Effect of Formation Modulus Contrast on Hydraulic Fracture Height Containment

Abstract

Summary Much study has been conducted on the effect 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 (Smith et al. 2001). To expand on this topic, 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 vs. 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 low-modulus layers can also contain fracture height. 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 can 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.