L41010 Removal of Waterblocks from Gas-Producing Formations

This report on part of the petroleum engineering research describes the work completed by the Bureau of Mines on a study of the effects of water intrusion into capillaries in low permeability reservoir rocks and the development of an effective method for removing the waterblocks. Laboratory and field investigations show that formation damage frequently occurs when water invades low permeability rocks. A method was developed by the Bureau of Mines in the laboratory and in the field to relieve capillary waterblocks in gas wells. Impaired gas permeability was improved by this inexpensive chemical treatment, which lowers the surface tension of the water held in the capillaries of the formation. Effectiveness of the alcohol-surfactant treatment was tested with a variety of chemicals and with sandstone cores cut from rocks having relatively low permeability.

Field tests on 20 gas-producing and storage wells demonstrated the effectiveness and limitations of the method. The productive capacity of some wells was doubled by the treatment. The final test was evaluated by the neutron logging technique for measuring changes in apparent liquid saturation. Maximum apparent liquid saturation was reduced by 52 percent; gas production rate increased from 2.3 to 3.5 MMcfd (million cubic feet per day).