Mill-through Tailpipe Liner Exit for Sidetrack Drilling

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Solution Overview

Problem

Current methods for drilling sidetrack wells face challenges such as precise targeting difficulties, expensive drill rig time, and restricted access to lower formations due to the use of kickoff plugs and permanently installed whipstocks, especially in wells with high constriction ratios between casing and liner.

Innovation Solution

A process involving the installation of a liner, a tubing string, a releasably attached tailpipe with millable stabilizing bands, a packer assembly, and a whipstock assembly, which allows for a single milling operation through the tailpipe and liner, minimizing clearance and enabling precise sidetrack wellbore drilling with reduced cement usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a kickoff plug is used to initiate sidetrack drilling, then drilling direction can be changed, but access to lower formations is restricted due to cement sealing

Engineering Contradiction:

Improvedrilling direction changeVSAvoidaccess to lower formations

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent employs a disposable bridge plug instead of a permanent kickoff plug. The bridge plug is set temporarily to guide the milling operation and then retrieved after use, allowing subsequent access to lower formations. This resolves the contradiction by providing the directional change capability during drilling while eliminating the permanent restriction on future formation access.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The system transitions from a static, permanent kickoff plug to a dynamic, retrievable bridge plug. The bridge plug can be set and retrieved as needed, providing temporary guidance during milling while allowing future flexibility. This dynamic approach resolves the contradiction between needing directional control now and maintaining future access options.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If a permanently installed whipstock is used for sidetrack drilling, then drilling precision is improved, but access to lower formations is blocked

Engineering Contradiction:

Improvedrilling precisionVSAvoidaccess to lower formations

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent uses a temporary bridge plug with an integrated whipstock rather than a permanent whipstock installation. The bridge plug provides the necessary guidance precision during the milling operation and is then retrieved, maintaining both drilling precision and future access to lower formations.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The whipstock is incorporated into the temporary bridge plug setup specifically for the preliminary milling operation. Once the mill passes through the casing and liner, the bridge plug is retrieved and the whipstock is no longer needed, having served its preliminary guidance function. This resolves the contradiction by providing precision when needed without permanent restriction.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If multiple milling runs are performed through tailpipe and liner, then precise targeting is achieved, but drill rig time and cost increase

Engineering Contradiction:

Improvetargeting precisionVSAvoiddrill rig time

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent merges the tailpipe and liner milling operations into a single milling run. By carefully positioning the bridge plug and whipstock to create an aligned pathway, the mill can pass through both the tailpipe and liner in one continuous operation, eliminating the need for multiple separate milling runs and reducing drill rig time and cost.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bridge plug and whipstock are positioned in advance to pre-establish the correct milling pathway. This preliminary positioning ensures that the mill can proceed directly through both casing and liner in a single run without requiring intermediate repositioning or additional milling operations, thereby improving productivity while maintaining precision.

Inventive Principle:

Principle #10Preliminary action

4Stability of the object's composition

If extensive cementing operations are performed for window exits, then wellbore stability is improved, but access to lower formations is restricted and cost increases

Engineering Contradiction:

Improvewellbore stabilityVSAvoidaccess to lower formations

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent uses a temporary bridge plug that requires minimal or no cementing operations. The bridge plug is set mechanically and retrieved after serving its guidance function, avoiding the extensive cementing required by conventional window exit methods. This resolves the contradiction by providing wellbore stability during the operation while maintaining future access to lower formations.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS8256535B2Mill-through tailpipe liner exit and method of use thereof

Publication Date: 2012.09.04 CONOCOPHILLIPS CO

AI summary

A method and apparatus for forming a window in the wall of a tubular wellbore. In one embodiment described herein, a down hole apparatus for forming a window in the wall of a wellbore utilizing a plurality of tubing string sections and a thick tailpipe positioned at the down hole end of a tubing section.