CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Provisional Application No. 63/033,555, filed June 2, 2020, U.S. Provisional Application No. 63/033,558, filed June 2, 2020, U.S. Provisional Application No. 63/067,703, filed August 19, 2020, U.S. Provisional Application No. 63/067,706, filed August 19, 2020, U.S. Provisional Application No. 63/067,715, filed August 19, 2020, U.S. Provisional Application No. 63/067,718, filed August 19, 2020, U.S. Provisional Application No. 63/067,719, filed August 19, 2020, and U.S. Provisional Application No. 63/067,729, filed August 19, 2020, the entire contents of each of which are incorporated herein by reference.

Field of the Invention

This invention is in the field of methods to reduce deposition of solid sulfur in natural gas wells.

Background of the Invention

Helium is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements.

Helium is critically important for specialized uses in industrial, scientific and medical processes and procedures. Liquid helium is used in cryogenics (its largest single use, absorbing about a quarter of production), particularly in the cooling of superconducting magnets, with the main commercial application being in MRI scanners. Helium's other industrial uses — as a pressurizing and purge gas, as a cooling gas used in the manufacture of optical fibers, as a protective atmosphere for arc welding and in processes such as growing crystals to make silicon wafers, account for approximately half of the gas produced. A well-known but minor use is as a lifting gas in balloons and airships.

From the beginning of recovery of helium from underground sources, all commercial helium is recovered from natural gas fields. The range of Helium found in natural gas fields is anywhere from a barely detectable level of about 0.1% to a level of about 10 % of natural gas in some fields. A helium content of about 0.3 % or more is considered necessary for commercial helium extraction.

In a typical natural gas well, there are multiple types of gasses present, such as, but not limited to carbon dioxide (CO2), methane (CH4), nitrogen (N2), hydrogen sulfide (H2S), sulfur (Ss) and Helium (He).

If there is a significant amount of butane, ethane, pentane, liquid petroleum/gasoline or other higher hydrocarbons then the gas is termed 'wet'. These are NGLs or condensates.

Wet gas is above 1050 BTUs with anything over 1350 being termed as 'super rich'. Wet gas has higher levels of natural gas liquids (NGLs) and condensates. In the oil and gas industry, wet gas is often used to describe the raw unprocessed gas, but some gas is 'wetter' than others.

From the standpoint of BTUs, dry gas is below 1050. When there is a high level of methane, the gas is considered dry, even if it has just been extracted from the well. Many conventional wells naturally produce dry gas that needs little processing. When we refer to dry gas, we mainly mean methane, which is used to heat homes, cook, and power some vehicles.

The gases in a natural gas well travel upwards from the reservoir to the surface through a series of connected pipes commonly referred to as the “tubing string”. As the gas rises from the reservoir and travels towards the surface through the tubing string it is a common occurrence that at the point along the wellbore where the temperature and pressure drop in the tubing string, gaseous sulfur (Ss(g>) begins to precipitate out into solid octasulfur (Ss( _s) ). This octasulfur then attaches itself to the inner surface of the pipe and is visible as a yellow solid. Eventually the yellow solid builds up on the pipe surface to a point where the flow of gas through the pipe is impeded causing the production of gas at the well to decrease. With a decrease in gas production comes a decrease in helium production and many times helium is the most valuable gas recovered from the well.

The problem of deposition of solid sulfur on the surfaces of pipes used to harvest natural gas is well known in the industry.

UK Patent Application No. 2411681A, “Method of Reducing Deposition of Elemental Sulfur in a Gas Well”, published on September 7, 2005.

This patent application describes and claims a method of reducing elemental sulfur deposition in a gas well involves injecting an aqueous solution of a surfactant having a hydrophile-lipophile balance value of at least 8 into the gas well upstream of a location where elemental sulfur precipitates from the produced natural gas. The concentration of the surfactant is such that the solution is above the critical micelle concentration for the aqueous surfactant solution under the thermodynamic conditions prevailing in the wellbore. At least a portion of the precipitated sulfur dissolves in the aqueous surfactant solution.

US Patent No. 3,331,657, “Method of Preventing the Depositing of Sulfur in the Riser Pipes in Producing Natural Gases Laden with Hydrogen Sulfide and Containing Elemental Sulfur Solution”, issued on July 18, 1967. This patent describes and claims in a method of preventing the formation of solid sulfur in a stream of natural gas during upward passage of the same from a subterranean natural gas deposit, said natural gas including H2S, CO2 and elementary sulfur and being initially at an elevated pressure and temperature sufficiently high to maintain said sulfur in solution in said H2S, the step of introducing into said stream of natural gas during upward passage of the same, at a point at which the pressure and temperature of said natural gas stream are still sufficiently high to maintain said sulfur in solution in said ¾S, an aqueous solution of the hydroxide of at least one substance selected from the group consisting of alkali metals and ammonia so as to form an aqueous solution of the sulfide of said substance having said sulfur dissolved therein in the form of an alkali metal or ammonium polysulfide.

US Patent No. 3393733, issued July 23, 1968 to Shell Oil Company and is entitled “Method of Producing Wells Without Plugging of Tubing String”. This patent claims a method of preventing hydrate formation and sulfur plugging in tubing string of a production well which extends from ground level to an underground producing zone for the production of a sulfur-containing fluid from said Zone, said method comprising:

(a) Flowing said sulfur-containing fluid from the producing Zone upwardly through said production tubing string; and,

(b) injecting into said production tubing string, through an injection tubing string in communication with said production tubing string, at a point where sulfur and hydrate deposition in the tubing string tend to form due to temperature and pressure drop in the tubing string, a hot sulfur-free fluid miscible with sulfur, said fluid being at a temperature above about 100 °F (37.7°C) and at a pressure sufficient to prevent sulfur precipitation and solidification on the tubing string wall.

US Patent No. 4, 543, 193, “Process for Preventing the Precipitation of Elementary Sulphur in Riser Pipes of Probes for Natural Gas”, issued on September 24, 1983. This patent describes and claims a process for preventing the precipitation of elementary sulfur from natural gas which may contain hydrogen sulfide and/or carbonic acid together with elementary sulfur during the mining of the gas which comprises dissolving the sulfur in a solvent which is selected from the group consisting of esters of mono- or poly-unsaturated fatty acids; thioethers of said esters or mono- or poly-unsaturated fatty acids; the mixed reaction products of hydrogen sulfide and said esters or mono- or poly-unsaturated fatty acids in the presence of elementary sulfur; and mixtures thereof, said solvent being optionally used in form of a solution wherein said solvent contains 10 to 24 carbon atoms in the fatty acid component and 1 to 22 carbon atoms in the alcohol component.

US Patent No. 10,472,556 “Nano-inhibitors”, issued on November 12, 2019. This patent describes and claims novel hybrid nanoparticles, useful for inhibiting or slowing down the formation of sulfur deposits or minerals in a well during the extraction of gas or oil. Specifically, the nanoparticles each include (i) a polyorganosiloxane (POS) matrix; and, optionally as a coating over a lanthanide oxide core, (iii) at least one polymeric scale inhibitor during the extraction of gas or oil. The invention also relates to the method for obtaining the nano-inhibitors and the application of same.

Previous attempts to reduce deposited octasulfur include trying to pump solvents into the production well. These attempts have not been successful. It has been found that as the solvents are introduced to the wellbore, they evaporate into the gas stream before coming into contact with the sulfur precipitation area.

What is needed are methods to reduce the deposition of solid sulfur on the inner walls of the pipes used to harvest natural gas containing helium and other valuable gasses.

Summary of the Invention

The first aspect of the instant claimed invention is a method to reduce the deposition of solid sulfur (Ss(s)) in a natural gas producing well, the method comprising the steps of a) Operating a natural gas production field comprising one or more natural gas production wells with each well containing a tubing string of connected pipes that allow gas to travel from a reservoir to the surface, b) Introducing nonpolar natural nanoparticles into the tubing string, c) Contacting the nonpolar natural nanoparticles with the gaseous sulfur (Ss(g)) present in the gas resulting in an interaction that causes the reduction of the deposition of solid sulfur (Ss(s)), wherein said nonpolar natural nanoparticles are selected from the group consisting of clays, quartz, feldspar, gypsum, coal dust, asphaltenes, biochar, ash, and fly ash, wherein said nonpolar natural nanoparticles can be introduced into the tubing string either by direct addition of a dry nanoparticle or be first being dispersed within a carrier fluid and then introducing the carrier fluid containing the dry nonpolar natural nanoparticles into the tubing string.

The second aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is a clay.

The third aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is a quartz.

The fourth aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is a feldspar.

The fifth aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is a gypsum.

The sixth aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is coal dust.

The seventh aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is an asphaltene.

The eighth aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is a biochar.

The ninth aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is an ash. The tenth aspect of the instant claimed invention is the method of the first aspect of the instant claimed invention in which said nonpolar natural nanoparticle is fly ash.

Detailed Description of the Invention

Current methods for recovering Helium from natural gas are described in this review article, “A Review of Conventional and Emerging Process Technologies for the Recovery of Helium from Natural Gas”, by Rufford, Chan, Huag and May, Adsorption Science and Technology, 2014, vol 31, pages 49-72. It is believed that the instant claimed invention will work in all three of the known recovery methods for extracting Helium: cryogenic distillation followed by pressure-swing adsorption, adsorption by itself and membrane technology.

As used herein, the term “nanoparticle” means a particle from about 1 to about 100 nanometers in diameter. In some embodiments, the term “nanoparticle” means a cluster of atoms or molecules with a radius of less than 100 nanometers. In some embodiments, the term nanoparticle is applied to inorganic materials, for example, silica. As used herein, the term “silica” may refer to silica particles or a silica dispersion. As used herein, the term “silica” may refer to silica particles originating from colloidal silica or from fumed silica. As used herein, the term “nanoparticles” can refer to both multiple individual nanoparticles as well as a population of nanoparticles of a particular type. Nanoparticles can also be referred to nanometer- sized particles, and nano powders are agglomerates of nanoparticles. In some embodiments, the term “nanofluid” means a base fluid, for example, water or oil, that comprises nanoparticles, including fluids with some or all of the nanoparticles in suspension.

Here are the definitions of the nonpolar natural nanoparticles that can be used in the method of the instant claimed invention:

Clay is a type of fine-grained natural soil material that contains hydrous aluminum phyllosilicates (clay minerals) that develop plasticity when wet. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to particle size and geometry as well as water content, and become hard, brittle and non-plastic upon drying or firing. Depending on the soil's content in which it is found, clay can appear in various colors from white to dull grey or brown to deep orange-red.

Base material nanoclays include but are not limited to Montmorillonite, Hectorite, Saponite, and Vermiculite. It is known that certain natural nanoclays are naturally polar. For use in the instant claimed invention, it is possible to apply a surface treatment to the naturally polar nanoclay to change it to be non-polar. These surface treatments are known to people of ordinary skill in the art of nanoparticles. The surface treatments include, but are not limited to Ammonium surfactants such as Quaternary Ammonium Dimethyl Benzyl Hydrogenated Tallow, Quaternary Ammonium Dimethyl Dihydrogenated Tallow, Quaternary Ammonium Dimethyl 2-Ethyl Hexyl Dihydrogenated Tallow, Methyl Tallow bis-2-hydroxyethyl Quaternary Ammonium, Octadecyl trimethyl Ammonium. Polyether functional quaternary amines are also included such as Polyoxypropylene methyl diethyl Ammonium materials. Suitable counter ions for Ammonium functional materials include Lithium, Sodium, Potassium, Magnesium, and Calcium. Amine functional materials are also used such as, primary amines like Octadecylamine, secondary amines, and tertiary amines such as Stearyl Diethoxyamine.

Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The atoms are linked in a continuous framework of SiCL silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiCh. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.

Feldspars (KAlShOx - NaAlSLOx - CaAESEOx) are a group of rock forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaS0 ₄ -2H ₂ 0. It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall

Coal dust is a fine powdered form of coal, which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. It is a form of fugitive dust.

Asphaltenes are molecular substances that are found in crude oil, along with resins, aromatic hydrocarbons, and saturates (i.e. saturated hydrocarbons such as alkanes). The word "asphaltene" was coined by Boussingault in 1837 when he noticed that the distillation residue of some bitumens had asphalt-like properties. Asphaltenes in the form of asphalt or bitumen products from oil refineries are used as paving materials on roads, shingles for roofs, and waterproof coatings on building foundations. Biochar is charcoal used as a soil amendment for both carbon sequestration and soil health benefits. Biochar is a stable solid, rich in carbon, and can endure in soil for thousands of years. Like most charcoal, biochar is made from biomass via pyrolysis. Biochar is under investigation as a viable approach for carbon sequestration, as it has the potential to help mitigate global warming and climate change. It results from processes related to pyrogenic carbon capture and storage (PyCCS).

Ash or ashes are the solid remains of fires. Specifically, it refers to all non-aqueous, non- gaseous residues that remain after something is burned. In analytical chemistry, in order to analyse the mineral and metal content of chemical samples, ash is the non-gaseous, non liquid residue after a complete combustion.

Fly ash or flue ash, also known as pulverised fuel ash in the United Kingdom, is a coal combustion product that is composed of the particulates (fine particles of burned fuel) that are driven out of coal-fired boilers together with the flue gases. Ash that falls to the bottom of the boiler's combustion chamber (commonly called a firebox) is called bottom ash. In modern coal- fired power plants, fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys. Together with bottom ash removed from the bottom of the boiler, it is known as coal ash.

These nonpolar natural nanoparticles are all commercially available.

As is mentioned previously, it is known that certain natural nanoparticles are naturally polar. For use in the instant claimed invention, it is possible to apply a surface treatment to the naturally polar nanoparticle to change it to be non-polar. These surface treatments are known to people of ordinary skill in the art of nanoparticles. The surface treatments include, but are not limited to, Ammonium surfactants such as Quaternary Ammonium Dimethyl Benzyl Hydrogenated Tallow, Quaternary Ammonium Dimethyl Dihydrogenated Tallow, Quaternary Ammonium Dimethyl 2-Ethyl Hexyl Dihydrogenated Tallow, Methyl Tallow bis-2-hydroxyethyl Quaternary Ammonium, Octadecyl trimethyl Ammonium. Polyether functional quaternary amines are also included such as Polyoxypropylene methyl diethyl Ammonium materials. Suitable counter ions for Ammonium functional materials include Lithium, Sodium, Potassium, Magnesium, and Calcium. Amine functional materials are also used such as, primary amines like Octadecylamine, secondary amines, and tertiary amines such as Stearyl Diethoxy amine. The nonpolar natural nanoparticles may be added to the tube string either dry or mixed in with a carrier fluid. When a carrier fluid is used to add the nonpolar natural nanoparticles the carrier fluid may be liquid or gaseous.

When the carrier fluid is liquid the liquid may be aqueous or non-aqueous.

When the carrier fluid is gaseous the gas may be any gas that does not cause problematic reactions. In an embodiment the gas is selected from the group consisting of natural gas, liquefied natural gas (LNG), methane (CH ₄ ), nitrogen (N ₂ ), Helium (He) and mixtures thereof.

In an embodiment the gas is selected from the group consisting of carbon dioxide (CO ₂ ) and mixtures with other gases.

Examples

Example 1 (comparative example)

Solid sulfur is put into a clear glass vessel. Elevated temperatures are applied until the solid sulfur melts into a liquid at approximately 239.38°F (115.21°C). The temperature is gradually reduced until solid octasulfur deposits on the walls of the vessel. When the experiment is ended and the gas evacuated, the octasulfur deposit remains on the walls and cannot be removed by tapping or shaking the vessel.

Example 2

Example 1 is repeated but in this example, toluene, a carrier fluid, containing a natural nanoclay that has been surface-treated to be nonpolar, is put in the vessel before (2a), during (2b) and after (2c) the solid sulfur is added and melted into liquid sulfur in the vessel at a temperature of about 116°C. Then the temperature is gradually reduced.

In each of experiments 2a, 2b and 2c, with the reduction in temperature, octasulfur is not observed to deposit on the walls of the glass. When each of experiments 2a, 2b and 2c are ended and the contents of the vessel poured out, a small quantity of nanoclay enveloped solid sulfur is found and upon analysis the presence of solid sulfur in the center of the nanoparticle solid is confirmed.