页岩油气甜点识别的综合评价方法
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摘要
页岩油气的高效开发需要最大程度地识别出甜点所在.为了将地质甜点与工程甜点有效融合来识别和评价页岩油气甜点,在总结龙马溪组勘探成功经验的基础上,以美国某盆地A组页岩层为例,提出"甜点体"的概念,其界定为体积压裂的对象.通过A组页岩储层纵向差异化研究,以及总有机碳(TOC)数值、脆性指数等地球物理预测方法的应用,结合甜点体非均质性变化对水平井产量影响的分析,建立了页岩油气甜点体的识别和综合评价方法,即五步法:垂向评级、平面划区、体积雕刻、差异压裂、油藏定调.研究结果表明:龙马溪组的TOC在2%~8%,含气量在1.7~4.8m~3/t,脆性矿物质量分数在20%~70%,"甜点"划分的门槛值应是TOC大于3%,含气量大于2m~3/t,脆性矿物质量分数大于40%.基于不同区域3个参数门槛值不同,该方法有利于区块内的勘探开发及钻完井技术适用性调整.
High-efficiency development of shale oil and shale gas mostly depends on sweet spot identification.This paper aims to identify and evaluate sweet spot through integrating assessment parameters of geological and engineering sweet spot.Based on summarizing the successful exploration experiences of Longmaxi formation in Yangtze area,and a case study of shale beds of A formation in certain American basin,the concept of sweet spot volume,which is defined as the object of volume fracturing,was put forward.By applying geophysical prediction method of total organic carbon(TOC)level and brittleness index,a five-step shale oil and gas sweet spot identification and comprehensive evaluation workflow was proposed on the basis of vertical differentiated study of shale reservoir characteristics,and the impact analysis of heterogeneity on production difference of sweet spot.The first step is to vertically study and classify reservoirs and ensure which layer is sweet spot;the second step is to determinate the planar partition of the target shale according to geophysical prediction results and geological parameters;the third step is to describe and understand characteristics of sweet spot volume through geological parameters and engineering parameters;the forth step is to optimize fracturing design for every horizontal well or one pad by level of understanding for sweet spot volume character-istics;and the last step is to judge development design of oil and gas field by production data analysis.The results show that:the TOC of Longmaxi formation is within 2%—8%,the shale gas content is among 1.7—4.8m~3/t,and the mass fraction of brittle minerals ranges from 20%to 70%.The threshold value for sweet spot identification is that the TOC should be larger than3%,with the shale gas content bigger than 2 m~3/t and the mass fraction of brittle minerals higher than 40%.Because of different threshold value of three parameters in different areas,this workflow is favorable for applicability adjustment of shale oil and shale gas exploration,development,drilling and completion techniques.
High-efficiency development of shale oil and shale gas mostly depends on sweet spot identification.This paper aims to identify and evaluate sweet spot through integrating assessment parameters of geological and engineering sweet spot.Based on summarizing the successful exploration experiences of Longmaxi formation in Yangtze area,and a case study of shale beds of A formation in certain American basin,the concept of sweet spot volume,which is defined as the object of volume fracturing,was put forward.By applying geophysical prediction method of total organic carbon(TOC)level and brittleness index,a five-step shale oil and gas sweet spot identification and comprehensive evaluation workflow was proposed on the basis of vertical differentiated study of shale reservoir characteristics,and the impact analysis of heterogeneity on production difference of sweet spot.The first step is to vertically study and classify reservoirs and ensure which layer is sweet spot;the second step is to determinate the planar partition of the target shale according to geophysical prediction results and geological parameters;the third step is to describe and understand characteristics of sweet spot volume through geological parameters and engineering parameters;the forth step is to optimize fracturing design for every horizontal well or one pad by level of understanding for sweet spot volume character-istics;and the last step is to judge development design of oil and gas field by production data analysis.The results show that:the TOC of Longmaxi formation is within 2%—8%,the shale gas content is among 1.7—4.8m~3/t,and the mass fraction of brittle minerals ranges from 20%to 70%.The threshold value for sweet spot identification is that the TOC should be larger than3%,with the shale gas content bigger than 2 m~3/t and the mass fraction of brittle minerals higher than 40%.Because of different threshold value of three parameters in different areas,this workflow is favorable for applicability adjustment of shale oil and shale gas exploration,development,drilling and completion techniques.
引文
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[3]王祥,刘玉华,张敏,等.页岩气形成条件及成藏影响因素研究[J].天然气地球科学,2010,21(2):22-26.WANG Xiang,LIU Yuhua,ZHANG Min,et al.Conditions offormation and accumulation for shale gas[J].Natural Gas Geoscience,2010,21(2):22-26.
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[6]刘成林,葛岩,范柏江,等.页岩气成藏模式研究[J].油气地质与采收率,2010,17(5):1-5.LIU Chenglin,GE Yan,FAN Baijiang,et al.Study on shale gas accumulation mode[J].Petroleum Geology and Recovery Efficiency,2010,17(5):1-5.
[7]范昌育,王震亮.页岩气富集与高产的地质因素和过程[J].石油实验地质,2010,32(5):465-469.FAN Changyu,WANG Zhenliang.Geological factors and process in enrichment and high production of shale gas[J].Petroleum Geology and Experiment,2010,32(5):465-469.
[8]范柏江,师良,庞雄奇.页岩气成藏特点及勘探选区条件[J].油气地质与采收,2011,18(6):9-13.FAN Baijiang,SHI Liang,PANG Xiongqi.Accumulation characteristics and exploration screening of shale[J].Petroleum Geology and Recovery Efficiency,2011,18(6):9-13.
[9]王阳,朱炎铭,陈尚斌,等.湘西北下寒武统牛蹄塘组页岩气形成条件分析[J].中国矿业大学学报,2013,42(4):586-594.WANG Yang,ZHU Yanming,CHEN Shangbin,et al.Formation conditions of shale gas in Lower Cambrian Niutitang formation,northwestern Hunan[J].Journal of China University of Mining&Technology,2013,42(4):586-594.
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[11]肖贤明,宋之光,朱炎铭,等.北美页岩气研究及对我国下古生界页岩气开发的启示[J].煤炭学报,2013,38(5):721-727.XIAO Xianming,SONG Zhiguang,ZHU Yanming,et al.Summary of shale gas research in North American and revelations to shale gas exploration of Lower Paleozoic strata inChina south area[J].Journal of China Coal Society,2013,38(5):721-727.
[12]郭英海,赵迪斐.微观尺度海相页岩储层微观非均质性研究[J].中国矿业大学学报,2015,44(2):300-GUO Yinghai,ZHAO Difei.Analysis of micro-scale heterogeneity characteristics in marine shale gas reservoir[J].Journal of China University of Mining&Technology,2015,44(2):300-307.
[13]胡东风,张汉荣,倪楷,等.四川盆地东南缘海相页岩气保存条件及其主控因素[J].天然气工业,2014,34(6):1-7.HU Dongfeng,ZHANG Hanrong,NI Kai,et al.Main controlling factors for gas preservation conditions of marine shale in southeastern margins of the Sichuan basin[J].Natural Gas Industry,2014,34(6):1-7.
[14]李志明,全秋琦.中国南部奥陶-志留纪笔石页岩相类型及其构造古地理[J].地球科学(中国地质大学报),1992,17(3):261-268.LI Zhiming,QUAN Qiuqi.Lithofacies types and tectonic paleogeography of Ordovician and Silurian graptolite-bearing strata in south China[J].Earth Science(Journal of China University of Geosciences),1992,17(3):261-268.
[15]周恳恳,牟传龙,许效松,等.华南中上扬子早志留世古地理与生储盖层分布[J].石油勘探与开发,2014,41(5):623-632.ZHOU Kenken,MU Chuanlong,XU Xiaosong,et al.Early Silurian paleogeography and source-reservoir-cap rocks of the Middle-Upper Yangtze region in south China[J].Petroleum Exploration and Development,2014,41(5):623-632.
[16]苏文博,李志明,FRANK R E,等.华南五峰组-龙马溪组黑色岩系时空展布的主控因素及其启示[J].地球科学(中国地质大学学报),2007,32(6):819-827.SU Wenbo,LI Zhiming,FRANK R E,et al.Distribution of black shale in the Wufeng-Longmaxi formations(Ordovician-Silurian),South China:major controlling factors and implications[J].Earth Science(Journal of China University of Geosciences),2007,32(6):819-827.
[17]万洪程,孙玮,刘树根,等.四川盆地及周缘地区五峰-龙马溪组页岩气概况及前景评价[J].成都理工大学学报(自然科学版),2012,39(2):176-181.WAN Hongcheng,SUN Wei,LIU Shugen,et al.General situation and prospect evaluation of the shale gas in Wufeng-Longmaxi formation of Sichuan basin and surrounding areas[J].Journal of Chengdu University of Technology(Science&Technology Edition),2012,39(2):176-181.
[18]张春明,姜在兴,郭英海,等.川东南-黔北地区龙马溪组地球化学特征与古环境恢复[J].地质科技情报,2013,32(2):124-129.ZHANG Chunming,JIANG Zaixing,GUO Yinghai,et al.Geochemical characteristics and paleoenvironment reconstruction of the Longmaxi formation in southeast Sichuan and north Guizhou[J].Geological Science and Technology Information,2013,32(2):124-129.
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