Multiphase of the meteoric diagenetic environment of carbonates and its relationship with reservoir: a case study of the Jingxi Area in the Ordos Basin, China

Abstract

The meteoric diagenetic environment has multiphase characteristic, but the scales of the reservoirs in different meteoric diagenetic environments have been rarely considered. On the basis of geological and well-logging analyses, three distinct phases of the meteoric diagenetic process were observed in the Ordovician of the Jingxi area in Ordos Basin, China. The phreatic zone formed in the first phase is partially preserved, whereas those formed in the second and third phases are completely retained. Strata in the western (close to the Central Uplift Belt) and eastern parts underwent bedding-parallel meteoric dissolution and cross-layer meteoric dissolution, respectively. The distributions of the dissolution formation thicknesses in two successive phases of the meteoric diagenetic process exhibit complementarity at the same positions in the plane. The favorable reservoirs at the top of the Ordovician are mainly distributed in the western parts. The second phase of the meteoric diagenetic process is most conducive to the formation of carbonate reservoirs. By dividing and comparing the multiphases of the meteoric diagenetic environment of carbonates, the favorable karst reservoirs can be predicted in each phase.