Study And Evaluation Of Shale Reservoir Characteristics Of The Longmaxi And Qiongzhusi Formations In The Lower Paleozoic Of Changning Block

This dissertation takes Qiongzhusi and Longmaxi shaleas as an object of study,which comes from Changning area of southern Sichuan basin.By usingnumerous experimental means,including overburden pressure pulse permeability experment,X ray diffraction,X ray fluorescence,cathodoluminescence,X ray diffraction quantitative analysis,argon ion polishing,scanning electron microscopy and high mercury nitrogen adsorption experment,magnetic resonance experment,rock mechanics experiment,to study Qiongzhusi andLongmaxi shale's physical characteristics,mineral composition,organic matter characteristics,aperture type,developmental characteristics,reservoir space characteristics and distribution characteristics of pore.Finally,completingthe selection of the main controlling factors and reservoirevaluation parameters.The mainly achievementsare as follows:(1)To complete a comprehensive study of Qiongzhusi and longmaxiformation shale reservoir of Changning block from four aspects,including regional geology,petrology,organic carbon abundance and physical characteristics.At the same time,making a comparison with the Silurian Permian shale reservoirs with Wuhu block and the typical North American rock reservoir.Finally,we findthat there has similaritiesbetween the threeareas.(2)Shale storage space includes two categories:fracture and matrix pore.according to the origin,matrix porecan be divided into inorganic matrix pore,organic pore and biogenic hole;At the same time,according to the tectonic origin,cracks can be divided into original seam and secondary seam Longmaxi shale is full of organic pore,clay minerals interlayer pores and intergranular pore;Qiongzhusi shale is full of clay minerals interlayer pores,intergranular pore,organic matter pores andintragranularpore(3)The shale porosity distribution of Longmashi formation is between 1.84 and 9.10%,with an average of 4.07%,mainly distributing between 2 and 6%.And the permeability distribution is between 1.75 and 1250nD,with an average of 90.83nD,mainly distributing between 1?50nD.The physical properties of the Qiongzhuformation are much worse than Longmaxiformation,with an average porosity of only 1.446%and a much lower permeability,which shows a strong heterogeneity.(4)The high pressure mercury curve of Longmaxi and Qiongzhusi formationare extremely fine skewness and poor sorting types.The mercury withdrawal efficiency is extremely low and the mercury injection parameters reflects shale has the characteristics of small pore throat and poor sorting;at the same time,two formation shale's adsorption curve is type ?,with a pore structure characteristics of slit.As for the adsorption parameters contrast,Longmaxi formaton's surface value,pore volumeis high butQiongzhusi formation is relatively low.Moreover,the shale surface has certain correlation with the content of carbonate minerals and TOC.(5)Synthsizing the advantages and disadvantages of NMR,N2 adsorption and high pressure mercury,we have established a more accuratemethod to test shale pore size distribution.The result indicats that Longmaxi shale micropores and big hole are well developed,accounting for 59.38%and 38.24%,but others are not developed.Qiongzhusi shale is full of large pores,accounting for 83.66%,but microporous and mesoporous are not developed,only accounting for 16.34%,this phenomenon may be an important factor leading to less gas adsorption.(6)The screening parameter of reservoir evaluationare TOC,total porosity,permeability,gas content and brittle mineral content.We have developed a classification standard and the evaluation results shows that Longmaxi shale is good reservoir but Qiongzhusi shale reservoir is not.According to the analysis,it is considered that the content of organic matter,brittle minerals,clay minerals and micro pores are important factors for the formation of high quality shale reservoirs.