Relationship between Tanlu Fault and hydrocarbon accumulation in Liaozhong Sag, Bohai Bay, eastern China

Abstract

Tanlu fault (Liaozhong segment) goes straight through Liaodong Bay along NNE direction and it is divided into three segments, i.e., the northern segment, the middle segment and the southern segment, according to the differences in structural features. There are obvious changes in deposit thickness, sag structure, tectonic nature and other aspects of the layers. Tanlu fault is a special controlling factor concerning the reservoir formation in Liaozhong sag. First, its activities affect paleogeomorphology and paleogeographic framework and control the distribution of the sedimentary facies and then they proceed to control the distribution of the source rock and reservoir sand bodies. Second, its activities affect the formation and deformation of the structure, control the formation of abundant traps and cause the destruction of some traps. Third, its activities also affect the juxtaposition relation among the fault, the sand bodies and unconformity surfaces and control the function and efficacy of the three as the main hydrocarbon translocation system. In this paper the hydrocarbon reservoir formation process of JZ21-1, JX1-1 and LD27-2 oil and gas fields, the representatives of Tanlu strike slip fault zone are mainly analyzed. The modes of hydrocarbon reservoir formation can be generalized as follows—hydrocarbon source acts as “soil” and oil and gas as “nutrient”; hydrocarbon expulsion relies on “roots”; hydrocarbon migration relies on “trunks”; reservoir forms in “brunches” and the whole process follows the pattern that “hydrocarbon accumulates in strike slips and oil and gas reservoir forms like the growth of trees”.