Earth boring – well treating – and oil field chemistry – Earth boring – Contains intended gaseous phase at entry into wellbore
Patent
1996-06-07
1998-10-13
Tucker, Philip
Earth boring, well treating, and oil field chemistry
Earth boring
Contains intended gaseous phase at entry into wellbore
507111, 507113, 507140, 507141, 507145, 166309, C09K 702
Patent
active
058212035
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP95/03102 filed Aug. 4, 1995.
The present invention is directed to novel foamed drilling fluids, their preparation and their use. The present invention relates also to a method for breaking a foamed drilling fluid.
Drilling fluids have been used for decades in the oilfield industry. As it is well known, such fluids are mainly based on a water and clay mixture plus various additives aimed at adjusting their rheology and suspending properties.
The general composition and properties of drilling fluids (or drilling muds) are well known of the skilled man and shall not be repeated here.
In the past decade, mixed metal hydroxides (or "MMH") have been developed, especially with reference to J. L. Burba et al in U.S. Pat. No. 4,664,843 and U.S. Pat. No. 4,790,954, whose teaching is incorporated herein by reference.
Drilling fluids incorporating MMH are disclosed in EP-A-501069. The said fluids are made of MMH and a mineral clay, especially bentonite, so as to impart the desired rheological properties to the fluid, and of an effective amount of a fluid loss control additive which can be generically described as a carboxymethyl substituted starch (cross-linked or not) or cellulosic compound, having a defined degree of substitution, and water plus other common additives.
With that technology, density can be as low as about 8.5 ppg (1.02 g/cm.sup.3) without oil or about 7.9 ppg (0.95 g/cm.sup.3) with some 40% by volume of emulsified diesel oil.
Currently there are not known low density recirculating drilling fluids. In situations where low densities are required, the industry is forced to use air or foam drilling techniques. However, such conventional foamed drilling fluids are normally not circulated.
One foam process has been proposed which relies on a pH sensitive foaming agent: the foam is chemically broken on surface with an acid, the solids are removed, the pH is adjusted back to basic then the fluid is refoamed and pumped back downhole. This "chemical" process is of a complex nature, requires additional products to twice adjust the pH, and does not address static suspension of the cuttings or well bore support. Each one of these drawbacks is serious.
There exists a definite need in the oilfield industry, and similar industries such as geothermal wells and depleted or low pressure reservoir etc . . . , for low density drilling fluids.
However, this need was never matched in the past, or only with drawbacks so serious that the practical use on the field was barely possible or only with serious associated problems.
It is an object of the present invention to provide drilling fluids covering a wide range of low densities, in particular from about 2.0 ppg (0.24 g/cm.sup.3) to 8.0 ppg (0.96 g/cm.sup.3).
It is a further object of the present invention to provide such drilling fluids under the form of a foam.
It is a further object of the present invention to provide a method for preparing such drilling fluids, and for using them for drilling operations.
A further object of the present invention is to provide a method for mechanically breaking a foamed drilling fluid, which method can be incorporated into the above mentioned method for drilling a well.
It has been surprisingly discovered that the use of metal hydroxides in a foamed drilling fluid allows to reach low densities of the foamed fluid while maintaining very efficient rheological and suspending properties.
The source of metal hydroxide can be a single metal hydroxide, or a blend of such metal hydroxides, for example aluminium hydroxide and/or magnesium hydroxide and/or similar hydroxides, or mixed metal hydroxides such as disclosed in the prior art, or precursors of such hydroxides (for example a metal oxide to be used in basic conditions).
According to a preferred embodiment, said metal hydroxide component is a mixed metal layered hydroxide compound of the following empirical formula: Cu, Zn, most preferably Mg, or mixtures thereof; and most preferably about 1; Al; inorganic ions such as: halide, sulphate, nitrate, phosphate
REFERENCES:
patent: 3323593 (1967-06-01), Foshee et al.
patent: 4088583 (1978-05-01), Pyle et al.
patent: 4092252 (1978-05-01), Fischer et al.
patent: 5565416 (1996-10-01), Wu
Gray, Composition and Properties of Oil Well Drilling Fluids, Fourth Edition, p. 331, (1980).
Barbo Douglas Y.
Dowell, a division of Schlumberger Technology Corporation
Tucker Philip
Vick, Jr. John E.
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