TULSA, OK - The Department of Energy continues to
mark progress in advancing its “microhole” initiative, a revolutionary
new approach to drilling America’s oil and natural gas wells. The
scale-down of two tools essential for the initiative has been deemed feasible
under a DOE-funded project.
The new technology, which entails integrating a suite of high-tech tools
with ultra-small diameter boreholes, promises to slash operators’
costs, decrease drilling risks, and dramatically reduce the environmental
impacts of oil and gas drilling.
In microhole drilling, slim coiled tubing spooled on a pickup truck is
used to drill wells instead of using conventional, wide-diameter drill
pipe assembled into massive strings on large, conventional drilling rigs—a
traditional method suited only for much larger boreholes. Critical to
the initiative is the development of micro-instruments that are small
enough to fit into the micro-boreholes yet rugged enough to withstand
the harsh downhole conditions.
Two such high-tech tools are a rib steering device (RSD) and a multiple
propagation resistivity (MPR) device designed for 2-inch coiled tubing.
RSD technology employs a downhole guidance system that continually adjusts
the drill bit’s course; it uses pads, or ribs, to steer while drilling
continuously, enabling the operator to change drilling angles without
interrupting the rotation of the drill pipe string. Resistivity measures
a formation’s resistance to electrical current, which is used to
determine whether the formation holds hydrocarbons or water. MPR employs
an array of antennas that propagate multiple electromagnetic signals at
different frequencies. The technologies are intended to give the operator
better control over drilling progress and better information about what
the drill bit is encountering downhole.
A first round microhole technology project, managed for DOE by the National
Energy Technology Laboratory, seeks to develop an RSD and an MPR device
for coiled tubing that is only 2 inches in diameter. Baker Hughes
INTEQ, through system concept development and a larger tool field survey,
has determined that the appropriate technology is available and can be
modified for microhole application.
For the RSD, the problem is primarily one of developing a 2⅜-inch
tool that can maintain structural integrity. Modeling and drawing tasks
have indicated that, at this stage of the project, construction of a 2⅜-inch
RSD is feasible.
For the MPR device, the problems associated with scaling down the size
are to maintain structural integrity and still achieve the fidelity of
resistivity measurement of the larger tool sizes. The construction of
a 2⅜-inch MPR device nevertheless appears to be feasible, according
to project investigators.
Several draft designs of these tools are undergoing evaluation to identify
the optimum setup. In addition, Baker Hughes INTEQ has performed calculations
to evaluate the maximum bending stresses that the new components may encounter
when integrated into existing coiled tubing bottom-hole assemblies.
The next step will be to work through the detailed design process to
reach a critical decision point: whether or not to enter into the manufacturing
stage. A decision is expected by June 30, 2005. If that decision is a
“go,” then Baker Hughes INTEQ will manufacture two prototypes
of each tool and test them in the lab, as well as in the field.
What makes this an important milestone is underscored by the target of
DOE’s Microhole Initiative. About two thirds of all the oil discovered
in the United States remains in the ground. Of that, over half (218 billion
barrels) lies in reservoirs shallower than 5,000 feet and is unrecoverable
with current technology or because of poor economics. Recovering just
10 percent of that shallow target resource would yield a volume equal
to the nation’s current level of total proved oil reserves.
America’s oil and gas field operators—mostly small producers
without access to high-tech solutions—continue to try to squeeze
out more oil from aging, nearly depleted shallow oilfields by drilling
more infill wells (those spaced between existing producing wells). More
than 20,000 shallow infill wells are drilled each year in the United States—and
nearly as many low-producing wells are abandoned each year because of
eroding economics. The reductions in drilling costs that microhole technology
yields—ranging from one third to more than one half—could
spawn a wave of infill drilling across the nation’s mature, declining
Microhole technology offers more than a low-cost means to drill a lot
of infill wells. It also reduces exploratory drilling risk by allowing
an operator to deploy downhole seismic sensors in a cost-effective way
in order to gain a better image of the subsurface. And the environmental
benefits of microhole technology are manifested in the smaller “footprint”
of the truck-mounted coiled tubing rigs and in the greatly reduced drilling
wastes resulting from a smaller hole.
The goal of DOE’s microhole
initiative is to support reservoir life extension and domestic resource
conservation by facilitating efforts to find, characterize, and develop
shallow domestic oil and natural gas resources inexpensively. Current
projects under the program focus on demonstrating present microhole technology
capabilities and developing missing key technology components. Microhole
technology consists of techniques and tools used to drill, complete, and
characterize reservoirs up to 5,000 feet deep in a 3½-inch diameter