Annales Societatis Geologorum Poloniae

A contribution to the study of Borysław sandstone

Crude oil is that one of the component parts of an oil deposit that might have originated simultaneously with the one or the other bed, or that might have been pressed out of the mother series through the action of various factors at the time when the sediment compacted and solidified, or — finally — that might have been infused into the already solid rock at some later time. For the petroleum praxis it cannot be an indifferent matter how the problem of the history of the reservoir rocks has been solved, as well as that of the rocks over- and underlying such deposits, and the material to the history of the formation and the transformation of each series of rocks we find in the petrographic, chemical and facial peculiarities of those rocks. Now, some peculiarities of an oil deposit will depend on the structure (tectonics) of the field and a thorough knowledge of the local structure and stratigraphy will frequently permit to forecast quite correctly, while other peculiarities of the oil deposit might be the result of many factors cooperating, and the productivity of the field, that is the higher or lesser degree of its commercial productiveness, becomes but one of the episodes of its geological history. However, we have not yet sufficient material at our disposal that we might be able to specify in each particular case in censequence of what factors such episodes would of necessity succeed each other. In connection with the exploitation of oil fields there are not always all of the available methods of systematic investigation fully taken advantage of. Among such methods of practical importance belong: the statictical method (as applied to production) and the pétrographie method (as applied to the series of petroliferous formations). Each of such series is the result of a sequence of phenomena as regards time, and of the mutual influence of those phenomena in space (correlation of phenomena). In certain physical, chemical and biological conditions must certain phenomena resul constantly, while in conserquence of some of those primary conditions having undergone any changes, that or the other resulting phenomenon will become but barely possible, and — finally — with basal conditions being entirely different, the phenomenon will not any more take place at all. To define conditions at the recurrence of which there would always follow of necessity a compound phenomenon like an oil deposit, would constitute the problem of calculating averages of the most probable results out of the largest number of particular phenomena, it would, therefore, constitute a work in part statistical in relation to geological phenomena. Microscopic investigation of sedimentary rocks and of heavy minerals permits to distinguish primordial (detrital) minerals from authigenic minerals („neoformation“ of French authors), originated in the formation itself during its sedimentation in consequence of chemical and biological (syngenetic) processes, or in consequence of the process of diagenesis during the solidification of the sediments, or — finally — through the introduction of the material from the outside (epigenesis). Thus mineralogical investigation permits a deeper insight into the geologic history of the rock itself. However, petroleum praxis needs not only definitions of geological facts accounting for such or other phenomena in the crude oil deposit, but it requires also that some other phenomena could be foretold. Geological knowledge has madë a tremendous progress in the direction to define that series of formations to which in any particular petroliferous province the oil deposits would be subordinated. No mistakes as to the leading series are now possible any more, and any uncertainty may still prevail solely regarding a more or less satisfactory result of the well about to be drilled. However, a good many geological conditions on which depend: the productivity of the deposit, the permanency of productivity or its unexpectedly early .exhaustion, the differentiation of productivity in various parts of the deposit either in the direction of the strike or of the dip, the concentration of pay streaks in that or other portion of the series, vertical section etc., — all that remains known to us in a very unsufficient degree. The main cause of this is the absence of any systematic investigation of the oilbearing series itself in each particular field. For even though physical attributes of the given formations constitute, it is true, one of the chief conditions governing the existence of the oil reservoir as such, they nevertheless do not solve fully the problem of interrelations between sedimentation within the limits of the oil reservoir and the oil-bearing capacity of the latter. Having followed up for a long time the results of drilling operations on the fields of Borysław , Tus t anowi ce and Mraźnica, as well as the literature on the petrography of sedimentary rocks, it occurred to me that possibly by combining investigation of physical attributes of oil deposits with such of conditions in which their sedimentation took place, it might be possible to obtain dependable material that would cover even so practical a problem as the answer to the question whether we might— on the basis of well samples from a number of adjoining wells — foretell any lithological changes in a well approaching completion and, at the same time, also the productivity of the deposit? The main oil sand of the Borysław pool, the so-called Borysław sandstone, is composed of series of individual sandstone beds of varying thickness, and is interlaminated close to the top by thin laminae of black slates, and close to the bottom, but not in all places, by slates of greenish-gray color. With those alternations at its top and bottom respectively, the sandstone series passes successively in its vertical section: upward — into the overlying complex of Menilite slates, and downward — into the underlying series of Popiele state s1). A more distinct limit in the upper portion of the Borysław sandstone series constitutes the series of „Lower Cherts “ having strata of black slates and sandstone subordinated to it, and frequently also the bottom limit is distinctly marked by the first strata of sandy slates being darkgray or grayish-green in color. Numerous wells drillend on the San Sab'ba, Horodyszcze and Mraźnica leases have demonstrated that at the top of the Bory s ł a w sandstone, but below the lower chert series, there occurs almost always a series of sandstones, frequently quartzitic, and of brown slates, with sandstones predominating in the upper portion of this series, and the brown slates in the lower. In some cases (Standard II, Mraźnica IV and Mraźnica VI) the lower chert series, manifests itself solely by several thin interlaminations of chert among sandstones predominatingly quartzitic, and of black oil shale with interlaminations of slates, known under the name of „Jasperite slates“. The annexed table No. I presents log sections of a number of wells in which the respective thicknesses of the following series of formations have been ascertained rather accurately: — I) the lower chert series, — 2) the series underlying the cherts (quartzitic sandstones and brown slates) and — 3) the series of the Borysław sandstone. Variations in thickness in all three of those series are quite considerable: — for the first: from 7 to 40 m, — for the second: from 4—10 to 25, and even 36 m, — and for ther third: from 11 —14 to 36 m and more. In those cases where also the Borysław sandstone series has been entirely traversed, the summary thickness of those three series runs between 36 and 88 m, while in cases where there is no second series (as in Halina and JoffreI), the summary thickness of the series 1) and 3) amounts to barely 36 to 50 m. Likewise, when the normal chert series happens to be absent, the summary thickness of the series 2) and 3) attains only 36 to 50 m (Liwia II, Standard II, ZofjaI, Kinga II), In the well Nahujowice (Standard-Noebel) the more or less normal series of lower cherts was followed by the series of sandstones and brown slates, overlying directly the green Popiele states and thus taking here the place of the series both 2) and 3). There was no Bo r y s ł aw sandstone series in its typical development, and the strong flow of brine was tapped 1004—1005 m in sandstone interbedded in Menilites and later at 1101 m in the sand stone of the sub-chert series. A like evanescence of the Borysław sandstone was met in the wells Mraźnica III and VI. The complexa of Menilite slates (lower Oligocene) and of the Popiele beds (upper Eocene) display both an eminently slaty character, but in the Popiele beds the slates are rather sandy. The character of the three series enumerated is preeminently sandstonelike solely at the bottom, and it gradually passes throughout the series 2) and 1) into a slaty one. Generally, all three of those series are oil-bearing, but only the Bo rys ł aw sandstone horizon admits of commercial exploitation. In the Popiele slates series there are generally also sandstone strata oil-bearing in part at least, especially at dephts of 70 to 80 m beneath the bottom of the Borys ł aw sandstone, and in the Menilite slates complex, that is in their upper portion among the upper cherts, there are also strata of sandstone that are frequently oil or gas-bearing. To modifications of the upper Eocene in the Popiele facies in the Borysław-Skole area, attention has been directed long time since (Kropaczek, Tołwiński ) , and that facies may be regarded as the first indication of the coming local conditions of sedimentation that have led to the formation of the Bo ry sł aw sandstone. Distinct top and bottom limits of the cemplex composing the three series enumerated (1—2—3), variations of their total thickness that are less than the variations in thickness of the respective members, — permit us to define those three series as a lithogenetic unit, with which is plainly connected the oil-bearing character of the basin. That unit is the expression of a reduction of the depth of the depositional basin after the time when the Popiele complex had subsided, but before the new cumulation at the time when sedimentation of the Menilite slates took place. A comparison of the thicknesses of those two complexa (Menilites= 130 to 230 m. Popiele beds = about 100 to 150 m) with the thickness of the oil-bearing unit (36 to 88 m) — and especially if we take into consideration the quicker rate of accumulation of arenaceous sediments like the Bory sław sandstone, as compared with that at which argillaceous sediments accumulate — vindicates the deduction that the sedimentation period of the entire oil-bearing unit constituted but a short episode in the geological life of the basin. That period stood in connection with a temporary slackening of the rate at which the bottom (geosyncline) subsided, and also with the frequent variations of the shore lines, and of the directions of transporting currents and streams. Of any absolutely synchronous analogies to the sandstone series of Borysław we do not know so far; the Kliwa sandstones in the lower portion of the Menilite slates may — for instance those in the vicinity of Bitków — be a kindred and homotaxial, but not a synchronous phenomenon, which factor might prove to be of consequence when explanation of the oil-bearing qualities of the Borysław chertsandstone series is attempted. The local reduction in the thickness of the chert-sandstone complex (wells: Liwia, Halina and others), as well as the evanescence of a pronounced distinctness on the part of the sandstone series (well Nahujowice and probably also Mraźnica III and VI, and Robert-Fanto) prove that the sedimentation episode of the oil-bearing unit was limited in area. A reply to the questions: whether it could be foretold in which direction from the productive fields of to-day the real limits of the oil-bearing area might be looked for, — whether that episode was not also associated whith some permanent change in the sedimentary material and, therefore, with what facial conditions, — whether this chert-sandstone series had not undergone any specific transformations brought about by its component material or by its interdependence from complexa lying directly below or above it? — that reply may come forth solely from systematic study of the petrography of the series of interest to us, and this essay must be looked upon solely as the first attempt at such studies, as must be undertaken by all of our petroleum geologists, and material for which must in the first line be assembled by them methodically. In this work I utilized solely a portion of the material so scrupulously compiled by Mr. J. Zieliński , M. E. (well logs, cuttings etc.) and elaborated upon by Dr. St. Jaskólski. Our task lay solely in singling out, in so far that was practicable, the most easily distinguishable features of oil-and gasbearing rocks, and also such features that commonly cannot be observed by merely maroscopic investigation or through a binocular lens. A plain and simple definition of oil-bearing formations must receive a practical application that will be the more extensive, the more abundant material for comparisons we shall have not only from the formations of the oil-bearing series, but also from the entire well log. Practical application of scientific methods requires that they be simplified to an extent that would render possible their employment by our geologists in actual field work, and to that purpose out of any of those methods can be singled out component parts that can be eliminated without that the degree of accuracy peculiar to any method as such would be lessened. Criticism of the method adopted by Melcher vor determining porosity has led to the introduction in the United States of Russel ’s method2) which simplified considerably measurements Of the volume of samples both in piece, as well as in powder form. A tedious job still remained the maceration of samples of oil-bearing sandstones in the Soxhlet apparatus, however, controlling experiments demonstrated that maceration of samples could be replaced by their being roasted, and that this expedient was applicable not only to sandstones that are exclusively quartzitic. Likewise the mechanical part of the analysis was modified so as to distinguish not eight sizes of particles as is done by the Americans, but solely six sizes, however, in order to determine the percentage of carbonates, every sample was tested for loss on hydrochloric acid. Examination of samples in thin sections that would not include the hydrochloric acid test, and without that porosity of the rock were determined, will not give a clear insight into the character of the cement in the sandstone. In separating heavy minerals, special stress has been laid upon determining the total percentage of the chief minerals, especially of the pyrite (and black opaque), the silicates and sulphates. Of definite results we obtained possibly not so very many, and in part they were already known before then, for instance as regards certain types of the Borysław sandstone, — while other problems that came up in the course of our work — such as the predominating effect of sedimentation upon the characteristic features of the Borysław sandstone as against secondary factors, or the passiveness on the part of formations overrespectively underlying the Borysław sandstone toward any transformation of that series, et. — constitute rather material for further studies. Within the sedimentary unit comprising: the lower cherts, the sub-chert series and the Borys ł aw sandstone, there exists a permanent and close relation between the oil-bearing horizons on the one, and the oil shales, the cherts and the strata of calcareous slates respectively, on the other hand. Microscopic investigation of samples of the latter formation (taken from the wells Mraźnica IV and XII) demonstrated them to be oolitic formations in a limy argillaceous mass. On samples from the wells Drasch VII and Rena VIII, the oolitic structure could be observed even through a lens. In proportion as they contain less of chemical material and as the content of detrital material in them is larger, suęh calcareous slates pass into sandstones having a cement of chemical and organic origin. Identical strata known in well logs by the name of „Jasperite slates“ resp. „Jasperite limestones“ reappear, without showing however oolitic structure at all times, in the sub-chert series (Ludwik, Drasch VII, Mraźnica I) and also among the upper cherts of the Menilite series (Mraźnicaa IV and XII, Fig. 29). The large proportion of organic remains— foraminifera, bryozoa, lamellibranchiata— is quite normal for those calcareous formations, as well as for normal sandstones, and frequently also for the Bo ry sł aw sandstone series (21 cases out of 41). Remains of siliceous organisms were determined in the Borys ł aw sandstone from the well Fan to No. 58, and in slates interbedding the Borysław sandstone in the well Horodys zcze II. The most abundantly oil-bearing sandstones— like those from Fan to No. 58, Józef I, J off re II, Standard II, Jerzy IX and Horodyszcze II — do not contain any organic remnants at all; they are sandstones with detrital cement only, and without any traces of chemical cementation. The supposition suggests itself — supported by investigation of rocks in thin sections and by HCl-tests — that a permanent relation exists between the formation of calcareous cement and the quantity of calcareous organic remnants. The calcitic cement orirginated chiefly from organic remnants, while the chemical sediment in the shape of limy clay submitted to recrystallization to a much lesser degree (Sadler XII (7), Ludwi k (77), Ul 1 mann (81) and G a 1 a 11 i III (43) (Eocene). Three samples form the well Fan to No. 58 — taken from the top portion of the Borys ł aw sandstone and within a distance of 4,1 meters — show in the lowest sample a distinct decline of porosity accompanied — in this layer only — by an increase in the quantity of calcitic cement at the expense of calcareous remnants; the two upper samples come from a sandstone having almost no cement, and only a minimum content of both calcitic and organic remnants. At the well Sadler XII, two samples from the sub-chert series, taken at a distance of 1,3 meters of each other, demonstrated the upper portion to be more calcitized. At the well J off re II, the same transition from 'calcitized Borysław sandstone to a sandstone without any cement has taken place within the distance of only one meter (Fig. 7, 8). Those facts demonstrate plainly that cementation with the aid of calcite must needs have taken place while the sediment solidified, and this by reason of a larger quantity of calcareous components in the various layers of the sediment. Such processes of sand cementation in consequence of large quantities of calcareous components may be observed to-day also along the sea shores. Silicification of the primarily calcitic cement, visible on the sample from the well Rai l i II (39), and also the secondary silicification in sandstones (Horodyszcze II (48, 68), Fan to 58 (51, 58), Dumb a VI (64), Drasch VII (23), Eglon II (30) — took place at the expense of the glauconite decomposing, which is demonstrated to best advantage on sandstones from the Eocene (Ralli II (39, 65). The first process might have been the result of the action of acid solutions, as has been observed by prof. Kreutz (1. c. pg. 45) in regard to Eocene sandstone; the second process of silicification, however, must have developed under the influence of rather alcaline solutions. Both processes must of necessity have evolved already after diagenesis proper had taken place, and they were caused by slow circulation of water in rocks that were already hardened. In the case of the two generations of calcite (B rugger 1 (3), Drasch VII (2), Ratoczyn I (81), the later generation is younger than the silicification, as is plainly seen from samples of Horodyszcze II (48), and it may come from a calcitization of feldspars or from a decomposition of chlorite (J offre II (49), F an to 58 (57). The mutual relation between those two processes and the porosity ratio of rocks is quite evident: each cementing process that leads to an augmentation of the cementing mass reduces at the same time the porosity:
Galatti III (49) — 3.94% Drasch VII .... (2) — 6.34% (37)
Galatti III (37) — 4.32% Rena VIII .... (41) — 7.53% (14)
Galatti III (14) — 7.21% Magdalena XV (47) — 6.65%
In some cases, and especially so with Eocene and Jamna sandstones, cementing substance in the shape of small quartz grains exerts an identical influence:
Ralli II (38) — 9.79%
Ralli II (40) — 8.87%
Ralli II (65) — 7.39%
The largest porosity show Bo ry sł aw sandstones having a fine detrital cement:
Horodyszcz II (68) — 14.53% and
Horodyszcz II 15.32%
J offre II (49) — 12.28%
less frequently those with silicaceous cement, as Fanto 58 (51) = 15.80%. Of well samples demonstrating secondary silicification in consequence of the opaque substance having developed in the cement, there are not many (Fanto 58 (51), EgIon II (30), Drasch VII (23)). In two cases (Dumba VI (64) and Nahujowice I (66)) such silicification shows in sandstones of the sub-chert series; in the wells Eglon II, Fan to 58 and Horodyszcze II we find it in the upper portion of the Borysław sandstone, while in the well Drasch VII it was found in the bottom portion of the Borysław sandstone. The preponderatingly calcitic and coarsely grained detrital character of the cement in the sandstone admits the supposition that there was no influence whatever exerted upon the silicification of the Borysław sandstone by the cherty series topping that formation. The character of the cement depends not on secondary processes, but chiefly on the type of sedimentation and the conditions under which the sediment solidified. The influence of sedimentation upon oil-bearing qualities of strata may be traced in the three following lithological sections: Horodyszcze I I . : — 1) After the sedimentation of fine detrital material that has become cemented through toothed grains of quartz getting compressed, there followed: — 2) the phase of sedimentation of still finer detrital material (.01 to .05 mm. in diam.) together with argillaceous material and partly organic silicaceous clay, and alternated rhythmically by exceedingly thin laminae of bituminous material. That phase was in turn followed by still another, that is: 3) the sedimentation of material exclusively detrital. Oil-bearing is the sediment of the first phase (porosity = 8.48%), while under the third phase (porosity = 14.53% to 15.32%) ranges sandstone preeminently gas-bearing. Joffre II: 1) Sedimentation of detrital material carrying fine detritus that plastered tightly over any larger grains of quartz, 2) the phase when coarser detrital material subsided, carrying fine grains of quartz and numerous calcareous organic remains. Oil-bearing is the sediment derived from the first phase (porosity = 10.89%), while that derived from the second (porosity = = 9.33%) is so to a lesser degree. Fan to No. 58: 1) First phase: sedimentation of coarse detrital material mixed, but not evenly, with calcareous organic remains (porosity = 10.36%), 2) Second phase; sedimentation of finer detrital material carrying silicaceous organic clay, which latter furnished the silicaceous cementing substance (porosity = 15.80%), 3) Third phase: sedimentation of detrital material with grains pressed intensively and toothed (porosity = 12.78%). Porosity is largest in the sediment formed during the second phase (15.80%) and that sediment gives the largest flow of oil. The series of lower cherts plays in relation to the subchert series and the Borysław sandstone constantly the role of a caprock, and that constancy would suggest that the properties of that caprock are the consequence of a diffusion of calcareous and siliceous solutions, as well as of a leaching of cement out of the oilbearing sandstones3), however, actual logs of our wells will not permit us to support such a hypothesis. Slaty elements in the subchert series (Ullmann [80 and 81]), among the lower cherts (Fanto 58 [58/b]) and in the Borysław sandstone (Horodyszcze II [59] and Standard II [69/b]) show plainly to be sediments of detrital material with streaks of bituminous clay (Fig. 4 a. 13), showing frequently traces of silicaceous organisms. Since with the progress of sedimentation there also increased the proportion of chemic mud, the adsorption of organic substance mus have taken place rather before the sediment solidified than after that. Prof. Kreutz observed in cherts unquestionable phenomena of secondary silicification, but he advanced the question, whether this were not organic sediment mixed with a large proportion of detrital material (1. c. pg. 48—49). Those exceptional instances of secondary silicification of sandstones in the sub-chert and in the Borysław series admit the assertion that there was no influence exercised by the chert series upon the cementation of strata lying underneath it. The recurrence of the (upper) chert series in the top portion of the Menilites, as well as the common occurrence of cherts in the Eocene, in Borysław as well as in other places4), permits us to establish their facial sedimentary character as independent of any secondary processes whatever. Menilite slates, slates of the sub-chert series and also the slates interlaminating the Borysław sandstone are distincly bituminous, while lime-clay formations, like the oólite formations referred to above, are not bituminous at all. It is a long time since in the petroleum geology attention has been directed to the fact, that by some types of organic sediment segregation of crude oil is favored to a larger extent than by others. Menilite slates contain large quantities of gipsum, sulphates of iron and chloride of sodium and, therefore, waters of that period could have properties of concentrated solutions that would initiate precipitation of colloid compounds, whereas the sandstones of the Borysław sandstone series are normal marginal detrital formations in which only among the heavy minerals any larger pyrite content could be noted [Camus IV (24), Rena VIII (41), Jerzy IX (21), Ratoczyn I (6, 8, 12), Horodyszcze II (53), Joffre II (49), Fanto 58 (54,57), Standard 11(5), Magdalena XV (13, 16, 47)], and also some sulphates: barite, anhydrite, celestine (Joffre II, Fanto 58,, Eglon II (27,30), Horodyszcze VIII (50, 53)). The pyrite may be of secondary origin as well, syngenetic, just as is the case with other components of the sediments. Among the various formations found in the geologic sections of the Carpathians are also red colored slates occurring in the Inoceramus and the lower Eocene, and carrying frequently rather weak oil horizons. If in spite of a synchronous quite extensive flooding of the sandstones, which would mean the movement of large volumina of underground water, the color of those formations has not changed to brown or green, that would disprove hypotheses on the migration of water in the transverse direction in general, or at least within the limits of the Eocene complex. Phenomena of adsorption as demonstrated by experiment5), may explain the different character of bitumina contained in slaty formations (hard modification of bitumina) and those contained in the sandstones alternating the slates (fluid crude oil). Nevertheless, adsorption through the agency of pure quartz sandstones and, following this, absorption of crude oil by the latter, could take place solely before the final consolidation of the sediment, but when the degree of porosity of the consolidating rock became defined in principle. The Menilite series is bituminous almost throughout its entire thickness, but bituminous are likewise interlaminations of slates and sandstones occurring among the lower chert and also among the subchert series. Oil-bearing sandstones found in the Popiele beds, in the lower Eocene and in the Cretaceous are interlaminated by sandy slates showing, however, no bituminous indications. Those , lithological conditions together with the arguments set forth above concerning the succession of sedimentary phases within the limits of the oil-bearing unit, permit us to declare ourselves for the syngenetic character of the crude oil in the strata that are its reservoir. There arises, however, the difficulty to explain the relation between the rather low average porosity of the Borysław sandstone and its in places rather high saturation. On the basis of measurements taken, the porosity of the Borysław sandstone varies between 2.2% (Magdalena) and 20.85% (Drasch VII), however, since none of those extreme figures is quite reliable, we would rather accept as limits: 5.36% (Ratoczyn) and 17.20% (Eglon II [4]). Compared with sandstones coming from various fields in the Uni ted States (7%—33%)6), both of our local limits are lower, and this proves conclusively that the Bo ry sł aw sandstone is more compact, variations being of the same order as usual in sandstones. Assuming: — 1) that on the San Sabba lease the wells BruggerIand Ralli II have stripped the area of 1 hectare, — 2) the thickness of the pay streak in the sandstone to be 10 meters (which figure is probably taken too high), and — 3) the porosity of the sandstone (Borysław sandstone) at 12.10%, — we may calculate the saturation index for that portion of the field as follows:

((100x100(2)x12,1))/100 = 12,100 m(3) = (12,100x1000)/159Bbls = 74,843

Tank-cars or in round figures= 1000 Tank-cars, that is per acre/foot of formation:

74,843/(2,4x32,8)Bbls

which equals the saturation rate of but mediocre fields in the United States.

Actually, however, the field exploited by the wells Brugger I and R alli II; produced:
3541+3489 = 7030 Tank-cars = 527,223 Bbls,

527,223/(2,4x32,8)Bbls=6700 BBls, which is about 7 times as much.

The wells surrounding that field on the south and west were either dry in the Bo r y s ł aw sandstone (G alatti III and Brunner V) or gave, like Drasch VII, a little oil from a party of the sandstone somewhat higher than at the wells Brugger I and R alli II, and for that reason it would be difficult to suppose that the production of those two wells had drained the field that extends for quite a distance in the direction of the dip. It might be inferred that these wells had stripped oil from the entire thickness of the Borys ł a w sandstone which averaged here approximately 30 meters, but that would give a volume of oil by about 2.3 times smaller than that actually recovered, and in that case, to calculate actual productivity, the porosity of the sandstone would need to be accepted at 27.8%. Borysł aw praxis admits the assumption that the actual productivity of the better fields will approximate 2000 tank-cars = = 150.000 bbls per 1 hectare, and that rate would correspond — with the thickness of the pay streak being 10 meters — to a porosity index of about 24%. Porosity ascertained upon small pieces of rock cannot by any means be also an index to the total volume of possible spaces that might occur throughout the entire bulk of any particular formation, in which small fissures will be the more numerous, the more complicated its tectonical structure will happen to be. Upon samples taken from the well Horodyszcze II it could be ascertained that the Borys ł aw sandstone is traversed by numerous fissures showing sometimes slickensides. Porosity ascertained on those samples was in fact higher: 14.53% and 15.32% both of which figures, however, are a long way off of 27%. That discrepancy between the actual yield of some wells (as in the case of Brugger I and Rai l i II) and the thickness of the Borysław sandstone we are unable to account for. The most probable would seem the inference that the wells drew their oil from the neighborhood, that is from beyond the boundaries of the supposed field. The actual productivity of the wells Brugger I and Rai l i II would — with porosity being 24% and the thickness of the pay streak 10 meters — need to be derived from an area of 3.5 hectares. An inflow from the bottom is precluded as is demonstrated by vertical sections of the entire complex of formations, nor can this discrepancy by explained by the theory of the entire complex having become ruptured by faults, and this because — as has been shown by Hempel — the area of possible oil blocks is limited to still a larger degree by the dimensions of the various sandstone blocks. If conditions under which sedimentation takes place decide upon the porosity of rocks and their possible primordial degree of saturation, then subsequent tectonical causes, like foldings aud faults, may create conditions that would favor increased saturation or the reverse may as well be the case. Far advanced fissirity of sandstones may be the cause of their additional saturation, for which porosity calculated from incidental samples cannot constitute a true index. Disturbances in the vicinity of faults or in zones of more important displacements in the sequence of strata may influence oilbearing qualities, however, that influence will not be identical in every particular field, and possibility to forecast such phenomena in each individual case is very much to be desired as it would be of great practical importance. For this reason positive certainty about the trend of faults becomes a very weighty geological argument. A number of such faults have been ascertained in the Borysław and Mraźni c a fields. Among them belong transverse faults like those of the well Kozak and of Tryskaj-Aldona, and more or less longitudinal faults like that of Józef. The influence of such faults upon the microstructure of rocks that constitute their walls may find expression in a cataclastic structure of those minerals and, with some of them, in the phenomenon of tWinned forms. Fissirity of rocks may also be the cause of an abnormal increase in the proportion of secondary pyrite. Those conditions have already received attention in the Uni ted States7). For indications of veins of calcite and quartz in samples, as well as for slickensides — as proofs of cataclase — are in our fields even the drillers on the look out, as they are well acquainted with the phenomenon of slickensides and with the significance of increased calcite and pyrite proportion. Now, upon the areas of the Mraźnica, Horodyszcze and San Sabba leases those phenomena manifest themselves distinctly in the proximity of the so-called overthrust plane and also in places within the overthrust itself, that is between the individual scales composing the former, but there those phenomena cannot constitute any important index as to the degree of porosity of the lower chert series, the subchert series, the Borys ł aw sandstone or the Eocene, and so, even though these phenomena are difficult to be perceived among those latter farmations, they nevertheless require, for reasons indicated above, full attention on the part of our geologists. All samples taken in the well Galatti III from the Eocene show a considerable proportion of pyrite and calcite veins and also twinning of the larger calcite grains in the lower Eocene. Galcite from two generations and accretion of pyrite were noted in samples of the Borys ł aw sandstone taken from the well Ratoczyn I, and twinned crystals of calcite in the Bo r y s ław sandstone were observed in samples from the wells: Horodyszcze II, Mela and Mraźnica II (Fig. 11); veins of calcite and quartz with fluid bitumen were noted in the sub-chert sandstone from te well Mraźni ca I. We have still little material at our disposal, but it can be observed nevertheless that even those rather loose indications stand in accord with the trend of deformation zones in the proximity of the faults referred to above and also » with the nature of the displacement in the proximity of the well Galatti III observed a long time past. In the latter case, and also in the proximity of Ratoczyn, the disturbance had an influence decidedly detrimental to oil-bearing qualities. Adsorptive qualities, capillarity and vertical pressure may be actors especially active during the consolidation of sediments. We have no basis on which to define the time in the course of which the processes of consolidation continued, and during which the processes of exchange of liquids and of the separation from each other of hard and of fluid hydrocarbons might have taken place. The consolidation period of sediments like muds and sands is over-long rather than the reverse. On the basis of known sections of diluvial formations filling deep river valleys (e. g. mining of auriferous placers) we know that consolidation of sediments, unless they are rich in calcareous and ferruginous components, requires geologic time. Tertiary oil-bearing series of California, Roumania, the Caucasus and other territories, still remain — notwithstanding their in places violent tectonical disturbances, so far only muds and sands. In consolidated rock, the main factor in any further accumulation of any such composites as oil and other chemic compounds may only be the movement of water, the direction and intensity of which will depend upon the tectonical structure of the rocks, that is upon orogenetic causes. To what degree theoretical studies on the processes of oil accumulation8) might be applied to actual deposits remains still an unanswered question. However, it may be accepted with some degree of probability that a loosening up of rocks in consequence of tectonical causes (fissility and fracturing) creates new void spaces within a certain portion of the deposit that had already become saturated before, and under the hydrodynamic pressure of the water confined in the oil-bearing stratum a portion of oil moves slowly from the flooded parts to the oil zone that has attained an increased capacity for saturation. But also the exact reverse may occur when the loosening of the rock structure leads to an emulsion of water and oil in the primarily oil-bearing party, and it is unfortunate that we know of no indicative phenomena from which the one or the other case might be inferred. It is quite possible that direct proximity of the fault to the primarily oil-bearing party may react unfavorably rather than otherwise. The oil-bearing quality of the unit differentiated by us that sedimentary episode — is not in the least an exceptional phenomenon, at least in the qualitative sense if not in the quantitative one. In the upper cherts, oil-bearing sandstones are in many cases known to exist, let us cite the oil horizons in the wells: M raźni ca IV at 1433 — 1439 m and Robert /Fanto at 1542 m; also in the well Mraźnica III the upper cherts commenced at 1384 m, and at 1410 m oil-bearing sandstone was met among the Menilite shales. The relation of those weak oil horizons to the substantial thickness of the bituminous Menilite shales series constitutes the best argument against the theory that bituminous shales are the maternal formation of oil-bearing horizons. The fields of Borysław, Tustanowic e and Mraźnica are that place where since the second half of the Eocene epoch there commenced to arise permanently conditions of sedimentation favorable to accumulation of bituminous matter in the fluid phase. Their greatest tension those conditions attained during the short period between the Eocene and the Oligocene epochs, however, it must be inferred that the period of solidification and compacting of the lower cherts, the subchert and the Borys ł aw sandstone series has been correspondingly lengthened, so that the processes of accumulation of hydrocarbons could attain their climax. This permanency compels us to seek its cause in favorable conditions that existed on the one hand in the sedimentary reservoir itself, and on the other hand in the terrane adjoining the former. The source of organic matter may be life in the coastal region of the sea, as well as that of the coastal region of the land. It has been established more than once that the seas in the Eocene and the Oligocene epochs were not dead by any means. Of life on land we have fewer proofs. Black and brown coloring of shales in the Menilite series, and frequently also in the Popiel e series, may be explained by bacteriar processes upon animal and vegetable matter. Traces of carbonization in the rocks of Carpathian cross-sections were not yet made the subject of detailed investigations. We know that for the sandstone of the Krosno formation characteristic is the large quantity of pulverized carbonized matter in them, while in other formations are vegetable remains — outside of fucoids — on the whole rather scarce, and only in places they happen to be not less abundant9). On well samples from Borysław may be ascertained that in Dobrotower Beds carbonized vegetable remains may be encountered in various horizons. In oilbearing series no vegetable remains could be discerned and, if the view point of Haseman and Rae is accepted, vegetable remains should not be even expected in those series. In Eocene and Inoceramus formations, carbonized vegetable remnants were found in many samples from a number of wells. Loose data on the occurrence of vegetable remains in the Carpathian sections do not entitle us yet to any conclusions on the genesis of oil, however, it might be well to point out that R. Zuber’s views on the part played by humous substances (ulmohumic acids) in the formation of bituminous sediments (1. c. pg. 329—340) are very closely approached by today’s views on that matter taken by American geologists, so e. g. Rae. Conditions permitting accumulation of bituminous material are solely the result of other orogenetic causes which decide the fact that at one portion of the coast such a process will take place, but will not do so at another, and this quite aside from the factor that the general rhythmus of the sedimentation is a regional phenomenon10). Upon the general background of that rhythm, the sedimentation of the B o r y s ł a w sandstone and of the sub-chert series is an exceptional phenomenon and probably dependent upon causes of very local a character. Today we are not yet in position to define those local causes precisely, and we may solely cite the hypothesis advanced by prof. Nowak11), that in its as yet unchanged position the flysch sediment blanket must have spread in a direction transverse to the trend of the Carpathians over the zones of primordial Carpathian area that later, in the period of Menilite shales sedimentation, may have already been entirely submerged. The local character of the Borysław sandstone might be derived from one of such zones. The question might be asked: whether in our flysch there could be found distinct indications disclosing also in other places of the present expanse of that blanket a favorable primordial Carpathian structure and also local sedimentation dependent there from and reduplicating Borysław conditions? — The only feature that would indicate any possibility of a subsequent sedimentation of the Borysław sandstone is the formation at the bottom of the Menilite shales series of an upper Eocene formation in the facies named Popiele; to which attention has already been called by N ow ak12). The Menilite shales — and the cherts among them — are pelitic sediments carrying a large admixture of muds of organic and chemic origin. Tey are, therefore, sediments accumulating very slowly and having in their primary state a considerable porosity. Until the time when the Do b r o t owe r Beds settled to considerable depth, the Menilite series could remain in a state favoring the segregation of various components, however, the presence of dry sandstone in the midst of this series does not constitute an argument in favor of a broad transverse migration of bitumina. The lithological uniformity over large areas of the Menilite and chert series that is independent of the multiform character of the formations lying at their bottom, will not permit to expect finding in those series any reliable indications as to what may be looked for underneath them. The oil-bearing sandstones of the wells Zofja I, J off re II and Standard II have at their top a chert series that is but imperfectly developed. Similarly, the barren Borysław sandstone of the well King a II showed at its top Menilites with only traces of cherts among them. The sedimentation phase in which the Borys ł aw sandstone settled in the type most favorable to the accumulation of crude oil (considerable thickness and large porosity) was the consequence of orogenic, erosive and sedimentary causes of which we do not know any particulars. As to whether there are any variations in the lithological features of Popiele Beds that underlie produc tive and barren sandstones respectively? — we have as yet no reply to that question, but possibly, if such variations existed, they could be taken advantage of in prospecting work over such areas where outcrops disclose upper Eocene formations and Popiele Beds. Study of well samples leads to the conclusion that transformation of rocks after they had solidified was less material than at the time when consolidation took place (diagenesis). Sub-terrain conditions of that entire section of the Carpathians were not favorable to broad and deeply going secondary transformation of those rocks, and farther reaching transformations took place rather close to the earth surface in proportions as, in consequence of erosion progressing, those rocks became exposed to influences that originated at the earth’s surface. The high vertical pressure, to which deep strata in our sections are exposed, could not exert any appreciable influence upon the transformation of rocks. The porosity of Jamna sandstone from the well Ralli i II at 1800 m was found to be: 8.87% and it hardly differs from the porosity of the Eocene sandstone from the same well (at 1687 m = — 7.39%), but is considerably in excess of the porosity of Eocene sandstone from the neighboring well Galatti III (at 1577.6 m = 3.94% and at 1554.8 m = 4.32%). Those differences are due solely to the primary cement in those sandstones. For comparisons sake was investigated also Jam n a sandstone from the well known outcrop in the proximity of the Limanowa Company ’s Main Office: that rock, having a much larger proportion of calcareous cement, shows a porosity of only 3.47%. Eocene sandstone from an outcrop close to the well Silva Plana XVII—composed of small quartz grains (0.2 mm) and of quartz detritus (size = 0.03 mm), with isotropic silica from the decomposition of chlorite — has shown a porosity of 10’20%- By its microstructure this sandstone comes very close to lower Eocene sandstone from the well Ralli II (from 1422.1 m and 1423.4 m and showing a porosity of 9.79°/0 and 12.17% respectively). Secondary processes connected with the decomposition of silicates contained in sandstones and, in consequence, with the appearance of the opaque siliceous substance, are of comparatively little influence upon changes in the primary structure of rocks. Eocene sandstones (Ciężkowice) coming from the oil-field Lipa in Lipinki (Western Małopolska) from depths of 284 m and 293.5 m respectively, show according to repeated tests executed by Mr. Nieniewski 1) a porosity of 23.87% and 24.62% resp. IV. Conclusions. I. Analyses: mechanical and microscopic — permit to distinguish in the rocks that were investigated (tab. 2 and 3) the following components: A) Primary: 1) Allochthonous (detrital): Quartz, silicates among heavy minerals (with the exception of chlorite). 2) Authigenic: Calcareous oolites, calcareous muds, mud (argillaceous) from the transformation of the bottom of the reservoir, black and brown organic mud, calcareous and silicaceous remains of organisms, chlorite, anhydrite, barite, celestite. B) Secondary: 1) Diagenet ic: formed during the solidification of the sediment: calcite, siderite, chlorite, isotropic silica, pyrite. 2) Epigenet ic: in rock already consolidated: isotropic silica, calcite, pyrite, oxides of iron. In some cases (Drasch VII, Rena VIII, Magdalena XV) it could be observed that the epigenetic calcite was better developed in the top portions of the respective strata. The most distinct epigenetic precesses are: the silicification of calcite and the decomposition of silicates (chlorite). II. The Borysław Sadstone: 1) Type wi th detri tal cement: The type of the Borysław sandstone that has been found (Fig. 1, 2, 3, 5, 6, 8, 9, 10, 11, 14) to constitute the best reservoir for oil (Jerzy IX, Horodyszcze II, Standard II, Joffre II, Fanto 58, Mraźnica I, Mraźnica II) is characterized by: a) The absence of chemical cement. b) Heterogenous structure in consequence of small angula grains being interposed among larger rounded ones. Because of that structure it crumbles easily when drilled. 3) Paucity of sulphates among authigenic minerals. 4) In secondary minerals: varying quantities of pyrite. That quantity is larger in proportion as the stratum is richer in oil. Porosity: from 10.50% to 15.32%. 2) Type wi th calcareous and det r i tal cement, in part exclusively calcareous: this type (Fig. 16, 17, 18, 19, 20) consists of rock having a larger content of organic calcareous remains (Brugger I, Eglon II, CamusIV, G alatti III, Horodyszcze VIII, Mela, Magdalena XV, Niagara II) and that frequently are in a state of full decomposition. Those sandstones probably belong to rather poor parties adjoining others having a higher saturation, as in the wells Brugger I and Ni aga ra II. The content as such even of large quantities of calcareous organic remains — so long as those latter have not suffered decomposition during the consolidation of the sediment (as in the wells Camus IV, Joffre II, Mraźnica II) is of no moment for the saturation of sandstones with oil, and, therefore, loss on HC1, even though quite large, does not furnish any real index as to the character of the cement from which in turn depend the porosity and saturation. Porosity: 6.65%— 12.43%. 3) Type wi th calcareous cement : a third type of the Borys ł aw sandstone (Fig. 7, 21, 23, 24) (wells: Drasch VII, Rena VIII, Ratoczyn I) constitute rocks, in which calcification proceeded uniformly through the entire mass of rock, even though the final quantity of calcareous cement be not large. Calcite: frequently from two generations, sandstone: frequently dry. Porosity: 6.34%—8.53%* 4) Type wi th opaque cement ing substace: the fourth type of the Bo ry sł aw sandstone (Fig. 15 Fan to 58, fig. 12 Eglon II, fig. 22 Drasch VII) are rocks in which acts as cement an isotropic silica, generated chiefly at the expense of chlorites (glaukonite) decomposing. Porosity: 5.29%— 15.80%. Whether this or any other type of the Borysław sandstone will result, is decided in the first place by conditions of sedimen tation and the diagenesis (types 1 and 2) and, in a lesser degree, by secondary epigenetic causes (types 3 and 4). Out of 41 investigated samples of the Borys ł aw sandstone, the relative frequency of cement of the various types was found to be as follows:
Calcareous........................... 20/41 = 48.78%
Opaque ...............................5/41 = 12.20%
Quartz detrital . . . . . . 12/41 = 29.27%
Calcareous and detrital . . . 4/41= 9.75%
and among 12 samples of non-oilbearing sandstone there were with:
Detrital cement....................... 1/12 — 8.3%
Calcareous............................... 9/12 = 75.0 %
Opaque ...................................2/12 = 16.6%
of 29 samples of oil-bearing sandstone, held cement as follows:
Detrital................11/29 = 38.00%
Calcareous and detrital . . 4/29= 13.78%
Calcareous........................... 11/29 = 38.00%
Opaque ............................... 3/29 = 10.22%
III. The shape and size of sandstone grains disclose conditions in which the grains had been transported: larger grains have been rolled along the bottom and were imparted a rounded form even after having been transported for but a short distance; small grains, on the contrary, having been transported in suspension remained angular in spite of having travelled long distances. The Borysław sandstones are chiefly fine-grained and this proves — if not their having been transported for long distances — then at any rate that repeated sluicing of the material had taken place. Of 35 samples examined, 20 (57.2%) show angular grains, while 15 (42.8%) schow rounded grains intermingled with finer angular detritus. The sub-chert sandstones — a product of the next following sedimentation phase — have grains chiefly angular (fig. 13, 25, 26, 27, 28, while sandstones from the Popiel e Beds — that is originated in the phase just preceeding the sedimentation of the Borys ł aw sandstone — have grains chiefly rounded or mixed with angular ones (fig. 34). The lower Eocene and Jamna sandstones have grains smaller and more uniform in size (fig. 31, 32,,33, 35) than the Borys ł aw sandstone. IV. Propr t i on of heavy nonma g n e t i c minerals. From table 2 may be observed that the proportion of heavy nonmagnetic minerals, while vacillating in various samples within rather broad limits, is nevertheless within the vertical cross section subject to certain laws. Thus the average proportion was found to be:
In sandstones from the lower Eocene . (4 samples): 0.66%
In sandstones from the Popiele Beds (5 samples ): 0.74%
In the Borys ł aw sandstone................(36 samples ): 0.28%
In Sub-chert sandstone........................... (6 samples ): 0.71%
All rocks investigated are characterized by a small proportion of silicates as compared with that of pyrites and of products of decomposition in the shape of iron oxides (black isotropic minerals). Among silicates, in turn, strikes the paucity in species what would prove the common origin of the sediments in the section investigated. The low content in heavy minerals in the Borysław sandstone, which cannot be explained away as being incidental, bears evidence to the exceptionally pure composition of that sandstone: chiefly of quartz grains. Petrographic differences between the various geological horizons seem to be founded upon frequent variations in the conservatory conditions of detrital material and upon larger or smaller adjections of chemical sediment. V. Abundance of pyri te in rocks cannot constitute a favorable index for the oil-bearing qualities of the sandstone. The pyrite may be the result of epigenetic processes connected with the deformation of rocks and exerting an adverse influence upon their saturation with oil (Rena VIII, Ratoczyn I, Galatti III). Epigenetic pyrite (pyritization of chlorite, pyrite veins) may be distinguished by macro- and microscopic examination much quicker than by way of an analysis of heavy minerals. VI. Abundance of pyri te in veins and twinning of calcite crystals may serve as indices of zones of deformation. Any appraisal of the importance of such zones in regad to oil-bearing qualities may be attempted solely after the trend of faults has been established. VII. The l i thologi c features of oil-bearing Borysław sandstones and their geologic expanse demonstrate them to be facial modifications originated during sedimentation which latter, although short in time, was nevertheless very changeful. This is borne out by the differences in proportion between the Pop i e l e beds and the sub-chert series as such, and the oil-bearing sandstones contained in each of those formations. VIII. Trans f o rmat i on ph enome na in the Borysław sandstone are chiefly confined to the primary character of the latter (sedimentation), no interdependence of such transformations from over- and underlying complexa could be proven so far. IX. Within the limits of a given reservoir (i. e. the reach of the Borysław sandstone series jointly with that of the series directly overlying the former) it is possible to forecast changes of a tectonical rather than those of sedimentary nature. Changes resulting from the first of above causes may be forecast at larger distance than sedimentary changes. X. By comparing well logs of neighboring wells with simultaneous examination of well samples — chiefly under the microscope and by testing for porosity — it would be possible to motivate forecasts regarding the direction in which lenticular strata of oil-bearing sandstones spread. The lithological character of oil-bearing Borysław sandstones (their comparatively small porosity and considerable interior friction), and also the great depth at which they occur, will permit the reservoir pressure to be maintained for a long time. At every moment of the well’s life a certain relation must be maintained between the reservoir pressure and the back pressure, so that the largest possible summary productiveness could be attained at the smallest gas/oil ratio. In this country there are generally no measures taken to maintain backpressure and if nevertheless declines in production are not quite so striking as in some fields in the Uni ted States, it is due exclusively to natural conditions of the Borys ł aw reservoir. The following table gives the gas/oil ratio for some Borys ław wells at the end of June 1928 as compared with that for their initial production. The volume of crude oil is taken in kilogrammes instead of in barrels, so that the ratio is given in turn in cubic meters per 1 kilogramm of oil. This was done as the object was not to obtain figures to be compared with those obtained in the Uni ted States, but figures to be compared against each other.

Gas/Oi l Rat io (x cbm of gas per 1 kg of oil).
Well - Initial - Now
Brugger I - 0’17 - -
Camus IV - 0’13 - 0’07
Jerzy IX - 0’07 – 0’04
Konrad IV - - 0’10
Horodyszcze II - 1’7-2’9 – 0’72
Joffre I - 7’00 - -
Joffre II - - 0’52
Standard II - 0’10 – 0’28
Fanto 58 - - 0’27
Mraźnica I - 0’27 - -
Mraźnica II - 1’50 - 0’80
Mraźnica XII - - 0’37
Ullmann - - 0’50
Horodyszcze VIII – 0’36 – 0’24
Ludwik - - 1’30
Józef I - - 0’24
Zofja I - - 0’02
Stateland X - - 0’64
This table demonstrates that on the whole there is no great waste of gas in our wells, a situation that is due solely to natural conditions prevailing in the reservoir. Those very same conditions (great depth, small porosity, considerable interior friction) render however impossible the application in our fields of such producing methods as is the driving by dry or wet gas. Similarly also for the application of waterflooding to oil-bearing Borysław formations are the lithological features of the Borysław sandstone less suited than those in Pennsylvania where that method is applied successfully in the fields of Bradford to sandstones showing a porosity of 15.7 to 18.6%. Better success might have the application of this producing method to the fields of Western Małopolska, e. g. those in the proximity of Lipinki . We have as yet no answer to the question as to what proportion of the total underground resources is in the Borys ł aw fields actually recovered by means of drilled wells. Clogging with paraffine frequently cuts short exploitation long before the sand has become depleted, while on the other hand the case of the wells Brugger I and Ralli II demonstrates that a limited field may yield a volume of production quite out of proportion to the porosity and the thickness of the formation tapped. There were as yet no measurements taken systematically of quantities of bitumi-' nous material contained in samples taken from wells approaching depletion. Only once such information has been given, when prof. Kreutz (I.e. pg. 47) gave the hydrocarbon content in sandstone from the well Niagara II as being 2.3%- From various sides are quite frequently advanced bold projects of a possible exploitation by mining of the northern portion of the Borysław field, where the oil-bearing horizon lies at the least depth, that is at less than 1000 meters. Leaving aside technical difficulties of such a project, it would be necessary to reflect first whether the depletion of the Borys ł aw sandstone had been carried only to such an unsufficient extent, and to what degree those sandstones would be capable to yield the oil that still remained in them. To answer those questions there is no other way, but to obtain from wells still drilling some core samples of Borysław sandstones and to subject them to necessary tests. Of the Borysław sandstones solely the first type constitutes a brittle rock that is the more brittle, the more oil has been withdrawn from it. That type is the chief reservoir of the entire party that is saturated with oil and probably its depletion is more thorough than that of the other types, while its physical features are the most favorable for the application of drainage. The second and especially the third type are not adapted for drainage, and it is just in sandstones of those two types that the largest quantities of residual oil may be expected. Sandstones of various types may pass into other types both in the horizontal, as well as in the vertical direction, and that irregularity in the sucession of various types of sandstones constitutes probably one of the main causes of the very ununiform results — mostly, however, negative — attained from shooting wells in the Borys ł aw fields1). Lithological features of Eocene sandstones, e. g. those on the fields of L i p i n k i in Western Małopolska, are more favorable to shooting, as well as to drainage by means of mining operations. Likewise account the multiform physical features of the Borysław sandstone also for the different attitudes of various individual wells toward swabbing: there are wells which require to be swabbed for a longer period of time before production can be induced to flow, and which after but a short interruption in swabbing regain the former rate of production only after protracted stimulation by swabbing. Among such wells belong e. g.: Jerzy IX, Sadler XII and in some measure also Camus IV. In the latter well the Borys ł aw sandstone has a calcareous cement, and similarly undesirable qualities may be displayed by sandstones having a very fine and closely pressed detrital cement as e. g. that one from the well Jerzy IX. The manner in which the best producing properties are scattered over the area of Tus t anowi ce leads — as follows from the work by Eng. Pfaff — that author to the conclusion that such fields are surrounded by portions comparatively poor on oil, similarly as islands are scattered in a river delta1). At the same time Pfaf f maintains that there exists no direct relation between the boundaries of such islands and the faults and fractures by which the entire field was presumably disrupted into blocks during the next following orogenic phase; he therefore assumes that upon the entire area of Tus t anowi ce there must have been formed a new set of fissures, through which oil has been transmitted to the various islands from unknown depths. On the basis of those premises Pfaff recommends that, before a new location is selected upon a known field, the logs of all wells situated within a radius of 500 meters were prepared and into each of them entered the volume of production obtained within each 10 meters of the log. By taking thus into account the various rates of production and their duration, he thinks, it would be possible to construct a probable system of fissures and to choose from that the most favorable location for the new well. Pfaff’s method rests on the one hand upon statistical material, but on the other hand it seeks support upon arbitrary assumptions, of a source of the oil at unknown depths and of its migration through fissures of which we do not known anything. In fact, that method does not furnish any real basis for petroleum practice and the only substantial result of the statistical analysis of the material on Tus t anowi ce was to define the productive islands or, in other words, to establish the irregular occurrence of more productive parties within the bulk of the B o rysław sandstone formation, but such localization of productive sands in the limits of a stratigraphically permanent oil horizon makes it necessary to proceed gropingly in the search for productive parties. Underground structure maps with the bottom of the lower cherts as their key horizon, the preparation of exact lithological sections in the limits of the lower chert and the subchert series will furnish material that may serve solely to forecast complications on the surface of the chert horizon and, therefore, also the oil horizon underlying the former. It is not only regarding the fields of Borysław, but also some others in the Uni ted States and Russia, that the facts available compel to the c