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Integrated Underbalanced Directional Drilling System
Project Number

To improve the performance and economics of underbalanced directional drilling so that wider commercial application can occur.

Objective: This project will develop an integrated underbalanced directional drilling system based on new and available hardware. The major components of this system include the underbalanced motor, an electromagnetic measurement-while-drilling (EM-MWD) downhole system including the pressure-while-drilling (PWD) sensors and optionally with mid-string repeater, and the surface computing system. The key challeng is integrating the EM-MWD and steerable air motor systems to provide reliable, cost effective directional drilling performance.


Sperry-Sun Drilling Services

Schematic of Underbalanced Directional Drilling System

Accomplishments (most recent listed first)

The prototype EM-MWD tools were fabricated and laboratory tested. These tests also identified design issues and provided invaluable insight to drive the full featured tool development. Five field tests were conducted between June 1996 and January 1997. Three of these tests were designed to demonstrate the telemetry capability of the EM-MWD and two tests addressed drillstring dynamics and downhole vibration. Sperry-Sun has also developed a database of performance information for inclusion into field operating manuals for several complete field kits (systems) for commercial use in its midcontinent area.

Current Status

and Remaining Tasks: The field kits developed in this completed project represents the beginning of commercialization/implementation of this EM-MWD technology. The technology is an "enabling" technology, which allows industry to utilize underbalanced drilling technology in a wider range of directional and horizontal drilling environments. This is important because today's gas reservoirs in the U.S. are increasingly characterized by lower permeability and environments more sensitive to drilling damage.

Project Start
Project End
DOE Contribution


Performer Contribution


Contact Information

Sperry-Sun Drilling Services – Daniel Gleitman (281-871-6146 or
NETL – Roy Long (918-699-2017 or