Cyclic-Production-Scheme Performance Evaluated Using Reservoir Simulation

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 164168, ’Appraising the Performance of a Cyclic-Production Scheme Through Reservoir Simulation: A Case Study,’ by Tariq Al-Zahrani, Saudi Aramco, prepared for the 2013 SPE Middle East Oil and Gas Show and Conference, Manama, Bahrain, 10-13 March. The paper has not been peer reviewed. Many strategies have been implemented to mitigate the problem of high water-production rates seen in mature fields. One of these is the cyclic-production scheme (CPS). This strategy, which requires alternately shutting and flowing wells with high water cut over a predetermined time, enhances sweep efficiency and pressure maintenance and reduces water-handling costs. In a reservoir-simulation model of a mature oil field evaluating a total of 93 wells, simulation runs involving several scenarios showed significant advantage in applying a CPS. Introduction Water management has become a key strategy in fields that have entered a high-water-cut development period. As fields mature, there is a natural tendency for water volumes to increase as aquifer and injected water advances toward the producers. Furthermore, increasing levels of water production can impair oil-production rates, in some cases to the point at which the well ceases to be economical to produce. Although injected water is an enabler for improved hydrocarbon recovery, it is essential to control water-production volumes and the flood front. High water production may limit oil production in a rate-limited well, increasing water-treatment and -disposal costs. One option to reduce water production from high-water-cut wells is to convert to cyclic production. Cyclic wells are alternated between shut-in and producing phases that normally last for 6 months each. The result of closing in these wells is significant water reduction with minimal impact on oilfield production. The main benefit of the cyclic strategy is the reduction of water production, which allows optimization of the water-injection process, minimizing recirculation and allowing a better displacement of the waterflood front to the updip offset producers. Because less injected water is recirculated, the operational handling costs decrease and the economic efficiency of the water-injection project improves. This study was implemented in a mature field as a part of water-management efforts to reduce water production. In this study, a reservoir-simulation model was developed on the basis of very fine geological characterization, and the field-performance history was matched. The model’s history matching was constantly updated by use of up-to-date reservoir-surveillance, pressure, water-saturation (for flood-front detection), and new-infill-well data. The predictive capability of the reservoir-simulation model is very good. Simulation runs were conducted to analyze and optimize the impact of a CPS on the production performance of the field.