szcwmcmca OF THE MAGNEWM / cmmum RATE To STRUCTURE N THE RELATED STONY LAKE OIL MEL"), MICHIGAN OAS Thais Ear tho Dog!» 0% M. 5. MlCHfiGAN‘ STATE COLHGE Robm‘? Thamas Young. 1955 fi. w "111mm: Lllljflllj mm lflfllflflll , This is to certify that the thesis entitled Significance of the Magnesium/Calcium Ratio as Related to Structure in the Stony Lake 011 Field, Michigan presented bg Robert Thomas Young has been accepted towards fulfillment of the requirements for _l_19_3_o__ degree in M 437L462. 46% Major professor / Date Fe brua 22 0-169 REMOTE STORAGE PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE 2/l7 20:: Blue PORN S/DateDueForms_2017.mdd - 99.5 SIGNIFICANCE OF THE MAGNESIUM/CALCIUM RATIO AS RELATED TO STRUCTURE IN THE STONY LAKE OIL FIELD, MICHIGAN By ROBERT THOMAS YOUNG A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology and Geography 1955 ACKNOWLEDGMENTS The writer wishes to eXpress his sincere thanks to Dr. w. A. Kelly of the Department of Geology and Geography, Michigan State College, under Whose direction this investi- gation was undertaken. He is also greatly indebted to Mr. G. F. Fix of the Carter Oil Company and.Mr. R. Grant of the Michigan Geolog- ical Survey for assistance in obtaining the maps, samples, logs, and other material so essential to the accomplishment of this study. Grateful acknowledgment is due to Dr. B. T. Sandefur for his many suggestions and encouragement and to Dr. S. G. Bergquist whose editing and critical comments were very helpful. or: sign": or! .rziqevzaoea- rum: 1 «Weave: am: no ed: '10 EJT'E .‘Z -ao£oe-3 negidar’ ,aelqmza: (Egan drzemielfrj'r u a or: 4: another? .'I‘ .3: .0 .6 (1!! 03 has vj'rev 9191-: as SIGNIFICANCE OF THE MAGNESIUM/CALCIUM RATIO AS RELATED TO STRUCTURE IN THE STONY LAKE OIL FIELD, MICHIGAN Robert Thomas YOung ABSTRACT The occurrence of secondary dolomite or dolomitic lime-_ stone adjacent to zones of weakness normally found in solid rocks has long been known to geologists. The development of tension fractures along the apices of folds, and the exist- ence of other fractured zones related to structure, has also been observed. That dolomitization should occur along the zones of weakness related to structure is a natural conclu- sion. In order to test this hypothesis it was decided to analyze a series of samples from.a dolomitized limestone formation in an area where a definite structure is present. The Stony Lake Oil Field of Oceana County, Michigan, was selected as having the requisite qualities for such an investigation. Samples from.this field were analyzed for calcium.and.magnesium content by titrating the prepared samples with.versenate. This relatively new method gives. rapid and accurate results, either on a percentage basis iii aenii ofiiaclcb t; edtmuica rust blins n1 onus: {Ilarwon asumfl: to sneak Leveb SAT .esaiaitoep -Jslxe ed: bur ,abiol to eeoiqi eels tad .euuwavuia o? heisioq I add groin wear; ‘DLUOu-‘i this ~u£onoo Issuien 2 at amujovfisa oi beblnen 35% II ctcofisrqv. eaesewmii besiji “In; a now ,3neseqq ai cruianda estziieb H ,nsgiduifi ,anuoU fiasco lo I fit none tot aeliiianp ejizinw «oi oustisxs sees Elsi: HAL beasceua ed: uniana'r {T eevig border Wen (ZuV’flCISW steed easiaeoquu e we 1r-ss or in.the form of a ratio. Results of the analyses were ex- pressed in terms of magnesium/calcium.ratios. The ratios for various intervals were plotted on base maps of the field and contoured in the form of lithologic ratio maps. It was hoped that comparison of the ratio maps with the structural map of the field would show the existence of a definite relation- ship or pattern such as might be expected if dolomitization had occurred along zones of weakness develOped in the for- mation because of folding. This, however, was not the case and it was concluded that, in the Stony Lake Oil Field, there was no recognizable relationship between the structure and the degree of dolomitization in the Traverse limestone as reflected by the magnesium/calcium ratios. Future work with other formations in other areas may yet establish the exist- ence of such a relationship. iv TABLE OF CONTENTS INTRODUCTION ..................................... SELECTION OF AN AREA ............................. THE STORY LAKE OIL FIELD.......................... Stratigraphy ................................ Structure ................................... METHOD OF ANALYSIS ............................... Samples ..................................... Reagents and Solutions ...................... Titration ................................... Calculations ................................ Ratios ...................................... CONSIDERATION OF DATA ............................ RELATIONSHIP OF DOLOMITIZATION TO STRUCTURE ...... ORIGIN OF DOLOMITE IN THE STORY LAKE FIELD ....... CONCLUSIONS ...................................... BIBLIOGPi-APII-Y 0.0.0...0......OOOCOOOOOOOOOOOOOOOCOO Page 10 12 1U- 17 21 23 25 Ah hé M9 TABLES Table Page I. Well and 881711313 data ooeooooooooeooooooooo 2? II. Data from lithologic ratio maps .......... hl ILLUSTRATIONS Figure Page 1. Index map of Michigan showing location or area eoooeeoooeooooooo 51 2. Map of Stony Lake Oil Field .............. 52 3. Generalized stratigraphic section of the Traverse group in Stony Lake Field ... 53 A. Structure contour map of Stony Lake Field contoured on top of Traverse limestone ...... 5h 5. Mg/Ca ratio map of Traverse limestone ' 0' t0 '2' 01" '3' below top 000000000000... 55 6. Mg/Ca ratio map of Traverse limestone O' or -1' to -5' or -6' below tOp ........ 56 7. Mg/Ca ratio map of Traverse limestone 0' or -1' to ~10' or -ll' below top ...... 57 8. Mg/Ca.ratio map of Traverse limestone -5' or -6' to -lO' or -11' below top ..... 58 vi . COOCICQQIIQVOII‘OVOUO .CCUQOOQC‘ For ‘ vh» .UC'UOIOOI 0.0... I_;_ A ~ ‘~. IOIIOOCOUOOI ~ o I , , - I Lg \__',. I I 71.“; "',_i 1 “It? " 34C“ . . . 911'“ I Y , 8 v: ‘ :vtc-i‘ 7- ;.. ; .IE’IJ‘V. a: r; - .00... .00 .00! ‘ ' 5 suede?“ i] _ ' ‘ 3". r ~ ‘ r: " J\ .0000. ~’~‘ ' ‘ I or”) z;;:' . :7 ».p, 7- , '. ., 0.0- 4~ some rvrrii‘ :\ ‘ '3 , 4 ., ."r .. ". r10... .‘ ,_:_w- INTRODUCTION The occurrence of secondary dolomite or dolomitic lime- stone adjacent to zones of weakness has been.noted.by'many authors. Geikie (1882, p. 305) early recognized such occur- rences and attributed them to the action of circulating waters. Steidtman (1917, p. hh8) in his work on the origin of dolomites states that secondary dolomites can be recog- nized by their relation to faults, fissures, and other sec- ondary Openings. Hatch, Rastall, and Black (1928, p. 193) discussed this phenomenon further: In the most characteristic occurrences, the secondary dolomite is clearly related to the planes of weakness normally found in solid rocks, the commonest channels of dolomitization being fault planes, joints, and.minor fractures. In Michigan and elsewhere a considerable number of pe- troleum.fields produce from porous zones in apparently lo- cally dolomitized limestones. In a study of the develOpment of porosity through dolomitization, Landes (l9h6, pp. 305- 318) paid particular attention to his relationship of the dolomitized zones to fissures, faults, and fractures. Al- though.in two of the fields which he cited as examples (Adams and Deep River pools of Arenac County, Michigan) the dolomitized zones extended for several miles in straight narrow bands not coincident with structure, Landes felt that there might be more than an accidental relationship between the position of the dolomite body and the rock structure. In explaining the porosity that is confined to locally dolo- mitized zones in limestones he concluded that: .... local diastrophism has produced master fissures in the limestone containing section; that an artesian'cir- culation has been developed which has carried waters through deeper dolomite and up into the limestone; and that these waters have replaced some of the limestone by dolomite that is locally porous where there was an excess of solution over precipitation during the re- placement process. As a result of this study, Landes recommended that well sam- ples be analyzed for MgCO3 content and indicated that its presence in more than average quantities might well be the basis for lateral exploration in the hope of finding true dolomite. Jodry (l95h, pp. 38 and 39) expressed the belief that dolomitization occurs on the apices of folded structures, as well as along faults and fissures, as the result of the action of ascending waters. His study of dolomitized zones in the Rogers City formation in central Michigan tends to bear out this belief. Application of the versenate method for determining calcium and magnesium in the Rogers City formation, and mapping of the Mg/Ca ratios thus obtained, resulted in a lithologic ratio map of the area which coincides closely with a subsurface structural contour map of the for- mation. A certain paucity of control, however, is indicated by the fact that in the four townships which were studied only hh wells penetrated to the Rogers City formation. Even with the data available from A5 shallower wells Jodry (195R, p. h) stated that at least five separate structural inter- pretations were possible. . In order to determine more exactly the nature of a pos- sible relationship between the Mg/Ca ratio and structure in a dolomitized limestone formation, it was decided to apply the versenate method of determining calCium.and.magnesium, and subsequent mapping of the Mg/Ca ratios, to the study of an area with well controlled structure from which plenty of samples would be available. SELECTION OF AN AREA Any area selected to demonstrate the relationship be- tween subsurface structure and the degree of dolomitization as reflected by the Mg/Ca ratio must have the following attributes: (l)_a locally dolomitized limestone formation must be present, (2) a structure of considerable magnitude should be reflected in this formation, (3) an abundance of control should.be available for contouring the subsurface structure, and (h) good samples of the formation should be available, distributed as evenly as possible over the lateral and vertical extent of the structure. A preliminary investigation to determine which areas might best fulfill these requirements was restricted to the oil and gas fields of Michigan. It was felt that these would not only afford the best possibilities in regard to control and samples, but would also, should a definite relationship be established between lithologic ratio maps of the Mg/Ca ratios and structure or porosity in dolomitized formations, be the object of major application of such a relationship. 0f the dozen fields judged most suitable from the stand- point of formation, size, structure, and structural control few'met the test of sample availability. In several instances the samples had been destroyed. DeveIOpment of some fields by numerous petroleum.companies, large and small, made the possibility of obtaining samples questionable in several cases. Fortunately, excellent sample coverage of the Stony Lake Oil Field was available from the Carter Oil Company. While not necessarily the best choice from all points of view, this field was selected as having the best comp bination of necessary properties for the purposes of this study. THE STONY LAKE OIL FIELD Location and extent. The Stony Lake field is located two to three miles southeast of the village of Benona, Clay- banks Township (TlBN-Rl8W), Oceana County, Michigan (see Figure 1.). The producing area, confined to sections 9, lO, 11, 1h, 15, and 16, is well delineated and extends for about two miles northeast to southwest and one and a half miles northwest to southeast (see Figure 2.). The total drilled acreage is 1,5h0. History of development. The Stony Lake pool was dis- covered in December, l9h6 by the Carter Oil Company's #1 Martin Miller well, NE-Sw-Sw, section 11. Subsequent devel- Opment of the field followed a 20-acre diagonal spacing pattern. To date there have been 85 wells drilled in or immediately adjacent to the producing area. Of these, 78 were producers and, as of the end of 1953, 71 wells were still in production. All dry holes were drilled on fringe locations. The field is almost entirely the property of the Carter Oil Company. Production. During the first year of develOpment the Carter Oil Company established a voluntary production rate of 100 barrels of oil per well per day. The State of Michigan has since established a proration of 50 barrels of oil per well per day or 100 barrels of oil per hO-acre unit per day. According to the Michigan Geological Survey (1953), cumula- tive production to the end of 1953 amounted to 5,h02,697 barrels of oil of which 608,671 were produced during 1953. Production has been nearly the same for the last three years. Brine production during 1953 amounted to h,h56 barrels per day, almost all of which was handled by subsurface diSposal methods. To the end of 1953 the average recovery of oil per acre drilled was 3,508 barrels. Producing zones. All wells but one produce from the Traverse limestone of Devonian age. According to Carter geologists (195h, personal communication), two separate and distinct pay zones are encountered. The upper zone consists of thin, erratically developed streaks of porosity found in the first 0 to 10 feet of the Traverse limestone. The rock is characteristically a fairly denSe, brown to tan limestone exhibiting scattered pinpoint to vugular porosity. No defin- ite oil-water contact has been found and an effective water or gas drive is lacking. The lower producing zone is encount- ered 15 to 30 feet below the tOp of the Traverse limestone in a light gray, fossiliferous limestone exhibiting good vugular and primary coralline porosity. A definite oil-water contact is in evidence at an approximate subsea depth of -953 feet. Because of the uniform porosity development the lower producing zone is a good water-drive reservoir. About five-sixths of the wells produce from the lower zone, most of them flowing naturally. Stratigraphy. It is generally agreed that the Traverse group includes that series of beds extending upward from the base of the Bell shale to the base of the Antrim formation. 'Some disagreement, however, has arisen as to the inclusion of the gray shales and thin beds of argillaceous limestone near the base of the Antrim formation. Cohee (19h?) consid- ered these to be the basal strata of the overlying Antrim formation. Hake and Maebius (1938, p. NS?) excluded this zone from.the Traverse group and recognized it only as a transition phase between the Traverse group and the brown to black shales of the Antrim.formation. In western Michigan the zone consists of a series of gray shales with occasional limy beds resting on a characteristic limestone member of the Traverse group. Here it generally has been accepted by petroleum geologists as a member of that group and is refer- red to as the "Traverse formation". The underlying limestone, consisting of up to several hundred feet of limestone and dolomitic limestone, is commonly referred to as the Traverse limestone. These terms will be used in this study with the indicated connotations. Because of the distinct and easily recognized lithologic break between the Traverse limestone and the shales of the overlying "Traverse formation" the former is used as a contouring horizon by petroleum geol- ogists and others. The structural contour map of the Stony Lake pool (Figure h) is contoured on this horizon. Several attempts have been made to divide the Traverse group into separate lithologic units and to correlate these units, where possible, across the Michigan basin. In one of the most recent articles dealing with fine Traverse group Cohee (19h?) states that the upper beds of the Traverse limestone of western Michigan are probably Thunder Bay in age. Figure 8 of his chart shows the southeastern part of Oceana County to be underlain by the Thunder Bay limestone and the rest of the county (including the Stony Lake field) to be underlain by the Squaw Bay limestone of younger age. Henry (l9h9, p. 8) divided the upper several hundred feet of the Traverse limestone into five separate lithologic units on the basis of an examination of samples and electric logs from wells in the Pentwater field of Mason and Oceans Counties. Due to lateral and basinward changes in lithology no attempt was made to correlate these units with previously established divisions of the Traverse. Henry mentions (19h9, p. 2) that both the Pentwater and Stony Lake fields have been termed reef-like producing pools. Because of the location of the Pentwater field (about 18 miles north of Stony Lake field) his investigation is of Special interest. In the Stony Lake field the Traverse limestone (from the top downward) consists of 3 to 5 feet of brown, crystal- 10 line dolomite and dolomitic limestone with some pinpoint to vugular porosity; 5 to 15 feet of brown to tan, fairly dense limestone and dolomitic limestone with scattered pin- point to vugular porosity; and a zone of undetermined thick- ness, the upper part of which consists of light gray fossil- iferous and crystalline limestone with coralline and vugular porosity. Since few' samples extended more than 25 feet be- low the top of the Traverse limestone a more extensive de- scription from personal examination of the lithology is not available. For a generalized section of the Traverse group in the Stony Lake field see Figure 3. Structure. The general structural configuration of the IStony Lake pool, as contoured on the tOp of the Traverse limestone (Figure A), resembles a dome with nearly 100 feet of closure. Carter geologists (l95h, personal communication) believe that the structure is the result of crossfolding with the major axis trending in a northwest-southeast direc- tion and the minor axis in a northeast—southwest direction. If this is the case the structural alignment is in agreement with the general trends in western Michigan. The possibility of a reef structure has already been mentioned. As a check on the nature of the structure of the Stony Lake pool, a structural plat was constructed using the top of the "Traverse formation" as the contouring horizon. When compared with the structural plat contructed on the tOp of 11 the Traverse limestone, the contours of the two were found to be nearly concentric with a difference of about 70 feet in the depths of corresponding contour lines. No flattened effect or drape folding was evident in the upper horizon, in fact a slight steepening was indicated on the extreme east and west flanks of the structure (in sections 8 and 12). If the major relief of the structure was due to a reef for- mation it seems likely that the structure as reflected in the overlying shale section would be considerably flattened. Since this is not the case it is considered that the structure is primarily of a tectonic nature and probably due to cross- folding in agreement with the general structural trend in the area. This does not obviate the possibility that a reef structure is present in the lower producing zone of the Stony Lake pool. Such a structure may have been of low re- lief or graded laterally into normal limestone thus present- ing a nearly flat surface prior to the folding. Because the structure in the Traverse limestone is almost perfectly re- flected in the overlying Goldwater formation of Mississippian age, the age of folding is considered to be post-Mississip- pian . METHOD OF ANALYSIS Until recently the methods available for the analysis of calcium and magnesium in limestones and dolomites involv- ed either the time-consuming precipitation and separation of the two in solution, or staining of the sample with Lem, berg's solution, silver chromate, or potassium ferricyanide. The latter methods often required the preparation of polish- ed slabs or thin sections and, upon staining, careful and detailed examination was necessary to determine the amounts of calcite and dolomite present. In Helvetica Chimica Acta for 19h? and l9h8 Schwartz- enbach and co-workers of the University of Zurich reported the results of a series of investigations of the complex ions of the alkaline-earth and other metals with aminopoly- carboxylic acids, and suggested the use of ethylenediamine- tetraacetic acid (commonly called versene) as a titrant for the sum of calcium and.magnesium in water, using a dye, Erio- chrome black T (F-2hl), as an indicator. This usage is based on the fact that both versene and Fh2hl form slightly ion- ized compounds with calcium and magnesium. One of the salts formed by the neutralization of versene with sodium.hydrox- ide, disodium dihydrogen versenate, is used in preparing the titrating solution. As the titration progresses the 12 13 versenate first combines with the free calcium ions, then with the free magnesium ions, and finally, at the end point, extracts the magnesium from the soluble, wine-red dye com- pound formed by magnesium and F-2hl. At this point the color changes sharply from wine-red to clear blue. The versenate method for obtaining total calcium.and magnesium has been successfully applied to‘the analysis of limestone by J. J. Banewicz and C. T. Kenner (1952, p. 1186) who used this method in analyzing 500 feet of core from an oil well. They, however, combined the versenatrmethod with the calcium oxylate separation in order to obtain separate values for calcium and magnesium. In a later article Chang, Kurtz, and Bray (1952, p. léhO) of the University of Illinois elaborated upon the use of the versenate method for deter- mining total calcium and magnesium in limestones and supple- mented it by describing a simple method of titrating for calcium alone by using ammonium purpurate (murexide) as an indicator with the versenate. Results obtained with the versenate titration in analyzing standard.samples were in excellent agreement with results obtained by conventional procedures. Since the versenate method has not yet been described in any of the publications generally available to geologists, it is outlined here in some detail, with such modifications as have been found convenient by the author. The techniques described by Cheng, Kurtz, and Bray were used as a guide. 111» Of Special importance in the following procedures is the use of distilled water in the preparation of all aqueous solutions and in washing equipment. Samples Source. Carefully selected core chips or pieces of out- crop offer perhaps the best type of sample for analysis. Cable tool samples are usually satisfactory and unless the sample is very finely ground a representative portion can often be selected megaSCOpically. Samples obtained with rotary tools (except cores) are difficult to work with for the following reasons: (1) the necessary quantity of sample is not often available in the first shows, (2) it is diffi- cult to locate the sample correctly as to depth, and (3) separation of a suitable sample must often be made microscop- ically, at least from the earlier shows. If the stratigraphy, lithology, and drilling practices of an area are well known to the analyst foreign material in the samples is quite eas- ily determined, either from empirical data or from the apes- modic occurrence of such material in the section. Preparation. Samples must first be thoroughly washed and dried. Pieces of caving and other foreign material should be removed and a magnet passed through the sample to pick up any pieces of "junk" iron which may be present. If only a ratio of calcium and magnesium, instead of exact percent- 15 ages, is desired, cherts and other relatively inert mater- ials of a non-limy nature need not be separated from the sample. Crushing ofthe larger fragments will aid in rapid and complete digestion. Quantity. Samples of 1.00 gram were recommended by Banewicz and Kenner (1952, p. 1186) and Cheng, Kurtz, and Bray (1952, p. 16h0) as being of optimum size. Satisfactory results were obtained by the author with samples as small as 0.25 gram. Unless only small samples are available, how- ever, it is recommended that, for convenience in handling and calculating, 0.50 gram or 1.00 gram samples be used throughout any one series of analyses. Digestion. Weigh 1.00 gram of properly prepared sample into a 250-milli1iter beaker and add 10 milliliters of hy- drochloric acid (1 to 1)1 and 15 milliliters of water (dis- tilled). Evaporate to dryness, bake residue for a short time (10 to 30 minutes), and allow to cool. Take up residue by adding 3 milliliters of hydrochloric acid (1 to l) and 10 milliliters of water. Filter the solution and make up to 250 milliliters with water (a 250—milliliter volumetric flask is convenient for this purpose). 1Chang, Kurtz, and Bray (1952) recommended the use of perchloric acid for digesting samples. Because of the dan- gerous fumes evolved hydrochloric acid was substituted and proved to be satisfactory. 16 Laboratory Equipment The following equipment was utilized during the analyses: Balance and weights 5-gallon carboy with siphon (for distilled water) Mortar and pestle 50-millilitcr burette (graduated) 250-milliliter beakers (2)1 loo-milliliter beaker (1)l 200-milli1iter porcelain dish (1)1 50-milli1iter glass funnel (1)l 200-milli1iter volumetric flask 1-liter graduate 50-mi11iliter graduate 10-milliliter volumetric pipette 5-milliliter volumetric pipette Assorted tweezers, stirring rods, spatulas, etc. In addition to the above equipment it was found con- venient to have, besides the original large containers,- small drOpper bottles and a 0.10 gram.measuring Spoon from which to diapense the indicators ani other reagents during titration. A large Erlenmeyer flask equipped with a Spout of tubing was used to replenish the burette between titrations. 1If samples are run in batches the quantity of equip- ment indicated in parentheses will be required for each sample in the batch. 17 All standard solutions, reagents, and indicators were kept tightly stOppered when not in use. Small quantities of sol- utions remaining in diSpensing bottles after a series of determinations were thrown out and the supply replenished from the original containers. All pieces of equipment were washed in distilled water and the volumetric flasks and pi- pettes were rinsed after each usage. Reagents and Solutions Required for Calcium Determination Versenate solution. Place h.00 grams of disodium dihy- drogen ethylenediaminetetraacetate dihydrate1 in about 100 milliliters of distilled water and, when thoroughly dissolved, dilute to exactly 1 liter. Standardize this solution against - the standard calcium and standard magnesium solutions as ‘ described hereafter. Standard calcium solution. Dissolve 2.h95 grams of cal- cium carbonate2 in about 5 milliliters of hydrochloric acid (1 to l) and dilute to 1 liter with water. This solution contains 1.000 milligram of calcium per milliliter. 1Available from the Hach Chemical Company of Ames, Iowa N N as TitraVer . 2Standard calcium solutions were prepared with both re- agent grade calcium carbonate and Iceland Spar. Identical results were obtained when the versenate solution was stand- .ardized against the two . 18 Potassium hydroxide. Prepare a 20 percent aqueous sol- ution. This solution serves to adjust the pH value of the sample for titration. Calcium indicator powder. Thoroughly mix powdered potas- sium sulfate and murexide in a ratio of 99 to 1. This item may be obtained in prepared form as "CalVer" from the Bach Chemical Company. Several mixtures of potassium sulfate and murexide were tried and the quantity of indicator powder used in successive determinations of a single sample was varied. Results were essentially the same but it was found that the best colors and color changes were obtained using approximately 0.10 gram of the 99 to 1 mixture. .Required for Magnesium Determination Versenate solution. As previously described. Standard magnesium solution. Dissolve 3.h7 grams of reagent grade magnesium.carbonate or 1.66 grams of magnesium oxide in 5 milliliters of hydrochloric acid (1 to l) and dilute to 1 liter with distilled water. This solution con- tains l milligram of magnesium per milliliter.1 1Standardization of the versenate solution with the original standard.magnesium solutions prepared as above did not give results agreeable with those calculated from the molality of the versenate solution as found with the stand- ard calcium solution. A new standard magnesium solution was prepared using magnesium oxide obtained by heating reagent grade magnesium carbonate to a temperature of 1500 degrees centigrade for several hours in an electric oven. Excellent correlation was achieved with this solution. 19 Buffer solution. Dissolve 67.5 grams of ammonium chlor- ide and 5 grams of the magnesium.salt of versenate1 (obtain- able from.the Hach Chemical Company) in about 200 milliliters of water, add 570 milliliters of concentrated ammonium hy- droxide, and dilute to 1 liter with water. This solution serves to adjust the pH of the sample being titrated to a suitable value (about 10). Potassium cyanide. Prepare a 10 percent aqueous solution. The addition of this solution to the sample largely over- comes interference with the end point occasioned by the presence of iron, c0pper, cobalt, or nickel. F—2hl indicator. Dissolve 0.15 gram of Eriochrome black T (Fk2hl, available from the Hach Chemical Company) and 0.50 gram of sodium borate in 25 milliliters of methanol. In sol- ution this indicator was found to be stable for several weeks. Since the methanol evaporates readily, the container should be kept stOppered except when actually dispensing the indicator. Quantities Required The following quantities of material were necessary to prepare and.make a complete calcium and magnesium deter- The addition of the magnesium salt of versenate is necessitated by recent refinements in the versenate obtain- able (Hach, l95h, personal communication). 20 mination for one sample. The figures are based on the use of a 1.00 gram sample made up to 250 milliliters in solution, of which a 10 milliliter aliquot was tested. Distilled water 310 milliliters Hydrochloric acid (1 to l) 13 milliliters Filter paper (number 1) 1 each Versenate solution 7h milliliters1 Potassium hydroxide solution 1 milliliter Calcium indicator powder 0.10 gram Buffer solution 2 milliliters Potassium cyanide solution 0.10 milliliter F-Zhl indicator O.h0 milliliter These figures are given as a guide in estimating the quantities of the various materials which might be required for a series of analyses. Plenty of additional distilled water should be available for washing equipment and an extra 20 percent of all material should be allowed to cover standardizing, re-titrations, and similar items. Standardization of Versenate Solution With standard calcium solution. Take a 10 milliliter aliquot of the standard solution and proceed as described for the titration of calcium, using murexide as the indicator. Average quantity required for calcium and total calcium and magneSium.determinations per sample. Based on average for 20 samples. 21 With standard.magnesium.solution. Take a 10 milliliter aliquot of the standard solution and proceed as described for the titration of total calcium and magnesium, using F—2hl as the indicator. \ Titration For calcium. Pipette a 10 milliliter aliquot of the solution to be analyzed into a 200-milliliter porcelain dish, then add about 20 milliliters of water, 1 milliliter of potassium hydroxide solution, and approximately 0.10 ‘ gram of calcium.indicator powder. Stir, and titrate with the standardized versenate solution. The end point is reached when the color changes from.pink to violet. The sample should . be titrated immediately after the addition of the calcium indicator powder as the latter is not stable in solution. A series of determinations of the same sample was made immediately following the addition of the indicator powder and ten, twenty, and forty minutes later. Negative errors of up to 12 percent were noted in the delayed determinations. For total calcium and.magnesium. Pipette a 10 milliliter aliquot of the solution to be analyzed into a lOO-milliliter beaker, then add about 25 milliliters of water, 2 milliliters of buffer solution, several drOps of potassium cyanide sol- ution, and 8 drOps of F-2h1 indicator. Stir, and titrate with the standardized versenate solution. The end point is 22 reached when the color changes from.wine-red to clear blue. Care should be taken to add the reagents in the order indi- cated. If the indicator is added before the buffer solution or potassium cyanide solution, interference by iron is likely to be encountered. This will give a pink tinge to the blue color beyond the end point. A series of determinations of the same sample, made immediately after, and at ten, twenty, and forty minutes following, the addition of the indicator, gave identical results. For convenience and Speed in carry— ing out the determinations it is recommended that the titra- tion for calcium be made first. It is then possible to add swiftly at least the same amount of versenate solution to the sample when titrating for total calcium.and magnesium. Color Standards Since the colors involved in the titrations are not stable for more than a short time it is not possible to establish permanent comparative color standards. FUrther- more, the end point obtained with the calcium indicator powder (pink to violet) is not as sharp as that obtained with the F-2hl indicator (wine-red to blue). In order to check the end point obtained with the calcium.indicator, titrations of the standard calcium solution were made with both the calcium indicator and F-2hl. The sharp end point obtained with the latter was used as a reference 23 when titrating with the calcium.indicator and, with a little practice, it was possible to obtain excellent agreement be- tween the two end points. Calculations For Standardizing Versenate Solution With standard calcium solution. 25.2 milliliters of versenate solution were required to titrate, to the end point, 10 milliliters of the standard calcium solution. Since this solution contained 1.00 milligram of calcium per milliliter, 0.397 milligram of calcium.was titrated by each milliliter of versenate solution (10/25.2 = 0.397). With standard.magnesium.solution. hl.3 milliliters of versenate solution were required to titrate, to the end point, 10 milliliters of the standard magnesium solution. Since this solution contained 1.00 milligram of magnesium per milliliter, 0.2h2 milligram of magnesium.was titrated by each.milliliter of versenate solution. As a check the milli- grams of magnesium per milliliter of versenate solution were calculated from the results obtained with the standard cal- cium solution as follows: , - 1 Atomic weight of magnesium. _ 2%.32 8 0.607 Atomic weight of calClum- h0.08 0.607 X 0.39? - c.2t1 21L This calculated value agrees closely with that obtained using the standard magnesium solution. Since any impurities present in the magnesium compound used in preparing the standard solution would have the effect of raising the fig- ure, the calculated value (0.2hl, the lower of the two) was accepted as being most nearly correct. Calculations for successive batches. Eight separate batches of versenate solution were prepared and standard- ized with the standard calcium and magnesium solutions. The results were essentially the same with each batch and the original calculations were thus validated for the entire series of analyses. Calculations for Calcium and Magnesium Given: A - milligrams of calcium per milliliter of versenate solution. B - milliliters of versenate solution used in titration with murexide as indicator (for calcium). C = milligrams oftmignesium per milliliter of versenate solution. D = milliliters of versenate solution used in titration with F-2hl as indicator (for total calcium and magnesiwm. 25 Then the quantities of calcium and magnesium.present in the sample can be calculated as follows: A x B 031°ium ' (weight of sample titrated) TMnesium.‘ C X (D - B) ““5 (Weight of sample titrated) If a 1.00 gram sample is made up to a 250 milliliter solution and a 10 milliliter aliquot is taken for titration, the percentages of calcium and magnesium.can be calculated as follows: 7.7 .. r A X B = {.4 ¢ = C XJD " B) = _ Ratios Selection. On a molecular basis the ratio of calcium to magnesium varies from 1.000 in‘a normal dolomite (CaMg(COB)2) to infinity in a pure limestone (CaC03) while he magnesium/calcium ratio varies from 1.000 to zero. Since the results of much recent quantitative work have been expressed in terms of weight it was thought desirable to express the ratios used herein on that basis. The ratio of Calcium to magnesium thus will vary from 1.6hh (in a nor- mal dolomite) to infinity (in a pure limestone) and the 26 magnesium/calcium ratio will vary from 0.607 to zero. Ob- viously, the use of the magnesium/calcium.ratio on either basis will give results within well defined limits which can easily be applied to the construction of charts, graphs, and.maps regardless of the relative quantities of calcium and magnesium present. Calculations. The ratio of magnesium to calcium can be calculated from the relative percentages of each as previous- ly determined. A more direct method of calculating the ratio is as follows: ”@125: Cx (D- B) x 2.5_ C(D- B) % Ca A X B X 2.5 - AB Since C and A bear a constant relationship to each other as determined by the respective atomic weights of magnesiwn and calcium, the ratio can be even more simply expressed. Thus : ME - D - B a 0.607 x B To obtain the magnesium/calcium ratio with this formula neither the weight of the sample nor the strength.of the versenate solution is required. The formula thus lends itself readily to use in mass analyses or field work where the ratio alone is sufficient. 27 TABLE I WELL AND SAMPLE DATA #1 E. Top of TOp of "Trav- Trav- Permit # Well Name1 Location erse erse Forme Lime- ation" stone 127u2 #1 M. H. Miller NE-Sweswell -8u5 -913 1302h #1 Schiller Unit NE-NE-NE-lS -850 -910 13077 #1 J. Schiller NE—NE—SE—lo -839 -910 13096 #1 E. Eilers NE-NweNE-IS X2 -896 13106 #1 L. Eilers NE—SE-SE-lO X ~906 131h8 #1 K. Schiller NE-sw-SE-lo -837 -897 13180 #1 H. Weber SE-sw-NE-B -918~ -98u (ROWMER CORPORATION) 13191 Hoffman NE-SweNE-ls 1Unless otherwise noted all wells belong to the Carter Oil Company and are named on that basis. 2The symbol "X" is used where information is unavail- able or highly questionable. 28 TABLE I (Continued) WELL AND SAMPLE DATA Sample Interval Per- Per- Mg/Ca Mg/Ca Ratio for 1 Below cent cent Ratio Indicated Interval Traverse Mg Ca Limestone 0-2% 0-5 0-10 5-10 O-h 2.9 23.5 0.087 X X X X h-7 1.0 21.7 0.0hh 7-16 0.6 35.8 0.017 16-22 0.8 38. 2 0.022 22-2h 0.8 39.10.021 0-3 2.8 29. 8 0.093 0.093 0.111 0.100 0.091 3- S 3.u 2u.3 0.138 11-20 1.3 3u.0 0.039 20-24 1.9 3u.0 0.057 0-2 10.% 19.1 0.5u5 0.5u5 X 0.16u X 2-11 2..» 35.0 0.079 3-6 8.0 2a.? 0.325 X X X 0.096 6-9 3.7 30. 0 0.12a 9-11 1.9 36. 2 0.053 11-16 2.5 3s.u 0.071 0-3 3.1 21.6 0.1h5 0.1h5 X X X 3-7 u.6 2h.9 0.18h 7-16 2.3 3h.0 0.067 0-3 11.8 23.3 0.505 0.505 0.315 X X 3-6 3.9 30.8 0.125 - . 0-6 9.7 21.6 0.u52 X 0.u52 X X 0-2 8.5 15.6 0.5a? 0.5u7 X X X 1 . Intervals are generalized. For complete explanation "Consideration of Data - Selection of inter- see text under vals to be mapped". 29 TABLE I (Continued) TOp of Tap of "Trav- Trav- Permit # Well Name Location erse erse Fbrmp Lime- ation" stone 13197 #2 J. F. Miller NEPNE-Sw-ll -857 -928 13213 #2 E. Eilers NB-SB—Nwels X -906 13267 #1 Fulljames et a1 Nw-SB-Swel2 -92u -976 (NEIL WAGEHAAR) 13286 #1 L. Stevens NE-sw-Nl-15 -829 -901 1333M #1 R. Schiller NB-NB-swelo -832— -909 133u8 #1 v. Schiller NE-sw-Sw-lo X -899 l3u19 #1 J. v. Schiller NE-Nw-SE-lo -837 -90u lth5 #1 s. J. Schiller NB—SE-SB—9 -836 -907 13h99 #1 w. Miller NE—SE-NE-l6 -8h6 -911 13500 #1 E. Friday NE-wl- 1-10 -8h1 -909 13930 #2 S. J. Schiller NE-NE-SE-9 -858 -929 13550 #3 s. J. Schiller NE-SweSE-9 -853 -923 13567 #1 M. B. Hunt NE-NE-NE—16 -853 -922 13622 #3 E. Eilers NE—NE-SW-lS -850 -929 30 TABLE I (Continued) Sample Interval Per- Per- Mg/Ca Mg/Ca Ratio for Below cent cent Ratio Indicated Interval Traverse Mg Ca __ Limestone 0-25 0-5 0—10 5-10 0-2 11.5 22.2 0.521 0.521 X X X 0-3 2.3 33.u 0.066 0.066 X X X 0-5 5.5 31. 0.177 X 0.177 0.197 0.217 5-10 6.5 29. 0.217 0-10 2.h 35.2 0.068 X X 0.068 X 10.1.5 007 38.9 0.019 0-5 11.2 21.8 0.515 X 0.515 X X O-h 8.u 2%.5 0.3h3 X X 0.163 X u-ll 1.7 2 .0 0.060 0+6 12.2 20.h 0.596 X 0.596 0.359 0.07u 6-11 2.7 35.8 0.07u 0-3 11.0 22.2 o.u9u 0.49M X 0.197 X 3-10 2.3 32.8 0.070 O-u u.8 29.u 0.16h X X X X O-u 11.3 20.2 0.560 X X 0.298 X u-9 h.5 32.2 0.139 9-10 106 314-08 0.0115 0-6 12.1 20.2 0.595 X 0.595 X X 6-15 0.8 38.7 0.022 0-3 12.1 20.6 0.587 0.587 X X X 0-2 5.2 28.u 0.182 0.182 X X X 0-5 7.9 9.5 O.hl9 X 0.h19 0.25h 0.161 5’11 LL02 26.6 0.16]. 11-16 1.u 35.8 0.0h1 31 TABLE I (Continued) Top of Top of "Trav- Trav- Permit # - Well Name Location erse erse Ferm- Lime- ation" stone 136uh #1 3. Jacob NE-SE—NE-lo -863 -93h 13703 #1 M. Miller NB-sweNB-l6 -860 -925 13723 #1 A. Schiller NE-SE-NE—lS -869 -93u 1h138 #1 G. Schmiedeknecht NE—NE—SE-l6 -857 -933 1h328 #1 R. 0. Hamill saereSE-9 -862 -929 1h502 #1 State-Claybanks NB—SB-Nwel6 -868 -9u2 (MERCER OIL COMPANY) 15065 #1 C. Eilers sw-SB-Nw-lo X -918 15110 #u s. J. Schiller sw-NB-SE-9 X -921 15190 #2 S. Jacob Sw-SE-NE-lo X -919 15191 #3 J. F. Miller swesw-ww-ll X -927 15235 it J. F. Miller swer-sw-ll X -909 32 TABLE I (Continued) fl _‘—: fl Sample Interval . Per- Per- wg/Ca Hg/Ca Ratio for Below cent cent Ratio Indicated Interval Traverse Limestone 0-2% 0-5 0-10 5-10 0-5 7.h 21.0 0.350 X 0.350 X X 5-9 2.3 30.8 0.07h 9-1h 0.7 38.7 0.019 1h-16 1.0 . 37.6 0.026 0-5 12.5 22.1 0.567 X 0.567 0.321 0.116 5'9 #0% 3h.2 0.130 9-11 2. 31.6 0.087 11-18 0.6 38.0 0.016 18-21 1.2 38.6 0.031 0-5 6.5 21.2 0.307 X 0.307 0.263 0.219 5'10 6.14- 2902 0.219 ILL-18 1.0 33. 0.029 l-h 6.7 19.9 0.33h X X X X o-h 5.h 22.h 0.2h2 X X X X 0-1 5.u 19.5 0.279 X 0.253 0.172 0.0h9 1-6 7.0 28.6 0.2u8 6-10 1.8 37.0 0.0h9 10-15 1.0 38.6 0.025 0-3 2.9 3h.e 0.08h 0.08h X 0.082 X 3-10 2.h 29.8 0.081 0-5 h.2- 28.h 0.1h9 X 0.1h9 X X 0-3 3.9 9.1 0.023 0.a23 0.333 X x 3'6 503 21.8 0.2u3 0-22 7.1 20.8 0.3h2 0.3h2 X 0.328 X 2%- 7.5 21.3 0.3u6 9-11 6.0 23.8 0.253 0-2 2.7 22.h 0.109 0.109 X 0.16h X 2-8 b.6 26.2 0.175 8-11 3.3 18.1 0.180 33 TABLE I (Continued) TOp of Tap of "Trav- Trav- Permit # Well Name Location erse erse Form- Lime- ation" stone 15256 #2 E. Friday sw-Nw-Sw-lo X -906 15275 # N. H. Miller sw-sw-St-ll X -916 15351 #2 J. Schiller sw-Nv-SE-lo X -905 15359 #3 L. Stevens SW—SW‘NW-IS X -911 15u15 #2 E. Blohm sw-NE-NE-16 X -912 15h71 #h M. Schiller . SW‘SE-Swelo X -898 15h9h #2 K. Schiller sw-Sw-SE-IO X -888 15527 # E. Eilers sw-NW-NEF15 X -902 15570 #2 0. Eilers NE-SE-Nw-lo X -928 15593 #1 w. Nichols sw-NE-NE-IO -886 -9u9 (R. T. JONES) 15626 $1 J. E. a A. N. sw-Nw-Nw-ll -868 -95u Bilers . 15666 #1 Jonseek-Schiller SW—SweNE-lo X -909 TABLE I (Continued) 3h “— * Sample Interval Per- Per- Ng/Ca Mg/Ca Ratio for Below cent cent Ratio Indicated Interval Traverse Mg Ca Limestone 0-2% 0-5 0-10 5-10 0-6 6.h 20.2 0.316 X 0.316 0.239 0.11h 6-10% 3.3 28.6 0.11h . 0-2 1.9 25.h 0.076 0.076 X X X 2-10 5.5 2h.2 0.229 0-8 7.2 22.0 0.328 X X 0.332 X 8-10 6.3 18.0 0.347 13-3 u.9 2h.6 0.202 X X X 0.0h5 3-6 2.3 3302 0.069 6-9 2.0 30.8 0.067 9-11 0.5 38.0 0.013 l-h 11.8 21.h 0.550 X X 0.255 X h-ll 3.6 28.0 0.129 l-h 9.u 21.9 0.h26 X .X X X h-9 2.0 33.8 0.060 9-15. 0.6 39.9 0.015 15-21 1.0 no.1 0.02h 0-3 5.9 21.6 0.272 0.272 X X X 0-53 11.7 20.6 0.567 X 0.567 X X 0-2' 3.9 31.2 0.12h 0.12h 0.162 X X 2-5 5.7 28.u 0.199 0-1 10.1 20.0 0.506 X‘ 0.u57 X X . 1‘5 8.0 17.9 Gaul-5 5-9 6.0 230,4- 0.258 9'15 #08 2702 00177 1-5 1.6 36.6 0.0h3 X 0.0h3 X X 35 TABLE I (Continued) W Top of Top of ' "Trav- Trav- Permit # Well Name Location erse erse Formr Lime- ation" stone 15667 #2 Jonseek-Schiller NE-sw-NE-lo X -93u 15683 #1 F. Osborn Nw-Nw-SE-ls -855 -92u 15689 #2 R. 0. Hamill NE-NW-SE-9 -87h -9h5 15751 #1 Kelley NE—NE—Nw-22 -900 - -970 (OIL PRODU ERS) 15799 # S. J. Schiller sw-sw-SE-9 X -936 15805 #u M. H. Miller sw-Nw-Nw-lh -86h -935 15890 #5 J. F. Miller sw-NE-Sw-ll -8h6 -912 15935 #1 Esther Friday NE-SE-SW-9 X -9u7 16059 #2 w. Miller sw-SE-NE-16 -861 -931 161h6 #2 H. B. Hunt sw-Nw-NE-16 -859 ~926 16lh7 #1 H. P. Schneider SW—SW—NE-9 -890 -957 TABLE I (Continued) 36 Sample Interval Per- Per- Mg/Ca Hg/Ca Ratio for Below cent cent Ratio Indicated Interval Traverse Mg Ca Limestone 0-23 0-5 0-10 5-10 0-6 5.5 28.8 0.192 X 0.192 0.235 0.239 6'8 801 26.8 0.301 8-11 5.9 30.0 0.197 11-13 1.1 36.8 0.030 13-1u 1.8 2u.8 0.073 114-15 103 3500 0.038 1-6 u.3 29.0 0.1 9 X 0.1h9 0.115 0.081 6-11 2.8 3A.2 0.0 1 0-2 6.8 25.0 0.270 0.270 X X 0-2 6.6 20.2 0.328 0.328 X X 0-5 8.8 2h.6 0.358 X 0.358 X 0-6% A.3 27.0 0.161 X X 0.1h6 X 6%'9 306 250,4- 001,42 9-11 2.6 26. 0.100 11-15 1.7 BA. 0.0A9 0-1 8.8 22.h 0.389 X 0.308 X X 1-5 7.6 26.h 0.288 0-3 9.3 23.8 0.390 0.390 X X X 0-6 u.7 26.8 0.175 X 0.175 0.127 0.070 6-11 2.0 34.6 0.070 0-2 11.3 22.2 0.510 0.510 0.300 0.186 0.013 2-6 5.7 29.0 0.195 6-10 0.5 37.8 0.013 10-15 0.5 37.8 0.013 0-3 10.1 25.2 0.h02 0.h02 0.h56 0.363 0.270 3-5 11.0 20.14- 005.36 5-7 11.7 22.2 0.526 7-10 3.h 34.1 0.099 37 (Continued) TOp of Top of "Trav- Trav- Permit # Well Name Location erse erse Forms Lime- ation" stone 1611.85 #5 N. H. Niller SW—SE-SW—ll -860 -927 16620 #2 A. Schiller SW—SE-NE—IS -863 -93LL 38 TABLE I (Continued) Whig-1:" Sample Interval Per- Per- Hg/Ca Mg/Ca Ratio for Below cent cent Ratio Indicated Interval Traverse Limestone 0-2-3; 0-5 0-10 5-10 0-1—3 3.7 30.6 0.122 X 0.065 X X 173-5.; 1.6 36.7 0.003 0-1 3.9 27.8 0.139 X X 0.038 X l-h 1.2 37.7 0.032 11..-? 0.8 38. 0.022 7-10 1.0 37.9 0.025 CONSIDERATION OF DATA Selection of intervals to be mapped. Preliminary anal- yses of samples from several wells located across the struc- ture indicated that very little dolomitization had occurred at depths of more than 12 feet below the top of the Traverse limestone. Highest ratio values were confined to the top few feet. A chart was prepared which showed sample intervals be- low the top of the Traverse limestone in the various wells. Distribution of the sample intervals was noted to be high at depths of about 5, 10, and 15 feet. In order to have as much control as possible for mapping, and to Show the de- gree of dolomitization in the upper few feet of the formation, the following sample intervals were selected (given in feet below the top of the Traverse limestone): O to -2 or -3 (Figure 5.) 0 or -1 to -5 or -6 (Figure 6.) 0 or -1 to ~10 or -11 (Figure 7.) -5 or -6 to -10 or -11 (Figure 8.) 0 or -1 to -15 or -16 -10 or -11 to -15 or -16 39 MO Ratios for these intervals were calculated from the results of the analyses of the well samples. These were plotted areally on base maps of the Stony Lake field and the respective values were utilized in constructing a series of lithologic ratio maps. Although ratio maps were con- structed for the last two intervals listed, control was so lacking and results so anomalous that inclusion of these maps was considered superfluous. The lateral extent of dol- omitization of the different intervals can be seen by exam- ination of the map of a particular interval and the degree of vertical dolomitization can be seen in part, by compar- ison of the maps of the different intervals. Comparison of the various lithologic maps to a subsurface structural con- tour map of the field (Figure A.) should indicate whether or not there is any positive relationship between the degree of dolomitization, as reflected by the Mg/Ca ratios, and the structure. Vertical extent of dolomitization. Mg/Ca ratios of the samples tested ranged from 0.013 to 0.596. The general pat- tern of vertical distribution within the Traverse limestone seemed to be from a high value in the upper S or 6 feet to a low value at a depth of about 13 feet and then a very slight increase in the ratio below that depth. Some rather low ratios were noted in the top few feet of the formation and in nine of these instances a slight increase in the ratio was observed in the second sample. hl In four cases this increase may have been due to the inclusion of some of the overlying shale in the finely ground top samples. Previously, several analyses had shown this shale to be somewhat limy with an average Mg/Ca ratio of 0.083. In the other five in- stances the samples were free of shale, and lower ratios in the tOp samples may have been due to failure to get a rep- resentative sample. The possibility also exists that the ex- treme upper part of the formation may not have been as heav- ily dolomitized in places as a zone slightly below the tep. Inspection of the lithologic ratio maps revealed the following information: # Sample Interval (in feet Average Range of below top of Traverse ls.) Mg/Ca Ratio Mg/Ca Ratio 1 O to ~2 or ~3 0.321 0.066 to 0.587 2 0 or -1 to -5 or ~6 0.321 0.043 to 0.596 3 0 or ~1 to ~10 or ~11 0.208 0.038 to 0.363 h 0 or -1 to ~15 or ~16 0.1h5 0.0h0 to 0.292 S ~S or ~6 to ~10 or ~11 0.124 0.013 to 0.270 6 ~10 or -11 to -15 or -16 0.0M6 0.013 to 0.111 TABLE II h2 The similarity in ratios between intervals 1 and 2 would seem to indicate that the first six feet of the for- mation were dolomitized equally throughout. Comparison of successive values obtained for small sample intervals near the tOp of the formation, however, showed that a steady de- crease in the ratio often can be expected from the top down- ward. Similarity of the two ratios may be due to the occasion- al presence of a less heavily dolomitized zone at the very top of the formation. The decrease in the average ratios at successively lower intervals, as illustrated by intervals 2, S, and 6 (Table II), indicates that dolomitization de- creases with depth, rather sharply at first and then more slowly. InSpection of values obtained from samples of indi- vidual wells showed this to be generally true with a very small increase in the ratio occurring below depths of about 13 feet in some wells. The decrease in the ratios shown in intervals 2, 3, and h also indicates a decrease in dolomit- ization or magnesium content with depth. The flattening effect of the overlapping intervals is apparent when com- pared to ratios obtained for intervals 2, S, and 6. Dolomitization ingproducing zones. Samples through the producing zones were available from some wells. Analyses of six of these wells did not reveal any significant change in the Mg/Ca ratio in these samples. Both high and low ratios were encountered depending largely on the depth of the pro— ducing zones below the top of the formation. 1:3 Lateral extent of dolomitization. Examination of the lithologic ratio maps and individual well analyses indicates that some dolomitization was present across most of the Stony Lake pool. The presence of both high and low ratios distributed over the field would further indicate that the degree of dolomitization or quantity of magnesium.present varied considerably and that develOpment of the dolomitized zones was rather irregular. Dry holes located on the flanks of the pool in sections 8, l2, and 22 did not have Mg/Ca ratios significantly different from those obtained in wells nearer the center of the pool. RELATIOHSH E OF DCLCNITIZATIOT TO STRUCTURE If the assumption holds true that dolomitization occurs along tension fractures developed on the apices of folds, a comparison of the lithologic ratio maps and the structural contour map of the Traverse limestone in the Stony Lake pool should show the existance of a definite relationship or attern. To this end the various lithologic ratio maps were con- toured in several patterns. In order to develop any possible relationship each map was contoured individually several times. An attempt was also made to develop patterns which would be common to all ratio maps. Where control was lack- ing the Ng/Ca ratios of intermediate sample intervals were used as guides. Because most dolomitization apparently occurred in the upper six feet of the formation and because of the greater control available, emphasis was placed on ratio maps of the upper part of the formation. The ratio contours as shown in Figures 5, 6, 7, and 8 represent but a few of many possible interpretations. The subsurface structural contour map of the Traverse limestone was constructed from.data secured from the Mich- igan Geological Survey and the Carter Oil Company. In sever~ a1 cases of conflicting data the samples were checked and uh 1L5 those values taken which best coincided with the lithologic change from shale to limestone. The density of control and logical pattern left little necessity for questionable contouring of the structure. 2 Direct comparison of the lithologic ratio maps and the structural contour map failed to disclose the existence of any recognizable relationship or pattern between them. Exam- 'ination of the individual well analyses also failed to es- tablish any definite relationship between the structure and the lateral or vertical extent of dolomitization. No recog- 'nizable pattern such as might be expected in the case of cross- folding, folding, or doming was apparent in any reasonable interpretation of the lithologic ratio maps. ORIGIN OF DOLOXITE N THE STOKY LAKE FIELD Several possibilities exist as to the origin of the dolomite near the top of the Traverse limestone. Although none of the individual well analyses showed a significant increase in, or sustained high value for, the Mg/Ca ratio at depths down to 2h feet, it is entirely possible that a number of irregularly spaced fractures extend down into the formation and that, at one time, magnesium-bearing waters circulated through these fractures from below. The relatively impervious beds of overlying shale would, in this case, tend to direct the waters laterally at the contact with the limestone. Interruption or discontinuance of the circulation could account for the irregular pattern of dol- omitization. Because of the age (post-Hississippian) assign- ed to the folding, it seems unlikely that dolomitization could be due to the circulation of ground waters through tension fractures developed as a result of uplift and expos- ure following the folding. If unrelated to fracturing develOped during folding, the dolomitization might be due to the replacement of lime- stone beneath warm, shallow seas or lakes sometime after partial lithification of the limestone. The circulation of magnesium-bearing sea waters through borings or Openings M6 #7 due to marine vegetation might then account for the irregu- lar distribution of the dolomitized areas. Occasional re- cession of the unstable seas and subsequent non-deposition is also a possibility. It is not improbable that the Trav- erse limestone underwent uplift without appreciable folding on one or more occasions. In such a situation the dolomite could be due to dolomitization of the limestone by downward circulating groundwaters or to leaching of calcium from a dolomitic limestone. In the latter case subsequent compaction and re-dissolution and replacement may have served to impart to the dolomitized zone its present relatively non—porous condition. CONCLUSIONS The versenate method for determining calcium and mag- nesium in limestones and dolomites has proved to be rapid, simple, and accurate. The preparation of lithologic ratio maps based on Mg/Ca ratios appears to be a simple and log- ical way of presenting information obtained by applying the versenate method to analyzing a series of samples from a dolomitized zone in a particular area. Although comparison of structural and ratio maps of the Traverse limestone in the Stony Lake pool did not reveal any significant relationship between the structure and the de- gree of dolomitization as indicated by the Mg/Ca ratio, the possibility of such a relationship existing in other for- mations and in other areas is not precluded. Only after ex- tensive comparison of many structures and formations by means of structural and lithologic ratio maps can the value of this method of locating structural features and dolomit- ized zones be evaluated. The combination of the versenate method for determining calcium and magnesium and.mapping of the results as a Ng/Ca ratio may yet prove to be a useful tool for the geologist. Q8 BIBLIOGRAPHY Banewicz, J. J., and C. T. Kenner (1952), "Determination of Calcium and Magnesium in Limestone and Dolomite", Analytical Chemistry, V01. 2h, No. 7, pp. 1186-1187. Cheng, K. L., T. Kurtz, and R. H. Bray (1952), "Determin- ation of Calcium, Magnesium, and Iron in Limestone", Analytical Chemistry, Vol. 2h, No. 10, pp. 16h0~16h1. Cohee, G. V. (19h7), "Lithology and Thickness of the Trav- erse Group in the Michigan Basin", U. S. Geological Survey Oil and Gas Investigations, Preliminary Chart 28. Fix, G. F. (195h), Geologist, Carter Oil Company, Personal Communication. Geikie, A. (1882), Textbook of Geology, London, MacMillan and Co. Hach, C. (195h), Chemist, Hach.Chemica1 Company, Personal Communication. Hake, B. F., and J. B. Maebius (1938), " Lithology and Thick- ness of the Traverse Group of Central Michigan", Paper, Mich. Acad. Sci., Arts, and Letters, Vol. 23, pp. hh7~h61. Hatch, F. H., R. H. Rastall, and M. Black (1938), The Petrol- ogy of Sedimentary Rocks, London, Allen and Unwin Ltd. Henry, w. H. (19u9),‘"An Investigation of Subsurface Reef Conditions in the Traverse Group of Michigan", Thesis, Michigan State College. Jodry, R. L. (19Sh), "A Rapid Method for Determining the Magnesium/Calcium Ratios of Well Samples and Its Use as an Aid in Predicting Structure and Secondary Porosity in Calcareous Formations", Thesis, Michigan State College. Landes, K. K. (19h6), "Porosity through Dolomitization", Bull. Am. Assoc. Petrol. Geol., Vol. 30, No. 3, pp. 305-318. Michigan Geological Survey (1953): Summary Of Operations, Oil and Gas Fields. #9 50 BIBLIOGRAPHY (Continued) Schwartzenbach, G., and H. Ackermann (19u7), "Complexon V. Ethylenediaminetetraacetic Acid", Helvitica Chimica Schwartzenbach, G., and H. Ackermann (19h8), "Complexons XII. Homologs of Ethylenediaminetetraacetic Acid and Their Alkaline-Earth Complexes", Helvetica Chimica Acta, Vol. 31. pp. 1029-1ou8. Steidtman, E. (1917), "Origin of Dolomite as Disclosed by Stains and Other Methods? Bull. Geol. Soc. of America, V01. 28, pp. ABI-ASO. II I, ONTONAG ON GOGENC “lsc\ 01,87? 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STONY LAKE OIL FIELD C7 FIGURE 1. INDEX MAP OF 51 II /,’/ _ .1.“ B I \\ ‘A _ x ’5‘ . °=§sEE ' w hi I _ W“ ~ ._L -_ y =7=J . ~=I «UR‘NER'FIT- CAM-rt“ on ”510701! CO-N'fi, 7', JO” 5 0M Panama?! CARTER OIL co. A" ‘14 mos I5349 I559?! ; 24 .5983 o I OI I /.‘, I . :, IAIN-N I /_ ' _ ’ Z Carin-‘6. 9H. :9. If can'rzk on. co. gAfiwaE‘I‘Kuou. co- __c.Tfi7_27/?'a—/ICLM SCARTE‘L OIL I/gn [He/'5 Z7 A“ '5’70 3644 02 Q I l/ V” I3I80 "MI" ”52055“ 5'3"" Isohs my I “I O. M- OI ~ » I O 3 L-“ H.5eIIneIJcr HI Rube ‘. R 5 , .E Ierfi Jan n Oral/e l I ‘ Roxm an. n- r. L. v .. "7 961F727: o/z.‘ awry? OIL chW’Eafigfi‘a—m WWW co, L, f ‘ ILIM . mew I3530 vasoo [3334 ‘ I34I9 I3077 I2930 I3I9'7 4‘ 02 O 2 0| 0 I o I .I o I .Qa ~ .— fi _ / ‘I P4 17/05 I4328 mm ”3256 [98,0 V I o I e 4 .a . 5 web" A?” HdI'IIcIA- A’. llarnr’l/ , . ' Harm/K 1 E. Fr/‘r/a: J. F. Miller CARTER c- co- L W an ce- , ‘17,, ‘ L .seas I3550 I3445 C m [@345 CARTER “322', 73“?!“ .542. o I .3 o I o I o a A 4 1 7 ‘ l 0,, I5799 mm. ’5”? ‘ . 1547’ '04.“ ' a G o 5 O 2 C 4 :2 , E. FI‘Id 5 J 527‘: //er I'.'5c/II‘//€-" ‘1 Kdfla’i’lié'i/ML 1 \ fink,” \ $727711 ~52 FIT - CARTER OIL o. L 1314! "\1 EAETEfi 0”- co. cmzv 1 cARTEH IL c5 ”553 5567 ”418 “9299 . , Isaac I536 \ o I o I .I 0 3 .I $~ I E / ,n (‘ 7Aiégégfifié fl #4 ”I " W 154/5 25537 55% 1.6537 1544' Imp; e z o 5 0 6 o r o 2 . 4 H. omng” M. NW; 5. axe/m 7 Mari Sg’zM/en A V ,7- 5‘. 49/?er 5c1p/Ier Amt.“ MM Mill Ier E. But t/emch / TWE pr ('6- CANTER 01L co, CAk‘TER on. ca. EAR-rm! all. to. CAQTEQ all. CAETF OIL ca oven-12 OIL. 7573mm \IN I45oz mos I349? I326!» [3243 men I3723 +9,” VI NJ OI e I CI 0 I o z ' I .I I; *4 L‘vi-Leqijkc‘i. 4” —== == ==” I60" .5359 I957 Isssa II'I'” '- O . o 3 @’ 0.4 '50.; {r ’- l — — 7 1 M. Mil/er . 4’, Mil/er 1 1 [/IrnHD/f’man A ne: SC/H/Icr -f:/\/\ n 1 £ 1 4 - M4 36‘ L ’3 1 , I; II- A‘ Lilli FITJTM "“ I459 I I 529 .3434 ‘ O I 0 Z w «r, , Vrv I EN I ‘ I I I \ 1 BA “ I J I "‘4' fl “ '1’ L‘ L571 thel EIIeI‘o F. Osborn A390,!" - , IA 1 ALLIED E . NC. . 1:65 . ‘ I4906 I5. ‘ CZN ' I F I G U R E 2 . r” ' I I . STONY LAKE OIL FIELD ifare-L'pfv.://,(5 WW CLAYBANKS Twp. (T '3 N, R [8 W) a. I E . - . ;575I I I. ‘ OCEANA CO.,MICHIGAN M" 0 . - _L ‘ SCALE. 1 INCH-4MILE i LEGEND: OIL WELL 0 \ «:7.- Km” :1 ,1 4-— l _ D R Y H o L E 4} . MAF’ OBTAINED FROM MICHIGAN GEOLOGICAL SURVEY FORMATION, THICK- SYSTEM GROUP I-IEIIBHR, MESS LITHOLOGIC DESCRIPTION OR STAGE (FEET) M I . S Antrim S 210 Brown to dark brown Shale shale D E V _-_.—. __15;_. Light gray, crystalline "Traverse \\_ limestone H n 60 Gray shale w/ streaks of _____ Dormation gray limestone E_—h*—q Brown crystalline 15 ’ (dolomite 30 I Brown to tan limestone D & dolomitic limestone T Tan to light gray, foss- E R iliferous and/or crys- A 190 talline limestone w/ V V vugular and coralline O E Traverse porosity R S Limestone Light gray, crystalline N E limestone - I G R --10- Brown, dolomitic lime- A o 35 \\ stone w] anhydrite U __.1§_L Anhydrite and dolomite N P ____15__+ Sucrosic dolomite 80 Sucrosic dolomite and anhydrite Sucrosic dolomite Bell Shale ho Gray shale , Dundee 50 Light brown, crystalline i Limestone to granular limestone FIGURE 3. GHHFRALIZED STGATIGRAPHIC SECTION OF THE TRAVERSE GROUP IN THE STOHY LAKE OIL FIELD SCA E: l 53 NCH - lOO FEET s FIGURE 4. STRUCTURE CONTOUR MAP OF STONY LAKE OIL FIELD ‘ DATUM IS TOP OF TRAVERSE LIMESTONE CONTOUR INTERVAL Io FEET SCALE: 4 INCHES = l MILE. LEGEND: . OIL WELL 4r DRY HOLE O 0 (DO A? o , /, up I24 ‘ 423 542 .31 9/ .270> V H 0.00 /\\:0: 3J0 0‘00 .390 076 /- Oo / V; k . \f\ /5IO I ICON .066 .200 ' > O ‘5 /\'300 o '6 o \_/’ \\ '5 '4 FIGURE 5. MG/CA RATIO MAP ’ TRAVERSE LIMESTONE ,328 ‘ . I O'TO —2‘ OR -3' ‘ STONY LAKE OIL FIELD I SCALE: 4IN.=IMI. C.I.=.Ioo .l77 FIGURE 6 MG/CA RATIO MAP TRAVERSE LIMESTONE O'OR -I' TO -5' OR -6' STONY LAKE OIL FIELD SCALE: 4 IN.: | MI. C.I.= .IOO ‘J \I < r LI FIGURE 7. MG/CA RATIO MAP TRAVERSE LIMESTONE 0' OR -I' TO —IO' OR -II' STONY LAKE OIL FIELD SCALE: 4 IN.= I MI. C.|.= .IOO lbw- - 239 O / 374 .049 .045 o .096 o .09l o R \_ .150 V .200 .070 .IEI .1981 FIGURE 8. MG/CA RATIO MAP TRAVERSE LIMESTONE -5'0R ’-6‘ TO —IO'OR -II' STONY LAKE OIL FIELD SCALE: 4 IN. = I MI. C.I.= .050 IunQT a a! 3., T7 95‘ NICRICRN SFATEIWNIV. LIBfiARIES I|IIIIIIIII”WIIII"III”llIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 31293102774266