松辽盆地北部白垩系嫩江组低熟页岩原位渗透率随温度变化演化特征  

Evolution of in-situ permeability of low-maturity shale with the increasing temperature,Cretaceous Nenjiang Formation,northern Songliao Basin,NE China

作　　者：何文渊[1] 蒙启安[2,3] 林铁锋 王瑞[2,3] 刘鑫 马生明[2,3] 李昕 杨帆[2,3] 孙国昕 HE Wenyuan;MENG Qi’an;LIN Tiefeng;WANG Rui;LIU Xin;MA Shengming;LI Xin;YANG Fang;SUN Guoxin(Daqing Oilfield Co.Ltd.,PetroChina,Daqing 163712,China;Exploration and Development Research Institute of Daqing Oilfield Co.Ltd.,Daqing 163712,China;Heilongjiang Provincial Key Laboratory of Shale Oil&Tight Oil Accumulation,Daqing 163712,China)

机构地区：[1]大庆油田有限责任公司,黑龙江大庆163712 [2]大庆油田有限责任公司勘探开发研究院,黑龙江大庆163712 [3]黑龙江省致密油与泥页岩油成藏研究重点实验室,黑龙江大庆163712

出　　处：《石油勘探与开发》2022年第3期453-464,共12页Petroleum Exploration and Development

基　　金：中国石油重大科技专项“古龙页岩油成藏理论与关键技术研究”(2021ZZ10-01)。

摘　　要：通过加温-三轴压力联合的(轴压8 MPa、围压10 MPa)渗透测试、封闭体系页岩电加热热解测试和扫描电镜分析,研究松辽盆地北部白垩系嫩江组二段富有机质低熟页岩平行层理方向原位渗透率的演变规律及特征。研究结果表明:随温度升高,样品原位渗透率呈现先升后降又升的变化规律,375℃时渗透率最低。同一温度下,样品原位渗透率随孔隙压力的增大而减小。低熟页岩原位渗透率演变可划分为5个阶段:①25~300℃,热破裂和黏土矿物的脱水作用改善了渗透性,但渗透率小于0.01×10^(-3)μm^(2)。②300~350℃,有机质热解排烃形成有机成因的矿物粒间孔和微米级孔缝,在有限范围内形成连通的孔隙网络,提高了渗透率。但液态烃内黏稠的沥青质含量高,应力约束下不易流动而滞留于孔隙内,导致渗透率增长缓慢。③350~375℃,有机质大量热解生烃形成孔隙,但液态烃吸附溶胀和应力约束下的附加膨胀热应力,压缩了孔裂隙空间,液态烃难以排出,造成渗透率急剧下降。④375~450℃,有机质生烃后不同矿物之间相互连通的孔隙-微裂隙网络系统、增加的孔隙尺寸和黏土矿物的转化作用,促使应力约束下渗透率的持续升高。⑤450~500℃,稳定的孔隙系统和不同层理方向交错的裂隙系统,造成渗透性显著上升。不同阶段内有机质的热解作用、孔裂隙结构和周围应力的耦合作用是原位渗透率演化的主控因素。Temperature-triaxial permeability testing at the axial pressure of 8 MPa and confining pressure of 10 MPa,closed shale system pyrolysis experiment by electrical heating and scanning electron microscopy analysis are used to study the evolution mechanism of in-situ permeability in the direction parallel to bedding of low mature shale from Member 2(K2n2)of Cretaceous Nenjiang Formation in northern Songliao Basin with mainly Type I kerogen under the effect of temperature.With the increasing temperature,the in-situ permeability presents a peak-valley-peak tendency.The lowest value of in-situ permeability occurs at 375℃.Under the same temperature,the in-situ permeability decreases with the increase of pore pressure.The in-situ permeability evolution of low mature shale can be divided into 5 stages:(1)From 25℃to 300℃,thermal cracking and dehydration of clay minerals improve the permeability.However,the value of permeability is less than 0.01×10^(-3)μm^(2);(2)From 300℃ to 350℃,organic matter pyrolysis and hydrocarbon expulsion result in mineral intergranular pores and micron pore-fractures,these pores and fractures form an interconnected pore network at limited scale,improving the permeability.But the liquid hydrocarbon,with high content of viscous asphaltene,is more difficult to move under stress and more likely to retain in pores,causing slow rise of the permeability.(3)From 350℃to 375℃,pores are formed by organic matter pyrolysis,but the adsorption swelling of liquid hydrocarbon and additional expansion thermal stress constrained by surrounding stress compress the pore-fracture space,making liquid hydrocarbon difficult to expel and permeability reduce rapidly.(4)From 375℃to 450℃,the interconnected pore network between different mineral particles after organic matter conversion,enlarged pores and transformation of clay minerals promote the permeability to increase constantly even under stress constraints.(5)From 450℃to 500℃,the stable pore system and crossed fracture system in different bedding

关 键 词：松辽盆地 白垩系嫩江组 低熟页岩 原位转化 孔裂隙结构 原位渗透率 页岩油 

分 类 号：TE122[石油与天然气工程—油气勘探]