Abstract: Migration of formation solids in a wellbore is restrained by feeding a slurry, comprising water, a viscosifier, and a concentration of cement clinker particles, into the wellbore, and hydrating the clinker particles in the wellbore. The clinker particles are kept in suspension during the hydrating, and upon completion of the hydrating the hydrated clinker particles form a hardened cement consisting of a permeable structure of interconnected hydrated clinker particles. A layer of degradable lost circulation material (LCM) may be employed to separate the slurry with clinker particles from the formation surrounding the wellbore during hydrating of the clinker particles.

Abstract: Migration of formation solids in a wellbore is restrained by feeding a slurry, comprising water, a viscosifier, and a concentration of cement clinker particles, into the wellbore, and hydrating the clinker particles in the wellbore. The clinker particles are kept in suspension during the hydrating, and upon completion of the hydrating the hydrated clinker particles form a hardened cement consisting of a permeable structure of interconnected hydrated clinker particles. A layer of degradable lost circulation material (LCM) may be employed to separate the slurry with clinker particles from the formation surrounding the wellbore during hydrating of the clinker particles.

Abstract: A method for preventing undesired cement flow in a well containing a tubing string, comprises: determining a desired pressure drop for a desired flow rate at a desired location in the tubing string, determining a flow area that will cause the desired pressure drop, and installing in the tubing string a choke having at least one port, wherein the total area of the port or ports equals the desired flow area. The choke may include at least two ports, one of which may include a least one rupture disk disposed selected to rupture when the pressure drop across the choke exceeds a predetermined value. The choke may be below a float collar in the well. The invention allows the use of foamed cement and in particular foamed cement having a density that is less than the lowest density that could have been used if the choke were not in place.

Abstract: A method for improving zonal isolation between formations along a borehole, comprises a) providing a pipe in the borehole, wherein at least a portion of the pipe lies between the formations, b) providing a body of cement in the annulus between the borehole wall and said pipe portion, c) allowing the body of cement to cure until it has reached at least 70 Bearden units consistency, and d) expanding said pipe portion so as to decrease the cross-sectional area of the annulus between the borehole wall and said pipe portion.

Abstract: A method for expanding an expandable tubular in a borehole, comprising the steps of: a) positioning the expandable tubular at a desired position in the borehole; b) anchoring the tubular at the desired position solely by means of a first cement portion in the annulus between the tubular and the borehole wall; c) expanding the tubular by moving an expansion device through the tubular. The cement may be cured or not cured when step c) is carried out and may or may not fracture during step c). The method may include providing an exit path for water expelled from the cement during expansion, providing a second cement portion having a longer cure time than the first cement portion, or calculating the length of cement that is required to anchor, based on the properties of the cement and the expected expansion force.