The primary purpose of surfactants used in stimulatingSandstone reservoirs is to reduce surface tension.Conventional surfactants adsorb rapidly within the first fewinches of the sandstone formations, thus losing theireffectiveness as the treating fluid leaks off. This results intrapped fluids and poor post fracturing fluid recovery. Asurfactant solvent system in the form of a microemulsion canalso be used to not only lower surface tension at very diluteconcentrations, but alter contact angle and lower capillarypressure to further improve recovery. The unique microcellsare also effective in controlling leakoff.This study describes the laboratory experiments and fieldcase studies of various surfactants used in the oilfield. Severalsurfactants including an ethoxylated linear alcohol, a nonylphenol ethoxylate and a microemulsion system wereinvestigated to determine their adsorption properties wheninjected into laboratory sand packs. Laboratory studies werealso conducted to compare the leakoff and water recoveryproperties from gas wells.Field data collected from Bradford and Speechleysandstone formations confirms experimental sand pack andcore flow investigations. Reservoirs treated withmicroemulsion fluids demonstrate exceptional waterrecoveries when compared with conventional surfactanttreatments. Wellhead pressures, flowing pressures andproduction data were collected and evaluated using aproduction simulator to show effective fracture lengths anddrainage areas with various fluid systems.Lab and field data collected in these studies fromAppalachian Basin reservoirs illustrates that the addition of amicroemulsion to a fracturing fluid exhibits significantadvantages over the conventional surfactant treatments when water recovery, increased effective fracture length and wellproductivity are of concern to the operator.
展开▼
