Wells – Submerged well – Means removably connected to permanent well structure
Reexamination Certificate
2000-09-20
2002-08-27
Schoeppel, Roger (Department: 3672)
Wells
Submerged well
Means removably connected to permanent well structure
C166S298000, C166S376000, C166S054600, C166S055800
Reexamination Certificate
active
06439313
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to the equipment and methods used in the completion of wells, such as oil and gas wells, and in particular to downhole machining of completion equipment.
BACKGROUND OF THE INVENTION
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation (i.e., a “reservoir”) by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be “completed” before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of tubulars, tools, and other equipment that are located in the wellbore for the purpose of conveying, pumping, or controlling the production or injection of fluids. The maintenance, operation, adaptability, and management of the completion must be considered as well. The completion of a well represents a complex technology that has evolved around the technique and equipment developed for this purpose.
Completion generally includes the installation of casing and one or more tubing strings in the wellbore, cementing, the installation of a variety of downhole equipment, such as packers and flow control devices, and in most cases perforating the casing to allow the hydrocarbons to flow from the formation into the wellbore. It is customary to install completion equipment that is particularly adapted for the specific well involved. Thus, commonly used types of completion equipment, such as landing nipples, packers, and flow control valves, are typically available in a variety of sizes and configurations, so that a particular size and configuration can be selected that will be best suited to work in the well in conjunction with the other equipment that is also installed in that well.
As a more specific example, as part of the completion practice, the control of fluid within the tubing and the flow of fluid from tubing to casing, or vice versa, is an important feature of flow control equipment. In order to properly construct a flow control system, any number of seating locations must be available in which the specified flow control devices can be installed. Landing or seating nipples are distributed throughout the tubing string as a method to locate and latch different flow control mechanisms. These nipples come with a variety of internal diameters and locking recesses in order to properly locate pre-selected equipment in place at the correct depth. When the desired tool is lowered into a well by wireline or the like, co-acting locking means on the tool can engage a corresponding locking recess on the landing nipple. Thus, by using a plurality of landing nipples in a well that have a different inner diameters as well as sizes or shapes of locking recesses, downhole tools can be selectively installed by matching the size and shape of the tool's locking means to the corresponding locking recess on the desired landing nipple. Significant planning is involved in specifying the correct nipple sequences so that the desired flow-control devices can reach their targets. In addition to the necessary planning, there is must be a substantial inventory of nipples in terms of style and quantity in order to provide an acceptable arrangement of the flow control system downhole. A method of completing wells that would allow more use of standard completion equipment would make the completion process less expensive and would reduce the need for inventories of many different sizes and configurations of a given type of downhole equipment.
Packers are one commonly used type of completion equipment. A permanent packer is preferred over a temporary removable packer under a variety of conditions, including potentially hostile environments in terms of pressure, temperature and fluid exposure. The packer is expected to be in the wellbore for long periods of time. The permanent packer has certain advantages in terms of capacity and functionality in comparison to other types of packers. However, the permanent packer is difficult to remove from the wellbore, and attempting to do so typically requires a milling operation to remove an anchor, which involves significant planning and time. There are also semi-permanent packers which can be placed in a well but can also be retrieved without milling and destroying the packer, thereby potentially allowing the packer to be reused. A need exists for improved methods of removing permanent packers from wellbores.
Downhole alteration of completion equipment has been used only on a limited basis in the past. One common downhole alteration is the use of a jet perforating gun to form holes in the well casing, and thus create a flow path for hydrocarbons to pass from the formation into the wellbore. Another such technique that has been used is to cut slots in well casing by lowering a jet nozzle into a well and pumping a fluid through the nozzle radially outward against the casing, at a high enough pressure to cut holes or slots in the casing. One embodiment of this technique is described in U.S. Pat. No. 4,134,453. The above-described uses of downhole cutting or perforation of well completion equipment have not eliminated the need for many sizes and configurations of equipment such as landing nipples, packers, and a variety of downhole tools.
In general, there is a long-standing need for simpler and less expensive methods of completing wells.
SUMMARY OF THE INVENTION
The present invention relates to a method of machining a workpiece in a subterranean wellbore. The method comprising the steps of: (a) providing a workpiece that comprises (1) a first section that comprises a first material, and (2) a second section that comprises a second material, the second section forming at least one surface of the workpiece; (b) placing the workpiece in a subterranean wellbore that is surrounded by a geologic formation; and (c) machining the workpiece to remove at least part of the second material in the second section, so that at least one surface of the workpiece is formed into a desired configuration.
In some embodiments of the invention, the machining in step (c) substantially destroys the second section of the workpiece. “Machining” in this context includes mechanical, electrical, and chemical techniques of removing material, as well as methods that involve combinations of these approaches. “Substantially destroys” in this context means that the second section is reduced to small particles that can easily be pushed out of the way by a downhole tool or by a flow of fluid. In essence, “substantially destroying” the second section removes that section as a fixed structure, so that mechanical or other operations may take place in the space that was previously occupied by that second section. In this embodiment of the invention, the destruction of the second section can allow the retrieval of the remainder of the workpiece (e.g., a permanent packer) from the wellbore.
In another embodiment of the invention, the workpiece is a tubular member (e.g., a landing nipple) having a hollow axial bore therethrough and an opening at each end. Preferably, the first section comprises an outer tubular member having a hollow axial bore therethrough and having a inner surface and an outer surface. It is also preferred that the second section comprises an inner tubular member having an inner surface and an outer surface, and that the outer surface of the inner tubular member is in fixed contact with the inner surface of the outer tubular member. In other words, the inner tubular member and the outer tubular member are connected in a fixed manner to form a combined tubular structure.
In an especially preferred embodiment of the invention, the inner surface of the inner tubular member is cylindrical and has a substantially uniform inner diameter along its axial length prior to the machining in step (c). In other words, the inner surface presents a smooth profile to any downhole tools that are lowered past that surface. The absence of sharp edges or a complex profile of indentations helps prevent downhole tools
Allcorn Marc
Costley James Michael
Eslinger David M.
Oettli Mark C.
Sheffield Randolph J.
Jeffery Brigitte L.
Ryberg John J.
Schlather Stephen
Schlumberger Technology Corporation
Schoeppel Roger
LandOfFree
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