Configuration Of Fault-sand And Its Controls On Hydrocarbon Accumulation In The Chengbei Fault Terrace Zone Of The Huanghua Depression

In the terrestrial rift basins,faults and sand bodies are the main essential factor of hydrocarbon migration network.In order to explore the mechanism of hydrocarbon migration and accumulation in the Chengbei fault terrace zone under the control of fault-sand configuration transportation conditions,the fault-sand configuration(types division,characteristics,distribution law of fault-sand configuration)and the static and dynamic elements of oil-gas reservoir(basic geological characteristics,fluid temperature and pressure,forming period of oil-gas reservoir)were studied by the comprehensive research method of petroleum geology,fluid inclusion homogenization temperature method,hydrocarbon migrating pathways simulation by Trinity in this paper,based on the fine interpretation of seismic profile,sand body inversion profile,drilling and logging data,geochemistry and analytical test data.The dominant hydrocarbon migrating pathways in each layer of the fault terrace zone,the characteristics of the fault-sand configuration and its relation to types,hydrocarbon migration process,distribution and hydrocarbon accumulation of reservoirs were revealed.Based on these,the controls of the fault-sand configuration on hydrocarbon accumulation in the study area were summarized,and the forming model of oil-gas reservoir model was established.Three conclusions were made in this paper.(1)The faults can be divided into three types according to the different functions in the process of hydrocarbon migration and accumulation,including oil source faults,transport faults and adjustment faults,the fault-sand configuration in the fault terrace zone can be divided into three types on these basis,including configuration of oil source faults and multiple sets of sand body superposed vertically,configuration of transport faults and sand body forward or reverse ladder type,configuration of adjusting faults and sand body "Y" type.(2)the oil and gas from Qikou main depression was enriched to the Zhangdong-Hai4 fault structure,and the oil and gas from Qinan sub sag was enriched to the Zhaobei fault terrace zone and high part of the Yangerzhuang slope.(3)The controlling function of fault-sand configuration on hydrocarbon enrichment is mainly reflected in three aspects:(1)Controls the types of oil and gas reservoirs: the configuration of oil source faults and multiple sets of sand bodies mainly controls the formation of Structural-lithologic and fault block oil-gas reservoirs,and the configuration of transport faults and sand bodies in a terrace forward or reverse direction controls the formation of fault block,fault nose and composite oil-gas reservoirs,and the configuration of regulating faults and sand bodies in a "Y" shape controls the formation of fault block oil-gas reservoirs;(2)Controls the hydrocarbon migration process: The configuration of oil source fault and large zone sand body at the fault root connects the deep hydrocarbon source.during the activity period of oil source fault,oil and gas migrate along the fault to the shallow layers,and then accumulate in the high part of fault terrace zone for enrichment after a long distance migration.The terrace-by-terrace vertical or reverse configuration of transport fault and sand body provides the terrace-byterrace vertical and lateral migration channel for hydrocarbon,and the configuration of adjusting of fault and sand body plays a role of readjustment and distribution in the process of hydrocarbon accumulation;(3)Controls the position of hydrocarbon migration and accumulation: When the probability of fault migration f is more than 50% and the sandstone thickness to total formation thickness ratio is more than 0.5,the fault-sand configuration is believed to be completely fluid connected.In the shallow layer,oil and gas migrate from the deep layer to the shallow layer along the oil source fault,and can migrate to the high part of the fault terrace zone in a long distance;in the middle-shallow layer,oil and gas can migrate along the transport fault,and the sealing property of the transport fault controls the hydrocarbon accumulation;And in the middle-deep layers,the degree of oil and gas accumulation is positively related to the sandstone thickness to total formation thickness ratio.Three types of fault-sand configurations were successively distributed from south to north,forming the characteristics of "relay-type" migration and accumulation model.