METHOD AND PILL FOR REMEDIATING HYDRATE CONDENSATE

BLOCKAGE IN PIPELINES

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application, pursuant to 35 U.S.C. § 1 19(e), claims priority to U.S. Patent

Application Serial Nos. 60/885,914, filed on January 21, 2007, and 60/894,363, filed on March 12, 2007, both of which are herein incorporated by reference in their entirety.

BACKGROUND OF INVENTION

Field of the Invention

[0002] Embodiments disclosed herein relate generally to push pills for use in remediating hydrate condensate blockage in pipelines.

Background

[0003] Low-molecular-weight hydrocarbons, such as methane, ethane, propane, butane and iso-butane, and sometimes other low-molecular-weight species such as CO ₂ and H ₂ S, are normally present in pipelines or other conduits used in the transportation and processing of natural gas and crude oil. When a gas stream is subjected to low temperatures and/or elevated pressures in the presence of free water, gas hydrate crystals typically are formed. Particularly, if a program of injection of low-dosage-hydrate-inhibitors (LDHFs) is on-going and some up-set occurs in the gas gathering center or centers supplying gas to the pipeline, in the operation of the pipeline itself, or in the gas treating plant that the pipeline is flowing into, then there can be an interruption in the in-flows and continuous injection of LDHI's. In these circumstances a hydrate blockage or partial blockage can condense in the pipeline that can only be remediated through the application of thermodynamic hydrate inhibitors which will contact the hydrate condensate directly, melt or extract water therefrom, and thereby remove the blockage from the pipeline.

[0004] Gas hydrates are clathrates (inclusion compounds) in which small hydrocarbon molecules are trapped in a lattice consisting of water molecules. Hydrates form as a consequence of the tendency of water to reorient in the presence of a non-polar solute (typically light hydrocarbon gases such as methane) to stabilize the lattice through, typically, van der Waals interactions while maintaining the

hydrogen bonding between the water molecules. Tetrahydrofuran, jy-dioxane, CO ₂ , and H ₂ S, to name a few other compounds in addition to the low-molecular- weight hydrocarbons are capable of occupying the interior positions in a clathrate lattice of water molecules and stabilizing the overall structure so that it does not decompose until a relatively substantial increase in temperature or decrease in pressure occurs or both occur. Tetra-hydrofuran and />-dioxane, of course, are not commonly found in pipelines; but CO ₂ , H ₂ S, and low-molecular-weight hydrocarbons are.

[0005] Hydrate formation inside a conduit such as a pipeline is undesirable because the crystals might cause plugging of flow lines, valves and instrumentation, reducing line capacity and/or causing physical damage to pipelines and equipment. Unless the gas hydrate plug is only partially plugging the pipe, such gas hydrate plugs tend to separate a pipe into two zones: a high pressure zone between the head well and the plug and a low pressure zone between the plug and the production facilities area. If the plug and the pipe wall are suddenly unstuck, a projectile may be generated which can destroy the pipeline at any restriction or facilities apparatus. The solution is to decrease the pressure both on the well head side and on the platform side, but there is still a potential risk for generation of a projectile.

[0006] In order to remedy this undesired phenomenon, a number of means for inhibiting gas hydrate formation have been proposed, such as removal of free water, addition of salts or brines, maintaining elevated temperatures and/or reduced pressures, and/or the addition of inhibiting agents such as melting point depressants (antifreezes). Melting point depressants, typical examples of which include methanol and various glycols, often have to be added in substantial amounts, typically in the order of several tens of percent by weight of the water present, in order to be effective. However, these methods focus on the prevention of gas hydrate crystallization through thermodynamic means. The addition of salts or brines is also classed among the thermodynamic methods for prevention of gas hydrate crystallization. There is also a large class of kinetic hydrate inhibitors which inhibit the kinetics of the formation of hydrates and hydrate crystal growth modifiers which permit the hydrates to form but prevent them from agglomerating into a plug as long as there is flow in the pipeline to fluidize the tiny crystals that do form and allow them to be transported along and out of the pipeline into a receiving facility where they can

be dealt with without causing any interruption in pipeline flow. When flow in the pipeline is interrupted for some reason while there is still a substantial burden of tiny hydrate crystals residing in the pipeline, then these crystals can drop into lower portions of the pipeline and lie together in intimate physical contact for sufficient time for the crystal growth inhibition to fail and a hydrate plug can form.

[0007] In the event that a hydrate plug is formed in a pipeline completely plugging the pipeline, removal of the plug becomes necessary in order to resume gas flow. If the pipeline is only partially plugged, it may be acceptable to re-start the pipeline in the partially plugged condition; however, usually, it is greatly preferred to remove even a partial plug in order to resume full gas flow as the pipeline was designed. Prior art methods for remediation of the pipeline have included the injection of copious quantities of methanol or ethylene glycol down the line to help melt the hydrate plug and to dilute the melt water so that the hydrates do not re-form as the pipeline is pressured up during blow-down procedures to remove the plug.

[0008] However, the volume of methanol or ethylene glycol needed to effect dissolution of the plug may far exceed the amount required to sufficiently dilute the melt water. In fact, it may be necessary to entirely fill the pipeline from the point of injection to beyond the location of the hydrate plug with solvent. This large volume may exceed the total globally available solvent readily available on short notice. Other fluids, such as non-hydrate forming gases or liquids, such as oil or natural gas condensate, may be available to fill the pipe and deliver the hydrate-melting solvent to the plug, but many pipelines follow a course of rising and falling elevations along their route. The "valleys" formed between elevations serve as low points where higher density fluids may settle out. Generally, solvents effective for dissolving water and hydrate and preventing re-formation of hydrates are denser than oil, and especially gas condensate.

[0009] Conversely, the pill should spontaneously de-viscosify upon contact with the hydrate or water so as to release the solvent for combination with the aqueous phase.

[0010] Thus, there is a need for a means for viscosifying these solvents into a "pill" such that an effective volume of solvent may be delivered to the site of the hydrate blockage without filling the entire pipeline. That is, it is typically desirable to keep the volume of methanol, ethylene glycol, or other hydrate inhibitor applied to effect

dissolution of the hydrate plug as small as practicable; therefore, rather than applying a large slug of inhibitor, a smaller quantity, often termed a "pill," is often applied. To efficiently remove a gas hydrate plug via a remediating push pill, the pill should have a sufficient viscosity for effective emplacement. However, obtaining the necessary viscosity is complicated by the inability to use conventional viscosifiers to form the pill. Conventional viscosifiers, such as xanthan gum, hydroxyethyl cellulose (HEC), etc., result in hydration of the viscosifier as water is released from the gas hydrates. Thus, while the gas hydrate plug is freed, the hydrated polymer forms a highly viscous (even semi-solid) plug in its place and full gas flow in the pipeline cannot be achieved. Additionally, it may be also desirable for the viscosified pill to de-viscosify upon contact with the hydrate or water, so as to release solvent for combination with the aqueous phase.

[0011] Accordingly, there exists a continuing need for improvements in remediation treatments for gas hydrate agglomerates.

SUMMARY OF INVENTION

[0012] In one aspect, embodiments disclosed herein relate to a method for dissolving a gas-hydrate agglomerate, comprising introducing a push pill to the gas-hydrate agglomerate, the push pill comprising a hydrate inhibitor; and a viscosifying agent wherein when said viscosifying agent is exposed to free water, the viscosifying agent does not substantially result in an increase in viscosity.

[0013] In another aspect, embodiments disclosed herein relate to a method for treating a hydrocarbon conduit that includes emplacing a push pill in the hydrocarbon conduit, wherein the hydrocarbon conduit has a gas-hydrate agglomerate therein, the push pill comprising: a hydrate inhibitor; and a viscosifying agent wherein when said viscosifying agent is exposed to free water, the viscosifying agent does not substantially result in a increase in viscosity of the push pill; and substantially reducing the gas-hydrate agglomerate.

[0014] In yet another aspect, embodiments disclosed herein relate to a method for dissolving a gas-hydrate agglomerate that includes introducing a push pill to the gas- hydrate agglomerate, the push pill comprising: a glycol; a chelating or viscosifier- so lvati on-promoting agent; a viscosifier wherein when the viscosifier is exposed to free water, the viscosifier does not substantially result in an increase in the viscosity

of the treatment pill; and a glycol-soluble base capable of neutralizing or partially neutralizing acidity induced by the addition of said chelating or viscosifier-soϊvation- promoting agent.

[0015] Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

DETAILED DESCRIPTION

[0016] In one aspect, embodiments disclosed herein relate to push pills for use in remediating a conduit or pipeline having a gas-hydrate plug or agglomeration of crystals therein. In another aspect, embodiments disclosed herein relate to push pills that may be used in conjunction with other remediation techniques (such as hot condensates) to assist in remediating the conduit.

[0017] Specifically, a high glycol push pill is desired to assist in applying condensate at, for example, 80 ⁰ C to melt away a partial (~70%) plug in a 36" gas pipeline because the glycol will contact the hydrate. Alternatively, a high glycol push pill is desired to assist in applying condensate at, for example, 80 ⁰ C to melt away said partial plug in a 36" gas pipeline because as the hot condensate contacts hydrate agglomerates and begins to melt them, any water that comes from melted hydrate will be "sopped up" or captured by the glycol in the push-pill. Capture of the water released from the gas-hydrate is necessary to ensure that the released water does not subsequently cool down and re-form hydrates.

[0018] With most high glycol pills, however, when the pill is formulated with conventional polymers, such as, for example, HEC or xanthan gum, the pill will only have a suitable viscosity to serve as a push pill with a sufficient amount of polymer dissolved in the pill; but when the pill starts melting away the hydrate or when the hot condensate pill that the viscosified glycol pill is pushing begins to melt away the hydrate (or both), the resulting water can cause the polymer in the push pill to hydrate and yield, making a very high viscosity plug, even a semi-solid. Surprisingly, the present inventors have discovered that push pills can be formulated as disclosed herein that will effectively assist in the placement of a primary remediation technique, such as a hot condensate slug, and/or will not increase dramatically in viscosity when diluted with water.

[0019] In one embodiment, the push pills of the present disclosure may include a hydrate inhibitor, a viscosifier (or viscosifying agent), and optionally, a chelating agent (or viscosifier-solvation-promoting agent).

[0020J Hydrate inhibitors suitable for use in the remediating pills of the present disclosure include those compounds, such as glycols, methanol or other alcohols, or brine which act to melt gas-hydrate crystals, releasing water molecules from surrounding gas molecules. Without being bound to any particular chemical mechanism, the mechanism through which an alcohol may work to melt a gas-hydrate is thought to be twofold. First, an alcohol may form hydrogen bonds with water using its OH-groups, and secondly it tends to cluster water molecules around its hydrocarbon ends, which effectively "captures" the released water and may reduce or prevent any subsequent re-formation of gas-hydrates. However, one of ordinary skill in the art would recognize that other types of hydrate inhibitors that may act to release water from a gas hydrate are within the scope of the present invention. In a particular embodiment, the hydrate inhibitor may be present in the pill in an amount ranging from 30 to 99.9 percent by weight of the pill.

[0021] In one embodiment, the hydrate inhibitor may include a C2-C6 alkyl glycol.

In another embodiment, the hydrate inhibitor may include at least one of ethylene glycol, propylene glycol, butylene glycol, and combinations thereof.

[0022] Brines suitable for use as a hydrate inhibitor according to various embodiments of the present disclosure may include seawater, aqueous solutions wherein the salt concentration is less than that of sea water, or aqueous solutions wherein the salt concentration is greater than that of sea water. The salinity of seawater may range from about 1 percent to about 4.2 percent salt by weight based on total volume of seawater. The solutions typically contain metal salts, such as but not limited to, transition metal salts, alkali metal salts, alkaline earth metal salts, and mixtures thereof. Exemplary salts include halides of zinc, calcium, and mixtures thereof. For example, the solution can include zinc halide, such as zinc bromide or zinc chloride or both, optionally in combination with calcium bromide or calcium chloride or both. Salts that may be found in seawater include, but are not limited to, sodium, calcium, aluminum, magnesium, potassium, strontium, and lithium salts of chlorides, bromides, carbonates, iodides, chlorates, bromates, formates, nitrates, oxides, silicates, sulfates, phosphates, and fluorides. Salts that may be incorporated in

a given brine include any one or more of those present in natural seawater or any other organic or inorganic dissolved salts. Additionally, brines that may be used in the fluids disclosed herein may be natural or synthetic, with synthetic brines tending to be much simpler in constitution. In one embodiment, the density of the fluid may be controlled by increasing the salt concentration in the brine (up to saturation). In a particular embodiment, a brine may include halide or carboxylate salts of mono- or divalent cations of metals, such as cesium, potassium, calcium, zinc, and/or sodium. The brine solution can include the salts in conventional amounts, generally ranging from about 1% to about 80%, and preferably from about 20% to about 60%, based on the total weight of the solution, although as the skilled artisan will appreciate, amounts outside of this range can be used as well.

[0023] Further, embodiments of the present disclosure may further use "specialty" brines that include at least one alkali metal salt of a transition metal oxy-anion or polyoxy-anion, such as, for example, an alkali metal polytungstate, an alkali metal heteropolytungstate, an alkali metal polymolybdate or an alkali metal heteropolymolybdate.

[0024] Viscosifying agents or viscosifiers suitable for use in the pills of the present disclosure include those compounds that do not substantially hydrate or result in a substantial increase in a viscosity when exposed to free water. That is, as the gas- hydrate agglomerate is melted by the hydrate inhibitor of the present disclosure, releasing free water, the formation of a hydrated viscosifier may be at least reduced or prevented. In one embodiment, the viscosifier may be at least one of diutan gum. In a particular embodiment, the viscosifier may be present in an amount ranging from about 0.1 percent by weight of the pill up to its solubility limit in glycol. One of ordinary skill in the art would recognize that the amount of viscosifier will depend on the pill viscosity desired. One example of a viscosifier is ECF-612, which is commercially available from M-I LLC, Houston, TX, and which as a chemical structure as follows:

3 1 1 =--L-Rhap-(-i-*4)- ^y -L-Rtiap

[0025] In addition to diutan gum, one of ordinary skill in the art would recognize that other types of viscosifiers may be used that do not substantially hydrate or result in a substantial increase in viscosity when exposed to free water. For example, one of ordinary skill in the art would recognize that while some unmodified polymers may result in viscosity when exposed to free water, a crosslinked derivative may resist such substantial increases in viscosity. That is, by providing a crosslinked polymer that has already developed its maximum viscosity, exposure to free water will not result in a substantial increase in viscosity. WO07/005499, which is herein incorporated by reference in its entirety, describes such types of crosslinked polymers that may be used as a viscosifier in the push pill of the present disclosure. An example of a commercially available source of a crosslinked polymer additive that may be used in a push pill of the present disclosure is SAFE-LINK™, available from M-I LLC (Houston, Texas).

[0026] Embodiments of crosslinked polymers of the present disclosure may use a number of "natural" polymers. Such polymers include HEC, derivatized HEC, guars, derivatized guars, starches, derivatized starches, scleroglucans, wellan gums, locust bean gum, karaya gum, gum tragacanth, carrageenans, alginates, gum arabic, and biopolymers, such as, for example that derived from fermentation with xanthomonas campestήs, and other similar polymers.

[0027] Further, embodiments of the present disclosure may also use a number of

"synthetic" polymers, either exclusive of the aforementioned "natural" polymers or in combination therewith. "Synthetic" polymers include poly(ethylene glycol) (PEG), poly(diallyl amine), poly(acrylamide), poly(acrylonitrile), polyvinyl acetate),

poly(vinyl alcohol), poly(aminomethylpropylsulfonate[AMPS]), poly(vinyl amine), polyvinyl sulfonate), poly(styryl sulfonate), poly(acrylate), poly(methyl acrylate), poly(methacrylate), poly(methyl methacrylate), polyvinylpyrrolidone), poly(vinyl lactam), co-, ter-, and quater-polymers of the following co-monomers: ethylene, butadiene, isoprene, styrene, divinylbenzene, divinyl amine, l,4-pentadiene-3-one

(divinyl ketone), l,6-heptadiene-4-one (diallyl ketone), diallyl amine, ethylene glycol, acrylamide, AMPS, acrylonitrile, vinyl acetate, vinyl alcohol, vinyl amine, vinyl sulfonate, styryl sulfonate, acrylate, methyl acrylate, methacrylate, methyl methacrylate, vinylpyrrolidone, vinyl lactam and other similar polymers.

[0028] In selected embodiments, crosslinked HEC and its derivates may be used as the viscosifier to form the push pill of the present disclosure. In particular, in one embodiment, ECF-680 may be used. ECF-680 is a slurry of a doubly derivatized hydroxyethyl cellulose in an inert, water-miscible carrier fluid. ECF-680 is available commercially from Special Products, Inc., a subsidiary of Champion Technologies,

3130 FM 521, Fresno, TX 77245, USA. DDHEC may be synthesized by grafting monomers of vinyl phosphonic acid (VPA) onto cellulose polymers according to methods disclosed in U.S. Pat No. 5,304,620 (Holtmyer '620), U.S. Pat. No.

5,439,057 (Weaver '057), and U.S. Pat. No. 5,996,694 (Dewprashad '694). Those patents ('620, '057 and '694) are incorporated by reference in their entirety.

[0029] In order to form a suitable crosslinked polymer, typically a crosslinking agent must be added to whatever polymer - natural or synthetic - is used. In select embodiments, magnesium oxide is used as a crosslinking agent or as a crosslinking activator. One suitable form of magnesium oxide is a very fine powder is a highly reactive form, i.e., having small particle size, high surface area, and ready accessibility for reaction. One example of such a fine powder magnesium oxide is available commercially from M-I LLC under the trade name of DI-BALANCE™.

One useful feature of the magnesium oxide system is that the crosslinking does not occur immediately, but instead occurs over the course of several hours, leading to doubling of the apparent viscosity of the mixture during the first part of an hour and gradually increasing to about 50 percent of its ultimate value upon sitting for several hours at room temperature.

[0030] Alternatively, other polymers similar to DDHEC may be used including, for example, similarly modified cellulose, guar, or hydroxypropyl guar or synthetic co- or ter-polymers in which one of the co-monomers is vinyl phosphonic acid, such as, for example, those disclosed in U.S. Patent Application No. 60/948,833, filed on July 10, 2007, which is assigned to the present assignee and herein incorporated by reference in its entirety. Also, it will be obvious to one skilled in the art that other methods may be used to effect the same result - for example, applying a mildly complexed crosslinkant which becomes slowly un-complexed in order to effect the initial crosslinking, and subsequently applying a stronger complexing additive to effect the breaking (un- crosslinking).

[0031] Further, other compounds for crosslinking HEC may be used. For example, it is known that titanium or zirconium may be used to crosslink HEC. U.S. Patent No. 6,342,467, for example, discloses one method for crosslinking HEC that involves the use of zirconium or titanium. Thus, the crosslinking agent can be any convenient source of zirconium ions. According to that patent, which is incorporated by reference in its entirety, a preferred crosslinking additive is a zirconium chelate such as zirconium lactate. Other suitable zirconium compounds include zirconyl chloride, sodium zirconium lactate and zirconium acetylacetonate. The delay agent is preferably the sodium counterpart of these zirconium compounds.

[0032] In addition, while specific mention is made of HEC and its derivatives in other embodiments, guars, derivatized guars, and other similar polymers may be used in accordance with embodiments of the present disclosure.

[0033] It is also within the scope of the present disclosure that the push pill may include a mixture of viscosifiers such that the mixture of viscosifiers does not substantially hydrate or result in a substantial increase in viscosity when exposed to free water. For example, it is specifically within the scope of the present disclosure that a mixture of viscosifiers, such as diutan and HEC or xanthan gum, may be used in the push pill. One of ordinary skill in the art would recognize that the amounts or ratios of diutan to either HEC or xanthan gum, for example, may depend on the ability of the mixture to avoid substantial hydration. In a particular example, a push pill may contain 1.33 ppb diutan (such as ECF-612, available from M-I LLC) with either 0.133 ppb HEC or 0.133 ppb xanthan gum (such as FLO- VIS ^® , available from M-I LLC).

[0034 j It is also within the scope of the present disclosure that one embodiment of the viscosified push pill of the present disclosure may be formed in situ, for example, by crosslinking between glycol, such as those described above, and calcium present in a brine. Thus, such resulting crosslinked glycol push pill may include both the hydrate inhibitor and viscosifier as described herein. The formation of a plug by the reaction of calcium and a glycol is described in U.S. Patent Application Serial No. 11/683,781 which is herein incorporated by reference in its entirety. In a particular embodiment, a calcium brine may be present in or may be injected into a conduit having a hydrate agglomerate therein. A glycol pill may be emplaced in the conduit, whereby upon reaction with calcium, the push pill of the present disclosure may be formed in situ. Upon dissolution of the hydrate agglomerates, the water activity of the released water may be reduced by presence of the pill components such that hydrate agglomeration may be reduced or prevented.

[0035] Various chelating agents include at least one of ethylenediamine tetraacetic acid, citric acid, glutamic diacetic acid, nitrilotriacetic acid, the alkali and alkaline earth salts of these, and combinations thereof. In a particular embodiment, the chelating agent may be present in amount ranging from about 0.1 percent by weight of the pill up to its saturation point in the glycol. In other embodiments, no chelating (or viscosifier-solvation-promoting agent) is present in the push pill. In other embodiments, a viscosifier-solvation-promoting, for example ethylene glycol, propylene glycol, and/or butylene glycol, may be used to assist in the formation of the push pill.

[0036] For example, in a particular embodiment, a viscosifier-solvation-promoting agent may be used as a "co-solvent" to hydrate or solvate a solid or slurry of viscosifier, such as a DDHEC. Upon the addition of brine and an acid to lower the pH, the polymer (which was supplied in an anionic form) may readily solvate in its nonionic form. Once solvated, a crosslinking agent, such as MgO, may be added to raise the pH and cause crosslinking of the polymer and an increase in the viscosity of the pill.

[0037] Additionally, in some embodiments, a glycol-soluble base may be included in the push pill that is capable of neutralizing or partially neutralizing acidity induced by the addition of said chelating or viscosifier-solvation-promoting agent. For example,

in particular embodiments, the glycol-soluble base may include a morpholine or a morpholine process residue

[0038] Specifically, in one or more disclosed embodiments, mixtures of the following compounds, listed below in Table 1, may be used, wherein ECF-612, ECF-687, SAFE- COR™, SAFE-CIDE™, and EMI-530 are available from M-I LLC, Houston, TX.

Table 1

[0039] Embodiments disclosed herein may further comprise other additional components, including, but not limited to, different controlling chemistries such as neutralizers, corrosion inhibitors, wax inhibitors, asphaltene inhibitors and other hydrate inhibitors and/or solvents.

[0040] In various embodiments, the push pill disclosed herein may also contain at least one additional salt, including any salt that may be incorporated in brines, as disclosed herein. In particular embodiments, at least one of sodium chloride, calcium chloride, potassium chloride, and sodium carbonate may be incorporated in the push pill disclosed here. In one embodiment, the at least one additional salt may incorporated into the push pill disclosed herein in an amount ranging from about 0.5 weight percent to salt saturation.

[0041] As described above, a push pill of the present disclosure may emplaced in a conduit in a variety of manners and means, such as by a progressive cavity pump, and may be moved within the conduit as a piston, with the application of pneumatic or hydraulic pressure. In various embodiments, the movement of the push pill may be used to push or convey materials (fluid or solid materials) along the conduit and/or may be used to separate two species from each other in the conduit.

[0042] It is specifically within the scope of the present disclosure that a push pill(s) of the present disclosure may be emplaced to dissolve a hydrate agglomerate, assist in absorbing water released from a hydrate agglomerate, and/or assist in the emplacement of a hydrate inhibitor, for example, an unviscosified inhibitor, to dissolve a hydrate agglomerate.

[0043] In one embodiment, a first push pill comprising a glycol and a diutan gum may emplaced, optionally behind a slug of unviscosified hydrate inhibitor(s) and/or a slug of hot condensate. A second pill comprising a brine and a crosslinked DDHEC may optionally be emplaced in conjunction with (either prior to or following) the first pill, or alternatively, the second pill may be emplaced without the first pill. Once a hydrate agglomerate is broken, the push pills of the present disclosure may be pumped from the conduit, such as by means similar to those used in emplacing the pill, or alternatively, in the case of a crosslinked viscosifier, the pill may be optionally "broken" in situ, for example, by the application of a weak acid or pH 4 buffer solution.

[0044] In yet another embodiment, if the gas hydrate plug has separated a pipe into two zones: a high pressure zone between the head well and the hydrate plug and a low pressure zone between the hydrate plug and the production facilities area, then it may be desirable to inject a push pill into the low pressure zone between the hydrate plug and the production facilities area. Then the pressure in the pipeline may be raised in the zone between the push pill and the production facilities area, preferably to the point that the pressure between the push pill and the production facilities area is equal to or greater than that in the "high pressure" zone between the head well and the hydrate plug. This pressurization could be effected using "dry" gas containing little or no hydrate-forming components or condensate or diesel fuel containing little or no hydrate-forming components. At the same time, hot condensate, for example, may optionally be injected between the push pill and the hydrate plug. Preferably the composition of the hot condensate would be controlled so as to contain little or no hydrate-forming components. This injection may be accompanied by further increase in the pressure between the push pill and the production facilities area so that if the hydrate plug were suddenly to become unstuck from the pipe wall, any projectile generated would tend to move away from the facilities apparatus, reducing or eliminating any risk that the pipeline in this area or the production facilities farther

downstream might be damaged. While there may still be a potential risk for generation of a projectile, in some embodiments, this may be desired, such as when the pipeline leading to the reservoir and the reservoir itself possess a buffering volume that could receive the reflux without much increase in pressure.

[0045] Further, one of ordinary skill in the art would appreciate that, in addition to use in conduits or pipelines, the remediation techniques of the present disclosure may also be used in any other types of storage vessels or containers in which gas hydrates may have formed, such as, for example, natural gas storage chambers.

[0046] EXAMPLES

[0047] Example 1

[0048] Two remediating push pill, Pills 1 and 2, were formulated as shown in Table 2 below.

Table 2

[0049] The rheology of Pills 1 and 2 was investigated, at various temperatures and conditions, with increasing amounts of water present, using a Farm 35 viscometer. The results are presented in Table 3a and 3b below.

Table 3 a

Table 3b

[0050] Tables 3a and 3b shows that Pills 1 and 2 have a sufficient viscosity for effective emplacement, and are likely to act as thermodynamic hydrate inhibitors which will contact the hydrate condensate directly, melt or extract water therefrom, and thereby remove the blockage from the pipeline. Further, as Pills 1 and 2 were diluted with increasing amounts of water, it can be shown that the viscosity of the fluid did not substantially increase, and in fact the rpm measurements show a decrease in viscosity.

[0051] Example 2

[0052] Three remediating push pill, Pills 3-5, were formulated as shown in Table 4 below.

Table 4

[0053] The rheology of Pills 3-5 was investigated, at various temperatures and conditions, using a Fann 35 viscometer. The results are presented in Table 5 below.

Table 5

[0054] Example 3

[0055] A remediating push pill, Pills 6, was formulated as shown in Table 6 below.

Table 6

[0056] The rheology of Pill 6 was investigated, at various temperatures and conditions, using a Fann 35 viscometer. The results are presented in Table 7 below.

Table 6

(0057] Advantages of embodiments of the present disclosure may include one or more of the following. A push pill having properties, such as viscosity, thermal stability, ability to suppress conductive heat loss, and/or heat conveyance, may be used in remediating conduits having gas-hydrate agglomerates stuck therein. If used

in conjunction with a primary remediation technique, such as a hot condensate, the pills of the present disclosure may capture released water to at least reduce the incidence of further formation of gas hydrates.

[0058] Additionally, the pill may have a sufficient viscosity to drive the emplacement of a hot condensate to the blockage in a conduit, while remaining intact with close exposure to the elevated temperature of the hot condensate. Further, a sufficient emplacement viscosity may be obtained with minimal occurrence of complicating side effects, such as polymer hydrate blockage. When a pill of gas condensate along with the solvents effective for remediation of the hydrate plug and preventing reformation of hydrates, is confined ahead of a "push pill", then there may be a greater chance of keeping the applied volumes to a manageable size, of avoiding the separation of the disparate density fluids into separate slugs, and of avoiding the loss of portions of the fluids into falling elevations along their route.

[0059] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

[0060] All priority documents are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted. Further, all documents cited herein, including testing procedures, are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted to the extent such disclosure is consistent with the description of the present invention.