A method for recovering oilfield associated gas

Abstract

The invention provides a recovery method of associated gas of an oilfield. A gas phase of a raw material subjected to primary gas-liquid separation is subjected to secondary gas-liquid separation anddewatering after being compressed and cooled, a liquid phase subjected to primary gas-liquid separation is subjected to flash evaporation, dewatering and steam stripping, and a gas phase obtained through steam stripping and a gas phase obtained after flash evaporation enter a dewatering link after two times of compression cooling; the gas phase subjected to dewatering drying is cooled and then subjected to low-temperature gas-liquid separation, a liquid phase subjected to low-temperature separation is heated and then subjected to ethane removal, the liquid phase with ethane removed is heated for butane removal, a liquid-phase LPG product is obtained, part of liquid-phase condensate oil with butane removed is cooled to serve as an absorbent and then subjected to multi-stage mass transfer and heat transfer with a gas phase subjected to low-temperature separation in the liquefaction step, the gas phase obtained after mass transfer and heat transfer serves as lean gas to be recovered afterbeing subjected to cooling, low-temperature separation, pressure reduction and cold recovery. High-value LPG products in the associated gas of the oilfield can be recovered, and the production cost is greatly reduced with an efficient and economical technique.

Description

technical field [0001] The invention belongs to the technical field of oilfield gas recovery and separation, and in particular relates to a recovery method of oilfield associated gas. Background technique [0002] The traditional oilfield gas recovery method uses the high-pressure expansion refrigeration process or DHX process. [0003] In the high-pressure expansion refrigeration process, the raw material gas is high pressure (about 60 bar), and the Joule Thomson throttling effect in the expansion process is used to generate low temperature, and the C in the raw gas is condensed. 3 、C 4 Equal weight components. The DHX process adopts the propane ice machine to pre-cool and the expander to further refrigerate, and the deethanizer adopts the DHX process to further recover the C in the lean gas 3 、C 4 components. [0004] For the raw material gas pressure is about 20barg, C in the raw gas 3 +C 4 The content is about 19% (vt), the delivery pressure of lean gas is about 2...

AI Technical Summary

Problems solved by technology

If the DHX process is adopted, due to the C in the feed gas 3 If the content is higher than 11% (vt), too much heavy hydrocarbon will cause the temperature of the top of the deethanizer to be too high, which will destroy the DHX process, and the advantage of the DHX process is not obvious

Moreover, the LPG recovery rate of the high-pressure expansion refrigeration process and the DHX process is not high, generally only about 80-90%

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