Abstract
Surfactant-polymer (SP) flooding has been demonstrated to be an effective method to recover oil in the enhanced oil recovery (EOR) stage when water flooding is no longer relevant. Theoretically, adding surfactant causes the reduction of the interfacial tension between oil and water in pores, therefore reducing the residual oil saturation, whereas the sweep efficiency will be significantly improved by the polymer injection as a result of proper mobility control. With regard to the well patterns, water flooding has demonstrated a high productivity in horizontal wells. Recently, other EOR processes have been increasingly applied to the horizontal wells in various well patterns. In this study, the efficiency of SP flooding applied to horizontal wells in various well configurations is investigated in order to select the best EOR performance in terms of either a technical or economical point of view. Furthermore, the reservoir is assumed to be anisotropic with four different layers that have same porosity but different permeability between each layer. The study figures out that, the utilization of a horizontal injector and producer always gives a higher oil production in comparison with the reference case of a conventional vertical injector and producer; however, the best EOR performances that demonstrate the higher oil recovery and lower fluid injected volume than those of the reference case are achieved when the production well is located in bottom layers and parallel with the injection well at a distance. While the location of producer decides oil productivity, the location of injector yet affects the uniformity of fluids propagation in the reservoir. A predefined feasibility factor is also taken into consideration in order to reject the infeasible cases that might give a high oil production but require a higher injected volume than the reference case. This factor is used as an economic parameter to evaluate the success of the EOR performance. The simulation is carried out in a quarter five-spot pattern reservoir with the support of the Computer Modeling Group (CMG) simulator. Understanding the predominant EOR performance of SP flooding in horizontal wells will help to select the best plan to obtain the highest oil recovery when considering economic issues.
Highlights
The utilization of horizontal wells to recover trapped oil in the enhanced oil recovery stage has been developed as the significant well patterns installed in conventional reservoirs.Improvements in horizontal well technologies have been demonstrated to be technically and economically attractive compared to the use of only conventional vertical wells [1]
The efficiency of SP flooding applied to horizontal wells in various well configurations is investigated in order to select the best enhanced oil recovery (EOR) performance in terms of either a technical or economical point of view
The rest of the well combinations are categorized in Category C as the least effective well patterns owing to their low cumulative oil production compared to the performance of the reference case
Summary
The utilization of horizontal wells to recover trapped oil in the enhanced oil recovery stage has been developed as the significant well patterns installed in conventional reservoirs. The numerical studies of Algharaib on water-flooding processes concluded that increases in the lengths of the horizontal wells do not result in a linear increase in the additional oil recovery [5]; a long horizontal well was not necessary for recovering the trapped oil in a heterogeneous reservoir [6]. This work focuses on the utilization of horizontal wells for surfactant-polymer (SP) flooding in a heterogeneous reservoir. The horizontal wells can provide cost effective solution in terms of productivity [11,12], the length of the well and, obviously, the long project life caused by the long horizontal well should be considered, and the injectivity reduction (when injecting polymer) can significantly affect the economics [13]. The heterogeneous reservoir complicates the EOR processes owing to the unstable and unpredictable performance [14,15]
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