Downhole packer assembly having an auto-retraction mechanism
A downhole packer assembly may include an outer wall, an inflatable bladder, at least one coupling element, and at least one auto-retraction mechanism. The inflatable bladder may be configured to cause the outer wall to expand radially outwardly. The at least one coupling element may be mechanically coupled radially with the outer wall. The at least one auto-retraction mechanism may be configured to mechanically assist the outer wall to retract radially inwardly when the inflatable bladder is deflated from an inflated configuration toward a deflated configuration. The auto-retraction mechanism may include a chassis and a plurality of pistons, each piston having one end coupled to the chassis and another end coupled to a coupling element.
1 . A downhole packer assembly having an axis and comprising:
an outer wall;
an inflatable bladder configured to cause the outer wall to expand radially outwardly, the inflatable bladder having a first diameter in a deflated configuration and a second diameter in an inflated configuration, the second diameter being greater than the first diameter;
at least one coupling element mechanically coupled radially with the outer wall; and
at least one auto-retraction mechanism configured to mechanically assist the outer wall to retract radially inwardly when the inflatable bladder is deflated from the inflated configuration toward the deflated configuration, the auto-retraction mechanism comprising a chassis and a plurality of pistons, each piston having one end coupled to the chassis and another end coupled to a coupling element of the at least one coupling element.
2 . The downhole packer assembly according to claim 1 , wherein the outer wall has at least one drain, the downhole packer assembly comprising two end pieces defining two axially opposed ends of the downhole packer assembly, the outer wall and the inflatable bladder being disposed axially between the two end pieces; and at least one of the at least one coupling element being a flowline in fluid communication with the at least one drain and with at least one of the end pieces.
3 . The downhole packer assembly according to claim 1 , comprising two axially opposed mandrels defining axial ends of an inner chamber of the inflatable bladder, the chassis of the auto-retraction mechanism surrounding one mandrel of the axially opposed mandrels radially and being mechanically uncoupled with the one mandrel.
4 . The downhole packer assembly according to claim 1 , wherein the chassis comprises at least one ring provided with a plurality of clevises, each clevis being coupled to at least one piston of the plurality of pistons.
5 . The downhole packer assembly according to claim 1 , wherein each piston comprises a cylinder having a chamber and a rod slidingly received within the chamber and configured to move between an extended position and a retracted position, the rod having a diameter substantially equal to a diameter of the chamber.
6 . The downhole packer assembly according to claim 1 , wherein each piston comprises a cylinder having a chamber, a rod slidingly received within the chamber and configured to move between an extended position and a retracted position, and a stop mechanism configured to limit extension of the rod to a predetermined length in the extended position, the stop mechanism comprising a sliding shaft received within an open sliding path arranged outside the chamber of the cylinder.
7 . The downhole packer assembly according to claim 6 , wherein the sliding shaft and the open sliding path have complementary abutment surfaces configured to abut against each other in a sliding direction of the sliding shaft, the abutment surfaces being bevelled with respect to the sliding direction of the sliding shaft.
8 . The downhole packer assembly according to claim 1 , wherein each piston is a passive piston comprising a cylinder having a chamber and a rod slidingly received within the chamber and configured to move between an extended position and a retracted position, the chamber being pressurized at an atmospheric pressure when the rod is in the retracted position.
9 . The downhole packer assembly according to claim 1 , wherein each piston has a rod having a diameter, the diameter of the rod being between 3.50 mm and 4.00 mm.
10 . The downhole packer assembly according to claim 1 , wherein the first diameter is between 150 mm and 260 mm and the second diameter is between 220 mm and 390 mm.
11 . The downhole packer assembly according to claim 1 , wherein the auto-retraction mechanism comprises an even number of pistons, the pistons are grouped in pairs, each pair of pistons is regularly distributed about the axis, and the pistons of each pair of pistons are coupled to a same coupling element of the at least one coupling element and extend circumferentially on opposite sides of the same coupling element.
12 . The downhole packer assembly according to claim 1 , wherein the auto-retraction mechanism comprises four pistons or eight pistons.
13 . The downhole packer assembly according to claim 1 , wherein the at least one auto-retraction mechanism comprises two auto-retraction mechanisms disposed on opposite axial sides of the inflatable bladder.