Replacing annual shut-in well tests by analysis of regular injection data: Field-case feasibility study Page: 1 of 11
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Replacing annual shut-in well tests by analysis of
regular injection data: field-case feasibility study
Dmitry Silin', Chin-Fu Tsang', and Harlan Gerrish2
Regulations governing deep injection of industrial wastes for disposal require
regular tests for monitoring the formation hydraulic properties changes in the vicinity of
the wellbore. Such a monitoring is performed through transient pressure well testing, a
procedure that is routinely used in the environmental and oil industries. In such tests, the
pumping pressures and rates are recorded and analyzed to estimate the transmissivity and
storativity of the rock in the vicinity of the wellbore. Numerous methods for analyzing
such data have been developed since the pioneering paper by Theis (1935). The well test
analysis methods are summarized in several monographs, see, e.g., Earlougher (1977)
and Matthews (1967).
Traditional well test analysis methods are often based on estimating the slope of
the pressure fall-off curve in a special time scale, e.g., using the Horner plot method
(Horner, 1951). Such an approach is justified by asymptotic analysis of the pressure
change relative to a uniform initial pressure distribution. However, in reality, such an
initial condition may not hold true because the operations preceding the test make the
pressure distribution not uniform. It has been demonstrated in Silin and Tsang (2002,
2003) that in the Horner plot method, this circumstance partially explains the deviation of
the data points from the theoretically predicted straight line. A new method has been
proposed to analyze well test data accounting for the pre-test operations. This method
has been validated using synthetic and field well test data.
In this paper, we demonstrate how the method can be applied to analyze regular
pumping data from an injection field to estimate the formation's hydraulic properties
without interrupting the operations. In this estimation, we use the code ODA developed
at Berkeley Lab. This code implements the methods and algorithms developed by Silin
and Tsang (2002, 2003).
The paper is organized as follows. In the next section, we present a brief
overview of the method and describe the procedure used in the analysis. Then, in the
following section, we present the analysis of data from several injection wells. The
results of this analysis are summarized in our conclusions.
Description of the Method
The procedure we use in this study was designed to estimate formation hydraulic
properties from regular operations data. The recovered parameters include formation
transmissivity and storativity, skin factor, and an average reservoir pressure.
Additionally, the method estimates an effective pre-test pumping rate, which can be used
for aposteriori verification of the quality of fitting. We only briefly describe the method;
for details, see Silin and Tsang (2002, 2003).
1Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, CA 94720
2 U.S. Environmental Protection Agency, 77 West Jackson Street, Chicago, IL 60604
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Silin, Dmitry; Tsang, Chin-Fu & Gerrish, Harlan. Replacing annual shut-in well tests by analysis of regular injection data: Field-case feasibility study, article, May 21, 2003; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc739823/m1/1/: accessed December 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.