A startup company in Canada is developing a tool that may help operators realize savings in resources and manpower in their fracturing operations. The PSI-CLONE tool from RocketFrac Services uses a proprietary solid rocket fuel mixture as a propellant fracturing mechanism which eliminates the need for significant water volumes. When loaded into the tool, deployed down a well, and ignited, the propellant releases high-pressure gas and creates enough pressure to produce fractures at targeted sites along the wellbore.
The PSI-Clone tool can be reloaded with additional blocks of solid rocket fuel propellant. Source: RocketFrac Services.
The PSI-CLONE tool, which holds the propellant, is reusable. Once the propellant has burned out completely, the tool can be reloaded with another block of fuel. The company states that the system requires a single coiled tubing unit, as opposed to the multiple pumper trucks and water tanks used for hydraulic fracturing, and requires three to five onsite personnel.
The ability of propellant fracturing to rapidly generate high pressures allows for tailorability, which is not available with hydraulic fracturing because of the physical limits on the water pumping rate.
Propellant fracturing can be designed to anticipate the
existing stress field and produce the desired fracture pattern.
Source: RocketFrac Services.
Propellant fracturing is not a new concept. Sandia National Laboratories began researching the topic in the 1980s, and more than 600 wells have been stimulated using some variation of this technology. Annelise Freeman, CEO of RocketFrac, said that the main difference between PSI-CLONE and other propellant fracturing methods is the burn time of the fuel and the presence of elements that allow for sealing the wellbore against the pressure generated by the solid propellant. Current technology cannot confine the rapid pressure rise rates generated by propellant fracturing within a target zone for treatment durations of more than 300 to 500 milliseconds.
Freeman said the PSI-CLONE technology’s ability to isolate a selected target zone and prevent gas from escaping along the wellbore allows for greater penetration into the formation and extended fracture growth. According to RocketFrac, a pressure event duration may last between 1 and 20 seconds at 20,000 psi and produce four to eight radial fractures. Tools can also be strung together to simultaneously treat multiple zones.
“Traditional propellant fracturing has been off-the-shelf propellant that you can purchase, hang down the well on a wireline, ignite, and it would get some really great results with no casing damage. What it did not have was the ability to seal which is critical to sustain longer burn times, and when we’re talking about long lateral horizontals, inadequate sealing allows the gas to escape along the wellbore. What this means is you don’t put as much pressure on the formation, so you don’t create the long fractures required,” Freeman said.
Because it does not use any liquid beyond the drilling fluid on-site, Freeman said PSI-CLONE would eliminate the need for facilities and vehicles for water treatment and disposal. She said solid rocket propellant is stable, safe to handle, and easier to transport than flowback water. With no size or lateral restrictions in borehole length, the tool would be small enough to be transported in a single truck, and because it does not require water or proppant, the system does not require much time for assembly.
“You could actually put this rocket fuel in the back of your car and put it on the road,” Freeman said. “It won’t go off without an ignition force. It is absolutely benign. As a solid, if you drop it, you can just pick it up. I’ve handled it with my bare hands. It is very, very safe.”
RocketFrac is still in the early stages of development. The company incorporated in February and is currently looking to test both the sealing mechanism and the solid rocket fuel to see how it performs in different formations. It is currently working with a rocket fuel manufacturer to design and supply a formulation customized for the petroleum industry. Freeman said the company is looking to use PSI-CLONE in test wells by January or February 2018.
Stephen Whitfield, Senior Staff Writer | 26 September 2017