Abstract: A method and apparatus for estimating the time varying mechanical properties of a cement including propagating acoustic waves through a cement sample, measuring signals corresponding to the acoustic waves after they propagate in the sample, comparing attributes from the measured signals with corresponding attributes provided by a model accounting for at least initially estimated acoustic properties of the cement, using the differences between the measured and calculated signals to update the initially estimated acoustic properties of the material in the calculating model, using the differences between the measured and calculated signals, updating the initial acoustic properties in the model, processing N iterations of the comparison and updating either until the differences between measured and calculated signals are within a given tolerance factor or when the number i reaches a prescribed maximum and calculating the time varying mechanical properties of the cement from the final iterated acoustic properties.

Abstract: An additive for use in aqueous cement slurries which adapted such that, when added to an aqueous cement slurry, it migrates to an interface between the slurry and an adjacent solid material or fluid composition during a setting phase of the cement because of the passing of the upper limit of solubility in the water of the additive.

Abstract: The present invention relates to a method of modelling a circuit travelled by a drilling mud during drilling, the circuit including both the well and the surface equipment, in particular solid separation devices, in which method, for each time sequence, there are calculated the mass concentration of each liquid and solid species present in the mud, the total flow rate, and the grain size distribution of each solid species downstream from each item of equipment. The invention also provides inversion of the above method to estimate the size of the cuttings on the basis of the measured efficiency of solid separation devices.

Abstract: A method for estimating the time varying mechanical properties of a material comprising: propagating acoustic waves through a sample of material; measuring signals corresponding to acoustic waves after they propagate in the sample; and characterised by: comparing attributes from the measured signals with attributes from corresponding signals provided by a calculating model, the calculating model accounting for at least initially estimated acoustic properties of the material; using the differences between the measured and calculated signals to update the initially estimated acoustic properties of the material in the calculating model; processing N iterations of the comparison and updating either until the differences between measured and calculated signals are within a given tolerance factor or when the number i reaches a prescribed maximum; and calculating the time varying mechanical properties of the material from the final iterated acoustic properties.