Uncertainty in well test and core permeability analysis

Download
2008
Hapa, Cankat
Reservoir permeability is one of the important parameters derived from well test analysis. Small-scale permeability measurements in wells are usually made using core plugs, or more recently, probe permeameter measurements. Upscaling of these measurements for comparisons with permeability derived well tests (Pressure Build-Up) can be completed by statistical averaging methods. Well Test permeability is often compared with one of the core plug averages: arithmetic, geometric and harmonic. A question that often arises is which average does the well test-derived permeability represent and over what region is this average valid? A second important question is how should the data sets be reconciled when there are discrepancies? In practice, the permeability derived from well tests is often assumed to be equivalent to the arithmetic (in a layered reservoir) or geometric (in a randomly distributed permeability field) average of the plug measures. These averages are known to be members of a more general power-average solution. This pragmatic approach (which may include an assumption on the near-well geology) is often flawed due to a number of reasons, which is tried to be explained in this study. The assessment of in-situ, reservoir permeability requires an understanding of both core (plug and probe) and well test measurements in terms of their volume scale of investigation, measurement mechanism, interpretation and integration. Pressure build-up tests for 26 wells and core plug analysis for 32 wells have valid measured data to be evaluated. Core plug permeabilities are upscaled and compared with pressure build-up test derived permeabilities. The arithmetic, harmonic and geometric averages of core plug permeability data are found out for each facies and formation distribution. The reservoir permeability heterogeneities are evaluated in each step of upscaling procedure by computing coefficient of variation, The Dykstra-Parson’s Coefficient and Lorenz Coefficients. This study compared core and well test measurements in South East of Turkey heavy oil carbonate field. An evaluation of well test data and associated core plug data sets from a single field will be resulting from the interpretation of small (core) and reservoir (well test) scale permeability data. The techniques that were used are traditional volume averaging/homogenization methods with the contribution of determining permeability heterogeneities of facies at each step of upscaling procedure and manipulating the data which is not proper to be averaged (approximately normally distributed) with the combination of Lorenz Plot to identify the flowing intervals. As a result, geometrical average of upscaled core plug permeability data is found to be approximately equal to the well test derived permeability for the goodly interpreted well tests. Carbonates are very heterogeneous and this exercise will also be instructive in understanding the heterogeneity for the guidance of reservoir models in such a system.

Suggestions

Uncertainties in Reservoir limit test results - Effect of input parameters
Altinbay, G.; Akın, Serhat (2015-01-01)
Reservoir parameters from the well test data are essential for reservoir management. Especially the identification the presence of the reservoir boundaries is important for an appraisal well testing. Providing reserve estimation, identifying new well locations and well placement and avoiding dry holes are some important outcomes. However more work on precision of the input data is needed before using the calculated well test parameters. Lots of ambiguity in the results obtained from well tests should be con...
Genetic algorithm for estimating multiphase flow functions from unsteady-state displacement experiments
Akın, Serhat (1998-04-30)
Relative permeability and capillary pressure are the primary flow parameters required to model multiphase flow in porous media. Frequently, these properties are estimated on the basis of unsteady state laboratory displacement experiments. Interpretation of the flood process to obtain relative permeability data is performed by one of two means: application of frontal advance theory or direct computer simulation. Application of frontal advance theory requires a number of experimental restrictions such that th...
Investigation of Porosity and Permeability Impairment in Sandstones by X-ray Analysis and Simulation
Iscan, A. G.; Kök, Mustafa Verşan; Civan, F. (Informa UK Limited, 2009-01-01)
Both porosity and permeability constitute the major parameters in core analysis. In this study, the variation of these two parameters along a sandstone core sample was investigated during formation damage. A water-based drilling fluid was dynamically circulated through the core sample for three different time intervals of 15 min, 45 min, and 60 min at 100 psi circulation pressure. The core sample was analyzed using x-ray digital radiography by sectional image approach. The differences in the porous media du...
Uncertainties in reservoir limit test results : effect of input parameters
Altınbay, Gül; Akın, Serhat; Department of Petroleum and Natural Gas Engineering (2013)
Reservoir parameters from the well test data are essential for reservoir management. Especially the identification the presence of the reservoir boundaries is important for an appraisal well testing. Providing reserve estimation, identifying new well locations and well placement and avoiding dry holes are some important outcomes. However more work on precision of the input data is needed before using the calculated well test parameters. Lots of ambiguity in the results obtained from well tests should be con...
Implementation of noise filtering algorithm for automated pressure transient analysis
Coşar, Doğuhan; Sınayuç, Çağlar; Department of Petroleum and Natural Gas Engineering (2022-9-2)
In order to estimate reservoir parameters such as permeability and skin factor, well tests are performed. Pressures are recorded periodically during these tests. These parameters are crucial in predicting the amount of oil or gas that can be produced. The analysis of pressure changes provide information about the reservoir characteristics and its ability to produce hydrocarbons at a certain amount of time. Three different cases of drawdown tests are analyzed. Derivative curves are plotted using data poin...
Citation Formats
C. Hapa, “Uncertainty in well test and core permeability analysis,” M.S. - Master of Science, Middle East Technical University, 2008.