"A formation's minimum in-situ stress is an important parameter to determine for hydraulic fracturing. While minimum in-situ stress, and its orientation, can be measured from triaxial tests on core, it is more common to measure it as closure stress, by performing pressure testing of wells in the field. Closure stress is considered equal to, or a good approximation of the minimum in-situ stress for most cases. The analytical methods applied to such pressure testing include the square root of time plot, G function plot and the G-dP/dG plot. These plots require the engineer to fit tangent lines to the data, and the intersection of the tangent lines defines closure stress. The answer obtained is somewhat subjective, and a range of values of closure stress may result depending on how the tangents are fitted to the data. In 1989, Lee and Haimson described a statistical method for determining closure stress in water wells. Their work demonstrated the application of a non-linear regression technique for determining an upper and lower bound for closure stress. This work applies the non-linear regression method to both a water well and a gas well, and compares closure stress found with a statistical analysis to the values determined from square root of time plots. Results from this analysis show that for a water well domain, there is close agreement between closure stress derived from the square root of time plot and the value determined from statistical analysis. A slightly larger difference occurs between these values in the gas well example, indicating that a statistical analysis of closure stress may be of greater significance in analyzing oil/gas wells"--Abstract, Page iii.
Samaranayake, V. A.
Britt, Larry K.
Flori, Ralph E.
Geosciences and Geological and Petroleum Engineering
M.S. in Petroleum Engineering
Missouri University of Science and Technology
xii, 114 pages
© 2013 Soumitra Bhaskar Nande, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Pressure -- Testing -- Mathematical models
Oil wells -- Hydraulic fracturing
Electronic OCLC #
Nande, Soumitra Bhaskar, "Comparison of square root of time approach and statistical approach to minimize subjectivity in the determination of minimum in-situ stress" (2013). Masters Theses. 7100.