Laboratory studies of polymer compositions for well-kill under increased fracturing

Well-service under increased fracturing is often complicated as early as at the stage of well-killing operations. The presence of cracks in the reservoir formation can result in significant absorption of drilling fluid, as well as in bottomhole gas breakthrough. The laboratory studies are required to develop a blocking agent for reliable isolation of highly permeable reservoir intervals without a negative impact on the reservoir porosity and permeability and in compliance with operational safety requirements. For the purpose of this work, the physical, chemical and rheological properties of frame-forming and gel-forming compositions, which are cross-linked systems prepared on the basis of soluble silicates, have been studied. The well-killing technology implies their consecutive injection into the well. The reviewed compounds have proven their applicability in a wide range of reservoir temperatures, which provided for the possibility of their injection into a standard well and flushing into the bottomhole formation zone due to low viscosity and slowed cross-linking. Breaker application allows us to almost completely eliminate negative impact of this technology on filtration characteristics of the bottomhole formation zone after well-killing. The studies conducted within the scope of this work have shown application efficiency of blocking polymer compounds and opened new directions for further researches, including the necessity to undertake a sequence of laboratory and field tests of the reviewed agents, which will enable to select and validate optimal technological and economic parameters of the operation. The results obtained can be used to improve the efficiency of oil and gas well-kills under increased fracturing during well-service operations.