临北地区位于惠民凹陷中央隆起带中部,针对该区沙三中亚段基山砂体的储层类型、圈闭规模及储层有效性不清等问题,从烃源条件、储层物性、沉积相展布以及构造特征等方面入手,通过钻井和试油成果资料,综合应用地质、地化分析和地球物理研究手段,剖析了油气成藏条件及主控因素.结果表明,紧邻的临南洼陷沙三段优质烃源岩是临北基山砂体的主要来源,和区内各期砂体在时空上的良好配置是油气藏形成的基础;区内发育的断裂和骨架砂体输导体系之间的相互配置关系,为油气提供良好的运移通道,使油气藏沿南北向成断阶式带状分布;沙三上亚段的泥岩及基山砂体顶部稳定的厚层泥岩、各期次砂体之间被泥岩分隔,且东西向上倾尖灭、沙三段发育封闭性较好的高矿化度原生CaCl2水型,同时部分断层侧向封堵,这些因素的共同作用为油气藏提供良好的保存条件.

Rift-subsidence lake basins are important oil-bearing basin of Eocene in the eastern China.The research of the main controlling factors of sandbody development has great practical significances for the prediction of hydrocarbon reservoirs.The characteristic research of the Paleogene sandbody distribution in west sag of Liaohe Basin shows that sedimentary environment,palaeogeomorphology and lake surface and base level fluctuation are the dominant controlling factors of sandbody development,among which the palaeogeomorphology is the most obvious one except for the sedimentary environment.The palaeogeomorphology of west sag includes palaeo-high,palaeo-ditch and valley,palaeo-platform,palaeo-break in-slope and palaeo-trough fault,which affect the distribution of depositional system and the development of sandbodies.The palaeo-break in-slope is divided into three types,i.e.faulted terrace type break in-slope,faulted scarpe type break in-slope and steep slope type break in-slope.Alluvial fan,fan-deltas and far-shore turbidite fan are developed on faulted terrace type break in-slope;Alluvial fan and nearshore turbidite fan are developed on faulted scarp type break in-slope;Alluvial fan,fan-deltas and nearshore turbidite fan are developed on steep slope type break in-slope.

Sedimentary micro-facies is the basic sedimentation unit in sedimentary system and its sedimentary characteristics can be reflected by log curves.Based on the geological sedimentary characteristics formed in the process of lake development,the lake facies is divided into 4 sub-facies: deep-water lake to half deep-water lake sub-facies,shallow lake sub-facies,shoreward lake sub-facies and lake controlled sub-facies,and then subdivided into 11 sedimentary micro-facies.Analyzed is the relation between the SP and resistivity logging curve's shapes and sedimentary characteristics of the formation.Summarized are the log response properties of different sedimentary micro-facies and log identification sign of each micro-facies.

Fractures are the main flowing channel and effective storage space for the low permeability reservoir in Chaoyanggou Oilfield,Songliao Basin.The exploitation of oil deposits in this oilfield is strongly controlled by the complex distribution of fractures.Based on regional tectonic study,core structural analysis and the data from outcrops and thin sections,we have studied the developmental characteristics,the genetic mechanism and the controlling factors of the fractures in the Chaoyanggou Oilfield.The results show that there are four sets of tectonic fractures in the reservoir,extending in the south-north,east-west,north-west and north-east orientations respectively.The fractures with low dip-angle are dominant in the studied area,which are mainly the along-bedding detachment fractures formed by compressive folding,and the shear fractures related to the thrusting of faults.The fractures with high dip-angle are mainly the extension fractures and oblique fractures.The tectonic fractures are mainly formed in the reversal tectonic stage at the end of Mingshui Formation,when there developed the nearly S-N and nearly E-W orientations fractures.The development degree of the fractures is controlled by the factors of lithology,strata thickness,the faulting,the folding,the depth,etc.The development degree of fractures is different with different lithology;there is a linear relationship between the fracture spacing and the fractured strata thickness;most fractures have a relation to the faulting;the types of fractures are different with different formation phases of the fold;and the development degree of fractures is sharply decreased with the increase in depth.

The Songkan section in Tongzi County of Guizhou Province,with a complete development of the Lower and Middle Triassic,abundant fossils and favorable exposure is an ideal section for the study of marine strata in the Upper Yangtze area.According to the stratigraphic division and correlation,the Lower Triassic is divided into the Yelang and Maocaopu Formations,and the Middle Triassic comprises the Guanling Formation.Carbonate rocks and clastic rocks dominate the Lower and Middle Triassic with the former one making up 67% of the entire section and the latter one 24% respectively.Carbonates are distributed in the Yelang,Maocaopu and Guanling Formations,while clastics are confined to the Yelang Formation.The research results show that the Lower and Middle Triassic was characterized by a multi-cycle deposition.The Yelang Formation includes two transgressive-regressive cycles with sedimentary environments of tidal flat,open platform and shoal,and the Maocaopu Formation includes three cycles with sedimentary environments of open platform and restricted platform.The Guanling Formation is mainly a regressive succession,with sedimentary environments of restricted platform and tidal flat.Upon these researches,the sedimentary model of the Lower and Middle Triassic is established,i.e.,tidal flat-restricted platform-shoal-open platform pattern.