An Ordovician carbonate reservoir in strike-slip structures producing from fault-associated fracture systems, 3D seismic region of Northern Shun 8 block (Tarim Basin)

Abstract

The fault system in the 3D seismic region of northern Shun 8 block (Tarim Basin) is mainly composed of NNW-SSE and NE-SW orientation faults. The No.7 fault zone in the NNW-SSE orientation extends linearly on the plane. It partially exhibits segmentation characteristics. According to the fault plane spread feature of the partial extensional section, the No.7 fault zone is the left-order left-lateral strike-slip fault. The SHB7 well on the No. 7 fault zone was drilled to the vicinity of the extensional section. The successive strike-slip stress field generated multiple sets of fractures in different orientations. The integration of 3D seismic, image logs and production logging analysis reveals the clustering of productive fractures around the fault zone. These open to semi-open production fractures are inconsistent with the tectonic stress state of the present day acting in this part of the Tarim Basin, indicating that the present-day tectonic play no role in production rate. The Build-up tests show three main types of responses: (1) A-type displays a radial flow and there is no test boundary for a longer period of time, (2) B-type displaying a short radial flow period followed by bilinear flow and (3) C-type is only related to bilinear flow. These three flow responses are linked with structural models of fault associated production fractures. Analysis of geological and production data indicates that the spatial distribution of productive fracture zones is primarily controlled by open fractures. A better understanding of the production system allows us to optimize the drilling location and select the appropriate well production zonees.