Studies on Nanoparticle-Stabilized Foam Flooding EOR for a High Temperature and High Salinity Reservoir

Abstract Foam is a mixture of gas and water where the gas is dispersed as bubbles in a continuous liquid phase. Foam flooding is one of chemical enhanced oil recovery (EOR) technologies by using foam fluid's "Jamin effect". Field tests showed that the EOR performances of foam flooding depend largely on both foamability and stability of foam under reservoirs conditions. To enhance foam stability, high molecular-weight polymer as stabilizer was generally introduced into foam solution. However, in high temperature and high salinity (HTHS) reservoir condition, this function of polymer was limited being the degradation of their large molecules. Therefore, it is necessary to call for an alternative stabilizing agent. DL offshore oilfield is one of HTHS reservoirs with reservoir temperature of 100-120°C and salinity of 34,370 mg/L, which has entered high water cut stage. The selection of EOR technique is very important for future development of such reservoirs. In this case, foam flooding with nanoparticle replace polymer acted as foam stabilizer was proposed. Nanoparticle-stabilized foam formulation was studied under the target reservoir conditions. The nanoparticle-stabilized foam formulation was screened by static bulk foam tests. Though foaming agent and nanoparticle types screening tests, the effect of nanoparticle on the stability of foam system was investigated by measuring the foam properties of the foamability (foaming volume) and stability (drainage half-life). The distribution of nanoparticle size was analyzed. The injectivity and resistance factor (RF) of nanoparticle-stabilized foam fluid were studied on core flooding. Core oil displacement experiments of nanoparticle-stabilized foam flooding were conducted at the reservoir condition. From the nanoparticle-stabilized foam system screening tests, α-olefin sulfonate (AOS) and fluorocarbon surfactant as foaming agent and clay nanoparticle as foam stabilizer were selected. The results showed that clay nanoparticle could greatly enhance drainage half-life of the foam system. More dense foam was formed in nanoparticle-stabilized foam fluid. Injection experiments of nanoparticle-stabilized foam on core showed a good injectivity when core permeability was more than 200 mD. RF of foam fluid showed that nanoparticle-stabilized foam had good mobility control function. EOR effect evaluation on core flooding indicated that foam flooding could contribute 17%-21% of OOIP incremental oil recovery under good operating protocols. The experimental results were considered to be technical feasibility and effectiveness of nanoparticle-stabilized foam flooding EOR methods for DL reservoir, which might present further understanding for nanoparticle-stabilized foam flooding EOR field application on the HTHS reservoir.