Posted on February 22, 2022 by Jacob Gallagher

Ellingson crews recently had the opportunity to install a “full-scale” soil vapor exctraction (SVE) system at a site where we’d installed the initial pilot study wells several years back.

Project Starts with a Small Pilot Study

In May of 2018 Ellingson-DTD mobilized to a site in the Eastern US to drill and install a single, sub-slab, “pilot study” SVE well. Crews completed the short (80ft) well 5ft below an operating manufacturing plant in a blind (single entry) borehole.

It only took one day to rig up, drill and install the well. Crews had to install the well a little short of the planned total length due to a utility at unkown depth along the borepath. Unfortunately that represents a pretty typical obstacle in the field. Mysterious utilities are the bane of many a horizontal well designer’s existence.

Pilot study objectives included determing the following parameters:

• Could horizontal well installation proceed at the site without disrupting the ongoing facility operations?
• If so, would a “pre-packed” screen (EnviroFlex™) work for an SVE application in a “blind” or single-ended configuration?
• Finally (most importantly), what is the radius of influence from the SVE well?

The pilot study proved the feasibility of installing 5ft sub slab wells without impacting operations.

In addition to this core demonstration, two other lessons learned included:

1 . Future well alignments must consider the old and poor quality utility maps available for the site.

2 . The site geology allowed for the blind installation of EnviroFlex™ prepacked well screen.

Of course, the ROI of the SVE well and effectiveness of the remediation design remained yet to be determined.

Work Expands into a Full-Scale Effort

Fast forward to October of 2021. Once they’d operated the system for a few years, the engineering consultant called and low and behold! They determined the horizontal well had an ROI of ~25ft. That meant the 300ft wide building only required an additional five (5) wells to achieve full coverage. Additionally, the SVE effort had reduced concentrations quite effectively. In other words, the full-scale project appeared economical and the gears began turning for full-scale implementation.

The full-scale work scope included an additional five blind wells, similar to the pilot well. Well designs targeted a total vertical depth of 5ft below the slab. Total screen lengths ranged from 50ft to 125ft depending on utilities.

The full-scale field effort lasted ten days. Of course, the biggest challenge remained identifying the depth of all the utilities along the well paths. In fact, one of the wells passed so close to a utility the decision was made to expose the buried line and watch the directional drill bit pass the potential obstruction.

Tags: blind horizontal wells, Enviroflex, full-scale, horizontal SVE, pilot study, remediation, SVE, SVE ROI

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