川西南天宫堂地区龙一段1亚段页岩气富集条件及勘探有利区评价OA

[Objective]The shale gas reservoir in the First Member of the Longmaxi Formation in the Tiangongtang area of southwestern Sichuan exhibits significant heterogeneity.To investigate the factors influencing shale gas enrichment,this study systematically analyzed the enrichment conditions and exploration potential in southwestern Sichuan.[Methods]This was achieved through an interdisciplinary approach incorporating core analysis,geochemical analysis,mineralogical characterization,and well-logging interpretation.[Results]The first sub-member(Long 1-1)contains continuous organic-rich shale with a thickness of 25–60 m,featuring a TOC content of 1.0%–4.0%(average 3.19%).The lower intervals(Long 1-1-1 to Long 1-1-3)show significantly higher TOC values than the upper intervals.With Ro values ranging from 2.58%to 3.16%,the shale is in an overmature stage.The mineral composition is dominated by quartz(35%–45%),clay minerals(25%–35%),and carbonate minerals(15%–25%).Brittle mineral content exceeding 59%and brittleness indices of 60.3%–71%indicate favorable fracability.The reservoir space comprises organic pores(0.02–0.9 μm in diameter),inorganic pores(including intragranular dissolution pores and intergranular pores),and a multi-scale fracture system(including structural fractures,non-structural fractures,and microfractures).The porosity ranges from 3.0%to 6.0%(average 4.2%),while the permeability varies between 0.0003 and 0.2352 mD(2.96×10-7–2.32×10-4μm2),exhibiting a vertical permeability profile with low values at the top and bottom and high values in the middle.Analysis of structural preservation conditions reveals that gentle anticlines and monoclinal structures provide better preservation conditions,whereas areas near steep fault zones experience significant gas dissipation.Formation pressure coefficients show a positive correlation with production,and wells with a pressure coefficient exceeding 1.4 typically achieve daily production rates above 2.0×104 m3/d(e.g.,Well Y203 at 3.626×104 m3/d).[Conclusion]Through establishing a comprehensive evaluation index system,the study area was subdivided into favorable zones of Class I(TOC>2.4%,brittleness index>65%,porosity>4.5%,high-quality shale thickness>35 m,burial depth 3000–4000 m,pressure coefficient>1.4)and Class II,providing a scientific basis for shale gas exploration and development in the Tiangongtang area.[Significance]The research findings elucidate the key factors that control shale gas enrichment in complex structural settings and offer guidance for efficient shale gas development in southwestern Sichuan.