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^

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

INFLUENCE OF TIDAL PHENOMENA ON INTERPRETATION OF PRESSURE BUIILD-UP AND PULSE TESTS

1976 ◽  
Vol 16 (1) ◽  
pp. 99 ◽  
Author(s):  
A.K. Khurana
Keyword(s):  
Time Pressure ◽  
Pressure Gauge ◽  
Early Time ◽  
Late Time ◽  
Time Lags ◽  
Pressure Oscillations ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole ◽  
Gippsland Basin

Bottom-hole pressure tests conducted in the Kingfish oil reservoir (located in Gippsland Basin - Offshore Victoria) during 1974 and 1975 using a high sensitivity surface recording electronic bottom-hole pressure gauge indicated the presence of sinusoidal pressure oscillations in the reservor. The oscillations are of the order of 0.1 psi in amplitude and their frequency suggests that they are in some way related to tidal phenomena.Although the oscillations do not affect production, they do influence interpretation of pressure build-up and pulse tests. Interpretations of both late time pressure build-up behaviour and pulse tests of small response magnitude and long time lags are considered to be particularly susceptible to errors due to these oscillations if they are not recognized and corrected for. Interpretations of early time pressure build-up data and pulse tests of definite response and relatively short time lags are not regarded as being significantly affected.The physical mechanism causing these pressure oscillations in the reservoirs is not known. However, one of the various possible hypotheses is that the Latrobe Formation sands could be outcropping on the ocean floor at abyssal depths southeast of Kingfish and that the pressure transients generated by changes in the hydrostatic head due to surfate tides are transmitted hydraulically to the reservoir. If this hypothesis is proved to be valid it could influence pressure performance predictions of Gippsland Basin reservoirs.

Machine Learning Provides Effective Leak Detection in Carbon Sequestration Projects

2021 ◽  
Vol 73 (07) ◽  
pp. 67-68
Author(s):  
Chris Carpenter
Keyword(s):  
Machine Learning ◽  
Time Series ◽  
Pressure Pulse ◽  
National Laboratory ◽  
Pressure Gauge ◽  
Pressure Data ◽  
Alamos National Laboratory ◽  
Los Alamos National Laboratory ◽  
Pulse Test ◽  
Monitoring Well

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 201552, “Leak Detection in Carbon Sequestration Projects Using Machine Learning Methods: Cranfield Site, Mississippi, USA,” by Saurabh Sinha, SPE, University of Oklahoma and Los Alamos National Laboratory; Rafael Pires De Lima, Geological Survey of Brazil; and Youzuo Lin, Los Alamos National Laboratory, et al., prepared for the 2020 SPE Annual Technical Conference and Exhibition, originally scheduled to be held in Denver, 5–7 October. The paper has not been peer reviewed. Saline aquifers and depleted hydrocarbon reservoirs with good seals located in tectonically stable zones make an excellent storage formation option for geological carbon sequestration.Ensuring that carbon dioxide (CO2) does not leak from these reservoirs is the key to any successful carbon capture and storage (CCS) project. In the complete paper, the authors demonstrate automated leakage detection in CCS projects using pressure data obtained from the Cranfield reservoir in Mississippi in the US. Results indicate that even simple deep-learning architectures such as multilayer feed-forward neural networks (MFNNs) can identify a leak using pressure data. Introduction Several methods that use different types of data currently are available to detect leaks. Although some of the methods are a direct indicator of CO2 presence, they cannot provide an early warning for the leaks, thus delaying remedial measures. An ideal process for the identification of leakages requires constant and repetitive comparisons of different data. Machine-learning (ML) techniques are ideally suited for this task. In this work, the authors demonstrate the use of ML techniques such as linear model, random forest, and MFNN on time-series signals obtained from a pressure-pulse test. The methodology uses the time-series data instead of 2D images or 3D voxels, thus providing a computational advantage. The authors write that an ML algorithm can distinguish between a pressure signal corresponding to a leak vs. the pressure signal corresponding to a baseline nonleak case. The trained models can then be used as an early-warning system to flag anomalous data to then be analyzed by a human interpreter. Background A pressure-pulse test uses at least two wells: an injection well and a monitoring well. The reservoir is then shocked by a series of predetermined cycles of injection and shut-ins (i.e., a pulse). The response then is recorded at the monitoring well with a pressure gauge that measures the target formation pressure. The test may be repeated with different pulses to understand the reservoir properties better. A harmonic pulse is preferred over a square wave because it allows for spectral decomposition of the pulse to analyze the reservoir response at different frequencies. Three wells are used in the study: F1, F2, and F3. Well F1 is the injector well, where alternative cycles of injection of CO2 and shut-in are carried out. Well F2 is the monitor well, which remains shut in for the duration of the test and where the pressure is monitored with the use of a pressure gauge. An artificial leak is simulated in the test by opening a surface valve at Well F3.

Highly Sensitive Capacitive Pressure Gauge

1969 ◽  
Vol 40 (11) ◽  
pp. 1393-1397 ◽  
Author(s):  
G. C. Straty ◽  
E. D. Adams
Keyword(s):  
Pressure Gauge ◽  
Highly Sensitive

Permanent Gauge Pressure and Rate Measurements for Reservoir Description and Well Monitoring: Field Cases

1998 ◽  
Vol 1 (03) ◽  
pp. 224-230 ◽  
Author(s):  
Trond Unneland ◽  
Yves Manin ◽  
Fikri Kuchuk
Keyword(s):  
Pressure Gauge ◽  
Pressure Sensors ◽  
Curve Analysis ◽  
Rate Data ◽  
Well Test ◽  
Reserve Estimation ◽  
Decline Curve Analysis ◽  
Decline Curve ◽  
Reservoir Description ◽  
Interference Tests

Summary This paper presents a procedure for interpreting data acquired with permanent downhole pressure sensors in association with surface or downhole rate measurements. The usefulness of this data source in reservoir description and well performance monitoring is illustrated. Unlike previously published examples, the interpretation is based on the analysis on a stream of data acquired over large periods of time, thus utilizing the continuous nature of the measurements. Three field cases are presented using the pressure and rate data in decline-curve analysis for wells with a variable downhole flowing pressure, and through more sophisticated models that are similar to the ones used in well test analysis. Because such interpretation is conducted while continuing production, it is particularly well suited for a well or group of wells under extended testing, which are equipped with downhole gauges and are flowing through surface separation and metering systems. Wells completed with both permanent downhole rate and pressure measurements are also ideal candidates for this type of analysis. Finally, the influence of the pressure sensor long term drift and the rate measurement error on the interpretation results and future forecasts are investigated. Introduction Since the first permanent downhole gauge installations in the early 1960's on land wells, the new technology in cable manufacturing, gauge sensor and electronics has permitted reliable installations also in hot, deep wells and subsea completions. These systems have gained acceptance among operators, and currently several hundred downhole gauges are installed every year. The traditional applications associated with permanent downhole systems can be characterized by four distinctions:single well optimization,reservoir description,safety improvement, andoperating cost reduction. Combining the recent technology development and these applications, the downhole gauge installations can be safe and reliable, as well as good investments. Most of the previous papers on the subject have focused on the hardware involved in permanent downhole pressure gauge installations. Regarding reservoir description, a few examples have been published where data recorded by the permanent downhole gauges have been used in well test transient analysis and multiwell interference tests. However, little has been published on the use of continuous downhole measurement in order to enhance reservoir description when associated with rate data during the pseudosteady state or depletion period of a field or a separate block. Decline curve analysis is one of the most widely used and documented methods for reserve estimation and production forecasting for a field under depletion. Solutions have been published for the case of a well producing at constant downhole flowing pressure. In reality, due to production constraints or change in operating procedures, the downhole flowing pressure seldom remains at a constant level over long periods of time. In the decline curve analysis literature, various methods have been proposed to account for these pressure variations; these include normalization and various types of superposition based on the pressure change observed at the wellhead.

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

Pulse Testing: Mathematical Analysis and Experimental Verification

1972 ◽  
Vol 12 (05) ◽  
pp. 403-409 ◽  
Author(s):  
A.S. Odeh ◽  
J.M. McMillen
Keyword(s):  
Diffusion Equation ◽  
Test Data ◽  
Pulse Propagation ◽  
Theoretical Research ◽  
Porous System ◽  
Pulse Test ◽  
The Core ◽  
Pulse Testing ◽  
Porosity And Permeability ◽  
Gas Expansion

Abstract This paper covers theoretical research on pulse propagation in linear cores saturated with air, and propagation in linear cores saturated with air, and discusses bow pulse tests in these systems can be analyzed to provide a measure of the porosity and permeability of the porous medium. It also covers permeability of the porous medium. It also covers experimental work designed to compare these properties, as calculated from pulse-test data, with properties, as calculated from pulse-test data, with those determined by conventional measurements. The paper shows that, when such pulse data are analyzed correctly, the comparison is very favorable; i.e., permeability values vary no more than 3 percent and porosity values no more than 0.5 percent. We conclude that pulse experiments with linear cores saturated with air give data, which when analyzed by methods based on the diffusion equation, give permeability and porosity values comparable with permeability and porosity values comparable with those obtained by conventional methods. Introduction Pulse testing is a recently developed method for evaluating reservoir storage capacity and fluid transmissibility. Papers have described the basic theory, based on the diffusion equation, and techniques of pulse testing as applied to field operations. Although some of the papers describe field applications, none report laboratory experimental investigations of pulse testing. This paper covers experimental and theoretical research on pulse propagation through porous media. It tests the adequacy of the use of the diffusion equation as a basis for interpreting pulse-test data. Using the diffusion equation, the theory of pulse propagation in a linear porous system and a method propagation in a linear porous system and a method of interpreting the experimental data are derived. A few experiments conducted on long Berea cores saturated with air are described. The porosity and permeability values were determined by gas expansion permeability values were determined by gas expansion and steady-state flow, respectively, and the values were compared with those theoretically calculated from experimental pulse data. The comparison shows that the values determined by the conventional methods compare well with those calculated from the pulse data. MATHEMATICAL ANALYSIS SOLUTION OF APPROPRIATE EQUATIONS The system to be analyzed consists of a Berea core saturated with air. At a reference time, t = 0, air is injected at a constant rate into one end of the core. At time t the injection is terminated and the injection end is closed. The other end is kept closed during and after injection. The equation which describes the above system, when the pressure variation is small, is the diffusion equation. For flow in porous media, the equation is(1) where c = compressibility in 1/atm k = permeability, darcies L = the length of the core in centimeters for thefinite core, and any arbitrary chosen lengthfor the infinite core p = the pressure in atmosphere at t >0 p = the pressure in atmosphere at t >0 pi = the pressure in atmosphere at t = 0 pi = the pressure in atmosphere at t = 0 Deltap = p - pi t = time, seconds tD = dimensionless time given by x = any distance from the inlet end, cm xD = x/L beta = porosity, fraction mu = viscosity, cp We solved Eq. 1 for two cores, finite and infinite, as shown in the Appendix. SPEJ P. 403

Analytical Model for Vertical Interference Tests Across Low-Permeability Zones

1985 ◽  
Vol 25 (03) ◽  
pp. 407-418 ◽  
Author(s):  
R.E. Bremer ◽  
Winston Hubert ◽  
Vela Saul
Keyword(s):  
Point Source ◽  
Test Data ◽  
Low Permeability ◽  
Test Analysis ◽  
Type Curve ◽  
Type Curves ◽  
Pulse Test ◽  
Vertical Permeability ◽  
Interference Test ◽  
Interference Tests

Abstract A mathematical model is developed that describes fluid flow and pressure behavior in a reservoir consisting of two permeable zones separated by a zone of low permeability, Or a "tight zone." This model can be used to design and to interpret buildup, vertical, interference, and pulse tests conducted in a single well or multiple wells across lithological strata. Dimensionless pressure functions and corresponding parametric type curves are derived to interpret vertical interference test data for tight-zone vertical penneability. Application of these type curves is illustrated using field data from two vertical interference tests. Test results obtained with the tight-zone model are shown to compare favorably with results obtained by usingcomputer simulations andBurns' method based on the uniform anisotropy assumption. Computer simulation using a numerical model also shows that high near-wellbore conductivity from a packer leak or poor cement job could not have adversely affected test results. The model presented and the type-curve interpretation method outlined are accurate for designing and interpreting single-well vertical interference tests across low-permeability zones. Introduction The knowledge of vertical flow properties across a low-permeability stratum is becoming increasingly important in reservoir development, especially when enhanced recovery projects are proposed for stratified reservoirs. Vertical well testing is a technique commonly used to determine values for the in-situ vertical permeability of a formation. Either the vertical interference or vertical pulse test may be used, depending on the amount of time required to obtain the necessary pressure response. The method of vertical interterence testing first was introduced by Burns,1 and later developed by Prats.2 Burns' model is based on the assumption of a homogeneous, infinite-acting reservoir with an average vertical permeability smaller than horizontal permeability. Four geometric parameters are used to computer-generate a type curve for analyzing the test data. One difficulty is that each type curve generated is specific to the four geometric parameters and, hence, to the well completion used. The analysis method proposed by Prats uses a plotting technique that does not require computer solutions. However, his technique is restricted by a point-source assumption; that is, the perforated production and observation intervals must be short compared with the distance between them. The most widely used vertical pulse test analysis technique was developed by Falade and Brigham.3–5 Briefly, the method uses sets of correlation curves relating a dimensionless pulse length and dimensionless pulse amplitude. Corrections can be made to account for the upper and lower formation boundaries. It should be noted that the times as given in the Falade and Brigham technique4,5 are too low by a factor of four.6 A second vertical pulse test analysis method, published by Hirasaki,7 is less general in that it considers only the situation with perforations at the upper and lower boundaries. Both methods use a point-source assumption. All previous vertical interference1,2 and vertical pulse3,4,7 test interpretation techniques were developed to determine vertical permeability in a homogeneous single-layer reservoir. These methods may be applied to stratified reservoirs where permeability contrasts are known to occur; however, they may yield misleading results in these cases where the homogeneous reservoir assumption is not justified. This paper presents an analytical model and interpretation technique to analyze vertical interference test data for tight-zone vertical permeability in a reservoir consisting of two permeable zones separated by a tight zone or a zone of low permeability. Pressure response data in the observation zone are plotted in a ?p vs. ?t format on log-log coordinates and matched against one of two type curves. The result of this match is a value for horizontal permeability in the upper and lower layers and a value for the effective vertical permeability across the tight zone. The type curves included are applicable for a wide range of thickness ratios between the permeable and low-permeability layers. Additionally, use of the model is not restricted by a point-source assumption.

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