鄂尔多斯盆地西南部镇泾地区长8油层组致密储层评价

综合鄂尔多斯盆地西南部镇泾地区延长组长8油层组的岩心、薄片、孔渗及压汞测试等资料,在长8储层结构、储层质量发育控制因素研究基础上,对长8低渗致密砂岩储层进行了分类评价。结果表明,长8砂岩储层发育低孔-特低渗储集物性,储层孔隙结构具有细-微孔喉、排驱压力大、分选差的特征,主要可分为3种类型,其中发育Ⅰ型曲线储层孔渗性最好。沉积作用形成的物质基础决定了储层原始孔渗性能,其中分流河道及水下分流河道具最优孔渗性能;成岩作用中,压实作用是储层储集性能破坏的主要因素;溶蚀作用起建设性改善作用。选取孔隙度、渗透率、孔隙排驱压力、中值压力和中值孔喉半径等主要储层参数进行聚类分析,将长8储层划分为3种类型:Ⅰ类为最好储层,Ⅱ类为较好储层,Ⅲ类为相对最差储层。其中,Ⅰ类储层主要分布于分流河道分叉叠置及水下分流河道汇聚叠合部位,储层品质最好,为最有利勘探目标。

Tight reservoir evaluation of the Chang 8 oil group in the Zhenjing area, southwestern Ordos basin

Based on the comprehensive analysis of the cores,thin sections,reservoir property and mercury injection data,this work analyzed the characteristics of reservoir structure and control factors of reservoir quality and made classification and evaluation to the Chang 8 oil group tight sandstone reservoirs of Yanchang Formation in the Zhenjing area,southwestern Ordos basin.The results show that Chang 8 sandstone reservoirs have low porosity and extremely low permeability.The reservoirs are characterized by the pore structure of fine-micro pore throat,high displacement pressure and poor sorting,which can be divided into 3 types.The reservoirs of type Ⅰ curve have the best reservoir property of pore permeability.The material basis for the depositions dictated the original porosity and permeability.The distributary channels and subaqueous distributary channels develop the optimal reservoir performance.Compaction and cementation are the main factors to damage the reservoir properties.Dissolutions are constructive factors for the improvement of reservoir properties.Combined with the sedimentary facies and pore characteristics of the reservoirs,the porosity,permeability,pore displacement pressure,median pressure and median pore throat radius were chosen to perform a cluster analysis to classify the reservoir types.The reservoirs of Chang 8 oil group were divided into 3 types.Type Ⅰ is the best reservoirs.Type Ⅲ is the relatively worst reservoirs.The type Ⅰ reservoirs are mainly distributed in the overlapping part of distributary channels and superimposition part of subaqueous distributary channels,where the reservoir quality is the best and the most favorable exploration targets are present.