Underbalanced Drilling Modeling for Plastic Damage Depth Prediction
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Solution Overview
Problem
Underbalanced drilling often induces plastic mechanical damage to the surrounding rock mass, leading to wellbore instability, which is not adequately addressed by existing methods.
Innovation Solution
A method for optimizing underbalanced drilling by collecting in situ conditions and formation properties, creating an underbalanced drilling model, modeling the drilling process, and adjusting the pre-drilling plan based on plastic mechanical damage depth, using a mechanical simulation to predict and mitigate wellbore collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If underbalanced drilling is used, then formation damage is minimized and rate of penetration is increased, but plastic mechanical damage to surrounding rock mass is induced leading to wellbore instability
Solution Approach 1:
The patent applies preliminary action by performing numerical simulations before actual drilling to predict plastic mechanical damage depth. The simulation model incorporates in situ stresses, formation properties, and drilling parameters to forecast wellbore stability and identify potential collapse zones in advance, allowing operators to adjust drilling parameters or modify the wellbore path before damage occurs during drilling operations.
Solution Approach 2:
The patent implements feedback by using simulation results to iteratively adjust drilling parameters and wellbore design. The predicted plastic damage depth from numerical modeling is fed back to optimize drilling parameters such as mud weight, drilling speed, and wellbore trajectory, creating a closed-loop system that continuously improves wellbore stability while maintaining high rate of penetration.
2Loss of energy
If underbalanced drilling is used, then lost circulation is reduced and differential sticking is eliminated, but plastic mechanical damage depth increases causing wellbore collapse
Solution Approach 1:
The patent applies preliminary action by performing numerical simulations before actual drilling to predict plastic mechanical damage depth. The simulation model incorporates in situ stresses, formation properties, and drilling parameters to forecast wellbore stability and identify potential collapse zones in advance, allowing operators to adjust drilling parameters or modify the wellbore path before damage occurs during drilling operations.
Solution Approach 2:
The patent applies parameter changes by using numerical simulation results to optimize drilling parameters such as mud weight, drilling speed, and wellbore trajectory. The simulation identifies critical parameter thresholds that prevent plastic damage while maintaining underbalanced drilling benefits, allowing dynamic adjustment of parameters throughout the drilling process to minimize harmful effects.
3Reliability
If numerical simulation modeling is performed to predict plastic mechanical damage, then wellbore stability is improved, but computational complexity and time required increase
Solution Approach 1:
The patent applies segmentation by dividing the wellbore into discrete radial zones based on predicted plastic damage depth. The numerical model segments the formation into an inner damaged zone and an outer intact zone, allowing simplified analysis of stress distribution and stability in each region. This segmentation reduces computational complexity by focusing calculations on critical zones rather than the entire formation.
Solution Approach 2:
The patent applies local quality by assigning different mechanical properties and stress states to different radial zones around the wellbore. The inner zone experiences plastic deformation and reduced strength, while the outer zone maintains intact properties. This spatial differentiation of material properties allows the model to capture local variations in mechanical behavior without requiring complex global modeling of the entire formation.
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 accurate prediction of plastic mechanical damage depth, enhancing wellbore stability and optimizing drilling performance by refining the drilling plan to minimize collapse risk.
Implementation Method 1
calculating changes of in situ stresses induced by a pressure drop inside the wellbore
Implementation Method 2
The underbalanced drilling model includes stress changes in the first area and the second area
Implementation Method 3
Modeling of the drilling process is accomplished by repeatedly reducing the stress borne by the second area in increments and solving the underbalanced drilling model to mechanical equilibrium to determine the stress borne in the first area
Data Source
AI summary
In general, in one aspect, embodiments disclosed herein relate to a method for optimizing underbalanced drilling according to depth of damage. The method includes collecting in situ conditions, well conditions, and formation properties of a subterranean area of interest, calculating changes of in situ stresses induced by a pressure drop inside the wellbore, creating an underbalanced drilling model using the in situ conditions, well conditions, and formation properties, modeling the drilling process, extracting and evaluating plastic mechanical damage from the underbalanced drilling model, adjusting a pre-drilling plan based on the depth of plastic mechanical damage, and finally using the modeled drilling process to drill a well. The in situ stresses include a maximum and minimum confining stress. The underbalanced drilling model includes a mechanical simulation of a first area representing rock surrounding the wellbore, and a second area representing rock inside the wellbore.