Drilling Systems & Borehole Instrumentation
EES-11 is conducting a broad-based microborehole technology integration and development program with three initiatives at various stages of development:
(1) Reduce the costs of deploying downhole geotechnical instruments using properly scaled conventional drilling technology, and state-of-the-art sensors and downhole instrumentation to minimize equipment costs and environmental impacts. This intermediate term research is aimed at commercial resource exploitation and deep earth science.
(2) Provide a shallow to medium depth test platform for developing, testing and evaluating drilling systems based on advanced, non-commercial drilling processes. Produce methodologies needed to evaluate advanced drilling concepts and develop appropriate proof-of-concept experiments. This long-term research is aimed at future exploitation of presently non-commercial resources, planetary exploration, and national security needs
(3) Provide a small test platform to develop, test, and demonstrate the integration of instrumentation and drilling systems to produce highly-automated, optimally-controlled drilling systems. Develop drilling systems that can be deployed in ultra-remote, unattended operating modes. This long-term research is aimed at future exploitation of presently non-commercial resources, ocean-bottom and arctic drilling, planetary exploration, and national security problems.
Initiative 1 - The results from modeling, laboratory testing and cost analyses, combined with a number of microdrilling component proposals from industry, strongly support the feasibility of using coiled tubing to drill microboreholes as small as 1-3/8 inches in diameter. To address the exploration and reservoir interrogation objectives expressed by a number of industry representatives, these microboreholes will need to be as deep as 10,000 ft and have an extremely small footprint and environmental impact to attract substantial commercial interest. Realistically, microhole well programs will need to provide full pressure control, well stability, and directional drilling technology that is routinely used in deep holes. This will include: micro-completion technology; appropriate, miniaturized surface and intermediate casing string;, cementing of very small annuli; cased-hole micro-logging; and micro-perforating technology.
Commercially-available small-diameter components were assembled into several bottomhole drilling assemblies and tested by Los Alamos in an industrial laboratory. Motor-, thrust-, and bit-performance demonstrated that off-the-shelf components were suitable for coiled tubing drilling of 1-3/4- and 2-3/8-inch bores using mud motors. Penetration rates in intermediate and high modulus rocks were comparable to conventional sized assemblies (Dreesen et al., 1996). Testing with air-mist, air-foam, and areated water showed that present drilling motor technology will be marginal if underbalanced microdrilling is deployed on coiled-tubing. Modeling to understand the loss of motor performance with compressible fluids is attempting to predict experimental results. Compressible fluid power transport and power conversion processes need to be modeled in order to design improved coiled-tubing microdrilling systems for compressible drilling fluids.
Los Alamos began field-testing of 2-3/8-inch drilling assemblies in September 1998 with the procurement and modification of a coiled-tubing drilling rig designed to explore the technical hurdles of microhole drilling in shallow tests (up to 400 ft). Drilling 1-3/4-inch bores to 1000- ft with this rig is anticipated, and drilling 1-1/8-inch holes to 1750-ft on 3/4-inch coiled tubing in under investigation. To the best of our knowledge, 2-3/8-inch is the smallest hole size yet attempted with coiled-tubing drilling.
Early on, the DeepLook Collaboration funded the first phase of the development of true microhole drilling assemblies capable of drilling 1-1/8 to 1-3/8 inch bores. A cost study has shown that microholes of these dimensions have the potential to be drilled at a fraction of the cost of conventional-sized holes. Based on simple scaling relationships, materials costs (e.g., muds, steel) may be only 2% to 4% of current values. Similarly, substantial reductions can be expected for the cost of wireline draw works, hoisting and telemetry cables, and borehole instrumentation as microhole technology development extends into formation logging.
In parallel with our microhole drilling project, is an effort to combine microholes and miniature instrumentation to proliferate borehole seismic measurements of signals from production-related and artificial sources. While awaiting the demonstration of a deep microhole drilling capability, we are developing and demonstrating the usefulness of miniaturized seismic instrumentation in shallow microholes and in creating new deployment possibilities. A good example of these possibilities is this project's design and installation of microtool access tubing in a stripper well at Texaco's Humble field, northeast of Houston. This installation enables repeated access to the well for microsensor seismic measurements without the cost of pulling the 2-7/8-inch production string. To date 1-gram geophones, a hydrophone and micromachined silicon accelerometer have been packaged and evaluated.
Initiatives 2 and 3 - Internal funding is supporting the development of a coiled-tubing-deployed, rock melting drill demonstration. A 400-ft-long, 1-inch OD coiled tubing is being equipped with telemetry and electric power cables to power and instrument a 2-inch OD rock melting drill. The tubing will be installed on a prototype tubing reel that will support the special utilities required. This drilling demonstration is intended to show the synergy of continuous drill stem and thermal drilling and provide the first downhole instrumentation run on a rock melting drill. It will also demonstrate the utility of testing advanced concept drills on coiled-tubing.
Proposals to construct a special tubing and reel to demonstrate spallation drilling on coiled tubing are in preparation and potential sponsors are being identified.
Advanced concept drilling has potential applications for national security programs, NASA planetary drilling, and commercial exploitation of resources that are beyond the reach of conventional drilling technology.
External Reviews - Annual review by oil and gas industry representatives to the Natural Gas and Oil Recovery Partnership. In 1998, the Microhole Drilling Project was ranked 1st by the partnership out of 12 national laboratory proposals dealing with drilling and completion. The Microhole Instrumentation Project ranked 2nd out of a similar number of proposals dealing with subsurface imaging.
Collaborators On One or More Projects - Texaco, Phillips, Mark Products, Input/Output Inc., Mobil, and the DeepLook Collaboration (BP, Chevron, Shell, Conoco, Unocal, and several service companies).
Coiled-Tubing Deployed Microdrilling Update 2001 - A Word 9.0 Document
The Application of Microhole Technology to the Development of Coalbed Methane Resources at Remote Locations - 494KB PDF File
Microhole Technology - Progress on Borehole Instrumentation Development (1.4 MB PDF File)