The Sedimentogenesis And Reservoir Characterization With Coal Measures Of Middle-Lower Jurassic In Hongshanzui Area Of Junggar Basin

The Hongshanzui area is mainly oil-gas block of exploration and development in Junggar Basin,and the average production is 300 000 tons/year in the past five years.By the end of 2017,the area has proven geological reserves of 5136.95 million tons,in the middle-lower Jurassic,about 3.11 million tons were proved,accounting for about 6.1%.There are 3 oil and gasreservoirs have been in the middle and later stages of development.Its production is decreasing year by year,and new development blocks are urgently needed to realize the purpose of stable production.The main scientific problem facing this challenge is the relationship between coal formation and sand body in different periods is unknown,the favorable storage sand body can be spread under sequence stratigraphic framework is not clear;the mechanism and controlling factors are controversial and favorable exploration targets need to implemented urgently.Hence,based on previous research results and exploration status,use of rock,logging,seismic and outcrop data,the characteristics of two coal-bearing formation groups were analyzed,the reason of stable continuous and intermittent coal seam are proposed;a comparative method of sedimentary microfacies orientation was used,the genesis and stacked of sand body of the two kinds of sedimentary systems are clarified by cross section;the mechanism and controlling factors are discussed;A quantitative method combing rock-logging-seismic,the sedimentary parameters of 8 periods were mapped according to the base level cycle,the distribution and evolution of the sedimentary facies are reproduced;On the base of characteristic of distribution in different period,the evaluation index of favorable reservoir is determined;Choose a method of weigh quantities techniques,the favorable zones of 8 periods were evaluated,and then based on composite and stacked comprehensive analysis,it is pointed out that CH7209 and hong68 well area are favorable exploration blocks,and the next direction of exploration is directed.Its main achievements and innovations are as follows:1)Based on the theory of sequence stratigraphic,the response of stratigraphic and boundary of the Upper-lower Jurassic,five kinds of gravel,sand body lithofacies,three kinds of mud stone lithofacies and one coal lithofacies are divided,eight genetic sequence units can use to descript depositional genesis is established,the sedimentary facies of core-logging-seismic integration is constructed;two kinds of sedimentary systems are identified,the fan delta in Badaowan Formation and the braided delta in Xishanyao Formation.2)The “four indicators” which reflect the structural and cause of gravelly sand stone(the lithological characteristics,sedimentary sequences,MPS/BTh and cumulative grain-size distribution curve)are put forward as recognition marks.There are two kinds of gravelly sand stone in effective quantitative: tractive current and gravity flow.3)The distribution characteristic of coal in two periods were discussed.The lower Jurassic(badaowan Formation)has the characteristic of stable continuous distribution and unstable interrupted distributions in middle Jurassic(xishanyao Formation).And the former is contacted with roof and baseborard,the stabilization controlled by angle and the continuity is controlled by climate and balance state.Three kinds of stacked sand body are identified by a comparative method of sedimentary microfacies orientation method by the section.4)The distribution of sedimentary parameters in 8 sequences are mapped by the methods of well-seismic,multivariate statistics.the distribution boundary of the sand body is determined by the normal distribution of the mean square root,the sedimentary patterns and evolution of eight half base level were reconstructed.The characteristics are defined,during the rise base level,the distribution of the fan delta in Badaowan Formation is characterized by “great plains and small front” and sand body is distribution of “carpet type”,whereas during descend base level,is characterized by “small plains and great front”,and sand body is distribution of “strip”.During middle Jurassic(Xishanyao Formation),the distribution of sand body is characterized by “channel developed” and sand body is “braided”.5)A model of porosity property interpretation for the pore structure of reservoir is established by the represent analytical data.Used the grey correlation analysis,according to the score of quantitative evolution(Q),the reservoir is divided into five categories,the ?class for the high quality reservoirs which Q is between 1~0.6,it is located between the delta plain and front,and develop the genetic conglomerate of traction current,the distributary channel and braided bar sand body;the ?class for the favorable reservoirs which Q is between 0.6~0.5,it is located delta plain,between the interior and exterior zone,the genetic conglomerate of gravity current,mouth bar and braided channel bar.? class for the general reservoir which Q is between 0.5~0.4,where located in the exterior of fan delta front and overbank sand body,the underwater distributary channel sand body is developed.6)Combining the characteristics of the known reservoir distribution,using the mapping of stacked “the porosity,facies,the evaluation of reservoir property”,the favorable area is forecasted,and it is suggested to explore the CH7209 well area and Hong 68 well as soon as possible.