Composite Mandrel Threaded Insert for Downhole Load Bearing
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Solution Overview
Problem
Current downhole devices, such as frac plugs and bridge plugs, with composite threaded members often fail to withstand high loads due to insufficient shear values, which can lead to damage during run-in and subsequent wellbore operations.
Innovation Solution
A mandrel with a recess and a packing element is used, along with a threaded member having a threaded outer surface with greater strength than the mandrel, to absorb higher loads, and a guide member is threaded onto this insert to provide additional support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If threads are formed directly on composite mandrels, then the mandrel can be simplified in structure, but the shear area is reduced and the mandrel strength deteriorates
Solution Approach 1:
The mandrel is divided into two functional parts: a composite mandrel body and a separate threaded insert. The threaded insert is placed around the mandrel body and secured within a recess, allowing the threading function to be separated from the composite mandrel structure. This segmentation prevents direct threading on the composite material, preserving its shear strength while providing the necessary threading capability through the insert.
Solution Approach 2:
A threaded insert acts as an intermediary component between the composite mandrel and the guide member. The insert is made of metal or other strong material that can accommodate threading without compromising the composite mandrel's integrity. The insert transfers loads between the guide member and the mandrel, protecting the composite material from direct stress concentration at thread roots.
2Weight of moving object
If composite material is used for the mandrel, then weight is reduced and corrosion resistance is improved, but the shear values are insufficient to withstand high loads
Solution Approach 1:
The solution uses a hybrid composite structure combining composite material (for the mandrel body) with metal or strong material (for the threaded insert). The composite mandrel body provides lightweight and corrosion-resistant properties, while the metal insert provides high shear strength and load-bearing capacity. This composite approach allows the system to achieve both weight reduction and sufficient strength by strategically combining materials with complementary properties.
Data Source
AI summary
An apparatus for use in a wellbore is disclosed that in one non-limiting embodiment includes a mandrel having a recess on a lower section thereof, a packing element around the mandrel, wherein the packing element provides a seal between the apparatus and the wellbore when the packing element is expanded radially outward from the mandrel; and a threaded member having a threaded outer surface placed around the lower section of the mandrel, and wherein strength of the threaded member is greater than the strength of the lower section of the mandrel. The apparatus may further include a guide member threaded on the threaded member to provide support to the mandrel. The apparatus may be utilized as a frac plug and a bridge plug.