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The shale sector is making moves to consolidate amid investor pressure to increase cash flow. This deal will form the second-largest producer in Colorado’s DJ Basin. PDC’s president and CEO describes the company’s management strategy for its hydraulic fracturing operations in the Wattenberg Field and the Delaware Basin. Baker Hughes is developing a drill bit capable of auto-adjusting its depth-of-cut feature to handle dynamic drilling conditions. Drilling the Severnaya Truba field in Aktobe, Kazakhstan, has been costly and time consuming.
The court said it was mindful of the disruption the shutdown will cause but said the seriousness of deficiencies from the US Army Corps of Engineers outweighs the negative effects of shutting down the pipeline. In 2 months, the US saw a 56% decline in rig count, reaching a 33-year low. Multistage horizontal well designs were first implemented in the Bakken in 2007. Since then, more than 12,000 wells have been completed in either the Middle Bakken or Three Forks zones. Most of ConocoPhillips’ oil and gas production by the end of the next decade will come from its unconventional operations.
In 2 months, the US saw a 56% decline in rig count, reaching a 33-year low. Multistage horizontal well designs were first implemented in the Bakken in 2007. Since then, more than 12,000 wells have been completed in either the Middle Bakken or Three Forks zones. Most of ConocoPhillips’ oil and gas production by the end of the next decade will come from its unconventional operations. But, for the near-term, the Houston independent will rely on conventional assets as it seeks to keep spending in check, decline rates low, and cash flow on the rise.
Summary In this paper, we provide some new insights into stick/slip vibration in drilling with polycrystalline diamond compact (PDC) bits. Fiftysix field runs under various drilling conditions were collected with the help of on-bit vibration sensors. Two types of stick/slip vibrations were identified: cutting-action-induced stick/slip and friction-induced stick/slip. Methods were developed to determine whether a stick/slip occurrence is induced by cutting action or by friction. Statistical analysis found that bit drilling efficiency (DE) is well correlated with the occurrence of cutting-action-induced bit stick/slip vibration. If a PDC bit is designed so that its DE is greater than a critical value, then the cutting-action-induced bit stick/slip vibration is not expected in drilling. Introduction Stick/slip vibration in drilling is one of the primary causes of cutter damage of PDC bits and early failures of downhole tools (Ledgerwood et al. 2013). Early efforts to address this issue were to measure downhole stick/slip by instrumenting vibration sensors near the PDC bits (Lamine et al. 1998) and near the roller cone bits (Chen et al. 2002). After the occurrence of stick/slip vibration in drilling is confirmed, efforts have been focused on understanding the root cause of stick/slip vibration of a PDC bit and the mitigation of stick/slip vibration during drilling. To better understand the root cause of stick/slip vibration of a PDC bit, three assumptions have been developed in the past three decades.
Stick-slip is a torsional vibration mode observed in drilling systems, which are used in creating boreholes for the exploration and production of oil and natural gas. This paper presents a method to create and assess stick-slip in the laboratory environment. This is achieved by using the hardware-in-the-loop method, where a numerical drillstring model is combined with an experimental drilling machine. In this setup, the numerical model captures the axial and torsional oscillations between the surface and the drill bit, while the drilling machine acts as the hardware in the loop, capturing the actual bit-rock interaction. The proposed framework allows creating self-excited stick-slip oscillations in a controlled, repeatable and measurable manner. This enables reducing the risk, cost, and time for activities related to testing, developing, debugging or optimizing any stick-slip related tool or mitigation concept.
Rolling depth-of-cut control (RDOCC) on fixed cutter drill bits can improve rate of penetration (ROP) and reduce vibrations during steerable motor applications by reducing torque fluctuations caused by sliding friction. Torque fluctuations are reduced by absorbing weight-on-bit (WOB) variations using a rolling bearing element, without generating additional torque that leads to tool-face control issues.
Laboratory testing validated RDOCC efficiency compared to traditional depth-of-cut control limiters (DOCLs) by evaluating frictional force, load, and material resistance to axial and lateral forces. At the field level, potential applications, where tool-face control was identified as a drilling performance limiter, were analyzed and selected for the initial field tests. Baseline performance and target depth of cut (DOC) were determined using foot-based data. Additional drilling parameters, such as WOB, torque, and vibration, were analyzed to measure the RDOCC influence on drilling performance. The vibration data were recorded using an at-bit data collection device (ABDCD) and later compared to data from bits with traditional DOCLs. Modified bit designs that included RDOCC with rolling elements on three blades to engage at the target DOC were run in the selected applications and results compared to historical data, performance, and dull bit condition.
In southeastern Saskatchewan, Canada, the curve section of Bakken wells experienced overall ROP improvement and reduced vibrations at the bit, as indicated by improved dull condition and ABDCD data. Five consecutive field record runs were achieved using bits equipped with RDOCC technology. In McKenzie County, North Dakota, USA, direct comparisons between polycrystalline diamond compact (PDC) bits with RDOCC and those with traditional DOCLs show a 39.5% reduction in hours or better to drill the curve section from 10,300 to 11,100 ft measured depth (MD) on the same pad site. The improved tool-face control allowed higher WOB application from a lower inclination through landing the curve, thereby improving ROP throughout the run. In the Wadi Rafash Field, northern Oman, a PDC bit with RDOCC drilled the curve section, improving dogleg severity (DLS) by 45%, ROP by 23% and reducing distance by 30% over the average offset performance in the field.
The novelty of the RDOCC is the ability to absorb WOB fluctuations without creating large torque fluctuations that inhibit tool-face control. By maintaining a consistent tool face, operators and directional drillers can apply more energy to the system, resulting in overall higher ROP.
This paper provides some new insights into stick-slip vibration in drilling with polycrystalline diamond compact (PDC) bits. Fifty-six field runs under various drilling conditions were collected with the help of onbit vibration sensors. Stick-slip vibration occurrence during drilling was analyzed. Two types of stick-slip vibrations were identified: cutting action-induced stick-slip and friction-induced stick-slip. Methods were developed to determine whether a stick-slip occurrence is induced by cutting action or by friction. Statistical analysis found that bit drilling efficiency is well correlated with the occurrence of cutting action-induced bit stick-slip vibration. If a PDC bit is designed so that its drilling efficiency is greater than a critical value, then the cutting action-induced bit stick-slip vibration is not expected in drilling. Increasing the aggressiveness of the cutting structure of a PDC bit within a limited critical depth of cut is found to be helpful to mitigate bit stick-slip vibration.
Shen, Yuelin (Schlumberger) | Chen, Wei (Schlumberger) | Zhang, Zhengxin (Schlumberger) | Bowler, Adam (Schlumberger) | Jeffryes, Benjamin (Schlumberger) | Chen, Zhenyu (Schlumberger) | Carrasquilla, Maria Neves (Schlumberger) | Smith, David (Schlumberger) | Skoff, Greg (Schlumberger) | Panayirci, Huseyin Murat (Schlumberger) | Arevalo, Yezid (Schlumberger) | Bolchover, Paul (Schlumberger)
In recent years, the phenomenon of drill string torsional oscillation at frequencies over 50 Hz has been well documented. This high frequency torsional oscillation (HFTO) creates cyclic fatigue loading on bits and drilling tools within the bottom hole assembly (BHA) and thus limits tool life and drilling performance. However, few models exist which can predict occurrence of HFTO and its severity. To our knowledge; none of these models consider the entire drilling system including the bit-rock interaction, downhole drive(s), BHA design, and surface drilling parameters, and hence there is a need to develop a system model for HFTO mitigation.
A 3D transient drilling dynamics model has been extended to study the severity of HFTO and cyclical loading to drilling tools. The accuracy of the model was validated by theoretical calculation, and high frequency downhole data. An example analysis was conducted to evaluate drilling system design performance in terms of HFTO risks. Good correlation was found between the analysis and field data collected from the Permian Basin.
Advanced models were developed for mud motors and rotary steerable system (RSS) tools. After conducting a full drilling simulation, the drilling system behavior under HFTO can be fully described. Cyclical torque loading of differing magnitudes and frequencies were observed for different BHA components depending on HFTO vibration mode, HFTO severity and BHA design. PDC cutters were subjected to different cyclical loading depending on bit design, formation and HFTO conditions. The mud motor power section was found to undergo high frequency cyclical loading which could accelerate its rubber degradation. Since the failure of PDC cutters and the degradation of mud motor power sections have a critical effect on drilling performance, the importance of mitigating HFTO cannot be underestimated. By evaluating the loading conditions, an optimized drilling system can be selected. Field data has proved the validity of this approach.
The methodology presented in this paper offers a new way for the industry to systematically mitigate HFTO by considering the rock drilled, bit design, mud motor utilized, the mechanics of RSS and other tools in the BHA, as well as drilling parameters. The usage of this approach can reduce premature drilling component failure and improve drilling performance, especially in the high energy drilling applications found in North America Land and other areas.
Robustness of round and v-shaped polycrystalline diamond compact (PDC) cutters against mechanical and thermal load was evaluated. Forensic analysis was used to estimate the range of loads and depths-of-cut (DOC) that cause structural overload of PDC cutters. Finite element analyses (FEA) were calibrated against this data and used to estimate the integrity of cutters. Thermal-abrasive wear was tested with single cutter tests on Sierra White granite with and without cooling for multiple material grades. The axial and tangential impact resistance were evaluated with drop and front face impact tests. In addition, full-scale lab drilling tests were conducted in granite (UCS=28,000 psi) and quartzite (UCS=56,000 psi). Finally, failures for round and v-shaped cutters were evaluated in field trials.
The v-shaped cutters scored similar to baseline cutters in thermal-abrasive tests, but lower in axial impact tests. They also failed at 13-18% lesser tangential load. By accounting for 16% reduction in contact area between the shaped cutter and load anvil, it was concluded that both cutter geometries fail essentially at the same stress. In all full-scale tests, round cutters failed before the shaped cutters. This was in contrast with drop tests and is attributed to the shaped cutter's cutting efficiency, resulting in lesser load on the cutters for the same ROP. The results were then compared with field runs in hard and interbedded application in Oklahoma and West Texas. The conclusion based on FEA, lab, and field data was that in a majority of the cases, this shaped cutter shows the same or better dull as its base grade.