1. Field of the Invention
The present invention relates to apparatus and methods for connecting two tubulars. Particularly, the present invention provides a locking means for a connection. More particularly, the present invention provides an apparatus and method of preventing a threaded connection from becoming unmade in a wellbore in response to rotational movement of the tubulars in a string of tubulars. More particularly still, the present invention relates to apparatus and methods for connecting tubulars together to produce a connection that has high bi-directional torque resistance.
2. Description of the Related Art
In order to access hydrocarbons in subsurface formations, it is typically necessary to drill a borehole into the earth. The process of drilling this borehole and of subsequently completing the borehole in order to form a wellbore requires the use of various tubulars.
Threaded connections are often used to connect multiple tubular members end-to-end and between tubular members that transmit torque. This is usually accomplished by providing tubulars that have a simple male to female-shouldered connection. The tubulars are connected, or “made up,” by transmitting torque against one of the tubulars while the other tubular is held stationary. Torque is transmitted in a single direction in accordance with the direction corresponding with connection make-up. Any torque applied to a joint in the make-up direction will have the effect of continuing to tighten the joint.
Problems are often encountered in wellbore operations wherein the tubular connections become disconnected. For example, rotation of the tubular string in the direction opposite of make-up creates a potential that one of the tubular connections can become disengaged if make-up torque is exceeded. More specifically, any torque applied in the direction opposite of make-up creates the potential that one or more of the tubular connections will start to unthread.
Methods have been employed to obtain bi-directional torque holding capabilities for connections. Some examples of these bi-directional setting devices include set screws, jam nuts, lock washers, keys, cross/thru-bolting, lock wires, clutches and thread locking compounds. However, these solutions have shortcomings. For example, many of these methods used to obtain bi-directional torque capabilities are limited by friction between component surfaces or compounds that typically result in a relative low torque resistant connection. For applications that require high bi-directional torque capabilities, only positive locking methods such as keys, clutches or cross/through-bolting are typically effective. Further, the high bidirectional torque connections identified above require both turning and milling operations to manufacture, which increase the cost of the connection over just a turning operation required to manufacture a simple male to female-threaded connection. The high bidirectional torque connections identified above also require significant additional components as compared to a simple male to female-threaded connection which adds to the cost.
There is a need therefore, for a locking arrangement between two threaded members that prevents movement between the members. There is a further need for a locking means that can be selectively installed in a threaded connection after the connection is made. There is yet a further need for a locking apparatus that prevents movement of the threaded parts of a connection in either of at least two directions. There is yet a further need for a connector for tubulars that does not require a separate, non-threaded component for locking. Further still, there is a need for a tubular connector capable of locking the tubulars together simply through rotational forces.