黔北地区志留系下统龙马溪组页岩气成藏潜力
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摘要
在野外地质露头观察和样品测试数据综合分析的基础上,对黔北地区志留系下统龙马溪组页岩的沉积特征及展布、地球化学特征、埋藏热演化史、储层特征等页岩气藏形成条件进行研究。研究结果表明:研究区龙马溪组页岩区域分布广,残余面积约为14 600 km~2;厚度大,最厚可达200 m;有机质类型好,干酪根为腐泥型;有机质质量分数高,残余有机碳质量分数w(TOC)高达3.92%;含气量好,饱和吸附量高达2.77 m~3/t;热演化程度高,镜质体反射率高达2.68%;埋藏深度适中,大部分地区埋深为1~2 km;脆性矿物质量分数高,平均值为43.2%;非均质性强,脆性矿物质量分数横向、纵向上变化都大;孔隙度较低,集中在4%~10%;渗透率低,平均值为0.088×10~(-3)μm~2。因此,研究区龙马溪组具备良好的页岩气成藏地质条件和压裂开采条件,习水—仁怀地区和道真—务川—沿河地区为最有利的页岩气勘探区带。研究区龙马溪组页岩资源丰富,运用概率体积法和地质类比法算出的资源量吻合很好,为(3.52~4.69)×10~(12) m~3。
Based on comprehensive analysis of outcrops observation and sample testing,the formation conditions of shale gas in Lower Silurian Longmaxi formation shale of northern Guizhou were analyzed, such as sedimentary characteristics and distribution, geochemical characteristics, burial thermal evolution and reservoir characteristics. The results show that the Longmaxi formation shale in the study area, characterized by extensive distribution(residual area of about 14 600km~2), big thickness(maximum of up to 200 m), fine kerogen type(sapropel type), rich organic matter content(residual total organic carbon mass fraction w(TOC) of 3.92%), high air content(saturated adsorption amount of 2.77%), high thermal evolution(vitrinite reflectance of 2.68%), appropriate depth(a large area of 1-2 km in depth), high brittleness mineral content(average of 43.2%), strong heterogeneity(great changes of brittleness mineral content in horizontal and vertical), low porosity(concentrated in 4%-10%) and low permeability(average of 0.088×10~(-3) μm~2), have good accumulation potential geological and fracturing mining conditions, and Xishui-Renhuai Areas and Daozhen-Wuchuan-Yanhe Areas are the most favorable exploration zones. Longmaxi formation shale in the study area is abundant in shale gas resources, and the values of resources calculated by probability volume should be(3.52-4.69)×10~(12) m~3, which match well with those obtained by geological analogy method.
Based on comprehensive analysis of outcrops observation and sample testing,the formation conditions of shale gas in Lower Silurian Longmaxi formation shale of northern Guizhou were analyzed, such as sedimentary characteristics and distribution, geochemical characteristics, burial thermal evolution and reservoir characteristics. The results show that the Longmaxi formation shale in the study area, characterized by extensive distribution(residual area of about 14 600km~2), big thickness(maximum of up to 200 m), fine kerogen type(sapropel type), rich organic matter content(residual total organic carbon mass fraction w(TOC) of 3.92%), high air content(saturated adsorption amount of 2.77%), high thermal evolution(vitrinite reflectance of 2.68%), appropriate depth(a large area of 1-2 km in depth), high brittleness mineral content(average of 43.2%), strong heterogeneity(great changes of brittleness mineral content in horizontal and vertical), low porosity(concentrated in 4%-10%) and low permeability(average of 0.088×10~(-3) μm~2), have good accumulation potential geological and fracturing mining conditions, and Xishui-Renhuai Areas and Daozhen-Wuchuan-Yanhe Areas are the most favorable exploration zones. Longmaxi formation shale in the study area is abundant in shale gas resources, and the values of resources calculated by probability volume should be(3.52-4.69)×10~(12) m~3, which match well with those obtained by geological analogy method.
引文
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[12]张金川,林腊梅.页岩气资源评价方法与技术:概率体积法[J].地学前缘,2012,19(2):184-191.ZHANG Jinchuan,LIN Lamei.The method of shale gas assessment:probability volume method[J].Earth Science Frontiers,2012,19(2):184-191.
[13]张琳婷,郭建华,焦鹏,等.湘西北下寒武统牛蹄塘组页岩气藏形成条件与资源潜力[J].中南大学学报(自然科学版),2014,45(4):1163-1173.ZHANG Linting,GUO Jianhua,JIAO Peng,et al.Accumulation conditions and resource potential of shale gas in lower Cambrian Niutitang formation,northwestern Hunan[J].Journal of Central South University(Science and Technology),2014,45(4):1163-1173.
[14]SCHMOKER J W.Resource-assessment perspectives for unconventional gas system[J].AAPG Bulletin,2002,86(11):1993-1999.
[15]POLLASTRO R M.Total petroleum system assessment of undiscovered resources in the giant Barnett Shale continuous gas accumulation,Fort Worth Basin,Texas[J].AAPG Bulletin,2007,91(4):551-578.
[2]SHIRLEY K.Tax break rekindled interest:shale gas exciting again[J].AAPG Explorer,2001,22(3):24-25.
[3]Navigant Consulting Inc.North American natural gas supply assessment[R].Chicago:Navigant Consulting Inc,2008:9-40.
[4]KUUSKRAA A V.Worldwide gas shales and unconventional gas:a status report[R].Washington D C:Energy Information Administration,2009:10-21.
[5]王世玉.黔北地区上奥陶统五峰组—下志留统龙马溪组黑色页岩特征研究[D].成都:成都理工大学能源学院,2013:31-38.WANG Shiyu.The study of the shale(gas)features in Upper Ordovician—Lower Silurian,Uplift in the northern of Guizhou[D].Chengdu:Chengdu University of Technology.School of Energy,2013:31-38.
[6]丰国秀,陈盛吉.岩石中沥青反射率与镜质体反射率之间的关系[J].天然气工业,1998,8(3):20-25.FENG Guoxiu,CHEN Shengji.Relationship between the reflectance of bitumen and vitrinite in rock[J].Natural Gas Industry,1998,8(3):20-25.
[7]LOCKS R G,READ R M,RUPPEL S C.Morphology,genesis,and distribution of nanometer-scale pores in siliceous mudstones of the Mississipian Barnett Shale[J].Journal of Sedimentary Research,2009,79(12):848-861.
[8]ROGER M.Pore types in the Barnett and Woodfood shale gas:contribution to understanding gas storage and migration pathways in fine-grained rocks[J].AAPG Bulletin,2011,95(12):2017-2030.
[9]CURTIS J B.Fractured shale gas system[J].AAPG Bulletin,2002,86(11):1921-1938.
[10]JARVIE D M,HILL R J.Unconventional shale gas system:the Mississipian Barnett Shale of north-central Texas as one model for thermogenic shale gas assessment[J].AAPG Bulletin,2007,91(4):475-499.
[11]黄文明,刘树根.川东南—鄂西渝东地区下古生界页岩气勘探前景[J].地质通报,2011,30(2):364-371.HUANG Wenming,LIU Shugen.Shale gas exploration prospect of Lower Paleozoic in southeastern Sichuan and western Hubei—eastern Chongqing areas,China[J].Geological Bulletin of China,2011,30(2):364-371.
[12]张金川,林腊梅.页岩气资源评价方法与技术:概率体积法[J].地学前缘,2012,19(2):184-191.ZHANG Jinchuan,LIN Lamei.The method of shale gas assessment:probability volume method[J].Earth Science Frontiers,2012,19(2):184-191.
[13]张琳婷,郭建华,焦鹏,等.湘西北下寒武统牛蹄塘组页岩气藏形成条件与资源潜力[J].中南大学学报(自然科学版),2014,45(4):1163-1173.ZHANG Linting,GUO Jianhua,JIAO Peng,et al.Accumulation conditions and resource potential of shale gas in lower Cambrian Niutitang formation,northwestern Hunan[J].Journal of Central South University(Science and Technology),2014,45(4):1163-1173.
[14]SCHMOKER J W.Resource-assessment perspectives for unconventional gas system[J].AAPG Bulletin,2002,86(11):1993-1999.
[15]POLLASTRO R M.Total petroleum system assessment of undiscovered resources in the giant Barnett Shale continuous gas accumulation,Fort Worth Basin,Texas[J].AAPG Bulletin,2007,91(4):551-578.