Scale Prediction and Remediation for Deep Water Fields

摘要

Completion technologies for horizontal and subsea deep-waterwells have been developed to make feasible and increaseoil production.Horizontal and subsea wells in Petrobras are usuallylocated at long distances from production facilities and indeepwater. Scale control can be implemented on these wellsvia bullhead treatment along a service line or downproduction lines.The scale potential for deepwater fields from CamposBasin, Brazil, was assessed. Thermodynamic model predicteda moderate barium and strontium sulfate precipitation inproduction wells (down hole). More severe precipitation waspredicted for the lower temperature of the risers (10 to 20°C).Despite of the predictions based on thermodynamiccalculation, experimental work performed consideringconditions of temperature, residence time and chemistry ofproduced water showed that precipitation is expected inreservoir rather than in the risers. Laboratory results agreewith field data observation. Data from gamma ray log obtainedin recent intervention caused by productivity loss in one wellof these fields, showed that scale was formed in the productionwell (screen, gravel and reservoir) rather than in the flow lines.Chemical dissolution treatment was designed and applied inthe wells from this field restoring their productivity.