Publications

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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.

This study evaluates the degradation of six different elastomeric polymers used for O-rings: EPDM, FEPM, type I- and II-FKM, FFKM, and FSR, in five different simulated geothermal environments at 300°C: 1) non-aerated steam/cooling cycles, 2) aerated steam/cooling cycles, 3) water-based drilling fluid, 4) CO2-rich geo-brine fluid, and, 5) heat-cool water quenching cycles. The factors assessed included the extent of oxidation, changes in thermal behavior, micro-defects, permeation of ionic species from the test environments into the O-rings, silicate-related scale-deposition, and changes in the O-rings' elastic modulus. The reliability of the O-rings to maintain their integrity depended on the elastomeric polymer composition and the exposure environment. FSR disintegrated while EPDM was oxidized only to some degree in all the environments, FKM withstood heat-water quenching but underwent chemical degradation, FEPM survived in all the environments with the exception of heat-water quenching where it underwent severe oxidation-induced degradation, and FFKM displayed outstanding compatibility with all the tested environments. This paper discusses the degradation mechanisms of the polymers under the aforementioned conditions.

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This paper aims to evaluate the survival of O-rings made with six different elastomeric polymers, EPDM, type I- and II-FKM, FEPM, FFKM, and FSR, in five different simulated geothermal environments at 300°C. It further defines the relative strengths and weaknesses of the materials in each environment. The environments tested were: 1) non-aerated steam-cooling cycles, 2) aerated steam-cooling cycles, 3) water-based drilling fluid, 4) CO2-rich geo-brine fluid, and, 5) heat-cool water quenching cycles. Following exposure, the extent of oxidation, oxidationinduced degradation, thermal behaviors, micro-defects, permeation depths of ionic species present in environments throughout the O-ring, silicate-related scale-deposition, and changes in mechanical properties were assessed.

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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.

Bottom hole assembly (BHA) designs were assessed in field trials for their ability to achieve critical low inclination requirements, while simultaneously enabling high drill rates. Because angle has historically been controlled by reducing weight on bit (WOB), these are often competing priorities. The use of real time surveillance of mechanical specific energy (MSE) provided unique insights into the bit dysfunction that occurs with many practices used to control angle. These quantitative insights supported the development of BHA and operating practices that maintained low angle while also achieving major gains in drilling performance. The McGinness Hills field in Lander County Nevada is a geothermal operation with wells drilled in hard metamorphic and crystalline formations. Wellbore inclinations must be maintained below 2.0 degrees in the critical 20 inch interval in order to allow use of lineshaft pumps, which is challenging in the required hole sizes and rock hardness. Formation strengths are similar to petroleum operations in the Rockies and West Texas. Pendulum and packed-hole assemblies were tested, and straight motors and slick assemblies were used for corrections. Well build rates were assumed to be controlled by the three-point curvature in the lower assembly and stabilizer placement was modified to control this curvature. The effectiveness of the curvature control as WOB was increased was evaluated from inclination measurements. Real time MSE analysis was used to manage bit operating performance and to determine the root causes of bit dysfunction. The results demonstrated that packed-hole assemblies could be designed that controlled inclination while enabling 2-3 times higher WOB, and that the use of pendulum assemblies should be eliminated. Packed assemblies drilled 87% faster. The increased WOB resulted in higher drill rates, major reduction in whirl and extended bit life, which are equally important performance objectives in hard rock drilling. The use of MSE surveillance allowed the physical processes to be understood deterministically, so that the philosophical design principles can be applied in other petroleum and geothermal operations.

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This Handbook is a description of the complex process that comprises drilling a geothermal well. The focus of the detailed Chapters covering various aspects of the process (casing design, cementing, logging and instrumentation, etc) is on techniques and hardware that have proven successful in geothermal reservoirs around the world. The Handbook will eventually be linked to the GIA web site, with the hope and expectation that it can be continually updated as new methods are demonstrated or proven.