PROCESS FLUID WITH ENVIRONMENTALLY FRIENDLY BIOSTABILISATOR

Abstract

Provided is a method for hydraulic fracturing in a borehole in a geological formation using a process fluid including an environmentally friendly biostabiliser. The biostabiliser is characterised in that it includes at least one organic acid, or a salt, alcohol or aldehyde thereof, such that the at least one organic acid is selected from the hop acids, resin acids, fatty acids and mixtures thereof.

Claims

1-20. (canceled)

21. A method for hydraulic fracturing in a borehole in a geological formation comprising fuel-containing sediment, the method comprising the following steps: injecting an aqueous fracturing fluid comprising a proppant and a biostabilizer into the borehole, thereby causing cracks in the fuel-containing sediment; pumping up produced water from the borehole, the produced water comprising at least a part of the aqueous fracturing fluid mixed with formation water and fuel from the fuel-containing sediment; and during the pumping up, contacting at least one undesirable microorganism in the produced water with the biostabilizer, thereby inhibiting growth and/or metabolism of the at least one undesirable microorganism; wherein the biostabilizer comprises at least one organic acid, or a salt, alcohol or aldehyde thereof, wherein the at least one organic acid is selected from a group consisting of hop acids, resin acids, fatty acids and mixtures thereof.

22. The method according to claim 21, wherein the produced water is at most 20° dH (German Hardness).

23. The method according to claim 21, wherein the at least one undesirable microorganism is contacted with the biostabilizer at a depth of 1 km to 5 km.

24. The method according to claim 21, wherein the at least one undesirable microorganism is contacted with the biostabilizer at a temperature of 25° C. to 90° C.

25. The method according to claim 21, wherein the at least one undesirable microorganism is a bacterium selected from Halolactibacillus and Halanaerobium.

26. The method according to claim 21, wherein the at least one undesirable microorganism is an archaeum seceted from Methanosarcinales, Methanohalophilus and Methanolobus.

27. The method according to claim 21, wherein at least 10.sup.4 L of the aqueous fracturing fluid are injected into the borehole.

28. The method according to claim 21, wherein the aqueous fracturing fluid further includes at least one gelling agent, wherein the gelling agent is a biopolymer.

29. The method according to claim 28, wherein the biopolymer is a polysaccharide, wherein the polysaccharide is a starch.

30. The method according to claim 21, wherein the aqueous fracturing fluid further comprises at least one substance which is selected from a group consisting of gelling agents, clay stabilizers, friction modifiers, chain breakers, crosslinkers, buffering agents, and water softeners.

31. The method according to claim 21, wherein the biostabilizer comprises a mixture, the mixture consisting of: at least one hop acid, or a salt, alcohol or aldehyde thereof; and at least one fatty acid, or a salt, alcohol or aldehyde thereof; or 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; or at least one hop acid, or a salt, alcohol or aldehyde thereof; and at least one resin acid, or a salt, alcohol or aldehyde thereof.

32. The method according to claim 21, wherein the biostabilizer is a mixture of at least one hop acid, or a salt, alcohol or aldehyde thereof; and 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.

33. The method according to claim 21, wherein the biostabilizer comprises at least one of the following components: hop extract, a natural resin, the natural resin is added in dissolved form, and myristic acid or a salt thereof.

34. The method according to claim 21, wherein the at least one organic acid is a hop acid, wherein the hop acid is an alpha hop acid, selected from a group consisting of humulone, isohumulone, cohumulone, adhumulone, prehumulone, posthumulone, tetrahydroisohumulone, and tetrahydrodeoxyhumulone.

35. The method according to claim 21, wherein the at least one organic acid is a hop acid, wherein the hop acid is a beta hop acid, selected from the group consisting of lupulone, colupulone, adlupulone, prelupulone, postlupulone, hexahydrocolupulone, and hexahydrolupulone.

36. The method according to claim 21, wherein the at least one organic acid is a resin acid, wherein the resin acid is selected from the group consisting of pimaric acid, neoabietic acid, abietic acid, dehydroabietic acid, levopimaric acid, and palustrinic acid.

37. The method according to claim 36, wherein the resin acid is obtained from black pine.

38. The method according to claim 21, wherein the at least one organic acid is a fatty acid, wherein the fatty acid is 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.

39. The method according to claim 21, wherein: a total concentration of hop acids in the fracturing fluid is 0.01-1000 ppm; and/or a total concentration of resin acids in the fracturing fluid is 0.05-5000 ppm; and/or a total concentration of fatty acids in the fracturing fluid is 0.05-5000 ppm.

40. A process fluid for use in the Earth's crust, comprising a biostabilizer, wherein the biostabilizer includes at least one organic acid, or a salt, alcohol or aldehyde thereof, wherein the at least one organic acid is selected from a group consisting of hop acids, resin acids, fatty acids and mixtures thereof.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0103] FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L and 1M: Effect of the biostabilisers on Halanaerobium congolense. In accordance with example 4, the strain DSM 11287 was exposed to biostabiliser I (hop acid) or to biostabiliser II (resin acid/myristic acid) in various concentrations. Shown in FIG. 1A is the growth curve without biostabiliser; shown in FIG. 1B is the growth curve at 0.5 ppm, FIG. 1C is the growth curve at 1 ppm, FIG. 1D is the growth curve at 10 ppm, FIG. 1E is the growth curve at 50 ppm, FIG. 1F is the growth curve at100 ppm, FIG. 1G is the growth curve at 250 ppm of biostabiliser I; and FIG. 1H is the growth curve at 0.5 ppm, FIG. 1I is the growth curve at 1 ppm, FIG. 1J is the growth curve at 10 ppm, FIG. 1K is the growth curve at 50 ppm, FIG. 1L is the growth curve at100 ppm, FIG. 1M is the growth curve at 250 ppm of biostabiliser II. The dose-dependent tendency towards biostabilisation is clearly evident.

[0104] FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2I, 2J, 2K, 2L and 2M: Effect of the biostabilisers on Halolactibacillus miurensis. In accordance with example 4, the strain DSM 17074 was exposed to biostabiliser I (hop acid) or to biostabiliser II (resin acid/myristic acid) in various concentrations. Shown in FIG. 2A is the growth curve without biostabiliser; shown in FIG. 2B is the growth curve at 0.5 ppm, shown in FIG. 2C is the growth curve at 1 ppm, shown in FIG. 2D is the growth curve at 10 ppm, shown in FIG. 2F is the growth curve at 100 ppm, shown in FIG. 2G is the growth curve at 250 ppm of biostabiliser I; and shown in FIG. 2H is the growth curve at 0.5 ppm, shown in FIG. 2I is the growth curve at 1 ppm, shown in FIG. 2J is the growth curve at 10 ppm, shown in FIG. 2K is the growth curve at 50 ppm, shown in FIG. is the growth curve 2L is the growth curve at 100 ppm, shown in FIG. 2M is the growth curve at 250 ppm of biostabiliser II. The dose-dependent tendency towards biostabilisation is clearly evident.

[0105] FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I, 3J, 3K, 3L and 3M: Effect of the biostabilisers on Halolactibacillus halophilus. In accordance with example 4, the strain DSM 17073 was exposed to biostabiliser I (hop acid) or to biostabiliser II (resin acid/myristic acid) in various concentrations. Shown in FIG. 3A is the growth curve without biostabiliser; shown in FIG. 3B is the growth curve at 0.5 ppm, shown in FIG. 3C is the growth curve at 1 ppm, shown in FIG. 3D is the growth curve at 10 ppm, shown in FIG. 3E is the growth curve at 50 ppm, shown in FIG. 3F is the growth curve at 100 ppm, shown in FIG. 3G is the growth curve at 250 ppm of biostabiliser I; and shown in FIG. 3H is the growth curve at 0.5 ppm, shown in FIG. 3I is the growth curve at 1 ppm, shown in FIG. 3J at 10 ppm, shown in FIG. 3K is the growth curve at 50 ppm, shown in FIG. 3L is the growth curve at 100 ppm, shown in FIG. 3M is the growth curve at 250 ppm of biostabiliser II. The dose-dependent tendency towards biostabilisation is clearly evident.

DETAILED DESCRIPTION

Examples

Example 1

Preparation of the Process Fluid According to the Disclosure for Use in Hydraulic Fracturing

[0106] For a bore, 560000 kg of inventive process fluid with biostabiliser (as fracfluid) are provided:

[0107] To 390000 liters of water the following substances are added: hop acid extract (28 kg of a 10% alkaline hop acid solution for a concentration of 5 mg/kg hop acids), rosin and myristic acid extract (140 kg of a 20% alkaline 50:50 solution of rosin and myristic acid for a concentration of 25 mg/kg resin acids and 25 mg/kg myristic acid) and 165000 kg of sintered bauxite as a proppant.

[0108] In addition, the following substances are added: 200 kg of sodium thiosulphate, 250 kg of sodium hydrogen carbonate, 300 kg of choline chloride, 75 kg of diammonium peroxodisulphate, 200 kg of sodium bromate, 100 kg of zirconyl chloride, 3900 kg of starch derivative.

Example 2

Biostabilising Effect on Halanaerobium

[0109] Preparation of the growth medium:

[0110] 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.

[0111] 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.

[0112] 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), 1 M glucose (0.2 ml/10 ml) and 1 M sodium thiosulphate (0.2 ml/10 ml). Optionally adjust pH to 7. Like this, the growth medium is obtained.

[0113] 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.

[0114] 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-00001 Hop Acid Resin Acid Myristic Acid Tube [ppm] [ppm] [ppm] R0 0 0 0 R1 5 25 25 R2 20 100 100 R3 100 500 500 R4 200 1000 1000

[0115] 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 addition, the amount of respectively produced H.sub.2S can be determined.

Example 3

Biostabilising Effect on Halolactibacillus

[0116] Preparation of the growth medium:

[0117] 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.

[0118] 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.

[0119] 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 Hop Acid Resin Acid Myristic Acid Tube [ppm] [ppm] [ppm] R0 0 0 0 R1 5 25 25 R2 20 100 100 R3 100 500 500 R4 200 1000 1000

[0120] 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

Biostabilising Effect on Halanaerobium and Halolactibacillus

[0121] The effect of selected biostabilisers (hop beta acids or resin acids/myristic acid, biostabiliser I or II) 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.

[0122] The following aqueous stock solutions for the selected biostabilisers were used: (I) 10% alkaline beta hop acid solution (hop extract) and (II) 20% alkaline solution of resin acids (rosin) and myristic acid (60:40).

TABLE-US-00003 TABLE 1 Culturing Conditions Culture Environmental Strain medium conditions Halanaerobium DSMZ Medium No. 933 3 days, anaerobic, congolense (as in Example 2) 42° C. DSM 11287 Halolactibacillus DSMZ Medium No. 785 48 h, microaerophilic, miurensis (as in Example 3) 30° C. DSM 17074 Halolactibacillus DSMZ Medium No. 785 48 h, microaerophilic, halophilus (as in Example 3) 30° C. DSM 17073

[0123] 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.

[0124] 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 werde shaken every 15 sec before each measurement with medium strength for 5 sec. The OD measurement was carried out every 15 min.

[0125] 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 first microtiter plate, the biostabiliser I was tested and on the second plate, the biostabiliser II 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 I) and to the final concentration of resin acids/myristic acid in the growth medium (in the composition 60:40, for II). “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).

[0126] 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).

[0127] 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.

[0128] Composition of each volume in the wells of the microtiter plate (for Halanaerobium congolense)

[0129] 300 μl 1.25×growth medium (DSMZ No. 933)

[0130] 50 μl bacterial suspension

[0131] 10 μl Oxyrase® (Oxyrase Inc., Ohio, USA)

[0132] 10 μl biostabiliser solution at an appropriate concentration

[0133] 2-3 drops of paraffin for overcoating

[0134] Composition of each volume in the wells of the microtiter plate (for the other three strains)

[0135] 300 μl 1.25×growth medium (DSMZ No. 785 or CASO)

[0136] 50 μl bacterial suspension

[0137] 10 μl biostabiliser solution at an appropriate concentration

[0138] 2-3 drops of paraffin for overcoating

[0139] 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.

[0140] 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).

[0141] Under the test conditions, the biostabilisers I and II were able to inhibit the growth of the tested bacteria, i.e. to act biostabilising.

TABLE-US-00004 TABLE 2 Minimum biostabiliser concentration for total growth inhibition. Biostabiliser Biostabiliser Strain I [ppm] II [ppm] Halanaerobium 10 100 congolense DSM 11287 Halolactibacillus 50 10 miurensis DSM 17074 Halolactibacillus 1 250 halophilus DSM 17073 I: hop acids, II: resin acids/myristic acid (60:40)

Example 5A

Preparation of the Process Fluid According to the Disclosure as a Drilling Fluid for Geothermal Drilling

[0142] For a geothermal bore, 750000 L of process fluid with a biostabiliser were provided as a drilling fluid:

[0143] 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.

[0144] 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 basis.

Example 5B

Inventive Use of the Process Fluid as a Drilling Fluid in Geothermal Drilling

[0145] When using a drilling fluid with the biostabiliser of Example 5A 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.

[0146] 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):

TABLE-US-00005 Day 1 Start of the second bore section (750 m depth). Drilling fluid of Example 5A, but without biostabiliser and defoamer, was used 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 5A 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 5A (i.e. with biostabiliser and defoamer) was used. 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 the drilling

[0147] Thus, it has surprisingly been found that the process fluid with the biostabiliser according to the disclosure is also effective as a drilling fluid in a geothermal drilling, particularly against bacteria of the genera Microbacterium and Dietzia.

[0148] Cited non-patent-literature: [0149] Ashraf et al. “Green biocides, a promising technology: current and future applications to industry and industrial processes.” Journal of the Science of Food and Agriculture 94.3 (2014): 388-403 [0150] Cluff, Maryam A., et al. “Temporal Changes in Microbial Ecology and Geochemistry in Produced Water from Hydraulically Fractured Marcellus Shale Gas Wells.” Environmental science & technology (2014) [0151] Emerstorfer, Kneifel and Hein, “The role of plant-based antimicrobials in food and feed production with special regard to silage fermentation”, Die Bodenkultur—Journal for Land Management, Food and Environment (2009), vol. 60, issue 3 [0152] Jorgensen and Ferraro, “Antimicrobial susceptibility testing: general principles and contemporary practices”, Clinical Infectious Diseases 26, 973-980 (1998). [0153] White, et al. “Antimicrobial resistance: standardisation and harmonisation of laboratory methodologies for the detection and quantification of antimicrobial resistance” Rev. sci. tech. Off. int. Epiz. 20 (3), 849-858 (2001). [0154] Madigan et al. “Brock Biology of Microorganisms”, 10. Ausgabe (2003), insbesondere S. 138 [0155] Mohan, Arvind, et al. “Microbial community changes in hydraulic fracturing fluids and produced water from shale gas extraction.” Environmental science & technology 47.22 (2013): 13141-13150. [0156] Mohan, Arvind, et al. “The Functional Potential of Microbial Communities in Hydraulic Fracturing Source Water and Produced Water from Natural Gas Extraction Characterized by Metagenomic Sequencing.” PloS one 9.10 (2014): e107682. [0157] Ravot, Gilles, et al. “Haloanaerobium congolense sp. nov., an anaerobic, moderately halophilic, thiosulfate and sulfur reducing bacterium from an African oil field.” FEMS microbiology letters 147.1 (1997): 81-88. [0158] [Struchtemeyer 2012] Struchtemeyer, Christopher G., Michael D. Morrison, and Mostafa S. Elshahed. “A critical assessment of the efficacy of biocides used during the hydraulic fracturing process in shale natural gas wells.” International Biodeterioration & Biodegradation 71 (2012): 15-21. [0159] [Struchtemeyer 2012b] Struchtemeyer, Christopher G., and Mostafa S. Elshahed. “Bacterial communities associated with hydraulic fracturing fluids in thermogenic natural gas wells in North Central Texas, USA.” FEMS microbiology ecology 81.1 (2012): 13-25. [0160] Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 23 (1993), S. 73-88. [0161] Wang, Jifu, et al. “Robust antimicrobial compounds and polymers derived from natural resin acids.” Chemical Communications 48.6 (2012): 916-918.