Waterflood Sweep Improvement at Prudhoe Bay, Alaska

Abstract

Waterflood conformance control due to reservoir heterogeneity is a common challenge to many oilfield developments. This paper describes the application at-scale of a thermally-activated polymer particle system (TAP) for improving waterflood sweep efficiency in the Prudhoe Bay field, Alaska. Since 2004, the technology has been successfully deployed 91 times in Prudhoe Bay Unit on the North Slope of Alaska as part of an approved Enhanced Oil Recovery (EOR) program. A total of 1.6 million gallons of chemical polymer particles have been injected into approximately half of the available waterflood patterns. Once the polymer particles activate deep in the reservoir, they provide resistance to water flow in the thief (swept) zones. The treatment design workflow applies a thermal model which accounts for the impact of the temperature distribution in the reservoir on activation of the polymer particles. Challenges associated with performance evaluation of the treatment program in a normal operational setting (as opposed to field trial) have been addressed, particularly in relation to interferences to interpretation resulting from the ongoing application of miscible gas EOR in the waterflood areas. Of the 44 treatments deployed between 2008 and 2012, 22 were sufficiently mature to have performance data which was not adversely impacted by interferences from well work, changes to operating conditions, or miscible gas breakthrough. So far, only one of the 22 patterns has not indicated an incremental oil response, while in two patterns the response had started too recently to be able to extrapolate the overall response magnitude. The analysis showed overall positive responses from the treatments that are competitive with other well work on cost/bbl and project economics. Results from this study provide insights on key controls on waterflood sweep improvements, and inform future candidate selection and optimization of treatment designs. The production performance analysis was corroborated by wellhead injectivity, repeat pressure fall-off tests, and reservoir modeling. This paper documents a good case history of waterflood sweep improvement.

Waterflooding, water-gas method and generation of carbon dioxide in the reservoir – methods of enhanced oil recovery and technology development

“…Of course, such a wide and successful application of the waterflooding technology is due to its own manufacturability during implementation, as well as the low cost and availability of large volumes of the agent injected into the reservoir -water. Along with high efficiency, non-stationary waterflooding technology creates serious problems in the development and operation of oil fields [1][2][3][4][5][6][7][8][9][10]. The problems are of both natural and technogenic origin, leading to premature breakthrough of injected or IOP Publishing doi:10.1088/1755-1315/1212/1/012038 2 formation water to production wells with subsequent watering of their production, which in turn provokes the formation of stagnant and poorly drained zones.…”

“…This project made it possible to maintain reservoir pressure for a long time, but later the degree of pressure recovery began to decrease. To increase the beneficial effect of waterflooding in this field, the injection of polymer particles was implemented, which made it possible to increase the coverage area of the formation [4].…”

A Tracer Streamline Practice for Re-Evaluation Waterflood Pattern to Introduce a Cyclic Water Injection Scheme

“…The very high permeability can disturb the sweeping effect in the waterflood scheme (Alhuthali et al, 2007). Waterflood conformance control on reservoir heterogeneity is a common challenge in an oil field (Thrasher et al, 2016).…”