Earth boring – well treating – and oil field chemistry – Earth boring – Contains intended gaseous phase at entry into wellbore
Reexamination Certificate
2000-04-04
2003-11-18
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Earth boring
Contains intended gaseous phase at entry into wellbore
C507S202000, C507S127000, C507S233000, C516S013000
Reexamination Certificate
active
06649571
ABSTRACT:
BACKGROUND OF THE INVENTION
Such fluids comprise an oleaginous continuous phase, one or more viscosifiers that impart an elevated low shear rate viscosity to the fluid of at least 10,000 centipoise, one or more aphron-generating surfactants, and aphrons.
The book by Felix Sebba entitled “Foams and Biliquid Foams—Aphrons”, John Wiley & Sons, 1987, incorporated herein by reference, is an excellent source on the preparation and properties of aphrons in aqueous fluids. Aphrons are made up of a core which is often spherical of an internal phase, usually liquid or gas, encapsulated in a thin liquid shell of the continuous phase liquid. This shell contains surfactant molecules so positional that they produce an effective barrier against coalescence with adjacent aphrons.
SUMMARY OF THE INVENTION
I have now determined that gas bubbles and microbubbles can be generated in oleaginous liquids by incorporating into the oleaginous liquid a silicone oil and encapsulating a gas therein.
Thus, it is an object of the invention to provide a method of incorporating microbubbles into oleaginous liquids.
It is another object of the invention to provide oil base well drilling and servicing fluids containing microbubbles therein.
It is still another object of the invention to provide a method drilling a well wherein the novel drilling fluid of this invention is used as the re-circulateable drilling fluid.
These and other objects of the invention will be apparent to one skilled in the art upon reading the specification and claims hereof.
While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof will hereinafter be described in detail and shown by way of example. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the invention is to cover all modifications and alternatives falling within the spirit and scope of the invention as expressed in the appended claims.
The compositions can comprise, consist essentially of, or consist of the stated materials. The method can comprise, consist essentially of, or consist of the stated steps with the stated materials.
PREFERRED EMBODIMENTS OF THE INVENTION
In its broadest aspects, the present invention is directed to a method of incorporating microbubbles in oleaginous liquids preferably for use as oil base well drilling and servicing fluids (hereinafter sometimes referred to as “OBWDAS” fluids).
The method comprises adding a silicone oil to the oleaginous liquid and thereafter subjecting the silicone oil-containing oleaginous liquid to mechanical forces in the presence of a gaseous phase. The base oleaginous liquid may be any organic, water insoluble liquid which can be viscosified to the desired extent. Exemplary oleaginous liquids known in the art include petroleum oils or fractions thereof, vegetable oils, and various synthetic organic liquids such as olefins (alpha and internal unsaturation), oligomers of unsaturated hydrocarbons, carboxylic acid esters, phosphoric acid esters, ethers, polyalkyleneglycols, diglymes, acetals, and the like.
Microbubbles are generated in the oleaginous liquid by incorporating a silicone oil in the oleaginous liquid and thereafter subjecting the silicone-containing oleaginous liquid to mechanical forces in the presence of a gaseous phase to generate the microbubbles.
The microbubbles can be generated by means known in the art. In addition to the methods disclosed by Felix Sebba in his book referenced previously, methods are disclosed in Michelsen et al. U.S. Pat. No. 5,314,644, incorporated herein by reference, Yoon et al. U.S. Pat. No. 5,397,001, incorporated herein by reference, Kolaini U.S. Pat. No. 5,783,118, incorporated hereby by reference, Wheatley et al. U.S. Pat. No. 5,352,436, incorporated herein by reference, and U.S. Pat. Nos. 4,162,970; 4,112,025; 4,717,515; 4,304,740; and 3,671,022, each incorporated herein by reference.
High shear mixing wherein a vortex is created in the presence of a gas will entrap gas bubbles in the silicone-containing oleaginous liquid.
Mixing wherein the silicone-containing oleaginous liquid is pumped through an orifice in the presence of a gas wherein the liquid is subjected to a large pressure drop of at least 500 psi, such as from 500 to 5000 psi or more, will generate microbubbles in the oleaginous liquid.
When the silicone-containing oleaginous liquid is used as a well drilling and servicing fluid, microbubbles will also be produced by the pressure drop and cavitation as the fluid is pumped through the drill bit.
The gas used to create the microbubbles may be any gas which is not appreciably soluble in the oleaginous liquid. Thus the gas may be air, nitrogen, carbon dioxide, and the like, including air encapsulated in the fluid during mixing.
The silicone oils useful in the invention are well known in the art and available commercially from such companies as GE Silicones, HULS AMERICA, INC., DOW CORNING, and CK WITCO. The silicone oils are basically siloxane polymers which have a backbone of Si—O linkages. Dimethyl silicone fluids, i.e., polydimethylsiloxanes, are available in various viscosity grades from about 0.5 centistokes at 25° C. to about 2,500,000 centistokes having average molecular weights from about 100 to about 500,00, preferably from about 5 centistokes to about 100,000 centistokes. Also available are polydialkylsiloxanes, polydiphenylsiloxanes, poly(dimethyl/diphenyl)siloxanecopolymers, and polymethyl-alkylsiloxanes, such as polymethyloctylsiloxane and polymethyloctadecylsiloxane.
The concentration of silicone oil required is generally from about 0.5 ppb (0.06 g/cm
3
) to about 20 ppb (2.4 g/cm
3
), preferably from about 1 ppb (0.12 g/cm
3
) to about 10 ppg (1.2 g/cm
3
). An indication of the volume of microbubbles generated can be obtained by determining the density reduction which occurs upon generating the microbubbles in the fluid. Foaming of the fluid, which is undesirable, may occur if the concentration of silicone oil is excessive. We have determined that the concentration of silicone oil can be increased, without any adverse effect on the fluid, as the LSRV increases. Thus the concentration of silicone oil, which can be determined by routine testing, is the amount required to generate sufficient microbubbles to give the density reduction desired but which is, preferably, insufficient to create a long-lasting foam on the surface of the fluid. The concentration of aphrons in the fluid is preferably from about 5% by volume to about 25%, most preferably from about 5% to about 20% by volume.
The density of the fluids can be adjusted, as required, by the addition of weight materials or the addition of soluble salts to the fluids as is well known in the art. Preferably the weight material is added to the fluid before generation or incorporation of microbubbles therein, thus adjusting the final density of the microbubble-containing fluid to the desired density by the concentration of microbubbles therein.
As indicated, the concentration of microbubbles in the fluid should be less than about 25% by volume at atmospheric pressure. However, on circulation of the fluid in a borehole, the volume of the microbubbles is believed to decrease as the hydrostatic pressure of the fluid increases. Indeed the microbubbles may compress in size to almost no volume depending on the depth of the borehole. The measured density under pressure should be very close to the density of the fluid without any microbubbles. The microbubles do not disappear, however. They are still present, and additional microbubbles will be generated at the face of the bit due to the pressure drop and cavitation. The microbubbles are extremely small, have very high surface area, and are highly energized.
As soon as the fluid exits the bit and starts back up the annulus, some pressure drop begins to occur and the microbubbles will begin to expand. As the fluid moves up the borehole and it encounters a loss to the formation, the microbubbles are filtered into the pore throats, m
Conley & Rose, P.C.
Masi Technologies, L.L.C.
Payne, Esq. Leslie V.
Tucker Philip
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