Method for characterising the mechanical behaviour of cements

Patent metadata

Field	Value
Publication number	US-9664648-B2
Application number	US-201314379549-A
Country	US
Kind code	B2
Filing date	Feb 21, 2013
Priority date	Feb 22, 2012
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

The present invention relates to a method for determining mechanical parameters of a cementitious system, on the basis of time, and on the basis of the fineness of the cementitious system, pressure and/or temperature, representative of the in situ conditions found in wellbores. The initial composition of the cementitious system, the fineness Φ thereof and the speed of the compression waves on the basis of time V p (t) are the only input data of the method. Said method comprises: ▪ a step A of estimating the degree of hydration of the cementitious system on the basis of time α(t) from Vp(t), at a pressure P 1 and a temperature T 1 ; ▪ a step B wherein α(t) is determined on the basis of desired values of fineness Φn of the cementitious system, pressure Pn and/or temperature Tn; ▪ a step C wherein the composition of the cementitious system is determined on the basis of time C(t) and on the basis of desired values of fineness Φn of the cementitious system, pressure Pn and/or temperature Tn from α(t) determined in step B; ▪ and a step D of determining at least one mechanical parameter of the cementitious system on the basis of time and on the basis of desired values of fineness Φn of the cementitious system, pressure Pn and/or temperature Tn, from C(t) determined in step C. According to the method of the invention, these parameters can be determined while the cementitious system is still very young. In particular, the parameters of static deformability and hydro-mechanical coupling parameters are determined by the method according to the invention.

First claim

The invention claimed is:

1. A method for determining mechanical parameters of a cement system of initial composition C 0 and of fineness Φ, as a function of time, and as a function of fineness of the cement system, pressure and temperature, comprising the following steps:
(A) determining a degree of hydration of the cement system as a function of time α(t) from a velocity of a compression waves as a function of time V p (t) measured in a specimen of the cement system, at a pressure P 1 and a temperature T 1 ;
(B) determining the degree of hydration α(t) as a function of desired values of fineness Φ n of the cement system, of pressure P n and of temperature T n ;
(C) determining a composition of the cement system as a function of time C(t) and as a function of desired values of fineness Φ n of the cement system, of pressure P n and of temperature T n , from the degree of hydration α(t) determined in step B;
(D) determining at least one mechanical parameter of the cement system as a function of time, and as a function of the desired values of fineness Φ n of the cement system, of pressure P n and of temperature T n , from the composition of the cement system C(t) determined in step C.

2. The method as claimed in claim 1 , further comprising an initial step of measurement of the velocity of the compression waves as a function of time V p (t) in a specimen of the cement system.

3. The method as claimed in claim 1 , wherein said mechanical parameter is selected from static deformability parameters.

4. The method as claimed in claim 3 , wherein static deformability parameters are two static elastic parameters selected from static Young's modulus E, static Poisson's ratio □, bulk modulus K, shear modulus G.

5. The method as claimed in claim 3 , further comprising determination of a mechanical parameter selected from the parameters of hydro-mechanical coupling.

6. The method as claimed in claim 1 , wherein the degree of hydration of the cement system as a function of time α(t) is calculated from V p (t) according to a linear relation.

7. The method as claimed in claim 6 , wherein the degree of hydration of the cement system as a function of time α(t) is calculated from V p (t) according to the relation α=(V p −V 0 )/(V ∞ −V 0 ), with V 0 and V P corresponding respectively to the velocity of the compression waves measured in the specimen of the cement system at time t=0 and at time t, and V ∞ corresponding to the velocity of the compression waves in a specimen of a fully hydrated cement system.

8. The method as claimed in claim 1 , wherein the hydration process comprises a first stage in which hydration is mainly governed by a process of nucleation and growth, and a second stage in which hydration is mainly governed by an ion diffusion process, said second stage starting when the degree of hydration α reaches a threshold value degree of hydration α*, this threshold value α* being a function of the temperature, and in which step B comprises the following substeps:
(B-i) determination of the degree of hydration α(t) during the first stage of the process of hydration of the cement system;
(B-ii) determination of the degree of hydration α(t) during the second stage of the process of hydration of the cement system;
each of the substeps B-i and B-ii taking into account the fineness Φ of the cement system, the pressure and the temperature for determining the degree of hydration α(t).

9. The method as claimed in claim 8 , wherein the threshold value of degree of hydration α* is evaluated by minimizing the difference between α(t) determined using a kinetic model 120 and α(t) determined experimentally from the velocity of the compression waves, for different temperatures, and at a constant pressure, so as to take into account a variation of α* as a function of the temperature in step B.

10. The method as claimed in claim 9 , wherein:
the cement system of initial composition C 0 comprises a cement and water, the cement comprising at least one reactive initial phase X;
the degree of hydration α(t) determined in step B corresponds to a weighted average of the degrees of hydration of each of the reactive initial phases X of the cement;
the degree of hydration of each of the reactive initial phases X of the cement is a function of a ratio of a chemical affinity A x (α) of the reactive initial phase X, this chemical affinity A x (α)controlling a rate of variation of the hydration of the reactive initial phase X, to a characteristic time associated with reaction of the reactive initial phase X with water τ x ;
and the characteristic time associated with reaction of the reactive initial phase X with water is τ x is a function of the fineness Φ of the cement, the pressure and the temperature.

11. The method as claimed in claim 10 , wherein the characteristic time associated with reaction of the reactive initial phase X with water τ x is expressed according to the following equation:

τ
x

⁡

(

T
,
Φ

)

+

Φ
0

Φ

n
x

+
1

×

τ
x

⁡

(

T
0

,

Φ
0

)

⁢

exp
⁡

(

Δ
⁢

⁢

E
x

R

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1
T

Assignees

• Total Sa

Inventors

• Bois Axel-Pierre
• Garnier Andre
• Laudet Jean-Benoit
• Vu Manh-Huyen
• Ghabezloo Siavash
• Sulem Jean

Classifications

• G01N2291/02827

  Elastic parameters, strength or force · CPC title

• G01N2291/0251

  Solidification, icing, curing composites, polymerisation · CPC title

• G01N2291/02441

  Liquids in porous solids · CPC title

• G01N2291/0232

  Glass, ceramics, concrete or stone · CPC title

• G01N33/383

  Concrete or cement · CPC title