Abstract
Oil reservoirs in the Lloydminister region, Canada, are produced through the process of Clod Heavy Oil Production with Sand (CHOPS). Implementation of CHOPS in these fields causes the formation of wormholes, which leads to production of excessive water and abandonment of the wells. In order to reduce the excess water production from wormholes, variety of techniques have been suggested and tested with minimal success. Blocking the wormholes by the means of clay, polymer-gel systems, and gel-foams are among the proposed methods. This paper presents the results of a series of experiments conducted in order to develop and test the applicability of a new gel-foam system for blocking wormholes in oil reservoirs. As a result, a new gel-foam system was invented that creates stable foam in wormholes for the duration of gelation time. The composition of the gel-foam was based on polyacrylamide cross linked with chromium(III), plus a mixture of solutions of two commercially available surfactants. These commercially available surfactants were tested at various concentrations and ratios to develop the most stable gel-foam system. An experimental set up was designed and built which allowed for two layers of unconsolidated sand as the matrix separated by a high permeability wormhole between them. The effect of various sizes of wormholes on the performance of this gel-foam system was tested. All experiments were conducted at atmospheric pressure and constant temperature of 30°C, with some experiments in the presence of residual oil. For all the experiments the residual resistance factors to the flow of water in high permeability pathways were in the range of 25 to about 200. The results obtained are clear indication of the effectiveness of this newly developed gel-foam system for blocking wormholes and other high permeability pathways in reservoirs.
