Implementation Time of Chemical Flood and its Impact on Ultimate Recovery
A.J. Alshehri and A.M. Khatib
Event name: IOR 2015 - 18th European Symposium on Improved Oil Recovery
Session: Poster Session
Publication date: 14 April 2015
Info: Extended abstract, PDF ( 1.1Mb )
Price: € 20
During water flooding processes, injected water disconnects oil droplets as it flows through pores/throats in the reservoir. These disconnections are a consequence of capillary effects hindering the mobilization of oil through pores/throats of the reservoir. Due to this capillary trapping, mobilizing the remaining oil in place by any enhanced oil recovery (EOR) process becomes very challenging. Chemical flooding has been identified as an effective EOR method which is usually implemented in tertiary mode, where field development has reached a mature level. At this stage, the efficiency of waterflooding processes in terms of mobilizing remaining oil declines due to capillary trapping. Chemical EOR processes such as surfactant flooding are used to reduce this trapping and mobilize the remaining oil. Surfactants are used to reduce the interfacial tension which consequently reduces the capillary pressure effects responsible for trapping. Although most EOR processes have been implemented in tertiary mode, earlier implementation is more desirable because capillary trapping is less prominent. This study investigates the impact of post-waterflood implementation time of surfactant flooding on ultimate recovery and net present value (NPV) given this capillary trapping. A series of numerical experiments were conducted to test this effect while accounting for operating expenses associated with both flooding options. Capillary pressure curves for the waterflood case and the chemical flood case were added to incorporate capillary trapping effects. Then, the chemical-flood implementation time was varied to evaluate its impact on the ultimate oil recovery. These experiments were performed on a number of stylized reservoir models while varying field size: a 1-D coreflood model, the PUNQ-S3, SPE10 reservoir model and a synthetic fractured reservoir model that is analogous to a Middle Eastern carbonate fractured reservoir. The implementation was conducted by an algorithm that was written in MATLAB and was coupled with a commercial reservoir simulator. Results show that the sooner chemical EOR is implemented the higher the ultimate recovery of the process. Due to the relatively large initial investment and operating expenses associated with chemical flooding, water flooding is more attractive from an NPV perspective.