Characteristics Of Fluid And Hydrocarbon Preservation In The Lower Cretaceous Of Lishu Fault Depression,Songliao Basin

Lishu fault depression is located in the southeast uplift belt in southern part of Songliao basin.With fault depression and depression layer double-layer structure,be-longing to the continental intraplate rift basin.the fault structural layer:early creta-ceous K1d-K1h;the depression structural layer is from K1q to K2n.Relatedto the oil and gas geological conditions have also been conducted a lot of research work,which is scientific and effective in promoting the oil and gas exploration.But the process of fluid accumulation,hydrocarbon migration accumulation-enrichment-savingis are still very vague.Based on the analysis of faulted strata,tectonic framework,fault system.Geochemical characteristics of hydrological and hydrodynamic characteristics are studied,the comprehensive evaluation of oil and gas preservation conditions of the research area provide guidance for the oil and gas exploration in the future.The main contents are as follows:(1)The hydrogeochemistry characteristics of lower cretaceous formation of Bawu-Siwujiazi-Shiwu oil and gas fieldscan be divided into three water chemistry profile unit.Overall,less than 1200m depth for atmospheric water infiltration belt;1200-2000m for cross-formational flow concentration belt;Below 2000m for mudstone compaction drainage fade zone.From 1200m to 1600m depth range,for-mation water salinity of the some exploratory well is relatively low.salinity changes with depth is not obvious.It suggests that due to the fracture development,fluid ver-tical connectivity is good.Atmospheric water along the open fracture infiltrated,leading to deeper formation water desalination.(2)The ?D??18O datapoints of lower cretaceous formation water and fluid inclu-sions in lishu fault depression are actually located in near atmospheric precipitation curve,it shows that formation water in Lishu fault depression are mainly sedimentary burial water affected by the atmospheric water;it is particularly obvious that for-mation water of the upper of K1q is influenced by atmospheric water.Into the deeper formation,atmospheric water influence wane gradually.Compared with formation water,the inclusion of ?D values and ?18O values areobvious negative bias,it suggests that formation water had been suffered strong infiltration effect from the ancient at-mosphere water.The degree of atmospheric water infiltration is gradually weakened from the central structural belt to the two side slope belt,from the top structure to low parts.(3)As for Pressure profile of Lishu fault depression,there are three zones:0-1200m for normal pressure zone,the equivalent of K1q2 and its upper;1200-2200m for low pressure zone,the main development in K1ql1?K1d and the upper of K1y;Be-low 2200m for high pressure zone,the main development in the lower of K1y?K1sh?K1h.(4)Oil and gas exploration favorable area of K1q?K1d in the lishu fault depres-sion are mainly includes:(1)the area between Houwujiahu area and Bawu gas field in the central structural belt;(2)the block of northeast and southwest of Houwujiahu area;(3)the local uplift structure betweeneast Qin Jiatunfracture and west Qin Jiatunfrac-ture;(4)the northern of Xiao Chengzi.Oil and gas exploration favorable area of K1y?K1 shin the lishu fault depression are mainly includes:(1)the area between Houwujiahu area and Bawu gas field in the central structural belt;(2)the western of-Bawu gas field;(3)the steep slope of downdropped block of Sangbeifault zone in Sujiatun area;(4)the northern of Jinshan area.