Effect of Scaleup and Aggregation on the Use of Well Tests To Identify Geological Properties

2005 ◽  
Vol 8 (03) ◽  
pp. 248-254 ◽  
Author(s):  
Olubusola O. Thomas ◽  
Rajagopal S. Raghavan ◽  
Thomas N. Dixon
Keyword(s):  
History Matching ◽  
Small Scale ◽  
Well Test ◽  
Transient Pressure ◽  
Fine Grid ◽  
Pressure Transient ◽  
Number Of Layers ◽  
Pressure Test ◽  
Well Tests ◽  
The Impact

Summary This paper discusses specific issues encountered when pressure tests are analyzed in reservoirs with complex geological properties. These issues relate to questions concerning the methodology of scaleup, the degree of aggregation, and the reliability of conventional methods of analysis. The paper shows that if we desire to use pressure-transient analysis to determine more complex geological features such as connectivity and widths of channels, we need a model that incorporates reservoir heterogeneity. This complexity can lead to significantly more computational effort in the analysis of the pressure transient. The paper demonstrates that scaleup criteria, based on steady-state procedures, are inadequate to capture transient pressure responses. Furthermore, the number of layers needed to match the transient response may be significantly greater than the number of layers needed for a reservoir-simulation study. The use of models without a sufficient number of layers may lead to interpretations that are in significant error. The paper compares various vertical aggregation methods to coarsen the fine-grid model. The pressure-derivative curve is used as a measure of evaluating the adequacy of the scaleup procedure. Neither the use of permeability at a wellbore nor the average layer permeability as criteria for the aggregation was adequate to reduce the number of layers significantly. Introduction The objectives of this paper are to demonstrate the impact of the detailed and small-scale heterogeneities of a formation on the flow characteristics that are obtained from a pressure test and how those heterogeneities affect the analysis of the pressure test. The literature recognizes that special scaleup procedures are required in the vicinity of wells located in heterogeneous fields. Our work demonstrates that these procedures apply only to rather small changes in pressure over time and are usually inadequate to meet objectives for history-matching well tests. Using a fine-scale geological model derived by geological and geophysical techniques, this work systematically examines the interpretations obtained by various aggregation and scaleup techniques. We will demonstrate that unless care is taken, the consequences of too much aggregation may lead to significant errors on decisions concerning the value of a reservoir. Current scaleup techniques presume that spatial (location of boundaries, location of faults, etc.) variables are maintained. In analyzing a well test, however, one of our principal objectives is to determine the relationship between the well response and geometrical variables. We show that a limited amount of aggregation will preserve the spatial and petrophysical relationships we wish to determine. At this time, there appears to be no method available to determine the degree of scaleup a priori. Because the objective of well testing is to estimate reservoir properties, the scaleup process needs to be made a part of the history-matching procedure. By assuming a truth case, we show that too much vertical aggregation may lead to significant errors. Comparisons with traditional analyses based on analytical techniques are made. Whenever an analytical model is used in the analysis, unless otherwise stated, we use a single-layer-reservoir solution.

Properties of a Natural Fracture and Its Skins From Reservoir Well Tests

SPE Journal ◽  
2013 ◽  
Vol 19 (03) ◽  
pp. 390-397 ◽  
Author(s):  
M.. Prats ◽  
R.. Raghavan
Keyword(s):  
History Matching ◽  
Flow Resistance ◽  
Short Interval ◽  
Natural Fracture ◽  
Disperse Flow ◽  
Well Test ◽  
Transient Pressure ◽  
Matrix Permeability ◽  
Wide Range ◽  
Well Tests

Summary Two well tests are described that are aimed at the in-situ determination of the flow capacity (permeability-thickness product) of a natural fracture and the flow resistance of its skins at the boundaries with the reservoir matrix. Fracture skins tend to disperse flow, thus affecting the distribution of tracers in reservoir tests and contaminants and trace elements in aquifers. We are unaware of any other analytical procedure aimed at obtaining the properties of a natural fracture and its skins from subsurface measurements. Neither well test has been implemented. The well tests are modeled after previously reported analytical expressions for the transient pressure distributions in a three-region composite reservoir in a uniform-thickness reservoir in which (1) the natural fracture is represented by a thin middle region of relatively high permeability, (2) the pressure disturbance is caused by producing from a short interval in one of the outer regions, and (3) the response is measured relatively near the fracture. The source and sensor may be on the same side or on opposite sides of the fracture, distinguishing the two tests. Visualizing special completions in a horizontal well intersecting a natural fracture normally, pressure responses are given for both tests for a wide range of fracture/matrix permeability ratios and skin flow resistances for a source 190 ft from the fracture and 10 ft from the sensor and on either side of the fracture, both at the midplane of the reservoir. A simple graphical procedure, not intended to replace history matching or regression where field data are available, illustrates how the two unknowns—permeability-thickness product of a natural fracture and the flow resistance of its skins—may be estimated from two representative values of an assumed measured pressure response.

scholarly journals An approximation of behind-casing hydraulic conductivity between layers from transient pressure analysis

DYNA ◽  
2019 ◽  
Vol 86 (210) ◽  
pp. 108-114
Author(s):  
Freddy Humberto Escobar ◽  
Angela María Palomino ◽  
Alfredo Ghisays Ruiz
Keyword(s):  
Hydraulic Conductivity ◽  
Transient Analysis ◽  
Test Interpretation ◽  
Well Test ◽  
Transient Pressure ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Transient Pressure Analysis ◽  
Pressure Analysis

Flow behind the casing has normally been identified and quantified using production logging tools. Very few applications of pressure transient analysis, which is much cheaper, have been devoted to determining compromised cemented zones. In this work, a methodology for a well test interpretation for determining conductivity behind the casing is developed. It provided good results with synthetic examples.

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.

Transient Pressure Analysis of Wells Intercepted by Partially Penetrating Finite Conductivity Hydraulic Fractures

2013 ◽  
Vol 446-447 ◽  
pp. 479-485
Author(s):  
De Tang Lu ◽  
Qing Xie ◽  
Cong Niu ◽  
Lei Wang
Keyword(s):  
Hydraulic Fracture ◽  
Transient Analysis ◽  
Contradictory Result ◽  
Hydraulic Fractures ◽  
Finite Conductivity ◽  
Well Test ◽  
Analysis Model ◽  
Transient Pressure ◽  
Pressure Transient Analysis ◽  
Pressure Transient

Most current pressure transient analysis techniques of hydraulically fractured wells are based on the fully penetrating assumption, which assumes equal thickness of hydraulic fracture and the formation. However, field application show that the fractures thickness can be shorter than the thickness of formation, which leads to vertical flow into the fracture. Thus applying the thickness equality assumption of current well test models to a partial penetrating fracture may give contradictory result. Further, there are very few studies concerning pressure transient analysis of partial penetrated wells. So it is important to develop analysis model and procedure to this type of fracture. In this paper, we presented an analytical model for partially penetrating hydraulic fracture in isotropic systems, along with the assumption that fracture is finite conductive. This model is then applied in the analysis of field production data, which verified validity of this new model.

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^

scholarly journals Development of a Semi-Analytical Type Curve of Transient Pressure Response in Complex Well-Reservoir Architectures

2019 ◽  
Vol 20 (2) ◽  
pp. 61-69
Author(s):  
Ibrahim Saeb Salih ◽  
Hussain Ali Baker
Keyword(s):  
Transient Response ◽  
Pressure Response ◽  
Skin Permeability ◽  
Well Testing ◽  
Well Test ◽  
Transient Pressure ◽  
Well Test Analysis ◽  
Pressure Transient ◽  
Analytical Approaches ◽  
Complex Well

The objective of the conventional well testing technique is to evaluate well- reservoir interaction through determining the flow capacity and well potential on a short-term basis by relying on the transient pressure response methodology. The well testing analysis is a major input to the reservoir simulation model to validate the near wellbore characteristics and update the variables that are normally function of time such as skin, permeability and productivity multipliers. Well test analysis models are normally built on analytical approaches with fundamental physical of homogenous media with line source solution. Many developments in the last decade were made to increase the resolution of transient response derivation to meet the complexity of well and flow media.    Semi-analytical modeling for the pressure transient response in complex well architecture and complex reservoirs were adopted in this research. The semi analytical solution was based on coupling the boundary condition of source function to the well segment. Coupling well-reservoir on sliced based technique was used to re-produce homogenous isotropic media from several source functions of different properties. The approach can model different well geometries penetrated complex reservoirs. A computer package was prepared to model the pressure transient response of horizontal, dual-lateral, multi-lateral wells in complex anisotropic reservoirs, multilayered, compartmentalized, system of various boundary conditions such as: bottom support aquifers, edge supported, gas caps, interference of injection. The validity of the proposed model was successfully checked by using the commercial simulator.

Modeling the Interfering Effects of Gas Condensate and Geological Heterogeneities on Transient Pressure Response

SPE Journal ◽  
2013 ◽  
Vol 18 (04) ◽  
pp. 656-669 ◽  
Author(s):  
H.. Hamdi ◽  
M.. Jamiolahmady ◽  
P.W.M.. W.M. Corbett
Keyword(s):  
Present Report ◽  
Early Time ◽  
Pressure Response ◽  
Gas Condensate ◽  
Well Test ◽  
Transient Pressure ◽  
Sensitivity Coefficients ◽  
Vertical Permeability ◽  
Single Well ◽  
The Impact

Summary Numerous publications have investigated the effect of gas condensate fluid on the transient pressure well-test (WT) response. However, to the best of our knowledge, its combined effect with geology has rarely been studied. Our findings in the present report demonstrate that geology can complicate the WT response and make it difficult for interpretation. In this study, the impact of geological heterogeneities on the WT response of a commingled braided fluvial gas condensate reservoir has been investigated. Numerical WT data were generated for a single-well model with a commercial compositional reservoir simulator. Several sensitivity simulations were performed to explore the effects of correlation length, vertical permeability, production rate, and drawdown time on the pseudopressure-derivative curves. The WT weighting kernel function and the calculated well-pressure sensitivity coefficients were implemented to demonstrate different trends of drawdown and buildup responses encountered in this study. The results clarified the idea that some geological heterogeneities and production parameters can alter pressure distribution and condensate saturation and mask the native model WT signatures. In this exercise, it was demonstrated that ramp effect, a geologically complex phenomenon in high-net/gross commingled reservoirs, is affected by the condensate formation. This interfering phenomenon is reflected on the derivative curves and is magnified in the presence of the shorter correlation lengths, the lower vertical communications, and the higher production rates. We also examined the stepwise stripping of the reservoir heterogeneity, demonstrating the significant impact of some facies on the buildup and drawdown transient pressure response. The time-dependent sensitivity coefficients were calculated to show that the drawdown test is sensitive to effective permeability in near-wellbore regions, in which condensate is prone to build up with time. In the buildup, on the other hand, the condensate saturation is almost invariant with time and affects the early-time region. This work leads toward better understanding of the influence of geology in gas condensate WT interpretation of fluvial reservoirs.

Can Values of Honesty, Hard Work, Loyalty and Discipline Predict Entrepreneurial Orientation of Muslim Owner Managers?

2015 ◽  
Vol 3 (1) ◽  
pp. 31 ◽  
Author(s):  
Rohani Mohd ◽  
Badrul Hisham Kamaruddin ◽  
Khulida Kirana Yahya ◽  
Elias Sanidas
Keyword(s):  
Entrepreneurial Orientation ◽  
Two Dimensions ◽  
Hard Work ◽  
Small Scale ◽  
Sampling Frame ◽  
Policy Makers ◽  
Learning Institutions ◽  
Innovative Orientation ◽  
The Impact ◽  
True Values

The purpose of the present study is twofold: first, to investigate the true values of Muslim owner managers; second, to examine the impact of these values on entrepreneurial orientations of Muslim small-scale entrepreneurs. 850 Muslim owner managers were selected randomly using the sampling frame provided by MajlisAmanah Rakyat Malaysia (MARA). 162 completed questionnaires were collected and analyzed. For this paper only two dimensions of entrepreneurial orientations were analyzed: proactive orientation and innovative orientation. Interestingly, the findings revealed that Muslim businessmen/women are honest, loyal, disciplined and hard working. Loyalty and honesty are positively related to proactive orientation, while discipline and hard-work are positively related to innovative orientation. The findings provide implications for existing relevant theories, policy makers, practitioners and learning institutions. 

Sign in / Sign up

Export Citation Format

Share Document