Westinghouse Hanford Company
Description
This drilling technology is an enhancement of the sonic drilling method to obtain representative geologic samples that meet data quality objectives and minimize secondary waste generated. It also reduces costs for drilling by means of its increased productivity, while minimizing operational and contamination exposure hazards to personnel. In addition, sonic drilling is utilized for the deployment of instruments, sensors, and other devices to the subsurface for characterization, remediation, and monitoring purposes. Sonic drilling has three major components: (1) a drill rig with the sonic head, (2) a drill pipe, and (3) a drill bit. Two counterbalances in the drill head rotating at high speed impart energy waves down the drill pipe at frequencies up to 150 c/s that are released at the face of the drill bit. The maximum energy delivered varies, depending on the size of the eccentric rollers and the maximum horsepower delivered to the drill head. The most common size sonic system can provide a maximum of 40,000 lbf. As the drill bit penetrates the soil, the core sample is captured in a tube that rests in the drill bit. Samples are continuously collected and retrieved from the hole using either a wireline retrieval system or by the removal of a sampling string located inside the drill pipe. No circulation medium is required with the sonic method; therefore, the only byproduct from drilling is the core sample. Sonic drilling is a promising method for several drilling applications including characterization borings, groundwater monitoring wells, extraction wells, and barrier installation holes.
Technical Performance Data
Sonic drilling generally produces only the cored sample, and holes are drilled at double the baseline rate. Preliminary testing of sonic drilling at the Hanford Site resulted in a cost reduction of approximately 15-25% over 11 holes, even though downtime from equipment failures was over 45%.
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 lb 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; pull down rate is 100 ft/min. Angle capacity is 45° to 90° off the truck and 5° to 45° 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. It 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. 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 dictates of the drilling program. Cost of a high quality rig is $300K; cost of drill strings is undetermined because of further development work needed. Operations and maintenance costs are approximately 20% higher than for a cable tool, but increased productivity will offset the increased maintenance costs.
Projected Performance
With the refinement of the sonic head, drill pipe, sampling tools, and core catchers, it is projected that the downtime can be reduced to less than 10%, which results in a substantial reduction in drilling costs.
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 30 yrs, 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 the Water Development Corporation operates.
Sonic drilling is currently available, with future improvements planned for products/components and substantial reduction of direct drilling costs and durations. Full implementation for vertical drilling is expected in the 1994-1995 time frame. The following represents best estimates on various application time lines: (1) Vertical and Diagonal Drilling: All chemical and low-level radioactive sites - 1 yr; Medium/high level - 2-3 yrs (2) Horizontal: Feasibility testing - 1 yr; All chemical and low rad - 2-3 yrs; Medium/ high rad - 3-5 yrs. For further information on sonic drilling, see the Slant Angle Sonic Drilling technology being developed by Sandia National Laboratories and the Water Development Corporation.
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 and 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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