A Type‐Curve Approach for Evaluating Aquifer Properties by Interpreting Shallow Strain Measured During Well Tests

Abstract

Strains occur at shallow depths in response to pressure changes during well tests in an underlying aquifer, and recent developments in instrumentation have made it feasible to measure essentially the full strain tensor. Simulations using poroelastic analyses indicate that shallow normal strains are approximately proportional to the logarithm of time when a well is injecting into or pumping from a deep aquifer or reservoir. The drawdown is also a linear function of log time, as shown by the classic Cooper‐Jacob type‐curve analysis. The time when the semilog straight line intercepts the zero‐strain axis is similar to the time determined from the Cooper‐Jacob pressure analysis, and it can be used to estimate hydraulic diffusivity, suggesting that horizontal strain data can be used directly to estimate aquifer properties. This approach was validated using measurements from shallow (30‐m deep) borehole strainmeters during an injection test at a 530‐m‐deep sandstone aquifer/reservoir in Oklahoma. The results show intercept times for the shallow normal strain data are essentially the same as for deep pressure data from an equivalent radial distance. The slopes of the semilog plots of the pressure and the strain increase at the same time, suggesting that they both respond to a lateral aquifer boundary. Significantly, though, strain was measured at shallow depths while the pressure data were measured at 530‐m depth. This suggests that strain data from shallow depths could be an effective way to improve the characterization of an underlying aquifer.

Using the Shallow Strain Tensor to Characterize Deep Geologic Reservoirs

“…The model was set up using Comsol Multiphysics using the approach described in Murdoch et al. (2019, Chapter 5; 2020, and 2021). The HEC lens was represented using the same cuboidal shape as the HEC lens in the analytical model, but the 3D numerical model calculates the pressures instead of approximating them from the data.…”

“…(b) Average horizontal and vertical strains with straight sections as in (a) based on Murdoch et al. (2021). (c) Boundaries of the permeable high energy channel lens from the October 2017 (thick orange line) and November 2017 (thin orange line) tests based on the analytical model.…”

“…One interpretation of this increase in the semi-log slope of the pressure during a well test is that the drawdown is affected by a lateral boundary (Streltsova, 1988). The hydraulic diffusivity and time of the change in slope of the pressure data can be used to infer the distance to the boundary as 𝐴𝐴 𝐴𝐴𝑏𝑏 ≈ 220 to 400 m (Murdoch et al, 2021). Using the change in slope of the semi-log strain data indicate that 𝐴𝐴 𝐴𝐴𝑏𝑏 ≈ 290 to 320 m. These results indicate that the hydraulic diffusivity and distance to the boundary of the reservoir estimated using standard well testing methods based on deep pressure measurements are essentially the same as the values estimated using a type-curve-like method of analyzing the shallow normal strain data.…”

Towards the Analysis of Reliability Index of Steel Frame Equipped with TADAS Yield Damper

“…By increasing the random variables and failure criteria, the reliability results will be more accurate. To evaluate the reliability of structures equipped with metal dampers, determine the reliability and structural failure, other methods such as system dynamics method [18,19,20,23] can be used instead of the Monte Carlo method. These methods include meta-models such as neural networks, support machines, and kriging.…”

Research on Test and Logging Data Quality Classification for Gas–Water Identification

“…It will cause great difficulties in the evaluation of the logging gas-bearing property in combination with the actual interval. Due to the strong inconsistency between the logging and test results, the test results are difficult to provide effective training samples or test basis for the judgment of gas layers, gas and water layers, and water layers [51]. Ultimately it will affect the establishment of effective fluid identification standards.…”