鄂尔多斯盆地致密油藏天然裂缝与人工裂缝特征及开发意义
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摘要
裂缝特征参数是致密油藏开发方式及井网优化的依据;针对致密油藏体积压裂下如何确定开发方式,通过对矿场测试的人工裂缝、天然裂缝和地应力方向采用高斯函数拟合,研究三者之间优势方向的耦合关系。针对致密油藏体积压裂人工裂缝有效参数的认识,提出以自然能量开发井网为研究对象,依据人工压裂缝控制区域和非控制区域压力变化规律的差异性,通过建立水平井分区渗流模型及拟合水平井生产数据,确定人工裂缝有效缝长;在此基础上,建立典型井精细地质模型及数值模型,对比不同裂缝有效宽度下数值模拟平均单段产量与实际统计单段平均产量,观察水平检查井取芯结果。结果表明:人工裂缝的优势方向与地应力优势方向基本一致;地应力的优势方向与天然裂缝优势方向差异较大的致密油藏,采用准自然能量开发,基本一致或差异小的致密油藏,具有注水补充能量的潜力;人工裂缝平均有效宽度小于等于10 m。
The characteristics of the fractures in a tight oil reservoir are the basis for the selection of oil exploitation modes and well pattern optimization. In this study, a Gauss function fitting method was adopted to investigate the coupling relationship among the natural fractures, fractures generated by hydraulic fracturing and in-situ formation stress. Using the effective parameters of the hydraulic fracturing via volumetric fracturing in the tight oil reservoirs, the effective length of the hydraulic fractures can be identified through the analysis of the pressure difference between fracture controlled and uncontrolled zones by fitting the production data of the horizontal wells according to the established flow model based on the natural energy development mode. On this basis, a numerical simulation model of typical wells can be established. By comparing the production predicted by the numerical simulation and the actual field data, the reliability of the above analysis method can be verified along with the coring observation from the inspection wells between the horizontal wells. The results show that the dominant direction of the hydraulic fractures is basically the same as that of the in-situ stress, and these reservoirs can be produced via a natural energy development mode. For the tight oil reservoirs with the dominant direction of the in-situ stress different from that of its natural fractures, water injection technique can be considered. For the cases studied in this paper, the average effective fracture width is less than or equal to 10 m.
The characteristics of the fractures in a tight oil reservoir are the basis for the selection of oil exploitation modes and well pattern optimization. In this study, a Gauss function fitting method was adopted to investigate the coupling relationship among the natural fractures, fractures generated by hydraulic fracturing and in-situ formation stress. Using the effective parameters of the hydraulic fracturing via volumetric fracturing in the tight oil reservoirs, the effective length of the hydraulic fractures can be identified through the analysis of the pressure difference between fracture controlled and uncontrolled zones by fitting the production data of the horizontal wells according to the established flow model based on the natural energy development mode. On this basis, a numerical simulation model of typical wells can be established. By comparing the production predicted by the numerical simulation and the actual field data, the reliability of the above analysis method can be verified along with the coring observation from the inspection wells between the horizontal wells. The results show that the dominant direction of the hydraulic fractures is basically the same as that of the in-situ stress, and these reservoirs can be produced via a natural energy development mode. For the tight oil reservoirs with the dominant direction of the in-situ stress different from that of its natural fractures, water injection technique can be considered. For the cases studied in this paper, the average effective fracture width is less than or equal to 10 m.
引文
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[12] 万晓龙,高春宁,王永康,等.人工裂缝与天然裂缝耦合关系及其开发意义[J].地质力学学报,2009,26(10):245-250.WAN Xiaolong,GAO Chunning,WANG Yongkang,et al.Coupled relationship between created and natural fractures and its implication to development[J].Journal of Geomechanics,2009,26(10):245-250.
[13] 魏漪,冉启全,李冉,等.基于分区补给物质平衡法预测致密油压裂水平井动态储量[J].石油勘探与开发,2016,43(3):448-455.WEI Yi,RAN Qiquan,LI Ran,et al.Determination of dynamic reserves of fractured horizontal wells in tight oil reservoirs by multi-region material balance method [J].Petroleum Exploration and Development,2016,43(3):448-455.
[14] BLASINGAME T A,MCGRAY T L,LEE W J.Decline curve analysis for variable pressure drop/variable flow rate systems[R].SPE 21513-MS,1991.
[15] 孙贺东.油气井现代产量递减分析方法及应用[M].北京:石油工业出版社,2013.
[2] 周新桂,张林炎,范昆.油气盆地低渗透储层裂缝预测研究现状及进展[J].地质论评,2006,52(6):777-782.ZHOU Xingui,ZHANG Linyan,FAN Kun.The research situation and progresses of natural fracture for low permeability reservoirs in oil and gas basin[J].Geological Review,2006,52(6):777-782.
[3] 樊建明,杨子清,李卫兵,等.鄂尔多斯盆地长7致密油水平井体积压裂开发效果评价及认识[J].中国石油大学学报(自然科学版),2015,39(4):103-110.FAN Jianming,YANG Ziqing,LI Weibing,et al.Assessment of fracturing treatment of horizontal wells using SRV technique for Chang-7 tight oil reservoir in Ordos Basin[J].Journal of China University of Petroleum(Edition of Natural Science),2015,39(4):103-110.
[4] 赵继勇,樊建明,何永宏,等.超低渗致密油藏水平井开发注采参数优化实践:以鄂尔多斯盆地长庆油田为例[J].石油勘探与开发,2015,42(1):68-75.ZHAO Jiyong,FAN Jianming,HE Yonghong,et al.Optimization of horizontal well injection-production parameters for ultra-low permeable tight oil production:a case from Changqing Oilfield,Ordos Basin[J].Petroleum Exploration and Development,2015,42(1):68-75.
[5] 张莉.陕甘宁盆地储层裂缝特征及形成的构造应力场分析[J].地质科技情报,2003,22(2):21-24.ZHANG Li.Characteristics of reservoir fracture and the analysis of stress field in Shaanxi-Gansu-Ningxia Basin[J].Geological Science and Technology Information,2003,22(2):21-24.
[6] 周新桂,邓宏文,操成杰,等.储层构造裂缝定量预测研究及评价方法[J].地球学报,2003,24(20):175-180.ZHOU Xingui,DENG Hongwen,CAO Chengjie,et al.The methods for quantitative prediction and evaluation of structural fissures in reservoirs[J].Acta Geoscientia Sinica,2003,24(20):175-180.
[7] 曾联波,李忠兴,史成恩,等.鄂尔多斯盆地上三叠统延长组特低渗透砂岩储层裂缝特征及成因[J].地质学报,2007,81(2):174-180.ZENG Lianbo,LI Zhongxing,SHI Cheng? en,et al.Characteristics and origin of fractures in the extra low permeability sandstone reservoirs of the upper triassic Yanchang formation in the Ordos Basin[J].Acta Geologica Sinica,2007,81(2):174-180.
[8] ZENG Lianbo,GAO Chunyu,QI Jiafu,et al.The distribution rule and seepage effect of the fractures in the ultra-low permeability sandstone reservoir in east Gansu Province,Ordos Basin[J].Science in China(Ser D):Earth Sciences,2008,51(sup II):44-52.
[9] ZENG Lianbo,LI Xiangyang.Fractures in sandstone reservoirs of ultra-low permeability:the Upper Triassic Yanchang Formation in the Ordos Basin,China[J].AAPG Bulletin,2009,93(4):461-477.
[10] 曾联波,文世鹏,肖淑蓉.低渗透油气储集层裂缝空间分布的定量预测[J].勘探家,1998,3(2):24-26.ZENG Lianbo,WEN Shipeng,XIAO Shurong.Quantitative prediction of fracture space distribution in low-permeability reservoir[J].Petroleum Explorationist,1998,3(2):24-26.
[11] 宋惠珍,曾海荣,孙君秀,等.储层构造裂缝预测方法及其应用[J].地震地质,1999,21(3):205-213.SONG Huizhen,ZENG Hairong,SUN Junxiu,et al.Methods of reservoir tectonic fracture prediction and its application[J].Seismology and Geology,1999,21(3):205-213.
[12] 万晓龙,高春宁,王永康,等.人工裂缝与天然裂缝耦合关系及其开发意义[J].地质力学学报,2009,26(10):245-250.WAN Xiaolong,GAO Chunning,WANG Yongkang,et al.Coupled relationship between created and natural fractures and its implication to development[J].Journal of Geomechanics,2009,26(10):245-250.
[13] 魏漪,冉启全,李冉,等.基于分区补给物质平衡法预测致密油压裂水平井动态储量[J].石油勘探与开发,2016,43(3):448-455.WEI Yi,RAN Qiquan,LI Ran,et al.Determination of dynamic reserves of fractured horizontal wells in tight oil reservoirs by multi-region material balance method [J].Petroleum Exploration and Development,2016,43(3):448-455.
[14] BLASINGAME T A,MCGRAY T L,LEE W J.Decline curve analysis for variable pressure drop/variable flow rate systems[R].SPE 21513-MS,1991.
[15] 孙贺东.油气井现代产量递减分析方法及应用[M].北京:石油工业出版社,2013.