Inflatable packers are ideal for through-tubing zonal isolation, but they are rarely used in extreme environments because of the assumed risk of failure. High pressures, high temperatures, high expansion ratios, and chemical resilience are particular challenges. This paper reports on three recent case histories that demonstrate inflatable packer technology can be used in several of these "harsh" wellbore conditions.
The first case history describes a high-pressure cement squeeze job using a 2 1/8-in. packer with an expansion ratio larger than 3:1. The objective was to run the packer through a 2.313-in. restriction and set in 7 5/8-in. casing to permanently shut off a lower water zone before perforating higher in the well. The second study involves an inflatable packer used in conjunction with a butyl acetate furan resin for sand consolidation. The furan resin is known to be extremely detrimental to elastomers, so a full-scale simulation under given wellbore conditions was conducted to demonstrate its compatibility with the packer. The resin was utilized as a screenless sand-control solution that allowed fullbore production. The final case history involves pumping of a viscoelastic acid-diverting treatment fluid, used for matrix stimulation under high-pressure, high-temperature conditions. Used in carbonate formations, the fluid is ideally suited for total zonal coverage matrix simulation and high temperatures. When a through-tubing inflatable packer is used as a treating packer, individual long producing zones can be fully isolated and evenly stimulated.
As the burden of R&D spending in the oil field shifts to service companies, many new technologies are being introduced for well intervention. Combining multiple systems or processes can yield new and unique solutions to old intervention challenges. This is particularly true when considering recently developed chemicals for which accurate placement and maximum treating length are critical in determining the success of the operation. In many wellbore completions, isolation of particular zones is required for successful treatments. For placement in completions with production tubing, coiled tubing (CT) is increasingly used as a conveyance mechanism; the isolation and placement can then be achieved through the use of new inflatable technology. The combination of new chemistry with new downhole hardware is a fruitful area of research, but compatibility between new technologies requires testing and confirmation. Two technologies may provide success when used separately but fail when used together.
Moreover, a great deal of well intervention focus and development is also being placed on reservoir control and abandonment, with techniques such as water conformance and sand control gathering pace in the intervention fluids market. The ability to isolate individual intervals is again imperative to the successful shutoff of a particular zone. As the fluids push the envelope to treat higher-temperature reservoirs, temporary and permanent inflatable packer technology must follow in step.
The potential or anticipated requirement for extreme through-tubing acid stimulations, water and sand conformance has traditionally forced the operator to retrieve the production tubing and then perform any isolation technique other than inflatable packers.
Traditionally, stimulating wells with production tubing without inflatable assisting equipment meant that formations could not be stimulated selectively or could only be stimulated using less-effective diverting techniques. Inefficient fluid placement treatment and previous failed inflatable attempts from incompatibility in the extreme environments resulted in extended nonproductive time with a late payback that wiped out the investment for the production enhancement.
Clearly this situation could not satisfy the industry because it reduced the inherent advantage of inflatable technology: minimized costs per length of pay zone. Noting that the majority of high-cost completed wells are multilayer, a means was required that allowed successful individual zonal isolation in more harsh environments and that allowed the use of available treatment chemicals on the market. Finally, the inflatable zonal isolation technique had to be reliable and fast, reducing overall treatment costs and enabling quick payback.