Control of differential tectonic activities on carbonate reservoirs in craton basin: A case study of the subsalt reservoir of Majiagou Formation in Ordos Basin

Carbonate rocks in China tend to have the characteristics of the older development period, deeper burial, and stronger later diagenetic transformation, which leaves a large space for the study of high-quality carbonate reservoirs and their main controlling factors in China. During the sedimentary period of Majiagou Formation in the Ordos Basin, the basin witnessed changing from tension to longitudinal compression, which induced a series of tectonic activities. To explore the influence of different tectonic activities on the subsalt deposition of Mawu Member in Majiagou Age, based on the previous studies and under the guidance of carbonate sedimentology, two-dimensional seismic profiles in the study area were analyzed, and differential tectonic activities were summarized. Combined with the analysis of seismic facies and sedimentary facies in the sub-salt sedimentary period of the Mawu Member, the influence of differential tectonic activities on the grain beach reservoir were depicted. As a result, the following understandings are obtained: a. four types of seismic facies have been identified in the study area, corresponding to different types of sedimentary facies, of which the grain beach facies is a good reservoir in the study area; b. there are three types of tectonic activities in the basin, basement faults (sag troughs), synsedimentary faults and uplifts; and c. based on the matching analysis of different types of tectonic activities and grain beach reservoirs, the control of differential structural activities on the development and distribution of this kind of carbonate reservoir is finally obtained, and its action mode is summarized. Finally, granular beach reservoirs are divided into fault-controlled reservoirs and uplift-controlled reservoirs.