摘要
近期四川盆地资阳地区的ZY2井和Z201井在寒武系筇竹寺组页岩获得重大油气突破,展示了该新层系良好的页岩气勘探开发前景,但天然裂缝的发育特征对页岩气的保存、富集及有效开发等具有重要影响。为揭示多期次构造背景下寒武系筇竹寺组页岩天然裂缝的发育特征及其控制因素,采用野外露头调查、岩心观察、测井解释、高分辨率岩心扫描及无人机定量辅助等技术,明确了裂缝类型、特征、发育模式及控制因素,并探讨了裂缝对页岩气富集、保存及开发效果的控制作用。研究结果表明:①该区筇竹寺组页岩主要发育构造成因的剪切缝和张性缝,多期、多类型裂缝交织形成了复杂的孔缝网络;纵向上裂缝密度差异性明显,筇竹寺组一段①、③、⑤小层裂缝密度大,发育层内限制型、穿层过渡型、层内延伸型及复合型4种裂缝模式,其中穿层过渡型广泛发育。②天然裂缝发育受控于构造因素(褶皱和断层)和非构造因素(有机碳含量、脆性矿物含量、岩性岩相及岩石力学层厚度),裂缝密度与距断层距离呈负指数关系,即距离断层越远,裂缝密度越低且趋于稳定,背斜核部的裂缝密度远高于翼部,高TOC(大于或等于2%)和高脆性矿物含量(大于或等于70%)有利于页岩中裂缝发育(尤其是薄层硅质页岩裂缝最为发育)。③筇竹寺组页岩中天然裂缝通过控制人工压裂缝的延伸距离和缝网复杂性,可显著影响页岩气储层改造效果,采用多层立体井网开发模式,页岩气预期整体采收率可达35%。结论认为,针对多期次构造运动背景下深层筇竹寺组页岩天然裂缝的精细准确表征,是此构造背景下深层页岩气有效开发的关键地质基础,研究成果为优化该领域、该类型深层页岩气勘探开发策略提供了关键地质依据。
Recently,Wells ZY2 and Z201 in the Ziyang Area of the Sichuan Basin have achieved significant oil and gas breakthroughs in the Cambrian Qiongzhusi Formation shale,which demonstrates the promising prospects of shale gas exploration and development in this formation.The development characteristics of natural fractures play a crucial role in the preservation,enrichment and effective exploitation of shale gas.To elucidate the development characteristics and controlling factors of natural fractures in the Cambrian Qiongzhusi Formation shale in the context of multiphase structures,this paper clarifies the types,characteristics,development patterns,and controlling factors of fractures by means of of field outcrop investigation,core observation,well log interpretation,high-resolution core scanning,UAV quantitative assistance and other techniques.In addition,the controlling effect of fractures on the enrichment,preservation and development of shale gas is discussed.And the following research results are obtained.First,the fractures developed in the Qiongzhusi Formation shale in this area are mainly tectogenetic shear fractures and tensile fractures,and the fractures of multiple stages and types intersect to form a complex pore-fracture network.Fracture density varies greatly along the vertical direction,with the 1st,3rd,and 5th sublayers of the 1st Member of Qiongzhusi Formation exhibiting greater fracture density.There are four fracture patterns,i.e.,intralayer constrained type,through-layer transitional type,intralayer extensional type,and composite type,among which,the through-layer transitional type is widely developed.Second,the development of natural fractures is under the joint control of tectonic factors(fold and fault)and non-tectonic factors(TOC,brittle mineral content,lithology&lithofacies,and rock mechanical layer thickness).Fracture density exhibits a negative exponential relationship with the distance from faults,that is,the farther from the fault,the lower and more stable the fracture density.The fracture density at the anticline core is significantly higher than at the flank.High TOC(≥2%)and high brittle mineral content(≥70%)are favorable for fracture development in shale.Fractures are developed in thin shale,and especially those in thin siliceous shale are the most developed.Third,natural fractures in the Qiongzhusi Formation shale have a significant influence on the stimulation effect of shale gas reservoirs by controlling the extension distance of hydraulic fractures and the complexity of fracture network.It is predicted that the overall recovery factor of shale gas can reach 35%by employing a development model of multi-layer tridimensional well pattern.In conclusion,the accurate characterization of natural fractures in the deep Qiongzhusi Formation shale in the context of multiphase tectonic movement is the key geological foundation for the effective development of deep shale gas under this structural background.The research findings provide critical geological evidence for optimizing the exploration and development strategies of this type of deep shale gas in this field.
作者
雍锐
吴建发
刘勇
赵圣贤
刘文平
张德良
沈骋
谢圣阳
李博
田鹤
YONG Rui;WU Jianfa;LIU Yong;ZHAO Shengxian;LIU Wenping;ZHANG Deliang;SHEN Cheng;XIE Shengyang;LI Bo;TIAN He(PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610051,China;Sichuan Key Laboratory of Shale Gas Evaluation and Extraction,Chengdu,Sichuan 610213,China;Shale Gas Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610051,China;Field Development Management Department,PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610056,China;Sichuan Shale Gas Exploration and Development Co.,Ltd.,Chengdu,Sichuan 610017,China)
出处
《天然气工业》
北大核心
2025年第5期1-16,共16页
Natural Gas Industry
基金
中国石油天然气股份有限公司科技专项项目“页岩气规模增储上产与勘探开发技术研究”(编号:2023ZZ21)。
关键词
四川盆地
资阳地区
筇竹寺组
天然裂缝
发育特征
控制因素
多期次构造作用
页岩气富集
Sichuan Basin
Ziyang Area
Qiongzhusi Formation
Natural fracture
Development characteristics
Controlling factor
Multiphase exploration and development strategies of this type of deep shale gas in this field.tectonism
Shale gas enrichment
