Development of sodium silicate-based inorganic water shut-off composition for low-permeability heterogeneous reservoirs

摘要

The article is devoted to development of low-viscosity water shut-off composition based on sodium silicate aqueous solution with an adjustable mechanism of gelation, the application of which will improve the efficiency of remedial cementing operations in conditions of heterogeneous low-permeability terrigenous reservoirs of Western Siberia. Evaluation criteria for determination of optimal concentrations of chemicals were as follows: gelation time, yield stress and gel plastic strength. Based on the results of the research it was found that sodium silicate aqueous solutions are capable to gel when interacting with chrome alum; it was also determined that changing the sodium silicate - chrome alum ratio makes it possible to adjust strength characteristics and gelation time of the composition proposed. The effectiveness of application of the water shut-off composition developed is confirmed by the results of low-permeability terrigenous core sample filtration studies with water shutoff treatment simulation in heterogeneous layered formation. It has been established that the proposed composition has selective insulating properties and to a greater extent reduces permeability of saturated intervals. After treatment with water shut-off composition it is recommended to inject a 15%- aqueous sodium hydroxide solution in order to restore permeability in oil-saturated interlayers with no destruction of the insulating shield in water-saturated reservoir compartments. Application of water shut-off composition during injection well treatment will make it possible to reduce amount of produced water and involve the previously non-draining oil stocks in the development; in addition, the alkali slug injection will restore filtration properties of oil-saturated intervals and increase oil relative permeability due to the effect of alkaline water flooding