The first project of the company ENERGAS in the field of gathering and transportation of associated gas was 10 years old!

2 January 2019

In December 2008, a compressor station of low separation stages (CSLS) began its work at the CPF (Central Production Facility) of Alekhinskoye field of the Nizhnesortymskneft Oil and Gas Production Department. Thus, the next stage of implementation of the Program of measures for the use of associated petroleum gas of Surgutneftegas PJSC was completed.

The basis of CSLS consists of five compressor units (CU) of low pressure, supplied and commissioned by the company ENERGAS.

CUs with a capacity of 7,000 m3 / h perform final purification, compression of associated gas (from the end separation stage) and injection it into a transporting gas pipeline at pressure of 1.7 MPa.

This project was the first for ENERGAS in the field of gathering and transportation of associated gas.

There are several main issues that make low-pressure APG compression process complicated: need for additional associated gas purification; risk of condensate dropout inside the gas system; negative impact of very low inlet pressure close to the vacuum; changes of the gas composition; severe operating conditions.

Therefore, this technological task is solved by special projects – on the basis of a set of consistent engineering solutions.

In particular, the gas final purification at the compressor inlet is performed by a highly efficient two-stage filter-scrubber (with a system of automatic drainage) integrated in the process unit's block-module.

At the design stage, there were carried out a detailed analysis of the gas composition and calculations in special software that creates a theoretical model of the behavior of a gas under certain conditions (temperature and pressure). This made it possible to determine the optimal operating temperature parameters of oil and gas, for which compression processes runs out of the condensation zone.

In oil system of units are used special lubricants with higher viscosity and high resistance to saturation from the heavy hydrocarbons.

Suction line is equipped with quick-acting valves with electric actuators and spring failsafe closing devices, that allows to cut off the CU gas circuit from the gas inlet pipeline.

Compressor units were designed taking into account extreme operating conditions. Special alloys and anti-corrosion materials were used in the production. It was performed redundancy of some components and subassemblies of equipment.

CUs are housed in its own enclosures of arctic type; they are equipped with all necessary life support systems (heating, ventilation, and lighting) and safety systems (fire detection, gas detection, alarm, and fire fighting).

In May 2012, the compressor unit No.5 was put out of the CSLS. Since commissioning, the operating time of unit was 15,827 hours.

CU-5 was dismantled and moved for 450 km – to the Rogozhnikovskoye field to operate at the site of the gas compression and treatment facility (GCTF). The CU functional has not changed – pumping of associated gas with inlet pressure close to vacuum.

The goal of the project was to increase the reliability of the GCTF and technological processes. The task was solved by ENERGAS service engineers.

Until August 2016, the only source of low-pressure APG for the CSLS was Oil Processing and Pumping Shop. To collect and compress gas from other facilities, at the station there was implemented upgrade of compressor units.

The system of input gas pipelines was upgraded with the installation of additional switching valves and pressure sensors, as well as the automated control system of CU and ACS of upper level were improved.

After upgrade, the capacity of the CU is regulated by the suction line, and the gas is supplied from the pipeline with a higher pressure. The choice of the source of gas is performed by the operator of CU in the operator room of the compressor station on the monitor of the operator's WKS.

The project has been implemented by ServicENERGAS LLC (part of the companies group ENERGAS). Technical specialists carried out the following:
  • Development, supply and connection of new software;
  • Supervisory control over the implementation of upgrade and assembling;
  • Start-up and adjustment works;
  • Individual testing in operation mode.

The careful design, high-quality production and timely upgrade of the equipment allow the compressor station of low separation stages of the Alekhinskoye field to operate to this day with a high level of reliability and efficiency.

REFERENCE. Alekhinskoe oil field – one of the oldest, put into development in 1985. The uniqueness of the field lies in the fact that it has four oil-bearing formations, whereas in other developments it is usually one or two. The peak of production was in 1991, when raised almost 2 million tons of oil from the depths.

Nizhnesortymskneft OGPD – the most northern Oil and Gas Production Department of Surgutneftegas OJSC – was established in 1989. The peculiarities of the enterprise include oil production in difficult, unique conditions of the marshland. Today, OGPD is developing 18 fields, which is about one third of all Surgutneftegas fields. The main part of the reserves is low-permeability oil deposits.

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