Sedimentary characteristics of Chang 2 and its relationship with sand body superimposition in Resiwan oil region

Abstract

On the basis of core observation, logging interpretation and previous research results, the sedimentary microfacies characteristics of each sub layer of the Chang 2 oil-bearing formation in the Resiwan oil area of Zichang Oilfield and the superimposed relationship of sand bodies are studied. The results show that the Chang 2 member in the Resiwan oil area of Zichang oilfield belongs to braided river deposits, and the study area mainly develops sedimentary microfacies such as river island, channel lag deposits and floodplain. The vertical superimposition types of sand bodies in Chang 22 oil-bearing formation are multilayer superimposition sand bodies and massive thick sand bodies, which are also the dominant sand body combination of oil-bearing reservoirs in the study area. Chang 21 oil-bearing formation is dominated by thin interbeds. Flood plains are developed at the top of Chang 23 oil-bearing formation, and massive thick sandstone is developed at the middle and lower parts, but the horizontal continuity is poor. Horizontally, the sand bodies of Chang 22 oil-bearing formation are mainly overlapped horizontally and cut laterally, which improves the connectivity of the sand bodies to a certain extent. Chang 21 and Chang 22 are mostly isolated sand bodies, and the sand bodies are wrapped in mud, resulting in poor oil and gas display. The contact pattern of sand bodies in the study area is mainly affected by sedimentary microfacies and river water volume.