Frac Plug Slip With Left-Hand Thread Retention
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Solution Overview
Problem
Current frac plugs in oil and gas production often shift within tubular sections, preventing full compression of sealing elements and allowing extrusion during reservoir stimulation, which hampers effective isolation and production.
Innovation Solution
A frac plug design featuring a slip with a left-hand thread pattern and tapered surfaces that engages with the tubular section, ensuring secure positioning and full compression of the sealing element, and includes a method for setting and removing the plug using a running tool to prevent movement during milling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a central mandrel with upper and lower slips is used to hold the frac plug in place, then the plug can be positioned within the tubular section, but the plug may shift when a sealing ball is installed and the sealing element may not fully compress
Solution Approach 1:
The patent inverts the conventional thread direction from right-hand to left-hand threads on the slip. This inversion causes the slip to engage the tubular section in a way that prevents plug shift during sealing ball installation, ensuring the sealing element can fully compress without the plug moving out of position.
Solution Approach 2:
The patent introduces asymmetric features including the left-hand thread pattern and the angled crest of thread crests. These asymmetric elements create a mechanical interference that prevents the plug from shifting in either direction, thereby maintaining proper sealing element compression while ensuring position stability.
2Manufacturing precision
If the sealing element is positioned between the slips, then the element can be compressed, but the sealing element cannot fully compress if the slips become fully engaged prior to full compression
Solution Approach 1:
By inverting the thread direction to left-hand threads, the slip engagement sequence is reversed. This allows the sealing element to be compressed first, achieving full sealing, before the slips become fully engaged with the tubular section, eliminating the constraint that prevented full compression.
3Reliability
If conventional frac plugs are used during reservoir stimulation, then isolation can be achieved, but the seal may extrude or the plug may move during milling or grinding operations
Solution Approach 1:
The left-hand thread pattern with angled crests creates an asymmetric mechanical lock between the slip and tubular section. This asymmetric engagement prevents the plug from rotating or moving during clockwise milling operations, maintaining position stability while preserving isolation effectiveness.
Solution Approach 2:
The left-hand thread pattern is designed to counteract the clockwise rotational forces applied during milling operations. The angled thread crests create a preliminary mechanical resistance that prevents plug movement before any extrusion or displacement can occur during the milling process.
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 design maintains the frac plug's position within the tubular section, ensures full compression of the sealing element, and prevents movement during milling, enhancing the reliability of isolation and production processes.
Implementation Method 1
The slip may include an annular body having a first axial end, a second axial end, an inner surface, an outer surface, and an axial length. The outer surface may include a left-hand thread pattern that extends from the first axial end along a portion of the axial length
Implementation Method 2
The method may also include milling the frac plug in a clockwise direction such that the left-hand thread pattern defined in the outer surface of the slip further engages with the tubular section and prevents movement of the frac plug away from a milling tool
Implementation Method 3
The annular body may include a taper on the inner surface that extends along the axial length of the annular body. The sealing element may be circumferentially disposed about the plug body and seal an annulus between the frac plug and a tubular section when actuated
Data Source
AI summary
A slip for a downhole tool is provided. The slip may include an annular body having a first axial end, a second axial end, an inner surface, an outer surface, and an axial length. The annular embody further includes a taper on the inner surface that extends along the axial length of the annular body, and a left-hand thread pattern defined by the outer surface and extending from the first axial end along a portion of the axial length, each thread of the left-hand thread pattern having a crest that is angled toward the first axial end.