Geometry, Kinematics and Segmentation Characteristics of Strike-slip Faults in Halahatang area, North Tarim Basin, NW China: A Study Based on 3D Seismic Data

- Introduction

Strike-slip faults in the Tarim Basin have significant impact on reservoir formation and hydrocarbon accumulation. Halahatang oilfield in the north of Tarim Basin is a large carbonate oil field discovered in recent years. The main reservoir types are fracturing and karsting carbonate reservoirs controlled by strike-slip faults.

- Data and method

The seismic data used are acquired by Tarim Oilfield Company in 2010. The Eigen-structure coherency is used to identify the distribution of faults. The segmentation of strike-slip fault is discussed.

- Strike-slip fault characteristics

There are several groups of strike-slip faults trending Northeast and Northwest in this area. Five kinds of typical structural styles are founded such as Tulip/Palm tree structure and En-echelon structure(Fig. 1). On the plane, the master strike-slip faults were conjugate shear faults like chessboard, and secondary faults extending shortly intersected with the master faults at a small angle.

Judging from the age of rocks subjected to strike-slip dislocation and the structutal styles, the strike-slip faults had three epochs of activity in study area. In Late Ordovician, the faults were formed as conjugate strike-slip faults by pure shear. That was caused by a pulse of horizontal pressure along the north-south direction due to the closure of the West Kunlun ocean. In Late Permian, some NW trending Ordovician strike-slip faults were reactivated and generated normal faults in Late Paleozoic strata. The normal faults converged downward to the Ordovician strike-slip faults vertically. In Late Cretaceous, some NE trending Ordovician strike-slip faults were reactivated and en-echelon faults were formed in Mesozoic strata.

- Segmentation Characteristics of Strike-slip Faults

According to the difference of structural style and stress state in different parts of the strike-slip fault, the segmentation model of small-slip distance strike-slip fault is established. The end of the strike-slip fault is a stress divergence area, and most of them are horsetail structures. The interior of the strike-slip fault is composed of the translation section, the overlapped section, the branch fault section and the braided section.

The strike-slip fault systems controlled the distribution of hydrocarbon in Halahatang oilfield.