WO2013169679A1

WO2013169679A1 - Methods for cleaning natural gas pipelines

Info

Publication number: WO2013169679A1
Application number: PCT/US2013/039794
Authority: WO
Inventors: Ronald Glynn FISHER; Karin S. FISHER; Jacques H. FISHER
Original assignee: M-I L.L.C.
Priority date: 2012-05-07
Filing date: 2013-05-07
Publication date: 2013-11-14

Abstract

A method includes introducing a cleaning fluid into a natural gas pipeline, the cleaning fluid including a diluent selected from glycol, glycerin, or mixtures thereof.

Description

METHODS FOR CLEANING NATURAL GAS PIPELINES

BACKGROUND

[0001] This section provides background information related to the present disclosure and is not necessarily prior art.

[0002] Pipelines are utilized to transport different types of substances such as water, chemicals, oil, gas, and gaseous fluids. During operation, the interior walls of a pipeline accumulate deposits of solids or become corroded due to the substances moving through them. As this process continues, the efficiency and integrity of the pipeline may be decreased. Therefore, operators periodically clean the pipeline to improve efficiency and prevent structural damage to the pipeline.

[0003] The cleaning of natural gas pipelines, in particular, pose some difficulty due to the prohibition of moisture, the presence of which may cause the formation of muds, rust, debris, and the like. Other issues with water in a natural gas line include the formation of hydrates and/or ice plugs and the freezing of valves and gates, which block flow through the pipelines.

[0004] Several methods, known in the art, are employed to clean a natural gas pipeline. Flow through a pipeline may be ceased to allow the pipeline to be cleaned with water. Another method includes maintaining service through the pipeline and cleaning the line utilizing a hydrocarbon diluent and cleaning agent. [0005] As previously mentioned, water used as the diluent for cleaning a natural gas pipeline can result in undesired hydrate formation, potentially causing obstruction or rupture of the pipeline. Further, using water to clean the line would require an additional process of dehydrating the line to bring the line's dew point back to an optimum range.

[0006] Utilizing typical hydrocarbons as the diluent in a chemical cleaning process may be an inefficient way to clean the pipe. Samples from a natural gas pipeline often comprise water-wet solids, which are insoluble in most hydrocarbons. Thus, the immiscibility of pipeline solids in typical hydrocarbons makes such hydrocarbons an ineffective solids carrier for the cleaning process.

[0007] Thus there exists a need for methods of cleaning a natural gas pipeline in an effective yet safe and economically feasible way.

SUMMARY

[0008] In one aspect of the present disclosure, a method includes introducing a cleaning fluid into a natural gas pipeline, the cleaning fluid including a diluent selected from glycol, glycerin, or mixtures thereof.

[0009] In another aspect of the present disclosure, a method includes introducing a cleaning agent into a natural gas pipeline and introducing a diluent into the natural gas pipeline, the diluent selected from glycol, glycerin, or mixtures thereof.

[0010] In yet another aspect of the present disclosure, a method includes cleaning a natural gas pipeline with a diluent comprising glycol. The method further includes admixing water to the glycol to separate solids from the glycol and recovering the glycol.

[0011] Furthermore, modifications are possible without materially departing from the teachings of the present disclosure. Accordingly, such modifications are intended to be included within the scope of the disclosure as defined in the claims.

DETAILED DESCRIPTION

[0012] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure.

[0013] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having," are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, components, and/or groups, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0014] Aspects of the present disclosure relate generally to a method of introducing a cleaning fluid into a natural gas pipeline using glycols as the diluent. Through non-limiting embodiments, the present disclosure relates to methods for cleaning, collecting, and removing particulate matter, solids, debris, and/or fluids from the interior wall of a natural gas pipeline using glycol as a diluent.

[0015] Within natural gas pipelines, the natural gas is typically purified to remove water and contaminants, such as hydrogen sulfide and carbon dioxide, before it is transported from its source. Substances, such as gaseous fluids, transported by natural gas pipelines are ideally free of water and toxic or corrosive contaminants. Residual water in the pipelines may facilitate the formation of hydrates (e.g., clathrate crystals) potentially causing flow reduction and/or pipe damage.

[0016] According to some embodiments, glycol or glycerin may be used as the diluent for cleaning a pipeline where water cannot be introduced to the line to avoid the formation of hydrates. In other embodiments, a diluent comprising glycol or glycerin may be used as a substitute for a typical hydrocarbon diluent to yield improvements in solids wettings and dispersion within a cleaning fluid.

[0017] As used herein, a diluent may refer to an inert medium, such as one that is non-reactive with or will not negatively impact the equilibrium or kinetics of a composition, mixture, or fluid system. A diluent can be used, for example, to modify the viscosity or increase the volume of a fluid system.

[0018] According to example embodiments, a cleaning fluid comprising a cleaning agent in a glycol may wet the solids within a pipeline, allowing such solids to be miscible in and removed by the cleaning fluid. If necessary, the solids may further be removed by mechanical cleaning devices, commonly referred to as pigs. As used herein, a pig is a mechanism, made from a varied range of materials, (e.g., metal, rubber, polyurethane) pushed through a pipeline for the purpose of cleaning and/or inspecting the interior surfaces. The elimination of solids and/or particulate matter within the internal surface of the pipeline may reduce the occurrence of trapped moisture and residual water. Thus, hydrate formation is potentially reduced, while the cleaning process is accelerated within a pipeline.

[0019] Suitable glycols in the present disclosure may include any member of a class of organic compounds in which two hydroxyl (OH) groups are attached to different carbon atoms in the hydrocarbon chain, having a general formula CnH_2n(OH)2, for example. In example embodiments, ethylene glycol, also called 1 ,2-ethanediol, having a molecular formula HOCH₂CH₂OH, can be used as a diluent in a cleaning fluid for natural gas pipelines. Due to its properties including the ability to wet solids, relatively high solubility, relatively high boiling point, affinity for water, and commercial availability, ethylene glycol can be effectively utilized as a diluent in a pipeline cleaning fluid. However, it is contemplated, in other example embodiments, that other glycols can be used including, but not limited to, monoethylene glycol, ethylene glycol, propylene glycol, di-ethylene glycol, polypropylene glycol, and tri-ethylene glycol, or mixtures thereof.

[0020] The current industry standard for cleaning fluids used in natural gas pipelines ranges from about 80% to about 90% by volume of a typical hydrocarbon diluent and from about 10% to about 20% by volume of a selected pipeline cleaning agent. The hydrocarbon diluent for the cleaners is typically either aliphatic solvents (e.g., diesel or kerosene) or aromatic solvents (e.g., xylene or toluene). These solvents have an affinity to absorb the glycols and dehydrate the solids in the lines.

[0021] In one embodiment of the present disclosure, the glycol to cleaning agent mixture ranges from about 50% to about 95% by volume glycol and from about 5% to about 50% by volume cleaning agent, depending on the amount of contamination in the line. In another embodiment, the glycol to cleaning agent mixture ranges from about 80% to about 95% by volume glycol and from about 5% to about 20% by volume cleaning agent. In yet another embodiment, the glycol to cleaning agent mixture ranges from about 90% to about 99% by volume glycol and from about 1 % to about 10% by volume cleaning agent. In yet another embodiment, 100% glycol is used to clean the pipeline, depending on the amount of contamination in the line.

[0022] In yet another embodiment, a cleaning fluid introduced to a natural gas pipeline may include glycerin, either alone in or combination with the cleaning agent. Glycerin, also referred to as glycerin, having a molecular formula C₃H₈O₃, may be a substitute for the glycol diluent as a component of the cleaning fluid. Both glycerin and glycol diluent, as discussed herein, may have cleaning properties comparable to that of water. Utilizing glycerin or glycol diluent will reduce the hydrate formation typically prevalent with the use of water for cleaning pipelines.

[0023] In one embodiment of the present disclosure, the glycerin to cleaning agent mixture ranges from about 50% to about 95% by volume glycerin and from about 5% to about 50% by volume cleaning agent, depending on the amount of contamination in the line. In another embodiment, the glycol to cleaning agent mixture ranges from about 80% to about 95% by volume glycerin and from about 5% to about 20% by volume cleaning agent. In yet another embodiment, the glycerin to cleaning agent mixture ranges from about 90% to about 99% by volume glycerin and from about 1 % to about 10% by volume cleaning agent. In yet another embodiment, 100% glycerin is used to clean the pipeline, depending on the amount of contamination in the line.

[0024] As a component of the disclosed cleaning fluid, the cleaning agent may be any suitable pipeline cleaning chemical, as known in the art. For example, a cleaning fluid may comprise a water soluble, non-hazardous blend of surfactants for solids wetting, dispersants, and solvents for solids penetrating and carrying. A non-limiting example of a suitable cleaning agent is available from M- I L.LC. under the name Aurora Clean 5325.

[0025] As discussed herein, the pipeline is cleaned using the cleaning fluid which includes a cleaning agent and/or diluent comprising glycol, glycerin, or a mixture of glycol and glycerin, using methods known by those skilled in the art. For example, a diluent selected from glycol, glycerin, or mixtures thereof, may be admixed with a cleaning agent prior to introducing the cleaning fluid into the natural gas pipeline. The cleaning fluid may be introduced into the pipeline by way of pumping or other conventional means of adding a fluid to a pipeline. In another embodiment, a cleaning agent may be introduced into a natural gas pipeline, followed by addition of the diluent into the natural gas pipeline. In example embodiments, following cleaning, subsequent pig runs may be performed to confirm that the line is satisfactorily cleaned.

EXAMPLES

[0026] Example 1

[0027] To a conventional pipeline was added 275 gallons of cleaning agent and 2376 gallons of diesel to clean the pipeline in numerous trial runs. A mechanical pig was pushed through the pipeline to recover from about 2033 gallons to about 3502 gallons, in a series of runs, of a slurry material comprising solids and particulate matter. The recovered slurry material was observed as comprising fluid and dense black sludge.

[0028] Example 2

[0029] To a conventional pipeline was added 275 gallons of cleaning agent and 2500 gallons of ethylene glycol, and in additional runs, 275 gallons of cleaning agent and 3100 gallons of ethylene glycol to clean the pipeline in numerous trial runs. The recovered slurry material was observed as fluid and black wet sludge.

[0030] Following introduction of the cleaning agent and/or glycol diluent, and after introduction of the pig, remaining glycol or glycerin diluent, cleaning agent, and/or pipeline solids may be captured in a frac tank. Such pipeline solids were dispersed throughout the glycol. About 20% by volume fresh water may be added and mixed to the frac tank utilizing a pump. The addition of water reduces the total density of the glycol mixture, enabling the solids to settle out of solution. The solids settle out of the glycol, falling into the lower levels of the frac tank to be disposed. The remaining glycol may be recovered via centrifugation to remove excess solids or particulate matter. It is further contemplated that various technologies known in the art, such as filtration, for example, may be used to perform the separation of glycol, or diluent generally, from the particulate matter. [0031] Embodiments of the present disclosure may provide for methods of cleaning a natural gas pipeline using a cleaning fluid composed of a diluent selected form glycol, glycerin, or mixtures thereof, to impart the typical cleaning properties of water. However, the presence of glycol or glycerin as a component of the cleaning fluid, in place of water, may provide efficient pipeline cleaning while potentially reducing the formation of hydrates within the interior surface of the pipelines.

[0001] The foregoing description of the embodiments has been provided for purposes of illustration and description. Although the preceding description has been described herein with reference to particular means, materials, and embodiments, it is not intended to be limited to the particulars disclosed herein; rather, it extends to all functionally equivalent structures, methods, and uses, such as are within the scope of the appended claims.

Claims

CLAIMS What is claimed is:

1 . A method comprising:

introducing a cleaning fluid into a natural gas pipeline, wherein the cleaning fluid comprises a diluent selected from glycol, glycerin, or mixtures thereof.

2. The method of claim 1 , wherein the cleaning fluid further comprises:

a cleaning agent in an amount from about 5% to about 50% by volume, wherein the diluent is in an amount from about 50% to about 95% by volume.

3. The method of claim 1 , wherein the cleaning fluid further comprises:

a cleaning agent in an amount from about 5% to about 20% by volume, wherein the diluent is in an amount from about 80% to about 95% by volume.

4. The method of claim 1 , wherein the cleaning fluid further comprises:

a cleaning agent in an amount from about 1 % to about 10% by volume, wherein the diluent is in an amount from about 90% to about 99% by volume.

5. The method of claim 1 , wherein the glycol is selected from at least monoethylene glycol, ethylene glycol, propylene glycol, di-ethylene glycol, polypropylene glycol, and tri-ethylene glycol, or mixtures thereof.

6. The method of claim 1 , further comprising:

admixing a cleaning agent with the diluent prior to introducing the cleaning fluid into the natural gas pipeline.

7. A method comprising:

introducing a cleaning agent into a natural gas pipeline; and

introducing a diluent into the natural gas pipeline, wherein the diluent is selected from glycol, glycerin, or mixtures thereof.

8. The method of claim 6, wherein the glycol is selected from at least monoethylene glycol, ethylene glycol, propylene glycol, di-ethylene glycol, polypropylene glycol, and tri-ethylene glycol, or mixtures thereof.

9. A method comprising:

cleaning a natural gas pipeline with a diluent comprising glycol;

admixing water to the glycol to separate solids from the glycol; and recovering the glycol.

10. The method of claim 9 further comprising:

separating the solid from the glycol by centrifugation.

1 1 . The method of claim 9, wherein the water is admixed with used glycol after cleaning the natural gas pipeline.

12. The method of claim 9, wherein the glycol is selected from at least monoethylene glycol, ethylene glycol, propylene glycol, di-ethylene glycol, polypropylene glycol, and tri-ethylene glycol, or mixtures thereof.