Advanced Noncement Options for Isolating Wellbores
- _ JPT staff (_)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 2008
- Document Type
- Journal Paper
- 36 - 38
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Technology Update - Information provided by Ed Wood, Sean Yakeley, Jesse Constantine, and Jody Augustine, Baker Hughes.
For today’s long horizontal wellbores and multilateral completions, competent zonal isolation is especially critical. But cementing and perforating multiple zones is costly and time consuming, requires specialized equipment and personnel, can cause near-wellbore formation damage, and poses safety and environmental risks. Alternative isolation technologies now can reduce costs and improve well productivity through more effective fracture treatment and better inflow management. Among these new options, reactive-element (RE) technology and other fit-for-purpose packer systems are field-proven solutions for a variety of zonal isolation challenges.
Much more of the world’s oil and gas can now be recovered economically by exposing to the wellbore long stretches of reservoir that typically contain several pay zones. Without cost-effective zonal isolation, however, the full potential of advanced drilling and completion technology to increase production, ultimate recovery, and profitability cannot be realized. Efficient, practical zonal isolation is also important in solving fluid-loss problems while drilling and in reviving mature wells.
With new, noncement isolation methods, it is possible to achieve uniform flow in highly productive wells, perform multiple fracture treatments in carbonate and shale reservoirs, and employ inflow control devices (ICDs) to man-age flow without well intervention. All of these capabilities extend a well’s productive life and profitability.
Two Key Drivers
Isolating well intervals without cement is not a new concept, but recent growth in commercial use has been driven by such challenges as the need to fracture tight gas formations and to regulate flow in high-rate wells.
Two means of achieving cementless isolation are the use of
- RE packers with swelling-elastomer elements that self-energize in reaction to water and/or hydrocarbons
- Hydrostatic/mechanical packers, set hydraulically
The latter type of packer often is used with an ICD.
For a fast-growing number of diverse zonal isolation challenges, an RE packer is an efficient, cost-effective alternative to cementing and perforating. RE-packer completions are simple to deploy and require fewer trips, no running tools, and no specially trained personnel on site. RE devices are usable in both oil and gas producers.
Elastomeric-polymer sealing elements in the packer react with oil or water to swell and seal off the annulus between liner or casing, and open hole. The water-reactive element consists of particles contained in a nitrile-based polymer that swell by absorbing water. The rubber expands without the particles being physically absorbed in the rubber matrix. Oleophillic polymers in the oil-reactive element absorb hydrocarbons into the matrix.
The swelling mechanisms are not reversible, so the element will not shrink if fluids are changed after swelling. Tests show negligible contraction in the elastomer when exposed to natural gas. RE packers are rated for temperatures to 300°F and pressures to 10,000 psi.
RE-packer applications include water shutoff and the isolation of cement shoes, lateral junctions, and fractures. A special type of RE packer can be field-installed onto existing tools for added flexibility in deployment. Another RE tool can be used as a debris barrier.
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