Weight materials for use in cement, spacer and drilling fluids
View Patent ↗A drilling fluid, spacer fluid and cementing compositions for use in subterranean wells are disclosed along with methods for making using same, where the compositions include a weighting system having an effective amount of a metal silicon alloy, mixtures of metal silicon alloys, or mixtures of metal silicon alloys and conventional weighting agents, to produce compositions having a desired high density, while retaining other fluid properties such as pumpability, gas tight sealing, low tendency to segregate, and reduced high temperature cement strength retrogression.
1. A downhole cement composition comprising:
a pumpable cement slurry including:
water;
a hydraulic cement; and
from 25 wt. % to 110 wt. % of a primary weighting agent, based on the weight of the hydraulic cement in the absence of the primary weighting agent, including a ferrosilicon having a density of at least 6.0 g/cm 3 ,
where the primary weighting agent increases the density of the downhole cement composition, while maintaining other properties including at least pumpability, gas tight sealing, reduced tendency to segregate, and/or reduced high temperature cement strength retrogression, and where the composition has (1) a plastic viscosity at least 10% lower than a composition including an equivalent amount of hematite as the weighting agent, (2) a yield point at least about 15% lower than a composition including an equivalent amount of hematite as the weighting agent, (3) a cure rate at least 10% faster than a composition including an equivalent amount of hematite as the weighting agent, and (4) a cure strength after 6 hours of curing and a final cure strength at least 10% higher than a composition including an equivalent amount of hematite as the weighting agent.
2. The composition of claim 1 , further including:
a gelling agent,
a dispersant, and/or
a fluid loss control additive.
3. The composition of claim 1 , wherein the ferrosilicon has a density of at least 6.5 g/cm 3 .
4. The composition of claim 1 , wherein the weighting agent comprises a powder having particles between 100 nm and about 500 μm.
5. A downhole cementitious composition comprising:
a pumpable cement slurry including:
a Portland cement;
from about 25 wt. % to about 110 wt. % of a primary weighting agent, based on the weight of the Portland cement in the absence of the primary weighting agent, comprising a ferrosilicon having a density of at least 6.0 g/cm 3 and a particle size distribution between 10 nm and 1 mm; and
water,
where the primary weighting agent increases the density of the downhole cementitious composition, and where the composition has (1) a plastic viscosity at least 10% lower than a composition including an equivalent amount of hematite as the weighting agent, (2) a yield point at least about 15% lower than a composition including an equivalent amount of hematite as the weighting agent, (3) a cure rate at least 10% faster than a composition including an equivalent amount of hematite as the weighting agent, and (4) a cure strength after 6 hours of curing and a final cure strength at least 10% higher than a composition including an equivalent amount of hematite as the weighting agent.
6. The composition of claim 5 , further comprising:
a dispersing agent;
a gelling agent; and/or
a fluid loss control additive.
7. The composition of claim 5 , wherein the ferrosilicon has a density of at least 6.5 g/cm 3 .
8. The composition of claim 5 , wherein the weighting agent comprises a powder having particles between 100 nm and about 500 μm.
9. The composition of claim 1 , further comprising:
a secondary weighting agent including iron, steel, barite, hematite, iron ores, tungsten, tin, manganese, manganese tetraoxide, calcium carbonate, illmenite, sand, or mixtures thereof.
10. The composition of claim 5 , further comprising:
a secondary weighting agent including iron, steel, barite, hematite, iron ores, tungsten, tin, manganese, manganese tetraoxide, calcium carbonate, illmenite, sand, or mixtures thereof.