Estimating Anisotropic Elastic Constants Using Sonic Logging Data
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for determining elastic constants in unconventional reservoirs, such as shale gas reservoirs, face limitations due to their assumption of homogeneous formations, which does not account for spatial heterogeneities, leading to inadequate placement of fracturing stages and perforation clusters for efficient hydrocarbon production.
Innovation Solution
A method that applies acoustic waves to estimate elastic constants C13, C23, C33, C44, C55, and C66 using sonic data acquired in vertical and lateral wellbores, allowing for the determination of minimum and maximum horizontal stresses and anisotropic mechanical properties, enabling optimal placement of fracturing stages and perforation clusters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If sonic data from a large volume of earth is used to estimate elastic constants, then the measurement coverage is improved, but the measurement precision deteriorates due to averaging effects that mask spatial heterogeneities
Solution Approach 1:
The patent divides the formation into multiple small, discrete volumes (elements) along the wellbore trajectory. Each element is analyzed independently to determine local elastic constants, rather than averaging over a large volume. This segmentation allows the method to capture spatial heterogeneities while maintaining measurement precision at each location.
Solution Approach 2:
The patent applies local quality by determining elastic constants for each small formation element individually, allowing each location to have its own specific mechanical properties. This approach recognizes that different parts of the formation have different properties and enables precise characterization of local heterogeneities, which is critical for optimal fracturing stage placement.
2Device complexity
If conventional workflows assume homogeneous formation, then the device complexity is reduced, but the manufacturing precision of fracturing stage placement deteriorates
Solution Approach 1:
The patent changes the approach from assuming a single homogeneous set of elastic constants for the entire formation to determining multiple local elastic constant values at different depths and locations. This parameter change from global to local characterization enables precise fracturing stage placement while managing complexity through systematic data acquisition and inversion procedures.
3Ease of manufacture
If elastic constant C13 is estimated from other sources or approximate models, then the ease of manufacture is improved, but the reliability of the estimation deteriorates
Solution Approach 1:
The patent makes the system self-service by determining all necessary elastic constants (including C13) directly from sonic log data acquired in the wellbore, without requiring external sources, core plug measurements, or approximate rock physics models. The inversion procedure simultaneously solves for multiple elastic constants using the available sonic data, making the system self-contained and eliminating reliance on external calibration data.
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 method provides accurate estimates of elastic constants and mechanical properties, enabling more precise placement of fracturing stages and perforation clusters, thereby enhancing hydrocarbon productivity by accounting for spatial variations in reservoir properties.
Implementation Method 1
applying acoustic waves to the formation and detecting acoustic waves to acquire acoustic data
Data Source
AI summary
A method includes applying acoustic waves to the formation and detecting acoustic waves to acquire acoustic data. The method further includes determining (i) at least one of elastic constant C13 and elastic constant C23, (ii) elastic constant C33, (iii) at least one of elastic constant C44 and elastic constant C55, and (iv) elastic constant C66 using the acquired acoustic data. Elastic constant C11 is determined using elastic constant C33, at least one of elastic constant C44 and elastic constant C55, elastic constant C66, and a relationship between Thomsen parameter gamma and Thomsen parameter epsilon.