Abrasive Jetting
Abrasive jetting is a wellbore treatment in which a high-velocity slurry of fluid mixed with hard solid particles (typically sand, steel shot, or silicon carbide grit) is pumped through a nozzle and directed against the casing wall, cement sheath, or formation rock to mechanically cut or perforate by erosion. The kinetic energy of the abrasive particles impacting the target surface removes material through erosion, creating slots, perforations, notches, or cuts depending on the tool geometry and pump rate. Abrasive jetting is used for casing cutting (severing a casing string downhole so it can be recovered or removed), perforation (creating holes through casing and cement into the formation), removal of scale or cement deposits inside casing, and hydraulic fracture initiation point control in horizontal wells where precisely placed notches guide fracture initiation rather than allowing it to occur at random locations.
Key Takeaways
- Abrasive casing cutters are used when mechanical cutters cannot penetrate the casing material due to extreme hardness, stuck tools, or complex geometry. The abrasive cutter circulates a sand-laden slurry through jetting nozzles directed radially against the inside of the casing wall. At flow rates of 4 to 8 litres per second with sand concentrations of 60 to 120 kilograms per cubic metre, the slurry can cut through standard K-55 or L-80 casing string in 4 to 10 hours depending on wall thickness. Abrasive cutting leaves a cleaner, more uniform cut than explosive cutters and does not damage the formation or adjacent casing strings as explosive cutting can. The cut casing section is then retrieved to surface using an overshot or spear fishing tool.
- In hydraulic fracturing, abrasive jetting is used to create oriented notches at selected intervals in horizontal wells before fracturing. A coiled tubing (CT) tool with radially directed jetting nozzles is positioned at the desired fracture initiation point. Pumping abrasive slurry through the nozzles erodes a circumferential notch in the formation or near-wellbore rock. The notch acts as a stress concentrator that guides the subsequent hydraulic fracture to initiate from the notched location rather than the weakest point in the wellbore wall. This technique is used to precisely space fracture stages and avoid fractures initiating at undesired locations (such as natural fractures or perforation clusters that are too close together).
- Abrasive jetting perforating uses a downhole jetting tool in place of conventional shaped-charge perforating guns. The tool is positioned at the target depth and abrasive slurry is pumped through jetting nozzles that are oriented perpendicular to the wellbore axis. The slots cut by jetting typically have different geometry from shaped-charge perforations: longer (up to 60 centimetres versus 15 to 20 centimetres for charges) but more rectangular in cross-section and with a cleaner entry hole geometry. Jetting perforations are sometimes preferred over shaped-charge perforations in sensitive formations where the shock of explosive perforation could damage near-wellbore rock or in wells with sour gas where explosive charges have reliability limitations.
- The abrasive material used in jetting operations must balance hardness (to erode the target) against its effect on the downhole tool and surface pump. Silica sand (quartz, Mohs hardness 7) is the most common abrasive because it is hard enough to cut most casing materials and is inexpensive and widely available. Silicon carbide (Mohs 9) is used for very hard targets (high-strength alloy casing or tungsten carbide components). Steel shot is used where contamination of the borehole fluid with silica fines must be minimized. All abrasive materials increase pump wear and surface equipment wear, so nozzle and pump liner inspection is mandatory after any jetting operation.
- Coiled tubing is the preferred delivery method for abrasive jetting because it allows precise depth control and real-time depth monitoring, can be used in live wells without killing the well (maintaining wellbore pressure), and the continuous tube design avoids the complex connection operations of jointed pipe in an active wellbore. The coiled tubing carries the abrasive slurry from the surface mixing system to the downhole nozzle tool. Maximum pump rate is limited by the internal diameter of the coil (typically 38 to 51 millimetres / 1.5 to 2 inches), which limits the flow rate and therefore the jetting energy available compared to a jointed pipe system.
How Abrasive Jetting Works
The basic physics of abrasive jetting is the same as sandblasting: high-velocity particles strike a surface and physically remove material by impact and erosion. The key parameters are particle velocity (controlled by pump pressure and nozzle geometry), particle hardness and shape (angular particles are more aggressive than rounded ones), particle concentration in the carrier fluid, and exposure time (how long the jetting is maintained at a given location).
At the surface, a high-pressure pump drives the abrasive slurry through the coiled tubing or jointed pipe string. As the slurry exits the jetting nozzle at the bottom of the string, it accelerates through the restricted nozzle orifice (typically 6 to 12 millimetres diameter) and strikes the target at velocities of 30 to 80 metres per second. The kinetic energy of the particles erodes the metal or rock surface faster than the fluid alone could by hydraulic force.
After striking the target, the spent slurry and eroded material (metal shavings, rock fragments, spent sand particles) flow back up the wellbore annulus to the surface, where they are caught by the shale shaker and disposal system. Maintaining a clean annulus return is critical: if the return path plugs with jetting debris, circulation is lost and the job must be stopped.
Fast Facts
Abrasive jetting in oil and gas wells was developed in the 1940s and 1950s as an alternative to shaped-charge perforation in wells where explosive tools were unreliable or unsafe. The technique gained renewed interest in the 2000s and 2010s as multistage horizontal well fracturing became widespread in tight formations. Canadian operators in the Montney and Duvernay plays experimented with abrasive jetting to create precise fracture initiation notches in the horizontal sections of long laterals, where controlling the spacing and initiation point of each fracture stage is critical to achieving even stimulation along the wellbore. Service companies including BJ Services (now Baker Hughes), Calfrac Well Services, and CARBO Ceramics developed specialized jetting tools for this application. Coil-jetting combined with simultaneous hydraulic fracturing (the "jetting and fracturing" technique) has been applied in several Montney wells in northeast British Columbia to allow fracture placement without requiring plug-and-perf systems.
Synonyms and Related Terminology
Abrasive jetting is also called sand jetting, hydro-abrasive cutting, abrasive slurry jetting, or jetting perforating (when used specifically for perforation). Related terms include coiled tubing (a continuous steel tubing string stored on a reel and run into the wellbore without connections; the preferred conveyance method for abrasive jetting tools in live wells because it provides precise depth control and continuous circulation), casing cutter (a downhole tool used to sever a casing string so it can be retrieved; abrasive jetting is an alternative to mechanical and explosive casing cutters in situations where mechanical cutting is not possible), hydraulic fracturing (the injection of fluid at high pressure to create fractures in a formation; abrasive jetting creates oriented notches that guide fracture initiation to desired locations and control fracture geometry in horizontal wells), perforating (the creation of holes through casing and cement into the formation to establish a flow path between the reservoir and the wellbore; abrasive jetting is an alternative perforation method to shaped-charge guns, producing longer slots with less near-wellbore damage), and scale (mineral deposits that form in wellbores and surface equipment from produced water; abrasive jetting is occasionally used to remove hard scale from inside casing where mechanical cleaning and chemical treatments have been ineffective).
How Abrasive Jetting Salvaged a Stuck Casing Recovery in a Montney Well in Northeast BC
A Montney horizontal well in the Groundbirch area of northeast British Columbia required abandonment after the production tubing became irreversibly stuck due to scale buildup and corrosion. The operator's plan called for recovering the production tubing string and cutting the casing at 1,200 metres measured depth so the upper casing section could be retrieved, leaving only the lower section to be cemented in place as part of the abandonment program. The casing was P-110 grade (high-strength alloy steel), with a wall thickness of 9.2 millimetres.
A mechanical casing cutter was run to 1,200 metres but failed to cut through the P-110 casing after three attempts, damaging its blades each time. The explosive casing cutter was rejected by the operator's safety team because the well was not fully de-gassed and there was a residual gas cap risk that made explosive tools unacceptable for this location. An abrasive jetting crew was mobilized with a coiled tubing unit.
The abrasive cutter was run to 1,200 metres on 44-millimetre coiled tubing. Silicon carbide abrasive at 80 kilograms per cubic metre concentration was pumped at 5 litres per second at a surface pressure of 18 megapascals for 6 hours. A circumferential cut was confirmed by rotating the jetting nozzle 360 degrees during the job. When the coil was pulled and a wireline jar was run to test casing movement, the upper casing string moved freely. The upper casing section was recovered, and the abandonment program proceeded as planned.
The abrasive jetting job cost CAD 95,000 in service company charges plus CAD 35,000 in coiled tubing rig time. The alternative of re-designing the abandonment plan to leave the upper casing in place (which would have required additional cement plugs and extended regulatory review) was estimated at CAD 180,000 in additional well costs plus a 6-week schedule delay. The abrasive jetting approach saved both time and money while satisfying the AER abandonment requirements for casing retrieval.