FAULT CHARACTERISTICS OF HEISHANDUN AREA OF THE ERDOS BASIN AND ITS CONTROL OF OIL AND GAS

There are two overlying structural systems in Heishandun working area of the Erdos Basin.They borders at around reflector T8 as show on seismic data.Among which the upper system is the target.It can be divided into three level fractures in terms of scale.The primary and second order fractures are mainly reverse faults extended down to the source rocks in south to north direction.The third order fractures are mostly intrabed normal faults.Faults and local structures were formed predominantly at early Yanshanian,and hydrocarbon expulsed at late Yanshanian.The primary and second order fractures,which connect oil sources and control local structures,play an active role in the accumulation of hydrocarbon.In combination with postdrill assessment,it is concluded that local structures are the controlling factor to the formation of hydrocarbon reservoir,and faulted anticlines are the favourable places for hydrocarbon accumulation.The primary and second order fractures play the main role in the initial allocation of hydrocarbon,whereas the third order intrabed fractures play an important role in the reallocation of hydrocarbon.