The project goal is to develop a Microhole Coiled Tubing Drilling Rig (MCTR) capable of drilling a 3½-inch open hole to 6,000 ft TMD with a 1,000 ft lateral section. The MCTR must be capable of rotary and coiled tubing drilling and be able to drill efficiently, safely, cost-effectively, and with minimal environmental impact.

Schlumberger Well Services, Sugar Land, TX

Coiled tubing drilling of oil and gas wells has been practiced since the early 1990s. Primary drivers for the development of coiled tubing services have been the ability to perform through-tubing re-entry work and to drill underbalanced. To date, a variety of purpose-built CTD rigs exist in various locations around the world. None of them is specifically designed to access the shallow oil and gas reservoirs in the US in a cost-effective way.

Results 
The project performer has acquired a shallow-hole grassroots CTD rig that was operating in Raton, CO. This rig has become the foundation for the development of the MCTR. After evaluation and modification, this rig will be a safe and efficient microhole coiled tubing drilling rig capable of accessing the shallow oil and gas reservoirs in the United States.

Benefits 
Microhole technology offers an alternative to conventional rotary drilling techniques. Rotary drilling typically has larger completion sizes due to limitations imposed by jointed pipe. These larger completions account for higher costs in the way of drilling, completion, and disposal cost. The MCTR’s part in microhole technology is to keep the operating cost to a minimum so all of the economic benefit of drilling a microhole can be realized.

Cost savings to the operator are estimated at as much as $1,071,144 per year. The estimated cost savings was based primarily on increases in efficiency compared with conventional units and the reduction of accidents. Based on the economics calculation, the MCTR could perform an additional 50 days of drilling, or nearly $1,100,000 worth of billable drilling, each year.

A day rate of $20,000 for basic overbalanced drilling was used in the estimate. Higher day rates would be expected for more-complex operations and underbalanced drilling.

Summary 
After acquiring the shallow-hole grassroots CTD rig, it was moved to the Schlumberger equipment testing facility in Rosharon, TX, for modifications and testing.

Two QHSE audits have been performed on the rig, which highlighted several areas for safety improvements. Solutions for all of these items have been developed and completed. For example, handrail and stair improvements will reduce slips, trips, and falls, while additional well control equipment and a high-pressure reel swivel will improve well control.

A complete rig evaluation was performed to provide an equipment baseline. This included a check of all hydraulic and electrical systems as well as an efficiency analysis. The efficiency analysis has highlighted several areas where timesavings will be realized. In particular, rig-up time will be reduced and BOP handling techniques will be improved.

In conjunction with the rig evaluation, a complete data acquisition system has been installed on the unit. This system will provide real-time display of critical parameters for the driller and the ability to record all job data for playback and review.

In addition, an efficient underbalanced tool deployment system has been designed for this rig.

(July 2007) 
The MCTR has completed all testing and modifications to improve safety, efficiency, underbalanced tool deployment, and data acquisition capabilities. The new Coiled Tubing Drilling Rig has been released from the Schlumberger facility located in Rosharon, Texas and has begun commercial duty in the prolific Barnet Shale Play in the Fort Worth Basin in Central Texas. The following activities have been completed:

• Perform required modifications based on QHSE audits.
• Conduct rig-up and rig-down tests to determine areas for additional efficiency gains.
• Complete installation and testing of process control and data acquisition system.
• Design and install underbalanced tool deployment system.
• Perform field test of completed rig on test well to 2,000 ft depth and complete all modifications.

Funding 
This project was selected from DOE’s first Microhole Technologies solicitation, DEPS26-03NT15392, January 30, 2004.

$1,200,000 

$636,423 (35 percent of total)

NETL – Daniel Ferguson (daniel.ferguson@netl.doe.gov or 918-699-2047) 
Schlumberger Well Services - Bartley Patton (patton6@sugar-land.oilfield.slb.com or 281-285-7068)