| Boli basin is an important mesozoic basin in eastern of Heilongjiang Province,the north side of basin is erosion boundary,The southwest boundary is the Yilan Boli fault,the south boundary is Xingnong-Xingkai fracture,Southeast boundary is peide fault.The basement is mainly composed of Jiamusi and xingkai crustal blocks,the basin can be divided into western,central and Eastern three depressions,the geological structure is very complicated.In this paper,the eastern depression of Boli basin area is the main research region,the lower Cretaceous Chengzihe and Muling formation are the main research objectiveinterval,carrying out a series of petroleum geological characteristicsincludes sedimentary characteristics,characteristics of source rocks,reservoirsand cover characteristics,source reservoir cap assemblage characteristics.Through field geology survey and well data study,sedimentary facies of the lower Cretaceous Chengzihe Muling formation in the eastern depression of Boli basin have been recognised(fan)delta facies,lacustrine facies,submarine facies three types,eight sedimentary subfacies and nineteen sedimentary microfacies are further identified.During the deposition of Chengzihe formation is mainly(fan)delta deposit,the lithology is mainly sandstone,meanwhile Semi deep lacustrine mudstoneis developedin the sedimentary formation,depocenter is in the vicinity of Bo 1 wells in Boli basin.lacustrine mudstone is widely developed in the period of Muling formation sedimentary,andmudstone large-area expose in research area,semi deep lake facies are dominant in the vicinity of ZK2,ZK3 wells in Boli basin,also the two wells are the depocenter of this period,the developing process of lake facies accompanies with subaqueous fan deposition.In the eastern depression of Boli basin,the mudstone of lower Cretaceous Chengzihe Muling formation are widespread,and its thickness is bigger,mudstone is the main source rock series in the research area of Lower Cretaceous,according to the analysis of hydrocarbon source rock tests,organic matter abundance showed Chengzihe and Muling formation belong to middle source rocks,organic matter type gives priority to type II 2,type ?1and type ? are developed in a small amount;organic matter maturity showed the thermal evolution degree is relatively high,most of the organic matter are in the over-mature stage,showing that source rock of Chengzihe formation and Muling formation in the lower Cretaceous has large gas potential,mainly to gas,oil generation as a supplement.Reservoir of Lower Cretaceous Chengzihe and Muling formation in the study area is mainly(fan)delta sandstone,sandstone rock types are mainly lithic feldspahtic sandstone,quartz content of detrital composition is lower,feldspars are mainly plagioclase feldspar,debirs are mainly volcanic debris and sedimentary rock debris,also developed a few metamorphic debris,chinkare mainly argillaceous matrix,sandstone compositional maturity and structural maturity are low,the comprehensive analysis of Chengzihe formation belongs to the middle diagenetic stage B,Muling formation belongs to the middle diagenetic stage A.The reservoir of Chengzihe formation and Muling formation is mainly secondary pore,porosity and permeability of sandstone are poor,belonging to extra low porosity,ultra-low porosity and ultra-low permeability reservoir.Shallow lacustrine subfacies mudstone of Chengzihe and Muling formationof Lower Cretaceous in the study area develop widely during sedimentary period,mudstone can be used as a major regional seal.In addition,tuff developed in the basin can be used as the local seal.The study area of Lower Cretaceous Chengzihe and Muling formation source reservoir cap assemblage relations have mainly three types,one is self generating and selfstorage type,Muling formation mudstone can be used as source rock,Muling formation sandstones in the upper part can be used as reservoir,Muling formation mudstonein the upper part can be used as cover,this combination relations is an important form of source reservoir cap assemblage in this area,the second kind of source reservoir cap assemblage relationship is upper generated and lower reserved type.The Muling formation mudstone can be used as source rocks,Chengzihe formation sandstone can be used as reservoir,Muling formation mudstone can be used as cover,the third kind of source reservoir cap assemblage relationship is lower generated and upper reserved type,Chengzihe formation mudstone as source rocks,Muling formation sandstone plays the role of reservoir,Muling formation mudstone can be used as cover. |
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