GB2099884A - A method of boring holes - Google Patents
A method of boring holes Download PDFInfo
- Publication number
- GB2099884A GB2099884A GB8117317A GB8117317A GB2099884A GB 2099884 A GB2099884 A GB 2099884A GB 8117317 A GB8117317 A GB 8117317A GB 8117317 A GB8117317 A GB 8117317A GB 2099884 A GB2099884 A GB 2099884A
- Authority
- GB
- United Kingdom
- Prior art keywords
- mixture
- drill string
- hole
- drill
- foam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000006260 foam Substances 0.000 claims abstract description 34
- 239000000203 mixture Substances 0.000 claims abstract description 25
- 229920000642 polymer Polymers 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000005187 foaming Methods 0.000 claims abstract description 11
- 239000004094 surface-active agent Substances 0.000 claims abstract description 10
- 238000011010 flushing procedure Methods 0.000 claims description 20
- 238000005520 cutting process Methods 0.000 abstract description 15
- 238000001816 cooling Methods 0.000 abstract description 2
- 230000001050 lubricating effect Effects 0.000 abstract description 2
- 230000015572 biosynthetic process Effects 0.000 description 12
- 238000005755 formation reaction Methods 0.000 description 12
- 238000005553 drilling Methods 0.000 description 11
- 239000004927 clay Substances 0.000 description 4
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 230000002706 hydrostatic effect Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 239000004088 foaming agent Substances 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 239000002689 soil Substances 0.000 description 3
- SVTBMSDMJJWYQN-UHFFFAOYSA-N 2-methylpentane-2,4-diol Chemical compound CC(O)CC(C)(C)O SVTBMSDMJJWYQN-UHFFFAOYSA-N 0.000 description 2
- 229920000663 Hydroxyethyl cellulose Polymers 0.000 description 2
- 239000004354 Hydroxyethyl cellulose Substances 0.000 description 2
- 239000000443 aerosol Substances 0.000 description 2
- 239000000440 bentonite Substances 0.000 description 2
- 229910000278 bentonite Inorganic materials 0.000 description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- -1 ethoxylated alkyl sulphate Chemical compound 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 229940071826 hydroxyethyl cellulose Drugs 0.000 description 2
- 235000019447 hydroxyethyl cellulose Nutrition 0.000 description 2
- 238000005461 lubrication Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 229940105329 carboxymethylcellulose Drugs 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 229940051250 hexylene glycol Drugs 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000008258 liquid foam Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000009527 percussion Methods 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000009991 scouring Methods 0.000 description 1
- 239000008257 shaving cream Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000009974 thixotropic effect Effects 0.000 description 1
- 229920001285 xanthan gum Polymers 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/02—Well-drilling compositions
- C09K8/38—Gaseous or foamed well-drilling compositions
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/06—Arrangements for treating drilling fluids outside the borehole
- E21B21/062—Arrangements for treating drilling fluids outside the borehole by mixing components
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/14—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor using liquids and gases, e.g. foams
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- Geochemistry & Mineralogy (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Earth Drilling (AREA)
Abstract
A method of boring a hole using a rotary drill includes foaming a mixture of water, a polymer and a surfactant at a rate not exceeding 0.4 litres per second and injecting the foam at a pressure of between 0.1 and 0.5 bar through the interior of the drill string 6 in a substantially continuous column. The foam flows through apertures in the drill bit 12 thereby lubricating and cooling the drill bit and removing cuttings and then flows upwardly through the annular space between the side of the hole 4 and drill string 6. <IMAGE>
Description
SPECIFICATION
A method of boring holes
The present invention relates to a method of boring holes with a rotary drill, such as oil wells, water wells and holes for geothermal or mineralogical purposes and is particularly concerned with the injection of a flushing medium into the hole whilst it is being bored.
Such holes, which are bored through rock and/or various types of soils, can be almost any depth down to many thousands of metres and it is conventional to inject a flushing medium down inside the interior of the drill string which then passes into the hole through apertures in the drill bit and thence back up the hole in the annular space between the side of the hole and the drill rods comprising the drill string. The most important functions of such a flushing medium are to carry the cuttings loosened by the drill bit to the earth's surface and thus permitting the drill to progress without being impeded by loose cuttings, to cool the drill bit thereby prolong its service life and to lubricate the drill bit to facilitate the formation of the cuttings. The flushing medium also has four further subsidiary functions.The first of these is to control the hydrostatic pressure found in most formations which are drilled.
Provided the hole is kept full of flushing medium it will not fill up with water, oil or gas from the formation. The second is to clean the hole bottom since it is important not only to remove cuttings to the surface but also to remove them as rapidly as possible from the bottom of the hole to expose fresh material to the drill bit. Tests have shown that at high flushing medium densities a problem known as chip hoiddown can occur in which the high pressure acts initially on the upper surface only of the cuttings thus tending to hold them in place against the bottom of the hole. This can lead to the same cutting being cut out by the drill several times which is accompanied by a reduction in drilling progress and an increase in wear of the drill bit.The third subsidiary function of the flushing medium is to provide a method of evaluating the formation through which the hole is being bored since cuttings brought to the earths surface can be analysed. Finally the flushing medium can also protect the formation since tight formations are susceptible to becoming plugged by the flushing medium itself and naturally no flushing medium should be used which will react with the formation to impair its producing ability or the interpretation of measurements carried out on the formation.
Various different flushing media have been used, one of which is air. For this method of drilling one or more high power air compressors are used delivering air typically at pressures of 7 to 1 5 bar. Typically one attempts to achieve an air velocity in the annular space of about 1 5 to 25 metres per second since this is the speed that is required effectively to remove the cuttings. The required output of the compressors will vary in accordance with the size of the hole being drilled but since the diameter of such holes generally lies in the range 0.1 to 1 metre the compressors must generally provide tens of cubic metres per second of compressed air.Air drilling is extremely effective since a compressor producing a 10 bar output pressure will provide about 10 bars also at the bottom of the hole, the additional hydrostatic pressure exerted by the column of air in the drill string being effectively zero. This means that in a hole in which the formation pressure, that is to say the pressure exerted by the formation itself can be as high as 150 bar or more depending on the depth of the hole, there is no problem of chip holddown and the cuttings almost explode off the hole bottom under the high pressure differential.
On the other hand air provides very little in the way of lubrication and the high annular speeds which are used of themselves bring the serious problem that the wall of the hole is severely eroded and the entrained dust particles in the exiting jet of air have resulted in the necessity of providing expensive cylone or other type of dust separators. In addition, air drilling is extremely expensive in the remote jungle or desert areas in which such holes must frequently be bored since the bulky compressors and dust separators must be airfreighted in, as must a generator and/or fuel to provide the necessary high power.
A further flushing medium which is commonly used is so called drilling mud, which is generally based on bentonitic clay. With such clay the annular velocity can be very much lower, typically about 0.1 5 metres per second so the problem of scouring the hole is substantially reduced.
However a substantial volumetric flow rate is still required of the order of about 1 5 to 50 litres/second depending on the size of the hole. To circulate the mud a slurry pump is usedwhich develops a head of about 50 to 140 bar and due to the considerable density of the mud the pressure at the hole bottom can be very considerable indeed, even as high as 200 to 300 bar due to the additional hydrostatic pressure exerted by the column of mud. Whilst such mud is relatively effective at cooling and lubricating the drill bit the pressure of the mud at the hole bottom can lead substantial problems of chip holddown since this pressure can frequently exceed the formation pressure.In addition a separating unit is required to separate the cuttings from the mud if the mud is to be reused and thus a substantial weight of equipment must be transported to the location of the hole and the considerable amount of energy is required to produce the necessary pressure and flow of the drilling mud.
In a still further method, which may be regarded as a development of the air drilling method described above, a liquid foam is mixed with compressed air, the mixture constituting the flushing medium. Such a method is disclosed in
U.S. Patent No. 3493059. In such methods, one or more compressors are used having an output of about 2.5 cubic metres/second at between 7 and
1 5 bar and into which a foam is introduced. Such foam is generally water based and may include either a bentonitic clay or a polymer together with
1 to 5% by weight of foaming agent. The mixture is made up in a tank prior to foaming, withdrawn at a rate typically of about 1 to 1.5 litres/second, foamed and then injected into the compressed air flow.Such a method is relatively advantageous in that it-produces a relatively low pressure at the bottom hole so that chip holddown problems are not severe and it satisfactorily carried away the cuttings. On the other hand it suffers from the disadvantage that a compressor, mechanical foaming device and means for mixing the foam with the compressed air are required with all that these imply as regards weight to be transported to the site together with a relatively heavy consumption of both the foam constituents and power.
Accordingly it is an object of the present invention to devise a method of drilling which utilises a much more economical system of flushing medium injection as regards both power and volume of flushing medium consumed and in particular a method which is economically viable in remote areas to which all machines and materials must be airlifted.
According to the present invention there is provided a method of boring a hole using a rotary drill including injecting a flushing medium through the interior of the drill string which subsequently flows through apertures in the drill bit and thence up through the annular space between the side of the hole and the drill string, the method including foaming a mixture of water, a polymer and a surfactant at a rate not exceeding 0.4 litres per second and injecting the foam at a pressure not exceeding 50 bar, and preferably not exceeding 10 bar or even 5 bar, at ground level in a substantially continuous column down the interior of the drill string.
Thus in its broadest form the invention may be considered as residing in the injection of much
less foam than has previously been used with
lower air volumes than have previously been used without using a compressor to provide a flow of compressed air in which the foam is entrained.
The foam is thus produced at a low rate in a form similar to aerosol shaving foam and slowly passed
at low pressure in the form of a continuous column down the inside of the drill string.
Surprisingly it is found that this low flow rate of
continuous foam will adequately perform all the functions required of a flushing medium and that the high velocity and volumetric flows previously
thought essential to satisfactory drilling are in fact
not essential.
Indeed it has been found that the pressure of
the foam at ground level can be very much less than 50 or even 10 bar, and in the preferred
embodiment this pressure is in the range 0.1 to 1
bar and preferably 0.1 to 0.5 bar. When the
mixture of water, polymer and surfactant is foamed it will increase in volume by a factor of
about 200 to 500 depending on the ratio of the
constituents, the method of foaming and the pressure to which it is subjected. The density of the foam is thus extremely low which means that the additional pressure exerted by the foam by virtue of the hydrostatic head of the column of foam inreases at a rate of only about 0.8 bar per
1000 metres depth of hole. This will mean that
chip holddown is not a significant problem since the chips are rapidly removed from the hole bottom before being removed slowly up through the annular space.
Surprisingly it has been found that the method in accordance with the invention does not rely on any particular minimum foam velocity in the annular space for its success, so the volume of foam which is injected is largely independent of the size of the hole being drilled. Typically however the foam velocity in the annular space is 0.05 to 0.5 metres per second. To ensure that the cuttings are reliably transported by the foam at low speeds the foam is preferably relatively stiff and thus preferably has a consistency similar two that of aerosol shaving cream.
This permits the rate at which the water/polymer/surfactant mixture is foamed to be reduced below 0.4 litres/second to a volume which is still consistent with adequate lubrication and removal of cuttings away from the drill bit, preferably 0.05 to 0.15 litres/second. It will be appreciated that the major advantage of the method in accordance with the invention resides in its economy as compared to the previous methods in that a very much lesser amount of the flushing medium is used and no compressor is required at all. This makes it a relatively simple matter to airlift the necessary equipment to remote areas.In a preferred form of the invention the mixture is made up in a container, is then withdrawn therefrom, foamed and injected into the drill string by a single mechanical unit comprising a pump for withdrawing the mixture and a fan for foaming it and injecting it into the drill string. The pump is preferably of positive displacement type producing a steady output, e.g.
of helical rotor or stator type. Such a mechanical unit may be operated by a motor of about 5 kW power so that the amount of fuel required to operate the method is extremely low.
The mixture preferably includes 0.5 to 4%, preferably 0.7 to 1.5% by weight of surfactant and 0.1 to 1%, preferably 0.2 to 0.6% by weight polymer. The surfactant may be one or more of a number of known foaming agents but is preferably an ethoxylated alkyl sulphate, optionally with traces of hexylene glycol. The polymer, which is preferably added to the mixture in powdered or granularform is preferably high molecular weight hydroxy ethyl cellulose but other polymers may be used in addition or alternatively, such as Xanthum gum of purified carboxy methyl cellulose.
A further advantage of using such polymer foams is that they tend to coat clays on the surface of the hole thus inhibiting swelling of the clay which is a primary cause of the collapse of the hole wall when using watery bentonite muds.
Such polymer foams have virtually no thixotropic properties whereas bentonite muds tend to "set" in the hole if drilling is temporarily halted which necessitates the application of a power surge to restart circulation of the mud. The foam is composed of cross-linked three dimensional tangled chains forming a structure which is too large to permeate into most soil structures and in yiew of the fact that the water in the foam is chemically bound up in it the water cannot seep out into the soil either. This is of particular advantage when drilling a water well, though the foam is in any case completely non-toxic.
The invention also embraces apparatus for carrying out the method and thus according to a further aspect of the present invention there is provided apparatus for boring a hole comprising a rotary drill string including one or more hollow drill rods at the lower end of which is a drill bit having one or more apertures communicating with the interior of the drill string, a container for holding a mixture of water, a polymer and a surfactant, means for withdrawing the mixture from the container at a rate not exceeding 0.4 litres per second and means for foaming the mixture and injecting it into the interior of the drill string in a substantially continuous column at a pressure not exceeding 50 and preferably 10 bar.
Further features and details of the invention will be apparent from the following description of one specific embodiment which is given by way of example only with reference to the accompanying schematic drawing which shows a hole being bored in accordance with the invention.
The single schematic drawing shows a drill string, generally designated 2, within a hole 4 which it has formed. The drill string comprises an appropriate number of drill rods 6 which are coupled by couplings 8 and each of which defines a passage 10 within it. At the lowermost end of the lower drill rod is a conventional drill bit 12 which affords a plurality of apertures (not shown) which communicate with the interior of the drill string. The hole may be of any desired depth whilst its diameter, which is determined by the size of the drill bit is between 0.1 and 1 metre. The diameter of the passage within the drill rods will vary with the size of the drill rods themselves but is generally between 2 and 10 cm.
At the upper end of the upper drill rod and above the ground level 14 is a drive coupling 1 6 by means of which the drill string may be rotated by a motor (not shown). Above the coupling 16 is a fluid coupling 1 8 which permits relative rotation and connects the drill string to a flushing medium pipe 20. The pipe 20 is connected to the outlet of a pump/fan unit 22 whose inlet is connected via a feed pipe 24 to a feed tank 26. The pipe 24 is also connected to a vacuum pump 28 whose function will be described below. The pump/fan unit 22 comprises a low-power monobloc positive displacement helical rotor pump 30 whose outlet is directed at a fan 32.
In use, a measured quantity of water is placed in the feed tank 26 and to this is added 1% by weight of a foaming agent, such as an ethoxylated alkyl sulphate, and 0.4% by weight of a soluble powdered polymer, such as hydroxy ethyl cellulose, the precise choice of the additives and the quantities thereof being determined by the operation conditions, such as the type of drill, the speed of rotation, the type of formation to be drilled and the like. The pump/fan unit is then actuated and the pump 30 withdraws the mixture from the feed tank at a rate of about 0.1 litres/second. The pump 30 delivers the mixture to the fan 32 which is also supplied with air, in this case by the pump 28, and which foams the mixture to produce a foam of specific gravity between 0.005 and 0.002 depending on conditions. The fan then gently forces the foam under a pressure of about 0.3 bar through the pipe 20 and in a substantially continuous column down the interior of the drill string whence it exits through the drill bit and then passes up the annular space between the side of the hole and the drill string carrying all the cuttings with it.
It will be appreciated that a great many modifications may be made to the method and apparatus described above and in particular that the foam constituents, pressures, flow rates and volumes may be altered in accordance with wishes and requirements and that the drill may of course also be a rotary drill exterting a hammer or percussion action.
Claims (9)
1. A method of boring a hole using a rotary drill including injecting a flushing medium through the interior of the drill string which subsequently flows through apertures in the drill bit and thence up through the annular space between the side of the hole and the~drill string, the method including foaming a mixture of water, a polymer and a surfactant at a rate not exceeding 0.4 litres per second and injecting the foam at a pressure not exceeding 50 bar at ground level in a substantially continuous column down the interior of the drill string.
2. A method as claimed in Claim 1 in which the pressure of the foam at ground level is in the range 0.1 to 0.5 bar.
3. A method as claimed in Claim 1 or Claim 2 in
which the speed of the foam in the annular space
is in the range of 0.05 to 0.5 metres per second.
4. A method as claimed in any one of Claims 1
to 3 in which the mixture is foamed at a rate of
between 0.05 and 0.15 litres/second.
5. A method as claimed in any one of the
preceding claims in which the mixture is made up
in a container and is then withdrawn therefrom,
foamed and injected into the drill string by a single
mechanical unit comprising a pump for
withdrawing the mixture and a fan for foaming it
and then injecting it into the drill string.
6. A method as claimed in any one of the
preceding claims in which the mixture contains
0.5 to 4% by weight surfactant and 0.1 to 1% by
weight polymer.
7. Apparatus for boring a hole comprising a
rotary drill string including one or more hollow drill
rods at the lower end of which is a drill bit having one or more apertures communicating with the interior of the drill string, a container for holding a
mixture of water, a polymer and a surfactant,
means for withdrawing the mixture from the
container at a rate not exceeding 0.4 litres per second and means for foaming the mixture and -injecting it into the interior of the drill string in a
substantially continuous column at a pressure not
exceeding 50 bar.
8. Apparatus as claimed in Claim 7 including a pump/fan unit comprising a pump for withdrawing the mixture and a fan for foaming it and then injecting the foam into the drill string.
9. A method of boring a hole using a rotary drill substantially as specifically herein described with reference to the accompanying schematic drawing.
1 0. Apparatus for boring a hole substantially as specifically herein described with reference to the accompanying schematic drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8117317A GB2099884B (en) | 1981-06-05 | 1981-06-05 | A method of boring holes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8117317A GB2099884B (en) | 1981-06-05 | 1981-06-05 | A method of boring holes |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2099884A true GB2099884A (en) | 1982-12-15 |
| GB2099884B GB2099884B (en) | 1985-04-03 |
Family
ID=10522304
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8117317A Expired GB2099884B (en) | 1981-06-05 | 1981-06-05 | A method of boring holes |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2099884B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0229434A1 (en) * | 1986-01-16 | 1987-07-22 | Pierre Ledent | Process for the improvement of the conditioning of gasification agents utilized in an underground coal-gasification process |
| FR2690709A1 (en) * | 1992-04-30 | 1993-11-05 | Seppic Sa | Tunnel excavation process, use of a foaming agent and new foaming agent. |
| US5513712A (en) * | 1994-11-08 | 1996-05-07 | Marathon Oil Company | Polymer enhanced foam drilling fluid |
| WO1996018802A1 (en) * | 1994-12-16 | 1996-06-20 | Condat S.A. | Material and method for lubricating the metal surfaces of an earth-pressure tunnel boring machine |
-
1981
- 1981-06-05 GB GB8117317A patent/GB2099884B/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0229434A1 (en) * | 1986-01-16 | 1987-07-22 | Pierre Ledent | Process for the improvement of the conditioning of gasification agents utilized in an underground coal-gasification process |
| FR2690709A1 (en) * | 1992-04-30 | 1993-11-05 | Seppic Sa | Tunnel excavation process, use of a foaming agent and new foaming agent. |
| WO1993022538A1 (en) * | 1992-04-30 | 1993-11-11 | Seppic, Societe D'exploitation De Produits Pour Les Industries Chimiques | Method for excavating tunnels, utilisation of a foaming agent and new composition |
| US5513712A (en) * | 1994-11-08 | 1996-05-07 | Marathon Oil Company | Polymer enhanced foam drilling fluid |
| WO1996018802A1 (en) * | 1994-12-16 | 1996-06-20 | Condat S.A. | Material and method for lubricating the metal surfaces of an earth-pressure tunnel boring machine |
| FR2728298A1 (en) * | 1994-12-16 | 1996-06-21 | Condat Sa | PRODUCT AND METHOD FOR LUBRICATING THE METAL SURFACES OF AN EARTH PRESSURE TUNNEL |
| US6287052B1 (en) | 1994-12-16 | 2001-09-11 | Condat S.A. | Material and method for lubricating the metal surfaces of an earth-pressure tunnel boring machine |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2099884B (en) | 1985-04-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |