Evaluation and Field Test of Combined Gel and Surfactant Imbibition Technology in High Temperature, High Salinity Fault Block Reservoir

AbstractChemical EOR(CEOR) is one of the most effective technologies for the recovery enhancement of mature high water-cut oilfields. Taking Daqing oilfield as an example, great success has been achieved in Alkali-Surfactant-Polymer(ASP) flooding field applications with incremental oil recoveries exceeding 20%. With the depletion of petroleum resources, CEOR methods attract ever-increasing attentions worldwide and expand to reservoirs with harsh conditions, such as high temperature high salinity (HTHS), low permeability, and complicated fault block etc.CEOR feasibility study was performed for a HTHS complicated fault block with temperature of 78 °C and produced brine salinity at 37570.7 mg/L. Detailed screening and evaluation of CEOR methods including polymer flooding, flowing gel injection, and surfactant imbibition were conducted. Furthermore, core flooding tests were carried out to determine oil displacement performance and optimize injection scheme.Parallel core flooding test proved that 12.8% incremental oil recovery was obtained by polymer flooding. As to flowing gel injection, a heat tolerant gel formulation was developed with good thermal stability at 78 °C within 30 days. An incremental oil recovery of 14.8% was achieved by flowing gel, 2% higher than that of polymer flooding. Through static imbibition test, an nonionic surfactant with good recovery was selected. Core flooding test resulted in 13.5% incremental recovery by surfactant slug. For combined gel and surfactant imbibition technology, 17.8% incremental oil recovery was achieved in core flooding test.Pilot test of flowing gel and surfactant imbibition technology was delpoyed in a fault block with 9 injectors and 26 producers. An incremental oil of 2376 MT was achieved after one year injection.