Hydrocarbon accumulation patterns of Moxizhuang oilfield,the Junggar Basin

This paper discusses hydrocarbon accumulation patterns of Moxizhuang oilfield of the Junggar Basin based on a comprehensive analysis of oil-water relationship,fault occurrence and hydrocarbon accumulation background.The reservoir of J1s2(2)(the lower second member of the Jurassic Sangonghe Formation) in Moxizhuang oilfield has a uniform oil-water system with a normal instead of inverted oil-water relationship.Seismic attributes of intervals with well-developed coal beds reveals that the previously interpreted major faults are artifacts resulted from seismic reflection of the coal seams,and no large faults are developed in the Sangonghe Formation,no fault-sealing trap conditions exist.Hydrocarbon accumulation conditions and distribution characteristics are different in J1s2(1)(the upper second member of the Jurassic Sangonghe Formation) and J1s2(2) reservoirs.The J1s2(1) reservoirs are developed in underwater distributary channel sandbodies of meandering river deltaic front facies,with the favorable reservoirs laterally being in strip distribution.In contrast,the J1s2(2) reservoirs are developed in distributary channel sandbodies of braided river delta facies,with the favorable reservoirs laterally in continuous distribution.The Moxizhuang oilfield is a structural-lithologic reservoir that is controlled by both structure and sedimentary microfacies and is still in the post-tilting dynamic adjusting process.There exists a uniform oil-water contact in J1s2(2) with occurrence the same as that of the up-dipping sandbody.