Page 10 - Oil and Gas Simulations
P. 10

GEORG-AUGUST-UNIVERSITY, GERMANY

PUMPING AND INJECTING FROM A
SINGLE BOREHOLE

Düsensauginfiltration, which translates as “nozzle-suction-infiltration,” is a technology for
dewatering that avoids the effort, costs, and environmental risks of conveying water from the
original site. Modeling is being used to understand why and how this novel approach works.

by JENNIFER HAND                             Co-Authored by Prof. Martin Sauter, Ph.D. Student Yulan Jin,
                                                                     and Assoc. Prof. Dr. Ekkehard Holzbecher,

                                                              Georg-August-University, Göttingen, Germany

FIGURE 1. Sketch of the borehole abstraction (pumping) and infiltration (injection)        is working in collaboration with Hölscher
concept.                                                                                   Wasserbau, a leading German dewatering
                                                                                           company, within the framework of the
Groundwater levels often need to be          separated into two parts: The upper part      DSI project. The project is financially
lowered in order to keep construction        of the borehole is the abstraction section    supported by Deutsche Bundesstiftung
or mining sites dry. Known as achieving      and the lower is the reinjection section      Umwelt (DBU). “Our role is to explain
“drawdown,” the traditional approach         (see Figure 1). These two parts are usually   why this method achieves results, to
is to abstract (pump out) water, and         separated by packers.                         understand its advantages and limitations,
discharge it back into the ground away                                                     and identify in which situations it would
from the site or into a surface water           Well hydraulics expert Werner Wils         work best,” comments Prof. Dr. Ekkehard
body. This approach can have a negative      has successfully used this method, also       Holzbecher, who leads the research team.
impact on the environment. The local         known as JSISWW (Jet Suction Infiltration
ecosystems at each site are disrupted and    System Werner Wils) in his company since         Yulan Jin, a doctoral student, is using
subsidence, contamination of ground or       2000. It has attracted much attention in      COMSOL Multiphysics® software to build
surface water, and soil degradation are all  Germany and Netherlands, where there          both 2D and 3D models. She describes the
potential consequences. In addition, there   are companies licensed to use the system,     objectives: “We are modeling alongside
are the costs of transport and disposal,     and it is also being used in Vietnam and      field experiments that are taking place
with increased expenses if water needs to    China. Practical experience shows that        in Germany so that we can compare
be treated before it can be returned to      it is successful, yet it is not completely    results with measured data. We want to
the ground.                                  understood. It is not clear under which       accurately predict the response of the
                                             conditions the technology works and in        system to changing boundary conditions.”
   In contrast, Düsensauginfiltration (DSI)  which situations it would not work. The
involves abstraction of groundwater near     challenge is to examine the technique         èPROVING THE BASIC
the groundwater table and injection          scientifically and this is being done at the  PRINCIPLE
into the same borehole, but at a greater     Georg-August-University of Göttingen.
depth. This avoids the transport of water                                                  A model solving for pressure (or hydraulic
away from the site as water is not lifted       The Department of Applied Geology          head) and the deformation of the aquifer,
at all, and also has the effect of reducing  of the University of Göttingen, led by        was set up in 2D, where Figure 2 shows
subsidence. In effect, the borehole is       Prof. Dr. Martin Sauter, concentrates on      a typical result. As the hydraulic head is
                                             research in the field of hydrogeology and     lowered at the upper part of the borehole
                                                                                           (indicated in blue) it creates a drawdown
                                                                                           of the upper boundary, representing the
                                                                                           groundwater table. This demonstrates the
                                                                                           fundamental principle that drawdown
                                                                                           does occur in the aquifer, even if water is
                                                                                           injected into the lower part.

                                                                                                 The same situation was then modeled
                                                                                           in 3D to take into account ambient
                                                                                           groundwater flow. The borehole, which is
                                                                                           represented as a cylinder, included depth-
                                                                                           dependent abstraction or injection rates
                                                                                           that were specified as sources and sinks
                                                                                           in the mathematical model. In the results
                                                                                           for the test case depicted in Figure 3, the
                                                                                           same drawdown phenomena as the 2D
                                                                                           model were apparent.

OIL GAS&
     comsol news industry focus
   5   6   7   8   9   10   11   12   13   14   15