Aqueous Polymers for Treating Clays in Oil and Gas

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American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Protection of water sensitive formations Protection of water sensitive formations is a serious problem in the production of hydrocarbons. Water sensitivity is usually the result of fines migrating which is triggered by introduction of foreign water. The migrating fines tend to lodge in constrictions in the formation flow channels where they severely reduce production. Water sensitivity can be simple clay swelling, but fines migration causes more permanent damage. However, swelling of clays in fines is an important mechanism for dislodging fines and starting the migration. The sodium clays are the important form of swelling or dispersing clays. Since sodium ion is easily replaced by others a successful method of helping to prevent swelling and migration is to treat the clays with potassium, calcium, ammonium or hydrogen ions. With these ions the clays are relatively inactive if not quiescent. However, this is temporary protection because sodium ion from formation water protection because sodium ion from formation water quickly counter replaces the non-swelling ions and the clay returns to the swelling or dispersing form. A new series of certain polymer materials has proved to be effective in treating water sensitive formations. These polymers adsorb tenaciously to surfaces of clay minerals and other formation fines, helping to prevent clays from swelling and fines from migrating should foreign water be introduced into the formation. The polymers win easily in competition with other simple ions (such as ammonium, calcium or potassium) for being deposited on clay surfaces. Furthermore, once deposited on clay surfaces, the polymers are not easily replaced by exchange with other ions. Subsequent acidizing treatments cause no detectable harm to the ability of the polymers to protect the clay. protect the clay. Laboratory test data with sand packs and cores are presented and annotated. The encouraging results of these tests are supported by the results of fracturing treatments, acidizing treatments, and other operations, which are tabulated and discussed. Introduction Many oil and/or gas producing formations contain clays, clay minerals, silica fines, and other fines.

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