中国非常规天然气地质特征、开发技术与发展前景OA

Based on China's latest exploration and development achievements,production performance data of over 7 000 horizontal wells,and the Unconventional Oil & Gas Digital-Intelligent Platform(UOG),and by integrating statistical analysis and machine learning prediction techniques,this study systematically compares four types of unconventional natural gas(tight gas,shale gas,shallow coalbed methane and medium-deep coal-rock gas)in the country,from the aspects of resource characteristics,key technologies,development indicators and prospects.China holds a substantial quantity of unconventional natural gas,especially shale gas and medium-deep coal-rock gas which boast prominent resource advantages and present a large-scale"continuous"spatial distribution.More than 75％of high-quality resources are concentrated in the Ordos and Sichuan basins.A type-adaptive key technical system has been established,incoprating extensive recovery of tight gas by virtue of"well pattern optimization+low-cost fracturing",commercial development of shale gas relying on"geological-engineering dual sweet spot evaluation+super fracture network fracturing",stable production of shallow-medium coalbed methane through"precision drainage and depressurization",and breakthroughs in pilot technologies such as pressure-controlled development and energy-gathered fracturing for horizontal wells of medium-deep coal-rock gas.The four types of unconventional natural gas vary significantly in development indicators.Tight gas,shale gas and medium-deep coal-rock gas reach peak production 10-30 days after gas breakthrough,showing the characteristics of high initial production followed by rapid decline(with a first-year decline rate of 30％-51％).Specfically,shale gas horizontal wells have the highest average daily production in the first year(7.28×104 m3/d on average)and single-well estimated ultimate recovery(EUR)(8 255×104 m3 on average).Shallow coalbed methane reaches peak production about 240 days after gas breakthrough,presenting a trend of slow rise-gentle decline,with the lowest single-well indicators.At present,the development of unconventional natural gas is faced with four major constraints including complex geology,technical bottlenecks,environmental restrictions and imperfect policies.It is necessary to address the predicament through multi-dimensional coordination in terms of resources,technology,environmental protection and policies.