泥岩压实研究中有机质导致声波时差异常的定量校正方法
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摘要
高丰度有机质导致的声波时差异常高值不能客观反映地层孔隙度的变化,定量研究有机质对压实曲线的影响才能减小压实研究结果的不确定性。从泥岩压实研究的原理出发,构建考虑干酪根的岩石等效体积模型,提出有机质引起声波时差增量的校正公式;以鄂尔多斯盆地南部镇泾地区为例,讨论压实曲线有机质校正方法的实用性及可靠性。结果表明:烃源岩层段高丰度有机质往往造成压实规律的较大误差,压实研究中应当消除有机质对声波时差的影响;镇泾地区泥岩压实曲线经过校正后,正常压实趋势线斜率减小约30%~55%;长7段底部页岩欠压实幅度显著降低,最大埋深时期的剩余压力约为3~5 MPa,相比于校正前降低5~8 MPa,反映出以往研究可能过高地估计了长7段古超压的幅度;利用校正后声波时差计算的泥岩孔隙度与实测孔隙度吻合性较好,且计算的流体压力与数值模拟结果一致,证实提出的定量校正方法能够有效地消除研究区有机质造成的声波时差异常,可作为鄂尔多斯盆地及其他地区压实研究的借鉴。
Abnormally high values in the sonic data of the source rocks cannot objectively reflect normal variations in porosity of the study of mudstone compaction. In order to eliminate the uncertainty of compaction measurements,quantitative corrections need to be introduced. In this paper,by using the principle of mudstone compaction,the organic rich rocks are divided into four parts by modifying the rock volume model of Wyllie equation: rock matrix,kerogen,pore and pore fluid. A correction formula for acoustic time increment caused by organic matter is derived. Taking Zhenjing area as an example,using the ωTOCand measured porosity data in Zhenjing area,the practicability and reliability of compaction correction method for organic matter are discussed. The results show that the high content kerogen leads to markedly large errors in the compaction results,therefore reducing these errors in the sonic data becomes very important. After applying the correction,the compaction coefficient decreases by 30%-55%,and the uncompacted belt amplitude drops significantly. The mud overpressure of C7 shale calculated based on the equilibrium depth method is 3-5 MPa,comparable to the results of numerical basin modeling. The pressure values are 5-8MPa smaller than that of without correction,indicate that previous studies may have overestimated the abnormal pressure of Yanchang Formation. Based on the Wyllie equation,the calculated porosity using the corrected sonic data is consistent with the measured porosity. The results suggest that the quantitative correction method can eliminate the abnormal sonic data due to the presence of organic matter,and can be effectively applied to other area of Ordos Basin and other basins.
Abnormally high values in the sonic data of the source rocks cannot objectively reflect normal variations in porosity of the study of mudstone compaction. In order to eliminate the uncertainty of compaction measurements,quantitative corrections need to be introduced. In this paper,by using the principle of mudstone compaction,the organic rich rocks are divided into four parts by modifying the rock volume model of Wyllie equation: rock matrix,kerogen,pore and pore fluid. A correction formula for acoustic time increment caused by organic matter is derived. Taking Zhenjing area as an example,using the ωTOCand measured porosity data in Zhenjing area,the practicability and reliability of compaction correction method for organic matter are discussed. The results show that the high content kerogen leads to markedly large errors in the compaction results,therefore reducing these errors in the sonic data becomes very important. After applying the correction,the compaction coefficient decreases by 30%-55%,and the uncompacted belt amplitude drops significantly. The mud overpressure of C7 shale calculated based on the equilibrium depth method is 3-5 MPa,comparable to the results of numerical basin modeling. The pressure values are 5-8MPa smaller than that of without correction,indicate that previous studies may have overestimated the abnormal pressure of Yanchang Formation. Based on the Wyllie equation,the calculated porosity using the corrected sonic data is consistent with the measured porosity. The results suggest that the quantitative correction method can eliminate the abnormal sonic data due to the presence of organic matter,and can be effectively applied to other area of Ordos Basin and other basins.
引文
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(1)罗晓容.陇东地区延长组6~8段石油运聚规律及成藏特征研究.中国科学院地质与地球物理研究所研究报告,2006.
[2]李明诚.在油气初次运移研究中压实曲线的应用[J].地球科学,1986,11(3):309-314.LI Mingcheng.Application of compaction curve in researching primary migration[J].Earth Science,1986,11(3):309-314.
[3]MAGARA K.Compaction and fluid migration practical petroleum geology[M].Amsterdam:Elsevier Scientific Publishing Company,1978.
[4]罗群.泥岩压实动态分析法定量评价石油初次运移[J].石油勘探与开发,2002,29(2):71-74.LUO Qun.Quantitatively evaluating hydrocarbon primary migration by mudstone compaction dynamic analysis[J].Petroleum Exploration and Development,2002,29(2):71-74.
[5]付广,薛永超,杨勉.用声波时差资料确定欠压实泥岩盖层压力封闭形成时期及其意义[J].石油地球物理勘探,2000,35(5):634-640.FU Guang,XUE Yongchao,YANG Mian.Determine forming period of pressure seal for undercompacted shale cap and its meaning by using interval transit time data[J].Oil Geophysical Prospecting,2000,35(5):634-640.
[6]陈瑞银,罗晓容,陈占坤,等.鄂尔多斯盆地埋藏演化史恢复[J].石油学报,2006,27(2):43-47.CHEN Ruiyin,LUO Xiaorong,CHEN Zhankun,et al.Restoration of burial history of four periods in Ordos Basin[J].Acta Petrolei Sinica,2006,27(2):43-47.
[7]赵健.松辽盆地西斜坡泥岩地层压实规律[J].石油与天然气地质,2010,31(4):486-492.ZHAO Jian.Laws of mudstone compaction on the west slope of the Songliao Basin[J].Oil and Gas Geology,2010,31(4):486-492.
[8]彭波,邹华耀,滕长宇,等.大民屯凹陷超压的发育演化及油气运聚的动力学机制[J].中国石油大学学报(自然科学版),2013,37(6):10-16.PENG Bo,ZOU Huayao,TENG Changyu,et al.Evolution of overpressure and dynamic mechanism of hydrocarbon migration and accumulation in Damintun depression[J].Journal of China University of Petroleum(Edition of Natural Science),2013,37(6):10-16.
[9]LUO Xiaorong,WANG Zhaoming,ZHANG Liqiang,et al.Overpressure generation and evolution in a compressional tectonic setting,the southern margin of Junggar Basin,northwestern China[J].AAPG Bulletin,2007,91(8):1123-1139.
[10]张发强,王震亮,吴亚生,等.消除影响压实趋势线地质因素的方法[J].沉积学报,2002,20(2):326-331.ZHANG Faqiang,WANG Zhenliang,WU Yashen,et al.A method for eliminating geology factors of affecting compaction trend line:an example from Yinggehai Basin[J].Acta Sedimentologica Sinica,2002,20(2):326-331.
[11]范昌育,王震亮,张凤奇.库车坳陷克拉苏冲断带传递型超压的识别、计算及其主控因素[J].中国石油大学学报(自然科学版),2014,38(3):32-37.FAN Changyu,WANG Zhenliang,ZHANG Fengqi.Identification calculation and main controlling factors of overpressure transferred by fault in Kelasu thrust belt of Kuqa depression[J].Journal of China University of Petroleum(Edition of Natural Science),2014,38(3):32-37.
[12]MEYER B L,NEDERLOF M H.Identifaction of source rocks on wireline logs by density/resistivity and sonic transit time/resistivity cross plots[J].AAPG Bulletin,1984,68(2):121-129.
[13]ATHY L F.Density porosity and compaction of sedimentary rocks[J].AAPG Bulletin,1930,14(1):1-21.
[14]WYLLIE M R,GREGORY A R,GARDER G H.An experimental investigation of factors affecting elastic wave velocities in porous media[J].Geophysics,1958,23:459-493.
[15]陈曜岑.利用测井资料研究和评价生油岩[J].石油物探,1996,35(1):100-106.CHEN Yaocen.Study and evaluation of oil source using log data[J].Geophysical Prospecting for Petroleum,1996,35(1):100-106.
[16]卢龙飞,蔡进功,刘文汇,等.泥岩与沉积物中粘土矿物吸附有机质的三种赋存状态及其热稳定性[J].石油与天然气地质,2013,34(1):16-27.LU Longfei,CAI Jingong,LIU Wenhui,et al.Occurrence and thermostability of absorbed organic matter on clay minerals in mudstones and muddy sediments[J].Oil and Gas Geolgey,2013,34(1):16-27.
[17]孙波,蒋有录,石小虎,等.渤海湾盆地东濮凹陷压力演化与超压形成机制[J].中国石油大学学报(自然科学版),2013,27(2):28-35.SUN Bo,JIANG Youlu,SHI Xiaohu,et al.Pressure evolution and formation mechanism of overpressure in Dongpu depression,Bohaiwan Basin[J].Journal of China University of Petroleum(Edition of Natural Science),2013,27(2):28-35.
[18]贺君玲,邓守伟,陈文龙,等.利用测井技术评价松辽盆地南部油页岩[J].吉林大学学报,2006,36(6):909-913.HE Junling,DENG Shouwei,CHEN Wenlong,et al.Evaluation of oil shale in the southern Songliao Basin using logging techniques[J].Journal of Jilin University,2006,36(6):909-913.
[19]PASSEY Q R,CREANEY S,KULLA J B.A practical model for organic richness from porosity and resistivity logs[J].AAPG Bulletin,1990,74(12):1777-1794.
[20]TISSOT B P,WELTE D H.Petroleum formation and occurrence[M].New York:Springer-Vevlag Berlin Heidelberg,1984:131-159.
[21]张文正,杨华,李剑锋,等.论鄂尔多斯盆地长7段优质油源岩在低渗透油气成藏富集中的主导作用-强生排烃特征及机理分析[J].石油勘探与开发,2006,33(3):289-294.ZHANG Wenzheng,YANG Hua,LI Jianfeng,et al.Leading effect of high class source rock of Chang 7 in Ordos Basin on enrichment of low permeability oil gas accumulation[J].Petroleum Exploration and Development,2006,33(3):289-294.
[22]邓南涛,张枝焕,王付斌,等.鄂尔多斯盆地南部镇泾地区中生界原油地球化学特征及油源分析[J].天然气地球科学,2013,24(3):604-611.DENG Nantao,ZHANG Zhihuan,WANG Fubin,et al.Geochemical characteristics and oil source correlation of crude oils in Zhenjing area,southern Ordos Basin[J].Natural Gas Geoscience,2013,24(3):604-611.
[23]刘新社,席胜利,黄道军,等.鄂尔多斯盆地中生界石油二次运移动力条件[J].石油勘探与开发,2008,35(2):143-147.LIU Xinshe,XI Shenli,HUANG Daojun,et al.Dynamic conditions of Mesozoic petroleum secondary migration,Ordos Basin[J].Petroleum Exploration and Development,2008,35(2):143-147.
[24]丁晓琪,张哨楠,易超,等.鄂尔多斯盆地镇泾地区中生界油气二次运移动力研究[J].天然气地球科学,2011,22(1):66-72.DING Xiaoqi,ZHANG Shaonan,YI Chao,et al.Dynamic of Mesozoic hydrocarbon secondary migration in Zhenjing Oilfield,south western Ordos Basin[J].Natural Gas Geoscience,2011,22(1):66-72.
[25]邓虎成,周文.镇泾地区三叠系延长组油气成藏条件研究[J].石油天然气学报,2008,30(5):11-17.DENG Hucheng,ZHOU Wen.Research on Hydrocarbon accumulation conditions of Triassic Yanchang formation in Zhenjing Area[J].Journal of Oil and Gas Technology,2008,30(5):11-17.
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