Particle drilling technology
A new drilling technology system is being tested that is expected to improve drilling penetration rate (ROP) in certain hard rock or tough drilling environments.
According to Chris Boswell with Particle Drilling Technologies Inc. (PDTI), “The Particle Impact Drilling (PID) system was patented in 2002 and is nearing the completion of a five year development phase.”
The PID System uses a specially designed bit fitted with a Polycrystalline Diamond Compact (PDC) cutting structures and novel nozzles. The nozzles serve to accelerate spherical steel shot entrained in ordinary drilling mud to excavate the formation.
As described by Chris and Tom Hardisty of PDTI, the steel shot impacts, fractures, and removes most of the formation ahead of the bit, which frees the bit to travel through the formation at an increased rate of penetration as compared with rates registered when drilling with roller cone bit technology, currently the preferred economical method to drill these slow drilling formations.
This granite rock sample with compressive strength of 36,000 psi was drilled using the PID application at TerraTek Drilling Laboratory.
The bottom hole particle delivery system is designed such that the steel particles impact the formation with a level of force beyond its fracture or plastic deformation point, and in such huge numbers (greater than 4 million impacts per minute based on introducing 12 gal/min of shot) that hard rock formations are rapidly excavated. The steel shot then flows back up the wellbore annulus along with the drilling fluid and formation cuttings to the surface where the system separates the cuttings and shot without the use of desilters or centrifuges and re-circulates the shot as part of a closed loop system.
The PID drill bit
The development of the fit-for-purpose drill bit is ongoing. The current development bit is an 8.5-in. diameter fixed-cutter design (as opposed to roller cone) with a PDC cutting structure and four conventional diameter nozzles. Previous three-nozzle bits were tested in hard and ultra hard rocks at TerraTek in 2002 and early 2003, and demonstrated rates of penetration that were believed to be two to four times faster than observed in drilling like formations with conventional methods. Based on these previous tests, cutter durability was determined to be the primary technology needing improvement.
The new four-nozzle bit is expected to handle additional mud/shot volume from 600 up to 850 gal/min, which should directly translate into increased drilling speed. Modifications to the bit body and significant improvements in cutting structure are expected to drastically improve durability.
Particle recovery system
The PID system used a mobile, compact, circulation delivery and recovery system that operates with conventional drilling rigs. The system is designed to entrain, circulate, and recover the steel shot without allowing the shot to pass through the rig pumps. Previous particle abrasive drilling systems did not have the ability to circulate, separate, and re-circulate the abrasive or abrading particles and the material passed through the normal rig pumps. Fine cuttings not removed from the mud and abrasive particulate being pumped through the pumps creates severe wear and mud maintenance, which can spell economic disaster in drilling applications, an example of such a system known as “Abrasive-Jet Drilling” used by Gulf Research and Development Co., a division of Gulf Oil Corp., in the 1960s and 1970s was not successful even though penetration rates were improved by a factor of five versus comparable rates. Basically, the Gulf system used fine particle abrasives to scrape, scour, gouge, or abrade the formations to remove it and required very high surface pressures up to 11,000 psi to give the small particulate the necessary velocity to abrade the formation ahead of the drill bit.
Much of the PID surface equipment are components already used in the field today. Other PID equipment includes specially designed components, piping, instrumentation, controls, and monitoring devices that are designed to set-up and operate with most conventional rigs used today. The system can be deployed and integrated on a rig in only a few hours, typically in less time than it takes to replace the conventional drill bit during a trip. The system can be operated with very little interference with normal rig operations, and can be turned off on “stand-by” in the event conventional methods are desired for drilling certain intervals.
PID system tests
Components of the PID system have previously been tested in actual downhole field conditions at the US Federal Government’s Rocky Mountain Oilfield Testing Center (RMOTC); in the laboratory at TerraTek Drilling Labs, an independent research and testing facility in Salt Lake City; and in multiple shop tests. This testing has demonstrated utility of the PID surface equipment and bit with various levels of success and improvement. In particular, the TerraTek tests have shown the PID bit is capable of increased ROP in hard rock conditions associated with limestone, sandstone, granite, and similar hard formations at rates multiple times faster than current conventional methods. Additional tests at TerraTek have been scheduled to evaluate the new four-nozzle PID bit. The company also is planning to operate the entire PID system later this year at the Gas Technology Institute’s (GTI) Catoosa facility near Tulsa, Oklahoma, to more fully demonstrate the system’s feasibility for commercial use. At Catoosa, the system will be tested in notoriously hard and tough limestone formations and possibly the granite basement rock.
The PID benefits are expected to be achieved through a number of factors unique to the system, including faster formation excavation, lower weight-on-bit, and torque requirements resulting in fewer bit deviations, less drill string vibration and bit wear, and longer footage runs resulting in overall increase in drilling speed. The PID system value will be generated from step-change improvement in drilling curves in certain hard-rock drilling situations, whereby operators will pay less variable drilling costs in those areas. The company’s ultimate goal is to dramatically improve finding cost and overall drilling economics for the energy industry in many basins around the world.
This looks to be a very interesting technology if PDTI can complete the development and get the system to operate reliably following its planned testing phase. While the company currently envisions a customer base that is largely related to onshore wells, one should expect with these types of potential savings onshore, it won’t be long before the industry drags this technology into the offshore market. Once the onshore testing and acceptance is complete, watch out offshore!
