Oil field gas (i.e. crude oil associated gas) gathering and transportation system engineering generally includes: gas gathering, gas processing; Transportation of dry gas and light hydrocarbon; Sealed transportation of crude oil, stability of crude oil, storage of light hydrocarbon, etc. Oil field gas collection After the crude oil comes out of the oil well and is measured by the metering separator, the oil and gas are transported into the oil and gas separator of the oil transfer station. Oilfield gas is separated from crude oil and enters into the gas gathering network. Generally, self-pressure or booster gas gathering station is built in the combined station of oil production plant. Booster compressors are mostly multi-unit single-stage reciprocating compressors. The inlet pressure can float, and the outlet pressure depends on the system back pressure. The maximum outlet pressure is 0.4MPa. Closed gathering and transportation of crude oil Closed gathering and transportation of crude oil is the primary condition for extracting light hydrocarbon from crude oil by crude oil stabilization method, and it is also one of the important measures to reduce the loss of crude oil. At the oil transfer station, the crude oil passing through the oil-gas separator enters the free water stripper, and then is sent to the crude oil dehydration station through the water bearing buffer tank and the export heating furnace. Here, the crude oil passes through the free water remover, then enters the dehydration heating furnace for heating, and then enters the composite electric dehydrator. After dehydration, the crude oil enters the buffer tank (the water content of the crude oil is less than 0.5%), and then is pumped into the crude oil stabilization unit, and after stabilization, the crude oil enters the storage tank for export. In the closed process of oil transfer station and dehydration station, free water is discharged in advance and mixed into oilfield injection water locally to reduce production energy consumption. Processing of oilfield gas The oilfield gas from the self-pressure station enters the shallow cooling (or cryogenic) unit, where it is pressurized, frozen and separated together with the non-condensable gas from the crude oil stabilization unit to recover the components above C3 (or C2), and the dry gas is exported. Light hydrocarbon gathering and transportation system Light hydrocarbon gathering and transportation adopts pipeline transportation mode, and the system is composed of auxiliary storage, transfer station, general storage, export metering station and corresponding pipe network. The light hydrocarbon recovery unit is equipped with a storage tank, which is used for settlement dehydration, product reconciliation, buffer of export pump and export pipeline to ensure normal production or planned shutdown of the unit in case of accident. The storage capacity of the storage tank is generally 1 to 2 days of light hydrocarbon production. The main function of light hydrocarbon transfer depot is to use the depot to coordinate the imbalance between light hydrocarbon production and export in one day, and to store and clean the pipeline effusion in case of pipeline accident. The main function of the general light hydrocarbon storage is to use the storage tank to coordinate the imbalance between light hydrocarbon production and export, including the output fluctuation of the production unit, the output fluctuation caused by different maintenance periods of the unit, the ethylene plant maintenance without ammonia maintenance, and the oil field needs to continue to provide the storage of light hydrocarbon recovered from the feed gas. Light hydrocarbon general storage and total export metering station are the main outlets of liquid hydrocarbon raw materials provided by oil field for ethylene plant, the gathering place of light hydrocarbon produced by various light hydrocarbon recovery units, and the hub of light hydrocarbon storage and transportation system. Export and return system of dry gas The oil field gas is treated and processed after recovery. Most of the dry gas after recovery of light hydrocarbon is sent to Dahua and methanol plants as chemical raw materials, and part of the dry gas is sent back to the oil transfer station on the oil field as fuel for heating furnace and boiler. The dry gas return is the reverse process of gas gathering. At the same time, some of the dry gas is injected into the gas storage in summer. It is produced in winter to ease the shortage of natural gas supply and demand. Some of the dry gas is used to generate electricity and gas for residents.