Time-Lapse Sonic Shear Moduli for Sanding Detection
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Solution Overview
Problem
Conventional sonic logging methods struggle to detect shear head waves in slow formations, and existing technologies lack reliable methods to identify sand production zones in production wells, which can lead to severe sand damage and reduced hydrocarbon production.
Innovation Solution
The use of time-lapse sonic data to characterize formation anisotropy through vertical and horizontal shear moduli, specifically by analyzing changes in cross-dipole flexural and Stoneley dispersion data, allowing for the identification of sanding occurrences and estimation of near-wellbore alteration zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sonic logging methods are used to detect shear head waves, then measurement can be obtained in fast formations, but detection capability deteriorates in slow formations where shear wave velocity is less than borehole-fluid compressional velocity
Solution Approach 1:
The patent changes the measurement parameters from traditional single-time sonic logging to time-lapse sonic logging, measuring formation properties at multiple times (before and after production). This allows detection of changes in shear modulus that indicate sand production, overcoming the limitation of conventional methods in slow formations by using temporal changes rather than absolute velocity values.
Solution Approach 2:
The patent implements feedback by comparing sonic measurements taken before production with measurements taken after production. This time-lapse approach provides feedback on formation property changes, specifically increases in horizontal shear modulus that indicate sand production, enabling detection even in slow formations where conventional single-time measurements fail.
2Reliability
If existing technologies are used to identify sand production zones, then no reliable method exists, but conventional methods cannot provide accurate identification leading to severe sand damage and reduced hydrocarbon production
Solution Approach 1:
The patent applies preliminary action by measuring sonic properties before production begins, establishing a baseline of formation properties. This preliminary measurement allows subsequent measurements during production to be compared against the baseline, enabling early detection of sand production changes before severe damage occurs.
Solution Approach 2:
The patent uses feedback by continuously monitoring formation properties during production and comparing them with pre-production baseline data. This feedback mechanism enables real-time identification of sand production zones through changes in shear modulus, allowing for timely intervention to prevent severe sand damage and maintain hydrocarbon production.
3Reliability
If time-lapse sonic data is used to characterize formation anisotropy through shear moduli, then sanding events can be identified, but the complexity of analyzing cross-dipole flexural and Stoneley dispersion data increases
Solution Approach 1:
The patent applies segmentation by separating the analysis into distinct components: measuring compressional wave velocity, measuring shear wave velocity through dispersion analysis, calculating vertical shear moduli from dipole flexural dispersion, and calculating horizontal shear modulus from Stoneley dispersion. This segmented approach manages the complexity of multi-parameter anisotropy characterization.
Solution Approach 2:
The patent simplifies the complex anisotropy characterization by focusing on specific parameter changes - namely, increases in horizontal shear modulus relative to vertical shear moduli - that indicate sand production. This parameter-focused approach reduces the complexity of analyzing all possible formation property changes.
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 enables the qualitative identification of sanding events and quantification of their impact on hydrocarbon production, helping to prevent sand production and maintain well integrity by accurately determining changes in formation properties over time.
Implementation Method 1
mechanical disturbances can be used to generate elastic waves in earth formations surrounding a borehole
Implementation Method 2
one or more acoustic sources and one or more acoustic receivers
Implementation Method 3
placing a piezoelectric source and an array of hydrophone receivers inside a fluid-filled borehole
Implementation Method 4
The head waves are caused by the coupling of the transmitted acoustic energy to plane waves in the formation that propagate along the borehole axis
Implementation Method 5
An incident compressional wave in the borehole fluid produces critically refracted compressional waves in the formation. The critical incidence angle θi=sin−1(Vf/Vc)
Implementation Method 6
a dipole source primarily excites the lowest-order flexural borehole mode together with compressional and shear head waves
Data Source
AI summary
Systems and methods for identifying sanding in production wells using time-lapse sonic data. Formation anisotropy can be characterized in terms of shear moduli in a vertical wellbore, e.g., vertical shear moduli C44 and C55 in the wellbore axial planes and horizontal shear modulus C66 in the wellbore cross-sectional plane. Changes in formation anisotropy between different times can provide qualitative indicators of the occurrence of sanding in the production well. Before production begins, the horizontal shear modulus C66 is typically less than the vertical shear modulus C44 or C55 or both. At a subsequent time after sanding occurs, the horizontal shear modulus C66 is typically greater than the vertical shear modulus C44 or C55 or both. By comparing the shear moduli of the vertical wellbore at different times, it is possible to identify the occurrence of sanding in the production well using time-lapse sonic data.