Classification and evaluation of tight sandstone reservoirs based on diagenetic facies: a case study on Chang 6 reservoir in the center-west Ordos Basin

Abstract Tight sandstone reservoirs dominated by are developed in the Chang 6 oil layer group of Yanchang Formation central-western part Ordos Basin. Featuring lacustrine delta facies, formation center-west area Basin shows an increasing petroleum reserve expectation. Its exploitation practice, however, has many problems caused tight reservoir features. According to diagenetic and pore analysis, facies study grouped into four types: chlorite-film-intergranular-pore, feldspar-dissolution, clay-cemented-micropore, carbonate-cemented-tightness for their obvious differences mineral feature evolution. By introducing comprehensive classification parameter synthesized from 9 other parameters, quality is divided up levels: I(F eci > 1), II(3 ≤ F 7), III(-2 3), IV(F -2). The division matches well with group. To decide type all wells, logging data utilized Fisher discriminant method, which obtained a good performance. method enables analysis expanding wells samples, helpful area.