Analytics-Driven Method for Injectivity Analysis in Tight and Heterogeneous Waterflooded Reservoir

Abstract

Waterflood is one of the most reliable methods to enhance oil recovery. Among many factors governing waterflood performance, injectors’ injectivity is considered as the key factor. Throughout the life of a waterflooded reservoir, injectivity impairment occurs which can have a negative impact on pressure maintenance and sweep efficiency provided by the waterflood, which both have a direct impact on production. This study aims to establish an integrated, analytics-driven method that will be leveraged to analyze injectors’ performance in a tight and heterogeneous reservoir and monitor the evolution of their injectivity over time. An injectivity diagnostic methodology was developed by incorporating daily injection data and integrating various analytical techniques including instantaneous injectivity index, Hearn plot, Hall plot, derivative Hall plot, and falloff test and analysis. The resulting analytics performed well in assessing the performance of all injectors in the studied reservoir and identifying which injectors were experiencing formation damage and need stimulation. Instantaneous injectivity index quantifies the injectivity of each well. Hearn plot presents the change of the reciprocal injectivity index throughout the injection period. Hall plot provides qualitative indicators of formation damage and stimulation in each injector. Derivative Hall plot was able to capture subtle changes in injectivity that cannot be detected by conventional Hall plot, making it a powerful tool for realtime injectivity monitoring. Falloff analysis provides well and reservoir characterization in a particular injector, proving the low permeability and fractured characteristics in the injector. Each technique has its advantages and limitations and the best practice was implemented by combining all the techniques to obtain a clearer and bigger picture of the performance of all injectors. This paper describes the integrated data analysis for injectivity analysis in a tight and heterogeneous reservoir. The workflow presented is practically applicable and highly recommended for monitoring and evaluating injectors’ performance in any reservoir, including the most complex ones.