Abating field development risks through 3D engineering design and unmatched testing capabilities

By Flavio Tosi, Giovanni Saccardi, Gianni Iannuzzi and Gabriele Turini
Originally published in Offshore Magazine's May 2007 issue.

Enhanced Oil Recovery (EOR) methodologies are increasingly experiencing extreme challenges when it comes to handling gas streams characterized by high levels of contamination such as found in the Kashagan project. In order to mitigate the inherent risks to the greatest degree, the advanced engineering designs and technologies that are applied must be proven before their “entry” into operation. One example of how this is done is the Full Load Test, successfully performed by GE’s Oil & Gas business on the highest pressure re-injection train ever built. This is part of the risk abatement process being undertaken by AGIP KCO for the development of this giant oil field.

Two key elements of AGIP KCO’s risk abatement process are well served by the unique capabilities of the GE Oil & Gas business: the ability to supply highly engineered compression islands and offshore modules, and the ability to verify the performance of the compression trains via a Full Load Test. The synergy achieved between these two elements is key to allowing challenges such as the Kashagan field development to be undertaken, while simultaneously ensuring returns on investment and the highest EHS standards.

Engineering design requirements

At the core of the Kashagan EOR process, GE is supplying two ultra-high pressure, barge mounted sour gas re-injection trains. The barge contains a full compression island that includes a 32 MW compression train capable of 820 bar delivery pressure and whose materials and design can withstand the 33% H2S found in the gas stream.

Each re-injection barge is 95 m long, 16 m wide and 25 m high. It should be noted that these dimensions are limited by the need to navigate through Russian internal waterways. Furthermore, the configuration is also constrained by disassembly requirements dictated by lifting operations, weight distribution, safety, operability and maintainability. For all of these reasons, the layout of the topside equipment has been one of the toughest challenges within this already difficult project.

The barge weight is also a crucial factor within the risk abatement process. The weight of a barge at operating conditions can exceed 4500 tons. In the Kashagan project, the need to limit the height to 16 m during navigation and the weight to 4000 tons during lifting requires disassembly of part of the topside. In addition, the weight needs to be carefully distributed in order to make the barge seaworthy and to limit distortions during lifting and in the final operating configuration fixed to the supporting piles.

Safety considerations have also required the allotment of adequate space for escape routes, but at the same time, all heavy equipment had to be arranged within a limited space, making it necessary to work on multiple levels of the topside. Furthermore, despite the heavy use of remote control operation, physical accessibility has been provided for all instrumentation as well as for manual operation of valves, vents and drains.

The construction and maintenance of a 3D model was a key element in helping to achieve an acceptable compromise for all these targets. 3D reviews were held at different stages of the project to ensure that the overall objectives of safety, operability and maintainability were under control. Material management also aided by the 3D model was particularly important because of the long delivery time and the cost associated with the heavy wall, low alloy steel piping components.

Testing requirements

GE’s Oil & Gas business has extensive experience in high-pressure re-injection. Its Nuovo Pignone testing facility, located in Massa, Italy, was the first to conduct full power, full pressure, and full speed testing of discharge pressures of up to 11,800 psi (820 bar). The testing facilities were set up to replicate all the key features of the plant site conditions. The train used during testing consisted of an MS5002/D DLN gas turbine and gear box driving the BCL404/B + BCL304/C + BCL304/E centrifugal compressors.

The test loop for the Kashagan oil field development was very carefully managed during its design, erection and certification. Using a continuous monitoring system, the gas loop was kept under pressure for the entire test duration. Furthermore, all controls were implemented for remote operation in order to replicate the on-site conditions where a very high degree of unmanned operation is required.  Since the toxic nature of the process gas is such an issue in this project, the sealing of all equipment was monitored and verified through dedicated procedures. In fact, a patented ‘zero leakage’ monitoring system was developed to ensure the detection of even ppm leakages at the compressor casing and innercasing interfaces. Finally, the equations of state for this unique process gas that were used in the design stage were validated by the test, thus assuring compressor performance control and robustness of the dry gas seal design.

With the successful “Kashagan” Full Load Test, GE’s Oil & Gas business has demonstrated its ability to predict the compression train performance and to design full compression islands capable of handling these latest industry requirements. This test program allows our customers to confidently proceed with field development with the certainty that their main plant equipment will deliver the required performance, and that the plant design will perform as required under these most challenging environmental and process conditions.

For more information, please contact:

Stefano Terzi
stefano.terzi@ge.com