Boring or penetrating the earth – Below-ground impact members – Fluid-operated
Patent
1999-04-30
2000-12-26
Schoeppel, Roger
Boring or penetrating the earth
Below-ground impact members
Fluid-operated
175305, 173 3, 173177, 173204, E21B 414
Patent
active
061643939
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic impact tool for use in a well, such as an oil or gas well, in particular to apply impact energy to a stuck object in order to get the object loose or break it.
Impact tools are often used in connection with operations, in which valves, measuring equipment and other equipment is to be anchored down in a well. An impact tool is attached as an extension of a pipe string, for example a drill string or coiled tubing, and equipment to be placed in the well is attached to the free end of the impact tool. The impact tool has a channel extending therethrough, so that fluid may pass. The equipment to be set in the well, may be provided with grippers, resilient lugs or other things which engage grooves or seat surfaces provided in the wall of the well. To ensure that the equipment does not become detached, it is often provided with a locking device which is activated through the shearing of a shear pin. In some cases the pipe string cannot transfer sufficient mechanical force to break the shear pins, and the shear pins may then be broken by means of an impact tool. Also, the impact tool is often provided purely as a precaution to make it possible to get the equipment loose in case it should get stuck.
In a hydraulic impact tool a movable, maybe sleeve-shaped hammer is biased towards a stop by means of an outer spring. A stroke is made by displacing the hammer from the stop, and then let the pre-tensioned spring drive the hammer back to the stop.
The hammer has a hydraulic piston arranged thereto, provided with a through passage in which a valve is provided. The valve is normally open, so that fluid may pass through the piston. By activating the valve and closing the through passage, the piston is displaced, and thereby the hammer is displaced from the stop when pressurized fluid is applied to it. At the same time the spring is further tensioned because of the movement of the hammer.
As the hammer reaches an end position, the valve is opened, so that fluid again may flow through the piston. The hydraulic force against the piston then quickly drops, and the spring drives the hammer (with the piston) back towards the stop. The valve is activated and then again closes the through passage in the piston, and the process is repeated.
SUMMARY OF THE INVENTION
It is known to use a spring, which can be prestressed from outside, to drive the hammer. Further, it is known to arrange said spring so, that it may be prestressed either through pulling at the pipe string in the direction away from the impact tool, or through pushing the pipe string in the direction towards the impact tool. Applied to an impact tool in a vertical position, the impact tool may then provide respectively upward and downward strokes, as the impact tool may comprise two separate valve mechanisms for upward and downward strokes respectively. Such impact tools are generally said to be double-acting. The magnitude of the impact force is changed by varying the prestressing of the spring.
It is common for said hydraulic valves activating the impact tool, to be influenced by the biasing of the spring. If the spring is in a neutral position, fluid may be pumped through the pipe string without the impact tool being activated. By applying a biasing to the spring, upwards or downwards, as mentioned, the impact tool is activated by a sealing body being brought to seal against through-put of fluid. This results in a pressure build-up, and the resulting hydraulic force displaces the hammer to a stroke start position.
In known impact tools the valve in the piston is activated, so that the through passage is closed by the hammer being carried to the start position towards the stop. Load of equipment hanging from the impact tool is often sufficient for exactly this to happen. This leads to fluid circulation through the pipe string being impossible as the impact tool is being inserted or withdrawn from the well without activating the impact tool. If circulation of long duration is required, said eq
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Bakke Technology AS
Schoeppel Roger
LandOfFree
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