Abstract: A wellbore service fluid comprising viscoelastic surfactants in combination with means for controlling the concentration of at least partially charged sites within the fluid is described.

Abstract: A method of quantitative analysis of free organic components in a drilling fluid comprising separating solid and liquid components of the drilling fluid using a non-filtering technique such as centrifuging, mixing a sample of the liquid components with a solution of an inorganic carrier such as 2M KBr and analyzing the mixture using infrared spectroscopy so as to determine the amount of organic components in the mixture and deriving the amount of free organic components in the drilling fluid from this analysis. In one embodiment, the mixture is dried to leave a solid mixture of the organic components and the carrier. In this case, the sample is preferably analyzed using a reflectance technique such as diffuse reflectance infrared spectroscopy. In another embodiment, the mixture is analyzed as a liquid, preferably using a direct transmission technique. In both the liquid and solid cases, Fourier transform infrared spectroscopy is preferred.

Abstract: A method of analysing the major and/or minor phase composition of a cement comprising a) preparing a calibration model from samples for which the phase composition has been determined and for which infra red spectra, typically Fourier transform infrared spectra, obtained by a diffuse reflectance technique, have been obtained so as to relate differences between spectra of the samples to differences in clinker phase composition of the samples; and b) obtaining the infra red spectrum of a sample of unknown phase composition and determining the phase composition of the sample from the calibration model typically using a multivariate statistical method.

Abstract: The invention in one aspect provides a method of testing drilling mud in use which comprises periodically sampling the circulating mud and analyzing its aqueous filtrate at the rig site by ion chromatography for selected positive and negative ions; one or more other parameters of the sampled mud and/or mud filtrate (e.g. pH, temperature) may also be measured; preferably the composition of the mud filtrate thus monitored is interpreted to indicate downhole interactions, with the composition of the mud supplied to the hole being adjusted to or towards the optimum as drilling proceeds. The invention also provides a method in which the solids of the periodically sampled mud are analyzed at the rig site, e.g. for sorbed ions and/or for cation exchange capacity; the values so obtained are preferably combined with those for the mud filtrate analysis and used in the diagnosis of downhole conditions for adjustment of the composition of freshly supplied mud.

Abstract: Samples of mud are taken periodically at the surface at one or several locations where the mud does not contain cuttings anymore. The mud samples are analyzed on the rig site to determine the successive values, as a function of time or depth, of a parameter representative of the weight of the fine solids present in the mud. In one aspect of the invention the weight of the fine solids present in the mud is determined by measuring the weight of the liquid phase of the mud and the weight of the electrolyte dissolved in a known weight of mud. Preferably the weight of the liquid phase is determined by drying to constant weight a given weight of mud and the weight of electrolyte is determined by chemical analysis of the mud filtrate using an ion chromatography system on the rig site.