All Mechanical Counter Dart for Frac Sleeve Counting
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Solution Overview
Problem
The traditional method of using balls or darts to actuate landing features in the resource recovery and fluid sequestration industry is limited by the diameter of the string and the practicality of small feature sizes, restricting the number of fracture stages possible in a wellbore.
Innovation Solution
An all-mechanical counter dart with a mandrel, movable shoulder members, and an upset to support the members in an active position, allowing them to traverse and count frac sleeves by moving radially outward and inward, with a biasing member and guide rails facilitating movement and a stop detent for load management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional balls or darts are used to actuate landing features, then the method is simple and reliable, but the number of fracture stages is limited by string diameter and practicality of small feature sizes
Solution Approach 1:
The counter mechanism is divided into multiple independent shoulder members (first shoulder member, second shoulder member, third shoulder member) that can be selectively engaged. Each shoulder member corresponds to a specific frac stage, allowing the system to count and actuate multiple fracture stages sequentially without requiring a completely different mechanism for each stage.
Solution Approach 2:
The shoulder members are designed to be movable between engaged and disengaged positions along the mandrel. The biasing member dynamically positions the shoulder members, allowing them to automatically engage with frac sleeves as the dart moves downhole and disengage when the selected stage is reached, enabling adaptive counting without complex mechanical linkages.
2Productivity
If the number of fracture stages is increased, then the versatility and productivity are improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The mandrel serves multiple functions: it provides the structural backbone for the dart, supports the biasing member that actuates the shoulder members, carries the upset that engages the frac sleeves, and provides the pathway for the shoulder members to move between engaged and disengaged positions. This multi-functionality reduces the need for separate components and simplifies manufacturing.
Solution Approach 2:
The biasing member and upset are integrated into the mandrel structure, with the upset formed as a continuous feature on the mandrel surface. The shoulder members are directly mounted on the mandrel and biased by the integrated biasing member, combining what could have been separate assemblies into a unified structure that is easier to manufacture and assemble.
3Adaptability or versatility
If shoulder members are made movable to count frac sleeves, then the adaptability and counting capability are improved, but the reliability and load-holding capacity are challenged
Solution Approach 1:
The upset acts as an intermediary element between the shoulder members and the frac sleeves. When a shoulder member engages a frac sleeve, the upset provides a mechanical interface that transfers and holds the load. The continuous upset feature on the mandrel ensures consistent load transmission throughout the counting and actuation process, maintaining reliability while enabling movable counting capability.
Data Source
AI summary
An all mechanical counter dart including a mandrel, a plurality of shoulder members disposed upon the mandrel and movable from a more downhole portion of the mandrel to a more uphole portion of the mandrel, individual ones of the plurality of shoulder members moving from an inactive position to an active position and back to an inactive position while traversing the mandrel, and an upset on the mandrel supporting the individual ones of the plurality of shoulder members when in the active position.