TITLE:
A Reinterpretation of Historic Aquifer Tests of Two Hydraulically Fractured Wells by Application of Inverse Analysis, Derivative Analysis, and Diagnostic Plots
AUTHORS:
Patrick A. Hammond, Malcolm S. Field
KEYWORDS:
Aquifer-Test Analysis, Inverse Analysis, Derivative Analysis, Diagnostic Plots, Hydraulic Fracturing
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.6 No.5,
April
25,
2014
ABSTRACT: Aquifer
test methods have greatly improved in recent years with the advent of inverse
analysis, derivative analysis, and diagnostic plots. Updated analyses of past
aquifer tests allow for improved interpretations of the data to enhance the
knowledge and the predictive capabilities of the flow system. This work
thoroughly reanalyzes a series of pre- and post-hydraulic fracturing, single-well
aquifer tests conducted in two crystalline rock wells in New Hampshire as part
of an early 1970’s study. Previous analyses of the data had relied on older
manual type-curve methods for predicting the possible effects of hydraulic
fracturing. This work applies inverse analysis, derivative analysis, and
diagnostic plots to reanalyze the 1970’s aquifer test data. Our results
demonstrate that the aquifer tests were affected by changes in flow regimes,
dewatering of the aquifer and discrete fractures, and changes due to well
development. Increases in transmissivities are related to well development
prior to hydraulic fracturing, propagation of a single, vertical fracture
hydraulically connecting the two wells after stimulation and expansion of
troughs of depression. After hydraulic fracturing, the estimated total yield of
the individual wells increased by 2.5 times due to the hydraulic fracturing.
However, the wells may be receiving water from the same source, and well
interference may affect any significant increase in their combined yield. Our
analyses demonstrate the value in applying inverse analysis, derivative
analysis, and diagnostic plots over the conventional method of manual
type-curve analysis. In addition, our improvement in the aquifer test
interpretation of the 1970’s test data has implications for more reliable
estimates of sustained well yields.