Horizontal remediation wells(HRWs) technology for contaminated site remediation

Source: B&R Working Committee

Applicating Company

Jiangsu Dadi Benesource Environmental Remediation Co.Ltd

Technology Name

Technical principle

There are often unremoved facilities or obstacles such as production facilities, roads, tracks, and underground storage tanks on the contaminated sites, which make the traditional in-situ remediation technology unable to be effectively implemented. The horizontal remediation well technology takes the advantage of the horizontal directional drilling technology to install the remediation wells underground without disturbance on the surface building, which can also realize the precise layout of the remediation wells in the contamination plume.
The HRWs can combine chemical oxidation/reduction agent injection, air sparging/gas phase extraction, biological ventilation, groundwater extraction treatment, light non-aqueous phase liquid (LNAPL) extraction, and many other new technologies for the treatment of site contaminants.

Figue1 Horizontal well drilling principle

Scope of application

The horizontal remediation well technology is mainly suitable for the remediation of sites with many surface obstacles, such as production facilities, roads, tracks, underground storage tanks, etc. where traditional restoration techniques cannot be implemented on these sites.

Besides, it is suitable for sites with long contamination plumes and thin thickness. It can remarkably reduce the wells number and the remediation cost.

Process flow and description

(1) First, based on the site investigation data, accurately outline the
distribution of contamination plumes;

(2) Combine the distribution of plumes, contaminants concentrations, stratigraphic information, hydrogeological conditions, etc., accurately design the horizontal remediation wells process, including the plane and cross-section layout, well types, injection amount of chemical agents;

(3) According to the above parameters and surrounding boundary conditions, COMSOL Multiphysics is used to simulate the remediation performance and optimize the core parameters;

(4) The drilling rig shall drill according to the positioning entry point after the drilling rig is in place;

(5) Drill horizontally and ream the holes according to the designed trajectory and depth, and drill out at the designated excavation point;

(6) Connect the pre-fabricated horizontal remediation wells and drag them back to the entry point; complete the laying of all horizontal well pipes in sequence;

(7) Due to the large amount of mud during the drilling process, the horizontal well pipes need to be flushed to prevent the well pipes from being clogged;

(8) After the well flushing is completed, inject the chemical agents according to the designed chemical ratio and injection process;

(9) The groundwater needs to be monitored and sampled during the chemical injection operation and maintenance period to analyze the process effect.

Figue2 HRW tech process

Promotion prospects

At present, there are few application cases of horizontal remediation well technology, and there is a lack of large-scale practical experience. This project is the first engineering demonstration implementation of large-scale horizontal remediation well technology in China. The development of technology provides practical reference, and has broad prospects for promotion and use. With the advancement of soil and groundwater investigation of in-production enterprises, the state's advocacy of precision and smart remediation during the "14th Five-Year Plan" period, non-destructive, non-excavation directional and precision remediatoin technology are bound to attract attention.

Through the development of the past ten years, the site remediation industry in China has gradually transformed from rough to refined and standardized. The characteristics of the horizontal remediation well technology are greatly in line with the scientific concept of "smart investigation and precise remediation" vigorously advocated by the state. In addition, by reducing energy consumption and reducing damage to the surface ecological environment, horizontal remediation well technology can achieve green and sustainable remediation goals.