Cased-Hole Formation Tester for Cement Defect Quantification
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Solution Overview
Problem
Current methods for evaluating wellbore zonal isolation and detecting defects in annular cement between the casing and formation are inadequate, as they provide only qualitative assessments and do not effectively quantify subtle cement defects or cement transmissibility, posing safety and operational risks in CO2 sequestration and oil and gas production.
Innovation Solution
A tool and technique using a cased-hole formation tester with a drill and pressure measurement system to detect and quantify hydraulically connected defects in the cemented annulus, allowing for real-time detection and volume estimation of micro-annuli and cracks by interpreting passive pressure measurements from single-probe cased-hole formation testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic measurements are used to evaluate cement quality, then the evaluation can be performed, but only qualitative assessment is provided and quantitative estimation of cement defects is not achieved
Solution Approach 1:
The patent replaces ultrasonic measurement methods with a pressure-based formation testing system. A drill creates a borehole through the casing into the cement annulus, and a pressure probe measures pressure decay as fluid flows through the cement. This mechanical pressure-based system substitutes the ultrasonic method, enabling quantitative measurement of cement permeability and defect characterization that was not achievable with qualitative ultrasonic assessment alone.
Solution Approach 2:
The patent introduces a pressure probe as an intermediary measurement device. The probe is positioned within the cement annulus through a drilled borehole and serves as the mediator between the testing system and the cement material. By measuring pressure decay and flow rate through this intermediary probe, the system obtains quantitative data about cement permeability and defect characteristics that directly addresses the limitation of ultrasonic methods.
2Measurement precision
If pressure probe methods are used to quantify cement permeability, then permeability estimation is achieved, but information on the presence and size of isolation defects is not provided
Solution Approach 1:
The patent segments the cement annulus evaluation into distinct components: first assessing overall cement permeability through pressure decay measurements, then separately characterizing defect properties (presence, size, location) by analyzing deviations from expected pressure behavior and using drill position information. This segmentation allows both permeability estimation and defect characterization to be achieved independently and combined for comprehensive evaluation.
Solution Approach 2:
The pressure probe system performs multiple functions: it measures pressure decay to estimate cement permeability, detects the presence of isolation defects by identifying abnormal pressure behavior, and determines defect size and location using drill position data. This multi-functional approach eliminates the need for separate testing methods and provides comprehensive cement annulus evaluation in a single integrated system.
3Measurement precision
If a drill and pressure measurement system is used to detect defects, then real-time detection and quantification of isolation defects is achieved, but device complexity increases
Solution Approach 1:
The patent merges the drilling function and pressure measurement function into a single integrated tool assembly. The drill creates the borehole through the casing while the pressure probe, positioned within the same assembly, simultaneously measures pressure decay in the cement annulus. This merging eliminates the need for separate drilling and testing operations, reducing overall operational complexity despite the sophisticated nature of the individual components.
Solution Approach 2:
The drill serves a dual purpose: it creates the borehole for accessing the cement annulus and simultaneously positions the pressure probe within the cement for measurement. The drill position information is used directly to determine defect location, eliminating the need for separate positioning systems. This self-service approach reduces the number of independent subsystems required.
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
Enables almost real-time detection and quantification of isolation defects, providing critical information for remedial actions and ensuring project safety by accurately estimating the volume and transmissibility of cement defects, thereby improving wellbore integrity.
Implementation Method 1
drilling through the casing and into cement surrounding the casing
Implementation Method 2
observing a pressure of the fluid within the housing and the annulus
Implementation Method 3
the pressure in the housing equalizes with the pressure in the cement annulus through the drilled hole
Data Source
AI summary
A method for evaluating wellbore integrity including introducing a drill to a surface of a casing encompassing an annulus, enclosing the drill in a housing hydraulically isolating the surface, drilling through the casing and into cement surrounding the casing, observing a pressure of the fluid, and using the pressure observation and a drill position to evaluate a presence of a defect and a location of the defect. Apparatus for evaluating wellbore integrity including a probe comprising a drill, wherein the probe is hydraulically isolated from the wellbore, a valve that encompasses the drill, a pressure gauge to measure the pressure of the fluid within the housing, a pressure gauge to measure the pressure in the system outside the housing, and equipment to compare the pressure measurements and the position of the drill and to evaluate a presence and a location of the defect.