鄂尔多斯盆地靖边油田李家城则地区长6致密油储层微观特征与含油性

Microscopic characteristics and oil content of Chang 6 tight sandstone reservoirs in Lijiachengze area, Jingbian Oil Field, Ordos Basin

综合应用铸体薄片、荧光薄片、扫描电镜、高压压汞和恒速压汞等分析测试资料,研究了鄂尔多斯盆地靖边油田李家城则地区长6致密砂岩微观特征及含油性。长6砂岩储层岩石类型为细粒长石砂岩,胶结物成分主要为方解石、绿泥石和浊沸石;铸体薄片下,孔隙类型主要以残余粒间孔和各种溶蚀孔隙为主,平均孔隙直径主要分布在20~50 μm;储层物性差,局部发育微裂缝,孔隙结构非常复杂。综合高压压汞和恒速压汞,孔喉半径跨度从纳米级至微米级,但主要存在2个主峰,以孔喉半径小于2 μm的孔隙为主。长6砂岩含油性较差,总体以油斑级别为主,石油主要分布在残余粒间孔和溶蚀孔隙中。达到工业油流井的含油砂岩,其储层孔隙度下限为7.5%,渗透率下限为0.15×10^-3 μm ^2 ,孔喉半径下限为0.1 μm。

The microscopic characteristics and oil-bearing properties of the Chang 6 tight sandstones in Lijiachengze area of the Jingbian Oilfield were studied using the analysis and test data of cast thin sections, thin section fluorescence, scanning electron microscopy, pressure-controlled porosimetry (PCP) and rate-controlled mercury porosimetry (RCP). The results show that the rock type of the Chang 6 sandstone reservoir is fine feldspar sandstone, and the main composition is calcite, chlorite and turbidite. The pore type is varied, mainly with residual intergranular pores and various dissolution pores, and the average pore diameter is mainly distributed at 20-50 μm. The reservoir porosity and permeability are poor. Micro-cracks are locally developed, and pore structure is very complex. Combined PCP and RCP indicate pore throat radius extends from nanometers to micrometers, but there are mainly two peaks, and the pore radius is mainly smaller than 2 μm. The oil content of Chang 6 sandstones is poor, mainly with oil spot grade, and oil is mainly distributed in the residual intergranular pores and dissolution pores. For the oil-bearing sandstones with industrial oil flow wells, the lower limits of porosity, permeability and pore throat radius are 7.5%, 0.15×10^-3 μm ^2 and 0.1 μm, respectively.