The drive for greater drilling speeds increases the dysfunctions encountered downhole. If left unmitigated, those vibrations can increase operating costs and downtime. Successfully suppressing downhole vibrations enables companies to surpass previous speed limitations, without damaging downhole equipment.
GUY FEASEY, Neo Oiltools
The stakes are higher than ever for today’s drilling programs. Time is truly money, and delays are costly in many ways.
The Permian is as prolific as it is challenging—especially in the Delaware basin. With the deepest oil-bearing formations and thickest rock deposits, as well as significant geological complexity and numerous faults and folds among the Permian’s sub-basins, the Delaware requires operators to drill down farther before drilling a lateral curve and horizontal section.
The operating conditions aren’t the only complication that oilfield companies encounter. The factory drilling approach that’s widely used across the region enables companies to drill multiple wells on a single site. While this method helps reduce costs and drilling cycle time, it also puts a premium on efficiency, so the impact of any delays can multiply quickly.
These dynamics underscore the complexity of today’s drilling operations. Operators have a target reservoir, a limited budget and a variety of tools at a drilling engineer's disposal to drill a well as fast and efficiently as possible. Speed is key, as operators pursue longer, faster and deeper wells. However, faster drilling introduces increasingly violent downhole forces that can damage delicate electronics in the bottom hole assembly (BHA) and the cutting structure of the drill bit, Fig 1.
THE DEMAND FOR GREATER SPEED
More demanding well profiles require more transfer of energy to reach the drill bit, which is achieved via advances in motor-assisted rotary steerable systems. Ironically, these innovations can increase drilling tool damage, reduce the rate of penetration (ROP) and cause premature trips out of the hole. The critical interaction between the wellbore and the tools manifests as a waveform, and the amplitude and frequency of these vibrations are key performance indicators. Minimizing these damaging axial, lateral and torsional vibrations—including High Frequency Torsional Oscillations (HFTO) and Low Frequency Torsional Oscillation, also known as stick-slip—is paramount to drilling faster while protecting downhole equipment.
Interrupting these bit-rock interaction-induced harmonic oscillations before they reach a damaging resonance frequency has perplexed operators for more than a decade. Different approaches have emerged that focus on a singular type of vibration, from a simple shock sub for axial dysfunctions to non-rotating drill pipe centralizers, elastomers or even electronic algorithms in the top drive, to reduce lateral vibrations.
One approach targeting HFTO uses an internal counterforce mechanism that interrupts the wave form. However, this takes away energy that could otherwise be better used at the drill bit. This approach only addresses a symptom of the vibrations; it doesn’t correct the creation of the HFTO vibration that occurs at the drill bit during interaction with the rockface.
Other vibration suppression tools have depth of cut management, such as an internal spline mechanism, to attempt to manage torsional vibration. The need to overcome internal friction to induce rotation reduces this type of tool’s ability to respond effectively to torsional vibrations. Spline tools are also limited in the ability to manage or minimize axial shocks or HFTO.
In contrast, a spring and cable design mechanism is field-proven to minimize all types of vibrations that can be encountered downhole. This provides a unique responsiveness when a new formation is encountered – upon sensing a torque change at the drill bit, the cables slide and rotate around the mandrel and return energy to the drill bit. This enables the cable design tool to reduce all forms of tangential oscillations, from low (5Hz) to high (450Hz) frequencies, as well as sudden axial and lateral shocks and vibrations.
CABLE DESIGN TOOL INCREASES ROP 30% IN THE PERMIAN
An operator in the Permian experienced the comprehensive vibration suppression effects of Neotork’s spring and cable design tool. On a five-well pad, each well targeted the same formation and exhibited identical well profiles: a vertical-curve-lateral section 17,500 ft long, with a 15°/100-ft dog leg severity (DLS) curve. The BHAs in the first three wells on the pad were equipped with a vibration suppression tool that addressed HFTO only, and the last two wells utilized a spring and cable design vibration suppression tool, Fig. 2.
Only the spring and cable design tool effectively minimized vibrations induced downhole, including stick slip, HFTO and axial and lateral dysfunctions. Most importantly, the spring and cable design tool also increased rate-of-penetration (ROP) by 30% and enabled the operator to drill the two wells up to 1.5 days faster.
PUSHING DRILLING BOUNDARIES FURTHER
As operators continuously seek to drill faster, it’s imperative to address and reduce all types of vibrations downhole. The ability to minimize any vibration encountered not only pushes the founder point higher to attain new technical limits, but it also helps to control costs, as downhole tool damage is decreased.
Mitigating all vibrations that can be encountered helps operators surpass established drilling program speeds and reimagine operations, Fig 3. WO
REFERENCES
Parimal Arjun Patil and Oscar Nicolas Ochoa, Baker Hughes_IADC/SPE-199680-MS2020
Ashley Johnson, Sameer Bhoite, David Long and Chris Reagan, SLB_IADC/SPE-208720-MS
GUY FEASEY is Neo Oiltools’ North America regional manager. He brings more than 25 years of oil and gas experience to this role. Through his role, he helps U.S. drilling companies effectively manage downhole torque and reduce drilling dysfunctions.