Dynamic Mud Weight Window Calculation for Wellbore Stability

Solution Overview

Problem

Existing wellbore drilling technologies fail to accurately determine a mud weight window that prevents both underpressure-induced collapse and overpressure-induced fracturing of formation rock, as they do not account for time-dependent stress and pore pressure perturbations.

Innovation Solution

The method involves determining the rock type and fracture nature of the formation rock to select between drained and undrained solutions, which are then combined with poroelastic or dual-poroelastic models to calculate a time-dependent mud weight window using stress and pore pressure equations, incorporating failure criteria like the Drucker-Prager criterion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If drilling mud pressure is increased to prevent collapse of formation rock, then wellbore stability is improved, but fracture of formation rock may occur due to exceeding fracture threshold

Engineering Contradiction:

Improvewellbore stabilityVSAvoidformation rock fracturing

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The system dynamically adjusts drilling mud weight parameters based on real-time calculations of collapse and fracture thresholds. By continuously monitoring formation properties and calculating the mud weight window, the system changes the mud weight parameter to maintain optimal wellbore stability while preventing formation fracturing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system implements a feedback mechanism where drilling parameters, formation properties, and mud weight effects are continuously monitored. The calculated mud weight window provides feedback guidance for adjusting mud weight, ensuring that wellbore stability is maintained without exceeding fracture thresholds.

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If drilling mud pressure is decreased to avoid fracture of formation rock, then formation rock safety is improved, but collapse of formation rock may occur due to falling below collapse threshold

Engineering Contradiction:

Improveformation rock fracturingVSAvoidwellbore stability

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The system dynamically adjusts drilling mud weight parameters based on real-time calculations of collapse and fracture thresholds. By continuously monitoring formation properties and calculating the mud weight window, the system changes the mud weight parameter to maintain optimal wellbore stability while preventing formation fracturing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system implements a feedback mechanism where drilling parameters, formation properties, and mud weight effects are continuously monitored. The calculated mud weight window provides feedback guidance for adjusting mud weight, ensuring that wellbore stability is maintained without exceeding fracture thresholds.

Inventive Principle:

Principle #23Feedback

3Ease of operation

If a static mud weight is used during drilling, then operational simplicity is maintained, but it cannot account for time-dependent stress and pore pressure perturbations

Engineering Contradiction:

Improvedrilling operation simplicityVSAvoidmud weight window accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system transitions from static mud weight specification to dynamic mud weight adjustment. The mud weight window is calculated based on time-dependent stress and pore pressure perturbations, allowing the system to adapt mud weight recommendations as drilling conditions evolve, thereby improving reliability while maintaining operational simplicity through automated calculations.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary calculations of the mud weight window before drilling operations begin and updates them as new data becomes available. This preliminary action provides operators with advance guidance on appropriate mud weight ranges, maintaining operational simplicity while accounting for time-dependent factors.

Inventive Principle:

Principle #10Preliminary action

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 provides a dynamic mud weight window that avoids both collapse and fracturing by accurately accounting for stress and pore pressure changes during drilling, improving wellbore stability and safety.

Implementation Method 1

selecting a poroelastic model or dual-poroelastic model based on whether the formation rock includes fractures

Methodology Applied

Scientific EffectPoroelasticity: Elasticity

Data Source

PatentUS11486244B2Systems and methods for determining mud weight window during wellbore drilling

Publication Date: 2022.11.01 SAUDI ARABIAN OIL CO

AI summary

Systems and methods for determining a time-dependent mud weight window are disclosed. The existence of fractures in formation rock along with a type of the formation rock are used to determine the use of a particular solution to determine the mud weight window at a particular time of a wellbore drilling operation.