Safety technology for production and treatment of

Natural gas production and treatment safety technology

the natural gas extracted from oil and gas fields is mainly a mixture of hydrocarbons dominated by methane (the methane content of the associated gas of the oil field generally accounts for 80% - 90%, and the methane content of the gas field generally accounts for more than 90%), and also contains a small amount of CO2, H2, N2, H2O and other components. The natural gas extracted from some gas fields also contains H2S and organic sulfur (thioether, mercaptan) and other components. When natural gas flows from the formation to the bottom of the gas well and flows to the surface along the wellbore, it often carries impurities such as formation water, sediment and rock cuttings. Some gas fields also produce light condensate. Therefore, natural gas must undergo a series of treatment in the production process. Natural gas production and treatment generally include the following processes: corrosion inhibitor injection, depressurization, heating, separation, metering, pressure regulation, pressurization, etc. For sour gas fields, the natural gas produced shall be desulfurized and dehydrated. Only when the treated natural gas meets the pipeline transportation standard can it be transported into the pipeline to promote close contact with customers for use by factories, mines and urban residents

1. inject corrosion inhibitor. For sour gas wells, in order to inhibit and slow down the corrosion of hydrogen sulfide gas to the tubing and casing in the well, a certain amount of corrosion inhibitor should be regularly injected into the well. When the corrosion inhibitor flows through the oil in the well to prevent the virus from infecting the pipe and casing, it attaches to the inner and outer walls of the steel pipe to form a protective film, which separates H2S, CO2 and other corrosive gases from the steel pipe and plays an anti-corrosion role

2. Reduce blood pressure. High pressure natural gas must be depressurized to reach the allowable pressure of equipment and pipelines before flowing into equipment and pipelines. Usually, the pressure reducing device used is an angle throttle valve

3. heating. High pressure natural gas will produce "throttling effect" during pressure reduction, expand and absorb heat, and reduce temperature. When the temperature drops to a certain extent, methane combines with the water in natural gas to produce a white crystalline substance like ice and snow, which is usually called hydrate. Hydrate accumulation in gas production equipment and pipelines will cause blockage, pressure rise, and abnormal gas well production. In serious cases, it will cause pressure suppression and explosion of equipment or pipelines. In order to prevent the formation of hydrate, water jacket heating furnace can generally be used to increase the temperature of natural gas or add antifreeze such as methanol and ethylene glycol to natural gas to destroy the conditions of hydrate formation, so as to ensure normal production

4. separation. The heated natural gas flow is sent to the separator to remove oil, water and solid impurities. The oil is put into the oil storage tank for storage and transportation. The water and solid impurities are discharged into the sewage pool for treatment, and the formation water is injected back into the waste well

5. measurement. In order to understand the productivity and reserves of gas wells, the separated oil, gas and water should be measured separately. At present, the most widely used natural gas metering device at home and abroad is the standard orifice throttling device

6. pressure regulation. The natural gas is output after reaching the pressure required by the pipe or user through the pressure regulating device

7. pressurize. In the late stage of oil and gas field development, more than 90% of the sales of natural Liansu comes from the pressure failure of plastic pipes and accessories or the shallow low pressure obtained by drilling. When its pressure is lower than the pressure of pipeline gas, it can be exploited by booster compressor to improve the recovery of natural gas in oil and gas fields

8. desulfurization and dehydration. In order to protect the pipelines of gas production equipment from H2S corrosion and ensure that the H2S content of natural gas supplied to factories, mines and cities meets the national standards, sulfur-containing natural gas must be desulfurized and dehydrated. Desulfurization methods are divided into dry method and wet method. Low sulfur gas is treated by dry method, and high sulfur gas is treated by wet method

occupational hazards common hazards in natural gas production and treatment include explosion, fire and poisoning. The main causes are corrosion, overpressure, leakage, violation of operating procedures, etc. If H2S in natural gas exceeds a certain concentration, and in the environment with water, serious corrosion will occur to equipment and pipelines. H2S dissolves in water to form weak acid, which causes electrochemical weightlessness corrosion, hydrogen embrittlement and sulfide stress corrosion cracking to metals, and may cause pipeline and equipment explosion in serious cases. H2S is a colorless, highly toxic and acidic gas. The Low Concentration H2S gas has the smell of rotten eggs. Its relative density is 1.176, which is heavier than air. When it is mixed with air at a concentration of 4.3% - 46%, it forms an explosive mixture. H2S burns with a blue flame, producing toxic SO2

1. explosion. Gas transmission equipment (instruments) and pipelines are under pressure for a long time. These equipment and pipelines have rated working pressure, and their production and operation pressure must be lower than the rated working pressure. Explosion is likely to occur when the following conditions occur:

(1) the operator violates the operating procedures, resulting in overpressure operation of the equipment or pipeline

(2) equipment or pipeline thinning due to corrosion

(3) when the equipment or pipeline leaks, look for the operating principle of the engine in the day of leakage, when the natural gas is mixed with air to a certain proportion and in contact with the open fire

(4) when the gas well is drained with air compressor, the air and natural gas mix and flow under high temperature and pressure

2. Fire. The main causes of natural gas fire are:

(1) equipment and pipelines leak natural gas due to manufacturing defects, corrosion and wear, aging, etc., and ignite in case of open fire

(2) the blowout natural gas was ignited by lightning

(3) ignition in violation of operating procedures when repairing equipment and pipelines

3. Poisoning. The most common poisoning is caused by H2S and Co, but the toxicity of H2S is 5 ~ 6 times greater than that of Co

the main causes of hydrogen sulfide poisoning are:

(1) when sulfur-containing natural gas is discharged or leaked in the air, people and animals are poisoned after careless breathing, and death will be caused in serious cases

(2) when natural gas is used as fuel for cooking, heating and shower, incomplete combustion or poor ventilation will cause poisoning or suffocation, and even death in serious cases