Case Histories and Applications of a New Slimhole MWD Multiple-Depth-of-lnvestigation Resistivity Sensor
- Scott Ball (Sperry-Sun Drilling Services) | Stewart Yee (Sperry-Sun Drilling Services) | Chris Maranuk (Sperry-Sun Drilling Services) | Mike Bittar (Sperry-Sun Drilling Services)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- December 1996
- Document Type
- Journal Paper
- 228 - 233
- 1996. Society of Petroleum Engineers
- 2.4.3 Sand/Solids Control, 5.8.5 Oil Sand, Oil Shale, Bitumen, 4.1.2 Separation and Treating, 1.10 Drilling Equipment, 4.1.5 Processing Equipment, 1.6.1 Drilling Operation Management, 2 Well Completion, 1.6.7 Geosteering / Reservoir Navigation, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.6 Drilling Operations, 5.1.2 Faults and Fracture Characterisation, 1.12.1 Measurement While Drilling, 1.4.4 Drill string dynamics, 1.5 Drill Bits, 5.5 Reservoir Simulation, 1.11 Drilling Fluids and Materials, 5.6.1 Open hole/cased hole log analysis
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The use of Measurement-While-Drilling (MWD) resistivity tools in boreholes 8-1/2 inches and greater in diameter has evolved over the past 10 years from a little-used, qualitative service, to a routinely-used quantitative service in directional, horizontal, and extended-reach wells. Todays' applications include reconnaissance logging, geosteering, pore pressure evaluation, wireline replacement, and enhanced formation evaluation.
Over the last several years, there has been an increasing trend worldwide toward drilling smaller boreholes to optimize the costs of tubulars and gain greater drilling efficiencies. Until recently, there have been 100 MWD resistivity tools available for logging 6 inch diameter boreholes. A new multiple-depth of-investigation MWD resistivity sensor housed in a nominal 4-3/4 inch diameter drill collar has been developed for use in slimhole drilling operations.
This new MWD resistivity sensor provides eight different depths of investigation in any mud type and allows for derivation of floe flushed zone resistivity, true resistivity, and the diameter of invasion across a wide range of formation resistivities. The tool is designed for boreholes larger than 5-7/8 inches in diameter and can be used in medium radius drilling applications.
Extensive operations in the North Sea, Gulf of Mexico, South Texas, Middle East, Alaska, and Australia have demonstrated a variety of applications. Slimhole MWD resistivity has been shown to have utility in geosteering horizontal wells to maintain and optimize well bore placement. Additionally it allows determination of true formation resistivity and diameter of invasion for formations with invasion effects and provides for application of advanced modeling techniques to enhance formation evaluation and log interpretation.
The measurement of propagation resistivity in the MWD environment began in 1983 with the introduction of the 2 MHz Electromagnetic Wave Resistivity (EWR ) tool. These devices became the standard in the industry due to their ability to operate in a wide variety of downhole environments coupled with their ability to measure true formation resistivity in preinvaded and shallow invasion conditions as well as their excellent vertical resolution. In many cases, these MWD logs became preferable to wireline induction logs which are typically run many days after drilling.
These conventional EWR-type MWD logs can sometimes be misinterpreted. Invasion in the MWD environment is assumed to be shallow or at such an early stage of progression that the measurement of phase or attenuation resistivity is proposed to be a measurement of true fonnation resistivity. In many cases this is not true. Appreciable mud filtrate invasion can easily occur in the MWD time domain that can affect the conventional EWR measurement of phase and attenuation resistivity.
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