Expanding the Limit of Economical Formation Evaluation in a Mature Gulf of Mexico Field Using Formation Evaluation While Drilling (FEWD) Technology
Authors: Kittridge M.G. , Robbins M.B. , Beique J.M. 
Published: December 2007

Abstract
In the past, traditional formation evaluation and hydrocarbon reserve appraisal have relied on petrophysical measurements made with wireline-conveyed logging tools. With the development and demonstration of the technical viability of drill collar-based resistivity and nuclear porosity sensors, formation-evaluation-while-drilling (FEWD) now offers an alternative to wireline-based evaluation. A formation evaluation strategy utilizing FEWD technology can offer economic and technical advantages over traditional wireline formation evaluation. In this paper, we explore the potential to replace wireline petrophysical data with FEWD data in a high rate of penetration (ROP), synthetic oil-based drilling fluid environment in a mature Gulf of Mexico field.
Based on this work we find that FEWD offers an economically attractive and technically viable alternative to wireline tool-based formation evaluation. For the example considered, FEWD cost savings were estimated to be 16% versus wireline, and increased with the probability of pipe-conveyed wireline logging. The FEWD data compares well with comparable measurements made with wireline tools. In addition to the cost savings, FEWD data may yield a more robust interpretation than wireline-based measurements, because of temporal and spatial changes in the wellbore environment. We believe the results described here are applicable to drilling in other mature Gulf of Mexico fields.

Introduction
The domestic E&P industry has seen dramatic change in the past few years brought on by re-engineering efforts directed at improving bottom-line financial performance. Tremendous energy has been devoted to introspective reviews seeking improved margins and reduced cycle times in all phases of the upstream E&P sector. The drilling and appraising portions of reserve replacement are areas where both margins and cycle times can be positively impacted by lower cost, shorter duration well operations. Drilling costs have been lowered by successful application of synthetic drilling fluids, resulting in dramatically increased rates of penetration. Cost-effective reserve appraisal must be accomplished using a formation evaluation strategy adapted to this new drilling environment.
Historically, hydrocarbon reserve appraisal has relied on petrophysical results obtained from evaluation models applied to indirect measurements of formation properties made by wireline-conveyed logging tools. With the development and demonstration of the technical viability of drill collar-based resistivity and nuclear porosity sensors, formation-evaluation-while-drilling(FEWD) now offers an alternative to wireline-based formation evaluation. FEWD may offer critical acquisition advantage(s) over wireline in high angle holes and/or high fluid loss environments. Additionally, FEWD may provide substantial economic benefits over wireline in high rate of penetration (ROP) drilling situations.
Previous work has clearly demonstrated the range of successful application for FEWD data. FEWD resistivity logs can replace wireline induction measurements and may provide additional insight into the invasion process. Successful hydrocarbon typing has been reported using FEWD resistivity and neutron logs. Complete wireline replacement with FEWD resistivity, neutron and density logs has been reported in a number of drilling environments world-wide.
In this paper, we explore the potential to replace wireline petrophysical data with FEWD data in a high ROP, synthetic drilling fluid environment in a mature Gulf of Mexico field.
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