乌尔逊凹陷大一段泥岩盖层封闭能力及其研究意义

SEAL CHARACTERISTICS OF K_1d_1 MUDSTONE CAPROCK AND RESEARCHSIGNIFICANCE IN WUERXUN DEPRESSION

在盖层对各种相态油气封闭机理及其影响因素分析的基础上,系统研究了乌尔逊凹陷大一段泥岩盖层对各种相态油气的封闭特征,证实该泥岩盖层对整个凹陷游离相油气具有好的毛细管直接封闭能力,在凹陷中部具有好的异常孔隙流体压力的间接封闭能力,向凹陷边部变为较好和中等异常孔隙流体压力的间接封闭能力;在凹陷的大部分地区对水溶相天然气和扩散相天然气具有好的封闭能力,在凹陷边部具有较好封闭能力。而且证实泥岩盖层对各种相态油气封闭能力的形成均早于南一段源岩大量排烃期,可以封闭住南一段源岩生成排出的各种相态油气,有利于其在南二段中聚集成藏,这是造成该段油气富集的根本原因。

Based on the study of seal mechanisms of caprock to each phase of oil or gas and their influence factors, this paper sisterly studied seal characteristics of K_1n^1 mudstone caprock to each phase of oil or gas in Wuerxun depression. This paper considered mudstone caprock of K_1n^1 to have best direct ability of capillary seal to oil or gas in free phase, to have best indirect ability of abnormal pore fluid pressure to oil or gas in free phase in the middle of depression and have better and diddle in direct ability of abnormal pore fluid pressure to oil or gas in free in the side of depression. Mudstone caprock of K_1d^1 have best seal ability to gas in water-dissolving phase and diffusion phase in the mast of depression and better seal ability to gas in water-dissolving phase and diffusion phase in the side of depression. The formation period of seal ability of K_1n^1 mudstone caprock is ealier the period of a lot of oil and gas in each phase expelled form K_1n^1 sourcerock. A lot of oil and gas in each phase can be sealed. It is favorable for oil and gas to accumulate and form oil and gas reservoirs. It is the basical cause that there are many oil and gas reservoirs in K_1n^2.