东营凹陷砂岩透镜体油气成藏机理及有利区预测

近几年济阳坳陷的勘探实践表明, 对岩性油藏的含油性差异、成藏机理尚认识不清, 这制约了隐蔽油气藏的进一步勘探.在东营凹陷145个砂岩透镜体油藏含油性统计分析的基础上, 结合典型透镜体油藏详细解剖和核磁共振物理模拟实验结果综合研究后发现: 砂岩透镜体圈闭形成时的构造和沉积环境、围岩生排烃条件、砂体储集条件是其成藏的主控因素.只有围岩(源岩) 进入供烃门限后, 其与砂体界面处的毛管压力差、烃浓度梯度产生的扩散力和膨胀力3者之和大于砂体中过剩的水向外渗滤遇到的阻力, 即成藏动力大于成藏阻力时, 砂岩透镜体才能成藏.当砂体沉积环境、围岩生排烃条件、砂体自身储集条件3方面均满足一定条件时, 圈闭才具备形成砂岩透镜体油藏的条件, 并且上述3方面条件越优越, 圈闭含油性就越好.用此方法对东营凹陷下第三系沙三中亚段砂岩透镜体油藏的分布进行了预测. 

Main Accumulation Controlling Factors and Forecast of Sand Lens Reservoir, Dongying Depression, China

Jiyang sub-basin is the most important area of subtle traps in China. Exploration in recent years has shown that the petroliferous property of the sand lens reservoir is quite different and the accumulation mechanism of lithologic reservoir is not clearly comprehended, restricting further exploration. A statistical analysis of the petroliferous properties of 145 lens reservoirs in Dongying depression was carried out, as well as the analysis of typical lenticular pools and NMR modeling experiments. Results show that structural and sedimentary factors, and hydrocarbon generation and expulsion conditions of the surrounding source rock, as well as reservoir properties, are the main controlling factors for lens reservoir formation. Lens reservoir formation depends primarily upon the balance of accumulation power and resistance. When the hydrocarbon supply thresholds have been exceeded the accumulation power is bigger than the resistance at the sand and mud interface, so oil/gas would possibly accumulate to the lens. Accumulation power is made up of different capillary pressures between source and reserve, and hydrocarbon diffusion, as well as hydrocarbon volume expansion. Resistance is the osmotic resistance of flowing liquid. The better the three accumulation controlling factors are matched, the higher the petroliferous property. By applying the research results, the lens reservoir distribution of the third member of the Neogene Shahejie Formation in Dongying depression is forecast.