Field Testing a New Spectral Neutron Tool for Identifying Bypassed or Moved Hydrocarbons Behind Casing in Both Vertical and Horizontal Wells in Mature Producing Fields in Northeast Oklahoma

Shambhu N. Tripathi¹, Ph.D., R. V. ÒBobÓ Westermark². (1) Nuclear Physicist, Century Geophysical Corporation, Tulsa, OK, (2) Grand Directions, LLC, Tulsa, OK [email protected]

This paper presents the field-testing results for a Spectral Neutron Tool (SNT) which can identify hydrocarbons behind casing. The field testing conducted includes new wells with modern log suites having the SNT run in both open and cased hole, old wells having no electric logs, and several open-hole logs in horizontal wells. The field testing was done in conjunction with Grand Resources, Inc. of Tulsa, Oklahoma, as part of their ongoing horizontal-drilling program. All logs to date have been run in Pennsylvanian formations, concentrating on mature Bartlesville and Tucker sandstone reservoirs.

The SNT uses a continuous source of neutrons to activate the subsurface formations surrounding the well bore. It measures the spectrum of neutron-induced gamma rays, incorporating state-of-the-art down-hole nuclear technologies. The log provides lithology determination and a neutron porosity index and identifies fluid type occupying the pore space.

Comparisons of the SNT logs in open hole and cased holes will be presented to demonstrate this technologyÕs ability to identify hydrocarbons behind casing. The use of the SNT in clearly locating high oil-saturation compartments of bypassed oil in horizontal wells will also be discussed.