Evaluation Of Favorable Area Of ??shale Gas In Longmaxi Formation In Northern Hebei

Situated in the junction of Yunnan,Guizhou and Sichuan provinces,the Dianqianbei Study Zone(the north Yunnan and Guizhou Provinces)covers an area of 15183 km2 in total.As its rapid development of the shale gas exploration in recent years,over 20 exploratory and appraisal wells of all kinds have been built and industrial gas run breakthroughs have been achieved for many times,which not only ranks the area third in China that made breakthrough in the field of shale gas development after the Jiaoshiba and Changning-Weiyuan Formation,but also proves that Dianqianbei Study Zone holds a certain potential in developing shale gas.In order to further explore the distribution and enrichment pattern of shale gas as well as to estimate its reserves,on the basis of previous researches,this study is going to target the Longmaxi Formation and to systematically analyze its geologic background,geological characteristics of the reservoir,geochemical characteristics,decompaction of the target layer and the paleoenvironment of the sediments,etc.The results are:(1)by the study of the lithofacies,sedimentary tectonics and palaeobios of the Silurian of the Longmashi Formation,it is believed that Longmaxi Formation was formed under the shelf depositional environment.And from top to bottom,as the sedimentary water deepened,the depositional environment changed from shallow water shelf into deep water shelf.(2)By combining the optimization model and the traditional method,the stratified acoustic time difference model and porosity varying with depth model in the Dianqianbei Study Zone are established.And then according to the rock matrix invariance principle we have conducted the back-striping method to the formation of this area and obtained the data of primary deposition thickness distribution law of Longmaxi Formation.(3)Based on the characteristics of Longmaxi Formation sedimentary facies distribution,TOC distribution and the trend of stratigraphic compaction restoring to paleoclimatic,the valuable area of shale gas is studied and its range is determined.(4)Applying the volumetric method and the fourth resource evaluation software of PetroChina Exploration and Development Research Institute,the evaluation parameters of valuable area are determined,and so do the favorable parameter system and preferred method under the environment of marine shale sedimentary in the background of high evolution and complex structure.(5)Combining reservoir characteristics and geochemical characteristics of fine division with shale gas reservoirs evaluation,we have calculated that the area's unconventional resource amounts to 24871.8 × 108m3.At the same time,the spatial distribution of unconventional resources in the exploration area is obtained,and their strategic position is clarified,too.Finally,this paper will list the area suitable exploration and development and provide the resource basis for the development of unconventional oil and gas development plan.