What is Radial Jet Drilling (RJD)?
It’s an enhanced oil recovery (EOR) method that can be used on existing wells to stimulate further extraction. It involves sending an ultra-high-pressure cutting spray into the wellbore to cut through the formation.
The technique has been around for over 20 years and is often presented as a greener alternative to hydraulic fracturing. The fluid used can include water, acidized water, and diesel, this would be determined by the geology that is being drilled.
A high-pressure pumping system is used that can produce up to 18,000 PSI, is combined with a specialist nozzle that drills forward. The nozzle also jets backwards to push back, or ‘accelerate’ the cuttings into the main bore.
As well as being an enhancement, it can be used as a stand-alone drilling technique, depending on the geology of the formation.
Sometimes a regular vertical well is producing substandard production, and radial jet drilling will be considered in order to further stimulate the well. The technique is also suited to lateral wells, with each new drilling lateral extending up to 100 meters.
This well-made animation shows how the process works:
Marginal and Mature Fields…
… Have been the main usage target of radial jet drilling. RJD makes sense on marginal fields as it’s a low-cost solution that is easy to perform, and can cut through to sweet spots of additional reservoir deposits. In the case of mature fields it can bypass damaged sections of a wellbore, that would be hard or impossible to drill again.
As well as being an alternative to fracturing, it can be used in conjunction with fracking, to deliver the frac fluids to create an extra boost to the technique. It’s also suggested in carbonate formations, where acid (usually hydrochloric) can be added to the fluid to increase the impact of the radial penetration.
A typical Application
Coiled tubing can be used to create a 90-degree bend in 4- 4.5″ casing then jet through the wall into the formation. The coiled tubing can be pulled back and used to create another penetration at another 90-degrees. This can be done 4 times and at a penetration depth of 100 meters or more. Then, this 4-way jet drilling can be repeated at intervals of a meter all the way along the bore. Additional reservoir sweet spots, as well as trapped oil, can filter back through to the well.
Benefits of jet drilling include:
- Environmentally friendly
- Inexpensive compared to alternatives
- Works in new and old wells
- Easy to deploy
- Works for many different geological formations
- Used for vertical or horizontal drilling
- Works in damaged wells not suitable for workovers or re-completions
Jet Drilling Controversy
After being around for 2 decades, there are some that doubt the cost-effectiveness of the technique. Considering the low cost, environmentally friendly aspects of RJD, you’d expect it to be used more often.
There are some challenges and limitations with the technique. The high-pressure jet is likely to follow the path of least resistance, meaning an increased chance of hitting a water zone. The cementing at the kick-off point needs to be perfect, and it’s nearly always recommended in carbonate reservoirs.
Jet drills are able to cut through hard sandstone, limestone, and dolomite, and the technique is practical in the Marcellus, Barnet and Austin chalk formations. There are plenty of examples where jet drilling has increased production. The question is, why isn’t radial jet drilling used in all situations where it makes sense? Surely there must be some actionable long-term statistics in by now?
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