Assembly for toe-to-heel gravel packing and reverse circulating excess slurry
A treatment assembly treats zones of a horizontal borehole. For example, the assembly can gravel pack a zone by delivering slurry down a workstring. The slurry exits the workstring's outlet and pass to the borehole annulus of the zone through a flow port in the assembly. The gravel in the slurry can pack the borehole in an alpha-beta wave from toe to heel, and the fluid returns from the borehole flow through a screen back into the assembly. After gravel packing, operators remove excess slurry from the workstring by reverse circulating down the assembly to carry the excess slurry uphole through the workstring. Closures on the assembly prevent the reverse circulation from communicating through the screens to the borehole annulus. Additionally, flow valves can be used on the flow ports to selectively open and close them.
1. A formation treatment method for a borehole, the method comprising:
isolating a borehole annulus of the borehole around an assembly into a plurality of isolated zones, the assembly in each isolated zone having a first port and a screen communicating a through-bore of the assembly with the borehole annulus, the first port having a first closure selectively operable between opened and closed conditions, the screen having a check valve permitting fluid communication from the screen to a second port of the through-bore and preventing fluid communication from the second port to the screen;
positioning a workstring in the through-bore of the assembly; and
treating the borehole annulus of any selected ones of the isolated zones by:
opening the first closure at the first port of the selected isolated zone with the workstring;
sealing an outlet of the workstring at the first port of the selected isolated zone;
flowing slurry as a treatment down the workstring, out the outlet, and to the first port;
gravel packing the borehole annulus of the selected isolated zone from toe to heel with gravel in the slurry;
filtering fluid returns of the slurry from the borehole annulus of the selected isolated zone into the through-bore of the assembly through the screen and through the check valve at the second port;
flowing the filtered returns from the selected isolated zone uphole through the through-bore of the assembly by flowing the filtered returns directly from the check valve up the through-bore and preventing flow of the fluid returns in the through-bore from flowing back to the borehole annulus out through the first closures and the check valves of the other isolated zones uphole on the assembly, wherein the filtered returns flow to surface without passing through a bypass of the through-bore; and
removing excess of the treatment from the workstring by:
sealing the outlet of the workstring from the open first closure of the first port at the selected isolated zone,
reverse circulating down the through-bore of the assembly and into the outlet of the workstring, and
preventing the reverse circulation in the through-bore from communicating to the borehole annulus out through the check valve of the selected isolated zone and out through the first closures and the check valves of the other isolated zones.
2. The method of claim 1 , comprising initially positioning the assembly in casing having perforations, in an expanded liner having slots, or in an open hole.
3. The method of claim 2 , wherein isolating the borehole annulus of the borehole around the assembly into the isolated zones comprises engaging isolation elements on the assembly against a wall of the casing, a wall of the expanded liner, or a wall of the open hole.
4. The method of claim 1 , wherein opening the first closure at the first port in the assembly at the selected isolated zone with the workstring comprises shifting a sleeve in the assembly away from the first port with the workstring.
5. The method of claim 1 , further comprising closing the first closure at the first port at the isolated zone with the workstring after treatment.
6. The method of claim 1 , wherein treating the selected isolated zone comprises:
flowing the slurry as the treatment from the first port disposed toward the toe,
gravel packing the annulus of the selected isolated zone from toe to heel, and
filtering the fluid returns into the through-bore of the assembly through the screen disposed toward the heel.
7. The method of claim 1 , further comprising preparing the isolated zones for production by:
closing the first closures at the first ports of the assembly at the isolated zones with the workstring; and
permitting fluid communication from the borehole annulus into the through-bore through the screens, the check valves, and the second ports at the isolated zones.
8. The method of claim 7 , further comprising screening production fluid from the borehole annulus of the isolated zones into the through-bore of the assembly through the screens, the check valves, and the second ports.