致密砂岩多因子储层精细分级评价方法——以东海盆地西湖凹陷渐新统花港组上段H3砂组为例

Multi-factor evaluation for fine grading of tight sandstone reservoirs:a case study from H3 sand group in the upper section of Oligocene Huagang Formation,Xihu Sag,East China Sea Basin

东海盆地西湖凹陷西次凹渐新统花港组上段H3砂组为低孔低渗—低孔特低渗致密砂岩储层,优质储层分布成为制约开发产能的关键问题。基于岩心、测井及物性测试等资料,对该区进行了沉积微相刻画和储层物性分析,结合构造、沉积微相发育特征,对储层展开精细分级评价和优质储层预测。研究表明,H3砂组储层分布主要受构造特征、沉积微相、砂体厚度和孔渗条件四个因素影响。在综合分析各因素与含气饱和度关系的基础上,建立了受产能约束的四因子储层精细分级评价标准,把H3砂组储层划分为“甜点”储层(Ⅰ类)、中等储层(Ⅱ类)和无效储层(Ⅲ类)三种类型。优质储层预测研究区H3-3小层为可能的高产能潜力带,H3-1、H3-2和H3-4小层次之。

The H3 sand group of the upper section of the Oligocene Huagang Formation in the western sub-sag of the Xihu Sag of the East China Sea Continental Shelf Basin is a tight sandstone reservoir with low porosity and low or ultra-low permeability.The distribution of high-quality reservoirs has become a key factor restricting productivity.Based on coring,well logging and physical property test data,the sedimentary microfacies and physical properties of the H3 sand group were studied,and a fine grading evaluation and“sweet spot”prediction were carried out.The reservoir distribution in the H3 sand group was mainly affected by four factors:structural characteristics,sedimentary microfacies,sand thickness and conditions of porosity and permeability.Moreover,on the basis of comprehensive analysis of the relationship among these factors and gas saturation,a four-factor reservoir fine grading evaluation method was proposed.The H3 sand group reservoirs were divided into three types:“sweet spot”reservoirs(type Ⅰ),medium reservoirs(type Ⅱ)and ineffective reservoirs(type Ⅲ).The H3-3 single sand layer has a great exploration potential,followed by the H3-1,H3-2 and H3-4 single sand layers.