Research On Depositional System Of Feixianguan Formation In Chengkou-E'xi Area

The black floor door structure in the study area is mainly located in the eastern margin of East Sichuan,located in East Sichuan basin margin of Daba Mountain front tectonic composite belt.The ground for a nearly East-West relief short box anticline,Shimen syncline and south of Shuanghe village,Huang Tong Cun structure across the mountain temple,Wu tianxingqiao syncline and wood structure relative to North broad,and gradually transition to the Dabashan fold syncline with the southern margin of the east across the low saddle and seven step anticline offset.In recent years,with the deepening of oil and gas exploration in the eastern Sichuan basin,Permian Changxin group two-three Feixianguan marine carbonate oil and gas exploration breakthroughs have been found in Longgang,Huanglong five hundred ladder,and Guangyuan Puguang field,a series of platform margin reef reservoir the main body of the large natural gas reservoir,that huge oil and gas exploration prospect in this field,and has become the main field of energy over Sichuan basin.The main contents of this paper include the following aspects:According to theobservationof profile and the analysis of thin section,combined with the latest drilling data andbased on the resultsof petrology,paleontologyand geophysical interpretation.The study found that the earlier FeixianguanFormationof Lower Triassicis the isolated carbonate ramp model and the Latter Period of Feixianguan Formation is the land carbonate platform,and it includedrestricted platform,open platform,platform fore-slope,deep water shelf sedimentation zones and so on.According to the identification of the key sequence boundaries,the Feixianguan Formation in the study area can be divided into 2 3th sequences and 5 4th sequences,and established to a 4th sequence stratigraphic model.The pattern of sedimentary facies and its evolution in sequence frame showed that the water fromearlierFeixianguan Formation tothe Latter Period of Feixianguan Formation were becoming more and more lower,and in this period,the filling sedimentation has happened.The sedimentary framework of Feixianguan Formation in Fengjie area was transitioned fromopen platform-platform margin-platform fore-slope-shelf sedimentation zones torestricted platform-open platform,and at the Latter Period of Feixianguan Formation was became to a tidal flat of restricted platform by peneplanation.Chengkou exi area oolitic reservoir formed by diagenesis,and relative sea-level change,sedimentary facies have close ties,but actually belong to the platform edge oolitic beach,and thus have a positive impact for the occurrence and development of facies belt.The relative sea level decreased,can promote the reservoir pore formation in the diagenetic process,dolomitization is an indispensable role on the formation of the reservoir has a positive effect,in addition,the corrosion is extremely beneficial,not only that the formation of pores,changes in the reservoir,fracturing has produced important influence.Combined with the earthquake prediction data,sedimentary facies study and reservoir research results,the favorable distribution zones of oolitic beach reservoir are predicted and evaluated,and the geological theory foundation has been laid for the reservoir prediction work.