黄骅坳陷上古生界异常压力的分布及其意义

The distribution and significance of abnormal pressure in Upper Paleozoic of Huanghua depression

根据对黄骅坳陷上古生界泥岩声波时差资料的分析 ,认为石炭系煤系地层和二叠系顶部的石千峰组为两个异常高压段。上古生界超压在整个黄骅坳陷均有分布 ,且坳陷南区的超压幅度高于中区。产生超压的原因主要为不均衡压实 ,与烃类生成和黏土矿物转化亦有一定关系。异常高压层作为良好的区域盖层 ,十分有利于古生界含油气系统的保存。实际资料表明 ,超压使上古生界烃源岩生烃滞后 ,油气大量生成和运移期较晚 ,因此既有可能形成“古生古储”、“古生中储”的油气藏 ,还有可能形成“古生新储”油气藏 ,拓宽了以古生界为油气源的找油范围。图 4参 4(王书香摘 )

The analysis results of acoustic data from the Upper Paleozoic strata in Huanghua depression suggest that there are two overpressure intervals within Permian-Carboniferous strata: Carboniferous strata and Shiqianfeng Formation of top Permian strata. Horizontally, the overpressure in coal-measure strata developed in the whole Huanghua depression, and southern region overpressure is stronger than the central. The mechanism to develop overpressure is mainly due to differential compaction, generation of hydrocarbon and clay transformation, according to the analysis of overpressure thickness and depth. The significance of existence of overpressure is to form high-quality regional seal strata that can be favorable to preserve Paleozoic petroleum system. In addition, factual data suggest that the overpressure slows down the evolution of source rocks in Paleozoic strata: obvious in 0.8%-1.05% of R _o with low influence in high temperature stage. This lag effect of hydrocarbon evolution caused to late generation and migration, which increase the probability of reservoir formation including all traps that formed from Paleozoic to Tertiary. Therefore, there are all kinds of reservoirs: Paleozoic reservoir with Paleozoic source; Mesozoic reservoir with Paleozoic source; and Paleozoic reservoir with Cenozoic source, which enlarged the prospecting region that migrate from Paleozoic source rocks.