Flow assurance tools used by the top operators

With a R&D investment by operators such as Statoil, Shell, Total, ExxonMobil, ENI, Chevron, and ConocoPhillips of more than US $ 300 million over the last 35 years, the simulation software OLGA is today an indispensable reference tool in the flow assurance field.

“OLGA is a simulator that has gone through nearly 35 years of development,” said Dr Bin Hu, OLGA Product Champion at Schlumberger Information Solutions.

“Thanks to the industry support and an innovative company culture, OLGA has been able to dominate the market for years,” he added.

Oil and gas companies such as Statoil, Shell, Total, ExxonMobil, ENI, Chevron, ConocoPhillips and others have all been heavily investing in OLGA’s research and development - particularly in the area of fundamental multiphase flow modeling.

OLGA’s next generation 

The next step of OLGA development will be focused on flow model.

“Slug flow and stratified flow are the two main dominating flow patterns in the gas-oil-water system and gas-condensate system respectively. The current OLGA flow model sometimes does not give accurate enough answers in terms of slug size and frequency for the slug flow, as well as the holdup and pressure drop for the stratified flow in large diameter gas-condensate pipelines,” said Hu (Schlumberger).

“Now it is time for us to implement our innovation results from the research program of the last ten years. We have new modeling solutions for both slug flow and stratified flow that shall significantly increase simulation accuracy,” Hu added.

“Particularly for the stratified flow, we are introducing a high-definition model that gives users improved predictions associated with a 3D flow description without suffering a serious penalty in execution time,” continued Hu.

Kongsberg’s LedaFlow

But the competition is fierce. Version 1.6 of the dynamic multiphase simulator LedaFlow - recently released by Kongsberg Oil & Gas Technologies - boasts improved features, like salinity analysis and wax and asphaltene prediction.

LedaFlow has beed developed since 2001 through the joint efforts of ConocoPhillips, Total and Norway’s SINTEF and IFE research centers. ConocoPhilips and Total have spent $3.17 million per year over ten years on LedaFlow’s R&D. The software latest update also benefits from the collaboration of industrial partners such as Petrobras, ENI and Shell.

LedaFlow was born to tackle the challenges of long-distance multiphase transport. Its development started out of the desire to generate a software with a strong focus on details in modelling and in spatial resolution, according to Kjell Arne Jacobsen, VP Research Oil&Gas Process Technology at SINTEF Materials & Chemistry.

SINTEF 

Based in Trondheim (Norway), SINTEF played a crucial role in the development of both OLGA and LedaFlow. OLGA was indeed jointly developed by SINTEF and IFE, and is now commercialized by SPT Group AS, purchased in 2012 by Schlumberger.

The largest independent research organisation in Scandinavia, SINTEF is a leading source of innovation in flow assurance solutions, conducting research on contract-basis for industrial clients.

“Our ambition is to have the best laboratory and the most qualified people in multiphase flow modelling in the world. We invested approximately 60 million NOK (about $ 7,600 ,000) in upgrading all the laboratory facilities six years ago. This goes into the knowledge base that we use in our industrial products later on”, said Jacobsen (SINTEF).

Fifty percent of SINTEF’s budget comes from the government, while the rest from the industry. Every year, oil companies such as Statoil, Shell and ConocoPhilips (which has now left the program) fund SINTEF’s competence building projects with approximately 2 million NOK (about $ 253,174) each, while CD-adapco, Vetco Grey, FMC and SPT Group invest about 500 thousand NOR (about $ 63,000) per year.

Detecting problems in multiphase transport through simulators 

Long distance multiphase transport – the transportation of oil, water and gas in the same pipeline - reduces the need of building offshore platforms. It allows leaving more operating personnel ashore, where it is cheaper, safer and more environmentally friendly to work than on board platforms.

Credit: SSSCCC

Multiphase transport has saved the petroleum industry huge financial outlays and made possible the development of oil and gas fields that would otherwise not have been profitable.

“Multiphase transport is widely used, for example for pipelines between wellhead and platform - or to shore - where the well stream is not one phase. As an example, more that 50% of the Norwegian oil production is from subsea wells,” said Andris Skattebo, Principal Flow Assurance Engineer at Future Subsea AS.

“Additionally, pipelines from platforms to shore are often multiphase, such as Troll, Kvitebjørn and Goldeneye in the North Sea. The primary development area is stretching the limits for tie-back distances,” he added.

For multiphase transport to work, it is essential to detect as soon as possible common problems such as corrosion and the formation of hydrates through computer programs that simulate the simultaneous flow of gas, oil and water through the same pipelines.

“Definitely, OLGA is the only simulator that can model both the sand suspension load and bed load under transient multiphase flow,” Hu (Schlumberger) said.

“There is no ready-made sand transport model in the open literature for gas-oil-water system, particularly under transient flow conditions. But we manage to borrow several correlations here and there, and assemble them together according to the OLGA flow modelling framework in an innovative way, which solves the challenge,” Hu added.

Flow assurance, drilling and performance engineers use OLGA

According to Hu, another innovation in OLGA2014 is its new capability of modelling flow dynamics in the drilling process using the moving grid method. This means that drilling engineers can now share the OLGA flow model with flow assurance engineers to address drilling hydraulics, well control issues, and hydrating risks under the gas kick.

But drilling engineers are not the only group of people who share OLGA’s simulation engine with flow assurance engineers. Several years ago well performance engineers made big progress optimizing the dynamic well operations, thanks to innovations on OLGA dynamic well modelling, according to Hu (Schlumberger).

“For example, well performance optimization engineers in BP have used OLGA to optimize the well start-up operation of low pressure offshore wells. According to BP, managing the dynamic transients in the well start-up can make the difference between a successful and an unsuccessful attempt,” said Hu, quoting a paper from BP.

“Using OLGA simulation to optimize the well bean-up procedure has been confirmed effective to bring more low pressure wells back to production. Only in 2011, the annualized production incremental for BP already reached 17.5 mBPD through dynamic modelling and slug control,” Hu added, referring to the paper.

Enhancing reliability of software solutions

The accuracy and reliability of software solutions can be further improved by both refining the models in the software programs and by obtaining more and better data to improve the tuning of the models, according to Skattebo, at Future Subsea AS.

“It is extremely difficult to collect field data with a quality sufficiently good to develop flow models, so in general field data can only be used to verify the models. Also the uncertainties in the input to the flow models are often larger than the uncertainty in the model itself. Thus, proper sensitivity and uncertainty analysis is important to understand the total uncertainty picture,” Skattebo added.

As Adegboyega Ehinmowo, Flow Assurance Researcher at the School of Engineering, Cranfield University, said “Code developers are not resting. There are various efforts between academia and the industry to develop more robust solutions. A continuous collaboration between the industry and the academia must be sustained to keep the improvement of the codes going”.