Evaluation of Polymer Alternating Waterflooding in Multilayered Heterogeneous Waterflooded Reservoir

Warut Tuncharoen,Falan Srisuriyachai,N Moubayed

doi:10.1051/matecconf/201817104001

Abstract

Polymer flooding is widely implemented to improve oil recovery since polymer can increase sweep efficiency and smoothen heterogeneous reservoir profile. However, polymer solution is somewhat difficult to be injected due to high viscosity and thus, water slug is recommended to be injected before and during polymer injection in order to increase an ease of injecting this viscous fluid into the wellbore. In this study, numerical simulation is performed to determine the most appropriate operating parameters to maximize oil recovery. The results show that pre-flushed water should be injected until water breakthrough while alternating water slug size should be as low as 5% of polymer slug size. Concentration for each polymer slugs should be kept constant and recommended number of alternative cycles is 2. Combining these operating parameters altogether contributes to oil recovery of 53.69% whereas single-slug polymer flooding provides only 53.04% which is equivalent to 8,000 STB of oil gain.

Highlights

In recent years, oil price has plunged below satisfaction for the oil producers which triggered them to save any cost as much as possible especially, the cost of exploring and drilling new wells so, various oil recovery techniques are developed to extend the oil production life
At the early time before breakthrough, pressure support from waterflooding can maintain oil rate at 800 STB/D later, after water breakthrough, oil rate drops rapidly due to insufficient pressure support from waterflooding, oil production is terminated in mid-2005 due to watercut constraint with cumulative oil production of 0.49 MMstb and oil recovery factor of 38.8%
This can be explained that for the first two descending order cases, first polymer concentration is too high for preflushed water to recover the polymer injectivity while second polymer slug has less concentration that can be injected but with lower polymer effect so these greatly reduces the oil recovery afterwards

Summary

Introduction

Oil price has plunged below satisfaction for the oil producers which triggered them to save any cost as much as possible especially, the cost of exploring and drilling new wells so, various oil recovery techniques are developed to extend the oil production life. Waterflooding used to be a common technique to increase the amount of oil owing to its simplicity and cost-effectiveness. When polymer solution is injected into the reservoir, polymer solution with higher viscous force will sweep more oil to the production well comparing to conventional waterflooding. Another benefit of polymer solution is that certain types of polymer tend to be adsorbed onto rock surface which results in reduction of the flow area of water, causing relative permeability to water to reduce and sweep efficiency is increased and more oil is produced

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Conclusion