非均质储层夹层控油作用初论——非均质储层油气分布规律及测井响应特征

根据毛细管压力理论, 分析了具有复杂孔隙结构的非均质储层油气聚集和分布规律.提出了非均质储层夹层对油气聚集和分布有重要控制作用的观点.分析表明, 物性较差的非均质储层一般具有较长的油-水或气-水过渡段, 形成油气藏的必要条件是要具备较大的圈闭高度.圈闭高度有限的非均质储层中夹层对油气流体有遮挡作用, 储层纵向上容易形成大段的不饱和含油(气) 水层或油水同层、气水同层.根据相对渗透率数据, 这类储层的有效产液能力受两相渗流的影响和本身渗透能力差的限制, 往往表现为低产甚至偏干的事实.导致气测录井、测井和试油测试之间存在矛盾.对非均质储层测井响应规律和特点进行了分析, 复杂孔隙结构非均质储层中含油性与储层物性的相关关系变得模糊.储层纵向上含油性及物性的复杂变化导致其油气层和水层的测井特征不易区分, 测井油气识别与评价面临很多困难和挑战.结合我国西部M盆地一个非均质油气藏的典型实例, 实际分析了非均质储层油气聚集和分布规律及测井响应特征. 

Controlling Effects of Poor Permeable Layers upon Accumulation and Distribution of Hydrocarbon in Inhomogeneous Sandstone Reservoir

Based on capillary pressure theory, the accumulation and distribution of hydrocarbon in inhomogeneous sandstone reservoir with complicated pore structures were analyzed. It was concluded that the accumulation and distribution of hydrocarbon in inhomogeneous reservoir were predominated by the poor permeable layers (barrier beds). The analysis demonstrated that the transition intervals would be long in inhomogeneous reservoir with moderate to low porosity and permeability. The entrapment in this kind of reservoir requested larger closure height. In the situation of limited closure, the poor permeable layers resulted in sealing process and formed non-saturated, both hydrocarbon and free water-bearing stratum with broader distribution vertically. The production ability was much limited because of the low effective permeability in the porous media with two-phase liquid system. All those features bring about a contradiction between the gas logs, well logs and the well testing. The well log responses and characteristics of this reservoir were also discussed in this paper both theoretically and by the case study. Generally, the correlation in well logs between the hydrocarbon saturation and the porosity in this formation became obscure and difficult to distinguish due to the great changes in porosity and saturation of the reservoir vertically. A case study was also presented and proved a good evidence of the above theoretical deductions.