Compositions and methods for controlling wellsite fluid and gas flow

摘要

Magnesium oxysulfate cement compositions and methods for controlling and preventing fluid and gas flow through a wellbore are described. The compositions and methods may be implemented to provide a barrier to fluid and gas flow between casings or in other operations such as squeeze operations. Magnesium oxysulfate cement compositions may include an admixture of magnesium oxide, magnesium sulfate trihydrate and water. When admixed with water, the compositions rapidly transition from a flowable state to a solid state with formation of little or no gel strength before the transition and further have a near-linear relationship between the time required for the transition to occur and the composition temperature at which the transition occurs enabling the user to determine the time within which the transition will occur. Additives, such as accelerators and inhibitors can be added to modify the time in which the compositions make the transition from flowable state to solid state. Other agents can be added to modify the specific gravity and viscosity of the compositions.

主权项

1. A method for preventing fluid and gas flow through a wellbore space around an axis and defined by an inner casing and an outer casing which surrounds the inner casing, the method comprising the steps of:
preparing a cement slurry to be injected into the wellbore space; placing a cement slurry supply line into the wellbore space between the casings, the supply line having at least two lateral outlets providing at least bi-directional flow of the cement slurry away from the supply line; and injecting the cement slurry into the wellbore through the supply line and the at least two lateral outlets such that the cement slurry simultaneously flows at least bi-directionally in both clockwise and counterclockwise directions around the wellbore space generally orthogonal to the axis with minimal axial flow to completely fill an axial region of the wellbore space thereby forming a solid plug between the casings which prevents fluid and gas flow through the wellbore, the cement slurry rapidly transitioning from a flowable state to a solid state to form the plug with formation of little or no gel strength before the transition and having a near-linear relationship between the time required for the transition to occur and the composition temperature at which the transition occurs.