Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Primarily organic continuous liquid phase
Patent
1999-05-10
2000-12-05
Warden, Jill
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Primarily organic continuous liquid phase
516 21, 507937, B01F 308, B01F 1700, C09K 300
Patent
active
061568058
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to stabilising emulsions, and concerns in particular a method for stabilising water-in-oil emulsions suitable for use in oil-based drilling muds.
When drilling a well, specifically an oil well, a drilling mud is employed primarily to carry rock cuttings up to the surface and out of the wellbore. Other functions of the mud are to cool and lubricate the drill bit, to protect against blowouts by counteracting downhole formation pressure, to maintain a stable borehole, and to prevent loss of fluids to the formations being drilled. Both water-based and oil-based muds are used as drilling muds. Water-based muds (WBMs) are generally cheaper than oil-based muds (OBMs), but the latter possess many operational advantages, particularly for the drilling of high angle, long reach and high pressure/high temperature wells. However, conventional oil-based muds do suffer from a number of undesirable characteristics. For example, the oil may be retained on the drill cuttings, which has unfortunate environmental implications. In addition, the presence of emulsifiers and other oil wetting agents, which are essential components of conventional OBMs (these are usually emulsions of water in oil, and the emulsifiers and wetting agents keep the emulsions stable and useful), 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.
Emulsifiers and oil wetting agents are added to conventional OBMs to emulsify the water phase in the oil phase, and to ensure that all of the solids in the mud are wetted by the oil. Surfactants, solids at the interface, or polymers can be used to stabilise such emulsions, and high levels of water can be stabilised in such muds, whilst maintaining all the other properties required of an oil-based mud, provided that sufficient surfactant is present. Now, the amount of oil in the mud and the oil wetting characteristics of the mud are important parameters affecting the concentration of oil retained on drilling cuttings, and unfortunately the high levels of surfactant often required result in undesirably strong oil wetting characteristics. 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.
Thus, according to the present invention there is provided a method for enhancing the stability of a water-in-oil emulsion, in which method there is added to the emulsion a silane having bonds which are capable of hydrolysing and condensing whereby a cross-linked silicone is formed at the interface between the oil and the water, thereby encapsulating the water droplets and so stabilising the emulsion.
In a second aspect, the invention provides a method for forming a stable water-in-oil emulsion, in which method: oil phase, this being the desired water-in-oil emulsion; and then of hydrolysing and condensing whereby a cross-linked silicone is formed at the interface between the oil and the water, thereby encapsulating the water droplets and so stabilising the emulsion.
The water-in-oil emulsion can be prepared in any convenient way suitable for making a fine dispersion of an aqueous phase in a continuous oil phase, but preferably it is prepared by strong physical agitation of the aqueous and oil components in the presence of a suitable water-in-oil emulsifier.
Suitable emulsifiers include fatty acid soaps such as calcium dioleate, fatty amides such a
REFERENCES:
patent: 4381241 (1983-04-01), Romenesko et al.
patent: 4421656 (1983-12-01), Donatelli et al.
patent: 4853474 (1989-08-01), Bahr et al.
patent: 5707939 (1998-01-01), Patel
Hibbert Julie A.
Smith Philip S.
Cole Monique T.
Schlumberger Technology Corporation
Waggett Gordon G.
Warden Jill
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