This study systematically reviews the development history and key technological breakthroughs of large gas fields in the Ordos Basin,and summarizes the development models of three gas reservoir types,low-permeability ...This study systematically reviews the development history and key technological breakthroughs of large gas fields in the Ordos Basin,and summarizes the development models of three gas reservoir types,low-permeability carbonate,low-permeability sandstone and tight sandstone,as well as the progress in deep coal-rock gas development.The current challenges and future development directions are also discussed.Mature development models have been formed for the three representative types of gas reservoirs in the Ordos Basin:(1)Low-permeability carbonate reservoir development model featuring groove fine-scale characterization and three-dimensional vertical succession between Upper and Lower Paleozoic formations.(2)Low-permeability sandstone reservoir development model emphasizing horizontal well pressure-depletion production and vertical well pressure-controlled production.(3)Tight sandstone gas reservoir development model focusing on single-well productivity enhancement and well placement optimization.In deep coal-rock gas development,significant progress has been achieved in reservoir evaluation,sweet spot prediction,and geosteering of horizontal wells.The three types of reservoirs have entered the mid-to-late stages of the development,when the main challenge lies in accurately characterizing residual gas,evaluating secondary gas-bearing layers,and developing precise potential-tapping strategies.In contrast,for the early-stage development of deep coal-rock gas,continuous technological upgrades and cost reduction are essential to achieving economically viable large-scale development.Four key directions of future research and technological breakthroughs are proposed:(1)Utilizing dual-porosity(fracture-matrix)modeling techniques in low-permeability carbonate reservoirs to delineate the volume and distribution of remaining gas in secondary pay zones,supporting well pattern optimization and production enhancement of existing wells.(2)Integrating well-log and seismic data to characterize reservoir spatial distribution of successive strata,enhancing drilling success rates in low-permeability sandstone reservoirs.(3)Utilizing the advantages of horizontal wells to penetrate effective reservoirs laterally,achieving meter-scale quantification of small-scale single sand bodies in tight gas reservoirs,and applying high-resolution 3D geological models to clarify the distribution of remaining gas and guide well placement optimization.(4)Further strengthening the evaluation of deep coal-rock gas in terms of resource potential,well type and pattern,reservoir stimulation,single-well performance,and economic viability.展开更多
Through systematic investigation of deep coal-rock gas in the Ordos Basin,NW China,this work analysed the thickness distribution of the entire Upper Paleozoic coal-rock intervals,quantified the resource potential of r...Through systematic investigation of deep coal-rock gas in the Ordos Basin,NW China,this work analysed the thickness distribution of the entire Upper Paleozoic coal-rock intervals,quantified the resource potential of representative areas(a 12000 km2 rectangular block in the eastern Ordos Basin roughly centered on Yulin City),clarified the occurrence characteristics of coal-rock gas,and identified key development indicators for gas wells,thereby defining the direction for iterative optimization of key technologies.(1)The total coal-rock gas in-place of the Upper Paleozoic coal seams 1^(#)-10^(#)in the resource evaluation region is assessed at 5.66×10^(12) m^(3),of which coal seam 8^(#),currently the main target interval,contains about 3.08×10^(12) m^(3),accounting for roughly 54%of the total.(2)Deep coal-rock gas is characterized by a high ratio of free gas.Under the conditions of 2000 m burial depth,6.35%porosity,95%free gas saturation,and 22.13 m^(3)/t total gas content,the free gas content of the reservoir is estimated to be ca.40%of the total gas.(3)Three productivity evaluation models(triangular,convex,concave)are developed for horizontal wells,of which the triangular model can serve as the reference model for predicting the estimated ultimate recovery(EUR)throughout the lifecycle of coal-rock gas wells.Using the triangular model with a 7 m coal thickness,1500 m effective lateral length and 400 m well spacing,the average single-well EUR is determined to be 4621.28×10^(4) m^(3).(4)Development of the coal seam 8^(#)should employ horizontal wells with pressure-controlled production.Meanwhile,it can be further optimized by adopting the cost-effective strategies of Sulige Gas Field in the Ordos Basin,China.(5)To achieve cost-effective development and increase primary recovery factor,key technologies must undergo continuous iteration and upgrading,focusing on accelerating drilling,extending effective lateral lengths,high-intensity reservoir stimulation,and well-pattern optimization.展开更多
文摘This study systematically reviews the development history and key technological breakthroughs of large gas fields in the Ordos Basin,and summarizes the development models of three gas reservoir types,low-permeability carbonate,low-permeability sandstone and tight sandstone,as well as the progress in deep coal-rock gas development.The current challenges and future development directions are also discussed.Mature development models have been formed for the three representative types of gas reservoirs in the Ordos Basin:(1)Low-permeability carbonate reservoir development model featuring groove fine-scale characterization and three-dimensional vertical succession between Upper and Lower Paleozoic formations.(2)Low-permeability sandstone reservoir development model emphasizing horizontal well pressure-depletion production and vertical well pressure-controlled production.(3)Tight sandstone gas reservoir development model focusing on single-well productivity enhancement and well placement optimization.In deep coal-rock gas development,significant progress has been achieved in reservoir evaluation,sweet spot prediction,and geosteering of horizontal wells.The three types of reservoirs have entered the mid-to-late stages of the development,when the main challenge lies in accurately characterizing residual gas,evaluating secondary gas-bearing layers,and developing precise potential-tapping strategies.In contrast,for the early-stage development of deep coal-rock gas,continuous technological upgrades and cost reduction are essential to achieving economically viable large-scale development.Four key directions of future research and technological breakthroughs are proposed:(1)Utilizing dual-porosity(fracture-matrix)modeling techniques in low-permeability carbonate reservoirs to delineate the volume and distribution of remaining gas in secondary pay zones,supporting well pattern optimization and production enhancement of existing wells.(2)Integrating well-log and seismic data to characterize reservoir spatial distribution of successive strata,enhancing drilling success rates in low-permeability sandstone reservoirs.(3)Utilizing the advantages of horizontal wells to penetrate effective reservoirs laterally,achieving meter-scale quantification of small-scale single sand bodies in tight gas reservoirs,and applying high-resolution 3D geological models to clarify the distribution of remaining gas and guide well placement optimization.(4)Further strengthening the evaluation of deep coal-rock gas in terms of resource potential,well type and pattern,reservoir stimulation,single-well performance,and economic viability.
基金Supported by the Scientific Research and Technology Development Project of PetroChina Company Limited(2023YQX103)Scientific Research and Technology Development Project of China National Petroleum Corporation(2024DJ86).
文摘Through systematic investigation of deep coal-rock gas in the Ordos Basin,NW China,this work analysed the thickness distribution of the entire Upper Paleozoic coal-rock intervals,quantified the resource potential of representative areas(a 12000 km2 rectangular block in the eastern Ordos Basin roughly centered on Yulin City),clarified the occurrence characteristics of coal-rock gas,and identified key development indicators for gas wells,thereby defining the direction for iterative optimization of key technologies.(1)The total coal-rock gas in-place of the Upper Paleozoic coal seams 1^(#)-10^(#)in the resource evaluation region is assessed at 5.66×10^(12) m^(3),of which coal seam 8^(#),currently the main target interval,contains about 3.08×10^(12) m^(3),accounting for roughly 54%of the total.(2)Deep coal-rock gas is characterized by a high ratio of free gas.Under the conditions of 2000 m burial depth,6.35%porosity,95%free gas saturation,and 22.13 m^(3)/t total gas content,the free gas content of the reservoir is estimated to be ca.40%of the total gas.(3)Three productivity evaluation models(triangular,convex,concave)are developed for horizontal wells,of which the triangular model can serve as the reference model for predicting the estimated ultimate recovery(EUR)throughout the lifecycle of coal-rock gas wells.Using the triangular model with a 7 m coal thickness,1500 m effective lateral length and 400 m well spacing,the average single-well EUR is determined to be 4621.28×10^(4) m^(3).(4)Development of the coal seam 8^(#)should employ horizontal wells with pressure-controlled production.Meanwhile,it can be further optimized by adopting the cost-effective strategies of Sulige Gas Field in the Ordos Basin,China.(5)To achieve cost-effective development and increase primary recovery factor,key technologies must undergo continuous iteration and upgrading,focusing on accelerating drilling,extending effective lateral lengths,high-intensity reservoir stimulation,and well-pattern optimization.
