Prediction Of Favorable Fault Traps For Hydrocarbon Accumulation Of Members 2 And 3 Of The Dongying Formation In Northern Liuchu,Bohaiwan Basin

The region of northern Liuchu is of key importance to hydrocarbon exploration in Raoyang Depression,Jizhong Subbasin,Bohaiwan Basin,with Members 2 and 3 of the Dongying Formation（hereinafter referred to as Ed₂ member and Ed₃ member）primarily being petroliferous strata.The reality that oil and gas having been found there mainly lie in the northern and central fault traps,yet less in the southern ones,demonstrates the spatial effectiveness of hydrocarbon accumulation by fault traps plays a dominating role,apart from whether source rocks could timely supply or there are quality sandstone bodies.In other words,only when fault traps happen to develop in hydrocarbon migration pathways by fault-sandstone body configuration,can oil and gas be captured and then grow into reservoirs,enabling explorers to find;otherwise,hardly.It,therefore,is evident that such spatial effectiveness has a decisive impact on the understanding of hydrocarbon distribution and the guidance on further exploration.Part of the college-enterprise cooperation scientific project,Research on the hydrocarbon migration system and its reservoir forming contribution,and favorable exploration zones in petroliferous Jizhong Sag,from Petro China Huabei Oilfield Company,the current work concentrates on northern Liuchu.The spatial effectiveness of hydrocarbon accumulation by fault traps of the Ed₂₊₃ members in this region,and its distribution,are figured out by coupling hydrocarbon migration pathways by fault-sandstone body configuration with fault traps development,lots of information and materials taken into account,namely geological data,geochemical data,seismic data,mud-logging data,well-logging data,well testing data,formation testing data and the like.In addition to the perception of oil and gas distribution of target formations,the thesis expounds on how such effectiveness dominates the hydrocarbon accumulation,by which predictions of favorable fault traps for further exploration are made.This research brings about 7 dimensions of achievements,i.e.（1）The Ed₂₊₃ members in northern Liuchu have abundant dominant hydrocarbon migration pathways by oil source faults,excluding F9 and F16 oil source faults in the Ed₃ member,and F8,F9,and F16 in Ed₂.（2）It is basically consistent in dominant hydrocarbon migration pathways and their distribution by sandstone bodies of horizons of the Ed₃ member in northern Liuchu,while there is a great difference in Ed₂.More precisely,the lower part of the Ed₃ member（hereinafter referred to as Ed₃^x horizon）has 38 dominant hydrocarbon migration pathways,the middle part（hereinafter referred to as Ed₃^z horizon）has 39,and the upper part（hereinafter referred to as Ed₃^s horizon）39.Yet,the lower part of the Ed₂ member（hereinafter referred to as Ed₂^x horizon）has 32 ones,while the middle part（hereinafter referred to as Ed₂^z horizon）has 15 and the upper part（hereinafter referred to as Ed₂^s horizon）28.（3）Hydrocarbon migration pathways by fault-sandstone body configuration are,rich in the Ed₃ member in northern Liuchu,but less-developed in Ed₂,whose number of each member from the bottom up in the former formation is respectively 20,22,and 21,while 16,6 and 17 in the latter.（4）Fault traps development positions and their quantity are great in all horizons of the Ed₃member in northern Liuchu,mostly located in the core of the collapse anticline,with only a handful in both eastern and western sides.Fewer fault traps,nevertheless,appear in horizons of the Ed₂ member–some lie in part of the core of the collapse anticline in the northern part of the target area,and others are widely found in the south.（5）More favorable fault traps for hydrocarbon accumulation exist in the Ed₃ member in northern Liuchu,than in Ed₂.There are18,20,and 17 favorable ones respectively in the Ed₃^x,Ed₃^z,and Ed₃^s horizons,but 9,4,and10 in Ed₂^x,Ed₂^z,and Ed₂^s.（6）Favorable fault traps for hydrocarbon accumulation of the Ed₂₊₃members in northern Liuchu,impose a rule on oil and gas distribution,which,or rather,turn out in and around these favorable fault traps,where ClassⅠones,rather than ClassⅡ,are more likely to indicate greater oil and gas possibilities.（7）A total of 30 favorable fault traps of the Ed₃ member in northern Liuchu for hydrocarbon exploration are determined,including18 ClassⅠones mainly in the central region,and 12 ClassⅡones chiefly in the western part.In the meantime,14 are figured out in the Ed₂ member,with 6 ClassⅠfavorable fault traps primarily in the central region,and 8 ClassⅡones in the southern part,scatteredly.In a nutshell,these research findings and deep understanding are of vital reference value to further hydrocarbon exploration of the Ed₂₊₃ members in northern Liuchu.