A study on reservoir space type of Ordovician ultra-deep marine carbonate reservoir in T-Sh Oilfield, Tarim basin

Abstract

Abstract The T-Sh reservoir is a typical ultra-deep marine carbonate reservoir with numerous large strike-slip faults. While the large strike-slip faults are preferred as the drilling target because it has previously been understood that they are the main reservoir space. In the Sh-1 and Sh-5 fault zones, the application outcome of this understanding is effective, but invalid in the Sh-7 fault zones. Therefore, the permeability of Ordovician Yijianfang Formation faults in the Sh-5 and Sh-7 fault zone have been analyzed by using geomechanics theory and the finite element method. Meanwhile, the reservoir space types in various T-Sh reservoir regions in conjunction with mud loss during drilling have been evaluated. It is found that in Sh-1 and Sh-5 fault zones, the main reservoir space is the fault, and the critical Ts (slip tendency coefficient) of the Sh-5 fault zone is 0.2. However, it is of high-permeability micro-fracture groups-type in the Sh-7 fault zone reservoir. This discovery explains why the Sh-7 fault zone cannot benefit from the development experience learned from the Sh-1 and Sh-5 fault zones. The breakthrough of these results could serve as a reference for the T-Sh oil field's further exploration and development.