Inflow performance methods for evaluating downhole water sink completions vs. conventional wells in oil reservoirs with water production problems

Document Type

Conference Proceeding

Publication Date

1-1-2018

Abstract

A new method and software have been developed to identify promising reservoir candidates for production improvement using DWS technology. DWS employs dual completion in wells affected by excessive water problem. The bottom completion drains the water and keeps the top completion open to oil inflow. The system has proven to be effective by increasing oil rate, particularly when the drained water - not contaminated with oil - can be disposed off without further processing. Decision on using DWS must be based upon pre-evaluation of reservoir candidates through a theoretical comparison of DWS and conventional well performances. Analytical modeling, to date, would predict oil productivity performance but has fallen short of precision in forecasting conditions for clean (oil-free) water drainage, because it cannot model distributed water saturation around well. New algorithms and an interface to a commercial reservoir simulator have been written and used as a numerical tool for DWS well performance analysis and design. The tool captures hydrodynamic interaction between the two completions of the well in terms of pressure interference, water saturation (coning), and producing water cut for any combination of top and bottom production rates in presence of heterogeneities, capillary forces, and relative permeabilities. It is used to determine a cluster of inflow performance relationships (IPR) for a DWS well to be compared with a single IPR for the conventional well. It is shown that optimized inflow conditions for maximum oil rate provide an unbiased criterion for comparing performance of DWS with conventional wells using a ratio of productivity improvement (PIR). The numerical tool has been also used to study sensitivity of PIR to several parameters of reservoirs with bottom drive: mobility ratio, vertical-to-horizontal permeability ratio, oil-to-water zone thickness ratio, drainage radius, capillary pressure, and limiting pressure drawdown. Two of these six parameters mostly determine superiority of DWS over conventional wells: oil-to-water zone thickness ratio and limiting pressure drawdown. Three parameters are insignificant and could be eliminated from the correlation. The results are combined in a regression formula to be used for ranking DWS reservoir candidates. An example is demonstrated using data from an oilfield with severe water problem.

Publication Source (Journal or Book title)

Canadian International Petroleum Conference 2003, CIPC 2003

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