Preprints
https://doi.org/10.5194/hess-2023-229
https://doi.org/10.5194/hess-2023-229
27 Nov 2023
 | 27 Nov 2023
Status: a revised version of this preprint was accepted for the journal HESS and is expected to appear here in due course.

Technical note: Wellbore water volume computation of tracer test in numerical modelling in a confined aquifer

Yiqun Gan and Quanrong Wang

Abstract. Computation of the water volume in the operational wellbore is a critical for numerical modeling of dissolved substances movement during aquifer remediation or tracer test in a confined aquifer, which affects the concentration variation, especially in the early stage of the test. In a confined aquifer, the water level is higher than the aquifer top elevation, and the water volume of the aquifer is controlled by the volume of aquifer when ignoring the water compressibility. We found that the wellbore was also treated to be confined in the numerical modeling of tracer test in a wellbore-confined aquifer system. As a result, the wellbore water volume is computed by the aquifer thickness instead of wellbore water level, such as the software package of MODFLOW/MT3DMS, which is incorrect. Actually, the wellbore is open to the air in the confined aquifer, and it is unconfined. In this study, a 3D reactive transport model is revised based on the mass balance in a well-aquifer system with special attention given to the wellbore water volume. The accuracy of new model is tested against benchmark analytical solutions. The results show that previous models may cause significant errors in both aquifer and wellbore for tests with injection wells. As for tests with extraction wells, the error is obvious in the wellbore, but not in the aquifer. Specifically, previous models overestimate the concentration of solute in both aquifer and wellbore under the injection well test case, while it underestimates the concentration in the extraction well test case. The revised model could increase the accuracy of reactive transport modeling in aquifer remediation through the wellbore.

Yiqun Gan and Quanrong Wang

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2023-229', Anonymous Referee #1, 01 Dec 2023
    • AC1: 'Reply on RC1', quanrong wang, 08 Jan 2024
  • RC2: 'Comment on hess-2023-229', Anonymous Referee #2, 18 Jan 2024
    • CC2: 'Reply on RC2', quanrong wang, 14 Jan 2024
    • AC2: 'Reply on RC2', quanrong wang, 24 Jan 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2023-229', Anonymous Referee #1, 01 Dec 2023
    • AC1: 'Reply on RC1', quanrong wang, 08 Jan 2024
  • RC2: 'Comment on hess-2023-229', Anonymous Referee #2, 18 Jan 2024
    • CC2: 'Reply on RC2', quanrong wang, 14 Jan 2024
    • AC2: 'Reply on RC2', quanrong wang, 24 Jan 2024
Yiqun Gan and Quanrong Wang
Yiqun Gan and Quanrong Wang

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Short summary
1. A revised 3D model of solute transport is developed in the well-aquifer system. 2. The accuracy of new model is tested against benchmark analytical solutions. 3. Previous models overestimate the concentration of solute in both aquifer and wellbore under the injection well test case. 4. Previous models underestimate the concentration in the extraction well test case.