Flushing-water discharge limitation and directed development in open-loop ATES systems

In 2050, when the Netherlands will no longer be using natural gas, approximately 25 percent of the buildings will have a thermal energy system. Following the installation, and during maintenance operations, of open-loop aquifer thermal energy storage (ATES) systems, the wells need to be flushed and developed. The flushing and development water contains dissolved and suspended materials such as clay particles, iron, salt and drilling fluid residues. The discharge of this water into surface water or the sewer system is undesirable because it can deteriorate water quality. Licensing authorities are applying increasingly strict requirements regarding water quality and maximum discharge flowrate. The problem also occurs to a lesser extent during maintenance when wells clog during the use phase and need to be regenerated. In this project we focus on the development and verification of techniques to reduce the volumes of flushing water during drilling, and to improve well development (essentially, cleaning the well to render it operational).

Technology

Discussions with the actors involved, such as drilling companies, indicate that with the current techniques it is difficult to limit discharges during the development of wells. We consider the following new development paths to be promising for the control of flushing water discharges:

Applying other types of support fluids during drilling, in combination with additives during the development of the well.
Increasing the effectiveness of the mechanical development methods that are today typically used in the installation of ATES wells.
Improving methods for the objective determination of the specific volume flow upon the completion of an ATES, so that it is clear when the drilling company can stop the well development.

Challenge

The project begins with a literature study in the area of well development with support fluids and alternative mechanical development methods. Lab-scale tests are then conducted to determine the power with which a specific operational mechanism needs to be applied to properly develop a well. Thus, for example: How many pulsations are required and how powerful do the pulsations need to be? Or what types or concentrations of chemicals are the most effective? And which combination works most effectively on a lab scale? The methods developed are then also tested in the field. Here, our goal is to verify whether these techniques actually work in practice in removing the clogging.

Solutions

The project should offer alternative chemical and mechanical methods for the directed development of wells. In addition, a method will be validated that makes it possible to determine whether the maximum capacity of a specific well has been reached.