Present geotemperature and its suggestion to natural gas generation in Xujiaweizi fault-depression of the northern Songliao Basin

According to stastistic of present geotemperatures at the depths of 1000,2000,3000 and 4000 m,respectively in the Xujiaweizi fault-depression of the north Songliao Basin,the result indicates that Xujiaweizi fault-depression falls in the high geotemperature area,with the higher geothermal gradient in the depression layer than that in the fault-depression layer.The geothermal gradient decreases with the increasing of the depth.The thermal conductivity of rock greatly controls the geothermal gradient.The main factors constraining the current geotemperature include thermal configuration of the earth's crust, deep faults,distribution and abundance of radioelements.The high geotemperature is in favour of generation of deep gas.

Uranium Metallogeny in Fault-Depression Transition Region:A Case Study of the Tamusu Uranium Deposit in the Bayingobi Basin

Compared to the sandstone-type uranium deposits in the Ordos Basin and the Songliao Basin,the Tamusu uranium deposit in the Bayingobi Basin formed in fault-depression transition region displays distinctive features.First,the uranium-bearing sandstones and their interlayer oxidation zone extend longitudinally no more than ten kilometers.Second,gravity flow sediments are more common in the uranium-bearing strata.Comprehensive facies analysis indicates that the Upper Member(orebearing horizon)of the Bayingobi Formation was largely deposited in fan deltas that prograded into lakes during period of relatively dry paleoclimate.Spatial distribution patterns of five facies associations along with two depositional environments(fan delta,lake)were reconstructed in this study.The results demonstrated that the depositional systems and their inner genetic facies played different roles in uranium reservoir sandstone,confining beds(isolated barrier beds)and reduction geologic bodies during uranium mineralization process.

Facies logging identification of intermediate-basic volcanic rocks in Huoshiling Formation of Songliao Basin

Volcanic oil and gas reservoirs are generally buried deep,which leads to a high whole-well coring cost,and the degree of development and size of reservoirs are controlled by volcanic facies.Therefore,accurately identifying volcanic facies by logging curves not only provides the basis of volcanic reservoir prediction but also saves costs during exploration.The Songliao Basin is a‘fault-depression superimposed’composite basin with a typical binary filling structure.Abundant types of volcanic lithologies and facies are present in the Lishu fault depression.Volcanic activity is frequent during the sedimentary period of the Huoshiling Formation.Through systematic petrographic identification of the key exploratory well(SN165C)of the Lishu fault-depression,which is a whole-well core,it is found that the Huoshiling Formation in SN165C contains four facies and six subfacies,including the volcanic conduit facies(crypto explosive breccia subfacies),explosive facies(pyroclastic flow and thermal wave base subfacies),effusive facies(upper and lower subfacies),and volcanogenic sedimentary facies(pyroclastic sedimentary subfacies).Combining core,thin section,and logging data,the authors established identification markers and petrographic chart logging phases,and also interpreted the longitudinal variation in volcanic petro-graphic response characteristics to make the charts more applicable to this area's volcanic petrographic interpretation of the Huoshiling Formation.These charts can provide a basis for the further exploration and development of volcanic oil and gas in this area.