Abstract: A method of cementing a well permitting a reduction in the degree of diameter reduction of casing or liners required, and not requiring excessively large initial conductor casing, is described. The method is characterized by provision of an enlarged wellbore and a novel liner structure which is adapted for expansion of a reduced diameter section thereof downhole, providing, before expansion of the section, unimpeded flow of fluid from the enlarged wellbore during cementing and close fit of the expanded section with the casing or preceding liner, after cementing is completed and expansion of the section. A novel well liner structure and novel well liner expansion means are disclosed.

Abstract: Methods and processes are claimed for optimal design of hydraulic fracturing jobs, and in particular, methods and processes for selecting the optimal amount of proppant-carrying fluid to be pumped into the fracture (which is a crucial parameter in hydraulic fracturing) wherein these design parameters are obtained, ultimately from a priori formation/rock parameters, from pressure-decline data obtained during both linear and radial flow regimes, and by analogy with a related problem in heat transfer, in addition the claimed methods and processes also include redundant verification means.

Abstract: A method for placing a plug at a predetermined location in a wellbore, the method being based on utilising a supporting fluid solidifying after being subjected to shear forces. After placing the supporting fluid and allowing it to develop sufficient strength, the plug material is injected. A preferred example of the fluid is an emulsion comprising polymer material and crosslinking agent separated by phase boundaries prior to the shearing process.

Abstract: An acidic fluid that is useful in stimulation and workover operations, and in particular, in matrix acidizing treatments, comprises an acid, such as hydrochloric acid; water; an aliphatic aldehyde having 1-10 carbon atoms; and an aromatic aldehyde having 7-20 carbon atoms. The aliphatic aldehyde preferably has 1-6 carbon atoms. Glyoxylic acid and glyoxal are especially preferred aliphatic aldehydes. The aromatic aldehyde preferably has 7-10 carbon atoms. Cinnamaldehyde is especially preferred.

Abstract: The present Invention relates to hydrocarbon well stimulation, and more particularly to methods and compositions to remove (or more generally to transfer) fluid introduced into a subsurface fracture, in which the methods involve creating then exploiting chemical potential gradients at the fracture face to induce fluid flow from the fracture into the formation; the methods and compositions involve creating, or relying upon an intrisic or previously created, a selectively permeable membrane that is permeable to water but that does not allow solutes to pass through.

Abstract: An apparatus for cleaning subterranean wellbores is described. The apparatus comprises a sleeve member which is fixed to a part of the drillstring and a rotatable jet head with nozzles through which an abrasive fluid is discharged. The nozzles are mounted such that the fluid jet is directed to an area of the wellbore immediately adjacent to a leading edge of the sleeve. The nozzle head is restricted in its protrusion out of the sleeve.