鄂尔多斯盆地延长组长7油层组石油成藏条件分析

Hydrocarbon accumulation conditions of Chang7 section, Yanchang Formation, Ordos Basin

时保宏 郑飞 张艳 黄静 张雷

Shi Baohong Zheng Fei Zhang Yan Huang Jing Zhang Lei

西安石油大学 地球科学与工程学院, 西安 710065 2. 中国石油 长庆油田分公司 勘探开发研究院, 西安 710018 3. 低渗透油气田勘探开发国家工程实验室, 西安 710018

School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China 2. Petroleum Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi'an, Shaanxi 710018, China 3. National Engineering Laboratory for Low Permeability Petroleum Exploration and Development, Xi'an, Shaanxi 710018, China

鄂尔多斯盆地长7油层组沉积期是湖盆发育的鼎盛期，不但沉积了大面积分布的优质烃源岩，而且还发育一定规模的储层。对储层所处沉积环境、储层特征、成岩相及生、储、盖组合等综合地质条件进行分析研究，结果表明，长7储层烃源条件优越，有利储集体主要为三角洲前缘的水下分流河道及半深湖—深湖相浊积岩，岩石类型以低成分成熟度的岩屑长石砂岩和长石岩屑砂岩为主，储层物性差，孔隙度平均8.45%，渗透率平均0.12×10-3 μm2，属超低孔低渗储层；发育5种成岩相类型。最有利成岩相为胶结作用—微孔粒间孔和溶蚀作用—溶孔微孔成岩相，分布面积有限；储层物性最差的为压实胶结—微孔成岩相，分布面积较广。半深湖—深湖沉积环境导致长7储层横向连通性差，纵向隔夹层多，油气只能通过垂向和短距离的侧向运移，在遇到泥岩遮挡层或致密砂岩遮挡时在相对物性较好的储层中聚集成藏。

The Ordos Lake in Chang7 phase was largest and deepest in Yanchang period, and deposited high-quality and widely-distributed source rocks with some sandstones of delta front facies and turbidites facies. The analyses of deposition environment, reservoir feature, diagenetic facies and the assemblage of source, reservoir and cap showed that the Chang7 section had favorable source conditions. The favorable reservoirs mainly included turbidites of underwater distributary channel at delta front and semi-deep/deep lake facies. The sandstones were mainly lithic arkose sandstones and feldspathic lithic sandstones with low compositional and textural maturities. The reservoirs had low porosity (8.45% in average) and low permeability (0.12×10-3 μm2 in average). Chang7 sandstones were divided into 5 diagenetic facies types, among which the most favorable type was the cemetation-micropore intergranular pore and dissolution-dissloved pore and micropore diagenetic facies, but the distribution area was limited. The diagenetic facies with worst reservoir physical properties was the compacted cement-microporous diagenetic facies, which had broader distribution area. The semi-deep/deep lake deposition environment led to poor plane connectivity in Chang7 section. Hydrocarbon mainly migrated vertically, or laterally for short distance, and accumulated when blocked by mudstones or tight sandstones.

陕西省自然科学基金（2012JM5010）资助。

https://doi.org/10.11781/sysydz201403285