Hello:

I am modelling for 2D hydraulic fracturing in Abaqus Standard, and adding proppant transport simulation to the this as well.

I have three steps to my model.

• Geostatic
• Step2 (where I inject the pad volume)
• Step3 (where I inject the fluid with the proppants mixed in the fluid)

But for now, to keep things simple, I am not injecting proppants at the beginning of step3, just the pad volume. In other words, Step 3 is nothing but a continuation of step 2!!!

I have a question regarding the output variable, gfvr (gap flow volume rate).

• What are the units for this gfvr variable? Is it m3/s or m2/s when the model is 2D?
• If I am injecting at a node at a flowrate of, say 3e-7 m3/s, shouldn't the value of gfvr be the same as the value of injection rate at the node where the fluid is injected? But the value of gfvr, at the injection node, is usually at least 1000 to 6000 times higher than the injection rate!!! Why is this the case?
• It is noticed in my model that, as soon as there is slight fracture propagation, there seems to be a steep increase in the gfvr at the injection node. But this increase in gfvr is the steepest right before the crack tip as the crack tip is about to expand. I have attched the figure. Can someone explain to me why this is the case?

If you could answer these questions regarding gfvr, that would e great!

Thank you very much.