A downhole apparatus comprises a housing, a seat mounted in the housing and configured to receive an object such that the object may engage and axially move the seat to operate the downhole apparatus, and a moveable barrier located on one axial side of the seat such that when an object is engaged with the seat a volume is defined between the object and the moveable barrier, wherein the moveable barrier permits said volume to be moved within the apparatus to allow the object to axially move the seat.

A stage cementing system includes a stage cementing assembly having a stage tool. The stage tool has an outer mandrel, an inner mandrel coupled to and disposed inside of the outer mandrel, an annular chamber between the outer mandrel and the inner mandrel, a first outer port through the outer mandrel, and longitudinally spaced first and second inner ports through the inner mandrel. The stage cementing system further includes an inner string assembly configured to be located inside the inner mandrel. The inner string assembly has a tubular body having a central throughbore and longitudinally spaced first and second side ports, a lower external seal element below the first and second side ports, a middle external seal element between the first and second side ports, and an upper external seal element above the first and second side ports.

Methods, systems, and computer program products for generating a schedule for fluid placement. A computer-implemented method may include determining, for each zone of a plurality of zones of a treatment interval to be treated by the fluids placement system, a criterion value based on a heterogeneity parameter of the zone, sorting the zones into an ordered sequence based on the criterion value associated with each zone, and generating a schedule that designates an order of treating the zones in accordance with the order of the sequence.

A method for temporary isolation of a well interval is proposed, the method comprising: pumping a first slurry into the well, the slurry comprising a viscous carrier fluid, degradable particulates, and degradable fibers, until a first filter cake is formed; and pumping a second slurry into the well, the slurry comprising a viscous carrier fluid, non-degradable particulates, and degradable fibers, until a second filter cake is formed. The first and the second slurries are not mixed when pumped into the well. To ensure optimum interval isolation, the ratio of the volume of the first slurry to the volume of the second slurry should be in the range 1:5 to 2:1. A method for hydraulic refracturing within an interval with several hydraulic fractures and a non-damaging well killing method are also proposed. The technical result is manifested in no formation damage and degradation of the sealing layer formed.

Systems and methods for cementing an annular space radially outward of a casing of a subterranean well include a float shoe located at a downhole end of the casing. A float valve is located within the float shoe and within a fluid flow path extending through the float shoe from an internal bore of the casing to an exterior surface of the float shoe. At least two wing members are located on an outer diameter surface of the casing, each of the wing members extending from the float shoe to an uphole end of the casing. The wing members are sized to define two or more separate sections of the annular space. A downhole splitter is located on a downhole surface of the float shoe. The downhole splitter is sized to seal between the downhole surface of the float shoe and an end surface of the subterranean well.

A stage cementing tool for use in a wellbore comprises a mandrel having a plurality of circumferentially spaced first longitudinal slots and a plurality of circumferentially spaced second longitudinal slots. An opening sleeve is disposed in the mandrel in a first position and movable relative thereto. A setting sleeve disposed about the mandrel is connected to the opening sleeve and movable therewith. A drive sleeve is disposed in the mandrel above the opening sleeve is connected to and movable with a closing sleeve disposed about the mandrel.

A stage tool assembly has a tubular body defining an interior bore with a port; an opening sleeve axially movable from a first position that restricts the port to a second position that exposes the port; a closing sleeve axially movable from a first position that exposes the port to a second position that restricts the port; and an isolation assembly downhole of the port that, at least when in an activated mode: permits tool passage in a downhole direction through the interior bore; and restricts flow through the interior bore.

A stage cementing system includes a stage cementing assembly having a stage tool. The stage tool has an outer mandrel, an inner mandrel coupled to and disposed inside of the outer mandrel, an annular chamber between the outer mandrel and the inner mandrel, a first outer port through the outer mandrel, and longitudinally spaced first and second inner ports through the inner mandrel. The stage cementing system further includes an inner string assembly configured to be located inside the inner mandrel. The inner string assembly has a tubular body having a central throughbore and longitudinally spaced first and second side ports, a lower external seal element below the first and second side ports, a middle external seal element between the first and second side ports, and an upper external seal element above the first and second side ports.

A stage cementing tool has a mandrel defining a central flow passage and a plurality of fully open cement flow ports. A packer disposed about the mandrel is movable from an unset to a set position. An opening sleeve is movable in the mandrel from a closed position to an open position in which the flow ports are exposed to allow flow therethrough. The opening sleeve is operable to move the setting sleeve to set the packer against the wellbore as it moves in the mandrel from the closed to the open position.

A stage cementing tool has a mandrel defining a central flow passage and a plurality of cementing passages in a wall thereof. A packer is disposed about the mandrel. A closing sleeve is detachably connected to and movable relative to the mandrel. An opening sleeve defining a plurality of fully open cement flow ports therethrough is telescopically movable relative to the closing sleeve and movable relative to the mandrel. The opening sleeve is movable to move the packer to the set position, and thereafter movable to open a cement flow path between the central flow passage and an annulus defined by the stage cementing tool and the wellbore.