WO2013007811A1

WO2013007811A1 - Method for mic control in oil field applications (oil and gas pipeline systems)

Info

Publication number: WO2013007811A1
Application number: PCT/EP2012/063762
Authority: WO
Inventors: Kevin Janak; Michael Leonid Ludensky
Original assignee: Lonza AG; Lonza LLC
Current assignee: Lonza AG; Lonza LLC
Priority date: 2011-07-14
Filing date: 2012-07-13
Publication date: 2013-01-17
Anticipated expiration: 2014-01-14

Abstract

The invention relates to the prevention and removal of biofilm growth and microbially induced corrosion in gas and/or liquid streams in industrial process systems, such as oil and gas production and gathering systems. The method comprises the addition of one or more quaternary ammonium compounds, specifically quaternary ammonium carbonates, bicarbonates, chlorides, and mixtures thereof, such that the treatment regime involves an initial batch treatment at micelle forming concentrations of the aforementioned mixtures that are followed with batch or continuous treatment of the same compounds or alternate biocides.

Description

METHOD FOR MIC CONTROL IN OIL FIELD APPLICATIONS (OIL AND GAS

PIPELINE SYSTEMS)

Background of the Invention

Microbio logically Influenced Corrosion (MIC) is a significant problem within the oil and gas industry. It is estimated that as many as 20 to 30% of pipeline corrosion failures may be attributed to MIC. MIC is usually defined as a specific type of corrosion influenced by the presence or activities of microorganisms including bacteria and fungi. The primary pathway by which MIC occurs is via development of a community of microorganisms on a surface such as a pipe within an organic matrix commonly referred to as bio film.

Bio film consists of cells immobilized in a substratum, frequently embedded in an organic polymer matrix of microbial origin, which can restrict the diffusion of substances and bind antimicrobials. It is estimated that more than 99% of all the planet's bacteria live in biofilm commu- nities. In flowing aquatic environments, a biofilm consists of a sticky and absorptive polysaccharide matrix encompassing microorganisms. Biofilm bacteria are morphologically and metabolically distinct from free-floating bacteria. Their structural organization is a characteristic feature and distinguishes biofilm cultures from conventional planktonic organisms.

Biofilm, or sessile, bacteria can proliferate and form multi-layer colonies on pipes under natural deposits such as mineral scale, wax, or asphaltene. It is important to note that microorganisms located at the metal surface do not directly attack the metal or cause a unique form of corrosion. Instead, byproducts associated with an organism's metabolic activity promote known forms of corrosion, including pitting, crevice and under-deposit corrosion. Typically, the products of a growing microbiological colony accelerate the corrosion process by either preventing natural film-forming characteristics of metallic corrosion products that would otherwise rede- posit and inhibit further corrosion, or providing an additional reduction reaction that accelerates the corrosion process.

One of the most important strategies in mitigating MIC is removal of biofilm or prevention of biofilm formation. However, control of biofilms and sessile bacteria is much more difficult to achieve than control of planktonic cells, primarily due to presence of the exogenous polymeric matrix. This is due, in part, to the dynamic nature of biofilms, whereby biofilms continuously change in thickness, surface distribution, microbial populations and chemical composition, and respond to changes in environmental factors such as water temperature, water chemistry and surface conditions. Thus, the complexity of biofilms reduces the effectiveness of typical chemical treatment and removal strategies.

This reduced efficacy is evidenced by the typically much higher concentrations of chemical biocides required for biofilm removal and control relative to control of planktonic organisms. This can increase both the cost of treatment and may also add an additional concern of corrosion due to extraordinarily high concentrations of corrosive chemical biocides. Correspondingly, there exists a need for a novel treatment whereby bio film formation can be prevented or minimized with reduced chemical loadings within an industrial system, such as oil and gas systems, and that does not exhibit corrosivity to the system in question.

Description of the Prior Art

In this regard, several biocides are used for MIC control in oil field gathering lines. Commonly used biocides are non-oxidizing chemicals such as glutaraldehyde or bis[tetrakis- (hydroxymethyl)phosphonium] sulfate (THPS). Some concern has arisen that that these biocides may be inherently corrosive at high end use concentrations and could cause general corrosion in the assets they are protecting from MIC.

Another group of biocides used in industry are quaternary amines. However, quaternary amines used alone at reasonable and affordable treatment concentrations are generally not as effective as biocides in controlling microorganisms attached to metal surfaces and bulk fluids.

The use of quaternary amines and other film-forming inhibitors as corrosion inhibitors is known in the industry. One of the studies demonstrated that quaternary amines may prevent MIC by mechanisms other than killing bacteria by deterring microbial attachment to metal surfaces under conditions found in oil and gas production. This study (M.V. Enzien, D.H. Pope, M.M. Wu, and J. Frank "Non-biocidal control of microbio logically influenced corrosion using organic film-forming inhibitors", Corrosion 1996, Paper 96290) indicated that coupons continuously exposed to a quaternary amine had very low surface colonization and lower corrosion rates than did control coupons. Coupons dipped in quaternary amine and then exposed to control fluids also showed lower colonization and corrosion rates than did control coupons. However, this approach only prevented microbial attachment for a limited period of time, after which colonization of the metal surfaces re-occurred.

In addition, U.S. Pat. No. 5,026,491 teaches a method whereby a biocide is dosed as a concentrated slug in order to affect quick kill of microorganisms and is followed by a low level continuous dose of another biocide, specifically isothiazolone. Although biofilm control is ob- served, the patent does not indicate the formation of a biocidal surface during treatment. Further, it is well-known that mole ratios >2: 1 for levels of ¾S: isothiazolone can deactivate the isothiazolone, thereby reducing its effectiveness in oil & gas production systems (Williams, T.M. "Efficacy of Isothiazolone Biocide Versus Sulfate Reducing Bacteria" Corrosion 2009, Paper No. 09059).

This is further evidenced in the teaching from EP 0 706 974, whereby continuous addition of a biocide, specifically isothiazolone, did not result in extended microbial efficacy. Rather, an intermittent treatment of a batch biocide and biostat at short, frequent intervals ("pulse method") was claimed to maintain microbial control over an extended period of time. Importantly, the patent only teaches a method by which to reduce the amount of bio film within a system but not to prevent its initial growth and maintain a clean system. Further, no indication of the impact on MIC is discussed. Summary of the Invention

The present invention is directed to a method of prevention and eradication of biofilm growth in oil field water-based applications and thus controlling MIC, specifically pitting corrosion, in oil and gas pipelines. The method comprises adding one or more quaternary ammo- nium compounds, specifically, quaternary ammonium carbonates, bicarbonates, mixtures thereof, and chlorides. The treatment regime comprises of initial batch treatment at "micelle- forming" concentrations of above-mentioned compounds that may follow with batch or continuous treatment of same compounds or standard biocides. Unless otherwise specified, all concentrations are given in parts per million (ppm) by weight and refer to the active ingredient (a. i.). The initial batch concentration of the quaternary ammonium compounds maintained in the aqueous medium generally ranges from about 100 ppm to about 6,500 ppm (expressed as active ingredient) for biofilm inhibition. The follow-up concentration of the same compounds or standard biocides generally ranges from about 10 ppm to about 2,500 ppm (as a. i.).

The present invention has application to essentially all oil field aqueous systems having the potential to contain or grow biofilm, and initiate MIC. These may be oil industry systems, oil and gas gathering systems, oil and gas pipelines, etc., and any other system subject to the growth of biofilm. The biofilm may comprise different forms and species of microorganisms, e. g., adhered to surfaces, such as mats, floes and slime. Brief Description of the Figures

Figures 1-3 illustrate the effect of major biocides on sessile acid producing bacteria (APB) and sulfate reducing bacteria (SRB) under various treatment regimes. Figure 4 comprises SEM micrographs of metal coupons SEM showing the effect of tested biocides and treatment regimes.

Figure 5 illustrates the history of pipeline failures in the field case. Detailed Description of the Invention

The extent and nature of MIC vary with the context of the problem. The diverse nature of physico-chemical conditions in oil field applications, as well as diverse microbiology and en- vironments in which bio films grow call for a variety of tactics and strategies for MIC control that might include corrosion inhibitors, microbiological control, biofilm control and prevention, pipe cleaning, pigging, and mixture thereof. Recent papers demonstrated an importance of biofilm formation in the process of MIC development and formation of pitting corrosion in pipelines. ("Analysis of bacterial kill versus corrosion from use of common oilfield biocides" Vic Keasler, Brian Bennett, Heather McGinley, IPC 2010-31593; "Conventional application of biocides may lead to bacterial cell injury rather than bacterial kill within a biofilm" Scott Campbell, Andrew Duggleby, Angela Johnson, NACE 2011, paper 11234). The last paper reports the efficacy of biocides applied in a dynamic flow cell system evaluating current conventional treatment regimes decreasing viable bacterial numbers within a biofilm, and thus decreasing SRB activity. The data suggests that biocides may not be killing bacteria within a biofilm, and after further review of doubling times of SRB's within the bacterial biofilm, suggests that bacterial cell injury may be a possible explanation rather than bacterial cell kill. Therefore, controlling MIC by applying biocides to simply kill bacteria may not be effective.

The present invention suggests a novel approach - control of MIC via prevention of biofilm and pitting corrosion -, which comprises adding at least one quaternary ammonium com- pound, specifically, at least one quaternary ammonium compound according to the formula

(R'R R ),, X" (I),

where R¹ through R⁴ are independently selected from the group consisting of Ci_₂o aliphatic hydrocarbyl groups and C₇_n aromatic hydrocarbyl groups, and X"^~ is a counter-anion selected from the group consisting of carbonate, bicarbonate, halides, phosphates, ethosulfates, citrates, borates, nitrate, and Ci_₂o carboxylates. Especially preferred counter-anions X" are carbonate, bicarbonate, and mixtures thereof.

In a preferred embodiment the treatment regime consists of an initial batch treatment at or above a specific critical micelle concentration of the at least one quaternary ammonium com- pound of formula I, optionally followed by a batchwise or continuous treatment with the same quaternary ammonium compound(s) or standard biocides, either below, at, or above said critical micelle concentration.

In a more preferred embodiment the initial batch treatment is performed at a concen- tration of the at least one quaternary ammonium compound maintained in the aqueous medium in the range of from about 100 ppm to about 6,500 ppm, more preferably from about 250 ppm to about 4,500 ppm, most preferably from about 500 ppm to about 2,500 ppm. In another preferred embodiment the follow-up treatment is performed batchwise with one or more quaternary ammonium compounds of formula I, at a concentration in the range of from about 100 ppm to about 2,500 ppm, more preferably from about 200 ppm to about 2,000 ppm, most preferably from about 250 ppm to about 1,000 ppm.

In still another preferred embodiment the follow-up treatment is performed continuously with one or more quaternary ammonium compounds of formula I, at a concentration in the range of from about 10 ppm to about 200 ppm. In another preferred embodiment the follow-up treatment is performed batchwise with glutaraldehyde at a concentration in the range of from about 250 ppm to about 750 ppm.

In another preferred embodiment the follow-up treatment is performed batchwise with bis[tetrakis(hydroxymethyl)phosphonium] sulfate (THPS) at a concentration in the range of from about 50 ppm to about 350 ppm.

The method of the present invention is preferably applied to industrial systems comprising an aqueous medium in oil and gas production sites or plants. Particularly preferred are industrial systems comprising an aqueous medium selected from the group consisting of hydro- test water, oil and gas gathering waters, condensed waters, oil and gas production waters, fracturing waters, wash waters, deck fluids, water in oil and gas reservoirs, water in sump tanks and water in drains.

The method the present invention is preferably applied to industrial systems comprising an aqueous medium wherein the aqueous medium contains biofilm adhering to a substrate.

In a preferred embodiment the at least one quaternary ammonium compound of formula I is added to the aqueous medium together with at least one performance additive. More preferably, the at least one performance additive is selected from the group consisting of dispersants, biodispersants, scale control agents, corrosion inhibitors, surfactants, hydrogen sulfide scavengers, oxygen scavengers, friction reducers, hydrate inhibitors, hydrotropes, biocides other than quaternary ammonium compounds of formula I, cleaning agents, and mixtures thereof.

Without wishing to be bound by any particular theory, it is believed that in aqueous solutions, the quaternary ammonium compounds used herein have a natural affinity to the metal, since they also act as cationic surfactants, and therefore migrate to the surface of the metal. Once at the surface, the quaternary ammonium compounds block oxygen and/or air from causing further oxidation of the metal surface. However, this is only part of the mechanism. The other significant property of the film created by the above mentioned treatment regime is the ability to prevent or minimize biofilm growth on the metal surface via incurred biocidal properties of such film. Figures 1-3 demonstrate that the treatment process according to the invention significantly delayed development of surface-bound sulfate reducing bacteria (SRB) and acid producing bacteria (APB) rather than general heterotrophic bacteria (GHB) that are located further from the surface. It is our understanding that this treatment technology is different from that described in the above mentioned Enzien et al. paper.

The following non-limiting Examples are intended to illustrate the present invention. Carboquat™ and Carboshield™ are trademarks of Lonza Inc., Allendale, NJ, for solutions containing didecyldimethylammonium carbonate and didecyldimethylammonium bicarbonate in a molar ratio of about 1 : 1.

EXAMPLE 1

Biofilm Control Efficacy

The efficacy of biocides and impact of pre-treatment on biofilms was tested utilizing dynamic flow cells attached to a chemostat. The dynamic flow cell, a flowing system, allows biocide testing to be performed in the laboratory under conditions representative of process equipment, pipelines or flowlines. The dynamic flow cells were operated under laminar flow conditions. Concentration, and treatment protocol (defined as continuous, batch, or pulse treatment for a prescribed length of time) can be changed to mimic the system under evaluation, thus providing the best opportunity to not only evaluate biocide efficacy, but to optimize biocide application, as well, prior to field testing, significantly decreasing the time necessary to achieve microbiological control in field systems.

Dynamic Flowcell w/Chemostat Operation

Within this set of experiments, dynamic flowcells were connected to a chemostat that can grow bugs at a set rate that will influence the inoculums within the system.

The following treatments were evaluated:

• Control (no treatment)

Glutaraldehyde— 250 ppm active

• THPS— 125 ppm active

· DDAC— 250 ppm active

DDABC— 250 ppm active

• DDABC— 1 ,250 ppm active pre-treatment + 500 ppm active batch treatment

• DDABC— 1,250 ppm active pre-treatment + 50 ppm active continuous treatment THPS = Tetrakis(hydroxymethyl)phosphonium sulfate (2: 1)

DDAC = Didecyldimethylammonium chloride

DDABC = Didecyldimethylammonium carbonate/bicarbonate Chemostat Setup and Operation

The chemostat, bioreactor, was operated utilizing artificial seawater spiked with approximately 6 M lactate. The chemostat was operated continuously for approximately three week to establish a healthy viable population of GHB, APB, and SRB bacteria within the bioreactor. After three weeks, the chemostat pumps and dosing peristaltic pumps were turned on to achieve a minor inoculum into the dynamic flowcell strings utilizing flow and dilution theory to achieve the minor inoculum. The dynamic flowcell strings were inoculated immediately upstream of the first dynamic flowcell of each string.

Upon setup of the 7 parallel dynamic flowcell strings, the peristaltic pumps were turned on and the system was inoculated.

Dynamic Flowcell Setup and Operation

Seven primary water reservoirs were setup to hold the water necessary to operate the dynamic flowcell system. Six of the seven reservoirs contained the respective concentration of chemical that was required for the test, and one reservoir was the control with no chemical addition. All seven of the reservoirs were connected to seven dynamic flowcell strings via a peristaltic pump, respectively. Seven strings with 7 dynamic flowcells connected in series, were set up in parallel to each other. The flowcell strings were connected to a peristaltic MasterFlex^® LS digital pump with respective pump heads for each dynamic flowcell string. The outlet tubing of the final dynamic flowcell was placed in a sink or collection vessel. Therefore, these reactors were not a recirculating loop, but rather a once flow through reactor system.

Batch Chemical Treatment

The biocides, glutaraldehyde, THPS, DDAC, and DDABC, were dosed into separate dynamic flowcell strings respectively with a comparative active concentration of each chemical and treatment regime. The treatment regime for the 4 chemicals was continued over the course of weeks to closely resemble field application of chemical treatments. The concentration treatment doses were established prior to start of the experiment. The dynamic flowcell (string 6) was soaked in an established Carboshield™ treatment concentration (1 ,250 ppm as active ingredient) for 24 h prior to beginning the inoculations. The flow rate through the dynamic flowcell system should be such to represent a laminar flow system. Pre-Treatment + Continuous Treatment

The dynamic flowcell (string 7) was soaked in an established Carboshield™ treatment concentration (1,250 ppm as active ingredient) for 24 h prior to beginning the inoculations. A 50 ppm dose (as active) was applied throughout the course of the study.

Enumeration of Surviving Sessile Bacteria

The biostud holder was removed from the dynamic flowcell and was replaced with a test blank. The biostud coupon was transferred into a test tube containing 10 ml sterile brine solution. The bio film was dispersed into suspension by mixing with a vortex mixer.

The results of the experiments are shown in Figures 1-3.

The results show that Carboquat™ pre-treatment + continuous treatment significantly delayed bio film growth for SRB and APB bacteria. The bio film was easier to remove on the coupons that received Carboquat™ pre-treatment.

EXAMPLE 2

Pitting Corrosion Inhibition The biostuds from Example 1 samples were placed in the scanning electron microscope.

Tweezers were used to handle the samples to insure that no finger prints were placed on the face of the sample. The samples were photographed at 50, 200 and 500^x in representative areas, usually 3 areas per sample. The samples were then photographed to get the overall image of the surface. Photographs are shown in Figure 4.

SEM images of carbon steel coupons following the 28 day testing were collected and analyzed at 50^x magnification utilizing the software imaging program Image J, available from the National Institutes of Health (http://imagej.nih.gov/ij). An average pit size in terms of depth, area, and volume were determined via computer image analysis and the values normalized relative to the control for the determination of the relative pitting tendency of each treatment program. Values <1 indicate a reduced pitting tendency whereas values >1 indicate an increased pitting tendency relative to the control. Results of SEM image analysis are shown in Table 1. Table 1 Effect of biocides and treatment regime on pitting corrosion.

THPS = Tetrakis(hydroxymethyl)phosphonium sulfate (2: 1)

DDAC = Didecyldimethylammonium chloride

DDABC = Didecyldimethylammonium carbonate/bicarbonate

EXAMPLE 3

Field Case Study

This example demonstrates MIC control efficacy of Carboquat formulation application in low velocity gas gathering pipelines, resulting in the reduction of the number of failures via suspected biocidal efficacy/bio film prevention while providing corrosion inhibition characteristics (Figure 5).

Field Evaluation Conditions.

The test location consisted of a traditional shallow gas and oil, low pressure (0.1 to 0.14 MPa [15-20 psi]) field with largely passive extraction. The field provides "sweet" gas and oil with almost no hydrogen sulfide concerns. The gas evolved is low in water content (<0.5%) and there is no need for secondary water injection methods. Water collection within the pipes typically has low total solids content, low to moderate salinity, and has long a residence time in the system (months) with laminar flow characteristics. The field consists of approximately 1,500 wellheads typically 700-900 m deep spread over an area of about 16^χ40 km² (10x25 miles) and is interconnected by an irregular spider web network of 7.5 cm (3") gathering pipes. Standard 7.5 cm (3") gathering lines connect to 15 cm (6") main trunk [gathering] lines and bring materials to centralized separation equipment for both gas/water (2 -phase) and gas/oil/water (3-phase) separation. The total gathering pipe length was estimated at 1,653 km. Internal leaks are typically seen at 4 and 8 o'clock on the pipe cross section at the water/gas interface. The test formulation of the present invention was applied quarterly via either pig slug injection or gravity feed slug injection at each wellhead. The target concentration was 1,250 ppm as active ingredient. The DDABC based product exited the process at the water separator in the water layer which was ultimately subjected to deep well disposal. Periodic monitoring of this water layer during the quarterly treatment program revealed the presence of DDABC at levels ranging from 200-800 ppm.

Claims

Claims:

1. A method of controlling microbio logically influenced corrosion (MIC) in industrial systems comprising an aqueous medium via prevention of bio film and pitting corrosion, which method comprises adding to said aqueous medium at least one quaternary ammonium compound of formula

( 'R^RV), X" (I), wherein R¹ through R⁴ are independently selected from the group consisting of Ci_₂o aliphatic hydrocarbyl groups and C₇_n aromatic hydrocarbyl groups, and X"^~ is a counter- anion selected from the group consisting of carbonate, bicarbonate, halides, phosphates, ethosulfates, citrates, borates, nitrate, Ci_₂o carboxylates, and mixtures thereof, wherein n designates the number of negative charges of the counter-anion.

2. The method of claim 1, wherein X"^~ is carbonate, bicarbonate, or a mixture thereof.

3. The method of claim 1 or 2, comprising an initial batch treatment at or above a specific critical micelle concentration of the at least one quaternary ammonium compound of formula 1 and, optionally, a subsequent batchwise or continuous follow-up treatment with the same quaternary ammonium compound(s) or standard biocides, either below, at, or above said critical micelle concentration.

4. The method of claim 3, wherein the initial batch treatment is performed at a concentration of the at least one quaternary ammonium compound maintained in the aqueous medium in the range of from 100 ppm to 6,500 ppm.

5. The method of claim 4, wherein the initial batch treatment is performed at a concentration of the at least one quaternary ammonium compound maintained in the aqueous medium in the range of from 250 ppm to 4,500 ppm.

6. The method of claim 5, wherein the initial batch treatment is performed at a concentration of the at least one quaternary ammonium compound maintained in the aqueous medium in the range of from 500 ppm to 2,500 ppm.

7. The method of any of claims 3 to 6, wherein the follow-up treatment is performed batch- wise with one or more quaternary ammonium compounds as defined in claim 1, at a concentration in the range of from 100 ppm to 2,500 ppm.

8. The method of claim 7, wherein the follow-up treatment is performed batchwise with one or more quaternary ammonium compounds as defined in claim 1 , at a concentration in the range of from 200 ppm to 2,000 ppm.

9. The method of claim 8, wherein the follow-up treatment is performed batchwise with one or more quaternary ammonium compounds as defined in claim 1 , at a concentration in the range of from 250 ppm to 1,000 ppm.

10. The method of any of claims 3 to 6, wherein the follow-up treatment is performed continuously with one or more quaternary ammonium compounds as defined in claim 1 , at a concentration in the range of from 10 ppm to 200 ppm.

11. The method of any of claims 3 to 6, wherein the follow-up treatment is performed batch- wise with glutaraldehyde at a concentration in the range of from 250 ppm to 750 ppm.

12. The method of any of claims 3 to 6, wherein the follow-up treatment is performed batch- wise with bis[tetrakis(hydroxymethyl)phosphonium] sulfate (THPS) at a concentration in the range of from 50 ppm to 350 ppm.

13. The method of any of claims 1 to 12, wherein the industrial system comprising an aqueous medium is in oil and gas production.

14. The method of claim 13, wherein the aqueous medium is selected from the group consisting of hydrotest water, oil and gas gathering waters, condensed waters, oil and gas production waters, fracturing waters, wash waters, deck fluids, water in oil and gas reservoirs, water in sump tanks and water in drains.

15. The method of any of claims 1 to 14, wherein the aqueous medium contains biofilm adhering to a substrate.

16. The method of any of claims 1 to 15, wherein the at least one quaternary ammonium compound is added to the aqueous medium together with at least one performance additive.

17. The method of claim 16, wherein the at least one performance additive is selected from the group consisting of dispersants, biodispersants, scale control agents, corrosion inhibitors, surfactants, hydrogen sulfide scavengers, oxygen scavengers, friction reducers, hydrate inhibitors, hydrotropes, biocides other than quaternary ammonium compounds of formula I, cleaning agents, and mixtures thereof.