Sludge management cancels H2S and HT risks in Kazakhstan

Kazakhstan, Asia, Onshore

Production ExPRESSTM rapid production response solutions enabled the operator to produce up to 450,000 bbl/d of oil and more than 300 MMcf/d of gas. Design, preparation, and startup were delivered in six months, helping the operator meet its production schedule.

Discovered in the year 2000 in the Caspian Sea offshore Kazakhstan, the Kashagan oil field ranks as one of the largest oil discoveries of the past four decades. Harsh weather conditions with temperatures varying from −35 to 40 degC and high concentrations of hydrogen sulfide (H2S) up to 19% make it one of the most challenging environments in the world.

As part of the Kashagan project, an onshore processing facility was built to process oil and gas coming from the region. In the plant’s commissioning phase, the operator faced a challenge with wells producing oily sludge, which could lead to a plant shutdown, delays in plant startup, or release of products containing unacceptable levels of H2S and acid.

Because of the facility’s location next to a major city, the operator could not consider draining the sludge manually and transporting it by public road unless the waste was treated properly and made environmentally safe for removal. The operator’s main requirement was to have an automated neutralization process that could treat the sludge continuously with minimal human contact, while making it transportable on public roads.

To meet the challenge, SLB proposed a facility commissioning service from its Production ExPRESS solutions portfolio. The solution involved a fully automated mobile package made from standard well testing equipment, which could handle the highly acidic, H2S-contaminated sludge reliably and effectively. The proposed solution would be kept in place for two years while the operator was sourcing and installing a permanent solution.

Three packages were created using an integrated intelligent remote-control system to minimize personnel exposure during the filling, dosing, circulation, and discharge of the waste sludge. The neutralization process involved multiple vessels, mixing the sludge with 25% to 45% caustic soda (depending on ambient temperature) and circulating it through the vessels. Once neutralized, the liquids were discharged to vacuum trucks for disposal.

Special modifications allowed efficient mixing of the treated sludge within the tank, which was internally coated with epoxy compound to protect against high pH and chloride effects. To avoid overfilling the vessels, a redundant level measurement system was introduced using electronic sensors and radio waves. Winterization of equipment with electrical heating cables and insulation was specially designed to meet hazardous area ATEX Zone 2 standards.

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Sludge treatment facility installed at the operator's onshore processing plant.

The implementation of a successful sludge management system was a vital part of the plant startup with capacity to process up to 450,000 bbl/d of oil and more than 300 MMcf/d of gas. The three packages worked together successfully to ensure that all sludge removal was done in a manner that minimized HSE exposure—to the site crew as well as to the local environment and population.

Design, preparation, delivery, and startup of the project took six months, enabling the operator to meet its production schedule. The agile approach used by Production ExPRESS solutions, which involved modification of existing equipment, allowed the operator to save significant capex by avoiding procurement and installation of new equipment with a high cost and long lead time. As part of the solutions delivery, operations personnel were trained to run the unit autonomously.

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