Gregory W. Vargus

Design Methodology for Swellable Elastomer Packers in Fracturing Operations

During past 7 years, swellable elastomer technology has been introduced to the oilfield, and its acceptance has been so rapid that its scope of application has rapidly expanded. Swellable technology employs the principle of elastomeric expansion in hydrocarbon or water to form a permanent seal. With the increasing acceptance of this concept for the oilfield, new applications are being explored, and this paper will discuss the application of swellable elastomer packers (SEPs) in stimulation operations. These applications include acid stimulations and/or hydraulic fracturing operations. During stimulation operations, SEPs are subjected to a very specific set of conditions that significantly affect the sealing performance of the tool(s). Three primary challenges must be addressed when designing SEPs for stimulation applications: 1. The downhole conditions; i.e., the main parameters to which the tool will be subjected such as the downhole pressure and the average temperature of the sealing elements. 2. Anchoring forces; i.e., the forces that occur from the shrinkage of the pipe during the treatment that subject the SEPs to additional forces that do not occur in conventional zonal-isolation applications. 3. Thermal contraction of the sealing element; i.e., the contraction that occurs due to the injection of the stimulation fluids that will cause the temperature of the packer to drop. This phenomenon causes the sealing element to partially contract and will result in altered sealing properties, and ultimately, the loss of the pressure seal. This paper describes the technical challenges and discusses resulting design methodology based on modeling (downhole parameters, anchoring forces) and laboratory testing (thermal contraction measurements) that have been developed to resolve these issues. This design methodology is not limited to stimulation applications but is applicable to any scenario with dynamic loads on SEP applications such as in water injection wells, etc. Finally, case histories are provided to illustrate the successes that have been achieved using the design methodology described.