Abstract: An optical fiber pH sensor 100, 200, 300 is described, where a transducer mechanically couples a Bragg grating to a pH-sensitive hydrogel, said sensor comprising a central part 110, 210, 301 where are placed the optical fiber 121 containing a Bragg grating 122, the pH-sensitive hydrogel set of discs 130, and the mechanical transducer which is a spring 123 a beam 215 or still the optical fiber itself 121, the mechanical transducer assuring the strain on the Bragg grating 122. The change in hydrogel hydrodynamic volume resulting from a change of the pH of the medium introduces a force that is sufficient to cause a strain in the Bragg grating. The measure of the pH change is retrieved using the usual techniques for wavelength measurement. The pH sensor 100, 200, 300 of the invention is useful for the indirect evaluation and control of corrosion in petroleum wells and is suitable for multiplexing with other optical fiber sensors measuring the same or different parameters.

Abstract: Storable compositions and slurries for cementing oil and gas wells are described which comprise blast-furnace slag besides other additives which are usual in the cementing technique. The compositions and slurries are insufficiently activated (or are activated immediately before introducing them into the well), so that they can be stored for at least 72 hours (alternatively they may be stored indefinitely) without the setting of the composition and dispense with the addition of activation inhibitors. The use of the compositions and slurries in the cementing of oil and gas wells is also described.

Abstract: Storable compositions and slurries for cementing oil and gas wells are described which comprise blast-furnace slag besides other additives which are usual in the cementing technique. The compositions and slurries are insufficiently activated (or are activated immediately before introducing them into the well), so that they can be stored for at least 72 hours (alternatively they may be stored indefinitely) without the setting of the composition and dispense with the addition of activation inhibitors. The use of the compositions and slurries in the cementing of oil and gas wells is also described.

Abstract: Storable compositions and slurries for cementing oil and gas wells are described which comprise blast-furnace slag besides other additives which are usual in the cementing technique. The compositions and slurries are insufficiently activated (or are activated immediately before introducing them into the well), so that they can be stored for at least 72 hours (alternatively they may be stored indefinitely) without the setting of the composition and dispense with the addition of activation inhibitors. The use of the compositions and slurries in the cementing of oil and gas wells is also described.