Don’t Discount Horizontal Wells Due to Limited Set Back or Small Rig Up Areas

We’ve discussed a myriad of topics regarding horizontal wells in our “Inflection Points” newsletter over the past ten years or so. The intent of our newsletter is to provide technical knowledge on how horizontal directional drilling (HDD) can be used to solve complex challenges for the environmental, geotechnical, and water supply industries. We certainly hope we are succeeding and welcome feedback from you, the reader.

In the past several issues we’ve discussed set back distance and rig up areas. These are definitely important when evaluating the applicability of HDD for well installations. Both set back and the area required for the rig and ancillary equipment can pose significant challenges when dealing with small or complex sites. We have provided some rules of thumb for set back – the “normal”, for every 1’of depth (V), figure about 5’ of horizonal displacement/set back (H) i.e. 1V:5H and rig up areas from 20’x50’ to over 150’x150’ for big rigs. However, rules are meant to be broken and we can be incredibly creative when trying to fit a rig onto a site. So this issue of Inflection Points is dedicated to what we call “weird” rig up locations.

Weird Rig Up #1

Our first weird rig up takes place in Colorado at a UST site. As with most gas station locations the site was tiny and bounded on two sides by street rights-of-way. Additionally, the topography sloped significantly away from the proposed entry locations, complicating the set back distance issue – we just couldn’t get deep enough, fast enough to hit the start of the screen section. As we were about to leave the site, disappointed we wouldn’t be able to help with horizontal wells, we overheard discussions about the upcoming tank pull. Shoring would have to be driven around the tank, a roughly 12’ deep excavation dug and then the tank would be removed. Now comes the creative or weird part. If we could place the rig into the excavation, we could hit the downslope/down gradient targets because the entry point would be 12 feet lower. Working with the client we were able to place the rig in the bottom of the pit and drill two remediation wells that solved this complex issue.

Weird Rig Up #2

Now let’s go to the East Coast for weird rig up No 2. This was a dry cleaner location in a strip mall. The owner and consultant wanted horizontal SVE wells under the parking area. However, there wasn’t enough room behind the building, and placing the drill rig in the front parking lot would have severely impacted the operation of the other retail outlets. Our solution at this location was to place the rig inside the former dry cleaner and drill out into the parking lot, installing blind SVE wells. There were some complications with working inside a small space. The first was the exhaust from the rig. This issue was solved by running the exhaust through a filter and then discharging the exhaust via a long hose out the back door. We also supplemented the filtering with fans as an additional engineering control. Additionally, it was very noisy – a horizontal drill rig inside a small, enclosed space is loud – the crew and consultant had to wear extra hearing protection.

From the East Coast to California, we’ll call this weird rig up No 2a. Another dry cleaner with an even tinier footprint. The front of the facility was directly on a busy street and the back of the building was up against another structure. The sub slab vapor mitigation wells needed to be completed under the former dry cleaner and under an adjacent retail space. In this case we were able to place the rig “half in and half out” of the building at the front door. This allowed us to hit our sub slab screen targets without impacting the busy thoroughfare in front of the building.

Weird Rig Up #3

California brings us to the third weird rig up area. This project entailed using HDD methods to obtain soil samples directly under occupied residential buildings. Essentially a condominium type setting with the buildings placed tightly together, space for the drill rig was severely limited and we had very specific targeted sample locations. This was a project where the field team improvised and set the rig up between buildings and up against fencing. The crew was able to wriggle the rig into the proper location so we could hit the target and obtain soil samples at the proper location.

Hopefully we have provided some valuable information regarding sites with small rig up areas and limited set back distances – and made you smile a bit with the photos. As the title of this newsletter suggests, don’t discount horizontal wells as a remediation option if the site is tiny or weirdly shaped. Give us a call and we’ll try to think outside of the box a provide options for you to review.