Publications

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Carbon sequestration is a growing field that requires subsurface monitoring for potential leakage of the sequestered fluids through the casing annulus. Sandia National Laboratories (SNL) is developing a smart collar system for downhole fluid monitoring during carbon sequestration. This technology is part of a collaboration between SNL, University of Texas at Austin (UT Austin) (project lead), California Institute of Technology (Caltech), and Research Triangle Institute (RTI) to obtain real-time monitoring of the movement of fluids in the subsurface through direct formation measurements. Caltech and RTI are developing millimeter-scale radio frequency identification (RFID) sensors that can sense carbon dioxide, pH, and methane. These sensors will be impervious to cement, and as such, can be mixed with cement and poured into the casing annulus. The sensors are powered and communicate via standard RFID protocol at 902-928 MHz. SNL is developing a smart collar system that wirelessly gathers RFID sensor data from the sensors embedded in the cement annulus and relays that data to the surface via a wired pipe that utilizes inductive coupling at the collar to transfer data through each segment of pipe. This system cannot transfer a direct current signal to power the smart collar, and therefore, both power and communications will be implemented using alternating current and electromagnetic signals at different frequencies. The complete system will be evaluated at UT Austin's Devine Test Site, which is a highly characterized and hydraulically fractured site. This is the second year of the three-year effort, and a review of SNL's progress on the design and implementation of the smart collar system is provided.

Drill rig parameter measurements are routinely used during deep well construction to monitor and guide drilling conditions for improved performance and reduced costs. While insightful into the drilling process, these measurements are of reduced value without a standard to aid in data evaluation and decision making. A method is demonstrated whereby rock reduction model constraints are used to interpret drilling response parameters; the method could be applied in real-time to improved decision-making in the field and to further discern technology performance during post-drilling evaluations. Drill rig parameter data were acquired by drilling contractor Frontier Drilling and evaluated for two wells drilled at the DOE-sponsored site, Utah Frontier Observatory for Research in Geothermal Energy (FORGE). The subject wells include: 1) FORGE 16A(78)-32, a directional well with vertical depth to a kick-off point at 5892 ft and a 65 degree tangent to a measured depth of 10987 ft and, 2) FORGE 56-32, a vertical monitoring well to a measured depth of 9145 ft. Drilling parameters are evaluated using laboratory-validated rock reduction models for predicting the phenomenological response of drag bits (Detournay and Defourny, 1992) along with other model constraints in computational algorithms. The method is used to evaluate overall bit performance, develop rock strength approximations, determine bit aggressiveness, characterize frictional energy losses, evaluate bit wear rates, and detect the presence of drillstring vibrations contributing to bit failure; comparisons are made to observations of bit wear and damage. Analyses are also presented to correlate performance to bit run cost drivers to provide guidance on the relative tradeoff between bit penetration rate and life. The method presented has applicability to development of advanced analytics on future geothermal wells using real-time electronic data recording for improved performance and reduced drilling costs.

Drill rig parameter measurements are routinely used during deep well construction to monitor and guide drilling conditions for improved performance and reduced costs. While insightful into the drilling process, these measurements are of reduced value without a standard to aid in data evaluation and decision making. A method is demonstrated whereby rock reduction model constraints are used to interpret drilling response parameters; the method could be applied in real-time to improved decision-making in the field and to further discern technology performance during post-drilling evaluations. Drill rig parameter data were acquired by drilling contractor Frontier Drilling and evaluated for two wells drilled at the DOE-sponsored site, Utah Frontier Observatory for Research in Geothermal Energy (FORGE). The subject wells include: 1) FORGE 16A(78)-32, a directional well with vertical depth to a kick-off point at 5892 ft and a 65 degree tangent to a measured depth of 10987 ft and, 2) FORGE 56-32, a vertical monitoring well to a measured depth of 9145 ft. Drilling parameters are evaluated using laboratory-validated rock reduction models for predicting the phenomenological response of drag bits (Detournay and Defourny, 1992) along with other model constraints in computational algorithms. The method is used to evaluate overall bit performance, develop rock strength approximations, determine bit aggressiveness, characterize frictional energy losses, evaluate bit wear rates, and detect the presence of drillstring vibrations contributing to bit failure; comparisons are made to observations of bit wear and damage. Analyses are also presented to correlate performance to bit run cost drivers to provide guidance on the relative tradeoff between bit penetration rate and life. The method presented has applicability to development of advanced analytics on future geothermal wells using real-time electronic data recording for improved performance and reduced drilling costs.

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Directional drilling can be used to enable multi-lateral completions from a single well pad to improve well productivity and decrease environmental impact. Downhole rotation is typically developed with a motor in the Bottom Hole Assembly (BHA) that develops drilling power necessary to rotate the bit apart from the rotation developed by the surface rig. Historically, wellbore deviation has been introduced by a “bent-sub” that introduces a small angular deviation to allow the bit to drill off-axis with orientation of the BHA controlled via surface rotation. The geothermal drilling industry has not realized the benefit of Rotary Steerable Systems, and struggles with conventional downhole rotation systems that use bent-subs for directional control due to shortcomings with downhole motors. Commercially-available Positive Displacement Motors are limited to approximately 350 F (177C) and introduce lateral vibration to the bottom hole assembly contributing to hardware failures and compromising directional drilling objectives. Mud turbines operate at higher temperatures but do not have the low-speed, high torque performance envelope for use with conventional geothermal drill bits. Development of a fit-for purpose downhole motor would enable geothermal directional drilling. Sandia National Laboratories is developing technology for a downhole piston motor to enable directional drilling in high temperature, high strength rock. Application of conventional hydraulic piston motor power cycles using drilling fluids is detailed. Work is described regarding conceiving downhole piston motor power sections; modeling and analysis of potential solutions; and development and laboratory testing of prototype hardware. These developments will lead to more reliable access to geothermal resources and allow preferential wellbore trajectories resulting in improved resource recovery, decreased environmental impact and enhanced well construction economics.

Directional drilling can be used to enable multi-lateral completions from a single well pad to improve well productivity and decrease environmental impact. Downhole rotation is typically developed with a motor in the Bottom Hole Assembly (BHA) that develops drilling power (speed and torque) necessary to drive rock reduction mechanisms (i.e., the bit) apart from the rotation developed by the surface rig. Historically, wellbore deviation has been introduced by a “bent-sub,” located in the BHA, that introduces a small angular deviation, typically less than 3 degrees, to allow the bit to drill off-axis with orientation of the BHA controlled at the surface. The development of a high temperature downhole motor would allow reliable use of bent subs for geothermal directional drilling. Sandia National Laboratories is pursuing the development of a high temperature motor that will operate on either drilling fluid (water-based mud) or compressed air to enable drilling high temperature, high strength, fractured rock. The project consists of designing a power section based upon geothermal drilling requirements; modeling and analysis of potential solutions; and design, development and testing of prototype hardware to validate the concept. Drilling costs contribute substantially to geothermal electricity production costs. The present development will result in more reliable access to deep, hot geothermal resources and allow preferential wellbore trajectories to be achieved. This will enable development of geothermal wells with multi-lateral completions resulting in improved geothermal resource recovery, decreased environmental impact and enhanced well construction economics.

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Percussive hammers are a promising advance in drilling technology for geothermal since they rely upon rock reduction mechanisms that are well-suited for use in the hard, brittle rock characteristic of geothermal formations. The project research approach and work plan includes a critical path to development of a high-temperature (HT) percussive hammer using a two- phase approach. The work completed in Phase I of the project demonstrated the viability of percussive hammers and that solutions to technical challenges in design, material technology, and performance are likely to be resolved. Work completed in Phase II focused on testing the findings from Phase I and evaluating performance of the materials and designs at high- operating temperatures. A high-operating temperature (HOT) drilling facility was designed, built, and used to test the performance of the DTH under extreme conditions. Results from the testing indicate that a high-temperature capable hammer can be developed and is a viable alternative for user in the driller's toolbox.

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Percussive hammers are a promising advance in drilling technology for geothermal since they rely upon rock reduction mechanisms that are well-suited for use in the hard, brittle rock characteristic of geothermal formations. Also known as down-the-hole (DTH) hammers, they are also compatible with low-density fluids that are often used for geothermal drilling. Experience in mining and oil and gas drilling has demonstrated their utility for penetrating hard rock. One limitation to more wide-scale deployment is the ability of the tools to operate at high temperatures (∼300°C) due to elastomers used in the construction and the lubrication required for operation. As part of a United States Department of Energy Funding Opportunity Announcement award, Atlas Copco was tasked with developing a high-temperature DTH capable of being used in geothermal environments. A full-scale development effort including design, build, and testing was pursued for the project. This report summarizes the results of the percussive hammer development efforts between Atlas-Copco Secoroc and Sandia National Labs as part of DE-FOA-EE0005502. Certain design details have been omitted due to the proprietary nature of the information.

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The dynamic stability of deep drillstrings is challenged by an inability to impart controllability with ever-changing conditions introduced by geology, depth, structural dynamic properties and operating conditions. A multi-organizational LDRD project team at Sandia National Laboratories successfully demonstrated advanced technologies for mitigating drillstring vibrations to improve the reliability of drilling systems used for construction of deep, high-value wells. Using computational modeling and dynamic substructuring techniques, the benefit of controllable actuators at discrete locations in the drillstring is determined. Prototype downhole tools were developed and evaluated in laboratory test fixtures simulating the structural dynamic response of a deep drillstring. A laboratory-based drilling applicability demonstration was conducted to demonstrate the benefit available from deployment of an autonomous, downhole tool with self-actuation capabilities in response to the dynamic response of the host drillstring. A concept is presented for a prototype drilling tool based upon the technical advances. The technology described herein is the subject of U.S. Patent Application No. 62219481, entitled "DRILLING SYSTEM VIBRATION SUPPRESSION SYSTEMS AND METHODS", filed September 16, 2015.

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