胡尖山地区前侏罗纪古地貌及成藏条件分析

Pre-Jurassic paleogeomorphology and formation conditions of reservoirs in Hujianshan area

卜广平 陈朝兵 成健 柴慧强 李海菲 唐栋梁1

中国石油长庆油田分公司第六采油厂，陕西 西安 710200 西安石油大学地球科学与工程学院，陕西 西安 710065

No.6 Oil Production Plant, Changqing Oilfield Company, PetroChina, Xi′an 710200, China School of Earth Sciences and Engineering, Xi′an Shiyou University, Xi′an 710065, China

运用印模法对鄂尔多斯盆地胡尖山地区前侏罗纪古地貌进行了恢复，并从储盖条件、油源分布、成藏模式、小幅度构造等方面对古地貌油藏的形成条件进行了详细分析。结果表明：受晚三叠世印支运动末幕的影响，研究区延长组顶部遭受剥蚀，形成了沟壑纵横、丘陵起伏、水系广布的地貌形态，可划分为6种地貌单元。古地貌形态对上覆富县组—延安组地层的相带展布、压实披覆构造的形成起到关键作用。古地貌形成的剥蚀面沟通了延长组与延安组的生储盖组合；长7生烃凹陷一定程度上控制了古地貌油藏的宏观分布，距离生烃凹陷越近，延安组油藏分布越密集，产量越高；河间丘、坡嘴、斜坡等地貌单元易形成披覆圈闭、岩性￣构造圈闭，构成相应的成藏模式而聚集油气；油藏范围内，鼻隆、局部隆起等小幅度构造控制着油气的聚集程度和高低产井的分布。

The pre-Jurassic palaeogeomorphology in Hujianshan area of Ordos Basin was restored using the impression method, and the conditions for the formation of palaeogeomorphic reservoirs were analyzed in detail from the aspects of reservoir and seal conditions, oil source distribution, hydrocarbon accumulation model and small scale structures. The results show that affected by the end of the Indosinian Movement at Late Triassic, the top of the Yanchang Formation in the study area was denuded, forming a landform configuration with gully aspect, hilly terrain, and extensive water-spreading, and the landform configuration is divided into six geomorphic units. The palaeogeomorphic form plays a key role in the formation of the facies belt distribution and compacted overlying tectonic of the upper Fuxian and Yan′an formations. The denudation surface formed by the palaeogeomorphology links up the reservoir and the covering strata combination between Yanchang and Yan′an Formations. The Chang 7 hydrocarbon generation depression controls the macro-distribution of the palaeogeomorphic reservoir to a certain extent. The closer the hydrocarbon depression, the denser the reservoir distribution of the Yan′an Formation, the higher the production; the geomorphic units such as the river hillock, the mouth of slope, the slope, etc. are easy to form overlying traps and lithologic-structural traps, and constitute the slope mouth accumulation model, river hillock accumulation model and slope accumulation model, which are the main places of oil and gas accumulation. Within the reservoir range, small scale structures, such as nose-shaped uplift and local uplift, control the degree of hydrocarbon accumulation and the distribution of high and low production wells.

10.6056/dkyqt201901001