Patent Application
20050039917
This invention generally relates to inflatable packers used to complete subterranean wells and in particular to hydraulically actuated inflatable packers. More specifically, this invention relates to hydraulically actuated inflatable packers that are inflated by a fluid filtered from a gravel laden slurry or other fluid with suspended solids.
Oil and natural gas may be obtained from subterranean geologic formations, referred to as reservoir, by drilling wells that penetrate hydrocarbon-bearing formations. In order to obtain hydrocarbons from a wellbore, the well usually must be completed.
Well completion involves the design, selection, and installation of equipment and materials in or around a wellbore for conveying, pumping, or controlling the production or injection of fluids from and/or to the wellbore. After a well has been completed, production of oil and gas may begin. Sand or silt flowing into the wellbore from unconsolidated formations may lead to an accumulation of fill within the wellbore which may cause a reduction of production rates and damage to surface and subsurface production equipment. The fill, often referred to as migrating sand, has the possibility of packing off around subsurface production equipment, or may enter the production tubing and therefore enter production equipment. Sand is highly abrasive, and if it enters production streams, it may cause the erosion of tubing, flowlines, valves and other processing components and equipment. Erosion and abrasion caused by sand production often increases operational and maintenance expenses, and in severe cases may lead to a total loss of the well. Gravel packing is a means of controlling sand production. Gravel packing is the placement of relatively large sand (i.e., “gravel”) around the exterior of a sand screen or liner, which includes slotted sand screens, perforated sand screens, and various other liner types and screens. The gravel acts as a filter to remove formation fines and sand from oilfield fluids.
A gravel pack completion known in the art comprises a sand screen that is placed in the wellbore and positioned within an unconsolidated formation. The sand screen may be connected to a tool that includes a production packer and a cross-over. The tool is connected to a work string or a production tubing string. Gravel is then pumped in a slurry down the tubing and through the cross-over, thereby flowing into the annulus between the sand screen and the wellbore. The slurry comprises a liquid supporting suspended solids. The solids are often referred to as “gravel”. The liquid leaks off into the formation and/or through the sand screen, which is sized to prevent the solids in the slurry from flowing through. Thus the solids are deposited in the annulus around the sand screen where it forms a gravel pack. The sand screen prevents the gravel pack from entering into the production tubing. The gravel must be sized for proper containment of the formation sand, and the sand screen must be designed in a manner to prevent the flow of the gravel through the sand screen.
Often during well completions there is a need to seal off sections of the wellbore. One reason to seal off a section of a wellbore is the need to isolate those areas in which an adequate gravel pack can not be obtained, such as below the bottom of the gravel pack screens where adequate circulation is difficult to achieve. Another reason to seal off a section of a wellbore is that in some formations, such as across a major or minor shale section, a gravel pack completion is not desirable. Still another reason to seal off a section of a well bore is because when one or more sections are to be completed and another section is not going to be completed, the non-completed section often needs to be isolated from the sections that will be completed. This is due to the fact that when non-completed sections are not isolated, the gravel, which is tightly packed around the gravel pack screens after a gravel pack, may be able to migrate to these non-completed sections, thereby limiting the effectiveness of the gravel pack completion. Another reason to isolate a section of the wellbore is to prevent or limit acceleration of the gravel migration effect due to the flow of produced fluids. Sand screens exposed to gravel migration due to the flow of produced fluids may experience direct production of formation sand which could result in equipment damage, formation collapse and even the loss of the well.
Well known in the art are inflatable packers, usually comprising an annular elastomeric bladder, which have been used to seal off sections of wellbores for the reasons discussed above. When the bladder is filled by a by a pressurized fluid, it inflates the packer causing the exterior of the elastomeric body to seal against the wellbore. This produces a wellbore seal that prohibits fluid flow past the packer.
A problem with inflatable packers known in the art is the difficulty of sending fluid to the bladder to inflate the bladder. The time consumed in using known inflatable packers includes the time needed for an extra step either prior to the gravel pack step or after the gravel pack step to send a specialized tool down the wellbore to inflate the packer.
Thus, there is a need for an improved inflatable packer which reduces the known problems in sending fluid to the bladder to inflate the bladder, and eliminates the need for an extra step either prior to or after a gravel pack to inflate the bladder.
The present invention describes tools and methods of completing a wellbore that comprise an isolation packer with a particulate filter and inflatable element. The isolation packer is adapted to direct a gravel laden slurry to the particulate filter, where the filter removes a substantial amount of the particulate matter from the gravel laden slurry thereby producing an inflating fluid that is substantially free of particulate matter. The inflating fluid then inflates the inflatable element thus creating a seal in the wellbore.
This invention offers a number of benefits over conventional wellbore completion tools. Usually a pre-gravel pack trip would be undertaken to isolate a sump area, for instance, with a cement plug or an open hole packer. This pre-gravel pack trip comprise additional steps that are costly, time consuming and are often difficult to perform and unreliable in their outcome. The present invention provides a means of achieving the desired results in the same trip into the well as the gravel pack operation. The ability to inflate the inflatable isolation packer during a gravel pack completion can save time and expense by eliminating an additional trip into the well.
The above advantages as well as specific embodiments will be understood from consideration of the following detailed description taken in conjunction with the appended drawings in which:
References in the detailed description correspond to like references in the figures unless otherwise indicated.
Referring to the attached drawings,
The present invention can be utilized in both cased wells and open hole completions, as well as vertical wells and non-vertical wells. For ease of illustration of the relative positions of the producing zones in
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An area that is prone to developing a void during a gravel pack operation is the area 42 below the lowest sand screen element 28, sometimes referred to as the “sump”. A gravel pack void in the sump 42 is particularly problematic in vertical wells in that it can allow the gravel from above to settle and fall into the voided sump.
Production of fluids from the productive formation 14 can agitate or “fluff” the gravel pack and initiate the gravel to migrate and settle within the sump 42. This can lead to the creation of voids in the annulus areas 38 adjacent to the sand screen elements 28 and undermine the effectiveness of the entire well completion.
As used herein, the term “sand screen” refers to wire wrapped screens, mechanical type screens and other filtering mechanisms typically employed with sand screens. Sand screens need to be have openings small enough to restrict gravel flow, often having gaps in the 60-12 mesh range, but other sizes may be used. Sand screens of various types are produced by Halliburton, among others, and are commonly known to those skilled in the art.
Between the conduit 52 and the gravel inflated isolation packer 50 is a particulate filter 54. Likewise, a particulate filter 59 is placed between conduit 53 and the isolation packer 50. In this way, either or both of the conduits 52, 53 allow gravel laden slurry to travel from the annulus area 38 to the particulate filters 54, 59 where the gravel laden slurry is filtered, thereby providing an inflating fluid. The inflating fluid is then communicated to an inflatable element 56 that provides the sealing mechanism between the tubular member 22 and the casing 16. The inflatable element 56 may be an expandable bladder. The particulate filter 54 could be any device known in the art that separates the particulate matter in the gravel laden slurry from the carrying fluid. Some examples of particulate filters include, but are not limited to: wire-wrapped screens and wire meshes.
A conduit, such as conduit 52 and/or conduit 53, is just one way of enabling the communication of the gravel laden slurry to enter the inflatable isolation packer 50. Other embodiments can be used, such as connecting the inflatable isolation packer 50 to a flow channel which is integral to the screen, or a shunt tube. All of these embodiments would include a particulate filter to prevent particulates such as gravel from entering the inflatable element 56. In addition, all of these embodiments may include a check valve device to prevent any reverse flow out of the inflatable isolation packer 50.
The inflation of the inflatable element 56 will typically be done with a fluid that is filtered from a gravel laden slurry. This fluid will be an inflating fluid that is substantially free of particulates such as gravel. The inflation of the inflatable element 56 can be performed in conjunction with a gravel pack completion operation of the well.
The inflatable element 56 may be constructed utilizing an inner elastomeric element that retains the pressurized fluid that is used to inflate the packer. The inflatable element may comprise more than one layer of material, such as utilizing an expandable mesh as an outer layer for durability. Often a plurality of metal reinforcing members can be located in the annulus between the elastomeric element and the outer expandable mesh, these provide additional strength to the packer and can improve reliability. The typical construction can be in the manner of conventional packers, these methods and materials being well known to those skilled in the art.
For ease of installation and to ensure proper placement relative to the components of the well tool 20, the conduit 52 that extends from the inflatable isolation packer 50 will typically be attached to the exterior of the well tool 20 in some manner, such as by welding. It is also possible for the conduit 52 to be replaced by a fluid pathway forming an alternative channel within a sand screen element, as described with respect to
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The inflatable isolation packer 50 acts to isolate a first zone from a second zone within the well. In
In another embodiment the invention may be placed below the lowest perforation or at the bottom of the well. This embodiment may be used to isolate the lower areas from the completed zones without permanently reducing the total depth of the well. Thus, the well could be functionally plugged back to where the inflatable isolation packer was located and leaving open the option of removing the inflatable isolation packer for the completion of deeper zones in the future.
The discussion and illustrations within this application may refer to a vertical wellbore that has casing cemented in place, or is an openhole bore, and comprises casing perforations to enable communication between the wellbore and the productive formation. It should be understood that the present invention can also be utilized with wellbores that have an orientation that is deviated from vertical.
The particular embodiments disclosed herein are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
