Description of the reservoir along strike-slip fault zones in China T-Sh oilfield, Tarim Basin

The reservoir depth of T-Sh oilfield in Tarim Basin is more than 7500 m, which is a typical deep carbonate fault-controlled reservoir. The S-1 and S-5 fault zones experienced multi-stage tectonic movements and developed complex fault-fracture systems. Based on geometry and dynamics, the evolution characteristics of faults are analyzed; the permeability of strike-slip faults in the middle and lower Ordovician carbonate strata drilled through in S-5 fault zone is studied by comprehensively using core observation, imaging logging, 3D seismic data, and drilling historical data, taking wells F-1 and F-10 as examples. It is found that the fault-fracture system is the main reservoir space and fluid migration channel in the reservoir. A large mud loss will occur when drilling high permeability faults. High production can be obtained after conventional well completion, otherwise, it is difficult to get production. In this paper, slip tendency coefficient is used to quantitatively characterize the permeability of fractures in T-SH ultra-deep reservoir. Based on the one-dimensional geomechanical model and three-dimensional geological structure model of typical wells, the slip tendency coefficients of different parts of the fault-fracture system are calculated using finite element numerical simulation method. Compared with the historical data of drilling in S-1 and S-5 fault zones, it is found that the slip tendency coefficient is positively correlated with mud loss. The results show that the critical slip tendency coefficient of the S-5 fault zone is 0.3, and that of the S-1 fault zone is 0.2. This study provides a new idea and method for the prediction of geological desserts and well trajectory design in the T-Sh reservoir.