Polymer Distribution Concepts for Large Scale Polymer Floods in the Sultanate of Oman: Simplicity or Flexibility?

Abstract

Abstract Enhanced Oil Recovery (EOR) is firmly established in the hydrocarbon maturation plans of PDO and Shell. Particularly polymer flooding is a proven and established method for hydrocarbon recovery. An important step in maturing polymer flood implementation is the upscaling from a successful pilot to field scale. One of the elements in the upscaling process is the distribution of polymer solution to the different polymer injectors. A fundamental choice is whether flexibility in operations is required to optimize the Well Reservoir and Facilities Management (WRFM) of a polymer flood or the simplest surface concept should be selected. This paper describes the rationale for making a choice for a distribution concept. The current experience in polymer flooding shows that the value of having WRFM capabilities is substantial. In this paper we evaluate the value of WRFM regarding polymer injection. Choices such as the need for varying polymer concentrations per injector and changing the duration of a polymer injection scheme are evaluated. The impact of the regrets for not having the ability to manage the polymer injection are quantified and the probability on the necessity of these aspects of WRFM in a large-scale field is determined based on the experience in an ongoing polymer flood in the South of Sultanate of Oman. Examples are shared that underpin the variance in response form pattern to pattern. Besides the value of WRFM capability, a large number of different concepts for polymer distribution are evaluated based on value, costs and feasibility of implementation and operation. Yard tests were performed to quantify the effect of mechanical shear degradation of low and high concentration polymer to underpin eventual value loss of the polymer. The value of having WRFM capabilities in a polymer flood is clearly articulated and confirmed from the analysis of polymer field data. Large pattern by pattern variations in polymer injectivity and polymer upsides will lead to the decision that the flexibility to turn of polymer injection and reverting to water injection in some injectors is a necessity. A new concept that combines flexibility and simplicity with limited number of moving parts has proven to be feasible and cost effective. The feasibility of the concept is articulated by the positive results of yard tests that show that high concentrations polymer solutions have limited shear degradation. Upscaling from pilot to field scale EOR flood is complex. The structured and integrated approach using both surface and subsurface capabilities combined with actual field performance data and supporting experimental data is novel. The limited amount of shear degradation of a mother solution opens a large number of additional concepts that combine simplicity and flexibility. The concept is not only applicable for onshore fields but also enables implementation of polymer flood in an offshore subsea environment.