川中地区公山庙油田侏罗系大安寨段致密油资源潜力分析

The potential of tight oil resource in Jurassic Da’anzhai Formation of the Gongshanmiao oil field, central Sichuan Basin

公山庙油田侏罗系大安寨段油层孔隙度大多小于2%,渗透率一般小于0.05×10-3μm2,属于典型的致密油层。该油层平面上大面积分布,存在明显的"甜点"区;剖面上非均质性强,顶部大一亚段和底部大三亚段的厚层介壳灰岩为主力产油层,中部大一三亚段的介壳灰岩与页岩薄互层为次要产油层。构造、介壳灰岩及暗色泥岩厚度对致密油富集没有明显的控制作用,"甜点"主要分布在公山庙构造西侧斜坡区。通过对公山庙油田大安寨段沉积演化、烃源岩生烃条件、储层特征及油气分布规律的研究,结合生产井数据,运用容积法和产量递减拟合法分别计算可采资源量,预测公山庙油田大安寨段致密油可采资源量分别为338.11万t和155.74万t。

T he Da＇anzhai reservoir in the Gongshanmiao oil field belongs to tight oil type, and its physical properties are extremely tight with porosity less than 2% and permeability below 0.05mD. The oil reservoir in Da＇anzhai extends extensively and has relatively oil enriched places called ＂sweet spots＂. Vertically, the oil layers in Da＇anzhai are strongly heterogeneous. The top and bottom segments of the section are composed of thick shelly limestone and are main producing parts in Da＇anzhai section; the middle segment composed of thin shelly limestone interbedded with shale is the secondary pay zone. The structure and the thickness of shelly limestone and dark shale are not the main mechanism of oil enrichment. ＂Sweet spots＂ are located in the sloping area on the western side of Gongshanmiao. Based on geological information and production data of wells, the authors calculated the recoverable resource using the volumetric method and production decline fitting method, and the result is 3.38 million tons and 1.56 million tons, respectively.