Russia: Rosneft Associated Gas Recovery

Associated petroleum gas (APG) is a by-product of oil extraction. It is a mixture of volatile hydrocarbons – methane, ethane, propane and butane. It also contains light liquid-phase hydrocarbons, mainly, pentane and hexane. APG may be dissolved in underground oil reservoir, or accumulate in the upper layer of oil-bearing bed, forming a gas cap.

One of the main ways of useful utilization of APG is its separation into several commercial products; broad fraction of light hydrocarbons (BFLH), dry gas, which predominantly consists of methane and casinghead gasoline – a mixture of heavier hydrocarbons, also known as condensate. Component composition of dry gas is similar to that of natural gas. Dry gas is similar to natural gas by its composition and used domestically as fuel for power plants and energy source in residential sector and industry. Dry gas is also exported abroad. Casinghead gasoline is either used directly as motor fuel or processed further. The BFLH is refined into ethane fraction and propane-butane fraction. Also, BFLH is used in petrochemical industry as the primary source of raw materials for production of liquified propane-butane and high-octane petrol fractions.

The purpose of this joint implementation project has been useful utilization of the associated petroleum gas at the production sites of Kharampur group of oil filed of Rosneft company, operated by its subsidiary, RN-Purneftegas Lt. This group of oil fileds includes North Kharampur, Sputh Kharampur and Festival oil fields. Oil production at Kaharampur group of oil fields began in 1990. These oil fields have high gas-oil ratior. Large volumes (about 1 billion cubic meters per year) of associated petroleum gas are historically flared and up to now. According to the subsoil use license, RN-Purneftegas has never been obligated to utilize any specified fraction of this gas. Actually, environmental permits officially sanction the gas flaring.

The project has included the existing booster pump stations with water discharge and preliminary water discharge units: All facilities have been equipped with high- and low-pressure flares. A small portion of APG has been used for own needs of the facilities, while the remaining gas has been flared. Nine of ten flares emit soot during APG flaring, because they operate under “carbon-black flaring” conditions, which are characterized by noticeable underfiring of methane.

Project activities have included:

• Recovery and delivery to the booster compressor station the high-pressure associated petroleum gas under its own pressure and preliminary compressed low-pressure APG from the existing BPS Festival, BPS-1 South Kharampur, PWDU-2 South Kharampur, BPS-2 North Kharampur and PWDU north Kharampur.
• Low temperature condensation of APG and its separation into the following commercial products: dry gas fraction, compliant to industry standard OST 51.40-93, and BFLH fraction.
• Transportation of commercial BFLH through a multiphase pumping station to Tarasovskoe oil field where the product is shipped to consumers.
• Injection of commercial dry gas through the injection wells into the temporary underground gas storage at Cenomanian gas deposit of Kharampur gas condensate field.