Technology Update: Magnetic Resonance-While-Drilling System Improves Understanding of Complex Reservoirs
- Kirill Kuptsov (Schlumberger) | Roger Griffiths (Schlumberger) | David Maggs (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- December 2015
- Document Type
- Journal Paper
- 26 - 29
- 2015. Copyright is retained by the author. This document is distributed by SPE with the permission of the author. Contact the author for permission to use material from this document.
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Reservoirs consisting of heterogeneous carbonates and shaly sands pose formation evaluation challenges for conventional logging-while-drilling (LWD) measurements. Widely used resistivity, density, neutron porosity, and sonic measurements are all sensitive to both the formation matrix and the fluids, which may create ambiguities in the evaluation of reservoir fluids.
The Schlumberger proVision Plus magnetic resonance-while-drilling (MRWD) technology offers enhanced evaluation capabilities. By manipulating the hydrogen atoms in the fluids, nuclear magnetic resonance (NMR) methods provide a focused measurement of fluid properties and their interactions with the surrounding matrix at a fundamental level. The technology provides a more complete, real-time assessment of producibility in complex reservoirs.
Evolution of the Technology
The industry has used NMR technology for formation evaluation for more than 25 years, during which significant technical and operational developments have greatly enhanced its capabilities and applications. In porous media, NMR techniques reveal pore and fluid properties by exciting the nuclear states of hydrogen-containing molecules in the formation fluids and measuring the relaxation times for the induced excited energy states.
The relaxation time for a molecule near a pore wall surface tends to be much faster than that for a molecule in the bulk fluid volume. A distribution of all the relaxation times, known as a T2 distribution, can be used to derive both irreducible and producible fluid volumes, and an improved estimation of permeability. These measurements are also important for identifying bypassed pay zones and estimating production rates.
The first NMR tools were deployed on wireline after the hole had been drilled, which added rig time and cost to the operation and did not allow for real-time changes to the wellbore’s trajectory. Schlumberger shifted the service from wireline to a while-drilling application in 2002. This early work focused on redesigning the sensor array to make it more robust and capable of withstanding dynamic drilling environments.
The design effort culminated with the introduction of the company’s latest MRWD system in 2012. Its new sensor makes reliable measurements under rapidly changing downhole temperatures and pressures and withstands the vibrations and drillstring shocks that are common during drilling.
Further design enhancements allow the tool to be placed anywhere within the bottomhole assembly (BHA). A sleeve stabilizer minimizes tool motion without affecting the steerability of the BHA. Powered by a downhole electrical turbine, the tool does not need to be tripped to replace batteries.
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