The Economics of Wettability Alteration for Renewed Production from Old Fields in the Permian Basin: Evaluations of Spraberry, Avalon and Bone Springs Reservoirs
Geoffrey Thyne¹, Sharon Yacob¹, and Teresa Nealon¹
Changing reservoir wettability by changing injected water chemistry has been the subject of intensive research for the last fifteen years. The promise of taking old fields and recovering additional oil during normal waterflood operations is always attractive. However, while many hypotheses have been advanced to account for the observations, the lack of confidence in predicting response has limited application of this technique. This paper presents a review of field and lab performance focused on establishing reasonable empirical bounds for the factors leading to increased production. Using this basis we developed a quantitative screening tool to identify fields with high probabilities for favorable outcomes. Representative screened fields were used to perform economic evaluations to assess potential profitability.
We screened a range of sandstone and carbonate fields in the Spraberry, Avalon and Bone Springs using public-domain data. More than 60% of fields passed the criteria. Those fields were then evaluated to determine the potential costs and benefits using an analog model based on the Kinder Morgan CO2 economic scoping tool with suitable modifications. We can account for taxes, royalties, etc, and assume a worst-case operational cost model, that all the produced water is treated before re-injection. We did not include peripheral benefits such as lower maintenance costs, reduced scaling and souring and improvement in injectivity making the calculations even more conservative in nature.
Assuming incremental recoveries similar to known field cases (5 to 15% OOIP, the relatively low CAPEX and OPEX compared to other surfactant flooding mean that many fields will be profitable. We varied water treatment costs, oil prices and recovery factors to evaluate the likely economic return only smaller fields are marginal. The major sensitivities are the amount of remaining oil and the rate of water injection. In cases where water treatment is required, costs are modest assuming reverse osmosis technology. Other cases where target injection chemistry can be achieved by blending produced water with other resources are even more profitable. While some assumptions used in this evaluation may need to be refined as we become more knowledgeable, the basic idea, that waterflooding to alter reservoir wettability will be profitable seems well justified from technical and economic perspectives.
AAPG Datapages/Search and Discovery Article #90190©AAPG Southwest Section Annual Convention, Midland, Texas, May 11-14, 2014