Location of Repository

Aquifer Storage and Recovery : Physical and Geochemical Modelling (SWIFTPHREEQC)of British Aquifers for Aquifer Storage and Recovery Purposes.\ud Part 1, physical modelling and geochemical model calibration

By I. Gaus, A.T. Williams and P. Shand

Abstract

This report describes the progress that has been made in developing models simulating both the\ud physical and geochemical aspects of Aquifer Storage Recovery (ASR) schemes. This work is part of\ud a 30 month project, entitled ASR-UK, which started in April 1999. The report describes progress to\ud the end of 1999.\ud SWIFT is a fully transient 3-Dimensional model that simulates flow and transport of fluids. It is\ud ideally suited to modelling ASR and has been used to simulate the response of the four major aquifers\ud in UK – Chalk, Lincolnshire Limestone, Sherwood Sandstone and Lower Greensand.\ud Ranges of parameters applicable to these aquifers, which encompass dual-porosity, fractured and\ud porous aquifers, were used to predict their response to a hypothetical, but realistic, cycle testing\ud programme and an annual operational cycle over five years.\ud Sensitivity analyses of the model’s responses to changes in matrix porosity, fracture porosity, fracture\ud permeability and thickness were carried out for each aquifer for the operational cycles. In addition,\ud sensitivity analyses to changes in matrix diffusivity and dispersivity were undertaken for the Chalk\ud aquifer.\ud The results showed low sensitivity to parameters in the estimated ranges with only matrix porosity\ud having a significant effect in the Chalk, the Lincolnshire Limestone and the Sherwood Sandstone.\ud The main conclusion is that dual-porosity aquifers will need more conditioning than single porosity\ud aquifers. However, the suitability of any aquifer depends on the dispersive and diffusive parameters\ud which can generally only be obtained from field trials.\ud SWIFT cannot incorporate geochemical reactions, both water/water and water/rock, which can be\ud important in determining recovered water quality. PHREEQC is a reactive model which can quantify\ud processes likely to occur in ASR schemes. In a non-reactive mode, PHREEQC was successfully\ud calibrated to the output from SWIFT and sensitivity analysis on the physical aspects of the model was\ud executed in four stages of increasing complexity.\ud PHREEQC has several limitations in describing the physical aspects of an ASR-cycle including:\ud • a simplified conceptualisation of dual porosity.\ud • inability to define injection or recovery rate.\ud • conceptualisation of radial flow in a one-dimensional model.\ud A variety of techniques were used to overcome these limitations including a thorough calibration to\ud the results of the SWIFT model.\ud Linking the two models successfully should enable both the physical and geochemical aspects of ASR\ud to be simulated. This will provide a valuable tool to assist site selection and design of testing and\ud operational schemes. The programme of continued research and development is identified in order to\ud achieve the objectives of the project

Publisher: British Geological Survey
Year: 2000
OAI identifier: oai:nora.nerc.ac.uk:12691

Suggested articles

Preview

Citations

  1. (1993). Geochemistry, groundwater and pollution. doi
  2. (1997). The physical properties of major aquifers in England and Wales.
  3. (1999). User’s guide to PHREEQC (version 2) – A computer program for speciation, reaction-path, 1-D transport, and inverse geochemical calculations.

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.