Study On Potential Exploration Target Layers Of Shale Gas In Devonian In The Central Area Of Guangxi

Shale gas exploration started in the United States.With the increasing share of shale gas in the USA,natural gas exploration industry,many countries have carried out research on shale gas exploration and development in their own country driven by the huge commercial value.Comparing with the United States,the largest producer of shale gas,the shale gas exploration industry of China is far behind the United States due to the over simplification of shale gas exploration formations and basins.The Single exploration basin and the exploration formations limit the expansion of shale gas exploration scale,so we should focus on finding new sedimentary basins and formations with shale gas exploration potential.Guangxi is located in the eastern margin of"Dianqiangui Ancient Land"in the late Silurian.Due to the Guangxi movement in the late Silurian,Dianqiangui Ancient Land evolved into Dianqiangui Basin and formed a set of thick marine sedimentary rocks in Devonian,which is expected to become the shale gas exploration strata in Guangxi.In the research of field exploration,Devonian sequences in Guangxi are divided in several sections,and 13 third-order sequences are divided from bottom to top in the Devonian in the section where the Devonian is exposed of Guangxi area.Based on this,regional stratigraphic correlation is carried out,and the Devonian paleogeographic framework of the study area is understood to a certain extent.It is found that the spatial distribution of high-quality source rock series composed of platform basin facies shale series in the study area is mainly controlled by Ziyun-Luodian-Nandan-Du'an ancient fault zone,Yishan ancient fault zone and Lipu ancient fault zone,that is,an interconnected hydrocarbon-generating sag is formed along Nandan to Du'an and Hechi to Liuzhou in Guangxi.Further combing the spatial and temporal distribution of high-quality source rocks is an important clue to find potential shale gas exploration blocks.In this paper,a detailed study has been carried out in the areas along Nandan to Du'an and Hechi to Liuzhou where high-quality source rocks may be distributed,and the total TOC and R_Ovalues have been measured by sampling and analysis in the corresponding intervals.Based on the geochemical data of source rocks in various regions and intervals,it is found that the potential exploration target strata composed of high-quality source rocks of Devonian mainly developed from late Early Devonian to early Late Devonian,belonging to SQ₅to SQ₁₀of 13 third-order sequences of Devonian,and the quality of source rocks formed the transgressive system tract and early high water level system tract of SQ₅to SQ₁₀,in particular,in the maximum flooding period is the best.Based on this understanding,the temporal and spatial distribution characteristics of potential exploration target layers mainly composed of high-quality source rocks of platform basin facies are summarized and discussed.Based on the geological background and the thickness variation of high-quality source rocks,several favorable blocks such as Baxu block,northwest Hechi block and Lipu block are preliminarily selected,and the exploration potential of Baxu block is emphatically discussed.