Characteristics of strike-slip fault-related fractures and their controls on reservoir in Halahatang area, northern Tarim Basin

ABSTRACT: The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×109 t, the fault-related fractures are important for hydrocarbon accumulation. In this paper, the basic parameters such as density and width of fractures are counted and classified, and the effects of fractures on reservoirs are analyzed. The results show that: (1) Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship. (2) Fracture density, width, aperture, and dip angle vary in different wells, but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone. In addition, oil and gas wells with high production mainly concentrate in the inner unit. (3) The infilling materials and degree of fractures vary. Fractures formed in the early stage are more filled and less open, while the fractures formed in the late stage are relatively less filled and more open. (4) Fractures improve porosity to a certain extent but greatly increase permeability, especially in the inner zone of fault damage zone with large quantity, multiple inclinations, less filling and large width. These features contribute to the formation of a higher-quality reservoir, further improving oil and gas production. This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs, and points out that fault damage zone, especially the inner zone of the fault damage zone, is the potential goal for oil and gas exploration.