Recapturing lost profits

Jon Lawson

Modelling and simulation offers cost-saving for oil and gas industry during market downturn. Alex Read reports

The ‘lower-for-longer’ oil price is causing the global oil and gas industry to look for ways to recapture the lost profits caused by the market downturn. To withstand the current petroleum freefall, companies are increasingly turning to engineering simulation in an effort to remain viable and meet the challenges presented by plummeting crude prices.

Many industries have used simulation technology, such as computational fluid dynamics or CFD, to reduce engineering time and costs. Historically, the O&G industry has struggled to achieve this saving, due to the model creation time being too slow in legacy codes, and High Performance Compute (HPC) resources being too costly.

By streamlining the simulation process, and enabling HPC, CD-adapco is enabling O&G companies to use simulation to explore the design space to discover better designs, faster. In so doing, we’re helping customers reduce engineering costs and time, without compromising safety.

Areas where CFD adds value include equipment design, the understanding of operational questions, safety, and troubleshooting or upgrading equipment.

Used to evaluate design alternatives, simulation in equipment design can be found in anything from drill bits through Fluidised Catalytic Crackers (FCCs) in a refinery. Among the operational questions simulation can help engineers understand include how best to produce a given reservoir, how to manage a well shut-in so as to prevent solids forming and plugging pipelines or equipment, or minimising erosion damage.

Safety, meanwhile, is of paramount importance to everything the industry does. Simulation is used for scenario analysis (for example, what if a leak occurs in a given location) to ensure facilities are safe by design.

CD-adapco is playing a leading role in the oil and gas industry’s adoption of CFD simulation in its design processes. Engineering simulation is a valuable method for reducing equipment failure, improving product longevity and lowering operating costs. As such, products such as CD-adapco’s engineering solution STAR-CCM+ enables oil and gas engineers to significantly reduce turnaround times for CFD simulations and enable much greater influence on engineering decisions.

Slow turnaround times present challenges for one-off analyses; can the engineer deliver results with sufficient speed in order to influence the decision being made? Analysis teams have long dreamed of automating the simulation process and leveraging design space exploration software to find better designs, faster. The manual work required to set-up and run legacy codes meant processes took too long, or were not robust enough to achieve this goal. We have, and continue to help our customers who have struggled with model turnaround times to make significant improvements, enabling simulation as a driver of design decisions. This offers the best possible outcome for our customers in the form of potentially significant time and cost savings.

Simulation and modelling for offshore vesses

The oil and gas industry is increasingly operating deepwater projects. These are typically ‘tied back’ to a floating vessel, which will be a semi-submersible, Tension Leg Platform (TLP) or a ship-shaped Floating Production Storage and Offloading (FPSO) unit. These vessels, and the mooring lines and pipes that connect them, often encounter severe weather such as hurricanes, strong currents, abnormal waves and strong winds.

Under these conditions, using simple methods/potential flow and physical testing in the design process leaves too wide a window for uncertainty in the design. For example, potential flow codes do not account for viscous effects, or overturning/breaking waves; and wave basin tests are scaled by the Froude Number rather than the Reynolds number. This uncertainty leads to overdesign and significantly increases cost.

Pioneering work by companies such as Technip and SBM Offshore, supported by major oil and gas operators, have developed a Numerical Wave Basin (NWB) based around STAR-CCM+. This allows them to perform virtual experiments, which includes all the relevant physics, and to do so before physical testing occurs. This allows them to optimise the design, ensure projects are delivered on time and budget, without compromising safety.

NWB is a specific example of a solution that uses simulation to drive design. NWB is used to understand many design requirements, such as VIM response, global motion, ringing on TLPs or gravity-based structures, air gap, wave run-up and slam loads.

Simulation brings greater certainty to the modelling of vessels, significantly reducing the margin of error for any given project. For example, several years ago - before CFD was used - Chevron performed a comparison of the VIM estimated in their design process and behaviour of the platform in the field. The magnitude of motion was over-predicted by a factor of two, and the frequency of VIM events was also significantly over-predicted.

Chevron estimated that this additional ‘conservatism’ added millions of dollars of additional cost to the project in the riser and mooring line design. These additional costs came extremely close to making the project uneconomic. Considering this study was done a few years ago when oil prices were much higher, the economic situation would be much more dire today.

Of course, the biggest challenge in modelling vessels is the wide range of time and length scales of interest. For example, a design requirement for a floating platform is its behaviour during a storm. The typical design assumption is that these storms will last for three hours, which is a long time to run a CFD simulation. The challenge this presents is how to make the simulation computationally and financially tractable. CD-adapco is addressing these issues in two ways:

* By implementing techniques that significantly reduce the computational cost of the CFD simulation. Examples include Overset Mesh, which is a computationally efficient way of handling the motion of objects in CFD calculations, such as a vessel moving in rough seas.

* And enabling the use of High Performance Computing (HPC) and Cloud solutions. STAR-CCM+ possesses the ability to scale onto a large number of cores - in 2015 CD-adapco became the first commercial CFD code to run on over 100,000 cores. Increasing the core count significantly reduces compute times.

Budget-friendly cloud-based solutions

While large compute resources are now readily available through cloud compute providers, licensing can be a challenge: corporate IT groups are reluctant to open their networks, and software providers historically have penalised customers for short-term licenses. CD-adapco offers a Cloud-based, Power-On-Demand licensing option called PowerSession to give engineers a convenient pay-as-you-go model.

PowerSession licenses allow the user to run simulations on as many cores as they have access to on an hourly basis. The license can be accessed by any machine with an internet connection. This combination enables engineers to reduce model turnaround time by using the latest hardware resources in an affordable manner.

Alex Read is the Director, Oil & Gas, at CD-adapco