Comprehensive And Quantitative Evaluation On Controlling Of Fault To Oil And Gas Accumulation In Napu Depression

On the basis of using geology,seismic,logging and various kinds of analysis material,combining with regional geological background,the structural characteristics and the formation and evolution history of faults in Nanpu Depression of Bohai Bay Basin are systematically analyzed,and the fault system is divided.On the basis of the oil and gas characteristics and oil-water distribution characteristics of fault traps,the formation mechanism and accumulation ability of fault traps and the controlling of faults to oil and gas accumulation is summarized.Finally the evaluation and optimization of the target fault traps will be conducted.Nanpu depression is consist of three structural layers:basement,faulted basin and depression basin.The formation and evolution history of faults undergoes three periods of tectonic deformation:Es2+3 Sedimentary period,Es1-Dongying group sedimentary period,and Guantao group-Quantemary sedimentary period.Six cases of fault system are divided:early expending fault system(? type);middle strike-slip expending fault system(? type);lately tenso-shear fault system(?type);early expending and middle strike-slip expending fault system(? type);middle strike-slip and lately tenso-shear fault system(?type);early expending,middle strike-slip expending and lately tenso-shear fault system(VI type).The controlling of faults to oil and gas accumulation is manifested in the following:?Controlling of faults connected sourcerock to the ability of providing hydrocarbon.From the number of fault traps bearing hydrocarbon,the fault traps whose faults are connecting the two sets of sourcerock as the faults connected sourcerock are the largest,only connecting one set of sourcerock as faults connected sourcerock are the second largest and not containing faults connected sourcerock are the least.?The anticlinal structure which is formed by the activity of faults is the favorable part for oil and gas accumulation.The hydrocarbon accumulations in Nanpu depression are mainly located in highest and also higher position of the faulted structural belt.Among them,the fault traps with anticlinal structural belt are the most,the second is those with fault-step belt and the fault traps with synclinal structure belt are the least.? The destroy of faults to cover controls the hydrocarbon distribution.When the fault-connecting thickness of the Ed2 mudstone caprock is less than 90?95m,the hydrocarbon distributes in the up and down part of it.When the fault-connecting thickness of the Ed2 mudstone caprock is more than 90-95m,the hydrocarbon only distributes below the caprock.When the fault-connecting thickness of the Ng3 volcanic caprock is less than about 130?150m,the hydrocarbon distributes in the up and down part of it.When the fault-connecting thickness of the Ng3 volcanic caprock is more than about 130?150m,the hydrocarbon only distributes below the volcanic caprock.?The lateral seal ability of faults controls the filling degree of oil and gas in the trap.The lateral seal ability of faults developing in the beach structure units is stronger than it developing in the land structure units.This decides the trap validity in the beach structure units is better than it in the land structure units.In vertical,the oil-bearing probability of faults has a good correlation with the lateral seal ability of faults.That is,the stronger the lateral seal ability of faults of the horizon is,the higher the average height of oil column it contains.The lateral seal ability of faults in traps below the regional cover is stronger than any other horizon,and the average height of oil column it contains is also higher than any other horizon.On the basis of defining the controlling of faults to oil accumulation in Nanpu depression,the comprehensive and quantitative evaluation method on controlling of fault to oil and gas accumulation is established by using the method of fuzzy mathematics and the target fault traps are evaluated and optimized.The Guantao group of the well NP4-9N and NP4-39W,the Edl member of the well NP4-51N and NP4-20N in the east of number 2 structure and the Guantao group of the well NP3-1 in the number 3 structure have the advantage of oil and gas accumulation,as the first fault trap to the next step of exploration.