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Utilization of Magnetic Resonance Bin Distribution to Determine Specific Permeability

Charles H. Smith1, Jim Bray2, and Sandeep Ramakrishna3
1Halliburton Energy Services, Oklahoma City, OK
2Halliburton Energy Services, Denver, CO
3Halliburton Energy Services, Houston, OK

The Granite Wash formation in Oklahoma is an arkosic detrital material resting on older Precambrian rocks. It can range in age from Precambrian to Middle Pennsylvanian. Formed by erosion of uplifted segments, it is generally granitic in nature, it may also include large areas of reworked carbonate. This wash presents a very difficult log interpretation problem since reservoir consistency varies greatly from well to well. Magnetic Resonance Image Logs were added to the logging program toe establish additional parameters that could be used for reservoir description.

The standard Coates permeability equation and variations were applied to estimate permeability with little correlation to production. As the grain size, the cementing material of the rocks and the lithology vary so greatly from well to well, the Coates relationship does not remain constant, and this technique proved to be inconclusive.

An observation was made that T2 bin distribution data tended to mirror production rates. Attempts were made to establish an algorithm that would directly establish permeability for this formation using the measured T2 data.

This case study details this method of using T2 bin information for estimating permeability and includes several Granite Wash wells. The Bin data was correlated to flow rates measured 30 days after fracture treatment. A permeability was then calculated directly from this established flow rate and modeled to the observed NMR bin data. Sufficient data was utilized to establish a generalized algorithm for permeability within this formation.

Subsequent logging and comparison of projected versus actual permeability as established by cores and production data has proven the value and accuracy of this technique. We anticipate that this same iterative technique may be applied with positive effect to many other reservoirs.

AAPG Search and Discovery Article #90092©2009 AAPG Rocky Mountain Section, July 9-11, 2008, Denver, Colorado