Abstract: A wellbore assembly includes a wellbore string disposed within a wellbore and a cement retainer coupled to a downhole end of the wellbore string. The cement retainer includes a housing, a packer, a valve, and a sleeve. The housing includes one or more fluid ports extending from an interior surface of the housing to the annulus. The housing defines a first fluid pathway extending from within the wellbore string to within the housing. The sleeve is movable between a first position, in which the sleeve blocks the one or more fluid ports, and a second position in which the sleeve exposes the one or more fluid ports to open a second fluid pathway extending from the annulus, through the one or more fluid ports, to the first fluid pathway. Opening the second fluid pathway allows mixing of a first fluid with a second fluid in the cement retainer.

Abstract: A wellbore whipstock tool assembly includes a body that includes an uphole axial surface that is slanted from one portion of an edge of the uphole axial surface to another portion of the edge of the uphole axial surface, a downhole axial surface opposite the uphole axial surface, and a radial surface between the uphole axial surface and the downhole axial surface; one or more keys formed on the radial surface and configured to secure into one or more keyholes formed in a casing of a wellbore; and a bore that extends between an opening in the uphole axial surface and an opening in the downhole axial surface, the bore sized to receive a bottom hole assembly of an intervention tool.

Abstract: 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.

Abstract: A wellbore whipstock tool assembly includes a body that includes an uphole axial surface that is slanted from one portion of an edge of the uphole axial surface to another portion of the edge of the uphole axial surface, a downhole axial surface opposite the uphole axial surface, and a radial surface between the uphole axial surface and the downhole axial surface; one or more keys formed on the radial surface and configured to secure into one or more keyholes formed in a casing of a wellbore; and a bore that extends between an opening in the uphole axial surface and an opening in the downhole axial surface, the bore sized to receive a bottom hole assembly of an intervention tool.

Abstract: 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.

Abstract: 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.