System and method for plugging a downhole wellbore

A method for plugging a downhole wellbore including, running an anchor and swellable seal disposed at a mandrel within the downhole wellbore, setting the anchor within the downhole wellbore, releasing the anchor and the swellable seal, and swelling the swellable seal into contact with another downhole structure.

BACKGROUND

Well operators in the hydrocarbon recovery industry often seal tubulars to downhole wellbores such as casings and liners. Several systems exist for sealing the tubulars to the downhole wellbores and many function adequately. Most of these systems, however, include complex actuation devices. For example, many systems axially compress an elastomeric sleeve causing it to expand radially into sealing engagement with the downhole wellbore. This axial compression includes valves, pistons and actuators each having multiple moving parts and sliding seals that have potential failure modes associated therewith. Such systems are complex, costly and difficult to effectively deploy. Accordingly, the industry is receptive to simple, cost effective systems for plugging a downhole wellbore.

BRIEF DESCRIPTION

Disclosed herein is a method for plugging a downhole wellbore. The method includes, running an anchor and swellable seal disposed at a mandrel within the downhole wellbore, setting the anchor within the downhole wellbore, releasing the anchor and the swellable seal, and swelling the swellable seal into contact with another downhole structure.

Further disclosed herein is a downhole wellbore plugging system. The system includes, a mandrel that is runnable within a downhole wellbore and releasable therewithin, an anchor disposed at the mandrel being anchorable to the downhole wellbore, and a swellable seal disposed at the mandrel being sealable with the downhole wellbore and the mandrel.

Further disclosed herein is a method for plugging a downhole wellbore. The method includes, running a tool having an anchor and a swellable seal into the downhole wellbore with a wireline, anchoring the tool within the downhole wellbore, retrieving the wireline, and swelling the swellable seal into contact with another downhole structure subsequent to retrieval of the wireline.

DETAILED DESCRIPTION

Referring toFIG. 1, an embodiment of a wellbore plugging system disclosed herein is illustrated generally at10. The system10, among other things includes a downhole tool12having, a mandrel14with a swellable seal18and an anchor22mounted thereat. The tool12is positionable downhole within a wellbore26by a wireline28that is disconnectable from the mandrel14by a disconnectable connector30. The swellable seal18can be made of a variety of materials that swell when exposed to certain well fluids, such as hydrocarbons and water, for example. Additionally, the swellable seal18can swell in response to exposure to certain conditions that are commonly encountered in downhole environments, such as, high temperatures and high pressures as well as exposure to certain chemicals. The swellable seal18, can forcibly contact structures it comes in contact with in response to the increase in volume that occurs during swelling. Such contactable structures include walls32of the wellbore26, which may be a casing, liner or other tubular member, or open hole, or an outer surface34of the mandrel14, for example. These contact forces are sufficient to create a seal between the swellable seal18and the outer surface34as well as between the swellable seal18and the walls32. The swellable seal18can also be sealed to the mandrel14based on the original construction such that swelling of the swellable seal18is not needed to form the seal with the outer surface34. A duration of time needed from initiation of swelling to formation of a seal is dependent upon various factors, some of which will be reviewed below.

The swell rate, or the rate of increase in volume, of the swellable seal18, can vary depending upon a variety of parameters. For example, the chemical make up of both the swellable seal18itself and the well fluid into which the swellable seal18is submerged, can greatly affect the swell rate. Additionally, clearance dimensions between the swellable seal18and the surfaces32,34as well as the dimensions of the swellable seal18itself will also affect the time required to form a seal. Typically, the greater the clearance the longer the duration before a seal is formed. A designer can, therefore, use these parameters to set a desired time duration from initiation of swelling to initiation of sealing. Delay in swelling to the point of sealing may be desirable to allow time for an operator to run the tool12into the desired position downhole prior to forming a seal with the walls32, for example. Such delays may be set from just a few hours to several days or more.

In embodiments of the invention, an operator will set the anchor22prior to forming the seal. The anchor22has slips44that are deployable and engagable with the walls32of the wellbore26to fixedly attach the system10to the wellbore26. Although the system disclosed herein has the anchor22positioned above the swellable seal18, along the mandrel14, alternate embodiments could just as well have the anchor22positioned below the swellable seal18. Regardless of the relative positions of the anchor22with the swellable seal18, initiation to actuate the setting of the anchor22can be carried out in various ways.

For example, setting of the anchor22can be initiated, and optionally actuated, from surface via the wireline28. The wireline28can be used to initiate a trigger36that actuates an actuator40, or the wireline28can be used to actuate the actuator40directly. For example, in embodiments wherein the wireline28is an electric wireline28an electrical signal could be transmitted along the wireline28and used to open a valve (the trigger36) that permits downhole fluid under hydrostatic pressure access to a chamber containing a piston and a compressible gas at atmospheric pressure, to thereby move the piston (the actuator40) to set the anchor22. In an alternate embodiment, the electrical transmission can be used to energize a motor (the trigger36) that drives a pump (the actuator40) to hydraulically set the anchor22. Still other embodiments, of the system10, could employ timing devices (the trigger36), or other means, that initiate actuation in response to exposure to a specific downhole parameter, such as, elevated pressure, elevated temperature and chemical exposure, for example.

Regardless of the trigger36and the actuator40employed to set the anchor22, the anchor22should be set prior to setting of the swellable seal18. In embodiments wherein the swellable seal18begins swelling as soon as it is exposed to certain downhole conditions, the duration to set the swellable seal18needs to be longer than the time it will take to run the tool12to the desired depth. This will prevent rubbing damage due to excess friction between the swellable seal18and the walls32while the tool12is being run. Once the tool12is in position the swelling of the swellable seal18can continue until a seal is formed.

Optionally, an operator is free to disconnect the wireline28from the tool12, at the disconnectable connector30, once the anchor22is set, even if the swellable seal18has not yet sealingly engaged the walls32. As such, a swellable seal18that takes several days to fully swell and seal with the walls32may be a desirable condition to assure that the operator has adequate time to fully run the tool12to the desired depth. It may be advantageous to position the disconnectable connector30between the actuator40and the anchor22to thereby allow an operator to remove the trigger36and the actuator40with the wireline28thereby minimizing a portion of the tool12that remains downhole.

The foregoing embodiments allow a well operator to quickly and inexpensively run the tool12with the wireline28to a position within the wellbore26, set the anchor22and then retrieve the wireline28and then wait for the swellable seal18to permanently plug off the wellbore26. Since it is not uncommon for wells to water out from the bottom up, several of the tools12could be used in a single well to sequentially plug off zones from the bottom up as they begin producing water.