Effective Acid Diversion and Water Control in Carbonate Reservoirs Using an Associative Polymer Treatment: Case Histories From Saudi Arabia

摘要

Acid diversion and water control are usually addressed as two separate issues in the oil industry. An associative polymer can be used to simultaneously address these two issues in a single treatment. Associative polymer treatments were successfully applied during matrix acid stimulations in onshore and offshore oil carbonate reservoirs in Saudi Arabia. The oil producers were completed as perforated and open hole wells. The associative polymer was applied in combination with acid treatments mainly to: 1) mitigate the preferential stimulation of water saturated zones located near oil producer layers, 2) improve acid diversion in heterogeneous carbonate reservoirs, and 3) restore the productivity of the damaged wells. Extensive experimental studies were carried out to investigate potential use of an associative polymer to control water mobility and act as an acid diverter. Coreflood experiments (parallel cores) conducted on reservoir cores at downhole conditions showed that the polymer treatment has no significant effect on the relative permeability to oil. However, the relative permeability to water was significantly reduced. In addition, the associative polymer was very effective in diverting acid into oil-saturated cores. This paper presents the results obtained from several wells where an associative polymer was applied successfully during matrix acid treatments of damaged wells. All the treatments included stages of associative polymer solutions and 20 wt% HCl with additives. Post stimulation treatments production data, build-up, downhole gauges and production logging confirmed that the associative polymer was very effective in diverting the acid into oil saturated zonesand resulted in a significant reduction in water production.