XP C 3 Press Bulletin Series Issue<1 Twice Q uartepIy STATE OF ILLINOIS - 0^ DEPARTMENT OF REGISTRATION AND EDUCATION , A. M. SHELTON. Director I C> DIVISION OF THE %*\£^ O < STATE GEOLOGICAL SUR VE Y ^>\ x a\^ \*> ' v M. M. LEIGHTON, Chief, Urbana C^>* ~£\ No 15 ILLINOIS PETROLEUM May 12, 1928 CONTENTS PAGE A study of the core of the Yanaway well No. 33 in the Siggins pool l Corrosion in the Eastern Illinois oil fields 9 A STUDY OF THE CORE OF THE YANAWAY WELL NO. 33 IN THE SIGGINS POOL By J. E. Lamar Introduction As the amount of oil in Illinois which can be produced economically by pumping decreases, the application of methods for increasing recovery becomes necessary in order to avert a premature abandonment of many pools and consequent loss of a large amount of recoverable oil. However, the intelligent application of improved recovery methods requires specific information concerning the oil sands, their detailed character, and their vertical and horizontal extent. Unfortunately such data are not generally obtainable from the available records, most of which are all too brief. Core drilling is therefore advisable in any attempt to determine if the amount of oil remaining in the sand is sufficient to warrant improved recovery methods and whether or not other conditions are right for the successful application of mining, flooding, or repressuring in any given pool. The pur- pose of this paper is to indicate the type of information which may be ob- tained from a single core and to show its bearing on deductions concerning some of the items mentioned above. The Petroleum Engineering Section of the Illinois State Geological Survey is prepared to make similar studies in other fields of the State, wherever satisfactory core samples are avail- able. Location The Yanaway well No. 33 is located in the SW. % SE. % sec. 1, T. 10 N., R. 10 E., in the north part of the Siggins pool in northeastern Cumberland Count}-. This pool appears to be one of the most promising in the State for the application of mining methods of oil recovery. For this reason detailed information on sand conditions and character should be ^ ILLINOIS PETROLEUM valuable in deciding how mining can be best applied. Though the Yanaway No. 33 is technically an edge well, the data from it are thought to be not unlike those of the rest of the pool in the major features. Method of Coking and Sampling. The core of the sand of the Yanaway well was obtained with a core bit for cable tools furnished by the Keystone Driller Company of Joplin. Missouri. The Ohio Oil Company arranged with the Illinois Geological Survey for collecting and studying samples of core from practically every foot of the sand. The samples of core thought to be oil sand were removed from the core barrel, rinsed rapidly in water to remove the mud usually coating them, wrapped in wax paper and sealed by immersing in melted paraffin. Other samples were similarly wrapped but not in all instances immediately after being taken from the core barrel. Laboratory' studies of the core were made along the four following lines: (1) description of core samples, (2) oil content, (3) porosity, and (4) texture. This work was largely done by C. R. Clark. Studies of the Core description of samples The samples of core were examined under the microscope and iden- tified as to kind and character of rock. The log of the sand is given below and is shown graphically in figure 1. Log of Yanaway well No. 33, Ohio Oil Company Shale, plastic, light gray-green Sandstone, gray, clayey, interbedded with gray siltstone and some shale; basal 3 feet limy Sandstone, medium-grained, buff -gray. . Shale, gray, bluish-gray and brown, carbonaceous, broken by siltstone; splits into thin flakes Coal Shale, gray or greenish-gray; soft at top, hard at bottom; mostly sandy... Sandstone, light gray, fine- to medium- grained Shale, dark gray, splits into thin flakes; moderately hard Coal Shale, plastic, gray, moderately hard.. Coal Thickness From To Feet. Feet Feet 400% 13% 400 % 414 14 414 428 44 428 472 1 472 473 17 473 490 10 490 500 4 500 504 1 504 505 1 505 506 2 506 508 ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00005 1304 A STUD'S OF THE CORE OF VAN AWAY WELL NO. ■'<'■'> 3 Shale and siltstone interbedded, gray, bluish-gray and greenish-gray; soft in upper part; hard, sandy, locally limy in basal IS feet 41 508 549 Coal 2 549 551 Shale, gray, greenish-gray and bluish- gray, locally sandy or limy; basal portion contains plant fossils 15 551 566 Coal 8 566 574 Shale, gray, hard, sandy to very sandy; contains plant fossils 7 574 581 Sandstone, gray, dense, hard 5 581 586 Shale and siltstone interbedded, gray or bluish-gray; locally sandy, coaly or limy 8 586 594 Siltstone, bluish-gray, hard, clayey; splits into thin flakes 13 594 607 Shale, bluish-gray, gritty 3 607 610 Siltstone, light gray, clayey, middle foot limy 3 610 613 Shale, bluish-gray, hard 5 613 618 The term siltstone used in the above log is used to describe those sedi- ments composed dominantly of fine gritty particles, too fine to be called sand and too coarse to be called shale. Inasmuch as siltstones ordinarily con- tain a high percentage of clay their effect on oil accumulation and migration is similar to that of shale. OIL CONTENT OK PER CENT OF SATURATION The oil content was determined as the difference in weight of a sam- ple before and after the oil had been removed by means of a Soxhlet ex- tractor — an apparatus especially designed for removing oils from solids. The graphs of per cent saturation given in figure 1 are thought to be mis- leading for three reasons. ( 1 ) Despite the fact that the core barrel of the bit was supposed to have been on bottom at all times, the way in which the core was broken in the barrel suggested that it had been raised from the bot- tom of the hole frequently during drilling. This would permit the escape of oil from the core. (2) the rate of drilling with the core bit was compara- tively slow and there was therefore time for a considerable proportion of the oil included in the core to have escaped. Some biscuits of core bubbled gas and oil after removal from the core barrel and there is no reason to suppose this had not also been happening while the core was in the core barrel. (.'5) Some of the core was in complete or partial contact with the mixture of oil and water in the hole, which afforded opportunity for oil to penetrate cracks or fractures in the core The oil content of some of the shale samples is thought to be of this nature. 4 ILLINOIS PETROLEUM POROSITY The porosity was determined by extracting the oil from the sample of core and then measuring the volume of fluid which it displaced when satur- ated. This gave the volume of the sample with the pores filled. The sample was then crushed and the volume of the resulting grains measured by deter- mining the amount of fluid they displaced. The porosity was calculated as follows : (Vol. original sample) — (Vol. sand grains) X 100 Per cent porosity = ■ (Vol. original sample) TEXTURE The texture of a number of selected samples was determined by making sieve analyses of them. The clay recorded in figure 1 is the material which had not settled through 15 inches of water in 10 minutes. The other grade sizes were determined on Tyler Standard Screen Scale sieves. Interpretation of Results of Tests general sand conditions significance of siltstones One of the important facts brought out by the study of the Yanaway core is the existence of siltstone as distinct individual beds and as "breaks" within the major sand-bodies. By reason of their intermediate character be- tween sandstone and shale, siltstones frequently grade laterally, in compara- tively short distances, into either sandstone or shale. It is possible therefore that the siltstones of the Yanaway No. 33 may be sandstone or shale in other wells of the Siggins pool. It is thought that this phenomenon probably ac- counts for the variation in the thickness of the producing sands in different parts of the field and may also indicate why as many as six oil sands are reported in some wells. OIL-SAND HOIUZONS The log given in figure 1 and on preceding pages suggests that in the northern part of the Siggins pool there are five horizons where sands may be expected to occur, as follows : ( 1 ) the upper sand found from 400^2 to 428 feet; (2) the siltstone horizon from 447 to 450 feet; (3) the middle sand from 490 to 500 feet; (4) the siltstone zone from 515 to 531 feet; and (5) the lower sand and siltstone zone from 581 to 613 feet. Of these the second is thought to be of the least importance as a possible sand horizon. The frequent changes in the character of the formations in the lower 118 feet of the well indicate unstable conditions of deposition in the sea in which these sediments were laid down, and consequently lateral variations in the sand- stones and siltstones of the lower 118 feet of the Siggins sand will probably be found to be greater and more abrupt than in the upper 100 feet. A STUDY OF THE CORE OF YAN.VWAY WELL NO. 33 I m m m it it ?*. ILLINOIS PETROLEUM THICKNESS OF OIL SANDS It the thickness of the sandstones found in the core of the Yanaway No. 33 be used as criteria, the sand records available for many of the wells in the Siggins pool are misleading in that they show far too great a thickness of sand. It is obvious that not all the formations logged as sand were pro- ductive of oil, but the records fail to indicate how thick the sand bodies are and at what depth they were found. Sand records at hand show from 18 to 91 feet of upper sand, but it is doubtful if the 91-foot thickness recorded was actually all sand. More probably, the sediments logged as sand were the upper sandstone and a series of interbedded shales and sandstones lying be- low. In the case of the lS-foot sandstone it would appear that some of the upper part of the upper sand of the Yanaway No. 33 grades laterally into shale. SEDIMENTARY STRUCTURES IN THE SANDSTONES AND SILTSTONES Judging by the manner in which the core broke, the three sands are all thin-bedded, in layers from !<4 inch to 2 inches thick. The bedding planes are irregular and many of them have thin films of highly micaceous clay coat- ing them. Several pieces of core were cross-bedded. The siltstones are even more irregularly heckled than the sandstones and arc usually very thin- bedded, resembling shale. THE UPPER SAND INTRODUCTION Since the upper sandstone is the most important in the Siggins pool and is the sand on which improved recovery methods would most logically be applied, it is discussed in detail. The general lithologic characteristics ex- hibited by the upper sandstone are also present in the two lower sands. OCCURRENCE (IF OIL Examination of the core of the upper sand as it came from the core barrel showed that the oil in it was not uniformly distributed. This is further borne out by the per cent saturation of the core samples (fig. 1) which show, considering only the outstanding features, an irregular arrange- ment of the points of high and low saturation, although in general the lower portion is shown to have a higher saturation than the upper. Some pieces of core showed even more restricted localization of the oil than indicated above, for in many of them by far the greatest amount of oil was found in a thin streak of coarse and apparently very porous sandstone which varied from ]/% to }4 of an inch in thickness. The cementa- tion of this coarse sandstone was much less firm than that elsewhere, inas- much as the core commonly broke along the coarser bands. A STUDY OF T11K CORE OF YANAWAY WELL NO. :'>•"> 7 II vina: OF THE SAND The texture of parts of the three sandstones in the Yanaway No. 33 well are shown graphically in figure 1. In general it may he said that all the sandstones are fine-grained and that all have a high clay content, ex- cepting sample I). The clay is present as a rilling between the sand grains. Sample A is high in very hue sand as might be expected from its position immediately below a shale. The siltstone "breaks" of the upper sand are shown in graphs B and C, with their high per cent of clay and material passing a 150-mesh screen. Graphs D, E, F, and G indicate the texture of the main body of the upper sand. The middle sand, illustrated by Graph H, is the coarsest of any of the sands tested. The lower sand is very fine-grained, high in clay and ma- terial passing a 150-mesh sieve, and approaches a siltstone in composition as shown by Graph J. POROSITY' DISTRIBUTION The results of the porosity determinations on samples of the sand- stones and siltstones are shown in figure 1. The porosity determinations as a rule serve to distinguish between the siltstones and sandstones, the former being much less porous than the latter. The upper sand shows considerable variation in porosity, doubtless due to variations in the tex- ture of the sandstone. The middle and lower sands have comparatively uniform porosities. RELATION OF CLAY CONTENT TO POROSITY It has been previously suggested that the clay present in the sands of the Yanaway No. 33 well fills the spaces between the sand grains and there- by reduces the porosity of the sandstones. This statement is borne out by data shown in figure 1. Graphs of texture show a high clay content for samples B and C. The porosity is low. Samples I), E, and F show de- creasing porosity and increasing clay content. Sample H is. in a way, an exception. Both its clay content and porosity are comparatively high, but this is because it has so much medium-grained sand that the pores are larger and the amount of fine material present is insufficient to fill the pores as completely as it dues in the other samples. RECOVERABLE OIL Inasmuch as the Yanaway No. 33 is an edge well, the saturation of the sands is doubtless lower than that of the sand in the more productive portion of the Siggins pool. However, assuming an average saturation of only '■] per cent, which is probably a conservative estimate of the actual saturation of the upper sandstone in the Yanaway No. 33, and a 60 per cent recovery of the oil remaining, the production would still be over 2,100 barrels per acre for the upper sand. This figure is essentially an estimate. 5 ILLINOIS l'KTROLKUM yet it is significant of the larger recovery which may he anticipated for other parts of the pool. Summary and Bearing of Studies on Improved Recovery Methods The study of the core of Yanaway No. 33 alone, does not yield defi- nite data on the advisability of mining, flooding, or repressuring in the Sig- gins pool, but it nevertheless indicates certain factors which must be con- sidered before improved methods are applied. These factors are as fol- lows : (1) Three sands which contain oil are present in the northern part of the pool in which the Yanaway No. 33 is located. (2) Two siltstone horizons are present; these may be sandstone elsewhere in the Siggins pool. (3) The sands of the Siggins pool are probably lenticular and therefore a thorough study of sand records, supplemented by core drilling, should be made to outline in detail the major sand bodies. (4) Of the three sands present the upper is the thickest and probably contains the most oil. It is therefore the most logical sand body for the applica- tion of improved recovery methods. (5) The upper sandstone is fine-grained and lies in thin, irregular beds. There are shale and siltstone "breaks," particularly in the upper part of the sandstone. (6) The porosity of the sandstone portions of the upper sand varies from 8 to 23 per cent. (7) The average saturation of the sandstone beds of the upper sand is 2.2 per cent. This is thought to be too low because of a probable loss of oil from the core samples. (8) Assuming 60 per cent recovery of the oil now in the upper sand and 3 per cent saturation, there are about 2100 barrels of recoverable oil per acre. CORROSION IX THE EASTERN ILLINOIS OIL FIELDS By J. E. Lamar and C. R. Clark Introduction The general problem of corrosion is of such great industrial import- ance that the reports on various phases of the subject comprise a voluminous literature' Corrosion of the metallic equipment used in the business of producing oil and gas is a special phase of the corrosion problem, which, because of its economic importance to the petroleum industry, has been the subject of special studies.-' The work thus far reported has been either of a general nature or else has had particular application to problems other than those confronting the Illinois oil operators. Therefore, the Petroleum Engineering section of the Illinois Geological Survey undertook a series of held investigations in the eastern Illinois oil fields in order to determine the causes of oil-field corrosion more precisely, so that any remedies avail- able might be applied. The purpose of this report is to make the results of the investigation available to oil operators. General, systematic studies of the waters in the Illinois oil fields were begun by the Illinois Geological Survey in 1924. One of the problems con- sidered in this investigation was the possibility of determining the relative corrosiveness of oil-field waters by comparing analyses of the mineral mat- ter dissolved in them. Although these investigations are not yet completed, it has been concluded that the relative corrosiveness of waters cannot be determined on the basis of a chemical analysis. ' ; ' The new work undertaken by the Petroleum Engineering section con- sisted principally of a more extensive determination of two of the chemical properties of the oil-field waters : ( 1 ) the relative acidity, and ( 2 ) the hydro- gen sulfide content. Quantitative determination of these properties was undertaken in the eastern Illinois oil fields during the summer of 1927, and an attempt was made to correlate the results of these tests with the relative corrosiveness of the waters. ( )ne of the outstanding difficulties in the study of oil-field corrosion problems was the absence of any comparable data by which the rate of corrosion could be determined. Comparison of corrosion in wells in indi- vidual pools or districts was [airly satisfactory, for the judgment of field superintendents who were familiar with operating conditions over such areas could be relied upon to classify the waters in a general way. No quan- titative determinations of the rate of corrosion could be made, however, so the terms "corrosive', "slightly corrosive" and the like, as used in ibis 1 For a comprehensive bibliography on the general subject of corrosion, see Speller, 1-'. X.. Corrosion, pp. 565-577, McGraw-Hill Book Co., New York, 1925. -.Mills. U. Van A., Protection of oil field equipment from corrosion, U. S. Bureau of .Mints Hull, -i:',:;, 1925. 1 Moulton, Gail !•'.. Illinois State Geol. Survey, personal communication. 10 ILLINOIS PETKOLEUM report, are definitely significant only of the relative corrosiveness in the specific field under discussion. In comparing fields as units, the state- ments regarding corrosiveness are the concensus of opinion of a large number of oil men. Acknowledgments The writers wish to express their appreciation to the many members of the petroleum industry of Illinois for their assistance and advice in mat- ters pertaining to this investigation, and to the State Water Survey for their valuable cooperation in making the chemical analyses of the samples of oil-field waters. Gail F. Moulton's constructive criticism of the manu- script has also been valuable. Conclusions and Suggestions . From the subsequent detailed description of corrosion in the south- eastern Illinois oil fields it is evident that the oil-field brines are responsible for the corrosion of the oil field equipment. Although no chemical charac- teristics of the brines are clearly responsible for their corrosive action, in the majority of cases it appears that the action of hydrogen sulfide, both as a gas and in solution, is the most important single factor. Remedies for corrosion might be found in the use of materials which would resist the action of the waters. On account of the large amount of equipment required for each well, the number of alloys and metallic coat- ings which might be used is restricted by the necessity of low cost, and it is probable that not many alloys or coatings remain untried. The solution of the problem would therefore seem to lie along some other line. Corrosion caused by waters which may be shut out of the wells by use of casing is easily controlled. In such a well the use of fluid mud, cement, or oil, behind the casing to protect it from contact with water should extend the life of the casing beyond the life of production. In certain parts of Illinois oil field work of this type should be very profitable. There is little doubt that the water produced with the oil and which causes so much of the corrosion can be reduced in many places and en- tirely eliminated in a few of them. The amount of water produced has been observed to bear ^uch a close relation to the rate of corrosion that it seems apparent that even a reduction in the amount of water handled with the oil would retard the rate of corrosion. The mudding oft" of cor- rosive waters and cementing off of bottom waters in the Flat Rock pool, undertaken in 1918 by the State Geological Survey in cooperation with the operators, is a good example of the type of repair work which may be done to reduce corrosion over some parts of the eastern oil fields. The work in the Flat Rock pool, Crawford County, resulted in satisfactory repairs on ten wells.* The net result was that an average increase of six barrels 4 Tough, Fred B., Williston, Samuel H., and Savage, T. E., Experiments in water control in the Flat Rock pool, Crawford County; Illiirois State Geol. Survey Bull. 40, pp. 97-140, 1919. CORROSION IN" EASTERN ILLINOIS OIL FIELDS 11 per day per well was obtained at an average oust of -tlifil per well. It is difficult to measure the additional benefit from reduction in the amount ol salt water handled, and therefore reduced lifting costs, as well as slower rates of corrosion, but the increased yield of oil more than paid the cost of the work. Systematic petroleum engineering studies of other parts of the Illi- nois oil fields to determine the feasibility of similar repair work are justified by the results obtained in the work of 1918. Areas in which corrosion is very serious are particularly promising of financial gain from this sort of re- pair work because of the saving to be expected from fewer replacements of pumping" equipment. In anticipation of undertaking cooperation in well repair work the Pe- troleum Engineering section of the Illinois Geological Survey has con- ducted experimental laboratory studies on the setting of cements under various conditions, and on the preparation of fluid muds which will stay in suspension for long periods of time. The results of these investigations will be published in later reports. Requests for cooperation in the solu- tion of water, cementing, mudding. and other problems in the field of petroleum engineering will be cordially received. The remainder of the paper is devoted to a detailed discussion of the types of corrosion, the relation of the chemical composition of oil-field brines to corrosion, the importance of hydrogen sulfide in corrosion, sub- stances that accelerate corrosion, the effect of corrosion on different mater- ials used in oil well equipment and details of corrosion in the various oil fields of eastern Illinois. Types of Corrosion introduction There are two important types of corrosion which do serious damage to oil-field equipment: (1) soil corrosion, which affects equipment buried in the soil, and 12) corrosion by oil-field brines and associated gases. Still another type, atmospheric corrosion or rusting, is also present, but as it is much slower and is comparatively easy to control, it is not discussed here. SOIL CORROSION Soil corrosion has been ascribed to an "acid" condition of the soil, but it is doubtful if this is generally the cause. Only in swampy and peaty soil.- i> acid present in sufficiently large amounts to markedly increase the ordinary rate of soil corrosion. Many soils give an acid reaction if tested with an ordinary indicator like litmus, because the basic color of the litmus is adsorbed by the colloidal matter in the soil. Thus many soils have been classified as true acid soils when in reality they possess only "ap- parent acidity." 12 ILLINOIS PETROLEUM Corrosion which affects buried equipment is the result of an electro- chemical reaction between the metallic equipment and soil water containing dissolved salts, and gases. That water is essential is evidenced by the fact that equipment buried in soil containing little or no moisture is not subject to soil corrosion. Soil corrosion may be minimized by the application of various pro- tective paints or coatings, either asphaltic or galvanized. In order to be effective these coatings must be moisture-proof. Great care should be ex- ercised, therefore, to prevent cracking or chipping of the coating during handling and installing, for the protective seal must remain intact over the whole piece or much of its effectiveness will be lost. WATER AND GAS CORROSION Corrosion by oil-field brines and gases may affect any of the subsurface or surface equipment with which they come in contact — casing, tubing, sucker rods, lead lines, vacuum lines, condensers, and the like, all are sub- ject to corrosion in some places. Not only is metallic equipment eaten away but also locally there is deposited contemporaneously a scale, usually largely composed of iron salts and sulfur, which often fills lead lines and vacuum lines to such an extent that they must be replaced. Generally the worst corrosion is caused by bottom- or edge-waters. Other corrosive waters penetrated in drilling can be shut off by strings of casing which may be mudded or cemented. Water and gas corrosion are. like soil corrosion, electro-chemical in their action. The rate of corrosion is governed largely by three factors : (1) the chemical composition of the oil-field brine, (2) the presence or ab- sence of products of corrosion that may accelerate or retard corrosion, and (3) the character of the materials from which the oil-field equipment is made. These matters are considered in the above order in this report. Relation of Chemical Composition of Oil-Field Brines to Corrosion choice of wells for investigation Because of the impossibility of securing comparable data on the rate of corrosion, the selection of corrosive and noncorrosive waters for study was of necessity confined to groups of contrasting samples from individual pools. Waters from two different areas were chosen for study, the Parker Township pool in Clark County and the Bridgeport pool in Lawrence County. These areas were favorable for sampling because in both pools there are wells producing from the same sands and in close proximity to each other, some of which yield corrosive water and others noncorrosive water. The wells selected were known to be producing regularly and to be in good condition. By sampling in this way it was believed that the analyses of the corrosive and noncorrosive waters in each area could be CORROSION IN EASTERN ILLINOIS (III FIELDS 13 accurately compared to determine what relationship if any, the chemical composition of the waters might bear to corrosion. Three water samples were taken in the northern part of the Parker Township pool. Two were from wells in which corrosion is very severe, and one from a well in which corrosion is not troublesome. The water in this pool is produced with the oil from the YVestfield lime which is found at an average depth of about 1-50 feet. In Lawrence County samples were taken from two wells a few miles north of Bridgeport. One of these wells produces very corrosive water with the oil while the other well, only a short distance away, produces only mildly corrosive water. Both wells are producing from the Bridgeport sand at a depth of about 1.000 feet. VALUE OF CHEMICAL ANALYSES AS INDICES OF CORROSION The results of water analyses are given in Tables 1 and * HYDROGEN SULFIDE CONTENT The corrosive properties of oil-field waters are thought to be due in a large measure to the hydrogen sulfide and carbon dioxide content as dis- solved gases and to the presence or absence of catalysts. Therefore, in addi- tion to the samples taken for chemical analysis, field tests were made on water> from a large number of wells scattered throughout the various pools • Op. 'it., p. 27. 14 ILLINOIS PETROLEUM where corrosion is severe to determine the amount of hydrogen sulfide dis- solved in the water, and to determine the hydrogen ion concentration which measures the 'acidity of a liquid. All of these tests were made as soon as the sample was obtained from the well. Only those wells which had been pumping continuously for an hour or more were selected for testing. These precautions were necessary since the hydrogen sulfide content of water lowers rapidly by chemical decomposition and by escape of the gas into the atmosphere when the water is exposed to the air or becomes warmer. RESULTS OP TESTS 1 he investigation showed that the hydrogen sulfide content of water indicates its corrosive or noncorrosive qualities only in a very general wav. If little or no hydrogen sulfide is present in the water there is probably no corrosion trouble and some waters with relatively high hydrogen sulfide content are only mildly corrosive. Nearly all highly corrosive waters have a high hydrogen sulfide content hut there are a few highly corrosive waters which are also relatively low in hydrogen sulfide. All tests for hydrogen ion concentration indicate that the waters are only very slightly acid or alkaline and in no test was the water sufficiently acid or alkaline so that this property might be considered an important factor in causing corrosive reactions. Substances that Accelerate Corrosion The most active and common product that accelerates corrosion is iron sulfide. It is formed by the reaction of the hydrogen sulfide in oil-field waters with the iron or steel equipment in the wells. Iron sulfide is electro- negative with respect to iron, consequently with the electro-positive iron of the equipment it constitutes a minute galvanic battery, and in the presence of water it greatly stimulates corrosion. The following facts seem to in- dicate the importance of iron sulfide in respect to corrosion. Many strings of tubing and casing are found to be corroded deepest just above the collars, indicating accelerated corrosion at that point. This is thought to be due largely to the iron sulfide scale which has lodged upon the ledges of the collars, and to the susceptibility to corrosion of strained areas in the casing and collars formed during the threading of the collars and screwing together of the casing. In many wells the few lower joints of tubing or anchor tubing are found to corrode much faster than the remainder of the tubing string. In some wells this may be due to more complete immersion but in others it is clearly due to the accumulation of iron sulfide around the tubing. The rate of corrosion in many wells grows progressively more rapid with age, but cleaning out at frequent intervals reduces the corrosion rate. The mud and water removed during the cleaning is usually very dark due CORROSION IN EASTERN ILLINOIS Ol 15 g 'w "o qq ijciVvOht - Q,"? o >- >-> t. a sr c s co - CD co S£ c o -S s > 2, =S _-, CD ^ cd 2 "b 2 .£:« ^ cs *j oj J ■vb£ = _; to a cu CD — o ^ ! t, o , *j T3 u cs = «M — ' CD n» O OS" on 0) _ S " te ° cu >> cd o s- u fe a) c £ > o cd _ m-o CD — ■*-> bfi'(- to c- -^ 3 5 M - •§.£ to CD 3. C CS ? M cu -b . 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The average life of the bottom joints of the 6j4-inch casing is about two years. The places of maximum corrosion are the threaded joints and the areas just above the collars, although the whole string of casing is also quite badly pitted. It would seem that filling the space between the 6-inch casing and the wall of the well with a thick mud might materially reduce this corrosion. The lead lines and sucker rods are seriously corroded, especially where the former are buried in soil which has become impregnated with sulfur and various salts by oil and water refuse from receiving tanks. In sec. 10. Oblong Township, the J. W. Shire lease of the Mahutska Oil Company produces oil with practically no water from the Robinson sand. Corrosion gives very little trouble here, but occasionally lead lines require replacement. The C. B. Walker lease of the Ohio Oil Company in sec. 27, Martin Township, produces oil without water from the Robinson sand. There is no corrosion on this lease or in this vicinity, which shows that the salt water and not the oil causes corrosion in the oil fields. On the G. W. Jones lease of the Ohio Oil Company in sec. 35, Martin Township, the waters are quite corrosive. The wells were all originally drilled through the Robinson sand into water and consequently they must now be pumped straight time at the rate of 20 barrels of fluid per hour. The waters contain dissolved hydrogen sulfide. Corrosion of the 6^4-inch casing is moderately severe and is most active about midway of the well. 20 ILLINOIS PETROLEUM Ordinary steel lead lines last about three months for wells most subject to corrosion, but some of the lead-lined pipe has been in use for over two years. Steel tubing lasts about six months ; galvanized tubing about twice that long. Sucker rods are commonly replaced when the tubing is changed. Of interest in connection with corrosion in these wells is the fact that anchor tubing is eaten through at a more rapid rate than the tubing above the working barrel, probably because the water acts on it from the outside as well as the inside. BELLAIR POOL Corrosion is quite severe on the Susanne Smith lease of the Ohio Oil Company in sec. 11, Licking Township. Production is obtained from two sands, the upper is probably the Robinson sand and the lower is one of the sands of the Chester series. The water from the lower of the two sands is the more corrosive. A comparatively large amount of water is pumped with the oil. It is commonly necessary to replace steel lead lines, tubing, and sucker rods about every year. Many of the lead lines are of cast iron but even these, where corrosion is the most active, must be replaced within a period of two years. Most of the wells that produce from the lower sand in this vicinity are also troubled with corrosion. PARKER POOL Probably the most intense and destructive corrosion in the county occurs in the vicinity of the Parker lease in Honey Creek Township in what is com- monly called the Parker pool. A great deal of water, high in hydrogen sul- fide, is produced with the oil from the Robinson sand. Many of the wells are pumped straight time. Corrosion is particularly bad on sucker rods and the lower joints of tubing and casing. The action of corrosion upon casing- seems to be from the outside inward, and below the seat of the 8-inch casing the 634-inch pipe shows the effects of corrosion to a greater degree than elsewhere, particularly just above the collars. This corrosion would probably be greatly lessened by the introduction of a thick mud between the 6%-inch casing and the wall of the well. Cast-iron tubing is used in at least one well, and chain-steel sucker rods in nearly all wells. The iead lines are of cast iron. BIRDS POOL In the Birds pool, located in Lawrence and Crawford counties and pro- ducing from the Robinson sand, corrosion is not a serious factor. It is confined mostly to working parts such as the balls and seats, and working barrels. FLAT ROCK POOL The conditions in the Flat Rock pool in Honey Creek Township are very similar to those in the Parker pool, but the volume of water pumped from most of the wells is less than that pumped from the wells in Parker CORROSION IX EASTERN ILLINOIS OIL FIELDS 21 pool, consequently the- corrosion is slower. Hydrogen sulfide is present in relatively large amounts in the gas and water pumped with the oil. Produc- tion is from the Rohinson sand. LAWRENCE COUNTY The oil fields of Lawrence County have no serious corrosion problems except for an area north of Bridgeport, near Millerville. There are five major producing sands in this area of which the Bridgeport sand is the youngest and most shallow, and carries the corrosive water. In general where the largest volumes of water are pumped the hydrogen sulfide con- tent of the water is highest and corrosion is most active. CLARK COUNTY Oil well equipment in Clark County suffers more from corrosion than any other of the counties mentioned. The Siggins pool, northwest of Casey, is the only producing area in the county not seriously affected, and the condition here is probably due to the small amount of water pro- duced with the oil. In general, however, tubing, sucker rods, casing, and lead lines are all destroyed in a relatively short time. Corrosion is worst in the north part of the county. Various kinds of equipment such as cop- peroid tubing and casing, cast-iron tubing and lead lines, wrought-iron tubing, and lead-lined tubing have been tried in an attempt to increase the length of time between replacements, but only cast iron has been found to resist corrosion for any length of time. It has been used in tubing and lead lines. WESTFIELD POOL The Parker Township or Westfield pool probably produces with the oil the most corrosive water in the State. Many of the gas lines, lead lines, and vacuum lines in this pool become choked with a scale high in sulfur, and this necessitates replacing or cleaning the lines at rather fre- quent intervals. The gas from this pool has a higher hydrogen sulfide content than any other produced in Illinois, and for that reason very little of it is run through compression or absorption plants to extract gasoline. The corrosive waters are produced with the oil from the so called "Westfield" lime. Wells producing only from the "Trenton" are not troubled with corrosion. Water from the Niagaran is said to be very cor- rosive. CASEY TOWNS II II', JOHNSON TOWNSHIP, AND MARTINSVILLE POOLS Corrosive waters are also found in the Casey Township pool, the |ohn- son Township pool, and the .Martinsville pool. In Johnson and Casey townships the production comes mostly from one sand, the Casev sand, which yields considerable water with some dissolved hydrogen sulfide. 22 ILLINOIS PETROLEUM In the Martinsville pool production is principally from two sands, the Carper and the Niagaran. Nearly all of the wells produce from the two sands at the same time. For two years or more nearly all of the wells in this pool produced only from the Carper sand, and no trouble from cor- rosion was encountered in any of the wells until they had been deepened to the Niagaran. Soon after this it was noticed that tubing and rods re- quired replacement more often than before. Unfortunately, most of the water, and oil too, are produced from this formation ,so that plugging it off would both prevent rapid corrosion and take away the best part of the oil production. 1, (87432—1,500)