Integrated Formation Evaluation Applications in Tarmat Identification, Well Placement, and ICD Completions Design Using Source-Less NMR Technology – A Case Study from a Middle East Jurassic Reservoir

Abstract

This paper presents the successful integration of an advanced nuclear magnetic resonance (NMR) log, a source-less technology, with core data and other openhole logs to resolve the challenges of reservoir characterization (including identification of tar mat) and to place the wells in targeted reservoirs zones. This enabled subsequent inflow control devices (ICD) completion design for optimal production in these complex carbonate Jurassic reservoirs. A comprehensive suite of advanced logs, conventional logs and core data were used. The wireline suite covered conventional (resistivity-density-neutron-gamma ray-acoustic) and advanced (NMR-elemental spectroscopy-image) technologies in one of the pilot wells. In another calibration well, data gathering was achieved with wireline (resistivity-density-neutron-gamma ray) and LWD NMR to log the same reservoirs. Integration using these conventional logs, advanced logs and core data established the correlations to derive permeability in this complex carbonate Jurassic reservoirs. From these study wells, a correlation was established between the NMR porosity, density/neutron porosity and core porosity to enhance confidence on NMR-measured porosity. The NMR permeability index was calibrated using parameters that were developed by integrating NMR results with the core data. This permeability relationship (core and NMR) was applied in all lateral wells with LWD NMR results that targeted the same reservoirs in the field. For delineating the tar mat interval, a combination of NMR, density and resistivity measurements was used. The LWD NMR results provided real-time reservoir characterization with rock quality (porosity distribution, permeability) that helped in ICD completion design and enhanced well placement. This approach and technology also enabled substantial rig time savings and reduced HSE risks. This approach demonstrates strong benefits of data integration and proven LWD NMR source-less and lithology-independent technology, in addition to the resistivity and gamma ray, as the preferred solution for advanced reservoir characterization, ICD completion design, and enhanced well placement in complex carbonate reservoirs. The solution for reservoir characterization enabled confident decisions on ICD completion design and enhanced well placement by implementation of source-less technology, eliminating the risks of using radioactive source-based technology.