| The Dengying Formation in the Moxi area of the study area is an important oil and gas exploration and development stratum in the Sichuan Basin,and breakthroughs have been continuously made.The predecessors have done a lot of macro work on the surface karst in the area to provide support for further development.Fine analysis of the temporal and spatial distribution of the reservoir and analysis of the main controlling factors.In this paper,the ancient karst reservoir of the fourth member of the Dengying Formation in the Moxi area is taken as the research object,combined with the previous research results,through the core,wavelet transform analysis,imaging logging,ordinary and cast slice of the core of the fourth member of the Dengying Formation in the study area.Based on comprehensive analysis,based on the establishment of a quasi-sequence(five-level sequence)level isochronous framework in the whole area,the vertical superficial karst reservoir combined with 2m-level high-precision core,thin slice observation and imaging logging data is fine Based on statistical analysis,a systematic analysis of the reservoir characteristics,distribution laws and main controlling factors of the superficial karst plane and vertical belts is carried out.The results achieved are as follows:(1)Based on the analysis of wavelet transform,imaging logging and GR logging,a high-precision sequence stratigraphic division and comparison study was carried out.Two third-level sequences were identified in the fourth member of the Dengying Formation in the study area.Named SQ1 and SQ2,each three-level sequence consists of TST and HST.Furthermore,7 quasi-sequence groups(named Pss1?Pss7 from bottom to top)and 13 quasi-sequence groups(named Ps1?Ps13 from bottom to top)were further divided.On this basis,the five-level sequence stratigraphic isochronous framework of the whole area was established.(2)Reveal the types of supergene karst storage space in Moxi area including intergranular(solution)pores,intragranular karst pores,inter-framework(karst)pores and pane pores and intergranular pores,karst caves and micro-fractures and fractures.(3)It is clear that the fourth karst reservoir in the Dengying Formation can be divided into vertical seepage zone,horizontal subsurface flow zone,and deep slow flow zone.The plane class is divided into three geomorphic units: karst level,karst slope,and karst basin.The fine vertical statistics and analysis of the 2m-class fine core,slice and imaging logging combined revealed that the cumulative thickness of the supergene karst highland-slope-basin reservoir has a thinning feature,while the top of the supergene karst highland reservoir is weaker than In the central area,karst slope-basin reservoirs are mainly distributed in the upper part;and the reservoir space combination has a transition from karst highland fracture-cavity(hole)combination to karst basin,mainly to micro-fracture-related pores and even pore combinations.A comprehensive study established a unique karst model map in the study area.(4)The main controlling factors of ancient karst reservoirs are discussed,and it is considered that the sedimentary facies belt of the fourth member of the Dengying Formation controls the material basis of reservoir development.The high-energy belt is the core area for the development of high-quality reservoirs.Oil and gas filling and cracking adjustment control the final formation of the reservoir.The upper part of the quasi-sequence group(four-level sequence)in the karst highlands-karst slope area is the most favorable development area of the reservoir. |
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