Dissolvable Mandrel Frac Plug for Full-Bore Flow-Through
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Solution Overview
Problem
Current hydraulic fracturing technologies face challenges with dissolvable plugs that are not fully dissolvable, unsuitable for high-pressure and high-temperature applications, and require costly milling operations for plug removal, which can be difficult especially in low-pressure wells or when casing collapses.
Innovation Solution
Development of a hybrid frac plug that transforms from a temporary solid-core bi-directional isolation plug to a full-bore flow-through plug using acid- or brine-dissolvable mandrel, allowing for self-isolation and easy removal without mechanical intervention, utilizing a dissolvable mandrel and a millable retaining sleeve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dissolvable materials are used for frac plugs, then plug removal is simplified and milling operations are reduced, but the plugs are not fully dissolvable and require incomplete dissolution leaving restrictions
Solution Approach 1:
The frac plug is divided into two distinct materials: a dissolvable mandrel that completely dissolves to remove isolation restrictions, and a millable retaining sleeve that remains to provide structural support. This segmentation allows each component to fulfill its specific function - the mandrel for complete dissolution and the sleeve for maintaining plug integrity during operation.
Solution Approach 2:
The frac plug combines two different materials with complementary properties: a dissolvable material (mandrel) that completely dissolves to eliminate restrictions, and a millable material (retaining sleeve) that provides structural support. This composite structure resolves the contradiction by having each material perform its optimal function.
2Reliability
If traditional solid-core frac plugs are used, then high-pressure and high-temperature applications are supported, but costly milling operations are required for plug removal
Solution Approach 1:
The plug structure is segmented into a dissolvable mandrel that handles the high-pressure/high-temperature structural requirements during operation, and a separate dissolvable component that completely dissolves to eliminate the need for costly milling operations for removal.
Solution Approach 2:
The mandrel material is selected to maintain structural integrity at high pressures and temperatures during the fracturing operation, then changes state through complete dissolution after the operation, transforming from a structural component to a removable restriction that fully dissolves.
3Ease of operation
If dissolvable frac plugs are used, then milling operations are reduced, but the plugs cannot be removed in low-pressure wells or when casing collapses
Solution Approach 1:
The plug is segmented into a dissolvable mandrel that completely dissolves to create flow-through boreholes, and a millable retaining sleeve that can be mechanically removed. This provides adaptability: in normal conditions the mandrel dissolves completely, but in difficult conditions (low pressure, collapsed casing) the millable sleeve can be mechanically retrieved and removed.
Solution Approach 2:
The millable retaining sleeve acts as an intermediary that provides a mechanical interface for retrieval operations. When complete dissolution is not feasible due to well conditions, the retaining sleeve serves as a intermediary component that can be mechanically removed to restore production.
4Productivity
If temporary self-isolation plugs are used, then production potential is maximized after dissolution, but the plugs must be completely dissolved which traditional materials cannot achieve
Solution Approach 1:
The plug structure segments the isolation function (provided by the dissolvable mandrel that completely dissolves to maximize production) from the structural support function (provided by the millable retaining sleeve). This allows complete dissolution of the isolation component while maintaining structural integrity during operation.
Solution Approach 2:
The mandrel material undergoes a complete parameter change through dissolution, transforming from a solid isolation structure to complete dissolution, maximizing production potential by eliminating all restrictions in the flow path.
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
Enables efficient plug removal and immediate production by dissolving the mandrel to create a full-bore ID, reducing milling intervention costs and overcoming limitations in high-pressure and high-temperature conditions, and facilitating production in both high and low-pressure zones.
Implementation Method 1
The mandrel is constructed of a dissolvable material, wherein the mandrel is dissolvable through application of a solvent in order to form a flow-through bore
Data Source
AI summary
A transforming bridge-to-flow-through frac plug has a mandrel, a retaining sleeve, a pair of cones, a pair of slips, a packing element, and a keeper ring. The mandrel is concentrically connected within the retaining sleeve, and is constructed of a dissolvable material such that the mandrel is dissolvable through application of a solvent in order to form a big bore flow-through frac plug if removal of the frac plug by milling is not possible. The pair of cones, pair of slips, packing element, and keeper ring are positioned on the exterior of the retaining sleeve in order to secure the frac plug in place after a setting operation, even if the mandrel is dissolved in order to form the big bore flow-through frac plug.