Lignite Copolymer Cement Reduces Transition Time
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Solution Overview
Problem
Cement compositions in subterranean operations face issues with unwanted gas migration due to a transition phase where the cement loses hydrostatic pressure, leading to flow channels in the set cement that compromise isolation of the subterranean formation, and existing additives either have limited effectiveness or are too expensive or provide longer transition times.
Innovation Solution
A cement composition incorporating a lignite-based copolymer with a lignite backbone and grafted monomers such as 2-acrylamido-2-methylpropanesulfonic acid and N,N-dimethylacrylamide, which shortens the transition time and reduces fluid loss, allowing the cement to set before gas migration occurs, thereby preventing flow channels from forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a copolymer additive is used to control gas migration, then transition time is reduced, but the solution becomes too viscous for pumping above 9% concentration
Solution Approach 1:
The patent uses a lower concentration of copolymer additive (below 9% by weight) that provides sufficient gas migration control during the critical transition phase, then allows the additive to be consumed as the cement sets. This temporary use of the additive avoids long-term viscosity issues while achieving the desired transition time reduction.
Solution Approach 2:
The patent optimizes the concentration parameter of the copolymer additive to be below 9% by weight, which maintains pumpability while still achieving effective gas migration control. This parameter optimization balances the competing requirements of reducing transition time and maintaining ease of operation.
2Reliability
If cement composition loses hydrostatic pressure during transition phase, then gas migration occurs and flow channels form, but maintaining hydrostatic pressure extends transition time
Solution Approach 1:
The patent incorporates the copolymer additive in advance into the cement composition before placement. This preliminary action ensures that when the transition phase occurs, the additive is already present to prevent gas migration and maintain hydrostatic pressure, thereby achieving both reliability and acceptable transition time.
Solution Approach 2:
The copolymer additive acts as an intermediary substance between the cement composition and the gas in the formation. It mediates the interaction by reducing interfacial tension and preventing gas from migrating into the cement, thereby maintaining isolation effectiveness without requiring extended transition time.
3Loss of time
If existing gas migration control additives are used, then transition time is reduced, but they are either too expensive or provide longer transition times
Solution Approach 1:
The patent employs a cost-effective copolymer additive at an optimized concentration (below 9% by weight) that provides sufficient gas migration control for the duration of the transition phase. This approach uses a more economical additive at a lower concentration, reducing overall cost while achieving the desired transition time reduction.
Solution Approach 2:
The patent optimizes the concentration parameter of the copolymer additive to achieve the most cost-effective solution. By adjusting the concentration to be below 9% by weight, the patent reduces the amount of additive required, thereby lowering material costs while still achieving effective gas migration control and acceptable transition time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The lignite-based copolymer significantly reduces the transition time of the cement composition, ensuring effective sealing and preventing gas migration, while also improving compressive strength development without retarding it, making it suitable for various subterranean operations.
Implementation Method 1
Another event is the loss of fluid from the slurry to the subterranean formation
Implementation Method 2
Another event is the development of static gel strength in the slurry
Data Source
AI summary
A method of cementing in a subterranean formation may comprise: introducing a cement composition comprising cement, water, and a lignite-based copolymer into a subterranean formation, wherein the lignite-based copolymer comprises a lignite backbone, a first grafted monomer selected from the group consisting of -acrylamido-2-methylpropanesulfonic acid, a salt of 2-acrylamido-2-methylpropanesulfonic acid, and a second grafted monomer comprising N,N-dimethylacrylamide; and allowing the cement composition to set in the subterranean formation, wherein cement composition has a transition time of less than or equal to about 150 minutes.