霸县凹陷文安斜坡火成岩分布特征及成藏主控因素分析

Formation and Distribution of Igneous Rock Reservoir and Main Controlling Factors in Wen’an Slope of Baxian Depression

霸县凹陷文安斜坡发育火成岩油藏,但油藏富集规律与火成岩的配置关系不明确。通过研究火成岩的岩性、测井特征、地震特征以及纵向及平面分布和发育规律,认为研究区火成岩主要以玄武岩为主,凝灰岩次之,亦见少量辉绿岩,其中玄武岩的声波时差为180~340μs/m,电阻率为0~60Ω·m,地震剖面上表现为中低-中高频、中强振幅、高连续性地震相;辉绿岩的声波时差为140~260μs/m,电阻率为0~500Ω·m,地震剖面上表现为低频强振幅连续地震相。文安斜坡火成岩具有薄层火成岩特征,纵向分布层位比较稳定,最大厚度可达270 m,横向上在整个文安斜坡均有分布,可形成埋藏溶蚀型、构造裂缝型以及火成岩体侧向遮挡型油气藏,且储集层位于生油洼陷附近,不整合及断层组成的疏导体系与之沟通,形成了高产油藏。目前苏39断块已完钻新井9口,平均单井钻遇Ⅰ类油层22.8 m/6层,Ⅱ类油层30.0 m/8层,预测资源量211×10^8 t,有望在文安斜坡实现火成岩勘探重大突破。

Igneous rock reservoir is developed in Wen’an Slope of Baxian Depression in Bohai Sea, North China, but the relationship between the oil accumulation and igneous rock distribution remains not clear. Based on the studies of the lithology, logging characteristics, seismic characteristics, longitudinal, and plane distribution and development of the igneous rocks, the igneous rock distribution and main controlling factors were analyzed. The main igneous rocks in the study area are basalt, followed by tuff, and some diabase. The acoustic time difference of the basalt is 180-~340 μs/m, the resistivity is 0~60 Ω·m, and the seismic profiling shows medium to high frequency, medium to strong amplitude, and high continuity features;and the acoustic time difference of diabase is 140~260 μs/m, the resistivity is 0~500 Ω·m, and the seismic profiling shows continuous seismic facies with low frequency and strong amplitude. The igneous rocks are characteristic of thin-layer igneous rock, the vertical distribution is relatively stable, and the maximum thickness can reach 270 m. It is distributed horizontally in the whole Wen’an Slope, and formed buried dissolution type, structural fracture type, and lateral shielding type oil and gas reservoir of igneous rocks. The reservoir is located near the source depression, which is connected with the dredge system composed of unconformity and fault, forming a high yield reservoir. At present, nine new wells have been drilled in Su 39 Fault Block, with an average of 22.8 m/6 layers of Class I oil layer and 30.0 m/8 layers of Class II oil layer drilled in a single well. The predicted resource is 211×10^8 t, which is expected to achieve a major breakthrough in igneous rock exploration in the Wen’an Slope.