TY - JOUR
T1 - A study of the effect of brittleness on hydraulic fracture complexity using a flow-coupled discrete element method
AU - Shimizu, Hiroyuki
AU - Ito, Takatoshi
AU - Tamagawa, Tetsuya
AU - Tezuka, Kazuhiko
N1 - Publisher Copyright:
© 2017 Elsevier B.V.
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2018/1
Y1 - 2018/1
N2 - In recent years, hydraulic fracturing has emerged as an important technique for the development of unconventional tight gas and oil reservoirs, particularly shale reservoirs. Production from a tight reservoir requires hydraulic creation of a highly fractured network for significantly improving the hydraulic conductivity of the reservoir. Field observations have empirically indicated that fracture complexity tends to be higher in the case of higher rock brittleness which is defined as the combination of the Young's modulus and Poisson's ratio of a rock. The brittleness is considered as one of the most important mechanical rock properties of unconventional tight reservoirs. However, the physical relationship between fracture complexity and the brittleness remains unclear. In this study, a series of hydraulic fracturing simulations were performed using a flow-coupled discrete element method to gain insights into the effect of the brittleness on fracture propagation. The brittleness was adjusted under different combinations of Young's modulus and Poisson's ratio for four rock models. Considering mechanical rock properties and pre-existing fractures, the effective stress in the case of lower brittleness reduced to the tension only around the tip of the hydraulic and pre-existing fractures. On the contrary, the tensile region was more widely distributed along the pre-existing fracture in the case of higher brittleness. The effective tensile stress in a wider region should induce more microcracks, thereby enhancing the possibility of the hydraulic fracture branching off from the pre-existing fracture. These considerations indicate a positive correlation between the brittleness and the complexity of a hydraulically induced fracture system.
AB - In recent years, hydraulic fracturing has emerged as an important technique for the development of unconventional tight gas and oil reservoirs, particularly shale reservoirs. Production from a tight reservoir requires hydraulic creation of a highly fractured network for significantly improving the hydraulic conductivity of the reservoir. Field observations have empirically indicated that fracture complexity tends to be higher in the case of higher rock brittleness which is defined as the combination of the Young's modulus and Poisson's ratio of a rock. The brittleness is considered as one of the most important mechanical rock properties of unconventional tight reservoirs. However, the physical relationship between fracture complexity and the brittleness remains unclear. In this study, a series of hydraulic fracturing simulations were performed using a flow-coupled discrete element method to gain insights into the effect of the brittleness on fracture propagation. The brittleness was adjusted under different combinations of Young's modulus and Poisson's ratio for four rock models. Considering mechanical rock properties and pre-existing fractures, the effective stress in the case of lower brittleness reduced to the tension only around the tip of the hydraulic and pre-existing fractures. On the contrary, the tensile region was more widely distributed along the pre-existing fracture in the case of higher brittleness. The effective tensile stress in a wider region should induce more microcracks, thereby enhancing the possibility of the hydraulic fracture branching off from the pre-existing fracture. These considerations indicate a positive correlation between the brittleness and the complexity of a hydraulically induced fracture system.
KW - Brittleness
KW - Discrete element method
KW - Hydraulic fracturing
KW - Pre-existing fracture
KW - Tight reservoir
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U2 - 10.1016/j.petrol.2017.10.064
DO - 10.1016/j.petrol.2017.10.064
M3 - Article
AN - SCOPUS:85033587701
VL - 160
SP - 372
EP - 383
JO - Journal of Petroleum Science and Engineering
JF - Journal of Petroleum Science and Engineering
SN - 0920-4105
ER -