Investigation of Water-Swelling Packers

Achieving successful zonal isolation during well completion is critical to minimize early water production. Currently, cementing is the only method used in Saudi Arabian fields to provide zonal isolation. In horizontal sections, cementing becomes a challenge and excessive water production can occur due to channeling. Another method for zonal isolation is to use a rubber elastomer bonded onto a base pipe. The rubber swells in water and provides a seal between the base pipe and the open hole. This article outlines step-by-step qualification testing that was carried out in Saudi Aramco facilities in an attempt to improve zonal isolation in horizontal and multilateral wells. In this study, we present lab evaluation of elastomers at 190 oF using brines of different ionic strengths and pH values. The evaluation involved examining the effect of salinity and pH on the rate of swelling of elastomers. Also, the study investigated the effect of 15 weight-percent (wt%) hydrochloric (HCl) acid on the swelled elastomers, and whether or not the exposure to water after the acid exposure will restore their size. To the best of the authors’ knowledge, no previous work was conducted to examine the impact of these factors on water swelling packers. The elastomer bonded in pipes was tested in autoclaves. The pressure drop across the pipe was measured as a function of time. The influences of pH and divalent cations on water swelling packers were investigated using elastomer samples. Swelling was related to fluid characteristics. Some water swelling elastomers withstood pressures up to 5,000 psi at 190 oF after placing the elastomers in brines with salinities up to 200,000 mg/l. The swelled elastomers shrank in 15 wt% HCl. Calcium chloride (CaCl2) completion fluids at 72 pounds per cubic foot (pcf) failed to swell the elastomers. The swelled elastomers shrank in 15 wt% HCl acid and their swelled size was not regained after soaking in water. This article discusses the advantages and limitations of swelling elastomers and gives recommendations for field application.