Pipe Conveyed NMR Logging Secures Successful Reservoir Characterization in a Low Resistivity Pay

Abstract

The Middle Burgan formation in North Kuwait is very challenging: its limited vertical thickness and overall low resistivity require complex and special operations for drilling, formation evaluation and completion to ensure optimum production. The objective of this case study is to demonstrate the value of Nuclear Magnetic Resonance (NMR) log data to provide rock quality and fluid typing in this challenging environment, where conventional logs are not enough for reservoir understanding along a horizontal well. A horizontal 6 1/8" section was drilled through the Middle Burgan formation with oil-based mud and Gamma Ray, Resistivity, Density data were acquired while drilling, and data from the latest generation of multifrequency, focused NMR wireline tool (FMR), conveyed on pipe (PCL). Water saturation computation in low resistivity pay often exceeds the real value when computed using conventional logs. In this environment, NMR logging proved to be essential for the proper reservoir characterization and to support critical decisions on well completion design. Fundamental rock quality and permeability profiles were supplied by NMR. Oil saturation was identified by applying the 2D-NMR methods, Diffusion vs. T2, or DT2 maps. Despite the presence of washouts, high quality NMR data was obtained at different depths of investigation in the horizontal well section. Integrating the NMR data with conventional well logs helped advanced reservoir characterization, in reducing the uncertainty in formation evaluation by clearly identifying pay and shale zones, and furthermore, in providing necessary information to support management decisions regarding fracking design to maximize oil production. The formation evaluation and well objectives were met with the aid of the high-quality NMR log data. The multifrequency capability of the tool allows data acquisition at different depths of investigation which helped to overcome the negative effects of washouts in the data interpretation. A remarkable well performance and high productivity from the low resistivity, thin reservoir layers, is expected based on decisions made from the by very reliable well log data interpretation.