Abstract
A successful cross-linked polymer flooding has been implemented in JD reservoir, an ordinary heavy oil reservoir with high permeability zones. For all that, there are still significant volumes of continuous oil remaining in place, which can not be easily extracted due to stronger vertical heterogeneity. Considering selective plugging feature, polymer enhanced foam (PEF) flooding was taken as following EOR technology for JD reservoir. For low cost and rich source, natural gas was used as foaming gas in our work. In the former work, the surfactant systems CEA/FSA1 was recommended as foam agent for natural gas foam flooding after series of compatibility studies. Foam performance evaluation experiments showed that foaming volume reached 110 mL, half-life time reached 40 min, and dimensionless filter coefficient reached 1.180 when CEA/FSA1 reacted with oil produced by JD reservoir. To compare the recovery efficiency by different EOR technologies, series of oil displacement experiments were carried out in a parallel core system which contained cores with relatively high and low permeability. EOR technologies concerned in our work include further cross-linked polymer (C-P) flooding, surfactant-polymer (S-P) flooding, and PEF flooding. Results showed that PEF flooding had the highest enhanced oil recovery of 19.2 % original oil in place (OOIP), followed by S-P flooding (9.6 % OOIP) and C-P flooding (6.1 % OOIP). Also, produced liquid percentage results indicated PEF flooding can efficiently promote the oil recovery in the lower permeability core by modifying the injection profile.
Highlights
Chemical flooding has been widely used in ordinary heavy oil reservoirs in China (Zhou et al 2006, 2013; Gao 2011; Hou et al 2013a, b; Zhang et al 2014)
A successful cross-linked polymer flooding has been implemented in JD reservoir, an ordinary heavy oil reservoir with high permeability zones
Considering selective plugging feature, polymer enhanced foam (PEF) flooding was taken as following EOR technology for JD reservoir
Summary
Chemical flooding has been widely used in ordinary heavy oil reservoirs in China (Zhou et al 2006, 2013; Gao 2011; Hou et al 2013a, b; Zhang et al 2014). Stronger heterogeneity of post cross-linked polymer flooding reservoirs makes injected fluid prefer to flow through highly permeable thief channels, rather than displace the remaining oil in low permeability areas,where a mass of remaining oil locates as continuous state. The fluid and gas can be injected to the core clamping system, which included two cores with different permeability This kind of design can reflect the vertical heterogeneity of real reservoirs. In the chemical flooding selection experiments, the accuracy of the temperature was ±0.5 °C, the flow rate was limited to 0–30 mL in the control apparatus of gas mass flow, the pressure was limited to the range of 0–10 MPa in the back-pressure valve and the pressure-controlling accuracies of both the back-pressure valve and digital pressure gauge were 0.01 MPa. Materials used in experiments included natural gas, crude oil, AS-polymer, JRJL-3 crosslinker, JRJL-3 modifier, and surfactants.
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