A completion string includes at least one isolation packer positioned between well zones of a plurality of well zones, and a sand control assembly and a circulating assembly each disposed uphole of a washdown shoe in the bottom-most well zone. A top well zone includes a return valve assembly, a production packer, and a second circulating assembly and a second sand control assembly downhole of the production packer. The completion string also includes an outer string spanning from the bottom-most well zone to the top well zone, and an inner production string concentrically arranged within the outer string, creating an inner-annulus between the outer string and inner production string. The inner-annulus is continuous from the washdown shoe to the return valve assembly, and the inner production string includes a production valve disposed between the sand control assembly and the circulating assembly in each of the bottom-most and top well zones.

An apparatus includes a funnel, a core, a first coating, a second coating, and a third coating. The funnel includes multiple inlet ports and an outlet port. The core is disposed within the funnel. The first coating is disposed on and surrounds an outer surface of the core. The first coating is configured to dissolve in response to being exposed to water. The second coating is disposed on and surrounds an outer surface of the first coating. The second coating is configured to dissolve in response to being exposed to water. The third coating is disposed on and surrounds an outer surface of the second coating. The third coating is configured to dissolve in response to being exposed to a hydrocarbon.

An apparatus for flowing and mixing cement within a subterranean formation includes a housing, a flow control device, and baffles. The housing is configured to contain a cement additive. The housing includes a first end and a second end. The first end is configured to couple to a cement retainer. The flow control device is disposed at the second end of the housing. The baffles are disposed within the housing.

A stage cementing differential valve tool includes a body extending from a first end to a second end. The body may include one or more ports that may be configured to circulate a cement slurry, an external sleeve may be slidably coupled to an outer surface to the body, and an internal sleeve assembly may be slidably coupled to an inner surface to the body. The external sleeve and the internal sleeve assembly may be configured to open and close the one or more ports. The stage cementing differential valve tool may also include a sealing element extending from the outer surface of the body that is configured to swell in a downhole fluid environment and a plug having shoulders with break-off points that is configured to actuate the internal sleeve assembly.

A wellbore assembly includes a cable configured to be disposed within a wellbore. The wellbore assembly also includes a housing attached to a downhole end of the cable. The housing defines a fluid outlet at a downhole end of the housing. The housing includes an anchor and a collapsible gate. The anchor engages a wall of the wellbore under increased tension in the cable, thereby anchoring the housing to the wellbore. The collapsible gate is disposed inside the housing between an uphole end of the housing and the fluid outlet. The housing temporarily stores a treatment fluid configured to treat an obstruction in the wellbore. The collapsible gate is configured to break, with the anchor engaged, under further tension applied by the cable, inside the housing to allow the treatment fluid to flow out of the housing through the fluid outlet toward the obstruction.

Degradable downhole tools, tool components, and balls are formed from a processed polyvinyl alcohol (PVA) compound that is degradable in a high-salinity environment. The PVA compound exhibits strength and elasticity properties that are comparable to existing degradable downhole polymers and further exhibits degradability properties that are superior to existing degradable downhole polymers, particularly in high-salinity fluids. For different components, the PVA compound may include a reinforcing material such as fiberglass. The PVA compound also includes a loading of degradable metal, such as a degradable magnesium alloy, rendering the material degradable at high salinity. Usage of tools, tool components, and balls formed from the disclosed materials eliminates the requirement that such equipment be drilled out after use as the PVA compound quickly degrades in high-salinity downhole fluids.

A downhole device that drills a wellbore includes a stabilizer which has a body and blades. The blades are disposed on a surface of the body and each blade has a hollow space. The blades each include a dissolvable window that is disposed on a surface of each of the blades and a light source that emits light to the wellbore. The dissolvable window blocks light emitted from the light source thereby reducing or eliminating light from being transmitted to the wellbore. The dissolvable window dissolves upon exposure to a fluid containing a dissolving medium, thereby allowing the light source to transmit light to the wellbore. Methods of using the downhole device to activate downhole chemicals are also provided.

A mud loss treatment drilling tool includes the tool having an upper tooljoint to a lower end of an above drill pipe string, one or more tanks with a through channel for a drilling fluid flow, a lower tooljoint connected to a BHA assembly at least comprising a drill bit; the tank arranged for holding a swellable sealant agent; the swellable sealant agent arranged for mixing with water to swell; the tank provided with an outlet to the through channel for the swellable sealant agent, so as for, when an undesired mud loss is detected, for flushing all or part of the swellable sealant agent into the through channel, so as for a mixture of the swellable agent and the water to start reacting to swell during the time it takes the mixture to reach a fracture extending from a well under drilling by said BHA, so as for continuing to swell and block the fracture to stop the undesired mud loss.

A corrodible downhole article includes a magnesium alloy, including: a strengthening metallic element comprising at least one of Al, Zn, Mn, Cu and Ag and at least one corrosion promoting element in an amount of 0.01-10 wt % in total. The alloy has a corrosion rate of at least at least 75 mg/cm.sup.2/day in 15% KC1 at 93° C. and a 0.2% proof strength of at least 100MPa when tested using standard tensile test method ASTM B557-10. In particular, the magnesium alloy includes 5-10 wt % Al, and at least one of Zn and Mn in a total amount ranging from 0 to 1.0 wt %.

A differential fill valve assembly for application in float collars or shoes in a well casing can provide locking mechanisms to limit premature movement of an activating sleeve while facilitating desired advancement of the activating sleeve. The valve assembly comprises a backpressure flapper valve and an activating sleeve slidably disposed within a housing. The activating sleeve initially maintains the flapper valve in an open position while the activating sleeve is maintained in its position by upper and/or lower lock rings on either side of a shoulder of the activating sleeve. A tripping ball is dropped to seat in the activating sleeve. Pressure applied on the ball moves the activating sleeve downward, releasing the backpressure flapper valve, after which the tripping ball exits the bottom of the assembly. The lower lock ring maintains the activating sleeve in its lower position.