Abstract
This paper presents successful field implementations of a high-temperature polymer (HTP) for water and gas-shutoff applications in highly naturally fractured carbonate reservoirs with BHT > 250°F. Fifteen case histories in a naturally fractured carbonate reservoir in Mexico (inland and offshore operations) are presented in which the HTP system was successfully applied to reduce water production. One-year, post-production data is reported for each case.
The HTP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). To date, more than 600 jobs have been performed with the HTP system around the world to address conformance problems, such as water coning/cresting, high-permeability streaks, gravel-pack isolation, fracture shutoff, and/or casing-leak repair. Originally, the HTP system had a limited working temperature range from 100 to 250°F. The upper placement temperature of the system was ~250°F as, above this temperature, pumping times were too short. A recently developed carbonate retarder allows reasonable placement times up to 350°F, without the need for cooling down the formation to obtain enough pumping time. The retarder is not detrimental to the thermal stability of the system. The development results of this HTP system are also discussed.
The HTP system has been successfully applied to sandstone, carbonate, and shale formations requiring a conformance treatment. This system has been successfully tested to withstand a differential pressure of at least 2,500 psi and is resistant to acid, CO2, and H2S environments. To date, more than 100 jobs have been successfully performed worldwide with the HTP at temperatures higher than 250°F with the recently developed retarder. Because of the capability of the HTP system to withstand pressure, workover operations have been successfully performed in previously treated wells, including acid stimulation, sand control, and frac-pack treatments, among others.
