Seismic-geological Comprehensive Research On The Effectiveness Of Compact Glutenite Reservoirs In The West Of Chezhen Sag

Chezhen sag,characterised by the narrow-steep type,is located in the northwest of Jiyang depression which is in the Bohai bay basin.About 3 types of fans were developed successively controled by the northern fault(named Chengnan fault)during Shahejie sedimentary period,the reservoir of fans have the strong heterogeneity and the poor sorting because the sediments derived from near provenances and deposited in the sag directly.Chexi area,about 900km~2,is the west part of Chezhen sag,the exploration practice shows that there are a low exploration level relatively in the deep,and the effectiveness of the compacted reservoirs is one of the key geological problems what restricted to the glutenite petroleum exploration.In this paper,determined the lower effectiveness limits as well as the main control factors of reservoirs'effectiveness based on the distribution characteristics of glutenite reservoirs and combined with the data of drilling and the analysis of test data.By using the theory&methods of geology&geophysics,studied the effectiveness of deep-glutenite reservoirs in the steep slope belt,and predicted the zone of favorable reservoirs.The main deposits facies in formation of Shahejie are fan delta,nearshore subaqueous fans and turbidite fans are the decond.Analyzing the geological meaning of the seismic events by synthetic seismogram calibration method,combined seismic and geological data,the key geological interface has cleared,it is very important to understand the spatial distribution of glutenite reservoirs.The analysis of thin section,results of core observation show that the feldspathic lithic conglomerate and lithic conglomerate are main rock types of glutenite reservoirs in the deeper layers in formation of Shahejie,including part of feldspathic lithic sandstone.Some primary pores,tectonic fractures as well as a certain number of dissolution pores are the main reservoir space types,and reservoir properties becomes poor vertically with the increase of buried depth but developed several secondary pore zone at some depth.By comparing and analysing,confirmed that sedimentary faces,property of bedrocks,tectonic fractures and property of flow underground are the main factors which mainly controled the development of favorable glutenite reservoirs in middle-deep layer.Based on the actual data,calculated the lower effective limit of glutenite reservoirs using the well test method,the limits are the function of depth(stratum)and sedimentary facies,and establish a quantitative prediction model innovatively,and the reliability was verified by the practical data.Based on the analysis of the geological data,comparing the similarity of known effective reservoirs and unknown in geology and seismic attributes,established the seismic-geological prediction method of effectiveness of glutenite reservoirs.Taking the third sub member of Shahejie formation as the research layer,and calculated reservoir properties by linear regression method of seismic attributes which related to the reservoirs'effectiveness,and predicted the effective glutenite reservoirs distribution area,divided the area into two types,i.e.type A and type B.Finally,combined with the distribution and evolution characteristics of hydrocarbon source rocks,obtained the favorable exploration target.The study above provides a more reliable geological basis for exploration in the West part of Chezhen sag.