USE OF A PROCESS FLUID WITH AN ENVIRONMENTALLY COMPATIBLE BIOSTABILIZER IN A GEOTHERMAL BOREHOLE

Abstract

The present invention relates to the use of a process fluid with an environmentally compatible biostabilizer in a geothermal borehole. The biostabilizer is characterized in that it comprises at least one organic acid, or a salt, alcohol or aldehyde thereof, wherein the at least one organic acid is selected from the group consisting of hop acids, resin acids, fatty acids and mixtures thereof. The biostabilizer is preferably a mixture of hop extract, rosin and myristic acid. The invention further relates to related process fluids and methods for producing the same.

Claims

1. A method comprising the step of pumping a process fluid into a geothermal borehole, wherein the process fluid comprises an environmentally compatible biostabiliser adapted for use in the process fluid to reduce microorganisms within the geothermal borehole, wherein the biostabiliser comprises at least one organic acid, or a salt, alcohol, or aldehyde thereof, wherein the at least one organic acid is selected from the group consisting of hop acids, resin acids, fatty acids, and mixtures thereof; wherein the process fluid comprises water, and a water hardness of the process fluid is at most 20° dH (German hardness).

2. The method according to claim 1, wherein the process fluid is used as a drilling fluid in the geothermal borehole.

3. The method according to claim 1, wherein the process fluid further comprises at least one defoamer.

4. The method according to claim 3, wherein the process fluid further comprises at least one gelling agent, wherein the gelling agent is a biopolymer or a polymeric derivative thereof.

5. The method according to claim 4, wherein the process fluid further comprises a water-softening agent.

6. The method according to claim 1, wherein the biostabiliser comprises: at least one resin acid, or a salt, alcohol, or aldehyde thereof, and at least one fatty acid, or a salt, alcohol, or aldehyde thereof.

7. The method according to claim 1, wherein the biostabiliser is a mixture of at least two of the following components: hop extract, natural resin, and myristic acid or a salt thereof.

8. The method according to claim 7, wherein the biostabiliser is obtainable by adding at least two of the following components: hop extract, natural resin, and myristic acid or a salt thereof.

9. The method according to claim 1, wherein the biostabiliser comprises: a hop acid, selected from the group consisting of humulone, isohumulone, cohumulone, adhumulone, prehumulone, posthumulone, tetrahydroisohumulone, and tetrahydrodeoxyhumulone, lupulone, colupulone, adlupulone, prelupulone, postlupulone, hexahydrocolupulone, and hexahydrolupulone; or a resin acid selected from the group consisting of pimaric acid, neoabietic acid, abietic acid, dehydroabietic acid, levopimaricacid, and palustrinic acid; or a fatty acid selected from the group consisting of capric acid, undecylenic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachinic acid, behenic acid, lignoceric acid, cerotic acid, palmitoleinic acid, oleic acid, elaidic acid, vaccenic acid, icosenoic acid, cetoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, arachidonic acid, timnodonic acid, clupanodonic acid, and cervonic acid.

10. The method according to claim 6, wherein: a total concentration of resin acids in the process fluid is 0.05-5000 ppm and a total concentration of fatty acids in the process fluid is 0.05-5000 ppm.

11. The method according to claim 1, wherein the process fluid further comprises at least one additional antimicrobial agent and/or biostabiliser.

12. The method of claim 1, further comprising biostabilising the geothermal borehole by pumping the process fluid into the geothermal borehole.

13-17. (canceled)

18. The method according to claim 1, wherein the process fluid further comprises at least one gelling agent, wherein the gelling agent is a polysaccharide of one of a starch, vegetable gum, xanthan, cellulose, polyanionic cellulose, or pectin.

19. The method according to claim 1, wherein the process fluid further comprises at least one of acetic acid, lactic acid, propionic acid, benzoic acid, sorbic acid, formic acid, and salts.

20. The method according to claim 1, wherein the water hardness of the process fluid is at most 15° dH (German Hardness).

21. The method according to claim 1, wherein the water hardness of the process fluid is at most 10° dH (German Hardness).

22. The method according to claim 1, wherein the water hardness of the process fluid is at most 7.5° dH (German Hardness).

23. The method according to claim 1, wherein the water hardness of the process fluid is at most 5° dH (German Hardness).

24. A process fluid for a geothermal borehole comprising: an environmentally compatible biostabiliser adapted for use in the process fluid to reduce microorganisms within the geothermal borehole, the biostabiliser comprising at least one organic acid, or a salt, alcohol, or aldehyde thereof, wherein the at least one organic acid is selected from the group consisting of hop acids, resin acids, fatty acids, and mixtures thereof; wherein the process fluid comprises water, and a water hardness of the process fluid is at most 20° dH (German Hardness).

25. A process for preparing a process fluid comprising an environmentally compatible biostabilizer adapted for use in the process fluid to reduce microorganisms within a geothermal borehole, the process comprising adding at least one organic acid or a salt, alcohol, or aldehyde thereof to water or a water-containing portion of the process fluid, wherein a water hardness of the process fluid is at most 20° dH (German Hardness), and wherein the at least one organic acid is selected from the group consisting of hop acids, resin acids, fatty acids, and mixtures of two or all of them, to obtain the process fluid.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0084] The present invention is further illustrated by the following figures and examples, to which it will of course not be limited.

[0085] FIGS. 1A-1M: Effect of the biostabilisers on Halanaerobium congolense. In accordance with example 4, the strain DSM 11287 was exposed to biostabiliser A (hop acid) or to biostabiliser B (resin acid/myristic acid) in various concentrations. Shown is the (A) growth curve without biostabiliser; growth curve at (B) 0.5 ppm, (C) 1 ppm, (D) 10 ppm, (E) 50 ppm, (F) 100 ppm, (G) 250 ppm of biostabiliser A; and growth curve at (H) 0.5 ppm, (I) 1 ppm, (J) 10 ppm, (K) 50 ppm, (L) 100 ppm, (M) 250 ppm of biostabiliser B. The dose-dependent tendency towards biostabilisation is clearly evident.

[0086] FIGS. 2A-2M: Effect of the biostabilisers on Halolactibacillus miurensis. In accordance with example 4, the strain DSM 17074 was exposed to biostabiliser A (hop acid) or to biostabiliser B (resin acid/myristic acid) in various concentrations. Shown is the (A) growth curve without biostabiliser; growth curve at (B) 0.5 ppm, (C) 1 ppm, (D) 10 ppm, (E) 50 ppm, (F) 100 ppm, (G) 250 ppm of biostabiliser A; and growth curve at (H) 0.5 ppm, (I) 1 ppm, (J) 10 ppm, (K) 50 ppm, (L) 100 ppm, (M) 250 ppm of biostabiliser B. The dose-dependent tendency towards biostabilisation is clearly evident.

[0087] FIGS. 3A-3M: Effect of the biostabilisers on Halolactibacillus halophilus. In accordance with example 4, the strain DSM 17073 was exposed to biostabiliser A (hop acid) or to biostabiliser B (resin acid/myristic acid) in various concentrations. Shown is the (A) growth curve without biostabiliser; growth curve at (B) 0.5 ppm, (C) 1 ppm, (D) 10 ppm, (E) 50 ppm, (F) 100 ppm, (G) 250 ppm of biostabiliser A; and growth curve at (H) 0.5 ppm, (I) 1 ppm, (J) 10 ppm, (K) 50 ppm, (L) 100 ppm, (M) 250 ppm of biostabiliser B. The dose-dependent tendency towards biostabilisation is clearly evident.

[0088] FIGS. 4A-4C: Effect of hop acids compared to the chemical biocide methylenbis[5-methyloxazolidine] on Halolactibacillus miurensis. In accordance with example 5, the strain DSM 17074 was exposed to a hop acid containing hop extract or to the biocide 3,3′-methylenbis[5-methyloxazolidine] known in the art in various concentrations. Shown is the (A) growth curve without biostabiliser; (B) growth curves at 10, 25 or 50 ppm methylenbis[5-methyloxazolidine]; (C) growth curves at 10, 25 or 50 ppm hop acids. The dose-dependent tendency towards biostabilisation is clearly evident. Furthermore, it can be seen from the figures that the biostabilising effect of hop acids on Halolactibacillus miurensis is surprisingly stronger even at lower concentrations of for example 10 ppm than in the case of the chemical biocide methylenbis [5-methyloxazolidine].

[0089] FIGS. 5A-5C: Effect of hop acids compared to the chemical biocide methylenbis[5-methyloxazolidine] on Halolactibacillus halophilus. In accordance with example 5, the strain DSM 17074 was exposed to a hop acid containing hop extract or to the biocide 3,3′-methylenbis [5-methyloxazolidine] known in the art in various concentrations. Shown is the (A) growth curve without biostabiliser; (B) growth curves at 5, 10, 25, 50, 100, 200, 1000, 2000 or 5000 ppm methylenbis[5-methyloxazolidine]; (C) growth curves at 0.25, 0.5, 20, 100 or 200 ppm hop acids. The dose-dependent tendency towards biostabilisation is clearly evident. Furthermore, it can be seen from the figures that the biostabilising effect of hop acids on Halolactibacillus halophilus is surprisingly stronger even at lower concentrations of for example 20 ppm than in the case of the chemical biocide methylenbis[5-methyloxazolidine] at for example 25 ppm.

EXAMPLES

Example 1A

[0090] Preparation of the inventive process fluid as a drilling fluid for a geothermal borehole For a geothermal borehole, 750000 L of process fluid with a biostabiliser were provided as a drilling fluid:

[0091] The following substances were added to 720000 L of water: hop acid extract as a biostabiliser (700 kg of a 10% alkaline hop acid solution for a hop acid concentration of 1 g/l). 61000 kg potassium carbonate to inhibit drilled solids; 18000 kg polyanionic cellulose (PAC) and 2250 kg xanthan.

[0092] In addition, the following substances were added: 4000 kg of citric acid, 1500 kg of soda, 3000 kg of bentonite and 720 L of defoamer on a fatty alcohol oxylate base.

Example 1B

[0093] Inventive use of the process fluid as a drilling fluid in a geothermal borehole

[0094] When using a drilling fluid with the biostabiliser of Example 1A at a geothermal borehole in a drilling depth of 750-3200 m, microbiological contamination has been significantly reduced and the adverse effects such as odor, change in viscosity of the drilling fluid or degradation of xanthan can be prevented.

[0095] The microbiological tests were carried out on platecount agar by plating 100 μl of a drilling fluid sample and incubating for two days at 37° C. (the microbiological load is indicated in CFU =colony forming units per ml drilling fluid):

[0096] Day 1 Start of the second bore section (750 m depth). Drilling fluid of Example 1A, but without biostabiliser and defoamer, was used

[0097] Day 11 Sampling from drilling fluid—bacterial growth overgrown agar, CFU therefore not well defined but surely far more than 3000. Among other things, a significant proportion of bacteria of the genera Microbacterium and Dietzia was present in the sample, as determined by sequencing. The drilling fluid of Example 1A with biostabiliser, but without defoamer, was now used. Unexpectedly it was shown that the use of a defoamer was advantageous so that after a short time the drilling fluid of Example 1A (i.e. with biostabiliser and defoamer) was used.

TABLE-US-00001 Day 18 >300 CFU/ml Day 21 93 CFU/ml Day 29 13 CFU/ml Day 37 14 CFU/ml Day 43 19 CFU/ml Day 50 18 CFU/ml Day 61 End of drilling

[0098] Thus, it has surprisingly been found that the process fluid with the biostabiliser according to the invention is also effective as a drilling fluid in a geothermal drilling, particularly against bacteria of the genera Microbacterium and Dietzia.

Example 2

[0099] Biostabilising effect on Halanaerobium

[0100] Preparation of the growth medium:

[0101] Trace element stock solution: Add 1.50 g of nitrilotriacetic acid to 1 L distilled water, adjust pH to 6.5 with KOH. Then add: MgSO.sub.4×7 H.sub.2O 3 g, MnSO.sub.4×H.sub.2O 0.50 g, NaCl 1 g, FeSO.sub.4×7 H.sub.2O 0.10 g, CoSO.sub.4×7 H.sub.2O 0.18 g, CaCl.sub.2×2 H.sub.2O 0.10 g, ZnSO.sub.4×7 H.sub.2O 0.18 g, CuSO.sub.4×5 H.sub.2O 0.01 g, KAl(SO.sub.4).sub.2×12 H.sub.2O 0.02 g, H.sub.3BO.sub.3 0.01 g, Na.sub.2MoO.sub.4×2 H.sub.2O 0.01 g, NiCl.sub.2×6 H.sub.2O 0.03 g, Na.sub.2SeO.sub.3×5 H.sub.2O 0.30 mg and Na.sub.2WO.sub.4×2 H.sub.2O 0.40 mg, adjust pH to 7 with KOH.

[0102] Medium basis: Add NH.sub.4Cl 1 g, K.sub.2HPO.sub.4 0.3 g, KH.sub.2PO.sub.4 0.3 g, MgCl.sub.2×6 H.sub.2O 10 g, CaCl.sub.2×2 H.sub.2O 0.1 g, KCl 1 g, sodium acetate 0.5 g, cysteine 0.5 g, trypticase 1 g, yeast extract 1 g, NaCl 100 g, trace element stock solution 1 ml and resazurin 0.001 g to 1 L of distilled water.

[0103] Boil the medium basis, cool down under N.sub.2:CO.sub.2 (80:20 v/v). Aliquot under N.sub.2:CO.sub.2 (80:20 v/v) in culture tubes and autoclave. Add to sterile medium basis the following sterile stock solutions up to the concentrations shown in parenthesis: 2% Na.sub.2S×9 H.sub.2O (0.2 ml/10 ml), 10% NaHCO.sub.3 (0.2 ml/10 ml), 1M glucose (0.2 ml/10 ml) and 1M sodium thiosulphate (0.2 ml/10 ml). Optionally adjust pH to 7. Like this, the growth medium is obtained.

[0104] Halanaerobium congolense (DSM 11287) is obtained from the German Collection of Microorganisms and Cell Cultures (DSMZ). Grow a pre-culture at 42° C. under anaerobic conditions in the growth medium, thereby incubating for 7 days.

[0105] Provide 5 culture tubes (R0-R4), each with 2 ml of growth medium, wherein biostabiliser (in the form of hop extract, rosin in sodium salt solution and myristic acid in sodium salt solution) is added to the growth medium in each culture tube up to the following concentrations:

TABLE-US-00002 Tube Hop Acid Resin Acid [ppm] [ppm] [ppm] Myristic Acid R0  0   0   0 R1  5  25  25 R2  20  100  100 R3 100  500  500 R4 200 1000 1000

[0106] Inoculate the tubes with 20 μl of pre-culture each and then determine, after 1, 2, 3 and 4 days of incubation at the growth conditions mentioned above, the optical density (OD). A lower optical density compared to R0 is found, wherein the density difference to R0 increases with higher biostabiliser concentration. In additon, the amount of respectively produced H.sub.2S can be determined.

Example 3

[0107] Biostabilising effect on Halolactibacillus

[0108] Preparation of the growth medium:

[0109] Add peptone 5 g, yeast extract 5 g, glucose 10 g, KH.sub.2PO.sub.4 1 g, MgSO.sub.4 ×7 H.sub.2O 0.2 g, NaCl 40 g, Na.sub.2CO.sub.3 10 g to 1 L of distilled water. Optionally adjust pH to 9.6.

[0110] Halolactibacillus halophilus (DSM 17073) is obtained from the German Collection of Microorganisms and Cell Cultures (DSMZ). Grow a pre-culture at 30° C. in the growth medium, thereby incubating for 3 days.

[0111] Provide 5 culture tubes (R0-R4), each with 2 ml of growth medium, wherein biostabiliser (in the form of hop extract, rosin in sodium salt solution and myristic acid in sodium salt solution) is added to the growth medium in each culture tube up to the following concentrations:

TABLE-US-00003 Tube Hop Acid Resin Acid Myristic [ppm] [ppm] [ppm] Acid R0 0 0 0 R1 5 25 25 R2 20 100 100 R3 100 500 500 R4 200 1000 1000

[0112] Inoculate the tubes with 20 μl of pre-culture each and then determine, after 1, 2, 3 and 4 days of incubation at the growth conditions mentioned above, the optical density. A lower optical density compared to R0 is found, wherein the density difference to R0 increases with higher biostabiliser concentration.

Example 4

[0113] Biostabilising effect on Halanaerobium and Halolactibacillus

[0114] The effect of selected biostabilisers (hop beta acids or resin acids/myristic acid, biostabiliser A or B) on the growth of three defined bacterial strains (Halanaerobium congolense DSM 11287, Halolactibacillus halophilus DSM 17073, Halolactibacillus miurensis DSM 17074) was analyzed by an in vitro experiment.

[0115] The following aqueous stock solutions for the selected biostabilisers were used: (A) 10% alkaline beta hop acid solution (hop extract) and (B) 20% alkaline solution of resin acids (rosin) and myristic acid (60:40).

TABLE-US-00004 TABLE 1 Culturing Conditions Environmental Strain Culture medium conditions Halanaerobium DSMZ Medium 3 days, congolense No. 933 anaerobic, DSM 11287 (as in Example 2) 42° C. Halolactibacillus DSMZ Medium 48 h, micro- miurensis No. 785 aerophilic, DSM 17074 (as in Example 3) 30° C. Halolactibacillus DSMZ Medium 48 h, micro- halophilus No. 785 aerophilic, DSM 17073 (as in Example 3) 30° C.

[0116] Each of the three test strains was grown for several days before the biostabilising experiments according to table 1. The species identity was checked by sequencing and again by a sequence comparison in public data bases.

[0117] The biostabilising experiments were carried out with the Bioscreen instrument. It involves a special microtiter plate photometer which simultaneously serves as an incubator and can accommodate up to two so-called Honeycomb microtiter plates with 100 wells simultaneously. The determination of the growth is carried out by an OD measurement at 600 nm. During the incubation the Honeycomb microtiter plates were shaken every 15 sec before each measurement with medium strength for 5 sec. The OD measurement was carried out every 15 min.

[0118] In each of the tests carried out two Honeycomb microtiter plates per test strain were used which were each filled according to the same scheme. On the respectively first microtiter plate, the biostabiliser A was tested and on the respectively second plate, the biostabiliser B was tested at concentrations of 0.5 ppm, 1 ppm, 10 ppm, 50 ppm, 100 ppm, and 250 ppm. The concentration data in ppm in this example refer to the final concentration of hop acids in the growth medium (for A) and to the final concentration of resin acids/myristic acid in the growth medium (in the composition 60:40, for B). “ppm” in this example stands for mg of organic acids (i.e. hop acids or resin acids/myristic acid) per kg of solution (i.e. growth medium+additives).

[0119] All test strains were tested sevenfold (i.e. n=7) at each listed biostabiliser concentration. To this purpose, the respective biostabiliser concentrations were investigated in parallel with each bacterial strain in seven wells of the Honeycomb microtiter plate. In addition, three wells per biostabiliser concentration were included as control means, i.e. instead of the bacterial suspension, sterile water was pipetted into the wells. In addition, seven wells were carried out without biostabiliser on each plate for further control to detect the typical growth of each strain under the chosen test conditions. Sterility control included three additional wells each per biostabiliser and bacterial strain (medium without biostabiliser and without bacterial suspension).

[0120] In each well, the respective growth medium according to table 1, bacterial suspension (or sterile water at the appropriate controls) and the biostabiliser solution were pipetted at the appropriate concentration. To create a strictly anaerobic atmosphere for Halanaerobium congolense, the growth medium was mixed with oxyrase (oxygen removing enzyme). By mixing all of the components, the respectively desired biostabiliser concentrations were achieved. Subsequently, all wells were overlaid with 2-3 drops of sterile paraffin oil. This served to maintain the anaerobic conditions for Halanaerobium congolense and to create microaerophilic conditions for Halolactibacillus miurensis and Halolactibacillus halophilus.

[0121] Composition of each volume in the wells of the microtiter plate (for Halanaerobium congolense)

[0122] 300 μ1.25×growth medium (DSMZ No. 933)

[0123] 50 μbacterial suspension

[0124] 10 μOxyrase® (Oxyrase Inc., Ohio, USA)

[0125] 10 μbiostabiliser solution at an appropriate concentration

[0126] 2-3 drops of paraffin for overcoating

[0127] Composition of each volume in the wells of the microtiter plate (for the other three strains)

[0128] 300 μl 1.25×growth medium (DSMZ No. 785 or CASO)

[0129] 50 μl bacterial suspension

[0130] 10 μl biostabiliser solution at an appropriate concentration

[0131] 2-3 drops of paraffin for overcoating

[0132] The respective growth curves are shown in the figures and show a strong concentration-dependent influence on the growth of the test strains by the biostabilisers. At higher concentrations of the biostabilisers it comes to an opacification of the growth medium (i.e. higher initial OD value—for an assessment of the biostabilising effect, it is not the initial OD value which is relevant, but the course of the growth curve or the OD gain)—and occasionally to aberrations (because the biostabiliser occasionally precipitates out of solution), yet the dose-dependent tendency towards biostabilisation is clearly evident from the figures.

[0133] In most tested biostabiliser/test strain combinations, a concentration of 0.5 ppm is already causing an influence on the growth (lower OD gain or delayed reaching the maximum OD). A complete inhibition of growth (i.e. no OD enhancing growth occurs any more) appeared strain-individually mostly at 10 ppm or 50 ppm of biostabiliser concentration (see Table 2).

[0134] Under the test conditions, the biostabilisers A and B were able to inhibit the growth of the tested bacteria, i.e. to act biostabilising.

TABLE-US-00005 TABLE 2 Minimum biostabiliser concentration for total growth inhibition. A: hop acids, B: resin acids/myristic acid (60:40) Strain Biostabiliser A [ppm] Biostabiliser B [ppm] Halanaerobium congolense 10 100 DSM 11287 Halolactibacillus miurensis 50 10 DSM 17074 Halolactibacillus halophilus 1 250 DSM 17073

Example 5

[0135] Comparative example

[0136] The biostabilising effect of hop acids compared to the chemical biocide methylenbis[5-methyloxazolidine] known in the art and used in a large technical scale, on Halolactibacillus. This test was operated essentially in accordance with example 4 (except in respect of the biostabilisers and the concentrations of them). The results of these investigations are shown in FIG. 4A-4C and 5A-5C. The dose-dependent tendency towards biostabilisation by hop acids is clearly evident. Furthermore it has surprisingly been shown during the investigations that the biostabilising effect of hop acids on Halolactibacillus is stronger even at lower concentrations than in the case of the chemical biocide methylenbis[5-methyloxazolidine] (see FIG. 4B-4C and 5B-5C).

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