Activated Completion Fluid for Thermal Heavy Oil Recovery

In thermal recovery of heavy oils, after well shut-in, the filtrates of the completion fluids entering the reservoir formations and water from the injected steam will react with rock minerals and formation fluids at high temperature. This reaction will inevitably damage the reservoir formations in contact. To avoid this damage, an activating completion fluid has been introduced. The activating acid, HJS, is used to activate the residue completion fluid in reservoir formations at certain temperature, and hydrogen ions are released to reduce the pH of the reaction system. This will mitigate the dissolution of formation minerals at high pH which is a cause of formation damage. Several additives such as high temperature swelling inhibitor HTW, high temperature friction reducer HUL, high temperature erosion agent HDB and high temperature corrosion inhibitor HJP were chosen and their optimum concentrations determined. With these additives, an activating completion fluid has been formulated. In laboratory experiments, the activating temperature of the completion fluid is 80℃, and the activating time, 60 min. The use of HJS greatly enhances the dissolution of drilled cuttings by the completion fluid. The ratio of swelling of the completion fluid after aging at 220℃ for 8 h is only 1.11%. The completion fluid is compatible with formation waters, and the turbidity of the mixed fluid is between 3.6 NTU and 6.9 NTU. The recovery of permeability after steam (270℃) flooding is greater than 90% (measured at 80℃). These data demonstrate that the activating completion fluid plays a positive role in protecting reservoir formations.