Title: Fracture-initiation pressure analysis of horizontal well in anisotropic formations

Authors: Tianshou Ma; Yang Liu; Ping Chen; Bisheng Wu

Addresses: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan, 610500, China ' State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan, 610500, China ' State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan, 610500, China ' CSIRO Energy, Melbourne, VIC 3168, Australia

Abstract: Lost circulation is a classic wellbore instability problem encountered during drilling. To minimise or avoid lost circulation, preventing the initiation of fracture is the best measure. However, because rocks are naturally anisotropic, the classic fracture pressure model is not applicable for anisotropic formations. Some researchers therefore investigated the influence of transverse isotropic material parameters, but they ignored the influence of anisotropic tensile strength. The present work proposes a novel fracture-initiation pressure model of a horizontal well to investigate the influence of anisotropy on fracture-initiation pressure. Laboratory hydraulic fracturing testing verified the present method. The results indicated that anisotropic modulus and tensile strength have distinct influences on fracture-initiation pressure. Fracture-initiation pressure declines obviously under the influence of anisotropic modulus and anisotropic tensile strength, thus, the anisotropy of modulus and tensile strength cannot be ignored. The present model provides more accurate predictions of fracture-initiation pressure for horizontal wells in anisotropic formations. [Received: July 26, 2017; Accepted: December 19, 2017]

Keywords: lost circulation; fracture-initiation pressure; fracture pressure; horizontal well; anisotropic formation; anisotropic tensile strength.

DOI: 10.1504/IJOGCT.2019.103508

International Journal of Oil, Gas and Coal Technology, 2019 Vol.22 No.4, pp.447 - 469

Received: 26 Jul 2017
Accepted: 19 Dec 2017
Published online: 08 Nov 2019 *

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