Online de-sander optimizes separator performance

Operators must meet growing global demand for oil and gas. While there are regions still rich in new reserves, it is both expensive and time-consuming to drill new wells. And in new areas, investing in collection and distribution infrastructure to support further development is required. When these considerations are combined with environmental factors and sensitivities, there is significant justification for operators to optimize production from mature assets to extract remaining reserves.

Sand production is becoming a factor, especially as older wells reduce yield. In new wells, sand production is a challenge where reservoir properties dictate a need for inclusion of sand screens and proppant in the well completion. These issues often can lead to carry-over of solids from reservoir to well bore.

Downtime reduction
Presence of sand in production vessels not only reduces capacity, but also affects separation performance, leading to deteriorating produced water quality and water carry-over in the oil phase. Without control, it can lead to a vessel being taken offline for manual cleanout. If not controlled, sand can cause major flow assurance problems impacting accumulation, fluidization, transportation, cleaning, and disposal. Even after sand is extracted, operators face storage issues since material cannot be deposited overboard due to environmental issues of oil on sand.

RBG’s third-generation online de-sanding system is modularized for easy installation. (Images courtesy of RBG)

Conventional sand management techniques require operations to shut down for 10 to 14 days, causing an expensive impact on the production schedule. A sand management solution that can remove sand from online production vessels, negating the need for a shutdown, and cleaning sand according to environmental regulations to be disposed overboard safely, is important to operators.

Technology developments promise a solution
RBG’s third-generation online de-sander system can eliminate the need for shut-in or production shutdown, providing efficiency, integrity, improved safety, and cost-effective operations over traditional vessel entry cleanout methods. This system can reduce the level of contamination in material removed from the production process, allowing it to be disposed overboard, providing a cost-effective and environmentally compliant solution to operators experiencing sand production problems.

While many separator vessels have built-in de-sanding systems, they are prone to blocking, which is expensive to retrofit and requires the vessel to be taken offline in the event of failure. RBG’s online de-sanding system can be deployed easily by connecting to existing drain connections, removing accumulated material, extracting oil from sand, and allowing recovered oil to be returned to the process via the platform’s hazardous drainage system.
It is designed to change the profile of shutdown and outage campaigns, enabling operators to achieve more uptime from mature assets and fields while reducing costs.

Oil-contaminated sand before cleaning causes various problems for operators.

The previously developed advanced online de-sanding unit featured safe and accurate deployment of jetting heads into vessels while collecting recovered material into drill skips. Although the process worked, the ability to clean recovered sand for overboard discharge was limited.
RBG has designed and manufactured a wash system to better treat produced solids for overboard discharge. Small, International Standards Organization-framed containers were developed that comprise a wash tank, high-flow centrifugal pump, and inbuilt access operating from a single 63A electrical socket.

Wash tanks now have become an integrated part of the new sand management portfolio. As material is recovered, it now can be washed, checked, and quantified prior to discharge.

These enhancements mean the company’s online de-sanding system can provide a complete sand management solution. A modular approach was taken in the design of the third-generation system, where the existing wash tanks can be used with a separation package fitted in line to pre-condition the slurry stream. This included development of a new coarse spin filter on the inlet to allow sand bursts to be addressed at startup, reducing blockage potential.
New solids extraction rams also were developed with rotational drive to improve deployment and recovery within production separators. Fluidization of the solids phase was improved, and deployment was eased through connecting drain pipework with bends, which minimized required costly pipework modifications.

A system of controls and process interlocks was developed to ensure equipment operations posed minimum risk to both the operations installation and teams.

A sand sample is cleaned and ready for overboard disposal.

Lower cost, added value
The third-generation online de-sanding system comprises several integrated components, including a solids extraction package, solids separation package, solids conditioning package, and hi-flow jetting unit with a recovered liquid package. The system is atmosphere-explosible compliant and can be used in Zone two hazardous offshore environments.

The system also can clean sand removed from the production process to less than 1% oil-on-sand content.

Portability of the system can allow sand production problems to be resolved cost-effectively since special hardware does not need to be designed or manufactured and shutdown is not required for installation. The package is connected via existing separator drain valves, causing minimal effect on existing infrastructure. With accumulated solids removed, separator performance efficiency is enhanced, and throughput can be increased.

Recovered material is subsequently removed and treated in situ without requiring onshore transportation or storage reinjection. The portable analysis kit allows treated sand to be tested onboard in real time, after which it can be disposed of overboard where environmental regulations allow.

Combination of these factors can cut costs and add value for the operator as production can continue, and impact on schedules is minimal.

Field-proven technology
Success of the online de-sanding system was demonstrated in a recent project for a major operator offshore Angola. The scope of the project required removal of an estimated 200 tons of sand from six “live” production vessels to interim containment skips, ready for washing and subsequent discharge.

An additional 627 tons of sand were removed from live separators, avoiding need for shutdown to clean vessels. Sand was washed to below 1% oil on sand, in line with Angolan operating requirements, with an average of 0.4% oil on sand.

System efficiency allowed the operator to maintain production at rates of approximately 140,000 b/d while de-sanding and sand washing took place. Following this successful project, the company secured a further work scope to clear blocked sand jets and sand blocked lines.

New approach
The system also has changed the way operators approach shutdown periods. As the system enables a high degree of specialist cleaning to take place prior to shutdown, a smaller team with high technical expertise can be deployed during the actual shutdown phase. This approach alters the resource profile required, positively impacting overall shutdown and outage planning management.