砂岩透镜体成藏动力学过程模拟与含油气性定量预测

Process Simulation of Hydrocarbon Accumulation Dynamics and Quantitative Forecast of Oil-Bearing Properties for Sand Lens Reservoir

砂岩透镜体油藏作为我国东部油气储量增长的重点,其成藏动力学研究对于搞清这类特殊油气藏的成藏机理及定量评价和预测圈闭的含油气性具有重要意义.本文利用数值模拟结合地质分析的方法,在对成藏动力与成藏阻力进行系统分析的基础上,通过建立成藏动力地质模型和数学模型及成藏动力学特征方程,对砂岩透镜体成藏过程进行模拟.研究结果表明,成藏主动力包括砂泥岩毛细管压力差、烃浓度差引起的扩散力、烃生成产生的膨胀力,成藏阻力主要为砂体内毛细管阻力及岩石的粘滞力和吸附力;东营凹陷岩性油气藏能否成藏主要受泥岩排烃强度、储层孔隙度、渗透率、地层埋藏深度、泥(页岩)厚度与砂体厚度之比等因素的综合影响;岩性油气藏的形成具有阶段性,在晚成岩阶段,成藏动力大于成藏阻力,油气开始充注,岩性油气藏的形成存在门限深度.利用成藏动力学特征模拟,建立了成藏动力与含油性的定量关系,还可以很好地对平面上砂体的含油饱和度分布进行预测.

As the hotspot and emphasis of petroleum exploration in east China, sand lens reservoir plays an important role in the increase of petroleum reserve. Therefore, it is significant to do research on sand lens reservoir-its hydrocarbon accumulation mechanism, its quantitative evaluation and the forecast of its oil-bearing properties. Based on systematic analysis of hydrocarbon accumulation drive and resistance, we applied numerical simulation and geological statistics to construct geological model as well as mathematic model of hydrocarbon dynamics for sand lens reservoir, and to simulate hydrocarbon accumulation process. The research results show that major accumulation drive consists of capillary pressure difference between sandstone and mudstone, diffusion power resulted from hydrocarbon generation in mudstone and expansion power caused by hydrocarbon generation in mudstone. And the major accumulation resistance includes capillary pressure, sticky and absorption resistance in sandstone. The formation of litbologic reservoir in the Dongying depression was controlled by many factors including hydrocarbon expulsion intensity of mudstone, porosity and permeability of sandstone, buried depth, the ration of thickness of sandstone and thickness of mudstone. The formation of sand lens reservoir can be divided into several stages, and only at the late diagenesis stage, the accumulation drive was greater than the resistance and as a result hydrocarbon filled in sand lens, which shows there exists a threshold buried depth for sand lens. Based on hydrocarbon accumulation dynamics, the authors also constructed quantitative relation between accumulation dynamics and oil-bearing properties, which affords a good means to forecast saturation and its saturation distribution in plane of sand lens pool.