Intelligent Downhole Identification and Control are Key to a Successful Water Conformance Strategy

Abstract

In many parts of the world, the water oil ratio (WOR) is approximately 9:1, resulting in large amounts of undesired fluids that require managing and processing, ultimately increasing cost. Water management strategies are applied to reservoirs to increase oil recovery and provide proper water conformance to minimize these impacts. The success rates of legacy water management strategies are approximately 40% of the causes for the low success rates involved in trying to control the water problem at later stages when treatment effectiveness is less effective and the diagnostics for the source of water production are more difficult. Early reservoir management strategies are needed to effectively reduce unwanted water production.

In this paper, we discuss a unique 4-stage process starting with reservoir analysis. Water coning and channeling are characteristic signatures in log-to-log WOR vs. time plots (Chan. 1995). These plots are used to identify near-wellbore problems and provide guidance into potential reservoir-related water issues. If the water production is from a high permeability streak, water increases rapidly and follows a linear pattern in the WOR vs. time log-log plot. The slope severity is dependent upon the relative permeability profile, initial saturation conditions, reservoir fluid properties, and capillary pressure. In bottom water coning, the plot curve exhibits a slow WOR increase rate until reaching an asymptotic behavior versus time in a log-log plot. After assessing candidate wells for the identification of water production issue, a chemical-based treatment is executed to mitigate the problem, temporarily or permanently.

This work showcases the results of zonal isolation, natural fracture sealing, and relative permeability modifications from wells in South America and Europe. The first candidate located in Colombia suddenly started to experience a high WOR, with the water cut increasing from 20 to 80%, in 45 days. A comprehensive study indicated that the issue was related to coning. The design and treatments helped to achieve a water-cut reduction of 53%. Another case located in Europe involved a well with permeability ranging from 55 to 175 mD. After treatment, the water production was reduced by an average of 50%, with a corresponding increase in the hydrocarbon production rate. The results demonstrated the effectiveness of the early water management strategy in reducing water cut and sealing off the water producing zones. This strategy also eliminates conventional flow measurements by using real-time sensor data to drive engineering models and predictive analytics to evaluate the data. This combination allows for immediate responses to ever-changing conditions for individual or group wells.

This paper presents specific case studies based on a proposed reservoir conformance workflow that utilizes smart technologies to perform real-time WOR analysis and describe the critical steps required for successful water management. If a water conformance issue is detected early and resolved, it will enable the operator to decrease water production, optimize oil production, and reduce overall operating costs.