摘要
四川盆地南部广泛发育海相泥页岩层系,龙马溪组页岩具备优越的页岩气成藏条件。基于钻井岩心观察和分析测试,对富顺-永川地区下志留统龙马溪组页岩有机孔特征及其影响因素进行了研究。结果显示:龙马溪组页岩总有机碳(TOC)含量主要介于2.45%~5.59%,有机质丰度高,镜质体反射率(Ro)介于1.97%~2.23%,有机质达到了高-过成熟,为有机孔发育提供了良好基础;有机孔是页岩气重要的储集空间,根据扫描电镜观察,单个有机孔形态以圆形、椭圆形和凹坑形为主,其次为长条形和不规则形等,边缘较光滑;结合氮吸附与高压压汞实验观察,富顺-永川地区龙马溪组页岩有机孔孔径较小,大多属于介孔范围,介孔占比约为57%。通过建立有机孔孔隙度与自然伽马能谱测井值(U)的关系模型并对全区的有机孔进行定量分析,发现富顺-永川地区龙马溪组页岩有机孔孔隙度介于1.10%~3.64%,平均为2.15%。有机孔发育及保存受多种因素影响,对有机孔孔隙度与粘土矿物、脆性矿物和TOC含量相关关系的研究结果表明:四川盆地富顺-永川地区龙马溪组页岩有机孔孔隙度的大小与粘土矿物含量成负相关、与脆性矿物和TOC含量成正相关,压实作用对有机孔保存起破坏性作用,而较高的地层压力系数有利于有机孔的保存。
The Lower Paleozoic marine shale sequences are widely developed in the southern part of Sichuan Basin.Among others,the Longmaxi Formation shale possesses high-quality source rocks favorable for shale gas enrichment.We discuss the characteristics of and factors influencing the organic pores in the Lower Silurian Longmaxi Formation,Fushun-Yongchuan area,based on coring data obtained from the drilling of organic-rich shale,as well as related analysis and tests. The research results indicate that the organic matter abundance of the Longmaxi Formation shale is high with a TOC content ranging from 2. 45%to 5. 59%,and its thermal evolution reaches a high-to-over-mature stage with a vitrinite reflectance(Ro)of 1. 97%to 2. 23%,providing a favorable basis for the growth of organic pores. As important reservoir space for shale gas,most organic pores are round-,oval-or concave-shaped under scanning electron microscopy(SEM) observation,and a few occur in strips and/or irregular polygons;all pores are smooth-edged.Besides,nitrogen adsorption and high pressure mercury intrusion porosimetry(MIP),show that these organic pores are relatively small in size,most of which are supposed to be ascribed to mesopores,accounting for about 57%. Then,we quantitatively analyze the organic pores across the study area by establishing a relationship model between porosity of organic pores and spectral gamma-ray(GR)logs(U),and the results show that the porosity of organic pores varies between 1. 10%and 3. 64%,with an average of 2. 15%. There are multiple factors related to the development and preservation of organic pores. The correlation between organic pore porosity with contents of clay minerals,brittle minerals and TOC,is set up and shows that the porosity of organic pores is positively correlated with contents of brittle minerals and TOC but negatively with clay mineral content. Compaction has a destructive effect on the preservation of organic pores,and a higher formation pressure coefficient is conducive to the preservation of organic pores.
作者
杨熙雅
刘成林
刘文平
任浩林
Yang Xiya;Liu Chenglin;Liu Wenping;Ren Haolin(State Key Laboratory of Petroleum Resource and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;Eoxploration and Derelopment Research Ilustitute of Southuest Oil&Gasfield Company,PetroChina,Chengdu,Sichuan 610046,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2021年第6期1321-1333,共13页
Oil & Gas Geology
基金
国家自然科学基金项目(41572099,41872127)。
关键词
脆性矿物
有机孔
页岩
龙马溪组
富顺-永川地区
四川盆地
organic pore
brittle mineral
shale
Longmaxi Formation
Fushun-Yongchuan area
Sichuan Basin
作者简介
第一作者简介:杨熙雅(1996-),女,硕士研究生,非常规油气地质。E⁃mail:18801321355@163.com。;通讯作者:刘成林(1970-),男,教授、博士生导师,油气地球化学与资源评价、非常规油气地质。E⁃mail:lclzgx@126.com。
