A New Method for Hydrocarbon Loss Recovering of Rock-Eval Pyrolysis

Dec. 2004J. China Univ. of Mining &. Tech. (English Edition)Vol. 14 No. 2A New Method for Hydrocarbon LossRecovering of Rock- Eval PyrolysisWU Xin-song(吴欣松)', WANG Yan -bin(王延斌)”, ZOU Xiao- yong(邹小勇)”(1. University of Petroleum , Beijing 102249，China ;2. School of Resources and Safety Engineering, CUMT, Beiing 100083, China ;3. Tarim Oilfields Company , Kuler, Xinjiang 841000， China)Abstract: How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock Evalpyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factorscausing the bydrocarbon loss. Aiming at this problem, a new method named critical point analysis is put forward inthis paper. The first step of the method is to find the critical point by drawing the scatterplot of hydrocarboncontents versus the ratio of the light component of with the heavy component of ;And the second step is to calculatethe recovering cofficient by contrasting the pyrolysis parameters at the critical point of different sample types. Thimethod is not only been explained reasonably theoretically ,but also has got a good application effect in Huanghuadepression.Key words : Geochemistry; Reservoir evaluation ; Rock- Eval pyrolysisCLC number: TE 132Document code: AArticle ID: 1006- 1266(2004 )02-0200-04Problems Existed in Hydrocarbon Lossreservoir and evaluate the physical properties of theRecovering at Presentcrude oil， which will play an important role inrecognizing water and oil layer at exploration stageThe technology of reservoir geochemistryand irwatered-out oil layer evaluation atlogging was developed from oil/ gas resource rockdevelopment stage. The basic procedure is 1 ) toevaluation'l in late 1980s and now it is one of therecover effectively the hydrocarbon loss of rockfast methods to evaluate the oil/ gas reservoir in site.cuttings in well drilling，2) to calculate porosity byFrom late :1980s to early 1990s， the mainusing rock cutting weight loss data， and 3) tcgeochemistry loggers used in China were DH-910calculate the oil saturation based on porosity andand OSA. Using these logging instruments, we cantotal hydrocarbon content data.acquire pyrolysis parameters including So，S, andIn the process of oil saturation calculation usingS2 called three- peak pyrolysis data[2]. At present ,total hydrocarbon content (ST), a very critical stepthe geochemistry logger popularized in Chinais to recover the hydrocarbon loss of rock cuttings asincludes YQ serials made in Haicheng， Liaoningaccurately as possible. However, there are manyprovince and OG-2000 made by Luneng Group infactors influencing on hydrocarbon loss of rockShandong province，which can offer five parameterscuttings, such as type of drill bit, depth of oil pool,called five peak pyrolysis data including So, S, Ssn，physical properties of crude oil, and the geophysicalS22，and Sa353].中国煤化工By using pyrolysis parameters and weight lossYHC N M H Grecovering， three maindata of rock cuttings pyrolysis in site， we canmethods are often used by predecessors. The first iscalculate the porosity and oil saturation of thethe single-factor plate correction method. Its basicReceived date: 2004 -05- 12Biograph5方数据song(1969-), male, from Susong, Anbui province, associate professor, master's degree, engaged in the research oncoal geology and oil and gas geology.WU Xin-song et al.A New Method for Hydrocarbon Loss Recovering of ...201idea is to make a relevant recovering plate by using athis block, three main difficulties are encountered.certain single factor such as delayed time of rockFirst，the experience recovering coefficient of thecuttings， standing time of samples， crude oiwhole Dagang oilfield obtained by processors leadsphysical properties4. The main shortcoming of thisto a lower oil saturation interpretation， whichmethod is that it is too complicated to be used itmeans that the recovering coefficient is not suitablepractice. The second method is called experiencefor the study fault block; Second, the loss of heavycoefficient recovering which is used to determine anhydrocarbon (S23) of rock cuttings can not beexperience coefficient based on numerous statisticsignored because of the bad cementation of theof depths of pay zones， geophysical properties ofreservoir and so the second method mentioned abovereservoir，and physical properties of the crude oil[5].can not be used; Third, there is no correspondingThis method is good at exploration stage. When it is .analysis data between core samples and rockused in a certain developed fault block， it will .cuttings，making it not possible to directly get the .produce big errors because of the geologicalrecovering coefficient.particularity compared with the whole oil field. TheIn view of existing situation， the authors ofthird method often used in practice is calledthis paper put forward a new method named criticalcorrelation analysisto， which is based on theanalysis from a totally different angle. the newsupposition that 1) there is no loss of S22+S2s， andmethod determines the recovering coefficients based2) the loss of Si， Szand S22 is recovered by usingon the ratio R= (S21+S22)/(S22+ Sz3)，the heavythe relevant relationship between S，S21, S22 andhydrocarbon components (S1+ S2)，and the lightS23. Usually， this method is only appropriate forhydrocarbon components (S22+S23) .the reservoirs with low porosity and low2 Critical Point Analysispermeability. .The research area is located in a fault block of2.1 Determination of critical pointsBeidagang oilfield， Huanghua depression. TheIn order to determine the critical point， theobjective is to evaluate the watered -out oil layers byscatterplot of S1+S21 and S22+ S2s versus the ratio Rusing pyrolysis geochemistry logging data of rockshould be drawn by using the pyrolysis parameterscuttings and then to lay a foundation for choosingof core samples and rock cuttings， respectively.perforation zones in the fill wells. In this faultGenerally, there is an obvious inflexion on the plotblock，there are 5 wells having been geochemicallycalled the critical point. On the left of this point, Ilogged，but only one of which， well G1，hasrises with the increase of Si+S21 and S2+ Sxs; Whilegeochemical logging data of cores while the otherson the right, R keeps a constant base value (Fig.are rock cuttings. The first barrel of core was taken1).from1448.0mto1496.5mwithbothfootage.and core length of 8. 5 m which means the yield.51.5ratio is 100%. The other three barrels of cores arex 1.0f09100.5conventionally cored with total footage of 19. 7 m .0 5.0 10.0 15.0 20.0 25.05.0 10.0 15.0 20.0 25.0and a core length of 16.4 m (yield ratio 83. 0%).S.+S,/(mg*g^)S2+Sx2/(mg.g")The pay zones are Minghuazhen and Guantao(a) Pyrolysis data fom core samplesFormation，upper Tertiary system. The geophysical中国煤化工’characteristic of the reservoir is high porous and:THCNMHGhigh permeability because of its bad cementation.0.3 prThe mean porosity is about 33%- 37%， the depthofthepoolisabout1330mto2000mandtheS.+S2/(mg*g*)S2+Sr/(mg*g')() Pyrolysis data from rock cuingsdensity of方数搪oil, about 0. 91- -0. 93 g/cm'.r1g.1 Scatter plot ot pyrolysis parametersDuring the study of hydrocarbon recovering in202J. China Univ. of Mining &. Tech. (English Edition)Vol. 14 No. 2From the scatterplot, we can also find that, onequals 1. 67(Table 1).the right of the critical point, the base values of R ofDuring the process of determining the coveringdifferent samples are obviously different. The valuecoefficients, it is a very important step to examineof the core samples is 1. 00 and that of the rockhe rationality of the results because there acuttings is 0. 93, which is caused by different loss ofinfluences created by artificial factors in a certainboth light and heavy hydrocarbons. Because the lossdegree. Let Q be the content of light hydrocarbonof the light hydrocarbons component is alwaysof the core sample，and Q2 be the content of heavybigger than the heavy one， the base value of R ofhydrocarbon，R be the ratio; correspondingly， letthe rock cuttings is always smaller than that of coreQ' be the content of light hydrocarbon of the rocksamples (Table 1).cutting，and Q'2 be the content (heavyhydrocarbon，and R' the ratio. According to theTable 1 Pyrolysis parameters comparing betweencore and rock cuttings samplesdefinition of recovering coefficients， we have K: =Value of eritical Value of critialQi/Q，K:=Q2/Q'2， R=Q/Qz, and R'=Q'i/Parameterspoint fromRatioQ'2. From these formulas, it can be deduced ascore samplesrock cuttingsS+ S2(mg/g)7.03.91. 79R/R'=K)/K2.(1)S22+S23(mg/g)4.21.67From equation (1)， we can simply judge theR based value on the1.000.931.07rationality of the critical point, that is, if the ratioright of critical pointofK:toK2isnearlythesameasthatofRtoR'，The geological meaning of critical point is that,then, the critical points you determined are correct.in the same pay zone of a certain fault block， whenFrom the former example, the ratio of K: to K2 isthe physical properties of crude oil are nearly the1.073，andtheratioofRtoR'is1.075，sothesame，there is a sudden change of R between thetwo values are roughly the same.bearing movable oil and the reservoir without3 Practical Application and Effectmovable oil, which means that the critical point canAnalysisbe used to judge whether the reservoir bearingmovable oil or notBased on the recovering coefficients acquired2.2 Determination of recovering coefficientsfromcritical point analyzsis， this study hasBy simply comparing the critical point values ofevaluated the watered- out oil-bearing layers of 5different samples，the recovering coefficients can bewells in the objectivefault block by usingobtained. In fact ，the ratio of the critical point valuegeochemistry logging data of rock cuttings. Table 2of the core samples to that of the rock cuttings isshows the results of three layers from 3 differentjust the coefficient. So the coefficient of the lightwells，with two of them having the oil test resulthydrocarbon content (K|) equals 1. 79，and theand one of them having core analysis data.coefficient of the weight hydrocarbon content (K?)Table 2 Watered-out oil layer evaluation results in a fault block in Huanghua DepressionResults ofWellSo/No.Depth interval(mg.g-1) %geochemistry loggingwell loggingOil-test resultinterpretationMiddleWeakCrude oil 10 m3 andG2 1 638.5-1 642.2 23.80 29. 3524. 30watered- -out zonewater 5 m3 per dayOil layer,中国煤化工de oil 50 m3 ,natural gasG3 2 049.8-2 053.5 30.60 22.25 48. 34watered- ouCN MH GO0m2 and water 1m3 per day13.80 27. 4315. 92covee from rok cuting)G1 510.5-1 512.0Dry- layer15.50 27. 1716. 50watered-out(note: core sample analysis)1) For layer No. 22 of well G2，the depth23.80 mg/g, the porosity calculated by weight lossinterval is方努数据642. 2 m, the total hydrocarbonmethod is 29. 35%， and the oil saturationcontent ST after recovering of the rock cutting isinterpreted by geochemical logging is 24. 35%.WU Xin-song et al.A New Method for Hydrocarbon Loss Recovering of ...203Meanwhile, the gas chromatograph of side wall coreinterval is 1 510. 5-1 512. 0 m，the totalsample displays the characters of a middle watered-hydrocarbon content ST after recovering of the rockout layer. So this layer is synthetically interpretedcutting is 15. 92 mg/g，the porosity calculated byto be middle watered- out and produced oil 10 m'/dweight loss method is 27. 43%，and the oiland water 5 m*/d, witha watercontent of 33. 0%.saturation interpreted by geochemistry logging is2) Fof layer No. 40 of well G3，the depth17.21%. Correspondingly， the total hydrocarboninterval is 2 049. 8- -2 053. 5 m，the totalcontent ST of the core sample is 15. 5 mg/g, theporosity calculated by weight loss method icutting is 30. 60 mg/g，the porosity calculated by27.17%，and the oil saturation interpreted byweight loss method is 22. 25%， and the oilgeochemical logging is 16. 50%. These two resultssaturation interpreted by geochemical logging is 48.are very close. The gas chromatograph of the core .34%. Meanwhile， the gas chromatograph of sidesample shows the character of a water layer.wall core sample displays the characters of a typicalFrom the above examples, we can deduce thatoil layer. So this layer is synthetically interpreted toit is reliable in a high level to evaluate the watered-. be a oil layer with no watering out, which produceout layer by using rock cutting geochemical loggingoil 50 m'/d, water 1 m*/d, and natural gas 14 000data，but it must be on the premise of an accuratem3/d.hydrocarbon recovering.3) For layer No. 14 of well G1，the depth自1060 3 69 1215182124273033363942454803 6912151821242730333639424548-103 6 912151821242303336394245481/min! /mint/min(a)b)(C) .Fig.2 Saturated hydrocarbon chromatogram of watered- out oil layercertain oil field, in order to determine critical points4 Concl usionsof the core samples， only one relative systematic1 ) The critical point analysis method iscored well is enough; But for rock cuttings， theeffective in recovering the hydrocarbon loss of rockwells are needed to be determined one by onecuttings，and the critical step is rational inbecause the drilling environment is different. Indetermining the location of the critical points fromaddition，enough analyses of samples are necessarythe scatterplot of pyrolysis parameters.in order to ensure the reliability of critical point2) In the same pay zone of similar depth of aanalysis.References[1] Espitalie J, Deroo G. Marquis F. ? Rock- Eval Pyrolyseis and its applications (Part Two)[J]. Oil &. Gas Science andTechnology, 1985, 40(6) :755-784.[2]潘志清,梅博文,苏秀芳,等.储层含油性热解评价方法[J].中国煤化工):353-355.[3]朱扬明，梅博文,潘志清.储岩热解技术在石油勘探中的应用1HC N MH G(4)9295.[4]丁莲花,刘志勤,翟庆龙.岩石热解地球化学录井[M].东营:石油大子出放任.1993.[5]大港油田科技丛书编委会.录井技术[M].北京:石油工业出版社,1999:130-132.[6]郎东升,郭树生.热解分析方法在松辽盆地北部储层评价中的应用[J].石油实验地质,1996,18<4):441-447.