Drilling rig and method for introducing one or more drilling pipes into an underbalanced well using same

Abstract

A drilling rig includes a mast to be placed above or close to a well and a device connected to the mast for carrying drill pipes to be lowered into the well, which carrying device includes at least three carriers which are connected at different heights to the mast and displaceable in height direction therealong and which are adapted to exert a pulling force or a pressing force as required on the drill pipes.The upper carrier can have a device for rotatingly driving the drill pipes, while the lower carrier, which can be connected releasably to the mast, can have a flexible device for connecting thereof to a blowout preventer placed on the well.A method for introducing one or more drill pipes into an underbalanced well while making use of such a drilling rig includes suspending the drill pipe(s) from the carrying device and urging the pipe(s) downward into the well while exerting a pressing force.

Description

FIELD OF THE INVENTION[0001]The invention relates to a drilling rig, which may include a mast to be placed above or close to a well and a device connected to the mast for carrying drill pipes to be lowered into the well.BACKGROUND INFORMATION[0002]Such a drilling rig is generally known and is used to form wells at locations where oil or gas is present in the ground.[0003]The most characteristic component of a conventional drilling rig is the mast or derrick construction, generally a slender framework pyramid which is placed above the drilling location or erected thereon and which rests on a foundation adjacently of or around the drilling location. Arranged at the top of this mast is a hoisting gear with which drill pipes can be successively picked up from the ground at the front side of the mast and subsequently lowered in controlled manner into the well. The hoisting gear is situated some distance directly above the well.[0004]The conventional drilling rig is further provided with ...

AI Technical Summary

Benefits of technology

[0025]The carriers in the drilling rig according to example embodiments of the present invention are advantageously adapted to co-act during a “normal” drilling operation when the well is (over)balanced, wherein the upper carrier is adapted to lower drill pipes in a downward movement into the well, and the middle or lower carrier is adapted to take over and hold the drill pipes fixedly at the end of the downward movement. The drilling rig can thus be used conventionally in an overbalanced situation.

[0027]When the lower carrier has a flexible device for connecting thereof to a blowout preventer placed on the well, this prevents the construction of the well being loaded during operations in an underbalanced situation by downward directed forces occurring here.

[0037]In this method the drill pipe(s) are advantageously picked up and presented to the middle carrier by the upper carrier. Because the operations necessary for introducing the drill pipes are performed by the middle and lower carriers, the upper carrier and the space above the middle carrier do after all remain available for other operations, such as manipulation of drill pipes using the top drive, fastening together or, conversely, taking apart drill pipes, etc. Operation can hereby take place efficiently and safely.

Problems solved by technology

Due to the physical limitation of the drill pipes and the screwing required, the process of constructing a drill string is an interrupted process of placing and screwing on new pipes and subsequently lowering the whole drill string.

This cementing, which is required during the drilling process, has the effect of slowing production considerably during the production phase of the well.

The ultimate result hereof is a steadily increasing production loss.

This applies all the more because the process will also cause wear of the valves since the drill pipes are moved through them.

Since only atmospheric pressure is exerted on the portion of the drill string protruding from the well, the difference in pressure inside and outside the well will result in an upward directed force on the drill string.

Since a conventional drilling rig is only adapted to overcome the forces caused by the force of gravity, which are by definition directed downward, the upward directed forces caused by the well pressure cannot be controlled by the drilling rig.

In addition to the changed play of forces in the well and the consequences ensuing herefrom, it is no longer possible, due to the operation with closed blowout preventers, to move through the closed blowout preventer drill pipes with a form other than that for which the blowout preventer is designed.

Making the necessary changes to the system of blowout preventers, arranging the hydraulic workover unit in the conventional drilling rig are not only time-consuming and so expensive, but also involve an increased safety risk.

The number of separate components of the drilling rig can thus be limited.

This is important because handling of drill pipes on the rig floor is one of the most hazardous operations on and around a drilling rig.

The use of such units and the associated staff is expensive and results in long delays.

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