Wen-120 block formation in Huabei Oilfield belongs to the typical complex fault block sandstone reservoirs. It is characterized by high heterogeneity, poor water sweep efficiency, high water cut and inefficient oil recovery during the post-water flooding period. The selection of enhanced oil recovery (EOR) technique is very important for future development of such reservoirs. Foam flooding can improve macroscopic sweep efficiency, which may increase oil recovery for highly heterogeneous reservoirs particularly. One of key techniques of foam flooding is to develop foam formulation to fit the reservoir conditions, especially in the harsh reservoir fluids conditions. In this study, systematic laboratory studies on foam flooding formulation for Wen-120 formation have been performed.
Foam flooding formulations were investigated based on foaming agents and foam stabilizers screening tests, oil sand adsorption experiments and oil displacement core flooding experiments under the target reservoir conditions (reservoir temperature is 80.4 °C, total salinity of formation water is 22,520 mg/L). The research results would lay the foundation of foam flooding EOR pilot test for the fault block reservoir.
The results showed that: (1) a compounded system of surfactant AOS and FC-1 mixture acted as foaming agent, and polymer KYPAM as foam stabilizer were selected, the foam formulation showed a good salt-tolerant and oil-resistant properties. (2) both of the good foamability and stability was obtained within concentrations of foaming agent of 0.4wt% and foam stabilizer of 1,400 mg/L. (3) the foam system still has higher foamability and stability after four times static adsorption. (4) EOR effect evaluation on core flooding indicated that foam flooding could contribute 24%-32% of OOIP incremental recovery under good operating protocols.
Foam flooding integrates both properties of gas injection technique and chemical flooding. It is a candidate EOR method which has great potential to be applied on highly heterogeneous complex fault block sandstone reservoirs.