Patent Application
20120048560
The field of the invention is debris cleanup tools for subterranean locations and more particularly to a device attached to the lower end of such tools, regardless of their flow patterns that maintain the tool out of the dense debris as the debris is collected to avoid loss of collection efficiency.
Milling operations at subterranean locations involve fluid circulation that is intended to remove cuttings to the surface. Some of these cuttings do not get transported to the surface and settle out on a wellbore support such as a packer or bridge plug that is below. In open hole situations the wellbore can collapse sending debris into the borehole. Over time sand and other debris can settle out on a borehole support and needs to be removed for access to the support or to allow further subterranean operations.
Wellbore cleanup tools have been used to remove such debris. Different styles have developed over time. In a traditional style the motive fluid goes through the center of the tool and out the bottom to fluidize the debris and send the debris laden stream around the outside of the tool where a diverter redirects flow through the tool body. A receptacle collects the debris as the clean fluid passes through a screen and is discharged above the diverter for the trip to the surface.
Another type of tool has a jet stream going downhole outside the tool to drive debris into the lower end of the tool where debris is collected and clean fluid that passes through a screen is returned to the surface outside the tool through ports located near the downhole oriented jet outlets. The jet outlets act as an eductor for pulling in debris laden flow into the lower end of the tool. Some examples of such tools are U.S. Pat. Nos.: 6,176,311; 6,607,031; 7,779,901; 7,610,957; 7,472,745; 6,276,452; 5,123,489.
One operating problem of such tools is that if they are lowered too fast or too much the lower end can penetrate the upper surface of the accumulated debris. When this happens, the efficiency of the debris collection is greatly diminished. Currently the crew at the surface has some idea of the location of the debris and lowers the cleanup tool to the expected debris location. The way that the crew determines when the debris is reached is the weight indicator. When the string finds support the indicated weight is reduced on the surface weight indicator. However, if the surface personnel is not attentive or lowers the debris removal tool too fast they may not be aware that it is embedded in debris and collecting virtually none of it.
Ideally, the debris removal tool should give an indication of its arrival at the top of the debris pile before the collection tool is embedded in the debris zone. The nature of the debris filled zone is that there is a rather firm top coating on the debris pile. Once that top coating is removed through the removal tool circulation patterns, the balance of the debris becomes somewhat fluidized. The present invention adds a lower end device that initially contacts the top of the debris pile and can somewhat embed into it while giving a weight signal at the surface while at the same time providing side openings that are large enough to allow the needed circulation for debris pickup. The device can be telescoping nested tubes that are extended with the pressure from circulation flow. There can be a bias toward the minimum telescoped dimension when there is no pressure available from circulation. As debris collection continues the surface personnel can control the process with the brake so that the downward movement of the tool can be regulated to the rate that the debris is removed. Another option is to put sensors that measure the amount of extension of the telescoping assembly and transmit that information to the surface. The surface personnel can then work the brake to control the amount of telescoping assembly extension to provide the optimum spacing of the collection tool to the top of the heap of debris. The lateral outlets can be in the lowest telescoping component and the lowest component can be tall enough above the top ends of the lateral slots so that some telescoping of the next higher tubular will not reduce the area of the lateral slots in the lowest telescoping component. These and other aspects of the present invention will be more readily apparent from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
A spacing device is located on a lower end of a debris removal tool. Circulation through the tool extends telescoping members to the top of the debris zone against a bias that retracts the members when there is no flow through the tool. The lowest telescoping member has peripheral slots through which the circulation for the tool takes place. The landing of the tool on top of the debris can be detected by the weight indicator at the surface. The device prevents embedding the lower end of the tool into the debris. Instruments can also determine the scope of the telescoping extension and transmit that value to the surface so that the cleanup tool can be continuously spaced from the moving top of the debris pile by maintaining a target distance for extension of the telescoping assembly.
A more elaborate control scheme is shown schematically as a sensor S and a way of transmitting the signal to the surface, shown schematically as arrow 66. The sensing can be of the amount of extension of the assembly 42. In that case the surface personnel can target maintaining the extension at some level below maximum and well above the minimum extension. In doing that the proper extension of the assembly 42 is maintained. The signal to the surface can be on wire or fiber optic or control line, to name a few possibilities. The sections 44, 46 and 48 can also be driven such as with a motor and a rack and pinion system although greater simplicity is always preferred for enhanced reliability. Preferably at the minimum dimension the slots 50 will not be obstructed by the sections 44 and 46.
Those skilled in the art will appreciate that the device 42 in the various alternatives described is used to properly distance the tool 10 that is preferably a debris removal tool from the top of the pile of debris to be collected so that the tool functions more optimally. The operation of the device 42 can be regulated from either watching the weight indicator at the surface or from getting a surface signal as to the degree of extension of the assembly as the debris removal progresses and as the tool 10 is allowed to advance by the surface crew. The device 42 can telescope by pressure from circulation or collapse by set down weight or a spring bias that operated when there is no flow to urge telescopic extension. The components can be mechanically extended or retracted with appropriate instrumentation to avoid overstressing a driver such as a motor connected to, for example, a pinion that engages a rack on the various components.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
