Sandia National Laboratories
Description
Slant Angle Sonic Drilling (SASD) is a method of rapid access to the subsurface for installation of a sloped well using resonant drilling methods. A high-power hydraulic oscillator containing eccentric, counter-rotating rollers utilizes inertia to effect a high-frequency, third-harmonic, sinusoidal standing wave in the drill pipe and drill head. In addition, to vibration, the resonant drill head also rotates, creating a very efficient cutting action in any geologic formation. Penetration rates are geology dependent, but the sonic drilling method can penetrate any formation including landfills, enabling penetration through boulders, metals, tires, wood, and concrete. The slant angle rig allows a well to be drilled at any angle from vertical to nearly horizontal. A hydraulically activated pull-down mechanism effects penetration into the formation. Below is a schematic of a sonic drill.
Various benefits arise from this drilling technique such as rapid penetration (speed), waste minimization, and high-quality core removal (including alluvial soils). The resulting cutting action of the drill head forces a continuous core of the formation up into the drill string. Moreover, the high forces developed and external flushing nature of the specialized drill string forces excess geologic material into the borehole wall. The result is that no additional cuttings are generated or removed from the subsurface other than the continuous core. This has great economic advantage when applied to an environmental application, such as, sampling below a chemical waste landfill or an application with radioactive soil contamination. The resonant drilling method requires no drilling fluids for lubrication or cutting removal; this contributes to the production of a high-quality continuous core that is useful for both geologic and contaminant analysis of the subsurface formation.
Technology developments in the form of feedback control and advanced hardware design will improve both the speed of this technique and its component reliability. The advancement of this technology will include an analog or digital feedback control circuit, as well as laboratory and field analysis of bit temperature, bit design, and downhole drill rod temperatures. The developers are in the conceptual stages of incorporating a method of downhole steering into this drilling technology to vary the drill angle during well drilling.
Technical Performance Data
This technology has been successfully applied to continuous coring, monitoring well construction, and horizontal drilling activities. A demonstration of the improved system, with feedback control and component redesign for improved reliability and more rapid access, is planned.
Drill Head. Dynamic force output is 30,000 lbs at 120 Hz. Power input is 150 hp. Rotational torque is 25,500 in.-lb; rotational speed is 60 rpm.
Drill Rig. Pull down force is 10,000 lb; the pull down rate is 100 ft/min. Angle capacity is 45 to 90° off the truck, and 5 to 45° is off standing mounting plates.
Speed of Drilling. The penetration rate of the sonic drill varies depending on the type of formation being cut. Speeds from 1 ft/s to 0.5 ft/min are encountered when drilling loose to compact formations.
Formations. The sonic drills any type of formation: alluvium, sands, clays, cobbles, boulders, bedrock, permafrost, caliche, and other types of formations including landfills. It is able to drill through metals, garbage, tires, wood, and concrete.
Cost/Benefits. The cost is approximately $100/ft for cased angled hole with continuous core. Drilling requires no fluid, and no cuttings are generated, which eliminates several waste streams and disposal costs. The result is savings of support staffing and cost savings for management of excess contaminated drill cuttings. There is a 95 to 100% core return in alluvial soil versus 60% for conventional drilling. Core sizes range from 2 to 12 in. in diameter depending on the dictates of the drilling program.
Projected Performance
The drilling speed and component reliability are expected to improve with the inclusion of feedback control and component redesign.
Waste Applicability
This technology is applicable for monitoring wells, vadose zone soil gas sampling, neutron probe pipe installation, core sampling, and injection and extraction wells for bioremediation and/or air stripping/vacuum extraction remediation projects. Additionally, in most conditions, closed-end tubes can be resonated into the ground to significant depths to yield no cuttings or core and to take discrete water samples or in situ cores.
Status
Resonant sonic drilling has existed for over thirty years, originating from the work of its inventor, A. G. Bodine. The application of this technology has been well demonstrated by the developers, the Water Development Corporation. There are eleven known U.S. based sonic drill heads and rigs, ten of which are operated by Water Development Corporation. This technology is currently available, with process improvements (feedback control and hardware redesign) expected within 2 to 3 yrs.
Regulatory Considerations
Drilling and subsurface access regulations may vary depending on the waste site characteristics. Ecological impacts are minimized or eliminated by the absence of secondary waste streams. Occupational Safety and Health Administration (OSHA) regulations apply for drilling equipment operation, high noise levels, and potential contaminant exposure.
Potential Commercial Applications
This technology can be applied to water well, natural gas well, geothermal well, and oil well drilling. It is also useful to industries that may have soil or groundwater contamination problems. Rapid access to the subsurface, without excess soil removal or secondary waste streams, is economically desirable for such industries to determine the scope of the problem and to remediate the contamination. This method of continuous core removal is useful for other geologic studies and to the mining industry.
Baseline Technology
This technology is compared to other conventional drilling methods, such as hollow stem auger, air and, mud rotary drill rigs that are traditionally used for oil, gas, and river-crossing applications. Field results demonstrate that the daily output of one sonic drill rig will approximate the daily continuous core output of three to four hollow stem auger rigs.
Intellectual Property Rights
U.S. patents for Resonant Sonic Drilling technologies are held by the Water Development Corporation (WDC). Patent numbers are available from the technology developer, WDC.
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References
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