Yarom Polsky

Enhanced Geothermal Systems (EGS) well construction technology evaluation report.

A synopsis of a report evaluating well construction technology for Enhanced Geothermal Systems (EGS) is presented. The assessment of well construction technology had two primary objectives: 1. Determining the ability of existing technologies to develop EGS wells. 2. Identifying critical well construction research lines and development technologies that are likely to enhance prospects for EGS viability and improve overall economics. Towards these ends, a methodology was followed in which a case study was developed to systematically and quantitatively evaluate EGS well construction technology needs. This paper provides an overview of the analysis and highlights key findings.

Laboratory Simulation of Drill Bit Dynamics Using a Model-Based Servohydraulic Controller

Drilling costs are significantly influenced by bit performance when drilling in offshore formations. Retrieving and replacing damaged downhole tools is an extraordinarily expensive and time-intensive process, easily costing several hundred thousand dollars of offshore rig time plus the cost of damaged components. Dynamic behavior of the drill string can be particularly problematic when drilling high strength rock, where the risk of bit failure increases dramatically. Many of these dysfunctions arise due to the interaction between the forces developed at the bit-rock interface and the modes of vibration of the drill string. Although existing testing facilities are adequate for characterizing bit performance in various formations and operating conditions, they lack the necessary drill string attributes to characterize the interaction between the bit and the bottom hole assembly (BHA). A facility that includes drill string compliance and yet allows real-rock/bit interaction would provide an advanced practical understanding of the influence of drill string dynamics on bit life and performance. Such a facility can be used to develop new bit designs and cutter materials, qualify downhole component reliability, and thus mitigate the harmful effects of vibration. It can also serve as a platform for investigating process-related parameters, which influence drilling performance and bit-induced vibration to develop improved practices for drilling operators. The development of an advanced laboratory simulation capability is being pursued to allow the dynamic properties of a BHA to be reproduced in the laboratory. This simulated BHA is used to support an actual drill bit while conducting drilling tests in representative rocks in the laboratory. The advanced system can be used to model the response of more complex representations of a drill string with multiple modes of vibration. Application of the system to field drilling data is also addressed.

Thermoelastic Modeling of a PWB With Simulated Circuit Traces Subjected to Infrared Reflow Soldering With Experimental Validation

A bare, four copper layer printed wiring board with simple trace patterns was built for modeling and experimental validation purposes. In-plane elastic properties of the core materials in the board were measured as a function of temperature. Thermoelastic lamination theory was utilized to predict the warpage of the board when subjected to an infrared reflow process, with emphasis on studying the influence of thermal gradients through the board, its support conditions and CTE differential on the warpage process. Board layers with traces were approximated with quasi-homogeneous effective properties obtained using micromechanics theory. An experimental system that employs the shadow moird technique in a simulated infrared reflow environment was used to evaluate the warpage for comparison to modeled results.

Derivation of the Casimir limit phonon distribution using the Boltzmann transport equation

The modes of energy transfer in solid thin films of electrically insulating material are lattice vibrations, which take the form of elastic waves. These energy waves are quantized and referred to as phonons. Phonon theory combines mechanics, statistics, thermodynamics, and quantum theory to provide an approximation for the energy transferred through a lattice due to disturbances in the equilibrium distances between atoms. On the macroscale, the heat transfer can be modeled by Fourier`s equation as q = -{lambda}{triangledown}T, where {triangledown}T is the local temperature gradient. This model yields accurate results when the mean free path of the phonons is much smaller than the thickness of the film. This form of transport is referred to as conductive transport and is based on an approximation of scattering events and phonon-phonon interference occurring within the solid. 12 refs.

Neutron imaging for geothermal energy systems

Geothermal systems extract heat energy from the interior of the earth using a working fluid, typically water. Three components are required for a commercially viable geothermal system: heat, fluid, and permeability. Current commercial electricity production using geothermal energy occurs where the three main components exist naturally. These are called hydrothermal systems. In the US, there is an estimated 30 GW of base load electrical power potential for hydrothermal sites. Next generation geothermal systems, named Enhanced Geothermal Systems (EGS), have an estimated potential of 4500 GW. EGSs lack in-situ fluid, permeability or both. As such, the heat exchange system must be developed or “engineered” within the rock. The envisioned method for producing permeability in the EGS reservoir is hydraulic fracturing, which is rarely practiced in the geothermal industry, and not well understood for the rocks typically present in geothermal reservoirs. High costs associated with trial and error learning in the field have led to an effort to characterize fluid flow and fracturing mechanisms in the laboratory to better understand how to design and manage EGS reservoirs. Neutron radiography has been investigated for potential use in this characterization. An environmental chamber has been developed that is suitable for reproduction of EGS pressures and temperatures and has been tested for both flow and precipitations studies with success for air/liquid interface imaging and 3D reconstruction of precipitation within the core.

Development of a High-Temperature Diagnostics-While-Drilling Tool

The envisioned benefits of Diagnostics-While-Drilling (DWD) are based on the principle that high-speed, real-time information from the downhole environment will promote better control of the drilling process. Although in practice a DWD system could provide information related to any aspect of exploration and production of subsurface resources, the current DWD system provides data on drilling dynamics. This particular set of new tools provided by DWD will allow quicker detection of problems, reduce drilling flat-time and facilitate more efficient drilling (drilling optimization) with the overarching result of decreased drilling costs. In addition to providing the driller with an improved, real-time picture of the drilling conditions downhole, data generated from DWD systems provides researchers with valuable, high fidelity data sets necessary for developing and validating enhanced understanding of the drilling process. Toward this end, the availability of DWD creates a synergy with other Sandia Geothermal programs, such as the hard-rock bit program, where the introduction of alternative rock-reduction technologies are contingent on the reduction or elimination of damaging dynamic effects. More detailed descriptions of the rationale for the program and early development efforts are described in more detail by others [SAND2003-2069 and SAND2000-0239]. A first-generation low-temperature (LT) DWD system was fielded in a series of proof-of-concept tests (POC) to validate functionality. Using the LT system, DWD was subsequently used to support a single-laboratory/multiple-partner CRADA (Cooperative Research and Development Agreement) entitled Advanced Drag Bits for Hard-Rock Drilling. The drag-bit CRADA was established between Sandia and four bit companies, and involved testing of a PDC bit from each company [Wise, et al., 2003, 2004] in the same lithologic interval at the Gas Technology Institute (GTI) test facility near Catoosa, OK. In addition, the LT DWD system has been fielded in cost-sharing efforts with an industrial partner to support the development of new generation hard-rock drag bits. Following the demonstrated success of the POC DWD system, efforts were initiated in FY05 to design, fabricate and test a high-temperature (HT) capable version of the DWD system. The design temperature for the HT DWD system was 225 C. Programmatic requirements dictated that a HT DWD tool be developed during FY05 and that a working system be demonstrated before the end of FY05. During initial design discussions regarding a high-temperature system it was decided that, to the extent possible, the HT DWD system would maintain functionality similar to the low temperature system, that is, the HT DWD system would also be designed to provide the driller with real-time information on bit and bottom-hole-assembly (BHA) dynamics while drilling. Additionally, because of time and fiscal constraints associated with the HT system development, the design of the HT DWD tool would follow that of the LT tool. The downhole electronics package would be contained in a concentrically located pressure barrel and the use of externally applied strain gages with thru-tool connectors would also be used in the new design. Also, in order to maximize the potential wells available for the HT DWD system and to allow better comparison with the low-temperature design, the diameter of the tool was maintained at 7-inches. This report discusses the efforts associated with the development of a DWD system capable of sustained operation at 225 C. This report documents work performed in the second phase of the Diagnostics-While-Drilling (DWD) project in which a high-temperature (HT) version of the phase 1 low-temperature (LT) proof-of-concept (POC) DWD tool was built and tested. Descriptions of the design, fabrication and field testing of the HT tool are provided. Background on prior phases of the project can be found in SAND2003-2069 and SAND2000-0239.

Development of a Mine Rescue Drilling System (MRDS)

Sandia National Laboratories (Sandia) has a long history in developing compact, mobile, very high-speed drilling systems and this technology could be applied to increasing the rate at which boreholes are drilled during a mine accident response. The present study reviews current technical approaches, primarily based on technology developed under other programs, analyzes mine rescue specific requirements to develop a conceptual mine rescue drilling approach, and finally, proposes development of a phased mine rescue drilling system (MRDS) that accomplishes (1) development of rapid drilling MRDS equipment; (2) structuring improved web communication through the Mine Safety & Health Administration (MSHA) web site; (3) development of an improved protocol for employment of existing drilling technology in emergencies; (4) deployment of advanced technologies to complement mine rescue drilling operations during emergency events; and (5) preliminary discussion of potential future technology development of specialized MRDS equipment. This phased approach allows for rapid fielding of a basic system for improved rescue drilling, with the ability to improve the system over time at a reasonable cost.