Antifreezing and anti-blocking method of natural gas runner

Abstract

The invention discloses an antifeezing and anti-blocking method of a natural gas runner, which comprises the following steps: periodically adding antifreeze into the natural gas runner so as to reduce the dew point of the natural gas and the freezing point of the water in the natural gas runner, and prevent the water from freezing and blocking the natural gas runner. The invention can effectively solve the problems that the natural gas runner is frozen and blocked, mixed solid content formed by natural gas hydrate and ice block the natural gas runner, also can greatly reduce the dew point of the natural gas, cosmically simplify the productive process of the natural gas, particularly, cosmically simplify the natural gas ground surface gathering process, greatly reduce the cost of the natural gas production, energy consumption, gas self consumption, management working load, and the like, fundamentally eliminate methanol harm and pollution in the natural gas production, realize non alcoholization of the natural gas productive process, and has the advantages of easy implementation, safety and reliability, wide application, easy popularization and the like. The economic benefit, environmental protection benefit and safety benefit are remarkable.

Description

technical field [0001] The invention relates to the fields of natural gas production, storage and transportation of natural gas, in particular to a method for antifreezing and unblocking of natural gas flow channels. Background technique [0002] "Oilfield Chemistry", page 269, line 10-11 of the first printing of the first edition of China University of Petroleum Press in July 2000, stated: "Under formation conditions, natural gas is in contact with water, so natural gas always contains A certain amount of water vapor." The water vapor will condense into water when the temperature is low, and freeze when the temperature is lower than the freezing point (or freezing point) of water, freezing and blocking natural gas wellbore, wellhead, pipeline, valve, flow meter, etc. The flow channel of natural gas prevents the process of natural gas production, gathering and transportation, storage and transportation from proceeding normally. [0003] Public information shows that some na...

AI Technical Summary

Problems solved by technology

The defect of this method is: to improve the temperature of natural gas flow or natural gas and water mixed fluid with the method of heating (as the method for heating furnace), prevent water from freezing (being antifreezing) in the natural gas flow channel, or the natural gas flow channel Ice is melted to dredge the natural gas flow channel (i.e. blockage removal); heating requires a large amount of energy and natural gas, which will greatly increase the energy consumption, cost, fixed investment, and management workload of natural gas production, and complicate the natural gas production process; therefore, this method Although it has been used on a large scale in China at present, it has been actively seeking alternative methods

[0016] (2) Methanol is a flammable, explosive, and highly toxic chemical. If the intake exceeds 4 grams, a poisoning reaction will occur. If more than 10 grams are taken by mistake, it can cause blindness. The lethal dose is about 70 milliliters. Methanol vapor can Seriously injure the nerves of the eyes, a large amount of use will not only seriously endanger the health of the operator, but also pose a major safety hazard;

[0017] (3) Public information shows that when the concentration of alcohols is low, alcohols will accelerate the formation of natural gas hydrate, such as methanol or ethylene glycol aqueous solution with a concentration of 1wt%-5wt% can accelerate the formation of natural gas hydrate; When the pressure is 20MPa and the temperature is 0-25°C, the concentration of methanol in the water phase must exceed 29wt% to effectively inhibit the formation of natural gas hydrate; therefore, if the concentration of alcohols is low, although it can effectively reduce the freezing point of water, However, it will lead to the defect that natural gas hydrate blocks the natural gas flow channel; therefore, it is necessary to use a high concentration of alcohols to effectively solve the problem of natural gas flow channel blockage, and its concentration generally reaches 20%-50% of the water content; therefore, the method would substantially increase the cost of natural gas production

[0018] (4) After methanol is added to the natural gas flow channel, only a small part of the methanol vapor is mixed with the natural gas, and is eventually burned with the natural gas; most of the rest of the methanol enters the sewage separated from the natural gas to form toxic methanol sewage; although these are toxic Methanol sewage can be treated with existing methods to recover most of the methanol, but the remaining part of methanol cannot be fully recovered by existing methods, or the recovery cost is too high to give up recycling; although the toxic sewage after methanol recovery is still Contains a small amount of methanol, but because it has no use value, it will eventually be discharged into the ground environment or injected into the ground, seriously polluting the ground environment or underground environment; recovery of methanol requires high recovery costs, and consumes a lot of energy and natural gas. Toxic sewage after methanol is injected into the ground also consumes a lot of electricity

[0019] (5) Since the melting of ice and natural gas hydrate is an endothermic process, it can be known from thermodynamic knowledge that hot liquid has a stronger ability to melt ice or hydrate, and hot methanol has a stronger ability to melt ice; however, public information shows that, Methanol has a high vapor pressure, a boiling point of 64.7°C, and a closed flash point of 11°C. Therefore, methanol cannot be used by heating, and can only be used at room temperature or low temperature, which greatly reduces its ability and efficiency to melt ice and natural gas hydrate. Its unblocking ability and efficiency

[0024] (2) It can be seen from the knowledge of thermodynamics that the temperature drop caused by throttling and pressure reduction has nothing to do with heat loss, so this method cannot solve the problem of water freezing and blocking in the natural gas flow channel caused by throttling and pressure reduction

[0025] (3) This method cannot melt the ice that has formed, and cannot solve the problem of freezing and freezing that has formed in the natural gas flow channel

Due to the huge difference between the production of natural gas from the "underground hydrate system" and the production of natural gas from ordinary natural gas reservoirs, the two belong to completely different technical fields, and the application of this invention to ordinary natural gas production will inevitably involve huge fixed investment and huge safety hazards. Defects such as huge operating costs, serious waste of resources, huge carbon dioxide emissions, huge energy consumption, and extremely complex processes will lead to complex natural gas production processes, equipment, and facilities, which are not as economical and practical as existing domestic natural gas production methods; therefore, domestic This type of test application is not currently carried out in natural gas production

[0029] (2) This invention does not solve the harmless problem of a huge amount of solids produced by "heating" described in its technical solution, and does not solve the process of "dilute aqueous solution" being concentrated and regenerated into "aqueous solution" and the prevention of "heating" and heat exchange. Problems such as scaling, descaling, anti-corrosion, etc., did not solve the problem of continuous enrichment of metal ions and mineral ions in the "regenerated aqueous solution", and did not solve the problem of "regenerated aqueous solution" before "recycling" and during the "regeneration" process The problems of various water-insoluble substances, sulfides, supersaturated crystals and precipitates have not been solved, and the purification problem of the "regenerated aqueous solution" before "recycling" has not been solved; it not only seriously affects the recycling of the "aqueous solution", but also if the Discharge of these waste substances into the environment will seriously pollute the environment; allowing these waste substances to "recycle" into the wellbore and pipeline with the "regenerated aqueous solution" will aggravate the fouling of the wellbore and pipeline, and even block the wellbore and pipeline

Therefore, it is difficult to directly implement the technical solution described in this invention, and it is difficult to be directly applied to domestic natural gas production

[0030] (3) Although the patent indicates that "aqueous solution containing 10-75 wt% alkali metal formate or acetate" is a very effective antifreeze agent and can "inhibit the formation of hydrocarbon hydrates"; however, it discloses The data show that there are many kinds of commercial antifreeze agents at present, not just the "aqueous solution" described in the patent, most inorganic salts such as calcium chloride, potassium chloride, and magnesium chloride aqueous solution are very effective antifreeze agents, but because calcium chloride, potassium chloride, and magnesium chloride aqueous solution are all very effective antifreeze agents, Potassium chloride and magnesium chloride aqueous solution antifreezes have strong electrochemical corrosion and will seriously damage natural gas production facilities. China's petroleum industry clearly stipulates that these antifreezes are not allowed to be artificially added to natural gas flow channels, let alone used to solve natural gas flow channels. However, it can be seen from the above that not all substances that can inhibit natural gas hydrate can effectively solve the problem of freezing and freezing of natural gas flow channels; The problem of freezing and blocking of natural gas channels (or anti-freezing and unblocking of natural gas flow channels) belongs to two different technical fields. Whether the "water solution" mentioned in the patent can "inhibit the formation of hydrocarbon hydrates" and whether it can solve the problem of freezing and freezing of natural gas flow channels (or natural gas Anti-freezing and unblocking of flow passages) also belong to two different technical fields; therefore, since the patent does not explicitly mention that the "aqueous solution" can effectively melt the ice in the natural gas flow passage, it does not explicitly mention that the "aqueous solution" can be used for Solving the problem of icing and freezing of natural gas flow channels does not involve or disclose the specific application of the "aqueous solution" to effectively melt the ice in the natural gas flow channel and solve the problem of icing and freezing of natural gas flow channels. Those of ordinary skill in the art cannot use this invention Enlightened by the solution to the problem of freezing and blocking of natural gas channels, it is also impossible to utilize the "aqueous solution that contains 10-75 wt% formate or acetate of alkali metals" described in the invention as "a very effective antifreeze" and can The expression "inhibiting the formation of hydrocarbon hydrate" is inspired to solve the problem of freezing and freezing of natural gas flow channels

[0031] Similarly, although the public information shows that one of the main components of the "aqueous solution" described in the invention, potassium formate, is a deicing agent, which can be used to melt snow and reduce the harm of snow; yet, the current public information does not involve the application of Potassium formate, formate, and acetate solve the problem of freezing and freezing of natural gas flow channels; there is no public information showing that potassium formate, formate, and acetate can be used to solve the problem of freezing and freezing of natural gas flow channels, and there is no solution A public technical solution for the problem of icing and freezing of natural gas flow passages; since snow and ice in natural gas flow passages are not of the same kind and there is a big difference, melting snow and melting ice belong to different technical fields, and melting snow and preventing water from freezing also belong to different fields In the technical field, melting snow and preventing water from freezing and freezing in the natural gas flow channel belong to different technical fields; therefore, it is difficult for those skilled in the art to effectively solve the problem of freezing and freezing of the natural gas flow channel based on public information

[0032] (4) This patent only shows that the "aqueous solution" mainly composed of alkali metal formate or acetate has the function of dissociating (melting) natural gas hydrate and preventing the formation of natural gas hydrate. The freezing point of the "aqueous solution" itself is below zero, but its technical proposal does not mention that the "aqueous solution" has sufficient capacity to melt ice and remove freezing blockages. Calculations show that the technical proposal cannot meet the requirements of melting ice in the natural gas flow channel. In order to clear the natural gas flow channel (i.e. blockage removal), those of ordinary skill in the art cannot effectively solve the icing and freezing blockage that has formed in the natural gas flow channel by using the "aqueous solution" (or "antifreeze") and its application technical solution disclosed in this invention. Problems (i.e. unable to achieve effective blockage removal), specifically as follows:

[0045] According to public information and thermal calculations, it can be seen that the lowest temperature in winter in various gas fields located in northern China, such as Qingshen Gas Field (located in Daqing City) and Sulige Gas Field (located in Ordos City), can reach below -31°C. It is a common phenomenon that the temperature is lower than -15°C. After the natural gas pipeline is frozen and blocked, the lowest temperature can reach the lowest ambient temperature, that is, below -31°C; the maximum temperature drop when natural gas is throttling can reach more than 40°C. The temperature drop generally exceeds 20°C, and the temperature after throttling can reach below -15°C; if the "aqueous solution" is used to melt the ice in the natural gas flow channel according to the technical solution described in the invention to dredge the natural gas flow channel (i.e., unblock ), even if it belongs to formate or acetate aqueous solution with a saturated concentration, the freezing point of the diluted dissociated hydrate injected into the ground may be about -6°C or even higher, and it is difficult to reach -15°C or even -31°C Therefore, the ice in the natural gas flow channel cannot be effectively melted to dredge the natural gas flow channel (that is, blockage removal);

[0046] Therefore, the "aqueous solution" (or "antifreeze") disclosed by the invention and its application technical solutions cannot be effectively solved by those skilled in the art to effectively solve the problem of freezing and freezing that has formed in the natural gas flow channel (that is, effective deblocking cannot be achieved)

[0047] (5) Since this invention does not provide the technical scheme of adding the "aqueous solution" directly as an antifreeze to the natural gas flow channel to prevent the water in the natural gas flow channel from freezing and blocking the natural gas flow channel, nor does it provide other "aqueous solution" As an antifreeze agent to prevent the water in the natural gas flow channel from freezing and blocking the natural gas flow channel, those of ordinary skill in the art can not solve the problem of preventing water from freezing in the natural gas flow channel according to the technical solution provided by this invention (ie, antifreeze)

[0057] ②According to the solution theory, it can be seen that in the aqueous salt solution, the lower the concentration of the salt, the greater the partial pressure of the water vapor; such as the partial pressure of the vapor partial pressure of the potassium formate aqueous solution with a concentration of 10% is much higher than that of the potassium formate aqueous solution with a concentration of 50%; if according to The technical solution described in this invention absorbs water vapor from natural gas. When the aqueous solution reaches absorption equilibrium, the water vapor partial pressure will be very high, and the corresponding water vapor partial pressure or content in natural gas will also be high, that is, the natural gas The dew point is also high, which cannot meet the requirements of natural gas export

[0062] Therefore, although the "aqueous solution" disclosed in the invention can absorb water vapor in natural gas and has the function of a hydrocarbon dehydrating agent, since the invention does not clearly specify other specific technical solutions for using the "aqueous solution" as a dehydrating agent, the provided The technical solution of this patent cannot solve the problem of water vapor condensing and freezing to block gas pipelines during natural gas transportation, so that those skilled in the art cannot use the technical solution described in this patent to solve the problem of water vapor condensing and freezing to block natural gas pipelines during natural gas transportation question

Therefore, there is no application test research on the "aqueous solution" described in the invention as a natural gas dehydrating agent in China at present.

[0063] (7) The invention does not involve or provide a technical solution for melting the ice in the natural gas flow channel to dredge the natural gas flow channel (i.e., unblocking), and its technical solution of using the "aqueous solution" as an antifreeze agent does not make full use of the "aqueous solution" The characteristics of "enhanced its ability to melt the ice in the natural gas flow channel. If its technical solution is used to melt the ice in the natural gas flow channel to dredge the natural gas flow channel (that is, blockage removal), the cost of blockage removal for natural gas production will be greatly increased.

[0073] In short, the current methods to solve the problem of freezing and freezing of natural gas channels have certain defects.