The oil and gas sector has witnessed a marked inclination worldwide towards enhanced oil recovery (EOR) in recent years due to diminishing easy oil in many fields. One of the more popular EOR strategies is the workover method of converting existing weak horizontal producers to maximum reservoir contact (MRC) wells, or dead vertical wells to single horizontal producers or power water injectors. This attempt at maximum well productivity and total oil recovery is based on installation of downhole smart systems to control flow from each lateral. Expandable liners and swelling elastomers are the key drivers enabling this type of zonal isolation. Enhancement and maximization of hydrocarbon recovery is also being attempted through intelligent and multilateral wells. These well systems cannot succeed without proper zonal isolation and compartmentalization of the reservoir. Compared to conventional methods, swelling elastomer packers maintain good zonal isolation in even the most complex environments, yielding major savings in rig time and cost.
As yet, no data is available from designers or manufacturers about the durability or service life of swell packers under actual well conditions. A full-scale rig has therefore been designed and fabricated at the Sultan Qaboos University (SQU), in collaboration with a regional petroleum development company, for longevity testing of water-swelling and oil-swelling elastomers. The test battery includes packers made from different swelling elastomer materials, exposed to actual crude oil or water of different salinities, maintained at different temperatures, and subjected to high pressure. Different conceptual designs of the test setup (for longevity testing over a 5 year period) were developed and later evaluated. Detail design of the best concept was carried out and assessed for reliability, manufacturability, assemblability, etc. Salient features of the final design include thermal systems for selected packers, able to continuously maintain temperature over the 5-year period; recirculation system to maintain the desired salinity in some packers; elaborate system for measurement and observation of upstream and downstream temperature and pressure in all tubes; a system for pressurizing the tubes (to 1000 psi) once the elastomers have swelled and sealed. Daily log of readings have been maintained over the last few months. Several months of testing has shown that packers exposed to low salinity and higher temperatures have sealed earlier, and water-swelling elastomers have sealed faster than oil-swelling ones. Three units have not sealed yet, one tube has desealed after initial sealing, one packer has shown seal failure after pressurizing, and two units are exhibiting good sealing under high pressure. Most of these results are in line with material behavior of swelling elastomers observed in earlier laboratory tests. The whole test battery will be monitored over five years, reporting seal temperatures, pressures, seal deterioration or failure, etc. This study can provide direct feedback to field engineers about the lasting capability of different elastomer types under various actual field conditions. This not-as-yet-available information will be valuable in proper selection of swell packers, and may also help in improvement of packer design.
Long-Term Integrity Testing of Water-Swelling and Oil-Swelling Packers
