Tech Transfer Track

Custom-Designed Bits Improve Drilling Performance

Two case studies, one a hardrock slimhole horizontal in New Mexico and a second North Texas vertical well, demonstrate how custom-designed bits can lower costs and improve drilling performance. In the slimhole horizontal example, high bit failures were being experienced in a section that was 70-90% chert. After several failures, RBI-Gearhart examined dull bits and failure modes. The gage-row area reflected insert breakage as the primary failure mode with the inner-row, flat-crested wear being a secondary mode. The solution involved a simple modification that changed the insert carbide grade and increased the insert count. New custom-designed bits were on bottom within six days. Rates of penetration in the chert were doubled, lowering the average cost per foot nearly 60%.

In North Texas, an operator wanted to improve drilling efficiency of a formation consisting of shale with chert stringers. Reviewing drilling histories of earlier wells in the area, RBI-Gearhart determined that three different bit types were required—one for the top, middle and bottom sections. Data were summarized for 14 wells drilled with the same rig using off-the-shelf bit designs. An initial test well using that rig and off-the-shelf bit designs duplicated results from the 14 well sample. On the second well, a custom-designed bit for the upper section lowered costs per foot in that section by 20%. In the third well, a custom-designed bit for the middle section lowered costs per foot in that section by 37%. These formation-specific bits and a third slightly modified bit for the bottom section were used in the fourth and final well. Average cost per foot, compared to the original 14 wells, was lowered by 28%. The overall custom design project took 45 days, but benefits will be realized in many wells yet to be drilled.

Excerpted from "Custom-Designed Bits Improve Efficiency, Lower Costs," Jack Castle, RBI-Gearhart, Oil and Gas Journal, Dec. 22, 2003, pp. 60-62.

Global Energy Partners, LLC (GEP), with $1.7 million of funding support through the California Public Utilities Commission (CPUC), has been working for the last 18 months with small independent producers in an energy efficiency program for small independents in Southern California. PTTC's West Coast Region has been supporting with technology transfer. Both were involved in an earlier study that identified the energy saving opportunities and led to the CPUC funding.

The program provides incentives such as free energy consumption audits for qualified wells, training and incentives totaling up to 50% of the installation cost of qualified energy efficiency measures. Program funds have been committed and field visits are underway to gather data confirming the savings achieved. In a nutshell, the program worked. Following the systematic analysis procedure offered by GEP, the results thus far have indicted that the operators are able to recoup their limited investments in just a few months and can enjoy substantial savings in their operating cost. Power consumption has/will be influenced on more than 200 wells. Achieved power savings in kW and kWh exceeded planning expectations by 21% and 39% respectively.

The program uses a systems approach to diagnose problems and savings possible with different solutions. Energy efficiency measures employed have included pump-off controllers, variable frequency drives, load balancing on rod pumps, proper sizing of water injection pumps, variable frequency prime movers, optimization of fluid cooling systems and premium efficiency motors. GEP has developed a template that enables producers to quickly determine potential impacts.

Results are being shared in a May 27th PTTC workshop in Los Angeles (see calendar, p. 15). This workshop will also be webcast so

In the Gulf of Mexico, Chevron Texaco and Schlumberger Oilfield Services achieved a new U.S. depth record, reaching 31,824 ft true vertical depth in the Tonga 1, Green Canyon Block 727. New records were set for pressure (26,138 psi) and measurement-while-drilling (MWD) and logging-while-drilling (LWD) depths. Schlumberger delivered continuous real-time surveys, allowing the well trajectory to be kept on target throughout the entire logging/drilling process. Drilling was conducted from Transocean's Discoverer Deep Seas drillship.

Editors Note: In the trivia question in its Feb 25 E-mail Tech Alert, PTTC noted that the Bertha Rogers #1, Oklahoma, had the U.S. depth record. That was true until the Tonga 1, as an informed reader pointed out. PTTC apologizes for that prior error.

Excerpted from World Oil column, Drilling Advances, February 2004, p. 17.

Gulf Research, a subsidiary of Gulf Publishing, recently released its "2003 Deepwater/Deep Shelf Technology Needs Assessment" study. More than 200 individuals in exploration, drilling, completions and production job functions were interviewed. Results reveal how industry prioritizes over 60 major technical needs in the deepwater environment.

Interested subscribers should contact Lanie Finlayson, E-mail lanie.finlayson@gulfresearch.
com.