Nuclear Magnetic Resonance

Nuclear Magnetic Resonance - Nuclear Magnetic Resonance...

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19 Autumn 1995 Although well logging has made major advances over the last 70 years, several important reservoir proper- ties are still not measured in a continuous log. Among these are producibility, irreducible water saturation and residual oil saturation. Nuclear magnetic resonance (NMR) logging has long promised to measure these, yet it is only recently that technological developments backed up by sound research into the physics behind the measurements show signs of fulfilling that promise. Nuclear Magnetic Resonance Imaging— Technology for the 21st Century Bill Kenyon Robert Kleinberg Christian Straley Ridgefield, Connecticut, USA Greg Gubelin Chris Morriss Sugar Land, Texas, USA For help in preparation of this article, thanks to Austin Testing, Sugar Land, Texas, USA. In this article, CMR (Combinable Magnetic Resonance tool), ELAN (Elemental Log Analysis), Litho-Density (pho- toelectric density log) and NML (Nuclear Magnetism Log- ging tool) are marks of Schlumberger. MRIL (Magnetic Resonance Imager Log) is a mark of NUMAR Corporation. For nearly 70 years, the oil industry has relied on logging tools to reveal the proper- ties of the subsurface. The arsenal of wire- line measurements has grown to allow unprecedented understanding of hydrocar- bon reservoirs, but problems persist: a con- tinuous log of permeability remains elusive, pay zones are bypassed and oil is left in the ground. A reliable nuclear magnetic reso- nance (NMR) measurement may change all that. This article reviews the physics and interpretation of NMR techniques, and examines field examples where NMR log- ging has been successful. Some Basics Nuclear magnetic resonance refers to a physical principle—response of nuclei to a magnetic field. Many nuclei have a mag- netic moment—they behave like spinning bar magnets ( next page, left ). These spin- ning magnetic nuclei can interact with externally applied magnetic fields, produc- ing measurable signals.
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1. Murphy DP: “NMR Logging and Core Analysis— Simplified,” World Oil 216, no. 4 (April 1995): 65-70. 2. For examples of laboratory T 2 core measurements enabling direct comparison to log measurements and to laboratory T 1 core measurements: Straley C, Rossini D, Vinegar H, Tutunjian P and Mor- riss C: “Core Analysis by Low Field NMR,” Proceed- ings of the 1994 International Symposium of the Soci- ety of Core Analysts , Stavanger, Norway, September 12-14, 1994, paper SCA-9404. Kleinberg RL, Straley C, Kenyon WE, Akkurt R and Farooqui SA: “Nuclear Magnetic Resonance of Rocks: T 1 versus T 2 ,” paper SPE 26470, presented at the 68th SPE Annual Technical Conference and Exhibition, Houston, Texas, USA, October 3-6, 1993. decay of the NMR signal during each mea-
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Nuclear Magnetic Resonance - Nuclear Magnetic Resonance...

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