The oil-and-gas industry has become increasingly interested in drilling dynamics and vibration as causes of drilling inefficiency and reduced drilling performance. Generally, drillstring vibration is measured with shock-and-vibration sensors installed in measurement-while-drilling (MWD) tools, logging-while-drilling (LWD) tools, and rotary steerable systems (RSS). Although these tools provide valuable real-time and recorded-mode information on the dynamic conditions, they are not generally designed to capture continuous high-frequency (HF) mechanics and dynamics data, and burst data may miss important information about the evolution of the system response and state.A downhole mechanics measurement tool has been developed that makes a comprehensive suite of measurements of the drilling process, including forces, accelerations, rotational speed, pressures, and temperatures. In addition to providing information in real time, the tool has the capability to capture long durations of continuous data at frequencies between 50 and 2,000 Hz. The recorded-mode information obtained has provided significant insight into the response of the drilling system to starting rotation; drilling procedures and parameter modifications; and exposure to excitation from sources including, but not limited to, rig heave, bottomhole-assembly (BHA) component imbalance, and bit/rock interaction. A wide range of occurrences has been captured in which the drilling system switches from a dominant vibration mode, typically torsional (downhole rotation-velocity oscillations or stick/slip) into a different mode, such as axial (bit bounce) or lateral (whirl). Transitions between different types of whirl have also been recorded.Several cases were studied to investigate the evolution and response of drilling-system behavior on the basis of in-depth interpretation of relatively long durations (minutes to hours) of HF data sets in the operational context. The findings verify the value of using continuous HF vibration data to understand the drilling system and to increase drilling performance.

A drill bit is subjected to rotational speed variation during drilling, ranging from minor rotational speed oscillations to severe speed variation, including stuck phase. The severe speed variation, referred to as stick-slip, is known to be a major source of problems, such as fatigue failures, bit wear, and poor drilling rates. This paper will provide new insight into the mechanisms that drive severe stick-slip based on continuous high-frequency downhole measurements and 3D transient dynamic drilling simulation. To understand the mechanism of severe stick-slip, a series of drilling tests were conducted at a full-scale drilling test facility. An advanced downhole measurement tool was placed in the bottom hole assembly (BHA) to record three-axis shock and vibration, RPM, bending moment, downhole weight on bit (DWOB), downhole torque (DTOR) and internal and annular pressure at high frequency. The drilling system was then modeled on a 3D transient drilling simulation platform, including detailed bit-rock interaction based on single-cutter tests, the exact BHA, and the wellbore geometry. The downhole recorded data showed clear coupling of severe stick-slip, axial load, and bending moment conditions. Interesting patterns observed between RPM, DWOB, DTOR, and bending moment will be presented in detail. The recorded severe stick-slip condition was successfully reproduced by 3D transient dynamic simulation, and the torque, axial load, and bending moment variations along the BHA revealed coupling between torsional, axial, and lateral motions of the drilling system from simulation. Bit-rock interaction and drillstring-wellbore contact are the drivers supporting the coupling. It was found that the coupling of three motions of the drilling system is the most reasonable explanation to the self-sustained severe stick-slip condition. This mechanism can explain the field observed stick-slip trend (i.e., the higher WOB and lower RPM tend to increase the risk of severe stick-slip tendency). Downhole measurements and transient 3D dynamic simulation of the entire drilling system are essential to fully understand this mechanism. Understanding the stick-slip process opens additional opportunities for controlling severe stick-slip. Because the stick-slip mechanism is driven by the coupling of three motions, it is possible to mitigate this condition by breaking the coupling mechanism. For example, a shock sub possibly will reduce the severity of axial coupling due to added axial compliance. Simulation shows breaking the mechanism could reduce the severity of stick-slip. The study being reported in this paper also proved the validity of applying advanced 3D transient dynamic model to obtain a better understanding of drilling system behavior. Drilling simulation might well be an effective way to plan a drilling system and drilling parameters.

Operators of Gulf of Mexico (GOM) wells frequently reported overtorque issue of bottomhole assembly (BHA) connections when drilling the 26-in. section through salt. Such overtorque often leads to costly tool damage beyond repair (DBR), additional trips, and high nonproductive time (NPT). The average DBR cost per BHA can be as high as USD 1 million. Combined with a complete BHA roundtrip, it can easily cost more than USD 3 million for operators if such failure happens. This has been a problem for several years and has caused significant damage: In 2014, of 15 26-in. PDC bit runs in salt, 40% had overtorque connections and 20% led to DBR. This paper discusses how an integrated multidisciplinary team identified the root cause of and the solution to the overtorque problem. Torsional vibration was believed to be the cause of such failure. Comprehensive drilling dynamics simulation software that is based on empirical bit design knowledge was used to design a new bit to reduce the vibration. A newly developed high frequency downhole recording tool used in the 26-in. section recorded high-frequency torque, acceleration, and RPM fluctuation downhole. This dataset became the key to understanding the downhole vibration in detail because it provided information that cannot be acquired by a traditional MWD tool. Field-recorded data were fed into drilling dynamics simulations to accurately calibrate the drilling dynamics model. The simulations resembled downhole drilling conditions and clearly identified the root cause. The simulations precisely predicted the torque along the entire drillstring and identified why overtorque is present in only a certain part of the drillstring. The calibrated model was used to compare old and new bit designs. The newly designed bit showed much lower torque amplitude with similar torsional vibration frequencies. The simulation indicated that the newly designed bit can significantly alleviate the overtorque issue. Implementation of the new bit mitigated the overtorque issue immediately. As of May 2016, there have been 18 runs with the new bit. Only one run had a slight overtorque issue whereas the rest showed no sign of overtorque connections. DBR and NPT related to overtorque were eliminated. As a byproduct, the average on-bottom rate of penetration increased by 9%. This case demonstrates the effectiveness of the integrated approach to solving drilling challenges.

The drilling industry has substantially improved performance based on knowledge from physics-based, statistical, and empirical models of components and systems. However, most models and source code have been recreated multiple times, which requires significant effort and energy with little additional benefit or step-wise improvements. The authors propose that it is time to form a coalition of industry and academic leaders to support an open source effort for drilling, to encourage the reuse of continuously improving models and coding efforts. The vision for this guiding coalition is to 1) set up a repository for source code, data, benchmarks, and documentation, 2) encourage good coding practices, 3) review and comment on the models and data submitted, 4) test, use and improve the code, 5) propose and collect anonymized real data, 6) attract talent and support to the effort, and 7) mentor those getting started. Those interested to add their time and talent to the cause may publish their results through peer-reviewed literature. Several online meetings are planned to create this coalition, establish a charter, and layout the guiding principles. Multiple support avenues are proposed to sustain the effort such as: annual user group meetings, create a SPE Technical Section, and initiating a Joint Industry Program (JIP). The Open Porous Media Initiative is just one example of how this could be organized and maintained. As a starting point, this paper reviews existing published drilling models and highlights the similarities and differences for commonly used drillstring hydraulics, dynamics, directional, and bit-rock interaction models. The key requirements for re-usability of the models and code are: 1) The model itself must be available as open source, well documented with the objective and expected outcomes, include commented code, and shared in a publicly available repository which can be updated, 2) A user's guide must include how to run the core software, how to extend software capabilities, i.e., plug in new features or elements, 3) Include a "theory" manual to explain the fundamental principles, the base equations, any assumptions, and the known limitations, 4) Data examples and formatting requirements to cover a diversity of drilling operations, and 5) Test cases to benchmark the performance and output of different proposed models. In May 2018 at "The 4th International Colloquium on Non-linear dynamics and control of deep drilling systems," the keynote question was, "Is it time to start using open source models?" The answer is "yes". Modeling the drilling process is done to help drill a round, ledge free hole, without patterns, with minimum vibration, minimum unplanned dog legs, that reaches all geological targets, in one run per section, and in the least time possible. An open source repository for drilling will speed up the rate of learning and automation efforts to achieve this goal throughout the entire well execution workflow, including planning, BHA design, real-time operations, and post well analysis.

The oil and gas industry has become increasingly interested in drilling dynamics and vibration as causes of drilling inefficiency and reduced drilling performance. Generally, drillstring vibration is measured with shock-and-vibration sensors installed in measurement-while-drilling (MWD) tools, logging-while-drilling (LWD) tools, and rotary steerable systems (RSS). Although these tools provide valuable real-time and recorded-mode information on the dynamic conditions, they are not generally designed to capture continuous high-frequency mechanics and dynamics data, and burst data may miss important information about the evolution of the system response and state.A downhole mechanics measurement tool has been developed that makes a comprehensive suite of measurements of the drilling process, including forces, accelerations, rotational speed, pressures, and temperatures. In addition to providing information in real-time, the tool has the capability to capture long durations of continuous data at frequencies between 50 and 2,000 Hz. The recorded-mode information obtained has provided significant insight into the response of the drilling system to initiating rotation; drilling procedures and parameter modifications; and exposure to excitation from sources including, but not limited to, rig heave, bottomhole assembly (BHA) component imbalance, and bit-rock interaction. A wide range of occurrences has been captured in which the drilling system switches from a dominant vibration mode, typically torsional (downhole rotation-velocity oscillations or stick/slip) into a different mode, such as axial (bit bounce) or lateral (whirl). Transitions between different types of whirl have also been recorded.Several cases were studied to investigate the evolution and response of drilling system behavior based on the in-depth interpretation of relatively long durations (minutes to hours) of high-frequency data sets in the operational context. The findings verify the value of using continuous high-frequency vibration data to understand the drilling system and increase drilling performance.