Extreme Sour Gas Compression

40+% H2S

15 High-Spec Compression Packages

A top ten global petroleum producer came to Startec with a major technical challenge. The company was experiencing significant performance issues with screw compressors it had acquired from another vendor. The compressors, being used to transport sour gas in the Alberta foothills, were prone to frequent breakdowns. The equipment could not handle the gas composition of 40+% H2S with variable quantities of water and condensates.

Production & HSE Factors

Reliability problems were disrupting production and exposing the company to an elevated and unnecessary level of HSE risk - the compression facilities are located in an environmentally sensitive area, relatively close to populated areas.

Startec Asked to Develop a Solution

The field and pipeline pressures were well suited to screw compressor capabilities, so the company turned to Startec to develop a package that could handle the highly corrosive H2S - H20 combination.

The Industry's Highest Rated Compressor

In developing a solution, Startec engineers worked closely with the client's research & specification division and Howden Compressors Ltd., the manufacturer of the industry's highest rated screw compressors for corrosive fluids (based on American Petroleum Institute specifications).

In assessing components, Startec engineers identified substantial differences between the Howden compressor and the failed field units. The bearing material and seal design on the Howden equipment were far superior. The technical review concluded the Howden components could withstand the corrosive properties of the gas and provide reliable operation.

Stringent Component Requirements

In addition to the compressor assessment, Startec engineers developed stringent specifications for the design, material selection and fabrication of pressure vessels, piping and all other components. Specialized lubricants were also specified, along with a sophisticated control and monitoring system.

Sour Gas Specification Adopted

After thorough review and consultation with Startec, the client's research and specification division adopted the sour gas compression package specifications.

Since that time, the client has commissioned Startec to design, manufacture and deliver multiple compression packages based on these exacting standards.

15 Compressor Packages in Use

Today, 15 of these high-spec compression packages are providing the client with safe, reliable service in the Alberta foothills.

This project demonstrates Startec's proven capabilities in:

• Engineering reliable compression solutions for highly corrosive gas production
• Developing custom compression packages to meet exacting client requirements
• Fabricating components to be compliant with stringent NACE specifications
• Proactively managing condensation issues - this capability is drawn from our industry-leading expertise in dewpoint control / propane refrigeration
• Mitigating HSE (Health, Safety & Environment) issues through advanced engineering

Equipment

• 800 HP Howden WRVi series screw compressor
• Electric motor drive
• NACE-compliant, custom-fabricated pressure vessel and piping components

Engineering & Design Factors

• Extra safety measures required due to high H2S levels, adjacent population and environmental sensitivity
• The corrosive H2S - H20 combination required specialized materials, lubricants and compressor design

Material Selection

• Project required corrosion resistant, NACE-compliant materials
• Startec sourced specialized steel plate for fabrication of all pressure vessels

Fabrication

• Startec employed specialized fabrication techniques to mitigate potential material corrosion, stress and cracking
• All weld joints in pressure vessel and piping components were subjected to appropriate post weld heat treatment (PWHT) to achieve NACE-specified hardness values. The heating, cooling and soaking process was tightly controlled to achieve optimum joint integrity.

Testing

• Entire fabrication process constantly monitored by Startec's Quality Control program (ISO 9001:2000)
• Integrity of all pressure vessel heads and shells verified by HIC (Hydrogen Induced Cracking) testing
• All welds verified according to Startec and client testing procedures, including 100% X-ray and PWHT

Operational Issues

• Startec reviewed suction and discharge pressures, compressor operating temperature and gas composition to form recommendations for specialized compressor lubricants and operating parameters

Contact Startec

To discuss the specifications of your gas compression projects, contact a Startec Oil & Gas Customer Representative at 403.295-5855 or toll free at 1-800-555-9439