摘要
川东地区龙潭组/吴家坪组发育一套海陆过渡相泥页岩,其含气性特征及控制因素研究薄弱,制约着页岩气的勘探和研究。通过对泥页岩开展地球化学、储层孔隙类型、孔隙结构参数和甲烷吸附等测试,分析了有机碳含量等参数对吸附能力的影响。结果表明,自川东南龙潭组至川东北吴家坪组,富有机质泥页岩形成的环境依次为滨岸沼泽、潮坪泻湖、浅水陆棚相和深水陆棚。龙潭组岩性主要为泥岩、粉砂岩和煤层,有机碳含量较高,多在2%以上;矿物组成以黏土矿物为主,平均含量在42%~70%,随沉积环境变化,黏土矿物组合面貌由以伊蒙混层+高岭石+伊利石为主转变为伊蒙混层+伊利石为主;吴家坪组岩性为硅质页岩和灰岩,有机碳含量为6.56%~7.15%;矿物组成主要为石英,其次为黏土矿物和方解石。龙潭组泥页岩干酪根类型为III型,有机质孔在镜质体和惰质体中发育较差、黏土矿物孔为优势孔隙类型;吴家坪组有机质为Ⅱ1型,有机质孔为主要的孔隙类型,主要发育在腐泥质和固体沥青中。采用三元Langmuir模型对过剩吸附曲线进行校正后,在>5 MPa时,绝对吸附量明显高于过剩吸附量。龙潭组泥页岩的兰氏体积普遍较高,介于2.19~6.98 cm^3/g,吴家坪组泥页岩的兰氏体积为2.08~3.96 cm^3/g,龙潭组泥页岩较高的兰氏体积与其较高的比表面积有关。TOC含量和黏土矿物含量是龙潭组/吴家坪组泥页岩兰氏体积的主控因素。由于这两套泥页岩中有机质孔发育存在显著差异,有机质对甲烷的吸附方式可能明显不同。吴家坪组泥页岩中有机质通过提供大量的吸附位点促进甲烷吸附,而龙潭组Ⅲ型干酪根表面吸附及长链结构线性分配提高了甲烷吸附能力。海陆过渡相页岩中富黏土矿物的吸附作用使其吸附能力显著增加,陆源碎屑石英含量的增加会降低泥页岩的吸附能力。
The Longtan/Wujiaping Formation in eastern Sichuan basin is a set of marine-continental transitional shale.However,the research on its gas-bearing capacity and controlling factors is limited,which restricts the ex-ploration and research of shale gas.In this study,the geochemistry,reservoir pore type,pore structure parameters and methane sorption tests were carried out on the shale samples of the Longtan/Wujiaping Formation,and the effect of TOC content and other parameters on sorption capacity were then analyzed.The results show that from the Longtan formation in southeastern Sichuan basin to the Wujiaping Formation in northeastern Sichuan basin,the shales were formed in sedimentary environment,in order,the coastal swamp,the tidal flat lagoon,the shallow water shelf,and the deeper water shelf.The Longtan Formation is mainly consisted of mudstone,siltstone and coal seam.The TOC content is generally higher than 2%,and the mineral composition is mainly clay minerals,with an average content of 42%-72%.With the change of sedimentary environment,the composition of clay minerals changes from I/S mixed layer+kaolinite+illite dominated to I/S mixed layer+illite dominated.The Wujiaping Formation is mainly consisted of siliceous shale and limestone,with their average TOC contents between 6.56%and 7.15%.The minerals are mainly quartz,followed by clay minerals and calcite.The Longtan Formation mudrocks is dominated by type III kerogen,and the organic matter pores are poorly developed in vitrinite and inertinite,and the clay mineral pores are dominant pore types.While the Wujiaping Formation mudrock is dominated by type II1 kerogen,and organic matter pores are the main pore type,mainly developing within sapropel and solid bitumen.After using the ternary Langmuir model to correct the excess adsorption,the absolute adsorption amount is significantly higher than the excess adsorption amount when the pressure is greater than 5 MPa.The Langmuir volume of the Longtan Formation shale is generally high,ranging from 2.19 to 6.98 cm^3/g,and the Wujiaping Formation shale has Langmuir volume between 2.08 and 3.96 cm^3/g.The higher Langmuir volume is associated with higher surface area for the Longtan Formation shales.TOC and clay mineral contents are the main controlling factors of the Langmuir volume of the Longtan/Wujiaping Formation shale.Due to the significant differences in the development of organic matter pores within the two sets of shales,the sorption of methane by organic matter may be significantly different.The organic matter in the Wujiaping shale promotes methane adsorption capacity by providing a large amount of adsorption sites,while the surface adsorption and the linear distribution of long-chain structures of type III kerogen in the Longtan shale increase the methane adsorption capacity.The adsorption capacity of clay minerals in transition shale could significantly increase shale adsorption capacity,whereas the increase of terrigenous quartz would reduce the adsorption capacity of shale samples.
作者
曹涛涛
曹清古
刘虎
邓模
刘光祥
CAO Taotao;CAO Qinggu;LIU Hu;DENG Mo;LIU Guangxiang(Hunan Provincial Key Laboratory of Shale Gas Resource Utilization,Hunan University of Science and Technology,Xiangtan 411201,China;Wuxi Research Institute of Petroleum Geology,SINOPEC Petroleum Exploration & Production Research Institute,Wuxi 214126,China;Sichuan Key Laboratory of Shale Gas Evaluation and Exploration,Chengdu 600091,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2020年第4期1445-1456,共12页
Journal of China Coal Society
基金
国家自然科学基金资助项目(41820163)
湖南省自然科学基金资助项目(2018JJ3152)
四川省科技计划资助项目(2018JZ0003)。
关键词
页岩组成
孔隙类型
甲烷吸附能力
影响因素
海陆过渡相
川东地区
pore type
shale composition
supercritical methane adsorption
influencing factors
eastern Sichuan Basin
