Retrievable Frac Mandrel with Well Control Stack for Live-Well Operations

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Solution Overview

Problem

Existing wellhead isolation tools are expensive, difficult to remove without killing or plugging the well, and often get stuck, making them unsuitable for marginal hydrocarbon production zones that require stimulation.

Innovation Solution

A retrievable frac mandrel and well control stack system that includes a frac mandrel with a contoured bottom end for high-pressure fluid seal and a well control adapter with axial seal bore, allowing for secure locking and easy removal from the wellhead, enabling full-bore access for downhole operations without damaging the well.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If prior art wellhead isolation tools are used to protect sensitive wellhead equipment during high-pressure stimulation, then pressure isolation is provided, but the tools are expensive to use due to labor costs associated with delivering and operating them and cannot be removed from a live well

Engineering Contradiction:

Improvepressure isolationVSAvoidremoval from well

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The isolation system is divided into two functional segments: the frac mandrel that remains in the wellhead providing pressure isolation, and the well control stack that can be removed. This segmentation allows the pressure isolation function to be permanently installed while the operational control equipment can be removed after use.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The well control stack (including flow control equipment, BOP, or other pressure control devices) is extracted from the permanent installation and can be removed from the wellhead after the stimulation operation is complete, while the frac mandrel remains in place to maintain pressure isolation.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If prior art wellhead isolation tools are used to provide pressure isolation during stimulation, then high-pressure fluid containment is achieved, but the tools get stuck in the wellhead making them difficult or impossible to remove without killing or plugging the casing

Engineering Contradiction:

Improvehigh-pressure fluid containmentVSAvoidremoval from wellhead

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

A release mechanism acts as an intermediary between the frac mandrel and the wellhead, providing a controlled method to disengage the mandrel from the wellhead. This intermediary system allows the mandrel to be securely locked during operation and then cleanly released when removal is desired, preventing it from getting stuck.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The release mechanism is pre-installed and configured in the wellhead before the frac mandrel is installed. This preliminary preparation ensures that the removal path is already established and that the mandrel can be released without killing the well or plugging the casing.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If a retrievable frac mandrel with well control stack is left on the wellhead throughout completion operations, then full-bore access is maintained, but the system complexity increases

Engineering Contradiction:

Improvefull-bore accessVSAvoidsystem configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system is segmented into the frac mandrel (providing full-bore access and pressure isolation) and the well control stack (providing flow control). This segmentation allows each component to perform its specific function independently, simplifying the overall system while maintaining full-bore access capabilities.

Inventive Principle:

Principle #1Segmentation

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 system allows for cost-effective and safe well completion, re-completion, or workover operations by providing a secure high-pressure seal and easy retrieval of the frac mandrel and well control stack, reducing labor costs and operational delays.

Implementation Method 1

the bottom end being contoured to be received in the tubing head spool and to provide a high-pressure fluid seal with a seal bore located above a bit guide of the tubing head spool

Methodology Applied

Scientific EffectMechanical sealing: Mechanical Fastener

Implementation Method 2

the well control adapter including an axial seal bore that receives the top end of the frac mandrel to provide a high-pressure fluid seal around a periphery of the top end

Methodology Applied

Scientific EffectMechanical sealing: Mechanical Fastener

Data Source

PatentUS7775288B2Retrievable frac mandrel and well control stack to facilitate well completion, re-completion or workover and method of use

Publication Date: 2010.08.17 OIL STATES ENERGY SERVICES LLC

AI summary

A retrievable frac mandrel and a well control stack are used to efficiently accomplish well completion, re-completion or workover. The retrievable frac mandrel is inserted in a tubing head spool of a well to be completed, re-completed or re-worked. The well control stack is mounted to a top of the tubing head spool and seals off against a top of the retrievable frac mandrel. Once well completion, re-completion or workover is completed, the frac mandrel can be retrieved from the tubing head spool without killing or plugging the well.