The Distribution Rules And Exploration Targets Of The Changxing Formation Reefs In Longgangdong Area Are Preferred

Distributed in the edge facies belt and inter-platform which located on both the east and the west sides of Kaijiang-Liangping Trough,organic reefs of Changxing Formation,Sichuan Basin,are the focus in research.Since 1996,significant results have been achieved in the key exploration areas of the trough.And some reef gas reservoirs such as Qilibei,Huanglongchang,Wubaiti and Puguang were discovered.Meanwhile,exploration breakthroughs of reef gas reservoirs in Tieshannan and Shuangjiaba areas of the west side were made.Especially in 2006,the discovery of reef reservoirs in central Longgang area and the drilled Longgang 81 and 82 wells in the east showed a bright prospect of the edge belt in the western trough.According to the exploration,drilling,seismic and logging achievements,integrating the stratigraphy,sedimentary facies,and the properties of organic reefs,this paper determines the distribution law and favorable areas of the reefs,and predicts their distribution.Changxing Formation in the exploration area are divided into 3 secondary cycles,so as to carry out stratigraphic reclassification for 73 wells in the whole area,describe the lateral variation and evolution rule of sedimentary facies belts,and make a plane distributive map of sedimentary facies.Taking Longgang 80 well as a standard,based on the 3D seismic facies study,we classify the stratigraphic boundary(Feixianguan and Changxinig Formations)for wells in platform,slope and trough facies belts,in order to depict the trough boundary of eastern Longgang.That provides evidences for the distribution research of favorable zones.By using a synthetic identification technology of organic reefs,platform margin reef distribution and reservoir prediction are studied and their characteristics described.Combining the top boundary reflection property variation with the thickness sedimentary changes,the variations in trough,slope and platform are analyzed.The sedimentary facies obtained from single-well log curve property and core data are used to determine the facies boundary.Therefore,the favorable faciesbelts of reef-bioclastic beach reservoirs have been discovered.The reef reservoirs are distributed in NW-SE trend along with Kaijiang-Liangping Trough.Predictions for reef reservoirs of Changxing Formation are carried out by seismic,drilling and logging data.