Effects of strike-slip faults on the differential enrichment of hydrocarbons in the northern slope of Tazhong area

Abstract

A series of NE strike-slip faults are developed in the northern slope of Tazhong area. Activities of these strike-slip faults generated a great deal of fractures and enlarge reservoir space, form massive dissolved pores and carities by deep thermal fluid from faults, which improves reservoir property significantly and increases development depth of karst reservoirs. Studies on source rock-reservoir relationship, active stages of faults and trace element distribution of crude oils indicated that strike-slip faults are an important pathway for hydrocarbon migration in the Tazhong area, together with unconformity of the Yingshan Formation, form a Lower Ordovician hydrocarbon transportation framework that controls hydrocarbon redistribution. The northern slope of the Tazhong area can be divided into twenty structural blocks with extension direction of major strike-slip faults and thrust faults. Each block has a normal differentiation of oil, gas and water. The extent of hydrocarbon enrichment in individual blocks has a certain correlation with distance away from strike-slip faults, smaller distance away from strike-slip faults, better property of reservoirs and higher extent of hydrocarbon enrichment. In addition, different blocks show obviously different characteristics of hydrocarbon enrichment.