Polymer-Flood Field Pilot Enhances Recovery of Heavy Oils on Alaska’s North Slope

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 195257, “First-Ever Polymer-Flood Field Pilot: A Game-Changer To Enhance the Recovery of Heavy Oils on Alaska’s North Slope,” by Abhijit Dandekar, SPE, University of Alaska Fairbanks; Baojun Bai, Missouri University of Science and Technology; and John Barnes, SPE, Hilcorp Alaska, et al., prepared for the 2019 SPE Western Regional Meeting, San Jose, California, 23–26 April. The paper has not been peer reviewed. Although polymer flooding has become a promising enhanced oil recovery (EOR) technique, no field tests have been performed to date in Alaska’s underdeveloped heavy-oil reservoirs. The overall objective of the research outlined in the complete paper is to perform a field experiment to validate the use of polymer flooding in this challenging environment. At the time of writing, no unexpected injectivity issues or polymer breakthroughs have been encountered and the two horizontal producers are showing positive response to the polymer injection, resulting in incremental increase in oil production rate. Introduction The Alaska North Slope (ANS) contains vast resources of heavy oils, primarily concentrated in the West Sak (also called Schrader Bluff) and Ugnu reservoirs. There are currently six fields producing heavy oil in Alaska: Orion, Polaris, Milne Point, Tabasco, Kuparuk, and Nikaitchuq. Tabasco is a Kuparuk River Unit (KRU) satellite, and the Ugnu formation overlies the West Sak/Schrader Bluff formation across the North Slope fields. The estimated total oil in place within these reservoirs is approximately 20 billion–25 billion bbl, with approximately two-thirds of the heavy oil lying under the KRU. At present, oils from the West Sak/Schrader Bluff formation are being developed. Despite the fact that heavy oil represents approximately a third of known ANS original oil in place (OOIP), the development pace has been slow, with cumulative production contributing only 1% of the OOIP slopewide. High development costs, significant logistical and environmental challenges, and low oil recovery resulting from conventional techniques have been the major factors for underdevelopment of these vast resources. Thermal recovery methods, such as steam injection, are impractical on the ANS because of the high cost and, more importantly, the concerns associated with thawing the nearly 2,000 ft of permafrost, which could cause massive environmental damage. From a technology standpoint, preliminary laboratory and simulation studies have indicated that polymer flooding has great potential to enhance oil recovery from the Schrader Bluff reservoirs, but these have yet to be tested because of the lack of field tests. In fact, no large-scale polymer flood of heavy-oil or other unconventional resources has occurred to date in the United States, although it has been tested and implemented in other countries such as Canada and China. Initial scoping studies suggest that successful implementation of polymer flooding could increase heavy oil recovery by 50% on the ANS. Description of the Polymer Field Pilot Area and Test Wells The project area, the Milne Point Unit (MPU), is between the Prudhoe Bay Unit (PBU) and the KRU. The MPU is approximately 30 miles northwest of the PBU and 15 miles northeast of the KRU. The current working interest owners of the MPU are the operator, 5Hilcorp Alaska (50%), and BP Alaska (50%).