| abstract |
Drilling muds are employed when drilling an oil well, primarily to carry rock cuttings up to the surface and out of the wellbore. Both water-based and oil-based muds are used, but the latter possess many operational advantages. However, conventional oil-based muds do suffer from a number of undesirable characteristics - the oil may be retained on the drill cuttings, and the presence of large amounts of the essential emulsifiers and other oil wetting agents can alter the wettability of oil-holding reservoir formations through which the borehole passes, thereby reducing their permeability to oil, and so making it more difficult to extract the oil therefrom. The present invention seeks to provide an alternative way of preparing water-in-oil emulsions so that in such emulsions high water levels and high stability can still be achieved but with the use of minimal levels of surfactant. More specifically, the invention suggests that the stability of water-in-oil emulsions may be significantly enhanced by using as a stabilising agent a particular type of silane - thus, first there is formed a water-in-oil emulsion with a fine dispersed aqueous phase in the continuous oil phase, and then there is added to this a silane having bonds which hydrolyse and condense to form a cross-linked polymer at the water-oil interface. |