Pulse-Testing Response for Unequal Pulse and Shut-In Periods (includes associated papers 14253, 19365, 20792, 21608, 23476 and 23840 )
Authors: Kamal M. , Brigham W.E. 
Published: December 2007

A theoretical study was carried out to developthe general equations relating-time lags and responseamplitudes to the length of the pulse cycles andthe pulse ratios of these cycles for pulse testswith unequal pulse and shut-in times. Thesevariables were related to the reservoir parameters using appropriate dimensionless groups. Theequations were developed by using the unsteady-stateflow model of the line source for an infinite, homogeneous reservoir that contains a single-phase, slightly compressible fluid. A computer programwas written to calculate the values of The three corresponding time lags and the response amplitudesat given dimensionless cycle periods and pulseratios using these general equations.

For different values of the pulse ratio rangingfrom a 0.1 to 0.9, the time lags and responseamplitudes were calculated for dimensionless cycleperiods ranging from 0.44 to 7.04. This range ofcycle period and pulse ratio covers all practicalranges over which pulse testing can be usedeffectively. Curves relating the dimensionless timelag to the dimensionless cycle period and thedimensionless response amplitude were constructed JOT each case. It was also found that both thedimensionless cycle period and the dimensionlessresponse amplitude can be represented as simple exponential junctions of the dimensionless timelag. The coefficients of these relations are functionsonly of the pulse ratio.

Introduction

Two wells are used to run a pulse test.These two wells are termed the pulsing well and theresponding well. A series of flow disturbances isgenerated at the pulsing well and the pressureresponse is recorded at the responding well.Usually, alternate periods of flow and shut in (or injection and shut in) are used to generate the flowdisturbances at the pulsing well. The pressureresponse is recorded using a highly sensitive differential pressure gauge.

Pulse testing has received considerable attentionbecause of be advantages A has over theconventional interference tests. The pressureresponse from a pulse test can be easily detectedfrom unknown trends in reservoir pressure. Pulsetest values are more sensitive to between-wellformation properties; thus, a detailed reservoirdescription can be obtained from pulse testing.

In all the work that has been reported on pulsetesting, it was assumed that the flow disturbancesat 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 alwaysequal. There bas been no study of pulse testing with unequal pulse and shut-in periods. Such a studymight have indicated whether other pulse ratioswill produce higher response amplitudes than theequal-period tests. The main purpose of this studyis to determine the response of pulse testing tounequal pulse and shut-in periods and to find theoptimum pulse ratio that gives the maximum responseamplitude.

PULSE-TEST TERMINOLOGY

Fig. 1 shows the pulse-test terminology as usedin this paper.

SPEJ

P. 399^