Research and application of ultra-deepwater shallow drilling fluid system
The ultra-deepwater shallow wells in the South China Sea have low mud surface temperature,shallow burial depth and loose lithology,facing a series of difficult problems such as low temperature drilling fluid rheological control,poor wellbore stability,narrow pressure window,high risk of downhole leakage,shallow gas hydrate formation,etc.,and the drilling safety risk is high.Therefore,based on the existing deepwater HEM drilling fluid system,the laboratory optimized treatment agents such as density reducer E,tackifier XC,inhibitor UHIB,and hydrate inhibitor MEG,and constructed a set of HEM drilling fluid sys-tem suitable for ultra-deepwater exploration.Experimental evaluation results show that this system has lower viscosity and higher shear force,stable rheological properties between 3～25℃,and has good rock-carrying capacity and filter loss reduction effect.The sealing pres-sure is up to 7 MPa,the resistance to drilling cuttings pollution is up to 10%,and the resis-tance to NaCl pollution is up to 15%.It has good pressure bearing,drilling cuttings resis-tance,and salt pollution resistance.This system has been successfully applied in many wells on site.The rheological properties of the drilling fluid are stable,tripping is smooth,the well diameter is well controlled,and complex underground conditions such as downhole losses and natural gas hydrate blockage have not occurred,providing a typical reference sample for the drilling operation of ultra-deepwater and shallow wells.
ultra-deepwaterlow temperature rheologydensity reducerwell wall stabiliza-tionnatural gas hydrate
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