Comprehensive Field-Scale Injection Performance Analysis Associated with Injected Water Quality Parameters

Abstract

This paper presents a comprehensive injection performance analysis conducted in major carbonate fields in Saudi Arabia. The production from the fields under study is pressure-maintained by peripheral water injection. More than 190 case studies were examined to generate populated trends and draw relevant conclusions on parameters affecting injection performances. Petroleum engineering concepts/tools, such as pressure transient analysis, were heavily used in this work to establish the effective yearly injection decline rate for each well.Extensive and dedicated sampling of injected water was carried out as part of water quality monitoring to ensure that well plugging and internal corrosion was minimized. The total dissolved solids, total suspended solids, particle count and size distribution, acidity, iron count, sulfide content, and bacterial growth data were measured and synchronized with the respective wells' injectivity indices to identify potential sources of well injection impairments. Major events, such as when starting or switching the water injection system, were thoroughly factored into the water quality analysis and its subsequent effect on the injection performances.The well injection performance analysis was carried out using pressure-transient analysis data obtained from Fall-Off Test (FOT) surveys, where each well has a baseline II survey taken when the well was first drilled and completed. Dimensionless injectivity indices were defined to compute the injection potential of each well. Baseline surveys were then compared with the subsequent or the latest surveys, if any, based on which time-lapse measurement trends were generated and analyzed.Several key findings and recommendations, regarding setting appropriate limits to water quality parameters and injection surveillance strategy, are presented in light of the performed analysis.This paper also discusses production engineering efforts to mitigate the decline in well injectivity, including: water quality control, well stimulation initiatives to enhance injectivity, and analysis of well plugging characteristics/profiles and their relation to reservoir permeability.