This invention relates to a tool for filtering debris in a well bore. More particularly, but not by way of limitation, this invention relates to a tool for filtering debris that can be retrieved, cleaned and/or replaced, and run back into the well bore for resetting.
In the course of drilling oil and gas wells, drill bit cuttings are produced. The drill bit cuttings are contained within the well bore fluid. Some of the drill bit cuttings will be separated at the surface, but despite these efforts, cuttings remain. Also, other debris such as pipe scale from the work strings can also become entrained in the well bore fluid.
Modern day drilling bottom hole assemblies have, in addition to a bit device, drill motors, measurement while drilling tools, and other components. Debris can cause the bottom hole assemblies to malfunction. This is particularly true in the case of measurement while drilling tools. Prior art devices have been devised in order to separate the debris within the well bore fluid. For instance, U.S. Pat. No. 6,598,685, entitled “Drilling Fluid Screen And Method” and issued to applicant, discloses a screen that can be used to separate debris from the fluid and is incorporated herein by reference. While this design has been successful, it would be desirable for a screen that would allow placement closer to the bottom hole assembly. Prior art screens have limited ability to be retrieved and later put back into the work string.
Additionally, with the use of prior art screens, erosion or flow cutting is a larger problem in down hole screens than in the equivalent surface screens being run at the top drive. The down hole erosion is caused in part by the breaking up of the laminar flow in the drill string during the filtering action from the screen. The laminar flow problem is not as prevalent at the surface due to the fact that flow has not had a chance to “straighten out” (from running through the pumps, elbows, Kelly, etc.) before filtering.
Therefore, there is a need for a device that can be used to effectively filter debris from a well bore. There is also a need for a device that can be retrieved from the well bore, and later run back into the work string and re-set within the work string for filtering. There is also a need to prevent down hole erosion of the screen apparatus. These and many other needs will become apparent from a reading of the following description.