Wellhead Isolation Tool Lock Assembly Design

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Solution Overview

Problem

Wellhead isolation tools face challenges during oilfield operations due to extreme pressures and flow rates, leading to packoff assembly 'lift-off' and leakage, and require support against external forces to prevent damage.

Innovation Solution

A wellhead isolation assembly incorporating a lock assembly, anchor assembly, and adapter with self-energizing annular seals and threaded connections to secure the mandrel and packoff assembly, preventing fluid leakage and external force transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the packoff assembly is used to isolate the wellhead from fluid flow during fracturing operations, then the wellhead equipment is protected from fluid leakage, but the packoff assembly may lift-off from the sealing surface due to high fluid pressure and flow rates

Engineering Contradiction:

Improvesealing reliabilityVSAvoidresistance to lift-off force

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The lock assembly is engaged before fracturing operations begin, pre-securing the mandrel and packoff assembly against the wellhead. This preliminary locking action ensures that when high fluid pressures occur during fracturing, the packoff assembly is already restrained and cannot lift-off from the sealing surface, thus maintaining sealing reliability while withstanding lift-off forces

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The lock assembly applies a counteracting force in the opposite direction of the fluid pressure-induced lift-off force. By engaging the lock assembly's locking mechanism against the wellhead, it creates a balancing force that counterweights the upward lift-off force generated by high fluid pressure, preventing packoff assembly displacement and maintaining seal integrity

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Reliability

If the mandrel and packoff assembly are secured during extreme pressure operations, then protection from fluid leakage is achieved, but the assembly is subjected to extreme axial forces that may cause damage

Engineering Contradiction:

Improveprotection from leakageVSAvoidexternal axial forces

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The lock assembly acts as an intermediary structure between the mandrel/packoff assembly and the wellhead. It transfers and distributes the extreme axial forces generated during fracturing operations from the vulnerable packoff assembly to the more robust wellhead structure, thereby protecting the packoff assembly from damage while maintaining its sealing function under high pressure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The lock assembly is engaged in advance to provide structural support and force distribution capability before extreme axial forces occur during fracturing. This pre-positioned support structure cushions the mandrel and packoff assembly against the full impact of extreme axial forces, preventing damage while allowing the assembly to maintain its protective sealing function

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

The solution effectively isolates the wellhead from fluid flow and supports the mandrel and packoff assembly against axial forces, reducing the risk of leakage and damage during fracturing and other wellbore operations.

Implementation Method 1

a resilient metal seal adapted to be crushed between the first and second annular grooves

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

threaded connections to secure the mandrel and packoff assembly

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 3

lock assembly, anchor assembly, and adapter with self-energizing annular seals and threaded connections

Methodology Applied

Scientific EffectMechanical interlocking: Mechanical Force

Data Source

PatentUS10267115B2Wellhead isolation tool and methods

Publication Date: 2019.04.23 OIL STATES ENERGY SERVICES LLC

AI summary

An isolation tool and related methods for protecting a wellhead to which a casing string is operably coupled. In an exemplary embodiment, the isolation tool includes an anchor assembly adapted to be connected to the wellhead; a mandrel adapted to sealingly engage an interior portion of at least one of the wellhead and the casing string; and a lock assembly including a mandrel head connected to the mandrel and adapted to be displaced, relative to the anchor assembly and the wellhead, to sealingly engage the mandrel with the interior portion; a landing sleeve connected to the mandrel head and adapted to be displaced, relative to the mandrel head, the mandrel, the anchor assembly, and the wellhead, to engage the anchor assembly; and a connector adapted to secure the landing sleeve to the anchor assembly when the mandrel sealingly engages the interior portion and the landing sleeve engages the anchor assembly.