Solids-Free Fluid Loss Pill for High Temperature Reservoirs

Abstract

The leakage of reservoir fluids into a wellbore during perforation, workover, or other completion operations is a substantial concern, especially in high temperature wells where existing fluids utilized to mitigate reservoir fluid influx offer poor performance. To maintain the hydrostatic integrity of the wellbore during these operations, a thermally-stable, solids-free fluid loss pill has been developed.The pill is composed of synthetic polymers and cross-linkers in monovalent high-density brine. Under ambient pressure and temperature conditions, the pill flows as a viscous liquid and remains fluid for over six months. Upon exposure to elevated temperatures (200˚F to 375˚F), the pill cross-links to form a robust gel that can act as an appropriately-weighted, low fluid loss pill. This pill can temporarily seal the reservoir, enabling well control during completion operations.Gelled samples of the fluid loss pill have maintained integrity for up to three weeks under HTHP conditions in laboratory testing with minimal signs of collapse. The gel can be readily destroyed with an oxidative breaker providing a substantial reduction in viscosity. At the end of the completion process, the timing of gel removal is completely controlled by the timing of the breaker addition.In addition to gel stability tests, formation damage caused by the gel and the fluid loss of the pill were assessed by core flooding experiments using Berea core plugs. Average fluid loss over 3 days at 320 °F was about 50 mL. Restoration of the Berea core permeability after the treatment exceeded 85% of the initial permeability with low lift-off pressures observed. This paper presents full laboratory data on the development of the thermally-stable, solids-free fluid loss pill including gel stability, fluid loss, and breaker testing.

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Environmental and strength‐enhanced nanosilica‐based composite gel for well temporary plugging in high‐temperature reservoirs

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