det gas y eval yac-arenas super

7/27/2019 Det Gas y Eval Yac-Arenas Super

1/14

SPE7920

FORMATI ONVALUATI ONNDGASDETECTI ONNSHALLOWLtWPERMEABI LlYSHALYSANDSOFTHENORTHERNREATPLAI NSPROWNCEbyG. C. Kukal , CERCtV p.

)Copyright1979, American Instituteof Mining, Metallurgicaland Petroleum Engineers, Inc. This paper was presented at the 1979 SPE Symposiu!oon Low?rmeabi1ity Gas Reservoirs, May 20-22, 1979, Denver, Color8do. The material is snhjcct to correction by the author. Permission to copy i~ restricte, m abstract of not more titan300 words. Write: 6200 N. Central Expy., Oallas, Texas 75206,

ABSTRACT adjacent to production J the Bowd@in Dome Field(Figure1).Montana log, core, and productiondata are com-bined with geology in a systematicapproach for im- This report uses e.synergeticapprnach for im-proved log analysisof Jhallow upper Cretaceous gas proved la interpretation. The litholc~; and .~iner-sands having a high silt-clay content. Qualitative alogy of the Bowdoin Member of the Carlile Shale and(overlay)techniquesare reviewedwith emphasis !pon the Eagle Sandstone are descried in detail. Thisthe normalizedAt - compensated nc.atronoverlay for informationie useful for making predictions of loggas detection. responseand in refiningloggingassumptions.Sugges-

tions are made for cross-plotmethods based uponLog interpretationof the Bowdoin Member of the these log responses that may be useful to detectCarlile ..,~leand Eagle Sandstone in the area periph- gas and/or to identifymineral components of theeral to the Bowdoin Dome Field is discussed in detail. complex lithology. Finally, suggestionsare presentePorosity tool responses are examined with respect to for improving~zantitative log interpretations.observe~ lithology and mineralogy. Lithology cross-plot when compared to predicted log responsesmay he LITHOIOGY AND MINERALOGYan aid in detecting the p~esence of gas and mineralsthat could be related to natural fracture systems(e.g.,gypsum, pyrite). The Upper Cretaceous clastic section in theBowdoin Dome arealis dominated by shales and clayey

siltstones. The rock may carry variable amounts ofQuantitative techniques for estimation of @ffec- gypsum, pyrite, carbnates, and micas. Reservoirtive porosity, volume clay, and water saturationare rocks.may cor :ainup to 50 percent clay mine~alz,presented. The Total Shale Relation appears to giveuseful water saturationvalu~:.. Log parameters re- The Bowdoin Sand (Figure 2) is a poor quslitylatir; to this equation are generalizedand refined. reservoir rock except where fractured. Most of theINTRODUCTION gas storage !. in silty laminae less than one centi-meter thick. Permeabilityis low and artificial

stimulationmethods are employed to make the narginalWith increasinggas prices, explora~.onfor wells more economic.shallow, low-deliverabilityresources in the NorthernGreat Plains Province is becoming more attractive. Table 1 is a summary of the recent x-ray miner-Log interpretationhas alw~;s been a problem in the alogical analysis of 30 sidewall cores taken fromUpper Cretaceous of north-centralMontana due to the two wells.18 The mineral compoeitlonfor each wellextreme shali~essof potential reservoirs,very fresh is expressed as weight percent and is averaged intoformation water, high water saturations,complex a total rock analysis and a clay size fractionlithology,and uncertain logging assumptions. It is analysis.the goal of this paper to suggest techniquesto im-prove gas detection an~ formationevaluation,partic- The sieve size distributionof the 296~c.resularly in marginally eccmomic areas peripheral or (Figurel)consistsof 60 percent silt (2-62 pm), 35>ercent clay (62 pm).Referencesand Illustrationsat end of paper. The analysis shows the rock to be made up dominantlyNotice: of quartz (52 percent) with the major clays beingReference to a company or product name is illite and kaolinite. Pyrite and gypsum aze presentused for descriptive purposes only and does not imply in significantamounts.approval or recommendationof the product by CERCorporation and/or the U.S. Departmentof Energy, to The 0370 cores (Figure1) are composed of athe exclusion of others that may be suitablm. similar size distributionwith 62 percent silt, 35

-.-W)


2/14

percent clay, and 3 percent sand. The mineralogy ie Logging service companiesoperating in nortnearly identical to the 2962 well. central Montana are veryconsciom of log qualityStandard logging speeds for neutron logs are 900

Visual inspectim of the 0296 core (Figure1) hr because of low count rates. Zn addition, repreveals the 3owdoin Member to be a dark gray aricaceous\

runs of statisticaltools are advisable through tshale with s% tstone lenses and laminations. Second- Bowdoin Section.ary pyrite is estimated at volumes up to 10 percent inthe intervalbetween 1,440 and 1,4469(Figure 4). Thin GAS DETECTIONdense gray limestonesare at 1,392 and 1,416. Silt-stone lenses are nest numerous in the interval 1,375 - Gas is detected principally by normalizing1,392and 1,397 - 1,410,with best development between At curve to the neutron porosity curve in an ove1,380 - 1,385! fashion. This technique has bee~ previously documented6r~1~11110 and has seen w;.despreaduse i

The Eagle Sand (Figure2) is a better quality Bowdoin Field since 1977. The &t curve is normareservoir rock than the Zowdoin but often requires over the neutron in average tight sands. The t%structuralclosure for gas accumulation. The unit curves generally t:ack because of similar ttitilhas increasedpotential tcr local stratigraphictraps sponse. Gas is detected by virtue of the neutroin the shelf sand and siltstone-shalefacies as de- At response in a gas zone. Neutron porosity decfined in the geologic l.iterature.~=In the Bowdoin ?.nresponse to gas and At increases,producing aDome area, reservoir development is typically in vinual crossoverof curves.clayey sandy siltstones. In the 0296 well, good developmentis shown

X-ray analysis of five Eagle sidewall cores in the Eagle between 540 and 550 ft Q?iqure.3). Thwells 03,70and 2962 (Figure1) show a uniform mineral Bowdoln (Figure4) develops an attractive crossocomposition. The composition (by weight) averages between 1,377 and 1,390. The zone in the Bowdoi63 percent quartz, 15 percent illite, 8 percent kao- sulted in 13 MCFD before stimulationand after flinite, 3 percent dolomite, 3 percent feldspar, 3 per- ture cleaned up to 80 MCED. The Eagle tested becent montmorillonite,3 percent chlorite, anf 2 per- 5 and 10 MCFDbut may have some formationdamagece.~tyrite for the total rock. The clay fraction present, wells in the field must produce at leasanalysis is 36 percent illite, 28 percent quartz, 15 100 MCFD before they are connected to pipeline.percent kaolinite, 10 percent montmorillonite,5 per-cent calcite, 3 percent chlorite,and 3 percent mixed It has also been customary to compare 0-60layer clays. cent density porosity across two tracks with son0-66 percent porosity across one track for visua

Point count microscopic analyses of three select- tection of when q exceeds 50 percent. This pred 0296 core samplesJ indicate an average Eagle compo- tice is based upon the notion that:sition of 48 percent clay matrix, 24 percept quartz,7 percent metamorphic rock fragments (mostiyquartz), Volume Clay = q = !%a - E&5 percent dolomite, 5 percent plagioclase feldspar, flsa2 percent sideri.te{ironcarbonate), 2 percent chert

. . . .(quartz),1 percent glauconite, and traces of biotite, where @sa = apparent porosity from the somuscovite, and pyrite. $da = apparentporosity from the de

In a clay mineralogy study of Pierre Shale (Fig- In the case of the Bowdoin dnd Eagle, thieure 2] samples taken west, south, and east of the not be a good assumption because (@da] is not nestudy area, it was found that the dominant clay min- sarily effectiveporosity, SOtiLC compaction correrals are mixed layer illite-smectite (montmorillonite tion factor varies with dc.>thbetween 1.4 and 1group minerals] and illite.~7 Shales of the Telegraph within the normal interval compared, and unusuaCreek equivalent (Figure2) that were deposited in the olo~ effects are not taken in,toconsideration.near shelf marine environment are +i~picallycomposed Furthermore,VCI is equai to q only when dealinof 70 percent clay minerals, 25 percent quartz, and a dispersed system which mostcertainly is not t5 percent plagioclase. The clay minerals are further case in the Bowdoin. The practice of drafting tbroken down into 7G percent mixed layer clays, M sonic porosity curve on the density porosity shpercent illite, 10 percent kaolinite, and 5 percent be discontinued.chlorite. The reason for the disparity of this ddtawith that observed in the study area is net under- Xn lieu of qprese>tation, gamma ray alonestood. do quite nicely for quick-look shaliness estim

This is true because the iilite-kaolini.teatioLOGGING PROGRAM AND QUAL.[TY20NTROL.- mains constant within each section being evaluaA spectral gamma should be run in the area to s

Well economics favor runrdcg a complete suite of uranium and thorium disturb this prediction?.logs. A few thousand dollars spent in formationevaluationmay maximize production, reduce operating Now the responsesof the several porosity lexpenses, reduce completioncosts, or help eliminate various minerals will be exa~ined. This will hunnecessarywell completions. A minimum program us understandhow changes in lithology and mineshould include inductionor laterolog, c~mpensated will affect our overlay technique gas detectionneutron or sidewall nev.eron,sonic, and compensateddensity. The proximity or microlaterologwith micro-log is also useful.

nc


3/14

SONIC RESPONSE porosity. In reality however, the response is alsoinfluencedby the formationstihermalneutron captu~eAcoustic travel times qenerallyvary between 150 cross section (2), Furthermore,the formation ex-and 70 psec/ft in the Bowdoin and Eagle section. The hibits a lithologyeffect which is related to thehigh travel times (lowvelocity) reflect a low degree thern!alizingability of atoms other than hydrogen.of compaction and a high volume of clay. Sonio com-paction correction factor (Cp) vbzies generally be- The ability OF an atom to thermalizeneutronstw(en 1.4 and 1.0, the compactionincreasing with is related inversely to its atomic ntier.g Thedepi.h. aton@c number reciprocalsfor the common elementsare presented in Table 2. Zt shouldprove useful toThe clay minerals and micas are plate>-minerals develop this concept to better understandthe lith-and have a high degrae of anisotropism. With in- ology effect. Mineral velumes should thermalizecreasing compaction there ie e tendency for theme neutrons according to the follo~.ag relatim~minerals to foliate perpendicularto the principal

stress (overburden). since sound travels much faS~~Jr KTh Molecule:3/cc!mineralperpendicularto the platethan it aoes parallel, the ThermalizingIndex (TX)= KTh Moleculeb~& (quartzAt reflects the degree of compaction -- particularlywhen compared to a measurement that dot%gnot respond (6)to this preferred orientation (nautron) . . . .

whereTable.4 swrizes the effect of various minerals KTh = Molecular thermalizingcoefficient=upon the sonic log. These calculationsassume Cp = 1, ~+~+~At fluid = 189 Psec/ft,and that the following re- Z1 Z2 Zx (7)lationshold: . . . .(the sum of the atomic number reciprocals forA~a=At quartz (Vquartz)+Atmineral (Vmineral) each atom in a molecule)

. . . . (2) Ndand Molecules/cc= /M (8)At = At~ + @ (Atfluid- Atma) . . . .. . . . (3)where N = Avogadro!s number- Atma quartz d x gra in density$sa = At&id - Atm quartz . . . . (4) M = Molecular weight

where V = volume % A quartz standard is chosen for convenience becauseAt = travel time we are dealing with shaly sands.@ = porosityma = matrix Table 3 summarizes the aesumtions used in cal-@sa = APParent sonic porosity relative culating the ThermalizingIndex for each mineral into quartz. the study area. l?i,qure5plov.sthe !l?hernwdizingIndex versus Apparent Quartz Nautron Porosity. sincThe calculati~n for the platey micas and clays is it is here assumed for comparativepurposes that

based on the assumption that velocity varies between15,000 ft/sec and 5,000 ft/sec depending upon crystal- porosity is dependentonly upon thermalizingabilitythen all the points should Lie along a straight linelographicorientation. Since perfect orientation is defined by the quartz point and water point. Thenot possible, an average velocity of 12,000 ft/sec is apparent quartz neutron porosity can be read for anyassumed. In the case of kaolinite,orientation is plotted mineral. Comparison with the Kydrogen Xndexnearly random and velocity is assumed to be 10,000 shows similaritiesto the new approach. The TXZt/sec. method, however, adds into the estimationthe effectof Uthology for atoms other than hydrogen and isOther responses of significanceare those of therefore more useful. For example, a rock composepyrite which increasesfisarelative to quartz, the of 100percentdolomite having O percent effectivecarbonateswhich slightly decrease@sa relative to. porosity will read 4 percent apparent quartz neutionqua;tz, and gypsum which has nearly the same At as porosity. !l?hiss reasonablewith respect to ~~pirquartz. cal charts relating neutron lithologyeffects.

COMPENSATEDNEUTRON LOG RESPONSE It is clear that all clays will-cause incre..sin apparent neutron porosity (?na)but not to theThe CompensatedNeutron response ie most directly same degree. For example a rock consisting of 100

related to the ability of a formation to thermalizeneutrons. Since hydrogen has the greatest thermal- percent kaolinite and O percent effectiveporosityshould read approximately39 percent quartz flna.izing propensity, it has sometimes been useful to use 100 percent montmorilloniteand O percent porositya Hydrogen Index (HZ) in order tounderstandhow a would read 17 percent quartz @la. Neutron responeegiven mineral.will influencethk neutron response. to illite is somewhat underestimatedfrom T!Idue to~= = hydroqen atoms/cc (Mineral) a comparativelyhigh Z.

hydrogen atoms/cc (Witer) .. . . (5) Table 4 illustratesthe neutron response to arock having 15 percent eff~etive porositifand 10 perIt has been generally accepted that gypsum (CaS04 2 H20) with HI = 0.48 will exhibit a CN response of cent impurityof a given mineral in an otherwise 90perf:er,ture quartzose sandstone.14 This should48 percent limestoneporosity. Likewise, calcite

(CaC03)with a HI = O should have O percent limestone eerve as an indicationof the relative influence ofthese minerals and should be useful in interpreting..


4/14

lithology -- particularlywhen compared to the re- A major goal of well log analysis is to try to re-sponse of other porosity logs. For example, the fine these parameters so that flda~ @effective.presents of 10 percent gypsum will produce a responseof 1.7 percent $na.lb Carbonates cause only a slight First we will look at matrix density. Refine-increase in @na. Pyrite will also cause increases m ment of grain density and apparent matrix density isneutron porosity. EV@n though TI is low, the high Z summarizedin Table 5. Several techniques arewill actually produce a substantial increase [from utilized to generate this data. First, grain densi1!5percent to 19 percent~a with 10p@rcent imPuritYin measurementsare made on core samples. Second, thea rock of 15 percent effective porosity).4 rocks are broken down into their mineral constituenas defined by x-ray analysisas presented in Table 1semi-compactedshaly sections in the stufiyarea we#ght percent is convertea to volume percent, andcommonly reatiquartz @na in excess of 45 percent. the rocks agrain ancl pa (~ma)arepresenteanlable4.This is due principally to the lithologyeffects Df Finally, the rockstare broken tiownas above intoillite, kaolinite, gypsum, anclpyrite, to effective their mineral constituentsby methoa of microscopiporosities in excesskof 20 percent anilto the adsorp- point count antithe clay matrix is assumetfio havetion of water particularlyby the expandable-layer the same agrain ana Pma as calculated by usinq x-rayclays. analysis.

The Ardmore Bentonite Bea [at 520 ft on Figure Several interpretationscap be mek!srelative t3) antinumerous bentonite jn the Claggett Shale the tiatain Table 5:reatl60 percent flna. These beds are composes of 95percent montmorillonite~7,are unaercompacteacom- 1. The density tool will reaclvery Yearly traparea to the sectionbelow, have a high effective aensity in both the 130waoinsna Eagle sec-porosity, ana carry a large volume of adsorbeawatez. tion.Because of the clissimilaritybetween these bec?sanathe rest of the section, it is cautionednot t~ use , 2. A good practical Pma for use in the Eagleany clay parameters from this interval in making is 2.70. This value is supportea by allgeneralitiesabout clay response in the underlying the clata.section.

3. Pma clay i n the E~yle ana I+owaoinis veryDENSITY RESPONSE similar to Oma cf other minerals,ana forthis reason it is not very significanttoThe apparent aensity for a rock of O percent correct flaafor shaliness.effective poroti~tyread by the density tool is re-latetlto the grain aensity of the material by the A Organic matter is observes in the 0296followingequation; .. Bowdoin section as abunclantbrown Iaminae.Differences in ~ma from grain .5ensity

Pma = 2 agrain Z/A (91 measurements ana x-ray analysis reflect. . . . this volume.where

Pm = Pa = clensitytool response to 5. Generalizationsregaraing Pma in the Bowtla material having O percent must assume that organic matter is equallydistributesthroughout the section. Sinceporositydgrain = grain density thie may not be the case, it may be best tZ/A = atomic number/atomicweight assume that Pma = 2.68 (Eromthe graindensity measurements)ana to calculate@e

Table 4summarizes$he again antiPZ,for the minerals by using a clensity-neutronrossplot.founclin the BowcioinDone Fielcl. AS an example ofconversion,gypsum having a true grain Ciensityof The density of formation fluicl(P~l in the in-2.32 anclZ/A = .5111 has a p- = 2.37. Thus the . vaaea zone of a gas-water system is quite oftendensity tool has a response that will cause it to assumea to be 1.0. This number may be improvedreaa gypsum more dense than its true Ctensity. forThis effective porosity cieterminationsby takingphenomenon 5.sof importancewhen trying to interpret into considerationthe pm -agrain relation,salinitporosity from the density reaaing. Sxo, anclgas aensity (phi. The following relationis approximate

Apparentdensityporosity [@aa)is expressedbythe familiar relation: Pf = [1 - s~o) ~h + Sxo Pmf . . . . [11where

@ka = ~~a~ ~~ . . . . [10] Sxo = water saturationof the flushed zowhere Ph = aens~ty tool response to hy&ocarboPnlf= clensitytool responsetomua filtra

Lhna= aenaity response to a materialhaving O percent effective porosity Ur,clerormationconditions in the 0296 well,for ex-pb = aensity log reaaing ample, SXO = .85, Ph = .03, aza Pmf = 1.11, sopf = tlensityresponsetoformationfluid in f = .95.vicinity of wellbore. , ,

00


5/14

.1

LITHOLOGYCROSSPLOTS then equates the two and solves for Vsh.7 Bothtechniquesseem to work well but require goodassump-For gas detection we have been relying heavily tions..-penthe compensatedneutron-sonicoverlay. We havebeen taking advantage o< t~ol response to ges. Neutron Probably a better techniqueof Vsh estimationdecreases while sbnic increases. We should pose the is through the use of gannnar~y. This technique,question: Will varioue secondary minerals that may although used widely elsewhere,is not readily appliedbe fracture related cause a masking of the gas re- in the Bowdoin Dome Field. This is because of thesponse? The answer is yes. Table 4 demonstratesthat absence of any clean zones within the section. TO@na - @sa will increase significantlywith the addi- get around this problem, it is suggested to crossplotion of gypsum, si.deritetand pyrite. For example, Vsh from a neutron-densitymethod against gamma. Thea clean rock that has 10 percent gypsum and 15 percent intersectionof the line defined by the plot with theeffective porosity will mask gas effect 3.8 porosity O percent neutron-densityVsh line will give anunits. approximate value for clean sand. The value forgannnaclay is approximately1.4 times the game read-We can use lithology crossplot to help us define ing in the Telegraph Creek Formation (composedofmatrix and particularlyto identify the presence of ~ 70 percent clay). ~gypsum, pyrite, or siderite. This could help us todetect gas that might otherwise be overlooked. Also, Water saturation calculationsrequire the usethe detection of these minerals could have explora- of shaly sand equations to compensateforclay re-tion ir,pilca>ions. Iated resistivity decreases. The type of equation

needed is one that will be applicable in both lamin-Pheimportantpoint to be mentioned regarding ated anddisperseddistributionof clay within thecrosaplotsin shaly sands is that the data interval rock. One of the better equaticmm for this purposeshould be selectedon the basis of geologic criteria. takes the following form:For example, if the purpose of the plot is to detectthe presence of one mineral, say gypsum,then itwould be unwise to include the Bowdoin Member with Sw=a Rw(l-V~h) {JT

%2+ 4 @em Vshpart of the overlyingNiobrara Formation. We 2 @em Rsh }a Rfi::t (1 - Vsh)- ~would prefer to deal with as few variables at atime as possible. . ..* (1

In designing optimum crossplot for detection whereof gypsum, pyrite, and siderite,we need to takebest advantage of log response. Using f8na- fisa a = formation factor coefficientversus @na - @da versus @sa - k Plots we should % = formationwater resistivitybe able to detect even small volumes of these min- Vsh = volume clayerals (seeTable 4). @e = effectiveporositym = cementationexponent

An advantage of these plots over conventional Rsh = res.istivityclaytype plots is that they allow us to detect the min- Rt = true formation resistivityerals of interestwhile at the same time compensatingfor gas and clay response., It has been variously referred to as TotalShaleRelation,16 ItTotalShale Equation Ja and Modified.

The lithologyplots described ative lend them- SimandouxEquetion.12selves to computerprocessing. It should proveuseful to plot depth, frequency,VclaY from the Application of the Total Shale Relation can wegamma, and Rt on the z-axis. These plots will be demonstratedby rewriting the equation;utilized in a continuationof this research.

Sxo=[J I I

a Rmf(l-vsh) W2 ~. 1QUANTITATIVELOG CALCULATIONS 2 @em Reh a ~~Rxom(l-Vsh)-ZEffective porosity is best calculated fzom tb.a (1density log by using equation 10 and proper assump- . . . .

tione for matrix and fluid. Porositiesobtained in wherethis manner,are in agreement with core porosity inthe Eagle. Bowdoin Gore porosity tends to run sX. = flushed zone water saturationslightly h!.gherthan density porosity. This iSthought to be due to artificial fracturingand de- &f = reSiStivitymud filtrateRxo = zesistivity flushed zonecrepitationof the co re which accompaniesdehydrationof clays. The core actually increases in volume un- Flushed zone saturations (Sxo)average 80-90percentless plastic sleeve coring tr.chniquesare employed. in the Eagle and Bowdoin using this equation. InThis phenomenon also has a pronounced effect upon comparison,Archie equation alone gives saturationspermeabilitymeasurements. over 200 percent.

Volume clay can be calculated by using a combin- Saturation.calculationsforthe 0296 well (Fig-ation of density.andneutron. Two techniques usinghand carried calculatorshave been recently published. ure 3 and 4) using the above methods give thefollowingsaturations:One technique makes cse of a geometricalneutron-density crossplot.20 The other defines effective Eagle 541- 5508 ~= 67%porosity in terms of both neutron and densitytand Bowdoin 1,380-1,388SW= 67%

,...


6/14

Table 6 summarizesthe assumptions used in makingthese calculations. Both zones calculate over 100percent & using Saraband computed analysis. The67 percent seems reasonablebecause the zones pro-duce both gas and water.

The Waxman-smiteequationlhillbeappliedin thefuture when cation exchange data become available.CONCLUSIONS

Conventionallog interpretationtechniques havebeefiineffective in detecting gas in the Bcwdoin andEagle sectionsof the Bowdoin Dome Field.~ Effective interpretationsystem will take

best advantage of geologic data and tool reepcnse.we suggest use of the,neutron sonic overlay in con-junctionwith computer generated lithology croseplots.

Effort should be made to quantify reservoirparameters. Methods for interpretingwater satura-tion, volume clay, and poroeity as preeented in thiereport should be utilized to maximize production, re-duce operating axpenses, reduce completion costs, orhelp eliminateunnecessarywell completions.NOMENCLATURE

a =A=Cp =d=;h ~m=~.ml uN=

, P=

q-&lay =Rild =Rmf =Rsh =Rt =~.Rxo =Sw =Sxo =%v=veh =~nAt n

Atma =Pa =Pb =

(Pb)clay=Pf =

formation factor coefficientatomic weightsonic compaction correction factorSgraim = grain density, g/ccHydrogen Indexmolecularthermalizingcoefficientcementationexponentmolacularweightslope for hydrocarboncorrectionAvogadzo*snumber, 6.025 x 1023dissolve~ eolids content of filtrate,ppm x 10 6dispersed ehale fractionresistivityclay, ohm-mreeistivitydeep induction,ohm-mresistivitymud filtrate,ohm-m%~ay = reeietivity ehale, ohm-mtrue formation reslstivity,ohm-mformation watcz resistivity,ohm-mresistivity flushed zone, ohm-mwater saturation,fraction of porevolumewater saturation flushed zone, fractionof pore volume ..formationtemperatureThermalizing IndexVolumevc~ay = clay content, fractionof bulkvolumeatomic numberacoustic travel time from the soniclog, peec/ftacoustic travel time in rock matrix,wec/ftapparent density fromg/ccdensity tool reeponseg/ccdensity tool responseclay g/ccdensity tool response

density 109,to the f~rmationto the formationto fluid invicinity of well bore, 9/cc

Ph = density tool responee to hydrocarbog/cc

Pmz = density tool response to rock matrig /cc

Pmf = density tool reeponseto mud filtrag/ccZ = ~eutron capture crose section,barn@da ~ apparent density porosity

(@da)cly = apparent density porosity clay$e = effective poroeity(@e)cla y = effective poroeity clayPJIs= limestone porosity

@na= apparent neutron porosity(Ona)clay = apparent neutron porosity clay(@na)m = apparent neutron porosity rock matri(@na)mf = correction for invaded filtrate =p~f (1 -P)

(@sa)=apparent conic porosityACKNOWLEDGEMENT

This study wa,sfunded by the DepartmentofEnergy under the Western Gas Sands Project. Thanare due CER.Corporationmanagement and geologistsfor encouragement to engage in this research. Wewould also like to thank J.J.C. Paine for participating in the Western Gas Sands Coring and LogginProgram, the U.S. Geological Survey personnel in-volved in the Western Gas Sands Projectt andKansae Nebraska Natural Gas Company. .-PREFERENCES1.

2.

3.

4.

5.

6.

7.

8.

9.

Bettis, F., *lGasDetection in Sands of HighSilt-Clay Content in the Cook Inlet Area;Trans. SPWLA SeventeenthAnnual Logging Sym-pcsium, 1976.CamPent E.B., IiWellLog AnalYeis in the Cre-taceous Gas Sands of Northern Montana, MontGeological Society 22nd Publication,1975.cannon, D.E,, llEvaluationof ShalY Sande witLow Deliverability,The Journal of CanadianPetroleum Technology,January-March,1975.Clavier, C., Heim, A., and Scala, C., Effecof Pyrite on Resietivity and Other LOggin9Measurements,TranS. SPWLA SeventeenthAnnLogging symposiS976.Cutrese, W.G., An Empirical Approach to LogInterpretationin the Viking Sand of East Cetral Alberta, Trans. SPWLA FifteenthAnnualLogging Symposium, 1974.Daweon-Grove,G.E., ShallowGaer How to LacEaSilY Missed Pay Sands, World Oil, SePtemb1977. Garb, F.A., nNeutronand Neutron-DensitY~9Analysis Procedures,PetrolWm 13n9ineerpMS1?78Gautier, D.L., MajorMineral Constituents oSelected Paine Well Samples,written commucation, 1979.Gearhart-Owen Industries,Inc., Formation Evuation Data Han-ok, 1975.


7/14

,., ,

10. ~enq, Kc., vGasDetection in the EXtremelY 16. Schlumberger,I@., Leg Interpretation,VoluMe IShaly Bowdoin Formation of Northern Montana, Principles, 1972.Unpublishedwritten communication,1978. 17. Schultz, L., w ~ ~ xed-~ a yer Cky h the ierre

11. Henry, K.C., Leg Evaluation in the Bowdoin Dome Shale and Equivalent Rocks, Northern GreatField, Unpublishedwritten conununication,1977. Plains Region, U.S. Geological Survey Pro-fessional Paper L064-A, 1978.

12. Johnson, W.L., Linke, W.A., Some PracticalApplicationsto Improve Formatim Evaluation 1s. Starkey, H.C., Blackmon, P.D., Rice, D.D.,of Sandstones in the MacKenzie lmlta, Trans., MineralogicalAnalysis of Drill Core SamplesSPWLA Nineteenth Annual Logging symposi~978. from klidlandsGas CorporationWells -- Federal0370 No. 1 and Federal 2962 No. 1, Phillips

i2. l@walchuk,H., Coats, G., and Wells, L., The County, Montana, U.S. Geological Survey Open-Evaluation of Very Shaly Formations in Canada File Report 78-1001, 1978.Using a SystematicApproach, Trane., SPWLAFifteenth Annual Logging Sympo= 1974. 19. Waxman, M.H., Smits, L.J.M., Electrical Con-ductivitiesin Oil-Bearingshaly Sands, Trans.

14. Kukal, G.C., ~lEsti~tionOf Neutron ~g esponse SPE 42nd Annual Fall Meeting, 1967. ,Using ThermallzingIndex and capture CrossSection, in preparation. 20. WU, C.H.? Krug, ~., Density-NeutronCrossplotAnalysie for Shaly Gas Sands Using Hand-carried

15. Rice, D.D., Shurr, G.W., Potentialfor Major Calculators,The Log Analyst, volume 19 #4,Natural Gas Resources in Shallow, LQW Perme- 1978. See also Erratum,The Log Analyst,ability Reservoirsof the Northern Great Plains, Volume 19 #6, 1978.Montana Geological Society 24th Annual Confer-ence, 1978.

Tabl e 1Mneral composi t i onbowdoi nmcmbercarl i l e shaleMidlands370 #1 Midlanda2962#1(17Sarnplea) (13Samples)Average AverageTotal TotalAverage ClaySize Average ClaySizeTotal Range Fraction Total Range FractionSample(%) (%) Only(%) Sample(%) (%) Only(%)

QuartzIlliteXsolinitePyriteFeldsparGypsumChloriteCalcitemlomiteMontmorilloniteMixedlayerclays

Total

52.018.011.07.03.52.53.02.00.50.50.0

100.0

45-6515-257-153-153- 70- 7

30-150..70- 3

25.3 49.548.2 18.016.8 11.00.0 6.51.0 3.00.0 3.54.3 3.00.0 1.50.0 1.01.5 1.02.9 _ 2.0

100.0 100.0

40-65 26.915-25 42.97-15 19.03-15 0.2

3 0.00-1o 0.23- 7 3.20-1o 0.00- 7 0.00- 3 2.20- 7 5.4

100.0

91


8/14

L

,

Tabl e 2Neutron response to the conmonel ementsThermal Neutron1 Capture Crossz T Section (Barns)

Hydrogen 1 1.000 0.33Carbon 6 0.167 0.0034oxygen 8 0.125 0.0002Sodium 11 0.091 0.400Magnesium 12 0.083 0.0625Aluminum 13 0.077 0.232Silicon 14 0.071 0.1638sulfur 16 0.063 0.49Potassium 19 0.053 2.152Calcium 20 0.050 0.455Iron 26 0.038 2.514

Tabl e 3Neutr on response to vari ous mneral s

Mineral Foxmula K1.hWOlecules/ccM d %h (XN) TI HI zWater (pure)GypsumKaoliniteChloriteWOntmorilloniteIlliteGlauconiteMuscwiteBiotite001omiteCalciteQuartzBideriteWa PlagicalaseMethanePyrite

HzOCaSO~ . 2H20iilqSih 010 (OH)O(Mg;Al,e)IZ(S1,A2)E OZO(OH)16A2u Sia OZO (OH)4 - n HzOK AIs Si7 OZII(OK)IIKz(Fe,Al#Wg) (Si,Al) ozo (OW I+s n H20K A12 (S13Al) 010 (OH)z2C(Fe,g,Al)[Si,Al)Iolo(W 2ca63g(C03)2tacoSiozFmzC03NaAl s:308(S00psia- 75?F)C334Fe S2

18.02172.17516.32

1,221.6673S.64758.62S31.51398.31465.011S4.22100.0969.OS171.70262.1316.04119.98

1.002.322.632.712.352.842.3o2.932.902.852.712.653.882.660.035.o6

2.124.S610.s429.9110.007.9410.043.7B4.021.220.590.320.621.394.170,16

.11s

.066

.055

.049

.032

.030

.028

.028

.025

.019

.016

.014

.014

.014,007.007

8.3104.6103.S903.4202.2402.~go1.960l,9\~1.7601.3201.1301.0000.9S60.9860.4930.4S6

1.000.480.370.320.17(.13,.150.130.11.00.00.00.00.00.06.00

22.OB19.4013.0618.728.1039.9020.5517.3028.034.7s7.48


9/14

Tabl e 4Summary of porosi ty l og response to vari ous mneral s

Water (pure)GypsumYaoliniteChloriteWontmmllkzniteIlliteGlauconitemuacoviteBiotiteColorAtecalciteQuartzSideriteNa PlagioclasePyrite

ApparentPorositywith 108Zmpurity of 142neraln 4 Semi-CompactedQuartzSan6stoneTI E d grain !% At Having#e - 159

Differencein Xesmnse for 10*Im urityof Mineral~n a Semi-compacteduarts andstoneHaving kle - 15$afna @da f%l fin- @.?afP..) !& - @da(P.u. l%a- @da(P.c . )

8.314.613.893.422,242.091.961.961.761.321.131.000.990.99

U.49

22.0819.4013.061s.s728.1039.9020.5517.3028.934.707.484.366s.516.9988.70

1.002,322,632.712.352.842.302,Q32.902.852.712.653.8s2.66S.06

1.11 207.0 ---2.37 53.0 .1872.6a n* .1632.74 A* .17B2.35 8* .1642.81 8* ..19**4.30 A* .1612.91 A* .1612.84 A* ..18*O2.85 44.0 >.42.:1 46.5 ,1522.65 55.1 ---3.72 ? *.19**2.64 ? .15

4.91 67.o =.19**

---.164.148.145.165.142.168.137.140.140.147---.095.15

.034

---.149=.18*.17..17=.17=.17=.17=.17.143.145.....14?..15?

.158

---3.s

. .!3.4= 0.s. -0,6= 2.0* +,9. -0.9= 1.0

1.10.7-..

= 5.00,0

* 3.2

.. .2.33.53.30.0

= 4.8-0.72.4

. 4.01.40,5---

* 9.5

*15.6

..--1.5. 3.2= 2.5. 0.5. 2.8* 0.2= 3.3= 3.00.3-0.2..-

. 4.5* 0.012.4

qAnisotrOpic- Plateyminerals,At dependinglargelyupondegreef compact ion and foliationq.z ~Or=e~tiO~~p@l~aaadttl~~oTIcorrections

Ref i nement of grai n densi t y apparent matri x densi ty (Pma)

%xain %n %a in %ALL MINSWS%ra in Ih.a ALL MINEPALSCUtY-MINESA3.9 CLAY MINSRALB OTN8R TILAN3VTALCCK OTRSR TNANTOTAL RGCK ONLY ONLY CLAY MINER4LS C~Y MINERALS .oRMATION SOURCEOF DATACommercialgrain density 2.6s0 2.677measurements50 samples Range%wdc in 0296well, 1,351 - 1,4451 2.78- 2.60

X-ray analysis,17 side-wall cores 0370 well,1,70s- 2.76o 2.756 2.737 2.7411,S40.5; 13 side- 2.772 2.765. . .wall cores 2962 wall, .1,406- 1,5331J Break- ,. .:..down into mineral con- . .stituantsall aiavesizes. G3es not in- ..elude organicmatter.

Commercialgrain density 2.7o4 2.702measurements67 ssmples S6nge0296well, 554 - 5781, 2.75- 2.65Eagle 835 - 891{. *

X-ray analyeis,3 sidewallcores 2962well, 573 - 717-J 2.699 2.697 2.708 2.7112 sidewallcoraa 0370 well, 2.695 2.691846- 847*I Bzeakdownintomineralconstituentsallsieve aisee. 0rg6nicmatterremovedia not aignificant

Nicvoacopicpoint count, 3 2.703 2.697selected0296well coras,562 .. 8471, in conjunctionwith clay size fractionX-ray analyais. -


10/14

Tabl e 6Assumpti ons used i n quanti tati vecal cul ati onsParameter Eagl,?- Bowdoin ...% l.om .635SlmTfm 60F (15.6oC) 750F (23,90c)&lay 3ti 2Gm(g~a)clay .55 . .55(@e)clay .20 .20(@na)m +.02 greater than fdl~ +.o2 greater than @ls(@n)mf 1.0 1.0P .003 pplnx 10-6 .003 ppm x 10-6Pf .95 ~/cc .95 g/cc Pm@ 2.70 g/cc 2.68g,cc(Pb)clay 2.71 g/cc 2.74 g/cc(@da)clay -.017 -.035Pmf 1.11 g/cc 1.11 g/ccph .03 g/cc .03 g/ccSxo .85 .85ml .65 .65


11/14

... ,

33N

32N

31N

SON

29N30E28N

) ) Bowdoi nDomeField

1 1-f-hhillipsLLIJR) i%

J. J.C.P8ineMidlandsFed1.0296

VeUey1 I I I I I I31E 32E 33E 24E 35E 36E

Fi g. 1 - I ndexmap of Bowdoi nDome Field, Nort h Central Montana.

Bearpaw Shalet

Claggett Shale Pierre Shak

TelegraphreekFm.I

I NiobreraFm.Carlile Fm.Bowdoin Mbr.

I Salle Pourche ehtde

Fi g. 2- Upper Cretaceousstr ati grasecti on i n vi ci ni ty of Bowdoi nDome,North Central Montana.


12/14

GAMMA RAYo API 200

)

500

600

[ RESISTIVIIY, OHMS mz/m

Il--RILD

I SANDSTONEPOROSITY60 45 30 15 0

-d t_-11.Fi g. 3- Mdl ands gas federal 1- 0296 composi te l og of Upper Eagl e sandstone.

-.


13/14

I . ..*

I ~ M1sTlTyOHMsmmsmDsmNEOROsTy II--3-I1- [ -1 l--

}icN-H 1- ( -i l-.

,Rx()

DENSITY

Fi g. 4- Mdl ands gas federal 1- 0296 composi te l cg of Bowdoi nMBI ?.of Carl i l e FM

.,


14/14

.... . ..10 .20Kxl .30 .40 .60 .60 .70 ,80 .90 1.00i I I I I I I I I

fl\90 ., water

SO /

I70 /60 Gypunl /HI , Kielinlk

Chlotito40 .

Mo~trnorMonlk30 - Kaullnl@Qlluccmita

Museoviie /Iulte I } \\\ \Chlo?lk

m - BlotltaMethuIe \w

II II II II II II1 2 3

Fi g. 5 -

4 6 6 7 8 9Thermelizing Index (Quartz Standerd)

Neutron response to thqrmali zers.

,-----

det gas y eval yac-arenas super

Documents