Experimental and numerical studies for determining the mode I critical stress intensity factor using thick-walled hollow
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ORIGINAL PAPER
Experimental and numerical studies for determining the mode I critical stress intensity factor using thick-walled hollow cylindrical marly specimens Houtan Sodeifi & Mehdi Hosseini
Received: 1 September 2014 / Accepted: 5 January 2015 # Saudi Society for Geosciences 2015
Abstract In the oil industry, hydraulic fracture is used for enhancing oil recovery in the case where the recovery yield has reduced due to long-term extraction or when the rocks around the oil well have low permeability. Since the notches are opened in tensile mode in the hydraulic fracture operation, only the mode I critical stress intensity factor (critical SIF) was investigated. The aim of the present study was to examine the effect of three important parameters including the notch length and width and confining pressure on the mode I critical SIF using a thick-walled hollow cylindrical marly specimen. The oil well environment was simulated in the laboratory. The marly specimen was prepared from the Bangestan Formation in southern and southwestern Iran. To perform the tests, two artificial symmetrical notches with certain dimensions were created in specimens with an outer diameter (OD) of 73 mm, an inner diameter (ID) of 25 mm, and a height of 150 mm. A triaxial stress was applied on the specimen and the pressure required for the propagation of the artificial notches was measured. Three tests were conducted to investigate the effect of each parameter on the mode I critical SIF. The experimental critical SIF was compared with the average critical SIF obtained from ABAQUS and ANSYS. It was found that the mode I critical SIF decreased with increasing in the notch width and increased with increasing in the notch length. The critical SIF nonlinearly increased with increasing in confining pressure.
H. Sodeifi : M. Hosseini (*) Department of Mining Engineering, Imam Khomeini International University, Qazvin, Iran e-mail: [email protected] H. Sodeifi e-mail: [email protected]
Keywords Critical SIF . Mode I . Hollow cylinder . Marl rock . Notch length . Notch width . Confining pressure . ABAQUS . ANSYS
Introduction Rock fracture mechanics deals with the investigation of initiation and propagation of cracks in geological materials with fields of applications such as hydraulic fracturing, rock slope analysis, earthquake mechanics, blasting and rock fragmentation, and in many other practical problems in earth sciences (Tutluoglu and Keles 2011). In oil industry, hydraulic fracturing is used for enhancing oil recovery in the case where the recovery yield has reduced due to long-term extraction or when the rocks around the oil well have low permeability. The hydraulic fracture involves the creation and development of notches. Depending on the structure geometry loading, there are three notch displacement modes including the mode I or opening mode where the notch displacement is perpendicular to the notch front, mode II or shear mode where notch dimensions are displaced in the notch plane, and the mode III or tear mode where th
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