applications ➤
historical data with ongoing project metrics and predict the output of the next stage in a single model and platform.’
Fracking extraction Tere are many complicated phases involved to
safely and successfully extract oil and gas from the earth’s surface during fracking. Tese include: drilling a useable borehole, providing a conduit from the underground reservoir to the surface, managing the flow of fluids from the reservoir to the surface and the disposal of waste products, such as reinjecting untreatable fluids back into the earth’s surface. To accurately model this range of critical
factors, ExxonMobil used Dassault Systemes’ Simulia applications to develop a fully coupled formulation for hydraulic fracture growth using two advanced finite element methods. A cohesive zone method (CZM) was
developed, in which the fracture trajectory is confined to a plane, and an extended finite element method (XFEM) was also developed where the fracture trajectory is entirely solution dependent. Additional models were also implemented in the Abaqus application to account for the inelastic deformation seen in soſt rock. ExxonMobil then used Simulia, alongside
results from its in-house experimental capabilities, to create 2D and 3D models of many different aspects of controlled hydraulic fracturing in rocks. Tis has helped ExxonMobil manage and mitigate the risks associated with drilling into the earth’s surface. It has also helped ExxonMobil develop recovery schemes to make production more economical. Bruce Dale, chief subsurface engineer for ExxonMobil, said: ‘In the decades ahead, the world will need to expand energy supplies in a way that is safe, secure, affordable and environmentally responsible. 3D simulation powers innovative solutions by building on the fundamentals to deliver energy in the 21st century.’
Visualising sites As the ExxonMobil case study demonstrates, visualisation is an important tool in the geothermal sector as it allows engineers to understand, investigate and optimise inaccessible sites that are, potentially, tens of kilometres under the earth’s surface. Geophysical exploration company Dewhurst
Group specialises in on site selection to pinpoint geothermal sources for electric power generation. Te group conducts resistivity imaging surveys using broadband magnetotelluric (BMT) and low frequency magnetotelluric (LMT) instrumentation to image the earth’s subsurface landscape to understand the underlying tectonics that might drive a geothermal source .
14 SCIENTIFIC COMPUTING WORLD
Figure 1: A 3D image of subsurface resistivity at the Pueblo of Jemez. Red shows areas of low resistivity, often associated with geothermally altered cap rock or a concentration of geothermal brine. Target area shown at a depth of 1800m and “X” marks the spot to drill.
Te Dewhurst Group recently investigated
a site at Jemez, New Mexico. During the first stages of the exploration project, the group gathered information on the survey location, which involved collecting data from 150 stations over an area of approximately 37 km2 Te group then analysed and modelled
dangerous experiments to find and extract these much-needed resources. Te next stage is to provide further links with
.
these results using the Golden Soſtware Voxler application to generate 3D renderings of all the 1D, 2D and 3D inversion results. Tis collection of models were then integrated to generate a resistivity imaging model of earth’s subsurface, which is shown in Figure 1, of the Pueblo region of Jemez. Tese visualisation tools helped Dewhurst to locate an optimal drilling depth and target
MODELLING AND
SIMULATION PROVIDE A VITAL LINK TO INVESTIGATE GEOTHERMAL RESOURCES
location. Te resistivity results were later confirmed by subsequent exploration efforts, including a seismic survey. Blakelee Mills, CEO at Golden Soſtware, said: “Whether it’s mapping the geothermal area, graphing the estimated geothermal production, or modelling the subsurface area of interest, our tools facilitate a more thorough understanding of the data at hand.” Modelling and simulation provide a vital link
to investigate the geothermal resources that exist under the earth’s surface, without research teams carrying out expensive and, potentially,
the on site teams to bring these simulation and modelling processes where they are needed so engineers can make smart on-site decisions without the need to go back to the research scientists. For example, simulation apps can be built by
modelling experts with Comsol Multiphysics and deployed with a local installation of Comsol Server, which can be accessed via a web browser. Te engineers in the field can then connect and run apps to make decisions based on simulation results. ‘Integration of the numerical simulation with field work is very promising and still requires more user-friendly tools to achieve, which will result in more smart self-adaptive tools for detecting and extracting energy resources,’ Cai added. Over the last few decades, the multiphysics
nature of the simulation and modelling soſtware has mirrored the multiphysics nature of geothermal detection and extraction to optimise these processes and keep the industry evolving. In a similar vein, the soſtware now needs to
evolve and match the needs of the geothermal energy sector from an accessibility perspective. To allow the continued detection and extraction of resources from the world’s most inaccessible regions, simulation and modelling must be accessible to all users, regardless of their level of expertise or physical location. In other words, the modernisation of
geothermal simulation tools is the next step to optimise this sector and ensure its ongoing success to meet the world’s ever-growing energy demands. l
@scwmagazine l
www.scientific-computing.com
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