Q: What relationship is there between frac growth and well spacing?
A: “Most of the companies we work with are developing multi pay zones,” Kyle LaMotta, VP of Analytics explains. "The traditional thought is to establish what the well spacing is and geometrically space all the wells the same. But the stress is varying with depth so in one zone the fracs might go up more than in another zone where they might go out more. In that situation you’d want to consider different well spacings for different targets.
“Here’s an example of a well that’s staying mostly in zone. But then in the bench above, the frac grows up more. It’s growing out more in one bench than the other. Potentially you could put the upper bench wells closer together and the lower bench wells further apart.
“Well spacing should not be considered just per DSU, it should be considered per well per bench.
“With the Petro.ai DSU Design service, we can run different combinations of well spacing in different zones. We can consider different numbers of wells that are spaced uniquely and appropriately for their specific benches. In shale, this important differentiator can significantly change the drainage and ultimate productivity of a DSU.”
Dr. Brendon Hall, VP of Geoscience with Petro.ai, deals with this question for almost all our Petro.ai clients. "This is the fundamental question behind our Drilling Spacing Unit Design Service (DSUDS) and why we’re so interested in geomechanics,” Hall begins. "The fundamental thesis is that the state of stress in the earth determines the direction the fracs propagate. They’ll move along the path of least resistance in terms of going in the direction of maximum horizontal stress. But the way the stress varies vertically will also determine whether these fracs grow up mostly, grow down potentially, or grow out.
“If you’re in a situation where the minimum horizontal stress is low, where the well has been drilled and it has high stress above and below then that frac may be blocked from propagating too far up or down and will grow out laterally. If you’re in a formation where this is the case, then that lateral growth will interfere with nearby wells that are placed there.
“So, you would expect that fracture growth really affects how closely you can space these wells. You may want to space them a little further apart in that scenario or a lot further apart depending on the situation.
“If the wells are drilled in a reasonably high stress region and the stress was low above where the wells are, those fracs may have an easier time propagating upward. All that fracture energy is going to go up and they won’t propagate outwards too much which would mean you could space those wells more tightly in that region.
“From the geomechanics perspective, that’s the mechanism that ties frac geometry to spacing. Knowing how wide the fracs go indicates how closely to space these wells. For the Petro.ai DSUDS analysis that comes from the frac fingerprint information and is incorporated into every analysis.”