New Type Curves for the Analysis of Pressure Transient Data Dominated by Skin and Wellbore Storage—Non-Newtonian Fluid

2007 ◽  
Author(s):  
Djebbar Tiab
Keyword(s):  
Newtonian Fluid ◽  
Pressure Transient ◽  
Type Curves ◽  
Wellbore Storage ◽  
New Type ◽  
Transient Data

A New Method to Identify and Quantify Hydraulic Communication between Isolated Reservoir Systems Using Pressure-Transient Data

2021 ◽  
Author(s):  
Hasan A. Nooruddin ◽  
N. M. Anisur Rahman
Keyword(s):  
Test Duration ◽  
Well Test ◽  
Pressure Transient ◽  
Type Curves ◽  
Unlimited Number ◽  
Communication Mechanism ◽  
Wide Range ◽  
Transient Data ◽  
New Formulation ◽  
The Impact

Abstract A new analytical workflow that uses pressure-transient data to characterize connectivity between two originally non-communicating reservoir zones is presented. With this technique, hydraulic communication is clearly identified and corresponding fluid crossflow rates accurately quantified. It is applicable to a wide range of communication mechanisms, including inactive commingled-completion wells, conductive fractures and faults, in addition to behind-casing completion problems. The impact of interference is also captured by handling an unlimited number of wells and communicating media. The solution uses pressure-transient data effectively to diagnose communication and estimate the amount of transported fluids. The new formulation is a general formulation for handling an unlimited number of producing wells and communicating media, which helps analyze pressure responses under the influence of interference. The reservoir system under consideration is assumed to be two-dimensional with two initially-isolated reservoir zones, intersected by an arbitrary number of wells, part of which are active producers while others can be penetrating wells with commingled completion, in addition to other communicating media. The well test duration is assumed long enough for the pressure-transient data to be affected by fluid communication. To demonstrate the applicability of the new model, a synthetic case study is presented to diagnose a fluid-communication mechanism. The system under consideration consists of two isolated reservoirs and two wells: a single producer completed in the top reservoir in which pressure responses are measured, and an offset well connecting both reservoirs through a fluid communication mechanism. Using the model, type-curves have been utilized to diagnose the hydraulic communication in the offset well. The connectivity of the communication channel in the offset well is also estimated by matching the pressure-transient responses of the model with the measured data. The rate of crossflow between the two reservoirs is also quantified as a function of time. It is observed from the log-log plot that higher connectivity values of the cement sheath causes a steeper merging ramp in the transition region, following a period dominated by the producing reservoir. Although the rate of crossflow depends on the magnitude of the connectivity, it is observed that there is an upper limit controlled by the rock and fluid properties of the individual reservoirs. In addition, the pressure regime at the location of the offset well plays an important role in the rate of crossflow. This study presents a novel analytical approach to detect communication from pressure-transient data, and to quantify the magnitude of crossflow rates between reservoir zones. The formulation captures the influence of interference between wells caused by production. While complementing diagnostic information from other sources to confirm fluid movement from isolated zones, the method also quantifies the connectivity of the communicating media, and the amount of crossflow rates as a continuous function of time.

scholarly journals Wellbore Effects in the Analysis of Two-Phase Geothermal Well Tests

1982 ◽  
Vol 22 (03) ◽  
pp. 309-320 ◽  
Author(s):  
Constance W. Miller ◽  
Sally M. Benson ◽  
Michael J. O'Sullivan ◽  
Karsten Pruess
Keyword(s):  
Water Reservoir ◽  
Hot Water ◽  
Well Test ◽  
Two Phase ◽  
Pressure Transient ◽  
Analysis Techniques ◽  
Wellbore Storage ◽  
Storage Effects ◽  
Transient Data ◽  
Well Tests

Abstract A method of designing and analyzing pressure transient well tests of two-phase (steam/water) reservoirs is given. Wellbore storage is taken into account, and the duration of it is estimated. It is shown that the wellbore flow can dominate the downhole pressure signal completely such that large changes in the downhole pressure that might be expected because of changes in kinematic mobility are not seen. Changes in the flowing enthalpy from the reservoir can interact with the wellbore flow so that a temporary plateau in the downhole transient curve is measured. Application of graphical and nongraphical methods to determine reservoir parameters from drawdown tests is demonstrated. Introduction Pressure transient data analysis is the most common method of obtaining estimates of the in-situ reservoir properties and the wellbore condition. Conventional graphical analysis techniques require that. for a constant flowrate well test in an infinite aquifer, a plot of the downhole pressure vs. log time yields a straight line after wellbore storage effects are over. The slope of that line is inversely proportional to the transmissivity (kh/u) of the reservoir. The extrapolated intercept of this line with the pressure axis at a specified time (1 hour or 1 second depending on the units used) gives the factor 0 Cth(re2), which is used to calculate the skin value of a well. In this study, the effects of a two-phase steam/water mixture in the reservoir and/or the wellbore on pressure transient data have been investigated. There have been a number of attempts to extend conventional testing and analysis techniques to two-phase geothermal reservoirs including drawdown analysis by Garg and Pritchett, Garg, Grant, and Moench and Atkinson. Pressure buildup analysis has been investigated by Sorey et al. To solve the diffusion equation that governs the pressure change in a two-phase reservoir analytically, it is necessary to make a number of simplifying assumptions. One assumption is that the fluid compressibility in the reservoir is initially uniform and remains uniform throughout the test. With this approach, it can be shown that a straight line on a pressure vs. log time plot will be obtained, the slope being inversely proportional to the total kinematic mobility When conducting a field test it is rarely possible to maintain the uniform saturation distribution in the reservoir required for that type of analysis to be applicable. In addition, the very high compressibility of the two-phase fluid creates wellbore storage of very long duration. Since most of the available instrumentation for hot geothermal wells (greater than 200C) can withstand geothermal environments for only limited periods, long-duration wellbore storage further complicates data analysis. Thus numerical simulation techniques must be used to study well tests to determine the best method of testing two-phase reservoirs. This work investigates and defines more thoroughly the well/reservoir system when the reservoir or wellbore is filled with a two-phase fluid. Four examples are considered:a single-phase hot water reservoir connected to a partially two-phase wellbore,a hot water reservoir that becomes two-phase during the test,a two-phase liquid-dominated reservoir, anda two-phase vapor-dominated reservoir. State-of-the-art analysis techniques are applied to pressure transient data after wellbore storage effects have ended. In the first example, a nongraphical method of analysis is discussed, which is applicable at early times when wellbore storage effects still dominate the pressure response. Note that our analysis has been done for a two-phase homogeneous, nonfractured reservoir. Previous studies of well test methods for two-phase reservoirs have been restricted to this case. SPEJ P. 309^

The Fenske Conservation Method for Pressure Transient Solutions with Storage

1985 ◽  
Vol 25 (03) ◽  
pp. 437-444
Author(s):  
R.N. Horne
Keyword(s):  
Diffusion Equation ◽  
Closed Form ◽  
Approximate Method ◽  
Simple Approximation ◽  
Tabular Data ◽  
Pressure Transient ◽  
Type Curves ◽  
System Pressure ◽  
Wellbore Storage ◽  
Transient Solutions

Abstract A method for determining pressure transient solutions for wells with storage (and skin) is presented, based upon an approach developed by Fenske in the ground water literature. By specifically conserving the entire mass of the system, including the wellbore or wellbores, it is possible to generate many common type curves. The procedure can be developed in an exact manner, in which case it is equivalent to existing techniques, however, a simple approximation step makes possible the generation of common solutions without recourse to numerical or ornate analytical techniques. In some cases the approximation provides equivalent solutions with substantially less computation, in other cases the Solutions are significantly in error, although perhaps still usable. The achievement of computationally rapid, closed-form solutions is of significant advantage for current developments in computerized interpretation. Examples shown in the paper demonstrate the application of the approximate Fenske method, and its exact generalization. The approximate method gives agreement within 2% of the standard single-well, storage and skin type curves. However, as the storage becomes small, as for example in the cylindrical wellbore case (where it is zero), the accuracy becomes unacceptable at early time. As an example of how the method can be applied to configurations other than those developed by Fenske the derivation of the method for the slug test problem is demonstrated. The solution obtained using the approximate method is within acceptable accuracy. The Fenske method is applicable to a wide variety of problems with storage and skin, probably including problems as yet unsolved. An approximate form is available for fast calculation, and the more correct form is equivalent to standard analytical methods. Introduction From a practical standpoint, the derivation of pressure transient solutions often involves intricate mathematics, even for quite simple configurations. As a result, the development of type curves for a new situation becomes a major research project which may involve the analytic or numerical inversion of complex Laplace transforms, numerical integration of Green's or Source Functions, or finite difference techniques. The use of such methods, although mathematically elegant, also makes it difficult to describe the reservoir behavior in a sufficiently closed form that it may be implemented in a computerized interpretation procedure. Such procedures can be designed to handle tabular data, but can operate procedures can be designed to handle tabular data, but can operate much more effectively if the model response (and its derivatives with respect to the unknown reservoir parameters) can be given in the form of analytical expressions. From a philosophical viewpoint, it must be acknowledged that the diffusion equation, which is almost always used to develop pressure transient solutions, does not, in fact, correctly represent pressure transient solutions, does not, in fact, correctly represent the behavior of the physical system. Pressure responses are not received, even infinitesimally, at great distance when a well is opened. Rather, there is a wave component of the response which transmits the signal through the system. Thus, since the diffusion equation is itself only an approximate solution to the problem, it seems opportune to seek a different approximation, hopefully one which does not involve the complexities of Bessel functions, Hankel transforms and series solutions that may be present in solutions to the diffusion equation. A method presented by Fenske in the groundwater literature in 1977 provides an intriguing possibility in the search for alternative solution methods. This method is particularly useful in problems involving wellbore storage, and, as will be shown in this paper, operates by replacing the Green's function of the problem by a simple approximation. By specifically conserving the mass of the system, the Fenske approach is capable of closely approximating known solutions to wellbore storage problems.

Type Curves Analysis for Asymmetrically Fractured Wells

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Lei Wang ◽  
Xiaodong Wang
Keyword(s):  
Asymmetry Factor ◽  
Fracture Conductivity ◽  
Linear Flow ◽  
Type Curves ◽  
Starting Time ◽  
Wellbore Storage ◽  
Constant Rate ◽  
Pressure Depletion ◽  
Storage Effects ◽  
New Type

In this paper, a new constant rate solution for asymmetrically fractured wells was proposed to analyze the effect of fracture asymmetry on type curves. Calculative results showed that for a small wellbore storage coefficient or for the low fracture conductivity, the effect of fracture asymmetry on early flow was very strong. The existence of the fracture asymmetry would cause bigger pressure depletion and make the starting time of linear flow occur earlier. Then, new type curves were established for different fracture asymmetry factor and different fracture conductivity. It was shown that a bigger fracture asymmetry factor and low fracture conductivity would prolong the time of wellbore storage effects. Therefore, to reduce wellbore storage effects, it was essential to keep higher fracture conductivity and fracture symmetry during the hydraulic fracturing design. Finally, a case example is performed to demonstrate the methodology of new type curves analysis and its validation for calculating important formation parameters.

Pressure Transient Data Acquisition and Analysis Using Real Time Electromagnetic Telemetry

1996 ◽  
Author(s):  
L.E. Doublet ◽  
J.W. Nevans ◽  
M.K. Fisher ◽  
R.L. Heine ◽  
T.A. Blasingame
Keyword(s):  
Data Acquisition ◽  
Real Time ◽  
Pressure Transient ◽  
Transient Data
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