Application of a Modern Electrical Borehole Imager and a New Image Interpretation Technique to Evaluate the Porosity and Permeability in Carbonate Reservoirs: A Case History from the Permian Basin, United States
Vivek D. Chitale, Clive Johnson, David Entzminger, Lyn Canter, 2010. "Application of a Modern Electrical Borehole Imager and a New Image Interpretation Technique to Evaluate the Porosity and Permeability in Carbonate Reservoirs: A Case History from the Permian Basin, United States", Dipmeter and Borehole Image Log Technology, M. Pöppelreiter, C. García-Carballido, M. Kraaijveld
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This chapter presents the results of field testing a modern generation wireline electrical borehole imager together with a new borehole image interpretation technique applied in a development well drilled in the Permian Basin, Texas. The borehole imager is designed so as to acquire superior quality images even under conditions of a very high ratio of formation resistivity to mud resistivity (Rt:Rm) ratio, which enhances the quality of formation evaluation of carbonate reservoirs particularly. A new borehole image interpretation technique was developed specifically to evaluate the porosity and permeability of carbonate reservoirs by integrating high-resolution data from an electrical borehole image log with the conventional wireline logs.
As shown in the chapter, the X-tended Range Micro Imager (XRMI™, manufactured by Halliburton) with improved signal-to-noise ratio and expanded dynamic range was able to yield a high-resolution microconductivity signal. This helped generate very high-resolution borehole images showing millimeter-size features in the fabric of carbonate beds. The microconductivity signal was then analyzed with the help of a newly developed software technique that first equates the total signal with total porosity, which is then resolved into fractions correlatable with micro-, primary, and secondary porosity. The new technique of image interpretation treats permeability based on published petrophysical models of equating rock types in carbonates with porosity types.
Integrated analysis of XRMI and other logs from a Whiting Oil and Gas Corporation well drilled in the Wolfcampian carbonate reservoir in the Permian Basin of the United States shows that facies and layer boundaries, the internal fabric of the carbonates, and the estimates of different porosity fractions and permeability determined using the new imager and the new interpretation technique closely follow the core descriptions and laboratory analysis of porosity and permeability. These results are encouraging because the single well correlation(s) will be applicable in the future to newly drilled wells in similar geological facies in locations without core control.
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Borehole imaging is among the fastest and most accurate methods for collecting high resolution subsurface data. Recent breakthroughs in acquisition, tool design, and modeling software provide real-time subsurface images of incredible detail, from the drill bit straight to a workstation. Associated interpretation workflows offer the high level of detail that is needed to make operational decision and to increase the predictability of subsurface models. Many exploration and production companies have acquired a wealth of dipmeter and image log data. The data are readily available and provide, for example the orientation of fractures and fluvial channels in space. Further applications of borehole imaging technology include matrix and fracture characterization, pore-type partitioning, geosteering, and in-situ stress determination. Exciting new applications are found in enhanced oil recovery, carbon dioxide sequestration, and geothermal projects. In addition, borehole image data are paramount to unlocking unconventional plays such as shale gas and coal-bed methane. AAPG Memoir 92 portrays key applications of dipmeter and image log data across the exploration and production life cycle. (Continued)