Multi-gate safety system for autonomous downhole perforating tools
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Solution Overview
Problem
Current well completion processes, such as the ACT-Frac method, require expensive surface equipment like cranes and lubricators, increasing project costs and complexity, and there is a need for a safer system to prevent premature activation of autonomous downhole tools like perforating guns.
Innovation Solution
A multi-gate safety system is introduced for autonomous downhole tools, which includes independently closing electrical switches activated by conditions like mechanical pull-tabs, pressure sensors, timers, and velocity sensors to prevent premature activation, and the tools are fabricated from friable materials for self-destruction after activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If autonomous downhole tools are used to eliminate surface equipment, then device complexity and cost are reduced, but reliability is worsened due to risk of premature activation
Solution Approach 1:
The patent implements preliminary safety actions by requiring multiple conditions to be satisfied before activation is permitted. A timer sets a time window, pressure sensors verify adequate bottomhole pressure, and mechanical switches must be closed in a specific sequence. These preliminary checks prevent premature activation while maintaining autonomy.
Solution Approach 2:
The activation system is segmented into multiple independent gates or switches, each controlled by a different condition (time, pressure, mechanical position). All gates must be closed for activation to occur, dividing the safety function into manageable segments that can be independently verified.
2Reliability
If multiple safety gates are implemented, then reliability is improved by preventing premature activation, but device complexity increases
Solution Approach 1:
The patent uses intermediary mechanical switches and timers as mediators between the sensor conditions and the final activation. These intermediaries translate complex sensor data into simple mechanical states (closed/open), reducing the complexity of the control logic while maintaining multiple safety checks.
Solution Approach 2:
The system is designed to be self-verifying through mechanical means. The pressure sensors and timers automatically verify conditions without requiring external monitoring or complex electronic control logic. The mechanical switches self-close when their conditions are met, providing automatic safety verification.
Data Source
AI summary
A tool assembly for performing a wellbore operation including an actuatable tool, a location device, and on-board controller are together dimensioned and arranged to be deployed in the wellbore as an autonomous unit. The actuatable tool, such as a perforating gun having associated charges, perforates a wellbore along a selected zone of interest. The location device, such as casing collar locator, senses the location of the actuatable tool based on a physical signature provided along the wellbore. The on-board controller or micro-processor is configured to send an activation signal to the actuatable tool when the location device has recognized a selected location of the tool based on the physical signature. The tool assembly further includes a multi-gate safety system. The safety system prevents premature activation of the actuatable tool.