Coiled Tubing

A method from the oilpatch can help with well rehabilitation projects.

By Edd Schofield

As the McEllhiney guest lecturer for the National Ground Water Association in 2007, I spoke on my shared experience from a previous life as a completion engineer for Hughes Tool completion group.

I had been asked to share experiences from my earlier work as a designer of well completions and well rehabilitation efforts in the oilpatch. I did so, and the name of my talk was “Oil and Water—They Really Should Mix.”

Use of coiled tubing has been a part of the oil industry since the 1960s but offers efficient well rehabilitation options for water well professionals.

I shared in the presentation my experiences and perception that we need to cross-pollinate some of the practices that are ongoing in the oilpatch with that of current demand and needs in the water well industry. Not only with drilling and completion practices but site supervision and the emphasis on safety on all of our drill and well rehabilitation projects.

I received a lot of notoriety and some pushback on the presentation at the time by folks who laughed and said such cross-pollination isn’t affordable by those in the water well industry. Well, let’s fast-forward to today. As I look around, I still stand by my insistence that we continue to look over the fence and see what they are doing in the patch and what we could take from their practices and apply them to our own efforts in the water well industry.

The challenge facing us today, in addition to additional costs, should be forcing us to reconsider different practices within the water well industry. Saying we can’t afford to do something even when we know there are viable solutions available seems less about costs and more about clinging to older practices.

So, just as I did back in 2007, I want to revisit the subject of coiled tubing as a viable alternative and option in addressing repetitive well rehabilitation cleanouts. Whether we are facing challenging depths, diameter, repetitive entry and exit requirements from a wellbore, or are limited to time constraints with
conventional threaded 20-foot to 30-foot treatment strings—coil tubing can offer unique opportunities to be really viable.

A Simplistic Nature

Coiled tubing has been around for more than 40 years. Its nature is simplistic. It is a relatively small-diameter, pliable steel tubing wrapped onto a reel and trailered to a jobsite with a support crane and straightener. Once straightened, the tubing is run out and into the wellhead bound for the bottom of the well. After initial setup takes place on the surface, it is just a matter of minutes before the coiled tubing is sitting at the bottom of the well.

The coiled tubing is a continuous run of flexible metal pipe requiring no other connection that can range from 1.66 to 3.25 inches in diameter. This continuous spool of tubing is delivered to the jobsite on a trailer along with a high-pressure pump and the ability to map continuously through this string of tubing.

Coiled tubing (CT) has been an invaluable resource to oilpatch operators since the mid-1960s, used for everything from cleanouts, acid stimulation, fracturing, cementing, logging, plugging the setting, and retrieving downhole tools. Any manner of fluids can be pumped through the tubing from water to nitrified foam, cement, and fracking fluids. It can also be employed to do well logging and well perforating. The only thing CT cannot do is rotate.

Once on site, the CT is spooled out and runs through a straightener and specialized injector that feeds the tubing down the well and controls the tubing progress. Once on the bottom, the well is circulated clean. It is then only a matter of minutes until the process is reversed, and the open-end CT can be returned to the surface and then fitted with the next tool of the desired process of acid introduction, fracturing, cementing, logging, or isolation tool placement.

The coiled tubing unit is central to CT surface operations. It consists of a reel that holds a continuous length of flexible steel pipe. After that, the tubing is deployed downhole by spooling it off the reel and guiding it through a gooseneck that directs the CT downward to an injector head. It becomes straight before it enters the borehole. Everything is controlled from the surface by operators in an operator’s booth.

Coiled tubing units typically possess one or more triplex pumps for the option of mixing and injecting any matter of fluids or foam that might be desired downhole. They are self-contained and have pumps that can operate between 3000 PSI to 5000 PSI.

Once on the bottom of the well or upon completion of the desired treatment, the flexible steel tubing configurations even allow for the continuous pumping of fluids while the spool is reeled back up to the surface.

Speedy and Efficient

Coiled tubing is extremely adaptive to the demands we currently face in our industry. It offers unique versatility, it is adaptable, and can be used for various operations such as well intervention, stimulation, cleanouts, and logging to enhance a given well’s performance.

Its flexible nature allows operators to navigate complex wellbore configurations efficiently and with greater confidence. It enables faster deployment, minimizing the need for time-consuming rigging-up processes and enhancing overall operational efficiency.

Granted, coiled tubing is more expensive upfront than that of our current completion techniques and practices. Yet the speed and efficiency which the tubing can offer water well contractors should no longer be ignored, as it offers significant cost savings with time over the well with its greater overall efficiency.

Well rehabilitation projects that currently require time-consuming makeup requirements can be completed in a matter of minutes. It can circulate the well clean, run back to the surface, have a spinning high-pressure jetting head installed, and go back to the bottom in record time. That is work that would typically take days now being done with coiled tubing in a matter of minutes.

Coiled tubing eliminates the numerous hours of making up numerous joints, laying down and then picking up the same pipe and running it back in. With coiled tubing, wells are cleaned out and returned to service within a matter of hours versus days. This means while the initial upfront cost is higher, you’re off the well sooner in light of the quick turnaround time and can now do additional wells on any given day.

I would never expect universal acceptance of coiled tubing within the water well industry, but I do know that oil and gas activities have been waning recently, so some equipment is sitting underutilized in the oilfield. Some special requirements may be needed to truly cross over between an oilfield-configured rig to meet the regulatory demands for use with a producing water well, but opportunities exist and some are being addressed on projects we’re involved in today.

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Now that it has been some time, and I think back to my McEllhiney presentation, I think what I said is as true today as it was back then. I stand by much of what I shared back then. As we consider options and opportunities for the future, we need to understand the need for more cost-effective and timelier approaches to well workovers.

Edd Schofield is the technical sales manager–chemicals for Johnson Screens and has been with the company since 1988. He served as the Groundwater Foundation’s McEllhiney Distinguished Lecturer in Water Well Technology in 2007. He can be reached at edd.schofield@johnsonscreens.com.