Characteristics and distribution of fault−controlled carbonate reservoirs in Yijianfang Formation of Yueman area, northern Tarim Basin

This paper is the result of oil and gas geological exploration engineering.

Objective The carbonate reservoirs of the Ordovician Yijianfang Formation are developed in Yueman area, south of Tarim River in Halahatang oilfield, Tarim Basin. The exploration and development results show that the high−producing wells are mainly distributed along four strike−slip faults in the area, and the oil and gas production along the fault zone is different, with strong heterogeneity, and the reservoirs are obviously controlled by faults. Therefore, it is of great significance for oil and gas exploration and development to clarify the characteristics and distribution regularities of fault−controlled reservoirs.

Methods In this paper, based on drilling logging data, cores data and 3D seismic data, the petrological characteristics, reservoir types and development regularities are analyzed, and the coupling relationship between high−quality reservoirs and strike−slip faults is discussed to clear the distribution regularities of such fault−controlled reservoirs.

Results The reservoir rock types of Yijianfang Formation in the area are mainly bioclastic limestone, arenaceous limestone, granular limestone and micritic limestone, with low porosity and permeability. According to the types of reservoir space, the reservoirs can be divided into four types: cavernous reservoirs, vuggy reservoirs, fractured reservoirs and fractured−vuggy reservoirs. The cavernous reservoirs develop vertically along the main fault, the vuggy reservoirs, fractured reservoirs and fractured−vuggy reservoirs are banded distributed along the fault.

Conclusion The structure of strike−slip faults controls the distribution of high−quality reservoirs, and the reservoir stratums in Horsetail, en echelon and overlap sections of faults are the best developed, the oblique intersection sections of branching faults are fair developed, while the linear sections are poorly developed. On this basis, the reservoirs in the superposition area of high−energy facies belts are better developed than those in the non−superposition area.