Abstract: Characterization of strike-slip faults and their implications for hydrocarbon accumulation are highlights of structural and petroleum geology. In this paper, we conducted a combination study of outcrop survey with seismic profile interpretation of the Dashuluogou strip-slip fault to further understanding such a fault in northwestern Junggar Basin, aiming at re-characterizing the structural property and boundary of the fault. We then addressed the implications for hydrocarbon accumulation through additional analyses of oil layer occurrence and oil property and geochemistry. The results show that the Dazhuluogou fault has clear strike-slip characteristics. At its western termination, the fault line is straight and fault plane is steep with well developed lateral scratches according to outcrop survey. At the eastern end, according to seismic profile interpretation, horse tail and flower structures are developed in lateral and vertical directions, respectively. These new insights allow us to re-characterize the fault boundaries: the Daerbute fault and Well Datan 1 are the western and eastern boundaries, respectively, and the total fault length is approximately 80 km. The Dazhuluogou fault has influence on hydrocarbon migration both laterally and vertically that oil and gas pools accumulate in passive walls laterally and in “beaded” form vertically—possibly a general feature for such faults. Thus the passive walls of a series of strike-slip faults in the study area should be further explored.

Key words: strike-slip fault, horsetail structure, flower structure, fault-controlled hydrocarbon accumulation, Dazhuluogou fault, northwestern Junggar Basin