Indexing Mechanism that Removes Transition Zone of Pressure Cycle Counting Mechanisms
Publication Date: 2012-Jun-12
The IP.com Prior Art Database
The present disclosure relats to a control mechanism for a downhole indexing sytem wherein the system is not allowed to move backwards once it passes a critical position.
Title of Invention: Indexing Mechanism that Removes Transition Zone of Pressure Cycle Counting Mechanisms
SUMMARY OF THE INVENTION
Isolation Valves with remotely operated “trip saving” devices are generally used in applications where intervention is expensive (such as off shore completions). The trip saving devices are operated by applying surface pressure cycles increasing the tubing pressure. A downhole mechanism is used to count the cycles and actuate the Isolation Valve on the proper cycle. As tubing pressure is applied a piston must cycle against a downhole reference pressure to index the counter. One such iteration of the counter is shown in figure 1 below. In this case, a pin is used to rotate a slotted mandrel. Each time the piston strokes down and then up the mandrel rotates and counts a cycle. When the mandrel reaches a specific number of cycles the indexer uses a longer slot to allow the piston to move a larger distance and activate the trip saving mechanism. Displacement based mechanical counters have a critical transition where reversing the direction of motion can cause the system to index either backward or forward, shown in figure 1. This can lead to accidental cycles where the actual cycle count can be different than the perceived cycles counted by an operator. This invention adds a control to the sequence which will not allow the indexer to move backward once a minimum position is reached. Figure 2 shows a Pressure vs. Time curve...