Effect of Formation Modulus Contrast on Hydraulic Fracture Height Containment

Abstract

Abstract Much study has been conducted on the effects of formation Young's modulus and in situ stress on hydraulic fracture height containment in layered formations. It has been well documented that in situ stress contrast is the dominant parameter controlling fracture height growth and that Young's modulus contrast is less important. However, a recent study pointed out that modulus contrast can have significant implications on fracture geometry and proppant placement.1 To expand on this topic further, we consider the combined effects of modulus contrast and in situ stress contrast on fracture geometry. A pseudo 3D (P3D) hydraulic fracture simulator with a rigorous layered modulus formulation is used in this study. The fracture height calculated based on uniform modulus versus layered modulus, under the same in situ stress contrast conditions, is compared. The results are analyzed and explained, based on fracture mechanics fundamentals as well as the coupled fluid pressure effect in hydraulic fracturing. One important finding is that fracture height can also be contained by low modulus layers. The results from this study can be applied to hydraulic fracturing treatments in formations with moderate to significant modulus contrast. The mechanisms studied in this work could also partially explain some recent results from microseismic or tiltmeter mapping that show more fracture height containment than that predicted by commonly used P3D hydraulic fracturing simulators based on averaged modulus.