Pulse-Testing Response for Unequal Pulse and Shut-In Periods (includes associated papers 14253, 19365, 20792, 21608, 23476 and 23840 )
- M. Kamal (Amoco Production Co.) | W.E. Brigham (Stanford U.)
- Document ID
- Society of Petroleum Engineers
- Society of Petroleum Engineers Journal
- Publication Date
- October 1975
- Document Type
- Journal Paper
- 399 - 410
- 1975. Society of Petroleum Engineers
- 5.6.4 Drillstem/Well Testing, 5.1 Reservoir Characterisation, 5.6.1 Open hole/cased hole log analysis
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A theoretical study was carried out to develop the general equations relating-time lags and response amplitudes to the length of the pulse cycles and the pulse ratios of these cycles for pulse tests with unequal pulse and shut-in times. These variables were related to the reservoir parameters using appropriate dimensionless groups. The equations were developed by using the unsteady-state flow model of the line source for an infinite, homogeneous reservoir that contains a single-phase, slightly compressible fluid. A computer program was written to calculate the values of The three corresponding time lags and the response amplitudes at given dimensionless cycle periods and pulse ratios using these general equations.
For different values of the pulse ratio ranging from a 0.1 to 0.9, the time lags and response amplitudes were calculated for dimensionless cycle periods ranging from 0.44 to 7.04. This range of cycle period and pulse ratio covers all practical ranges over which pulse testing can be used effectively. Curves relating the dimensionless time lag to the dimensionless cycle period and the dimensionless response amplitude were constructed JOT each case. It was also found that both the dimensionless cycle period and the dimensionless response amplitude can be represented as simple exponential junctions of the dimensionless time lag. The coefficients of these relations are functions only of the pulse ratio.
Two wells are used to run a pulse test. These two wells are termed the pulsing well and the responding well. A series of flow disturbances is generated at the pulsing well and the pressure response is recorded at the responding well. Usually, alternate periods of flow and shut in (or injection and shut in) are used to generate the flow disturbances at the pulsing well. The pressure response is recorded using a highly sensitive differential pressure gauge.
Pulse testing has received considerable attention because of be advantages A has over the conventional interference tests. The pressure response from a pulse test can be easily detected from unknown trends in reservoir pressure. Pulse test values are more sensitive to between-well formation properties; thus, a detailed reservoir description can be obtained from pulse testing.
In all the work that has been reported on pulse testing, it was assumed that the flow disturbances at the pulsing well were generated by alternate periods of flow and shut in or injection and shut in. The pulsing period and shut-in period were always equal. There bas been no study of pulse testing with unequal pulse and shut-in periods. Such a study might have indicated whether other pulse ratios will produce higher response amplitudes than the equal-period tests. The main purpose of this study is to determine the response of pulse testing to unequal pulse and shut-in periods and to find the optimum pulse ratio that gives the maximum response amplitude.
Fig. 1 shows the pulse-test terminology as used in this paper.
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