Patent Application
20140251628
In a staged fracturing operation, multiple zones of a formation need to be isolated sequentially for treatment. To achieve this, operators install a fracturing assembly down the wellbore, which typically has a top liner packer, open hole packers isolating the wellbore into zones, various sliding sleeves, and a wellbore isolation valve. When the zones do not need to be closed after opening, operators may use single shot sliding sleeves for the fracturing treatment. These types of sleeves are usually ball-actuated and lock open once actuated. Another type of sleeve is also ball-actuated, but can be shifted closed after opening.
Initially, operators run the fracturing assembly in the wellbore with all of the sliding sleeves closed and with the wellbore isolation valve open. Operators then deploy a setting ball to close the wellbore isolation valve. This seals off the tubing string of the assembly so the packers can be hydraulically set. At this point, operators rig up fracturing surface equipment and pump fluid down the wellbore to open a pressure actuated sleeve so a first zone can be treated.
As the operation continues, operates drop successively larger balls down the tubing string and pump fluid to treat the separate zones in stages. When a dropped ball meets its matching seat in a sliding sleeve, the pumped fluid forced against the seated ball shifts the sleeve open. In turn, the seated ball diverts the pumped fluid into the adjacent zone and prevents the fluid from passing to lower zones. By dropping successively increasing sized balls to actuate corresponding sleeves, operators can accurately treat each zone up the wellbore.
When initially run downhole, the inner sleeve 30 positions in the housing 20 in a closed state. A breakable retainer 38 initially holds the inner sleeve 30 toward the upper sub 22, and a locking ring or dog 36 on the sleeve 30 fits into an annular slot within the housing 20. Outer seals on the inner sleeve 30 engage the housing 20's inner wall above and below the flow ports 26 to seal them off.
The inner sleeve 30 defines a bore 35 having a seat 40 fixed therein. When an appropriately sized ball lands on the seat 40, the sliding sleeve 10 can be opened when tubing pressure is applied against the seated ball 40 to move the inner sleeve 30 open. To open the sliding sleeve 10 in a fracturing operation once the appropriate amount of proppant has been pumped into a lower formation's zone, for example, operators drop an appropriately sized ball B downhole and pump the ball B until it reaches the landing seat 40 disposed in the inner sleeve 30.
Once the ball B is seated, built up pressure forces against the inner sleeve 30 in the housing 20, shearing the breakable retainer 38 and freeing the lock ring or dog 36 from the housing's annular slot so the inner sleeve 30 can slide downward. As it slides, the inner sleeve 30 uncovers the flow ports 26 so flow can be diverted to the surrounding formation. The shear values required to open the sliding sleeves 10 can range generally from 1,000 to 4,000 psi (6.9 to 27.6 MPa).
Once the sleeve 10 is open, operators can then pump proppant at high pressure down the tubing string to the open sleeve 10. The proppant and high pressure fluid flows out of the open flow ports 26 as the seated ball B prevents fluid and proppant from communicating further down the tubing string. The pressures used in the fracturing operation can reach as high as 15,000-psi.
After the fracturing job, the well is typically flowed clean, and the ball B is floated to the surface. Then, the ball seat 40 (and the ball B if remaining) is milled out. The ball seat 40 can be constructed from cast iron to facilitate milling, and the ball B can be composed of aluminum or a non-metallic material, such as a composite. Once milling is complete, the inner sleeve 30 can be closed or opened with a standard “B” shifting tool on the tool profiles 32 and 34 in the inner sleeve 30 so the sliding sleeve 10 can then function like any conventional sliding sleeve shifting with a “B” tool. The ability to selectively open and close the sliding sleeve 10 enables operators to isolate the particular section of the assembly.
When aluminum balls B are used, more sliding sleeves 10 can be used due to the close tolerances that can be used between the diameters of the aluminum balls B and iron seats 40. For example, forty different increments can be used for sliding sleeves 10 having solid seats 40 used to engage aluminum balls B. However, an aluminum ball B engaged in a seat 40 can be significantly deformed when high pressure is applied against it. Any variations in pressuring up and down that allow the aluminum ball B to seat and to then float the ball B may alter the shape of the ball B compromising its seating ability. Additionally, aluminum balls B can be particularly difficult to mill out of the sliding sleeve 10 due to their tendency of rotating during the milling operation. For this reason, composite balls B are preferred.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
As discussed previously, the sliding sleeve 100 can have a ball seat 120 disposed in the bore 132 of the inner sleeve 130 to engage a ball B. Moreover, the housing 110 may define flow ports 116 for passage of fluid out of the sleeve 100 when the inner sleeve 130 is moved to its lower position. The sliding sleeve 100 also includes various seals 134, shear screws (not shown), lock ring (136), and other common components, which may not be not depicted but would be present as will be appreciated.
As discussed previously, sometimes the ball B and seat 120 in the inner sleeve 130 need to be milled out. For example, the ball B may not dislodged from the seat 120 to be floated to the surface. In any event, a milling operation mills out the seat 120 and the ball B (if present) from the inner sleeve 130 so the sliding sleeve defines full bore 132 for operations. To facilitate this milling procedure, the inner sleeve 130 preferably does not rotate or at least inhibits its rotation so that the rotating drill bit used in the milling operation can be applied more directly to the seat 120 and ball B (if any).
As best shown in
Details of the inner sleeve 130 and its wedged cone 150 are further shown in
Scores 152 are defined at locations around the circumference of the wedged cone 150 and run along the length of the wedged cone 150. As shown, eight such scores 152 may be provided, but more or less may be used. The scores 152 can facilitate the press fit of the wedged cone 150 into the cupped shoulder (170) of the lower housing section (112b), as disclosed herein. Other than or in addition to the scores 152, the cone 150 can have knurled surfacing or other modifications to facilitate the press fit.
The inner surface 172 defines an angle (β) and press fits around the wedged cone (150) of the inner sleeve (130). The angle (β) may be about 1.5-degrees (±0.5-degrees), and the sidewall 172 may extend a distance of about 1-in. when the inner sleeve 130 is about 13-in. long. In fact, the sidewall 172 can have a 1-in. Morse taper #0. Other values can be provided for different implementations.
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter. Accordingly, features and materials disclosed with reference to one embodiment herein can be used with features and materials disclosed with reference to any other embodiment.
In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
