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nSIGHTS: A Numerical Hydraulic Test Simulator

nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) is a Windows-based numerical hydraulic-test simulator that provides state-of-the-art well-test analysis tools for analysis of single-phase water and gas tests. The nSIGHTS approach to data visualization and data processing/analysis is based on the conceptual paradigm of pages and objects. The pages and objects are organized in an object tree, allowing the analyst to arrange the hundreds of available nSIGHTS objects in an infinite number of ways to accomplish anything they can imagine. nSIGHTS can be run in forward or inverse mode to handle everything from test design to analysis and parameter estimation. Because well-test analysis is an inverse problem with inherent uncertainty in the model’s fitting-parameter estimates, nSIGHTS has multiple methods for quantifying this uncertainty, including the calculation of joint-confidence regions and perturbation analysis. Numerous features include:

A multi-sequence test consisting of a shut-in/equilibration period, followed by a DST flow and shut-in period, and finally a pulse injection test. The entire sequence was matched using nSIGHTS.

  • Multi-sequence simulation – simulate any combination of aquifer tests including Pump tests (constant-rate, constant-pressure (head)), slug, or pulse tests;
  • Incorporate long-term pre-test pressure histories critical in low-permeability testing environments
  • Changing wellbore skin;
  • Pressure-dependent hydraulic conductivity for tests in fractured systems;
  • Pressure-dependent test-zone compressibility often observed in pulse tests performed at near-atmospheric pressures;
  • Non-radial flow dimensions (n) – beyond the standard linear (n = 1), radial (n = 2), or spherical (n = 3) flow systems that are typically modeled, nSIGHTS recognizes that flow dimensions in fractured/heterogeneous systems often have non-integer values, e.g., n = 1.7. nSIGHTS includes a full suite of flow-dimension diagnostic plots for all types of tests (Beauheim et al. 2004_Flow Dimension Diagnostics);
  • Multiple specialized plots including pressure derivatives with rate superposition, decline curves, Horner, Ramey A, B, and C, deconvolved pulse/slug response, and flow-dimension diagnostics;

3 slices of a 3-D parameter space. The best-fit value for each of the three fitting variables is indicated by the location of the lowest SSE value within the parameter space.

  • Presentation quality 2-D and 3-D plots that can be cut/pasted directly into reports;
  • On-screen animation of 3-D plots for data visualization – animation frames can be exported to create AVI files;
  • Advanced data filtering to remove barometric and earth-tide effects, allowing the analyst to see small test-related responses that might otherwise be masked;
  • Easily incorporate variable flow rates or variable pressures during aquifer tests that were intended to be constant rate/pressure tests;
  • Latin-hypercube and Monte Carlo sampling routines to investigate the correlation between fitting and non-fitting model parameters;
  • Any number of data types (pressure, derivatives, flow rates, etc.) and test sequences can be matched simultaneously to better constrain the fitting-parameter estimates.

Filtering of noisy well data. After removing both barometric and earth-tide effects, a response due to pumping can be seen.

nSIGHTS was used to successfully match the flow rates measured during a “constant” pressure test by using the somewhat variable pressures directly as model input. Estimating the hydraulic parameters of interest was not a problem even though the test performance was non-ideal.

An nSIGHTS generated pressure profile to investigate a hypothetical 40-year pumping scenario.

For curious folks, the current nSIGHTS User’s Manual can be downloaded here: Users Manual nSIGHTS V2.5. A description of the code’s mathematics can be downloaded here: GTFM Tech Doc. Note that the mathematical description refers to GTFM, the DOS predecessor to nSIGHTS.

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