Formation mechanism and targeted descaling technology of sand-scale composites in ultra-deep gas wells in the Kuqa piedmont of the Tarim Basin
The ultra-deep gas field in the Kuqa piedmont of the Tarim Basin is the main gas source for the West-East Gas Pipeline,and it is characterized by ultra-high temperature,ultra-high pressure,high salinity,strong heterogeneity of reservoir fractures,etc.The problem of sand-scale composite is prominent during the production of gas wells,with the impact on the production capacity of gas field up to 800× 104 m3/d.To achieve efficient descaling in ultra-deep gas wells,this paper reveals the formation mechanisms of sand-scale composite in ultra-deep gas wells using the thermodynamic prediction model of gas-water two-phase scaling,the rock mechanics experiments of fractured reservoirs,and the simulation of gas-liquid-solid flow in wellbore,and accordingly develops the key technologies for targeted descaling and production restoration.And the following research results are obtained.First,scaling along with flow pressure drop at high temperature and sand production due to fracturing of fracture surface are the internal formation mechanisms of the sand-scale composites in ultra-deep gas wells.Second,the formation of sand-scale composites due to the scale solidification and unconsolidated sand bridges is the main reason for the blockage and production reduction of gas well,and the targeted descaling technology is the key to descaling and production restoration.Third,the targeted descaling area is the wellbore diameter variation area and the martrix-fracture system within 5 m around the wellbore,and the optimal descaling occasion occurs when the gas well blockage rate is between 30％and 60％.Fourth,compared with the commonly used acidic descaling solutions,non-acidic descaling solutions have a corrosion rate of 0.49 g/(m2·h)at the same level of descaling ability,which can meet the technical requirements of low corrosion rates and high descaling efficiency.In conclusion,the established targeted descaling technology for ultra-deep gas wells has been applied 159 well times in the ultra-deep gas field in the Kuqa piedmont of the Tarim Basin,with an effectiveness rate of 93.3％and the cumulative increase in natural gas production of 75.08×108 m3.The targeted descaling technology is an effective method for the rapid descaling and production restoration of the main gas wells in the West-East Gas Pipeline and provides technical reference for descaling and production in similar gas fields at home and abroad.
Tarim BasinUltra-deep layer of Kuqa piedmontScaling along with flow pressure drop at high temperatureSand production of fractured reservoirSand-scale compositeNon-acidic targeted descaling technology
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维普
