Author: haroonkhan
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Relative Permeability
Except for gases at low pressures, the permeability of a rock is a property of the rock and not of the fluid that flows through it, provided that the fluid saturates 100% of the pore space of the rock. This permeability at 100% saturation of a single fluid is called the absolute permeability of the rock. If…
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Microscopic Displacement Efficiency
The microscopic displacement efficiency is affected by the following factors: interfacial and surface tension forces, wettability, capillary pressure, and relative permeability. When a drop of one immiscible fluid is immersed in another fluid and comes to rest on a solid surface, the surface area of the drop will take a minimum value owing to the…
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Recovery Efficiency
The overall recovery efficiency E of any fluid displacement process is given by the product of the macroscopic, or volumetric displacement, efficiency, Ev, and the microscopic displacement efficiency, Ed: The macroscopic displacement efficiency is a measure of how well the displacing fluid has contacted the oil-bearing parts of the reservoir. The microscopic displacement efficiency is a measure of how well the displacing fluid…
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Introduction
The includes a discussion of the fundamental concepts that influence the displacement of oil and gas both by internal displacement processes and by external flooding processes. It is meant to be an introduction to these topics and not an exhaustive treatise. The reader, if interested, is referred to other works that cover the material.1–5 The reservoir…
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The van Everdingen and Hurst Edgewater Drive Model
Consider a circular reservoir of radius rR, as shown in Fig. 9.6, in a horizontal circular aquifer of radius re, which is uniform in thickness, permeability, porosity, and in rock and water compressibilities. The radial diffusivity equation, Eq. (8.35), expresses the relationship between pressure, radius, and time, for a radial system such as Fig. 9.6, where the driving potential…
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Unsteady-State Models
In nearly all applications, the steady-state models discussed in the previous section are not adequate in describing the water influx. The transient nature of the aquifers suggests that a time-dependent term be included in the calculations for We. In the next two sections, unsteady-state models for both edgewater and bottomwater drives are presented. An edgewater drive…
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Steady-State Models
The simplest model that will be discussed is the Schilthuis steady-state model, in which the rate of water influx, dWe/dt, is directly proportional to (pi – p), where the pressure, p, is measured at the original oil-water contact.5 This model assumes that the pressure at the external boundary of the aquifer is maintained at the initial value pi and that flow to…
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Introduction
Many reservoirs are bounded on a portion or all of their peripheries by water-bearing rocks called aquifers (from Latin, aqua [water], ferre [to bear]). The aquifers may be so large (compared with the reservoirs they adjoin) that they appear infinite for all practical purposes; they may also be so small as to be negligible in their effect on reservoir performance. The…
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Introduction to Pressure Transient Testing
Pressure transient testing is an important diagnostic tool that can provide valuable information for the reservoir engineer. A transient test is initiated by creating a disturbance at a wellbore (i.e., a change in the flow rate) and then monitoring the pressure as a function of time. An efficiently conducted test that yields good data can…
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Superposition in Bounded or Partially Bounded Reservoirs
Although Eq. (8.39) applies to infinite reservoirs, it may be used in conjunction with the superposition principle to simulate boundaries of closed or partially closed reservoirs. The effect of boundaries is always to cause greater pressure drops than those calculated for the infinite reservoirs. The method of images is useful in handling the effect of boundaries. For example,…