Multi-dimensional NMR Technique for Wireline Formation Tester Sampling Optimization and Perforation Strategy Determination in a Brown Field, India

Abstract

AbstractThe Neelam field is situated in south-east of the giant Mumbai High oilfield in western offshore basin of India. This field was discovered in 1987 and has been put under production since 1990. The field is presently under active water injection and the average oil production from the study area is approximately around 100 BOPD with 95 percent water-cut.Perforation strategy determination in a brownfield carbonate reservoir under extensive water injection is very challenging. Fluid identification is critical in these reservoirs. Wireline formation tester sampling at defined depths can be very useful for downhole fluid identification. However, the sampling is a stationary measurement and depends on successful communication with the formation fluids. Multi-dimensional nuclear magnetic resonance (NMR) data can efficiently optimize the wireline formation tester operations in such critical wells by using continuous porosity and permeability at various depths of investigations. Additionally, resistivity independent fluid typing and saturation results from NMR analysis at different depths of investigation can be used to optimize the perforation strategy.Our study established a workflow for designing an efficient completion plan and perforation strategy by integration of multi-dimensional NMR and formation tester wireline logging technologies in a single acquisition run in the Neelam field. However, the workflow is applicable to similar reservoirs elsewhere in the world. The objective was to enhance oil recovery and reduce water-cut and rig-time. NMR data were used to optimize the formation tester operations by identifying possible tight zones. Moreover, the NMR saturation profiling results provided continuous fluid typing and fluid saturations at different depths of investigations. Formation tester fluid sampling was carried out at discrete station depths in the same run after NMR acquisition; the formation tester station measurements of reservoir mobility and in-situ fluid analysis were then used to validate the continuous NMR log derived fluid characterization and permeability. Based on all this integrated workflow and timely analysis the best possible completion strategy was decided and perforation intervals were optimized. The well is presently producing around 270 BOPD with a 30 percent water-cut.