| The object of this study is the fourth member of Dengying formation in the Gao Mo block of Sichuan basin.It is the most important gas reservoir in the basin,and it has great potential for exploration and development.In recent years,with the development and deepening of exploration and research work,the deep gas exploration work in the Sichuan Basin has made new progress again and again,especially in the Lower Cambrian of the Gaoshiti-Moxi block in 2013.The Longwangmiao Formation and the Upper Sinian Dengying Formation discovered a very large gas field,which greatly strengthened people's confidence in the exploration potential of deep gas reservoirs in Central Sichuan.the deep dolomite reservoir in this area has become the focus of the research object of domestic karst reservoir.The development and distribution of Sichuan basin of Sinian period to light four karst palaeogeomorphology reservoir plays a certain role in control,The karst paleomorphology and the development and distribution of the karst reservoir have a very close relationship,restoring the Gaoshiti-Moxi Formation.The karst paleogeomorphology morphological characteristics of dengying formation and its research and analysis are of great significance for the prediction of favorable reservoir facies belts.In addition,the sedimentary facies controls the distribution of reservoirs and is a key element for favorable reservoir facies belt distribution.The division of favorable sedimentary facies is an essential prerequisite for predicting the distribution characteristics of favorable reservoir facies.To elaborate the karst paleo-geomorphology of dengying formation,to clarify the influence of karst paleogeomorphology on hydrocarbon accumulation and to study the distribution characteristics of favorable reservoir facies,according to the collected and mastered Earthquake,drilling and geological data,combined with a large number of literature surveys,this paper uses the impression method to restore the karst paleotopography of the Deng 4 Member,and finely characterizations of it,in particular the quantification and analysis of karst residual mounds.Using the “impression thickness” at the top of the Cambrian base Canglangpu Formation,and simultaneously based on the combination of strata thickness,the karst paleogeography of the 4th section of the Sinian system is accurately restored,and on this basis,it is divided into karst highlands,karst slope and karst depression 3 geomorphic units,according to the recovery of the lamp four section of the paleo karst rocks in the study area,the karst depressions in the western part of the study area can be found,The karst slopes are developed in the central part of the study area,while the karst highland develops in the east.After analysis,it was found that the karst slope is a favorable reservoir development area,and in addition,the residual mounds after karst weathering are mostly favorable hydrocarbon accumulation zones.That is,the distribution of karst residual mounds is also one of the factors affecting the favorable reservoir facies belt distribution.Sedimentation has a certain degree of control over the distribution of the reservoir in the upper part of the Dengying Formation.However,the fine distribution boundary of the sedimentary facies at this stage is not yet clear.Therefore,on the basis of previous researches,the comparison is based on well logging curves(GR-based).Through the identification of the single well sedimentary facies and the study of the continuous sedimentary facies,combined with the seismic facies analysis,the boundaries of the facies are clearly defined.The overall can be divided into three sub-facies: the hilly sub-facies,the inter-facies sub-facies and the Yunping subfacies.The subfacies,and the shoal subfacies are favorable sedimentary facies.In this paper,through the comprehensive analysis of sedimentary facies and karst paleogeography of Dengying Formation in the study area,the distribution characteristics of favorable reservoir facies belts in the Deng 4 Member are predicted based on favorable sedimentary facies,karst slopes,and karst residual mounds.The superimposed areas of karst slopes and karst residual hills are divided into one type of favorable reservoir facies belts,and the superimposed areas of hilly facies and karst slopes are divided into two types of favorable reservoir facies belts. |
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