Swelling Packers; Lab Testing and Field Application (2008)

Abstract The best well completion is the lowest cost one that meets the demands for the well during its life time. There are different aspects that we need to consider when designing completion such as reservoir consideration (Allen and Roberts, 2006).We can have openhole completions, perforated casing completion, or horizontal completions. In this study, we present lab evaluation of oil and water swelling elastomers for potential field application in Saudi Arabia fields. Oil and water swelling packers were examined in the lab (measuring pressure difference across swelling packers in autoclaves at 190°F and testing against various salinity fluids and pH using coupons at 190°F). Crude oils with various properties were used to test the oil swelling packers. Water swelling packers were tested in aqueous fluids with various pH values and salinities. Oil swelling packers showed acceptable pressure drops across the packer for six crude oils. They were resistance against acids and different brines. Oil swelled elastomers were tested with different salinity fluids to simulate the effect of produced water on the oil swelling packers. They were also tested against various acids to simulate possible stimulation treatments. The water swelling packers showed acceptable results for all fluids tested except at high and low pH fluids. This limits their use in wells with potential acid treatments. Oil swelling packers were used successfully in 16 oil producers. Cost saving on the rig time was achieved with swelling packers to cased-hole completions. Up to 22% of the rig time was saved due to the elimination of running casing, cementing, using whipstock and casing milling. To date, all wells completed with oil swelling packers are showing good results for close to three years. Introduction Packers can be classified either as retrievable or permanent type. Some types of retrievable packers are: compression, tension-set, mechanical-set and hydraulic-set. Compression packers are suited for low pressure cases where the pressure above packer exceeds tubing pressure below it. Tubing weight is applied down to expand the packing element. Tension-set packers are suited for injection wells or stimulation operations where the pressure below packers exceeds the tubing above it. In this case, tubing weight is picked up to release the packer. Mechanical-set packers are used for higher pressure cases. The setting mechanism is tubing rotation. Hydraulic-set packers use wellbore fluid pressure to act on a piston-cylinder as a part of the setting mechanism. The other classification is permanent packers, which may be run on tubing or electric conductor cable. Tubing can be run separately from the packer so trip time is faster (Allen and Roberts, 2006). Swelling packers are new technology to provide long-term isolation of certain zones used for selective production. Evaluation and validation of this new technology is still under progress. In some cases, swelling packers have been used to replace packers, which are operated using mechanical and hydraulic means. In other cases, they have been used to replace cement columns pumped through liners to provide zonal isolation. While water swelling packers use water as the medium source, oil swelling packers use hydrocarbons for swelling process. Practically, swelling packers need 5–100 days to complete the swelling process. Several parameters affect the time needed to swell the packers: water salinity, temperature, oil viscosity, and composition, Heroid et al., 2006.