A Study on the Effect of Acid Injection with Surfactants on Malaysian coals for CBM Study

Acid injection is one of the well stimulation technique that usually been imposed on sandstone, but rarely been implemented for CBM recovery. This research will focus on the study consisting the effect of acid injection with surfactant on the CBM recovery which is also known as Enhanced Coal Bed Methane (ECBM). This research will attempt to resolve the formation damage problem by introducing surfactants that could probably avoid the formation damage, thus will assist acid injection to increase the permeability of the CBM. The surfactant is employed in an aqueous acid solution, preferably having pH equal to or less than 3.0. The method is carried out by injecting the aqueous acid solution containing alcohol and also SLS (Sodium Lauryl Sulfate) that act as surfactant into a coal sample, preferably at injection rates lower than that would fracture for formation or at matrix injection rates. Tests have shown that the acid solution containing surfactant at certain concentration permit stimulation of the formation without damaging the formation itself. The acid solution is believed to act for dissolving calcareous materials in the cleats and the surfactant modifies the wettability of the coal surface which will lead to the improvement of permeability either water or methane or both. Actually, the acid stimulation will improve the formation permeability for the water in the dewatering stage. When sufficient water has been produced from the formation through the interconnected cleats, the resultant reduced pressure allows the methane to desorb from the coalbed formation and flow into and through the interconnected cleats into the wellbore. In this study, ECLIPSE 300 software is used as the initial result on how the surfactant injection will impact the water and methane production from the Coalbed Methane, before proceed to the laboratory tests. Laboratory tests include the utilization of Gas Adsorption Column Unit (GACU) to measure the adsorption capacity, an experiment to measure the porosity and moisture content of the coal and lastly the usage of Mercury Porosimeter equipment to measure the permeability impact of acid and surfactant injection into Malaysia coal sample for CBM study. The permeability for both, water and methane are expected to be increased after injecting acid solution with surfactants of various concentrations.