Subsurface Sludge Sequestration in Cyclic Steam Stimulated Heavy-Oil Reservoir in Liaohe Oil Field

Abstract

Summary There are a lot of sludges produced in oil production and storage processes in Liaohe Oil Field. Usually complicated chemical processes are involved in treating the sludge effectively and such surface-treatment processes are subject to high cost and environmental challenges. Therefore, the feasibility and performance of sludge injection into steam-stimulated wells, and sludge sequestration and associated heavy-oil-recovery improvement are investigated on the basis of results of laboratory research and field operation. The sludge originally produced from the reservoir comprises mainly water, some oil components, and solid phase such as mud and fine sand, and aggregation of the injected sludge components, except water, could block the void porous space. Actually, the sludge is buried into its origin, the reservoir. As the sludge is injected into the steamed reservoir through an enlarged pore at high injection pressure, the permeability of the formation could be significantly decreased (the permeability reduction rate could be more than 98% after sludge blocking in our experiments with sandpacked tubes), and the sludge blocking performance is related to the reactions of oil and solid separated from the sludge, including adherence to the sand surface, consolidation of the sands, and filling in the void porous space. Consequently, the sludge is stored in the steamed formation, and the water in the sludge is separated and produced. At the same time, steam conformance and heating efficiency could be improved by implementing a sludge blocking process, thereby significantly improving oil production. Sludge sequestration has been applied to 45 steamed wells in Shuguang Oilfield until 2018, and all the wells have been stimulated by 7–10 cycles of CSS process. The total sludge injection of the wells is up to 133,200 tons, and more than 15,000 tons of oil and solid separated from the sludge are deposited underground. At the same time, more than 20% increase in cyclic oil production on average is obtained by the sludge-injection process.

Investigation of Polymer-Assisted CO2 Flooding to Enhance Oil Recovery in Low-Permeability Reservoirs

“…Meanwhile, the molecular modification of the polymer can play an interface effect, stripping, dispersing, and carrying oil droplets [13]. In addition, polymer gels [14], polymer microspheres [15][16][17], polymeric surfactants [18], and other agents [19] can play a role in profile control and flooding, further improving oil recovery. A comparison of the EOR effects of different enhanced CO 2 injection methods is shown in Appendix A Table A1.…”

A gel system with long‐term high‐temperature stability for deep profile modification of high‐temperature oil and gas reservoirs

“…[32][33][34] For example, the reservoir temperature in the fourth area of Jidong Oilfield of PetroChina reaches 140 $ 160 C. 35 The depth of the reservoir in the Northwest oilfield of Sinopec reaches 8520 m, while the temperature of the reservoir is as high as 155 C. 36 In addition, for some heavy oil reservoirs developed by steam injection, the reservoir temperature can also reach higher than 120 C. To solve the water production problem of the above reservoirs, scholars have also carried out a lot of research. [37][38][39] Prada 40 developed a gel system with a temperature resistance of 120 C using terpolymer and chromium crosslinked agent. Zhu 41 studied an organic crosslinked gel system and analyzed its high-temperature resistance (120 C).…”

“…In addition, for some heavy oil reservoirs developed by steam injection, the reservoir temperature can also reach higher than 120°C. To solve the water production problem of the above reservoirs, scholars have also carried out a lot of research 37–39 . Prada 40 developed a gel system with a temperature resistance of 120°C using terpolymer and chromium crosslinked agent.…”