Art of Discovery: Importance of Modern Logs and Accurate Mudlogs - an Example of a New Field Discovery

Abstract

Numerous new field discoveries may be missed by explorers who fail to use a full suite of modern logs and correctly calibrated mudlogs. A recent new field discovery in the Red Fork Sandstone and the Viola Limestone provides an excellent example of an ‘easy-to-miss’ field. The initial well was drilled on a 3D seismic structure. The primary objectives were tested as non-commercial. Before plugging, an errant 4-foot section of Red Fork Sandstone was perforated. The well flowed at a rate of 50 BOPD from natural perforations. Subsequently, the second well encountered a section of the Viola Limestone that was very similar to that in the first well (questionable porosity). However, the microlog suggested permeability in the middle Viola section and the mudlog indicated hydrocarbon presence. The mudlog shows and porosity intervals were identical to those not tested in the first well; the first well did not have a microlog. Consequently, the Viola interval was perforated in the second well and began flowing 200 BOPD with no treatment. The Viola flowed more than 15,000 BO in the first 100 days and produced no water. Presently, the field contains three wells producing from the Red Fork Sandstone and one well produces from the Viola Limestone all as a result of close examination of the logs and accurate mudlogs. Existing old style logs in the area would not have predicted the discovery in the Red Fork nor did the old style logs suggest a permeability zone in the Viola.

AAPG Datapages/Search and Discovery Article #90221 © 2015 Mid-Continent Section, Tulsa, Oklahoma, October 4-6, 2015