Abstract
The scale inhibitor squeeze treatment is a well-known method widely used in the oilfield to prevent mineral scale formation. Squeeze lifetimes are dependent on a number of factors. Some of these factors are reservoir temperature, brine composition, reservoir mineralogy, and inhibitor chemistry. In an attempt to reduce the number of squeezes in a given well, thereby simplifying the logistics and improving the economics of the treatment, modifications to the procedures have been developed that are targeted at extending squeeze lifetimes. The improved performance of scale inhibitor squeezes coupled with increased squeeze lifetimes are especially important for critical applications in environmentally sensitive areas.
In situ adjustments to the reservoir brine pH, calcium or zinc ion supplementation, microcrystalline kaolin addition, and the incorporation of chemical bridging agents have been used with varying degrees of success. These methods, while offering a degree of squeeze life enhancement, are not without their drawbacks. Methods involving pH adjustment or calcium ion supplementation create the opportunity for damage caused by excessive precipitation of solids. The injection of microcrystalline kaolin is inherently troublesome in that solids are intentionally introduced into the formation. Many chemical bridging agents often have temperature limitations restricting their use to a few select reservoirs or have undesirable environmental profiles.
Recently, laboratory investigations have been conducted using a new class of non-polymeric (MW 250 to 500) squeeze life enhancement, SLE, agent. Core floods have been run using commercially available scale inhibitors in the presence of the new products generating results that show dramatically improved squeeze lifetimes. Unlike some of the products currently in use, these new SLE agents possess a much better environmental profile, being biodegradable, non-bioaccuulating and having much lower toxicity. While providing much longer effective squeeze lifetimes, the SLE agents are not permanently adsorbed onto the rock surface. The improved SLE agents are thermally stable to 180°C (~350°F) allowing use in a wide range of locations.
