Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Patent
1991-10-11
1993-05-04
Bell, Mark L.
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
106737, C04B 1400, C04B 1600
Patent
active
052078329
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns compositions termed "cement slag" by petroleum engineers and "cement grout" by concrete workers but will be referred to as "cement grout" hereinafter. More particularly, the present invention relates to a lightened cement grout which is suitable for the cementation of natural hydrocarbon production wells (petroleum or gas).
BACKGROUND OF THE INVENTION
Cementation of natural hydrocarbon production wells is performed between the external part of the casing and the wall of the well to support the entire series of tubes and to prevent the flow of pressurized liquid or fluid originating in the subterranean strata in which drilling occurs.
It is especially important that the cement used for this purpose exhibits, after hardening, rapid and pronounced resistance to compression in order to possess satisfactory mechanical properties. Furthermore, it is often necessary that these cements are gas-impermeable in order to effectively block the flow of highly-pressurized gases which may be present in the drilled strata and which may travel through the cement, even as the cement hardens.
However, frequently, the drilled strata exhibit a mechanical strength which is too weak to allow the use of cements having a high density, i.e., of approximately 1.6 to 1.9 g/cm.sup.3. In this case, recourse must be made to cements termed "lightened," i.e., whose density ranges between 1 and 1.6 g/cm.sup.3 and in which inert or active lightening filling materials are incorporated.
The state of the art has proposed numerous types of filling materials. For example, the use of hollow glass microspheres containing air or an inert gas has been suggested. However, these filling materials pose serious risks for pumps and injection systems, since they may burst or implode. Furthermore, the real density of the cement grout is difficult to adjust. Finally, these lightening products are costly.
Silicates have also been proposed as lightening filling materials, but these compounds have a low compression resistance.
Finally, incorporating compounds capable of producing a gas in situ, which forms bubbles in these compounds, into the cement grout has also been contemplated. This solution can plausibly be considered for areas where the depth is slight. However, this procedure is more costly and is difficult to implement because the diameter of the ga bubbles cannot be controlled effectively and the bubbles promote the cracking of the cement.
In any case, the gas-impermeability of the cements lightened by these means poses serious problems for which solutions have long been sought.
Patent No. FR-A-2587988 proposes the use of, in a hydraulic cement slag containing light aggregates as a lightening filling material, such as hollow microspheres, an impermeability agent formed by particles of silica powder accounting for between 5 and 100% by weight of the hydraulic cement. These silica particles may be secondary products originating in electric ovens used for the production of silicon or ferrosilicon.
SUMMARY OF THE INVENTION
The present invention concerns lightened cement grouts containing fine silica particles, and represents an improvement in the compression resistance of cements obtained from these grouts and eliminates or limits their shrinkage.
Accordingly, one purpose of the invention is to achieve lightened cement grouts having a density of between 1.20 and 1.70, high mechanical performance levels, and whose compression resistance, which, in particular, varies as a function of density, which reaches and surpasses 15 MPa for a density of 1.40, and 30 Mpa for a density of 1.60, after 24 hours and at a temperature of 60.degree. C.
Another purpose of the invention is to provide a lightened cement grout which is impermeable to gas, even when highly pressurized, when it is put in place in a petroleum well.
A further purpose of the invention is to provide a lightened cement grout which is compatible with conventionally-used additives.
Another object of the invention is to provide a lightened cemen
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Baffreau Daniel
Laugerotte Jean-Claude
Musikas Nicolas
Bell Mark L.
Ciments d'Origny
Total Compagnie Francaise des Petroles
Wright Alan
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