陕甘宁盆地南部延长组低渗砂岩储层评价

RESERVIOR EVALUATION ON LOW PERMEABILITY SANDSTONE OF YANCHANG FORMATION IN SOUTH PART OF SHANGANNING BASIN

陕甘宁盆地是华北地台解体后独立形成的大型内陆沉积盆地。该盆地南部上三叠统延长组具“低孔、低渗、低产”的储集特点。通过研究储层孔隙结构，将该区延长组砂岩储层划分为５类：中小孔中细喉、小孔中细喉、小孔细喉、细小孔微细喉和微细孔微喉型。储层分类评价结果表明，前三类为有效储层，后两类为非有效储层；成岩作用是形成低渗砂体和次生孔隙发育的主要地质因素。进而应用模糊数学综合评判法定量预测了含油气有利区，并被生产实践所证实。

Shanganning Basin is a large inland sedimentary basin independently formed after Huabei platform disintegrates. Upper Triassic Yanchang formation in the south part of the basin has the characteristics of low porosity,low permeability and low production. By researching the reservoir pore structure, the sandstone reservoir of Yanchang formation is divided into 5 types such as middle-small aperture and middle-little throat, small aperture and middle-little throat, small aperture and little throat, tiny aperture and miniature throat as well as miniature aperture and miniature throat. Reservoir classificatory evaluation indicates that the former three typos are efficiency reservoirs.Diagenesis is the main geologic factors of formnig low permeability sand body and secondary pore development. The favourable oil-gas bearing area is qualitatively predicted by the use of fuzzy mathematics comprehensive evaluation.