An Integrated Approach to Water Diagnostic Analysis in A Mature Field: SPDC Case Study

Abstract

One of the most popular drive mechanisms in hydrocarbon production is water drive. Depending on the subsurface structural orientation, rock and fluid properties anisotropic distribution and the placement of the well amongst others, it could be edge or bottom water drive. These various patterns of water drive mechanisms have varying degrees of impact on the fluid-water contact, hydrocarbon production and ultimately life cycle recoverable volumes. Whether edge or bottom water, the excessive water production mechanism in a typical well are interrelated; insight to which had been provided by Chan, K.S (1995) in his water diagnostic plot. Though the water-oil ratio (WOR) diagnostic plot has been applied widely in zonal isolation, water shut-off, gas shut-off, gel treatment and its modifications into reserves quantification2, 3, 6, there has not been an integrated approach to the excessive water production analysis; guiding our interpretation of the WOR and its time derivative (WOR’) curves with an integrated understanding of the geological, petrophysical and reservoir properties variation. The WOR and WOR’ plots for this study were generated using over 20 years of production data from one of our SPDC fields in the Niger Delta with 11 oil wells and spanning 4 oil reservoirs. The reservoirs were modelled stratigraphically to show different flow zones delineated by different facies. The initial water saturation and permeability contrast were mapped against each flow zone including their relative permeability functions. The interpretation was also spot-checked using reservoir production monitoring (RPM) log result. This paper presents the outcome of an integrated approach to water diagnostic analysis based on the obtained data set with the view to further crystalize the understanding of water production mechanism in the field, proposing fit-for-purpose wells, reservoir & facilities management (WRFM) actions and adding value to global wells and reservoir performance reviews.