Wells – Processes – Cleaning or unloading well
Reexamination Certificate
1999-07-02
2001-09-18
Bagnell, David (Department: 3672)
Wells
Processes
Cleaning or unloading well
C507S266000, C507S267000
Reexamination Certificate
active
06289989
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the use of biodegradable alkoxylation products for cleaning boreholes, drilling equipment and drill cuttings, to an additive containing these alkoxylation products, to a cleaning composition containing this additive and to processes for cleaning boreholes, drilling equipment and drill cuttings.
2. Discussion of Related Art
In the drilling and development of oil and gas occurrences, cleaning steps have to be introduced at various stages to ensure problem-free drilling and production. Thus, after the actual drilling process, the borehole has to be prepared for the production of oil or gas (completion). To this end, an outer tube or casing has to be introduced and cemented in place to stabilize the borehole. The cement is passed through the casing in an aqueous liquid form, emerges at the lower end of the casing and hardens between the borehole wall and the casing. To guarantee optimal cementing, the borehole wall and the casings have to be freed from adhering residues of the drilling mud and adhering fine-particle solids. If this is not done, the layer of concrete is in danger of developing voids or channels which reduce the stability of the concrete. In addition, residues of the drilling mud and the cement together can form a gelatinous mass which prevents the cement from setting so that the stability of the cement jacket is further reduced.
After the casing has been introduced into the borehole, the actual production tube, which is smaller in diameter than the casing, is installed. In addition, a sealing fluid (or packer fluid as it is also known) is introduced between the production tube and the inner wall of the casing. Before this packer fluid is introduced, the annular space between the casing and the production tube is cleaned. In particular, all fine-particle solids still adhering to the wall of the casing or production tube have to be removed to guarantee the performance of the packer fluid.
The choice of the cleaning composition to perform the functions mentioned above is also determined by the nature of the drilling mud used. In principle, drilling muds are divided into water-based types and oil-based types. Oil-based drilling muds are mainly used today either as so-called “true oil muds”, i.e. muds which contain little if any dispersed water, or as so-called invert muds which contain between 5 and 45% by weight of water as dispersed phase, i.e. which form a w/o emulsion. In addition there are water-based o/w emulsions which contain a heterogeneous finely disperse oil phase in a continuous aqueous phase. Petroleum products, such as mineral or diesel oils, are normally used as the oil phase. However, increasingly more stringent ecological requirements have recently led to the development of synthetic oil phases, for example containing esters of certain fatty acids. Drilling muds based on such ester oils are described, for example, in European patents 386 636, 374 671 and 374 672 and show distinctly improved behavior compared with petroleum products in regard to their biological degradability and toxicity. Where drilling muds based on synthetic esters are used, the formation of tacky residues on metal surfaces and on the borehole wall are occasionally observed and can also lead to troublesome deposits.
In The same way as the cement used for the cementing process, the cleaning compositions are pumped downwards through the drill pipe in liquid form, emerge at the bottom of the borehole and are forced upwards through the annular space between the tube and the borehole wall. They detach residues of the drilling muds and solid particles adhering to the surfaces and remove them from the borehole. One such process is described in detail, for example, in WO 94/29570. The compositions are normally used in the form of aqueous or non-aqueous solutions or dispersions. However, they may also be added to the drilling mud in concentrated, solid or liquid form.
Cleaning compositions for the functions described above may be, for example, mixtures of citric acid, pyrophosphate and potassium salts used in solid or dissolved form. These compositions are suitable both for true oil muds and for invert muds. An alternative method is described in European patent 513 899, according to which a fluid containing a dispersed gas phase is used for cleaning boreholes. Under the temperature and pressure conditions prevailing in the borehole, the gas phase forms gas bubbles of a certain size which lead to a turbulent flow of the fluid pumped through the borehole and thus enable the borehole to be mechanically cleaned.
In oil production, deposits of paraffin or asphalt are often formed in the borehole or on the production tubes and reduce output. These deposits have to be removed in the course of stimulation work in order to improve the production rate.
Various solutions have been proposed in the prior art for removing the above-mentioned residues by suitable cleaning compositions. Thus, WO 96/01358 discloses an additive containing an ether amine and/or a base oil, for example an ester, a diester, a surfactant or an olefin, in combination with an alkyl alcohol, preferably a terpene alcohol. This additive is used in the form of an aqueous mixture. WO 95/17244 describes a composition for cleaning surfaces soiled with oil which contain surfactants with HLB values of at least 8 in combination with an oil. Ethoxylated sorbitan fatty acid esters are mentioned as preferred surfactants.
Now, although compositions based on ethoxylated sorbitan fatty acid esters develop a favorable cleaning effect, particularly against the residues occurring where ester-based drilling muds are used, their biological degradability and toxicity do not meet all the requirements of increasingly more stringent environmental legislation.
Accordingly, the problem addressed by the present invention was to provide cleaning compositions for boreholes, drilling equipment or drill cuttings which would show improved ecological compatibility in relation to known compositions for at least the same cleaning performance.
It has now been found that compositions for cleaning boreholes or drilling equipment which contain certain alkoxylation products obtained by reaction of certain OH-containing C
10-22
carboxylic acids or C
10-22
carboxylic acid derivatives with ethylene oxide, propylene oxide and/or butylene oxide are at least comparable in their cleaning performance with the prior art and, at the same time, have improved environmental compatibility.
DE 41 34 973 describes water-based cleaning compositions for hard surfaces which contain between 1.0 and 30% by weight of an alkoxylation product of OH-containing carboxylic acids and/or derivatives thereof with 30 to 85% of ethylene oxide or propylene oxide as nonionic surfactants. However, there is nothing in this document to suggest that the compositions in question would also be suitable for cleaning soiled surfaces which come into contact with drilling muds based on petroleum or synthetic esters. In addition, there is nothing in the document in question to indicate that such compounds would be usable under the extreme conditions encountered in oil boreholes in regard to temperature, pressure and exposure to shear forces and aggressive media, such as salt water.
In a first embodiment, the present invention relates to the use of biodegradable alkoxylation products obtained by reaction of ethylene oxide, propylene oxide and/or butylene oxide with C
10-22
carboxylic acids or C
10-22
carboxylic acid derivatives which, at least in the 9/10 and/or 13/14 position, contain structural units corresponding to general formula (I):
in which
R
1
is a hydrogen atom or an OH group or a group OR
2
, where R
2
is an alkyl group containing 1 to 18 carbon atoms, an alkenyl group containing 2 to 18 carbon atoms or a group corresponding to formula (II):
where R
3
is a hydrogen atom, an alkyl group containing 1 to 21 carbon atoms or an alkylene group containing 2 to 21 carbon atoms, for cleaning boreholes, drilling equipment or dri
Heidbreder Andreas
Herold Claus-Peter
Mueller Heinz
Podubrin Stefan
Schreck Berthold
Bagnell David
Dougherty Jennifer
Drach John E.
Henkel Kommanditgesellschaft auf Aktien
Millson, Jr. Henry E.
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