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The next version of 3DEC, Version 5.2, is in the final stages of development and now available to pre-purchasers as a pre-release. The latest 3DEC software offers about 2x faster run time performance and even greater improvements to model set-up time. A powerful set of new features provides major enhancements, particularly for bonded block modeling and hydraulic fracturing. The following are some of the new capabilities that have been added to Version 5.2.
Improved Performance in 3DEC 5.2
3DEC Models Solutions
Contact calculations and fluid flow analysis have been sped-up through:
- algorithmic improvements, including more powerful cell space and contact detection logic, and
- multi-threaded calculations.
This enables 3DEC to utilize multi-core CPUs to cycle up to 2x faster for typical applications.
Faster Model Set-up
Six key operations necessary for constructing 3DEC models have been significantly improved to execute faster.
- Cutting blocks, including adding joint sets
- Unjoining blocks
- Deleting blocks
- Excavating blocks (not deleted, but assigned a NULL constitutive material model)
- Making blocks deformable (e.g., GENERATE)
- Application of external boundary conditions
Zoning algorithms have been improved for better quality zone generation. Detection of any negative zone volumes is automatic, with such zones being deleted. Rigid block analysis is also more numerically stable.
Fluid Flow in 3DEC
As well as flow through joints, 3DEC 5.2 is capable of simulating fluid flow through the blocks or the matrix (i.e., between the joints). It is assumed that the blocks represent a saturated, permeable solid, such as soil or fractured rock mass. The flow in the matrix is coupled to the flow in the joints such that fluid in the joints can flow into the surrounding matrix (i.e., leak-off). As with the joint flow, the matrix flow modeling may be done independently of the usual 3DEC mechanical calculations or, in order to capture the effects of fluid/solid interaction, it may be done in conjunction (i.e., coupled) with the mechanical modeling.
Several characteristics are provided with the fluid-flow capability.
Different zones may be assigned a different (isotropic) permeability.
Fluid pressure flux and impermeable boundary conditions may be prescribed.
Fluid sources (e.g., wells) may be applied as either point sources or line sources. These sources correspond to either a prescribed inflow or outflow of fluid, and may vary with time.
Any of the mechanical and thermal models may be used with the fluid-flow models. In coupled problems, the compressibility and thermal expansion of the saturated material are accounted for.
Proppant Simulation in 3DEC 5.2
Hydraulic fracturing is a technique, used in the oil and gas industry, to stimulate resource production. The fracturing treatment often involves the injection of proppant as a suspension in the fracturing fluid. After the end of injection, the fracture closes onto the proppant, and a conductive conduit is formed to allow the oil/gas/heated-water to flow productively.
The transport and placement of proppant within the fracture is usually modeled by representing the proppant and fracturing fluid as a mixture, and this is the approach taken by 3DEC 5.2. It is assumed that the proppant particles are small compared to the fracture opening, and the proppant in the mixture is given by its volumetric concentration.
The proppant logic (Detournay et al., 2016) takes into account fluid-mechanical coupling and several effects are represented, such as:
- pack-formation (when the concentration reaches a given value, the proppant forms a pack, leaving only the fracturing fluid to flow through).
- bridging (when the proppant stops if the fracture width is small enough, compared to the particle size).
- proppant convection (when density gradients cause fluid motion in the fluid loaded with proppant).
- settling (when there is a slip in velocity between slurry and proppant, caused by gravity).
- viscosity changes as a function of proppant concentration.