Leveraging Single Phase Characteristics of Water Injectors to Optimize Reservoir Pressure Surveillance

Abstract

This paper presents a comprehensive field-scale engineering look into the application of single phase average gradient equation to obtain pressure surveys in water injectors. This methodology is sought to optimize well intervention operations in water wells while achieving all strategic master surveillance objectives. Strategic reservoir pressure surveillance necessitates surveying water wells in a given field. Several key water injectors are surveyed with increased frequency and are drilled in spatially selective locations. The objective of such surveys is to generate representative reservoir isobaric maps in order to guide field development activities and reservoir production/injection management. The current practice to obtain reservoir pressure data from water wells is through wireline intervention. An extrapolation method of Shut-In Wellhead Pressure (SIWHP) using an average water gradient to calculate Static Bottom Hole Pressure (SBHP) was rigorously examined and proofed accurate in the field. Raw data from more than a hundred strategically placed water wells were analysed and contrasted against measured data obtained from downhole pressure gauges to validate the proposed methodology. Sensitivity and error distribution analysis of existing data was performed to quantify the effect of different reservoir characteristics and injected fluid quality. Key findings and recommendations were generated in light of the above analyses with regards to the proper selection of candidates to apply this methodology. The application of this innovative approach has generated a significant cost saving and reduction of man-hours. As for well intervention, the number of wireline operations to obtain SBHP for key water wells was reduced by 75%.