New Correlations for Time Lags and Pressure Response Amplitude in Pulse-Test Analysis

1991 ◽  
Author(s):  
N.A.F. El-Khatib
Keyword(s):  
Pressure Response ◽  
Response Amplitude ◽  
Time Lags ◽  
Test Analysis ◽  
Pulse Test

Pulse-Testing Response for Unequal Pulse and Shut-In Periods (includes associated papers 14253, 19365, 20792, 21608, 23476 and 23840 )

1975 ◽  
Vol 15 (05) ◽  
pp. 399-410 ◽  
Author(s):  
M. Kamal ◽  
W.E. Brigham
Keyword(s):  
Pressure Gauge ◽  
Cycle Period ◽  
Time Lags ◽  
Pulse Test ◽  
Flow Disturbances ◽  
Pulse Ratio ◽  
Pulse Testing ◽  
Highly Sensitive ◽  
Dimensionless Groups ◽  
Interference Tests

Abstract 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^

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

Calibration of naturally fractured reservoir models using integrated well-test analysis – an illustration with field data from the Barents Sea

2021 ◽  
pp. petgeo2020-042
Author(s):  
D. Egya ◽  
P. W. M. Corbett ◽  
S. Geiger ◽  
J. P. Norgard ◽  
S. Hegndal-Andersen
Keyword(s):  
Field Data ◽  
Barents Sea ◽  
Fractured Reservoirs ◽  
Pressure Response ◽  
Fractured Reservoir ◽  
Well Test ◽  
Well Test Analysis ◽  
Test Analysis ◽  
The Barents Sea ◽  
Naturally Fractured

This paper successfully applied the geoengineering workflow for integrated well-test analysis to characterise fluid flow in a newly discovered fractured reservoir in the Barents Sea. A reservoir model containing fractures and matrix was built and calibrated using this workflow to match complex pressure transients measured in the field. We outline different geological scenarios that could potentially reproduce the pressure response observed in the field, highlighting the challenge of non-uniqueness when analysing well-test data. However, integrating other field data into the analysis allowed us to narrow the range of uncertainty, enabling the most plausible geological scenario to be taken forward for more detailed reservoir characterisation and history matching. The results provide new insights into the reservoir geology and the key flow processes that generate the pressure response observed in the field. This paper demonstrates that the geoengineering workflow used here can be applied to better characterise naturally fractured reservoirs. We also provide reference solutions for interpreting well-tests in fractured reservoirs where troughs in the pressure derivative are recognisable in the data.

New Approach for Pulse Test Analysis

2013 ◽  
Author(s):  
Noaman El-Khatib
Keyword(s):  
Test Analysis ◽  
New Approach ◽  
Pulse Test

Reservoir Characterization Constrained to Well-Test Data: A Field Example

2000 ◽  
Vol 3 (04) ◽  
pp. 325-334 ◽  
Author(s):  
J.L. Landa ◽  
R.N. Horne ◽  
M.M. Kamal ◽  
C.D. Jenkins
Keyword(s):  
Mathematical Model ◽  
Test Data ◽  
Pressure Response ◽  
Well Testing ◽  
Pressure Measurements ◽  
Well Test ◽  
Well Test Analysis ◽  
Test Analysis ◽  
Reservoir Description ◽  
Different Sources

Summary In this paper we present a method to integrate well test, production, shut-in pressure, log, core, and geological data to obtain a reservoir description for the Pagerungan field, offshore Indonesia. The method computes spatial distributions of permeability and porosity and generates a pressure response for comparison to field data. This technique produced a good match with well-test data from three wells and seven shut-in pressures. The permeability and porosity distributions also provide a reasonable explanation of the observed effects of a nearby aquifer on individual wells. As a final step, the method is compared to an alternate technique (object modeling) that models the reservoir as a two-dimensional channel. Introduction The Pagerungan field has been under commercial production since 1994. This field was chosen to test a method of integrating dynamic well data and reservoir description data because the reservoir has only produced single phase gas, one zone in the reservoir is responsible for most of the production, and good quality well-test, core, and log data are available for most wells. The method that was used to perform the inversion of the spatial distribution of permeability and porosity uses a parameter estimation technique that calculates the gradients of the calculated reservoir pressure response with respect to the permeability and porosity in each of the cells of a reservoir simulation grid. The method is a derivative of the gradient simulator1 approach and is described in Appendices A and B. The objective is to find sets of distributions of permeability and porosity such that the calculated response of the reservoir closely matches the pressure measurements. In addition, the distributions of permeability and porosity must satisfy certain constraints given by the geological model and by other information known about the reservoir. Statement of Theory and Definitions The process of obtaining a reservoir description involves using a great amount of data from different sources. It is generally agreed that a reservoir description will be more complete and reliable when it is the outcome of a process that can use the maximum possible number of data from different sources. This is usually referred to in the literature as "data Integration." Reservoir data can be classified as "static" or "dynamic" depending on their connection to the movement or flow of fluids in the reservoir. Data that have originated from geology, logs, core analysis, seismic and geostatistics can be generally classified as static; whereas the information originating from well testing and the production performance of the reservoir can be classified as dynamic. So far, most of the success in data integration has been obtained with static information. Remarkably, it has not yet become common to completely or systematically integrate dynamic data with static data. A number of researchers,2–5 are studying this problem at present. This work represents one step in that direction. Well Testing as a Tool for Reservoir Description. Traditional well-test analysis provides good insight into the average properties of the reservoir in the vicinity of a well. Well testing can also identify the major features of relatively simple reservoirs, such as faults, fractures, double porosity, channels, pinchouts, etc. in the near well area. The difficulties with this approach begin when it is necessary to use the well-test data on a larger scale, such as in the context of obtaining a reservoir description. One of the main reasons for these difficulties is that traditional well-test analysis handles transient pressure data collected at a single well at a time, and is restricted to a small time range. As a result, traditional well-test analysis does not make use of "pressure" events separated in historical time. The use of several single and multiple well tests to describe reservoir heterogeneity has been reported in the literature,6 however, this approach is not applied commonly because of the extensive efforts needed to obtain a reservoir description. The method presented in this paper uses a numerical model of the reservoir to overcome these shortcomings. It will be shown that pressure transients can be used effectively to infer reservoir properties at the scale of reservoir description. Well-test data, both complete tests and occasional spot pressure measurements, will be used to this effect. The well-test information allows us to infer properties close to the wells and, when combined with the shut-in pressures (spot pressure), boundary information and permeability-porosity correlations, provides the larger scale description. General Description of the Method The proposed method is similar to other parameter estimation methods and thus consists of the following major items: the mathematical model, the objective function and the minimization algorithm. Mathematical Model. Because of the complexity of the reservoir description, the reservoir response must be computed numerically. Therefore, the pressure response is found using a numerical simulator. The reservoir is discretized into blocks. The objective is to find a suitable permeability-porosity distribution so that values of these parameters can be assigned to each of the blocks.

Pulse Tests and Other Early Transient Pressure Analyses for In-Situ Estimation of Vertical Permeability

1974 ◽  
Vol 14 (01) ◽  
pp. 75-90 ◽  
Author(s):  
George J. Hirasaki
Keyword(s):  
Pressure Response ◽  
Gravity Drainage ◽  
Transient Pressure ◽  
Type Curve ◽  
Pulse Test ◽  
Recovery Processes ◽  
Vertical Permeability ◽  
Constant Rate ◽  
Rate Test

Abstract Formation vertical permeability is often the dominant influence in water or gas coning into a well, in gravity drainage of high-relief reservoirs, and in interlayer crossflow in secondary recovery projects. The advantages of either conducting a projects. The advantages of either conducting a pulse test or analyzing the early transient pressure pulse test or analyzing the early transient pressure response of a constant-rate test compared with previous techniques are simplicity of interpretation, previous techniques are simplicity of interpretation, short duration of test, and minimum interference from conditions some distance from the test well. The pulse test has a further advantage over the constant-rate test in that the rate does not have to be kept constant during the short flow period.Presented are the development of the theory and the curves of the dimensionless response time used in interpreting field data obtained by these techniques. The vertical permeability is determined with the pulse test from the time to the maximum pressure response and with the constant-rate test pressure response and with the constant-rate test from the extrapolated time to zero pressure response from the inflection point.Applications of the techniques to layered systems and to an oil zone with underlying water are demonstrated with results of numerical simulations. The vertical-permeability pulse test has been used to estimate the vertical permeability of a low-permeability zone in the Fahud field, Oman. Introduction The formation vertical permeability is often a dominant influence in reservoir recovery processes with vertical fluid flow such as water or gas coning, gravity drainage of high-relief reservoirs, the rising steam process, and displacement by water or gas in a heterogeneous formation. How reliably numerical reservoir simulators can predict the recovery performance of these processes depends upon how performance of these processes depends upon how accurately the significant reservoir parameters are estimated. Furthermore, in simulating a reservoir in two dimensions, the validity of the assumption of vertical equilibrium is based on the value of the vertical permeability.With the previously mentioned recovery processes, the reservoir cannot be modeled as a homogeneous reservoir with a single fluid. A well that has fluid coning or that is producing by gravity drainage will often have a fluid contact intersecting the well and thus dividing the reservoir into zones of differing mobility and compressibility. Reservoir stratification on a microscopic scale will result in a vertical permeability that is less than the horizontal permeability that is less than the horizontal permeability; but stratification on a macroscopic permeability; but stratification on a macroscopic scale will divide the reservoir into zones of differing permeabilities. Thus the design and interpretation permeabilities. Thus the design and interpretation of a vertical-permeability test for most practical reservoir situations will require that the reservoir zonation be represented.Transient pressure techniques for estimating in-situ vertical permeability have been introduced by Burns and by Prats. Both techniques require injection or production at a constant rate from a short perforated interval and measurement of the pressure response at another perforated interval pressure response at another perforated interval that is isolated from the first by a packer. The interpretation technique of Burns required a computer-generated type curve or a single-phase numerical reservoir simulator. This type-curve approach is applicable for an anisotropic, homogeneous, infinite reservoir model, and the numerical simulator with a regression analysis program is needed for finite or layered reservoir models. The technique presented by Prats did not require a computer program because the result of the analysis was presented on a single graph. The horizontal and vertical permeabilities could be estimated from the slope and the intercept of the pressure response and, the appropriate value from the graph. The method of Prats was based on an infinite, anisotropic, Prats was based on an infinite, anisotropic, homogeneous reservoir model.The pulse test and early transient analysis techniques presented here were developed to provide a simple means of interpretation for layered provide a simple means of interpretation for layered systems. Some advantages are thatno computer program is requiredlayered reservoirs can be program is requiredlayered reservoirs can be represented;test duration is shorter than for previous methods; andthere is less interference previous methods; andthere is less interference from reservoir conditions some distance from the test well. SPEJ P. 75

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

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