本文为国家自然科学基金项目（编号 42230808）资助的成果。
Liu Jin
1) School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China; 2) Laboratory of Xinjiang Shale Oil Exploration and Development, Karamay, Xinjiang 834000, China; 3) Research Institute of Experiment and Detection, Xinjiang Oilfield Company PetroChina, Karamay, Xinjiang 834000, China;陆相咸化湖盆页岩油甜点孔隙特征与形成机制复杂，是陆相页岩油研究的关键科学问题。本文以准噶尔盆地吉木萨尔凹陷芦草沟组为例，综合应用岩石薄片观测、X射线衍射、高压压汞、氮气吸附、扫描电镜、电子探针、碳- 氧同位素分析和成岩反演等方法，对此进行了研究。结果表明，以芦草沟组为例的陆相咸化湖盆页岩油甜点段矿物组成以长英质碎屑矿物和碳酸盐类矿物为主，黏土矿物含量较低，成分成熟度低，属于湖相混积岩。甜点孔隙以微—纳米孔为主，类型丰富，半径大于1 μm的孔隙主要为粒间溶蚀扩大孔与粒内溶孔，100 nm~1 μm主要为晶间孔，小于100 nm主要为黏土级碎屑颗粒粒间孔。沉积微相是控制甜点孔隙发育的关键，特别是滩坝相和三角洲前缘亚相原生孔隙发育，且抗压实能力强，粒间孔保存较好；溶蚀作用是次生孔隙形成的主要原因，进一步改善了储层物性；含铁白云石胶结总体上降低了孔隙度，但也在一定程度上增强了储层刚性，有利于部分孔隙保存。陆相咸化湖盆页岩油甜点孔隙演化呈现快速压实减孔、酸性溶蚀增孔和含铁白云石胶结减孔“三段式”特征，相互之间的匹配关系是控制孔隙发育的关键。
The pore characteristics and formation mechanism of shale oil sweet spots in terrestrially saline lacustrine basins are very complex and remain a critical and challenging scientific issue in the study of terrestrial shale oil geology. To address this issue, taking the Lucaogou Formation in the Jimsar sag, Junggar basin as an example, this paper comprehensively applied the methods of rock thin section observation, XRD, high- pressure mercury injection, nitrogen adsorption, SEM, EPMA, carbon- oxygen isotope analysis and diagenetic inversion. Results show that the sweet spot of shale oil in saline lacustrine basins (as represented by the Lucaogou Formation in this study) is mainly composed of felsic minerals and carbonate minerals, with low content of clay minerals and low composition maturity. These point to the complex lithology of lacustrine mixed rock. The pores in sweet spots are mainly micro and nano pores of diverse types. Pores with radius greater than 1 μm are mainly enhanced inter- granular dissolution pores and intragranular dissolved pores, pores with radius between 100 nm and 1 μm are intercrystal pores, and pores with radius less than 100 nm are intergranular pores formed by clay- size particle. Sedimentary microfacies is the key to control the development of sweet spot pores, especially the primary pores in the beach- bar facies and delta front subfacies, which have strong compaction resistance and better preservation of intergranular pores. Dissolution is the main reason for the formation of secondary pores, which further improves the reservoir properties. The cementation of iron- bearing dolomite reduces the porosity on the whole, but also enhances the rigidity of reservoir to certain extent, which is conditionally conducive to the preservation of pores. The evolution of the pore structure of shale oil sweet spot in terrestrially saline lacustrine basins shows a “three- stage” characteristic, i.e., rapid compaction and pore reduction, pore improvement caused by acid fluid dissolution, and pore reduction by iron- bearing dolomite cementation. A good match between these three controls is the key to determine the pore evolution and final development.
刘金,王剑,马啸,谭静强,刘淼,郑雨,曹剑.2023.陆相咸化湖盆页岩油甜点孔隙特征与成因——以准噶尔盆地芦草沟组为例[J].地质学报,97(3):864-878.
Liu Jin, Wang Jian, Ma Xiao, Tan Jingqiang, Liu Miao, Zheng Yu, Cao Jian.2023. Pore characteristics and genesis of shale oil sweet spots in saline lacustrine basins: A case study from the Lucaogou Formation in the Junggar basin[J]. Acta Geologica Sinica,97(3):864-878.
