24 FEBRUARY 2023 WorldWide Drilling Resource® Replacing Aging Remediation Systems with Horizontal Wells Adapted from Information by Directional Technologies, Inc. When existing soil or groundwater remediation systems begin to falter, it presents an opportunity to evaluate more effective solutions. The selection of a replacement mitigation/remediation system will have impacts that may be felt for years or even decades. Even if the existing system functioned effectively, oftentimes there are advantages to alternative designs. Modern horizontal wells are increasingly being used to replace aging vertical wells of years past. Various scenarios present compelling reasons to consider replacing aging vertical mitigation/remediation wells with horizontal wells. The following are two of the most common scenarios. Scenario 1: Failing Remediation Systems: Even the best-designed mitigation/remediation systems come with a limited life span. Wells can begin to fail due to a host of factors which can become increasingly costly to manage the longer a remediation system stays in operation. Many vertical well systems that have been in operation for decades were designed when horizontal well technology was still in its early stages. With advances in technology, engineering, and drilling techniques, modern horizontal wells often outperform their vertical counterparts. Horizontal wells are frequently used to solve design challenges that cannot be easily overcome using traditional wells. The main advantages of horizontal wells in this scenario include: e Unparalleled access to the contaminant plume, regardless of site conditions at the surface. e Increased mitigation/remediation performance due to precise targeting of the contaminant plume, greater well screen volume in direct contact with contaminated media, and increased radius of influence. e Fewer wells are required, leading to reduced long-term costs. e Installations of wellheads at the entry and exit point of the horizontal installation allow remediation equipment to be shifted from one end of the well to the other as site conditions change over time. Scenario 2: Converting Long-Term Mitigation Systems to Short-Term Remediation Solutions: At some sites, it made sense in years past to pursue longterm mitigation for large releases that were challenging to remediate. At these sites, remediation techniques were used primarily to control contaminant plumes and prevent contamination from spreading to sensitive areas. While these systems can reduce overall contaminant concentrations as part of their operation, they were designed as a long-term engineering control rather than a remediation measure to result in regulatory closure. These systems often represent a substantial annual operational cost which usually has no projected end date. However, horizontal wells can overcome challenging site conditions which have historically presented barriers to realistically remediating large releases once and for all. Horizontal wells also present additional advantages when converting to a short-term remediation strategy, such as: e Overcoming complex site conditions presented by infrastructure, business operations, or rock formations. e Eliminating annual costs of system operation once remediation goals are achieved. e Avoiding unanticipated future costs due to changing environmental regulations. e Achieving regulatory closure. Decisions to install new remediation systems can have lasting effects. At a wide variety of sites, horizontal wells can be used to achieve better remediation outcomes that benefit timelines, budgets, and success rates. DIR
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