Advances in Computer-Aided Well Test Interpretation

Horne, Roland N.

doi:10.2118/24731-pa

Cited by 34 publications

(25 citation statements)

References 9 publications

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“…The technique has become a standard in petroleum engineering over the last 20 years. It has been popularized by a series of papers and books (Bourdet 2002;Bourdet et al 1989;Bourdet et al 1983;Ehlig-Economides et al 1994b;Horne 1995;Horne 1994;Ramey 1992). In hydrogeology, the technique is used routinely only in some specific or highly technical projects such as the safety analysis of nuclear waste repositories.…”

Section: Introductionmentioning

confidence: 99%

“…This is usually done with least-squares procedures and there are many examples of these both in the petroleum and hydrogeology literature (Bardsley et al 1985;Horne 1994). What is important to highlight is that when diagnostic plots are used, it is interesting to display Infinite acting radial flow (IARF) Figure 3 shows an important characteristic of the Theis model: the logarithmic derivative of the model stabilizes at late time.…”

Section: An Introductory Examplementioning

confidence: 99%

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Understanding diagnostic plots for well-test interpretation

2008

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In well-test analysis, a diagnostic plot is a scatter plot of both drawdown and its logarithmic derivative versus time. It is usually plotted in log-log scale. The main advantages and limitations of the method are reviewed with the help of three hydrogeological field examples. Guidelines are provided for the selection of an appropriate conceptual model from a qualitative analysis of the log-derivative. It is shown how the noise on the drawdown measurements is amplified by the calculation of the derivative and it is proposed to sample the signal in order to minimize this effect. When the discharge rates are varying, or when recovery data have to be interpreted, the diagnostic plot can be used, provided that the data are preprocessed by a deconvolution technique. The effect of time shift errors is also discussed. All these examples show that diagnostic plots have some limitations but they are extremely helpful because they provide a unified approach for well-test interpretation and are applicable in a wide range of situations.

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Section: Introductionmentioning

confidence: 99%

Section: An Introductory Examplementioning

confidence: 99%

Understanding diagnostic plots for well-test interpretation

2008

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“…While the application of the derivative to bounded reservoirs was presented by Proano and Lilley (1986). Horne (1994) has summarized modern approaches to well test analysis-using computers and Buhidma and Chu (1992) present state-of-the-art computer application of pressure transient analysis. Djebbar and Henry (1979) shows a type curves matching technique for interpretation of the pressure transient behavior of wells located in various Multiple Sealing-fault systems because the presence of a fault in a reservoir is of great importance, considerable numbers of pressure analysis techniques dealing with this situation have been proposed in literature.…”

Section: Introductionmentioning

confidence: 99%

Well Test and PTA for Reservoir Characterization of Key Properties

Sylvester

Ikporo²,

Ogbon

2015

American Journal of Engineering and Applied Sciences

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Abstract:The characterization of a reservoir is a process which starts from the beginning of the field (oil or gas) discovery and continuous to the field's abandonment. It quantitatively or qualitatively describes the characteristics of the reservoir using data available. In the determination of key well and reservoir parameters for reservoir characterization, it is very vital to understand the flow phases and how to adequately identify them to prevent the challenge of obtaining the require parameters from a wrong phase. Thus, to successfully interpret a well test result either manually or by the use of computer aided software, we need to understand the well, reservoir and boundary models to actually match the field data. This success depends on the range and quality of pressure and rate data available and also the approach adopted for the analysis. This study adopted the method of pressure transient analysis, PTA to determine key well and reservoir parameters. A general well test work flow and the procedure for buildup test is presented. Data were obtained from Agba 8 and Ukot wells in the Niger Delta region of Nigeria and analyzed using well test analysis software 'saphir' to generate the damage and flow parameters around the wellbore. Result shows that Agba 8 well is a candidate well for stimulation operation due to positive skin.

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“…However, measurement errors in time are not uncommon and may play an important role. For example, Horne (1994) discussed the significance of a constant shift in time. The process of quality control of data, especially of flow-rate data, is often imperfect, if done at all.…”

Section: Introductionmentioning

confidence: 99%

Significant Improvement in the Accuracy of Pressure-Transient Analysis Using Total Least Squares

Dastan

Horne

2010

SPE Reservoir Evaluation &Amp; Engineering

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In this study, we show significant improvements over conventional pressure-transient analysis on the basis of nonlinear regression by using total least squares (TLS), which minimizes errors in both pressure and time simultaneously. To our knowledge, TLS has not been applied to pressure-transient analysis before in this sense.TLS regression is not an easy problem to solve mathematically, especially for nonlinear pressure-transient-model functions. In this work, we compare four different versions of TLS. We formulate a robust approximation of the TLS solution, which can handle a variety of tests and reservoir models yet does not compromise the performance of the analysis. We show that our technique reduces ambiguity in the estimation of parameters to a large extent, especially in the presence of noise in time. Using our TLS algorithm, we obtain much narrower confidence intervals on the parameter estimates of a variety of real data sets, compared to the conventional least squares (LS) approach. For synthetic data sets, we observe that the TLS estimates are often closer to the true values than estimates made with LS, especially for poorly determined problems. When the deviation is in pressure only, TLS and LS results are comparable. However, in the presence of deviations in time in addition to pressure, the performance of TLS algorithms is substantially better. We, therefore, expect that our technique will provide more accurate estimation of reservoir parameters, allowing for better forecasting of reservoir performance. Time/Pressure TLS Techniques for Pressure-Transient AnalysisTLS is a general term used to refer to techniques that take into account observational errors in both dependent (e.g., pressure) and independent (e.g., time) variables. Implementation of TLS is interpreted in terms of the orthogonal distances from the data points to the curve. The TLS algorithms minimize this distance. Since TLS combines in a single objective function errors from two different variables, which may have different units, it is necessary to multiply one of the variables by a weight factor. The relative weight between the two variables can be chosen to give more weight to minimize the errors in a particular variable. Furthermore, in traditional pressure-transient analysis, semilog and log-log graphs frequently are used to emphasize certain aspects of the data. TLSbased pressure-transient analysis can be formulated to correspond to the particular graph of choice. The orthogonal distance will be different when the log scaling of either of the axes is changed. For example, TLS regression on the semilog graph is expected to give more emphasis to early-time data. Consequently, there are three options for orthogonal distance regression (ODR) based on the graphs used in well testing-namely, linear p vs. linear t, linear p vs. log t, and log p vs. log t. Other than ODR, it is also possible to interpret TLS as a summation of vertical (pressure) and horizontal (time) errors in a single objective function, referred to here as summed distanc...

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Advances in Computer-Aided Well Test Interpretation

Cited by 34 publications

References 9 publications

Understanding diagnostic plots for well-test interpretation

Understanding diagnostic plots for well-test interpretation

Well Test and PTA for Reservoir Characterization of Key Properties

Significant Improvement in the Accuracy of Pressure-Transient Analysis Using Total Least Squares

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