川东北元坝中部地区须家河组致密储层裂缝特征及成因探讨
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摘要
川东北元坝中部地区须家河组致密气藏近年来取得油气勘探的重大突破,裂缝对天然气的运移、富集成藏及产能具有重要影响。综合运用野外露头、岩心、成像测井、包裹体分析以及声发射实验资料,对该区裂缝特征及成因进行研究。研究区主要发育构造成因的低角度剪切缝和高角度剪切缝,具有裂缝延伸中等、宽度小、多闭合、密度较小、充填程度较低的特征,高角度缝和直立缝有效性最好;构造裂缝主要形成期次有三期。第一期为燕山运动晚期,受近SN向构造应力场挤压,形成了NW—SE和NE—SW两组平面"X"型共轭剪切裂缝和近SN向低角度剖面剪切缝,古地应力的最大有效主应力为18.8MPa;第二期为喜马拉雅早—中期构造运动,在NE的挤压力作用下形成近SN向、近EW向平面"X"型共轭剪切缝,古地应力的最大有效主应力为27.9MPa;第三期为喜马拉雅运动晚期,构造应力方向仍为NE,主要形成NW向剖面"X"型剪切缝,古地应力的最大有效主应力为38.6MPa。
The tight gas reservoir in the central Yuanba area of Sichuan basin is one of the major breakthrough in oil and gas survey in recent years. The fractures have important influence on the migration, enrichment and production capacity of the natural gas.Based on the outcrop, core, imaging log, inclusion analysis and acoustic emission experiment data, we studied the fracture characteristics and its genesis of structural fractures in this area. The low-angle shear and high-angle shear fractures lead to the tectonic origin. The fractures have the characteristic of middle scale, minor width(sealed), high thickness, lower density and less filled degree. The high-angle and vertical fractures have better validity. It shows that there are three fracture generations in central Yuanba area: the first stage fractures are formed in late-Yanshanian tectonic movement, NW—SE and NE—SE of plane "X" conjugate shear fractures and low section shear fractures are formed under the compression of SN tectonic stress. The maximum effective principal stress of the paleostructural stress is 18.8 MPa. The fractures in the second stage are formed in middle Himalaya tectonic movement, SN and EW of plane "X" conjugate shear fractures are formed under the compression of NE tectonic stress. The maximum effective principal stress of the paleostructural stress is 27.9 MPa. The third stage are formed in late Himalaya tectonic movement. The structural stress direction is still NE, which mainly forms NW angle section shear fractures and the maximum effective principal stress of the paleostructural stress is 38.6 MPa.
The tight gas reservoir in the central Yuanba area of Sichuan basin is one of the major breakthrough in oil and gas survey in recent years. The fractures have important influence on the migration, enrichment and production capacity of the natural gas.Based on the outcrop, core, imaging log, inclusion analysis and acoustic emission experiment data, we studied the fracture characteristics and its genesis of structural fractures in this area. The low-angle shear and high-angle shear fractures lead to the tectonic origin. The fractures have the characteristic of middle scale, minor width(sealed), high thickness, lower density and less filled degree. The high-angle and vertical fractures have better validity. It shows that there are three fracture generations in central Yuanba area: the first stage fractures are formed in late-Yanshanian tectonic movement, NW—SE and NE—SE of plane "X" conjugate shear fractures and low section shear fractures are formed under the compression of SN tectonic stress. The maximum effective principal stress of the paleostructural stress is 18.8 MPa. The fractures in the second stage are formed in middle Himalaya tectonic movement, SN and EW of plane "X" conjugate shear fractures are formed under the compression of NE tectonic stress. The maximum effective principal stress of the paleostructural stress is 27.9 MPa. The third stage are formed in late Himalaya tectonic movement. The structural stress direction is still NE, which mainly forms NW angle section shear fractures and the maximum effective principal stress of the paleostructural stress is 38.6 MPa.
引文
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[2]Larsen B,Grunnaleite I,Gudmundsson A.How fracture systems affect permeability development in shallow-water carbonate rocks;an example from the Gargano Peninsula,Italy[J].Journal of Structural Geology,2010,32(9):1212-1230.
[3]郭彤楼.元坝气田长兴组储层特征与形成主控因素研究[J].岩石学报,2011,27(8):2381-2391.
[4]胡明,邓绍强,陈蓉,等.川东北地区构造应力场及与油气运移关系研究[J].特种油气藏,2008,15(3):14-19.
[5]巩磊,曾联波,裴森奇,等.九龙山构造须二段致密砂岩储层裂缝特征及成因[J].地质科学,2013,48(1):217-226.
[6]盘昌林,刘树根,马永生,等.川东北地区须家河组天然气成藏主控因素分析[J].断块油气田,2011,18(4):418-422.
[7]周进松,童小兰,冯永宏.柴窝堡背斜储层构造裂缝发育特征及控制因素[J].石油学报,2006,27(3):53-56.
[8]邓虎成,周文,姜文利,等.鄂尔多斯盆地麻黄山西区块延长、延安组裂缝成因及期次[J].吉林大学学报:地球科学版,2009,39(5):811-817.
[9]周文,张银德,王洪辉,等.楚雄盆地北部T3-J地层天然裂缝形成期次确定[J].成都理工大学学报:自然科学版,2008,35(2):21-126.
[10]孙宝珊,丁原辰,邵兆刚,等.辽北张强地区燕山期以来主要构造运动期最大主应力的测定[J].地质论评,2000,44(1):92-98.
[11]丁原辰,张大伦.声发射抹录不尽现象在地应力测量中的应用[J].岩石力学与工程学报,1991,10(4):313-326.
[12]胡明.四川盆地东北部构造成因探讨及未来天然气勘探方向[J].特种油气藏,2005,12(6):11-14.
[13]郭正吾,邓康龄,韩永辉.四川盆地形成与演化[M].北京:地质出版社,1994.
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