Development of blocking compositions with a bridging agent for oil well killing in conditions of abnormally low formation pressure and carbonate reservoir rocks

Abstract

Production well killing before workover operations in late-stage oil and gas-condensate fields can be complicated by abnormally low formation pressure, carbonate type of reservoir rocks, and high gas-oil ratio. These complications lead to the intensive absorption of technological fluids by the formation and gas ingresses, which, in its turn, increases the time of killing wells and putting them on production, reduction of productivity, and additional costs. Therefore, it is crucial to develop a high-performance well-killing composition that would allow improving the efficiency of killing wells in complicated geological, physical, and technological conditions at the expense of reliable overlapping of the perforation interval (or open wellbore) to prevent gas intakes and gas outflow from the formation. To develop blocking compounds, a set of laboratory tests has been carried out, including physical and chemical (determination of density, viscosity, thermal stability, sedimentation stability, etc.) and research of blocking and filtration properties of compositions during simulation of a fractured reservoir. In the course of laboratory tests, the choice of fractional composition and polymer filler concentration was substantiated in the blocking emulsion and polymer compositions to increase the efficiency of their application under the complicated conditions of killing oil wells. As a result of laboratory research and field tests, the emulsion and polymer blocking compositions containing bridging agent (microcalcite) were developed, which increase the oil well killing efficiency by preventing the absorption of technological fluids in the formations and, as a result, preserving its productivity.