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Time-Dependent Initiation of Multiple Hydraulic Fractures in Rocks

Uwaifo, Efosa (2016) Time-Dependent Initiation of Multiple Hydraulic Fractures in Rocks. Master's Thesis, University of Pittsburgh. (Unpublished)

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The challenge of creating multiple hydraulic fractures in petroleum reservoirs is approached by experimentally observing the time-dependence of the hydraulic fracture initiation/breakdown under different cases of fluid penetration into the rock during fracture initiation, and confining stresses.

The objective is to validate the plane-strain models of breakdown pressure for sandstone and granite. A comparison of cases of no-fluid penetration by using a jacketed wellbore, partial fluid penetration using soybean oil and glycerin, and full penetration using water was performed and the pressures required to create instantaneous and delayed breakdown, in cases of zero, low and moderate confining stresses recorded. In each case, the relationship between pressure and time to failure is compared with theory.

Experimental results show strong agreement with theory in the form of a predictable exponential relationship between time to breakdown and the wellbore pressure. Furthermore, the results enable experimentally derived values of β, a parameter varying from 1-2 for zero and full fluid penetration, respectively. By comparing values for soybean oil, glycerin, and water the dependence of β on viscosity is readily observed. The importance of β is further highlighted by
the ability to achieve breakdown after 500 seconds with only 25% of the tensile strength of the rock when β=2.

In summary, the main contributions are: 1) The first experimental validation of the predictable exponential relationship between time to initiation/breakdown of hydraulic fractures with wellbore pressure, 2) Experimental quantification of the role of fluid penetration, providing one of the clearest validations of classical hydraulic fracture breakdown models, 3) The first experimental demonstration of the role of confining stress on delayed hydraulic fracture initiation/breakdown, validating theory in the case of finite fluid penetration and demonstrating the need for further modeling in the case of zero fluid penetration.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Uwaifo, Efosaecu6@pitt.eduECU6
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBunger, Andrew P.bunger@pitt.eduBUNGER
Committee MemberMorsi, Badie I.morsi@pitt.eduMORSI
Committee MemberJikich, Sinisha A.saj55@pitt.eduSAJ55
Date: 25 January 2016
Date Type: Publication
Defense Date: 11 November 2015
Approval Date: 25 January 2016
Submission Date: 21 November 2015
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 100
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Petroleum Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: delayed initiation, hydraulic fracturing, petroleum, plane-strain, fracture initiation, rock breakdown
Date Deposited: 25 Jan 2016 17:06
Last Modified: 15 Nov 2016 14:30


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