Diagnostic Fracture Injection Test Permeability Estimation
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Solution Overview
Problem
Unconventional subterranean reservoirs, such as shale gas and tight gas formations, pose challenges in hydrocarbon extraction due to their low permeability and the high costs associated with pressure pumping and fracturing treatments, necessitating more efficient methods for evaluating formation properties before costly operations.
Innovation Solution
The implementation of diagnostic fracture injection tests (DFITs) using a system with coiled tubing, isolation packers, and a hydraulic pump to inject fluid at high pressure, monitoring pressure data before and after fracture closure, and applying mathematical models like the Before Closure Analysis (BCA) to estimate permeability without relying on limiting assumptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional well testing and specialized tests are performed to understand formation properties, then production forecasting and treatment optimization improve, but operational costs and time expenditure increase
Solution Approach 1:
The patent applies partial action by performing a diagnostic fracture injection test that injects fluid only to the point of fracture initiation and early propagation, rather than conducting a full-scale hydraulic fracturing treatment. This partial injection provides sufficient data for permeability estimation and formation property characterization without the time and cost expenditure of complete fracturing operations, thereby resolving the contradiction between measurement precision and time loss
2Measurement precision
If diagnostic fracture injection tests are performed to estimate permeability, then treatment optimization improves, but operational costs increase
Solution Approach 1:
The DFIT methodology uses partial action by injecting fluid only until fracture initiation and early propagation occur, then shutting in the well before complete fracture treatment. This partial injection provides the necessary pressure and volume data for accurate permeability estimation through analysis of the injection and shut-in phases, avoiding the need for large-scale fluid injection required in full fracturing treatments, thus resolving the contradiction between measurement precision and quantity of substance
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 allows for accurate estimation of formation permeability and fracture properties, optimizing hydraulic fracturing treatments and reducing operational costs by providing detailed insights into subterranean formations without requiring extensive a priori information.
Implementation Method 1
injecting a fluid through a well into a subterranean formation at an injection pressure sufficient to cause a fracture of the subterranean formation
Implementation Method 2
monitoring a pressure of the fluid injected into the subterranean formation after shutting in the well
Data Source
AI summary
In an example diagnostic fracture injection test (DFIT), or a “minifrac,” a fracturing fluid is pumped at a relatively constant rate and high pressure to achieve a fracture pressure of a subterranean formation. Sometime after achieving formation fracture pressure, the pump is shut off and the well is shut in, such that the pressure within the sealed portion of the well equilibrates with the pressure of the subterranean formation. As the pressure declines, the pressure of the injection fluid is monitored. This collected pressure data is then used to determine information regarding the permeability of the subterranean formation. In some implementations, a model for before closure analysis (BCA) can be used to estimate the permeability of a formation based on before closure pressure data (i.e., data collected before the fracture closure pressure is reached) based on a solution to the rigorous flow equation of fracturing fluid, which is leaking off into the formation during fracture closure.