An Emperical Method To Correct Pulse-Test Results For Wellbore Storage At The Pulsing Well

1979 ◽  
Author(s):  
Julius J. Mondragon ◽  
Donald E. Menzie
Keyword(s):  
Test Results ◽  
Pulse Test ◽  
Wellbore Storage

A Method To Account for Afterflow at the Pulsing Well During Pulse Tests

1983 ◽  
Vol 23 (03) ◽  
pp. 519-520
Author(s):  
Hubert Winston
Keyword(s):  
Computer Simulations ◽  
Flow Rate ◽  
Storage Capacity ◽  
Pulse Length ◽  
Test Area ◽  
Pilot Test ◽  
Test Results ◽  
Pulse Test ◽  
Wellbore Storage ◽  
And Storage

Abstract The nature of wellbore storage is such that afterflow during a pulse test can affect the reservoir pressure performance and can lead to the calculation of erroneous performance and can lead to the calculation of erroneous values for formation transmissibility and storage. This is most likely to occur when the wells of interest are close together or when after flow persists for a long time relative to the pulse length. This article describes a technique that was developed to account for the effects of after flow at the pulsing well during pulse testing of a small production pilot. The technique is not general because it requires that a computer-generated simulation of each pulse test be made. An application of the method is given. Introduction In carrying out a pulse test, we introduce a pressure disturbance into a reservoir by alternately increasing and decreasing the flow rate at the pulsing well in a known manner. The pressure at the responding well is monitored, and, if the wells are in pressure communication, the pressure distrubance eventually will affect the pressure at the responding well. Since the form and the duration of the flow, rate disturbance are known, and since the mathematics that describe the pressure behavior of fluid-beefing reservoirs are well understood, the pulse test pressure response can be predicted. Several methods are available to calculate values for formation transmissibility and storage within a pulse-tested reservoir. Although all real reservoirs are heterogeneous, the models for deriving these techniques assume that the reservoir is ideal. When the wells of interest are far apart or when the duration of after flow is short relative to the pulse length, the effects of wellbore storage on the pulse test results will be slight. If, on the other hand, the pulsing well and the responding well are close together or if after flow persists for a tong time, the effects of wellbore storage on the pulse test results may be substantial. The work described here began during the analysis phase of a series of pulse tests that were run in a small phase of a series of pulse tests that were run in a small pilot test area. Computer simulations of the tests showed pilot test area. Computer simulations of the tests showed that the method of Mondragon and Menzie would not compensate adequately for the strong effects of after flow on test results. Description of the Method Since a series of injection/falloff tests had been run in the pilot area, it was possible to obtain values for the ratio of formation transmissibility to the wellbore storage capacity, /F, at each well by type-curve matching techniques. Using this parameter, we can determine the after flow vs. time profiles that would occur during the pulsing-well shut-in periods and incorporate them into a computer simulation of each pulse test. A typical pulsing well-flow profile showing after flow during the shut-in period is profile showing after flow during the shut-in period is illustrated in Fig. 1. Given that the pulsing wells were observed to go on vacuum soon after shut-in and given that the wellbore storage capacity for these wells during the on-vacuum condition should be approximately two orders of magnitude larger than it would be during injection SPEJ p. 519

How Areal Heterogeneities Affect Pulse-Test Results

1970 ◽  
Vol 10 (02) ◽  
pp. 181-191 ◽  
Author(s):  
Saul Vela ◽  
R.M. McKinley
Keyword(s):  
Time Lag ◽  
Pulse Amplitude ◽  
Test Results ◽  
Hydraulic Diffusivity ◽  
Pulse Test ◽  
Influence Area ◽  
Pulse Testing ◽  
And Storage ◽  
Degree Of Heterogeneity ◽  
Relative Variability

Abstract Reservoir transmissibility and storage values can be obtained from pressure pulses induced in one well and measured at a second well. Such pulse-test values are generally calculated from pulse-test values are generally calculated from equations which assume the formation is homogeneous. This paper examines the effects of areally distributed heterogeneities on pulse-test values. An influence area is first developed for a pulse-tested well pair; only those heterogeneities pulse-tested well pair; only those heterogeneities within this area significantly affect pulse-test results. Next, for three limiting cases, the manner in which a pulse test averages heterogeneities within the influence area is described. These are the cases for which one of the three formation properties - hydraulic diffusivity, transmissibility properties - hydraulic diffusivity, transmissibility and storage - is constant throughout the influence area. Finally, a method called directional correction is developed that when applied to pulse-test values of transmissibility and storage restores some, if not most, of the true degree of heterogeneity to these values. Accuracy of the method depends upon the relative variability of the true values. Introduction The pulse-testing method of Johnson et al. uses a sequence of rate changes at one well to create a low-level pressure interference response at an adjacent well. This response is readily analyzed for reservoir properties if one assumes an infinite, homogeneous reservoir model. The field data of McKinley et al. show that, despite the use of a simple analytical model, pulse-test values are sensitive to between-well pulse-test values are sensitive to between-well formation properties. Calculated values for transmissibility and storage exhibit considerable variation with direction around a central pulsing well. These values cannot, however, reflect the exact degree of heterogeneity since flow about the pulsing well is usually nonradial. pulsing well is usually nonradial. This paper examines the effects of certain idealized types of areal heterogeneities on pulse-test values calculated from the simple model. In pulse-test values calculated from the simple model. In particular, an influence area for a pulse-tested well particular, an influence area for a pulse-tested well pair is first developed. This area is defined as that pair is first developed. This area is defined as that areal portion of the formation whose properties determine the numerical value, obtained from pulse testing the well pair. Its size depends on the length of the pulse and the hydraulic diffusivity of the formation. We then determine the type of average values yielded by a pulse test when heterogeneities are distributed randomly throughout the influence area. Results of these studies provide a simple correction scheme that restores some of the true degree of heterogeneity to pulse-test values of transmissibility and storage. Accuracy of the method depends on the relative variability of the latter two reservoir parameters. PULSE-TEST TERMINOLOGY AND ANALYSIS PULSE-TEST TERMINOLOGY AND ANALYSIS A typical rate-change sequence at the pulsing well appears at the bottom of Fig. 1. The pulse rate is q reservoir B/D and the pulse length is delta t minutes. The time between pulses is R delta t minutes. Each such pulse cycle induces at the responding well the pressure response (pulse) shown at the top of Fig. 1. According to the analysis method of Johnson et al., each pressure pulse is characterized by two quantities - a time lag, tL minutes, and a pulse amplitude, delta p psi. How these values are pulse amplitude, delta p psi. How these values are determined from the pressure response is apparent from Fig. 1. For an infinite, homogeneous formation, the time lag, tL, the R-value and the well spacing, rws, are sufficient to determine the hydraulic diffusivity, of the formation. These values, coupled with pulse amplitude, p, and pulse rate, q, determine formation transmissibility, =kh/ . Formation storage, = ch, is obtained from the ratio = / . Charts to facilitate this analysis are given by Brigham for R=1. SPEJ P. 181

Overdamped slug test in monitoring wells: review of interpretation methods with mathematical, physical, and numerical analysis of storativity influence

1998 ◽  
Vol 35 (5) ◽  
pp. 697-719 ◽  
Author(s):  
Robert P Chapuis
Keyword(s):  
Numerical Analysis ◽  
Classical Solution ◽  
Heat Conduction Problem ◽  
Solid Matrix ◽  
Test Results ◽  
Slug Test ◽  
Slug Tests ◽  
Monitoring Wells ◽  
Pulse Test ◽  
Negligible Influence

Several methods are available to interpret slug tests; however, when applied to the same test data, they usually yield very different results. The methods are classified into three categories depending on their assumptions about the solid matrix deformability during the test. This paper deals with overdamped tests for elastic solids that deform instantaneously. It provides a unified interpretation of transmissivity T and storativity S based on the velocity graph for variable-head tests in monitoring wells or cased boreholes. If S has little influence, the velocity graph is a straight line. If S has some influence, the graph should give a smooth curve. However, smooth curves are exceptions in practice, thereby leading to a reexamination of the influence of S during a slug test. Three independent approaches are used. (1) A mathematical review shows that the overdamped solution, as adapted from a heat conduction problem, did not correctly treat storativity terms and the type of problem: it corresponds to a special pulse test, not a slug test. (2) A physical investigation of deformability shows that the influence of S does not exceed 1% of the initial slug for most compressible materials. Thus, it is almost impossible to detect its influence in test results. (3) Numerical analyses confirm that S has a negligible influence: test results provide straight lines, not curves. The numerical analysis of the special pulse test provides exactly the classical solution, and the correct values of T and S after eliminating the confusion about storativity terms. It is concluded that (1) S has a negligible influence in slug tests, (2) the existing classical solution giving T and S must be abandoned, and (3) the velocity-graph equation and its integral equation (Hvorslev or Bouwer and Rice) which correctly describe the process must be used.Key words: slug test, hydraulic conductivity, storativity, numerical modeling.

Effect of Wellbore Storage on Pulse-Test Pressure Response

1975 ◽  
Vol 27 (06) ◽  
pp. 707-709 ◽  
Author(s):  
M. Prats ◽  
J.B. Scott
Keyword(s):  
Pressure Response ◽  
Pulse Test ◽  
Wellbore Storage ◽  
Test Pressure

scholarly journals A current-source concept for fast and efficient driving of silicon carbide transistors

2013 ◽  
Vol 62 (2) ◽  
pp. 333-343 ◽  
Author(s):  
Jacek Rąbkowski
Keyword(s):  
Magnetic Field ◽  
Silicon Carbide ◽  
Current Source ◽  
Practical Implementation ◽  
Test Results ◽  
Pulse Test ◽  
Switching Performance ◽  
Gate Capacitance ◽  
A Current ◽  
Gate Drivers

Abstract The paper discusses the application of the current-source concept in the gate drivers for silicon carbide transistors. There is a common expectation that all SiC devices will be switched very fast in order to reach very low values of switching energies. This may be achieved with the use of suitable gate drivers and one of possibilities is a solution with the current source. The basic idea is to store energy in magnetic field of a small inductor and then release it to generate the current peak of the gate current. The paper describes principles of the current-source driver as well as various aspects of practical implementation. Then, the switching performance of the driven SiC transistors is illustrated by double-pulse test results of the normally-ON and normally-OFF JFETs. Other issues such as problem of the drain-gate capacitance and power consumption are also discussed on the base of experimental results. All presented results show that the currentsource concept is an interesting option to fast and efficient driving of SiC transistors.

Pulse-Test Response of a Two-Zone Reservoir

1970 ◽  
Vol 10 (03) ◽  
pp. 245-256 ◽  
Author(s):  
E.G. Woods
Keyword(s):  
Flow Rate ◽  
Single Layer ◽  
Pressure Response ◽  
Test Results ◽  
Well Test ◽  
Reservoir Model ◽  
Reservoir Properties ◽  
Pulse Test ◽  
Pulse Testing ◽  
Single Well

Woods, E.G., Member AIME, Esso Production Research Co., Houston, Tex. Abstract A mathematical investigation of pressure response of two-zone reservoirs indicates apparent transmissibility (kh/ ) obtained by pulse testing is always equal to or greater than the total transmissibility of the zones, and that apparent storage (phi ch) is always equal to or less than the total storage of the zones. These apparent zone properties approach total properties as vertical fluid communication between zones increases. The presence of non uniform wellbore damage in the zones alters the division of flow between zones, and consequently, alters their apparent transmissibility ratio. In the absence of wellbore damage. the flow-rate ratio is a good estimator of the transmissibility ratio of the zones. A procedure is proposed for advantageously using differences in reservoir properties determined by single-well tests and pulse tests to describe flow properties of two-zone reservoirs. A numerical properties of two-zone reservoirs. A numerical example is included. Introduction Pulse tests, interference tests, and single-well pressure buildup or drawdown tests have been used pressure buildup or drawdown tests have been used to estimate reservoir properties. These pressure transient tests are normally analyzed with mathematical models which assume that the reservoir is a homogeneous single layer. Various techniques for analyzing single-well test data to obtain information about the properties of layered reservoirs have been shown by others to have limited applicability. This mathematical study was undertaken to determine what errors could be caused by interpreting pulse tests (in a multizone reservoir) with a single-layer model. Pulse testing is based on the measurement and interpretation of a pressure response in one well to a transient pressure disturbance introduced by varying flow rate at an adjacent well. The measured pressure response is usually a few hundredths of a pressure response is usually a few hundredths of a pound per square inch. Pulse-test terminology is pound per square inch. Pulse-test terminology is shown in Fig. 1; Johnson et al. give a complete description of pulse testing. Measured at the wellhead or in the wellbore, pressure response is a function of reservoir pressure response is a function of reservoir transmissibility (T=kh/mu) and diffusivity (n = k/phi cmu) in the region between the two wells; from these two quantities reservoir storage ( = /n=phi ch) can be derived. The analysis presented here discusses additional reservoir information made available by pulse testing and shows that single-well test and pulse-test results can be combined to give more information about a two-zone reservoir than either type of test alone. Also, procedures are given for estimating the magnitude of error if test results of a two-one reservoir are interpreted with the assumption that it is a one-zone, vertically homogeneous, reservoir. Discussions of theoretical work, field data requirements, interpretation procedure, and a numerical example follow. Details of the mathematical model are given in the Appendix. THEORETICAL STUDY - TWO-ZONE MODEL Reservoir Model - Assumptions and Boundary Conditions A reservoir model consisting of two zones penetrated by two wells, each of which is completed in both zones was assumed (Fig. 2). SPEJ p. 245

Using Conventional Articulation Tests With Highly Unintelligible Children

1992 ◽  
Vol 23 (1) ◽  
pp. 52-60 ◽  
Author(s):  
Pamela G. Garn-Nunn ◽  
Vicki Martin
Keyword(s):  
Test Results ◽  
Phonological Processes ◽  
Rule Based ◽  
Severity Level ◽  
Error Sensitivity ◽  
Conventional Tests ◽  
Severity Levels ◽  
Conventional Test ◽  
Impaired Children

This study explored whether or not standard administration and scoring of conventional articulation tests accurately identified children as phonologically disordered and whether or not information from these tests established severity level and programming needs. Results of standard scoring procedures from the Assessment of Phonological Processes-Revised, the Goldman-Fristoe Test of Articulation, the Photo Articulation Test, and the Weiss Comprehensive Articulation Test were compared for 20 phonologically impaired children. All tests identified the children as phonologically delayed/disordered, but the conventional tests failed to clearly and consistently differentiate varying severity levels. Conventional test results also showed limitations in error sensitivity, ease of computation for scoring procedures, and implications for remediation programming. The use of some type of rule-based analysis for phonologically impaired children is highly recommended.

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