Method and apparatus for activation of furnace slag base cement
First Claim
1. A method of preparation of formulations for cementing a wellbore, comprising:
- mixing drilling mud with blast furnace slag (BFS) in rig equipment normally used for mud circulation during drilling;
pumping the mixture of mud and BFS into the wellbore; and
injecting activator inline into the BFS/mud mixture before it enters the wellbore.
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Accused Products
Abstract
The invention provides for metering the pumping rate of BFS/mud mixtures pumped to the cementing head on a rig for sealing off the formation from the casing. Since BFS/mud mixtures require an activation agent, preferably sodium hydroxide is pumped into the flowline to the cementing head. Feedback from the BFS/mud slurry flowrate is fed to the activator injector pump drive system to regulate the addition rate of the activating agent in response to varying conditions, such as mud flowrate. The injection rate target can also be adjusted to compensate for any changes in downhole temperature. The risk of fouling surface equipment and the casing internal diameter is minimized because the activation agent is added very close in time to when the BFS/mud mixture enters the cementing head. Even in situations where the anticipated downhole temperature is significantly lower than the surface temperature, a sufficient amount of activating agent is added for the downhole conditions without fear of fouling the casing internal or the surface pumping equipment.
60 Citations
17 Claims
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1. A method of preparation of formulations for cementing a wellbore, comprising:
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mixing drilling mud with blast furnace slag (BFS) in rig equipment normally used for mud circulation during drilling; pumping the mixture of mud and BFS into the wellbore; and injecting activator inline into the BFS/mud mixture before it enters the wellbore. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of preparation of formulations for cementing a wellbore, comprising:
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mixing drilling mud with blast furnace slag (BFS) in rig equipment normally used for mud circulation during drilling; pumping the mixture of mud and BFS into the wellbore; injecting activator inline into the BFS/mud mixture before it enters the wellbore; measuring the BFS/mud flowrate; creating a signal based on said measuring; controlling the flow of injected activator based on said measuring; pumping the activator into the BFS/mud mixture adjacent an inline mixer; skid mounting said activator pump, said variable speed drive, said mixer, said controller, and interconnecting signal lines for compactness when based on a drilling rig; and providing a bypass on said skid to allow fluid to pass through said skid while isolating activator from the BFS/mud flow line. - View Dependent Claims (10)
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11. A method of cementing a wellbore, comprising:
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mixing blast furnace slag with drilling mud at the surface; pumping as yet unactivated BFS/mud mixture toward the wellbore; and injecting an activator inline into the flowing BFS/mud mixture shortly before it enters the wellbore. - View Dependent Claims (12, 13)
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14. A method of cementing a wellbore, comprising the steps of:
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continuously mixing BFS into drilling mud to a predetermined value; continuously adding inline an activator to a predetermined proportion of BFS in the mud. - View Dependent Claims (15, 16)
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17. A method of cementing a wellbore, comprising the steps of:
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continuously mixing BFS into drilling mud to a predetermined value; continuously adding inline an activator to a predetermined proportion of BFS in the mud; using a pump to add activator into a BFS/mud flowline; regulating pump output in relation to measured BFS addition rate in the mud; using a variable speed drive on said pump; adjusting pump output responsive to BFS addition rate in flowing BFS/mud mixture by varying pump speed with said variable speed drive.
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Specification