Identification of Optimal Drilling Parameters for Reduction of High-Frequency Torsional Oscillations by Combined Approach with Modeling and Real-Time Analysis of High-Frequency Measurements

Abstract

Maximizing drilling performance by pushing the limits of drilling tools is the key to reduce overall drilling cost. The interplay of complex parameters such as lithology, drilling parameters, drilling experience, downhole tool reliability, and the operational process help us to identify the limiting factors. Drilling dysfunction could deteriorate the reliability of downhole drilling tools including the overall drilling performance by causing damaged bits, failure of downhole electronic components, torsional fatigue of drillstring, over-torqued connections, etc. Precise modeling of dynamic responses of a bottomhole assembly in a given formation can help to identify operating limitations as well as post job analysis. The wellbore-drillstring interaction and well face-drill bit interaction are the sources of excitation of torsional oscillations. Stick-slip is one of the common and well-known torsional oscillation that usually occurs at low frequencies <1 Hz. High-frequency torsional oscillations (HFTO) are also recorded in the field by using high-bandwidth downhole vibration monitoring tools. HFTO occurs at much higher frequencies; >10Hz to 500 Hz. This paper summarizes the HFTO phenomenon that causes high tangential accelerations and torsional loads within the bottomhole assembly (BHA) during drilling in critical formations. HFTO modeling that is validated with high-speed measurements helps to identify tangential accelerations and torsional loads across the BHA components. This paper highlights the benefits of modeling the rotary steerable system (RSS) BHA for HFTO in order to identify the point in the BHA that is subjected to the highest tangential acceleration and torsional loads. Real time monitoring for drilling optimization of RSS BHA shows that the HFTO modeling and post-job data analysis of high-frequency data confirms the distribution of tangential acceleration and torsional loads along the BHA. The paper also highlights the accuracy of the HFTO modeling based on results of pre-job modeling and post-job high-speed data analysis from drilling runs. Based on the analysis and the study, recommendations for optimal BHA design and operational parameters are provided to yield maximum footage per run and improved BHA performance. High-frequency torsional oscillations in the BHA can be mitigated if adequate BHA design, drilling parameters, and procedures are implemented. The in-depth analysis of HFTO with accurate modeling and high-frequency measurements can be used to develop a knowledge base to further optimize the drilling process, reduce non-productive time, realize fewer trips for failures, extend the on-bottom drilling time, reduce maintenance costs, and increase the drilling efficiency and performance.

A Review of the Research and Development of High‐Frequency Measurement Technologies Used for Nonlinear Dynamics of Drillstring

“…Since highfrequency measurements used investigate BHA behavior, HFTO has become a topic gaining great attention in recent years due to the damage it causes to lower BHA components. Typical key indicators during failure investigation showing Shock and Vibration that HFTO had occurred in a BHA while drilling are cracks on tool, loose electronics within the tool, squeezed cables, sheared bolts, and vibration dust as shown in Figure 14 [61].…”

“…Actually, HFTO is not limited to RSS and may occur with any other BHA with or without motor in harder and denser formations all over the world [41]. Factors causing BHA to resonate in torsional direction mainly are (a) bit-rock interaction, (b) drilling parameters at the bit, (c) torsional stiffness of the BHA, (d) formation density, and (e) BHA design [61,63].…”

“…Figure 15 shows a 5-second burst data that captured the transition from low state to severe state of HFTO, and this sudden appearance of vibration mode suggests that it is driven by formation and/or operating environment changes but not the result of gradual dulling of bits. A prejob model for a BHA is created by Patil and Ochoa [61] and presumed that the HFTO will occur drilling preidentified formations, and those formations are relatively hard (typically the bulk density is >2.5 g/cc). It has been observed from the downhole memory data recorded by the tools while drilling that severity of the tangential vibration increases when the bit drills through transition zone from the softer porous rock to harder denser one and vice versa.…”

“…rough data collected from the DDS in RSS and motorized RSS (MRSS) BHA runs, the relationship between the drilling parameters (WOB and RPM) and the tangential vibration was plotted by Patil and Ochoa [61], as shown in Figure 18. High tangential accelerations are recorded as the WOB increases and also has liner relationship with RPM, and it could be concluded that these are primordial parameters for this drilling dysfunction triggered by HFTO.…”

“…Actually, the simultaneous LFTO and HFTO could interact with each other. Patil and Ochoa [61] put out a chapter of high-speed data from the tool's memory (Figure 23), and the left graph shows continuous HFTO while the right picture shows stickslip superimposed on HFTO.…”