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.
Only recently, an integrated approach to water diagnostic analysis was shared based on a mature field application; the insight from which has been very useful in the Monro field (one of SPDC fields in the Niger Delta region) and handy for a successful low-cost oil generation and wells, reservoir & facilities management (WRFM) opportunity identification. The Monro field performance was reviewed and initial assessment showed 9 out of 13 conduits were closed-in (representing ca. 65%) due to high basic sediment & water (HBSW) in most cases. Hence, wells & reservoir review (WRR) for the four producing reservoirs in the field was carried out using the integrated approach to water diagnostic analysis in order to ascertain the mechanism of water production in the wells and propose fit-for-purpose solutions to unlock their potentials. The scope begins with the reservoir stratigraphic cross-section showing flow zones and/or facies distribution based on log motifs or cores (if available). The initial petrophysical properties (e.g. Swi, k, etc.) are then mapped on the stratigraphic section against each flow zone and their respective relative permeability functions generated accordingly to determine the propensity for water production in the delineated flow units. Water oil ratio (WOR) and its first order derivative (WOR') plots are generated from over 20 years of wells historical production data (including bean sequencing & well re-entry) and interpreted based on the subsurface understanding of the reservoir. The interpretation was then spot-checked using available reservoir production monitoring (RPM) log result. Following the subsurface understanding from the integrated interpretation of the water diagnostic plots, a total of ca. 2200 bopd was realised as low-cost oil generation from 2 wells and a total potential of ca. 4200 bopd (risked at 50% watercut) from water shut-off opportunities from 3 wells; reducing the closed-in well count to 4 – representing over 30% improvement. This paper presents the practical gains of integrated water diagnostic analysis using Chan type plot. The outcome shows among others that (a) multidisciplinary integration and alignment delivers significant value in opportunity identification and (b) Excellent cross-functional collaboration results in a quick delivery of the identified opportunities.
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