Incorporating Self-Degradable Fibers into High Performance High Strength Particulates to Combat Losses While Drilling Across Reservoir Section in Extended Reach Well in Middle East Field

Abstract Lost circulation on drilling wells within the fractured limestone reservoir results in a significant loss of time when treating the losses. Furthermore, lost circulation can be detrimental to well productivity due to the damage caused by the influx of lost circulation material (LCM) into reservoir sections. Drilling fluid in these sections is replaced with sea water to mitigate formation damage and to reduce the hydrostatic pressure of the fluid column at the loss zone. Despite using sea water, total losses are typically encountered in these sections. Several conventional LCMs, fibrous and cementitious LCMs have historically been used to mitigate these losses. However, these LCMs could potentially reduce future well productivity and tend to plug surface facilities / equipment during production. Therefore, the application of an effective LCM that would cure the losses while minimizing the formation damage is required. A novel self-degradable fiber-based pill with acid soluble particulates specifically designed to cure losses in the reservoir section. Once placed, the pill forms an impermeable plug inside a fracture that is stable until the completion of the well. Based upon wellbore temperature and pressure, the fibers will self-degrade to prevent any long-term formation damage in the reservoir section that could impact future production. Laboratory tests indicated that a plug formed from the pill seals a fracture width up to 10-mm and withstand differential pressure as high as 1000 psi. The tailored pill design allows for complete self-degradation of fibers and particulate can exhibit solubility with the presence of acid following downhole placement of the pill. This pill was designed to be pumped through either a dummy bottomhole assembly (BHA), through bypass circulation ports above the BHA or an open-ended drill pipe. The self-degradable fiber-based pill with bridging particles was successfully pumped across the 8 ½-in reservoir sections. The plug was placed through bypass circulation ports by spotting the pill above the loss zone. Following treatment, the loss rate was effectively reduced by more than 95% allowing drilling to continue with drilling operations and without any major impact on future well productivity. The self-degradable pill was used for multiple loss circulation treatments with similar results. Deploying the pill at a different depth proved its applicability under different conditions developing into a standard engineered approach for curing losses in reservoir section. Incorporating fiber with degradable property and bridging materials proved the effectiveness of the novel self-degradable fiber to mitigate losses across reservoir zones in Middle East.