Optimization of a Large Polymer Flood Using Full-field Streamline Simulation

Abstract

A field scale polymer flood has been in operation since early 2010 in a major oil field of the Sultanate of Oman. The project comprises 27 patterns where water flood was on-going prior to initiation of Polymer flood in 2010. A polymer flood project has high chemical operating expenditure (Opex). Thus, optimization of a polymer flood requires continuous tracking of mass of polymer injected per unit volume of incremental oil produced for individual polymer flood patterns and then polymer throughput in individual patterns needs to be dynamically altered. To meet this objective, a full-field streamline simulation model has been built, history matched and is being used for optimizing the polymer-flood. Full-field simulation allows the proper modeling of each pattern and their interactions with off-set patterns, and these simulations can be performed in a reasonable computation time because of the efficiency of streamline modeling. Computational efficiency of streamline simulation has facilitated use of the model for routine well and reservoir management decisions. This would not have been possible with a finite difference model because of excessive run time and inability to clearly establish injection-production relationship as in a streamline model. The model has facilitated optimization of polymer flood patterns, specifically when to stop polymer injection, slug size, and slug concentration. Individual pattern performance can be visualized effectively and their efficiency can be compared. The model is also being used for ranking the existing water-flood patterns for the next phase of polymer-flood implementation and carrying out short term production forecast.

Historical and recent observations in polymer floods: An update review

“…As mentioned earlier, productivity losses have not been reported in most polymer floods except for Bohai Bay (27 injectors), Sleepy Hollow Reagan Unit (10 injectors) and Marmul (27 injectors) large/ commercial scale polymer floods (Choudhuri et al, 2014;Christopher et al, 1988;Luo, Zhao & Branch, 2011;Thakuria et al, 2013;Xiaodong et al, 2011). Mangala Field, India (Kumar, P., Raj., R., Koduru, N., Kumar, S., & Pandey, A., 2016) and Patos-Marinza, Albania (Bankers, 2016;Carss, 2014;Jacobs, 2015) are also recent large polymer floods but there is a lack of information documenting polymer production and/ or possible productivity losses.…”

“…Additionally, Choudhuri et al (2014) reported the optimization of the current phase (27 patterns) of the polymer flood based on streamline simulation. The main objective of this study was to evaluate individual patterns under polymer injection identifying underperforming patterns that were converted to water injection (3 patterns), another pattern that improved its efficiency after a conformance job and the rest were ranked to optimize polymer injection by adjusting injection rates, slug size and/or polymer concentration.…”

“…Finally, Haynes, A. K., Clough, M. D., Fletcher, A. J. P., & Weston, S., (2013) reported that the rate at which fracture growth occurred was unknown. Choudhuri et al, 2013;Choudhuri et al, 2014;Koning and Mentzer, 1988;Shuaili et al, 2012;Thakuria et al, 2013;Zwaan and Valdez, 2015). This field was discovered in 1956 and started commercial production in 1980.…”

“…Although some of the injectors were already fractured during the waterflood, polymer injection was planned to be "under controlled fracturing conditions since a matrix development will result in extremely low injectivity". Choudhuri et al, (2014) reported that the fracture length should not exceed 30% of the spacing to minimize the risk of direct inter-well communication impacting negatively the sweep efficiency.…”

“…However, despite numerous successes and encouraging results reported in multiple field experiences , the number of large-scale or commercial floods is still considered relatively low except in Canada (Renouf, 2014) and China (Zhang, Y., Wei, M., Bai, B., Yang, H., & Kang, W., 2016). Examples of other countries reporting large scale (>10 injectors) or commercial polymer floods include Albania (Bankers, 2016), Argentina (Buciak, Sancet & Del Pozo, 2015) and Oman (Choudhuri et al, 2014). Figure 1 shows the general location of pilot and large/ commercial (> 10 injectors) polymer flood projects included in this review.…”