Drilling with Induced Vibrations Improves ROP and Mitigates Stick/Slip in Vertical and Directional Wells

Abstract

For years drillers have been taught to mitigate all vibrations in the drillstring while drilling to maximize Rate of Penetration (ROP), limit bit damage, and extend bit life. While limiting lateral vibrations and stick/slip are proven ways to improve performance and maintain directional control, in recent years it has been conclusively proven in the field that inducing axial agitation with specialized downhole tools can significantly improve lateral reach. Currently, however, the benefits of downhole oscillation tools have not been thoroughly studied for other performance gains, such as improved ROP in non-directional wells.An extensive research study, including lab and field testing, found that a low-frequency, benign axial vibration can increase the ROP significantly in all well types. Initial laboratory experiments were performed by inducing axial vibrations into the drilling process on a small scale drill bit in hard rock. Dramatic improvements in ROP and drilling efficiency were observed, with the added benefits of improved bit life and an unexpected reduction in stick/slip. This lab experiment was later tested in the field by utilizing a proven downhole oscillation tool in an active Bottom Hole Assembly (BHA) to create the effect that was simulated in the lab. The field tests showed the same results as the lab tests: significant performance gains were observed in several test wells using the downhole oscillation tool as compared to offset data. In addition, this same downhole oscillation tool showed drastically improved directional control when run above a Rotary Steerable System (RSS) tool, and stick/slip was practically eliminated with no negative effect on bit life or BHA reliability.High-speed sensor data collected at the bit during both the lab and field tests will further demonstrate the validity of the theory. Testing for a hard-rock application with roller cone bits is forthcoming, as the data indicates possible performance gains in this environment as well.Overall, the study revealed many benefits, such as improving well placement, reducing Non-Productive Time (NPT) and time to Total Depth (TD) by preventing BHA component damage through beneficial axial vibrations from the downhole oscillation tool. The data indicates that "benign vibration" can drastically improve drilling performance. Induced Vibration Theory and Application Background (Forster and Grant, 2012)Theoretically, any drilling assembly which provides a fluctuating axial load application focused downhole will improve drilling efficiency. The axial excitation will improve drilling efficiency by breaking static friction, both in the BHA and at the bit. Once static friction is overcome and stead-state dynamic friction results, the Weight on Bit (WOB) required will be a fraction of the WOB required under normal drilling conditions, and load transfer will improve.

Vibration Technologies for Friction Reduction to Overcome Weight Transfer Challenge in Horizontal Wells Using a Multiscale Friction Model

“…The power section is made up of a positive displacement motor driver. The valve and bearing section is composed of an eccentric orifice, driven by the power section, and matched against a concentric orifice, thus generating a continuous wave of pressure pulse as the rotor turns when the drilled mud is pumped through the system [16]. These pressure pulses travel up into the Shock Tool.…”

New automated drilling controller for drill string vibrations mitigation and rate of penetration optimization using a fuzzy logic system.

“…These complicated phenomena cannot be entirely avoidable due to the unpredictable external forces acting on the drill-string and the Bit-Rock interactions in the bottom hole [5]. However, the use of dynamic analysis and control strategy allows to reduce the vibration related problems [6], to suggest new recommendations for drilling operations [7][8][9], for drill string design [10,11] and for control systems [12][13][14][15][16], which deliver economic benefits through a mix of lower costs and higher production.…”

Experimental study on jet pulse assembly design and numerical simulation

“…Since the 1980s, more and more downhole rotary drilling has been utilized in directional wells due to many advantages, such as increasing the rate of mechanical drilling, increasing the footage of a single drill bit, and achieving well path control. However, the friction between the drill string and the borehole wall is large because of the large inclination angle of the well, which is resulting in low drilling rate (ROP), drilling tool wear and tear, and wellbore instability (Abdo and Al-Sharji 2014;Clausen et al 2014;Martinez et al 2013). In order to enhance the extending ability of directional wells and maximize the productivity of oil reservoirs, the problem of reducing friction torque has become the focus of research in the oil field.…”