Numerical Simulation for Minimum In-Situ Stress Determination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for determining the minimum horizontal in-situ stress of a subterranean formation from well injection test data are unreliable due to inaccuracies in pressure fall-off analysis, especially in low permeability formations, leading to uncertainties in hydraulic fracture treatment design and execution.
Innovation Solution
A method involving numerical simulation of well injection tests with varying simulated in-situ stress values to match measured pressure responses, utilizing models for porous medium deformation, fluid flow, and fracture propagation to accurately determine the minimum horizontal in-situ stress, thereby improving the reliability of stress estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure fall-off analysis is used to determine minimum horizontal in-situ stress, then the stress value can be estimated, but the accuracy and reliability of the estimation deteriorates due to uncertainties in fracture closure pressure determination
Solution Approach 1:
The patent replaces the traditional pressure fall-off analysis method with a numerical simulation approach. The simulation model incorporates rock mechanics, fluid flow, and fracture propagation physics to predict pressure responses during injection tests. By comparing simulated pressure curves with actual measured data and adjusting stress parameters accordingly, the method achieves more reliable minimum horizontal in-situ stress determination without relying on uncertain fracture closure pressure measurements.
Solution Approach 2:
The patent introduces numerical simulation as an intermediary between the injection test data and the stress determination. The simulation model acts as a mediator that processes measured pressure responses through physical principles (rock deformation, fluid flow, fracture mechanics) to extract accurate stress values. This intermediary approach allows indirect determination of stress parameters that would otherwise be difficult to measure directly or reliably.
2Loss of time
If instantaneous shut-in pressure is used as an approximation of minimum horizontal in-situ stress, then the measurement time is reduced, but the accuracy of the stress value deteriorates
Solution Approach 1:
The patent performs preliminary numerical simulations before actual injection tests to pre-determine expected pressure responses and optimize test protocols. The simulation model is calibrated in advance with rock properties and stress conditions to predict how pressure should evolve during injection and shut-in. This preliminary action allows for more efficient test design that achieves accurate stress determination without requiring excessively long measurement periods.
Solution Approach 2:
The patent substitutes the simple instantaneous shut-in pressure measurement with a comprehensive numerical simulation approach that models the entire injection and shut-in process. The simulation incorporates rock mechanics, fluid flow, and fracture propagation to accurately determine stress parameters from measured pressure data, achieving both accuracy and reasonable measurement time by replacing the inadequate instantaneous pressure approximation with a physically-based simulation framework.
3Measurement precision
If pump shut-in is not truly instantaneous, then the pressure fall-off curve is confounded by both fluid dissipation and decreasing injection rate, but achieving true instantaneous shut-in is difficult to control
Solution Approach 1:
The patent replaces the difficult-to-control instantaneous shut-in operation with a numerical simulation approach. The simulation model incorporates the actual pump shut-in behavior (which may not be perfectly instantaneous) and automatically accounts for both fluid dissipation and decreasing injection rate effects. By modeling the complete pressure evolution process, the system can accurately determine fracture closure pressure without requiring perfect instantaneous shut-in control, thus improving measurement precision while maintaining operational ease.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a reliable estimation of minimum horizontal in-situ stress, enhancing the robustness of hydraulic fracture treatments and reducing uncertainties in injection system design and execution, applicable to both conventional and unconventional applications.
Implementation Method 1
The simulation may include a model of flow along a porous media according to Darcy's law
Implementation Method 2
The simulation may be configured with a capacity to model: (i) porous medium deformation
Implementation Method 3
a model of hydraulic fracture initiation wherein coincident faces separate under a traction load
Implementation Method 4
the direction that a hydraulic fracture will propagate from a wellbore into a subterranean formation is usually perpendicular to the least principal in-situ stress
Data Source
AI summary
A system of performing a well operation including determining a minimum horizontal in-situ stress of a subterranean formation, comprising: a first component configured to create a measured pressure response from data of a well injection test; a simulation component configured to generate a simulated pressure response with a selected value of a simulated minimum horizontal in-situ stress; and an arrangement to compare at least a portion of the simulated pressure response to a corresponding portion of the measured pressure response to resolve a difference; whereby the minimum horizontal in-situ stress of the formation may be equated to a value of the simulated minimum horizontal in-situ stress corresponding with a lesser resolved difference. Further aspects of the disclosure include novel methods.