Hw5group6 (1).docx

KKEK4325 Petroleum Engineering Semester 2 2018/2019 Session

Assignment 5 Group 6 Group Members: Mohamad Zaidi Ikram Bin Roslan Muhammad Khairullah Bin Khairuddin Arisya Binti Ahmad Zaini Syed Muzammil Iqbal

KEK150049 KEK150061 KEK150107 KEK130703

Lecturer: Associate Prof. Dr. Badrul Hisham Bin Mohamad Jan

Submission Date: 1st April 2019

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1.0 Introduction There is a difference between the flow of a gas and a liquid through a reservoir. This defiantly affecting the measurement of absolute permeability. As gas flow is less impeded by grain surfaces than liquid flow. Thus, this effect of gas flow being less impeded than liquid flow is considered to be a Klinkenberg Effect. In addition, the difference between gas and water permeabilities is significant not only for solving gas-water two-phase flow problems, but also for quick measurements of permeability using gas as pore fluid. The flow of gas through porous media was investigated by Klinkenberg (1941).

2.0 Klinkenberg Effect Phenomenon Klinkenberg effect is known to be occur when the mean free path of the measuring gas is greater than the diameter of the capillary (pores) through which it is traveling, the random kinetic energy of the gas is transferred to movement of the gas molecule through the capillary or slippage of the molecules occur at the pore walls. This slippage causes the molecules of the gas to travel at a higher velocity in the direction of transfer. This phenomenon is known as Klinkenberg Effect as it causes the measured permeability of a gas to be greater than the absolute permeability of the sample.

This effect is due to slip flow of gas at pore walls which enhances gas flow when pore sizes are very small. Experimental results show (1) that gas permeability is larger than water permeability, (2) that gas permeability increases with increasing pore pressure, and (3) that water permeability slightly increases with increasing pore-pressure gradient across the specimen. The results (1) and (2) can be explained by Klinkenberg effect quantitatively with an empirical power law for Klinkenberg constant. Thus,water permeability can be estimated from gas permeability. The Klinkenberg effect is important when permeability is lower than 10−18 𝑚2 and at low differential pore pressures, and its correction is essential for estimating water permeability from the measurement of gas permeability.

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3.0 Factors Affecting Measured Permeability Values Air permeabilities measured in a routine core analysis laboratory on rock samples from nonfractured reservoirs will give higher values than the actual reservoir permeability. This difference is dependent upon the magnitude of permeability as well as the pore geometry. The higher laboratory values are thought to be caused by gas slippage (the Klinkenberg effect), relative permeability, reactive fluids, and overburdenpressure effects

3.1.1 The Klinkenberg Gas Slippage Effect The flow of gas through porous media was investigated by Klinkenberg(1941). He found that the permeability of a core sample was not constant, but varied withthe gas used to make the measurement, as well as the mean (average) pressure existing inthe core at the time of measurement. His investigations indicated that at low mean pressures-for example, at atmospheric pressure-the gas molecules are so far apart thatthey slip through the pore spaces with little friction loss and yield a higher value of permeability. At higher mean pressures, for example, 1000 psi (6895 kPa) or greater, the gas molecules are closer together and experience a friction drag at the side of the pore walls. This increases as higher mean pressure increases, with the gas acting more and more like a liquid. This means that the measured value of permeability decreases as reservoir or laboratory mean pressure increases.

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JPT November 2013 page 124

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