02-Permeability - Permeability Instructional Objectives: -...

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Permeability 1 Permeability Instructional Objectives: - Learn how permeability is obtained. - Define permeability. - Use an appropriate method to average permeability for various reservoir geometries. - Understand basic core analyses for measuring permeability. - Understand common laboratory problems with the measurement of permeability. - Understand the difference in scale of various permeability measurements. Main sources for permeability estimation - core data - log data, RFT and MDT, and AIT (time-lapse) - well test data - production data Importance of permeability Permeability is an important parameter that controls the reservoir performance. Its importance is reflected by the number of available techniques typically used to estimate it. These different techniques provide formation permeability that represents different averaging volumes. The quality of the reservoir, as it relates to permeability can be classified as follows: k < 1 md poor 1 < k < 10 md fair 10 < k < 50 md moderate 50 < k < 250 md good 250 md < k very good This scale changes with time, for example 30 years ago k < 50 was considered poor. This classification also depends on fluid properties; for example, permeability of 5 md could be very poor for a heavy oil reservoir and could be moderate for a dry gas reservoir. Example Permeability-Porosity Relationship (from Tiab and Donaldson):
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Permeability 2 Factors affecting the magnitude of permeability: - Shape and size of sand grains. - Sorting. - Cementation. - Fracturing and solution. - Lithology or rock type. Definition of Permeability: Permeability is a property of the rock to transmit fluids. As such it is a derived property (like electric resistivity). Permeability can not be measured in the absence of flow. Darcy concluded that () L h h KA q 2 1 = where, q = Flow rate, cm3/sec A = Cross-sectional area, cm2 h 1 - h 2 = Height difference, cm L = Length of column, cm K = Constant of proportionality - 100% water saturated. - K was the “constant” needed to make the equation valid. Darcy’s “ K ” was determined to be a combination of: k , permeability of the sand pack (or rock), and μ , viscosity of the liquid k K = h 1 -h 2 h 1 h 2 L Q A
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Permeability 3 Permeability, k , is a measure of the fluid conductivity of a porous material (analogous to electrical resistivity of a material). Permeability usually correlates with other rock properties such as porosity and saturation. Absolute permeability - the permeability of a porous medium with only one fluid present (single- phase flow). When two or more fluids are present permeability of the rock to a flowing fluid is called effective permeability ( k o , k g , k w ). Relative permeability is the ratio of absolute and effective permeabilities k ro = k o / k , k rg = k g / k , k rw = k w / k . Effective and relative permeability will be discussed in more detail in a later section of this course.
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This note was uploaded on 06/12/2010 for the course PETROLEUM 1500 taught by Professor Ahmedalbamby during the Spring '10 term at University of Texas at Austin.

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02-Permeability - Permeability Instructional Objectives: -...

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