miscible displacement processes
DESCRIPTION
paper about miscible displacement processesTRANSCRIPT
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MISCIBLE DISPLACEMENT
PROCESSES
TM-6012
ENHANCED OIL RECOVERY
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OUTLINE
Introduction
General Description
Principle of Phase Behavior
First-Contact Miscible Process
Multiple Contact Miscible Process
Fluid Properties
Factors Affecting Displacement Efficiency Of Miscible Process
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INTRODUCTION
Definition
Processes where the effectiveness of
the displacement results primarily from
miscibility between the oil in place and
the injected fluid
Displacement processes:
First-Contact Miscible (FCM)
Multiple-Contact Miscible (MCM)
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PRINCIPLES OF PHASE BEHAVIOR
Pressure/ Temperature Diagrams
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PRINCIPLES OF PHASE BEHAVIOR
Pressure/ Composition Diagram Illustrating
Isothermal Compression
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PRINCIPLES OF PHASE BEHAVIOR
Pressure/ Composition Diagram Illustrating Isothermal Compression
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FIRST CONTACT MISCIBLE
PROCESS
FCM process normally consists of injecting a relatively small primary slug that is miscible
with the crude oil, followed by injection of a
larger, less expensive secondary slug
Ideally, the secondary slug should be miscible with the primary slug. In contrary,
then a residual saturation of the primary slug
material will be trapped in the displacement
process
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FIRST CONTACT MISCIBLE PROCESS
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FIRST CONTACT MISCIBLE PROCESS
A basic concern in the design of a process is the phase behavior between the primary slug and the
crude oil and between the primary slug and the
secondary slug fluid that displaces the primary slug
When the reservoir temperature is above the critical temperature of the primary-slug solvent, the
pressure required for complete miscibility between
the slug solvent and the reservoir oil becomes more
difficult to estimate
Under these conditions, the solvent cannot be liquefied and pressure must be above the
cricondenbar
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MULTIPLE CONTACT MISCIBLE
PROCESS
The condition of miscibility is generated in the reservoir through in-situ composition
changes resulting from multiple contacts and
mass transfer between reservoir oil and
injected fluid
MCM processes are classified as vaporizing-gas (lean-gas) displacement, condensing and
condensing/vaporizing-gas (enriched-gas)
displacements, and CO2 displacements.
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MULTIPLE CONTACT MISCIBLE PROCESS
Vaporizing-gas process
The injected fluid is generally a relatively lean gas ( it contains mostly methane and
other low molecular-weight hydrocarbons)
The composition of the injected gas is modified as it moves through the reservoir
so that it becomes miscible with the original
reservoir oil.
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MULTIPLE CONTACT MISCIBLE PROCESS
Development of
miscibility
Miscibility does not
develop
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MULTIPLE CONTACT MISCIBLE PROCESS
Condensing and Condensing/Vaporizing-Gas
(Enriched-Gas) Displacement Process
The injected fluid contains significant amounts of intermediate components (C2
through C6) rather than being a dry gas.
The process depends on the condensation of these components into the reservoir oil,
thereby modifying the oil composition
The modified oil then becomes miscible with the injected fluid
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FLUID PROPERTIES
The performance of a miscible displacement process depends on fluid physical properties that affect flow behavior in a reservoir
The properties influence the performance are:
Fluid Density
Fluid Viscosity
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FLUID PROPERTIES
Fluid Density
Knowledge of the relative densities of the fluids and fluid mixture is important for the process design
The result in displacement process can be gravity override, underride, or fingering
Fluid Viscosity
Mobility ratio in a displacement process is a direct function of the viscosities and relative permeabilities of displaced and displacing fluids
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Displacement Efficiency in a miscible process is less than 100%
The magnitudes of the efficiencies depend on a number of factors, including whether a displacement
is conducted as a secondary or tertiary process
In Secondary recovery, it is assumed that there is no mobile water unless water is injected as a part of the
process
In Tertiary recovery, both oil and water will be displaced and will be mobile
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Microscopic Displacement Efficiency (No Mobile Water)
The Interfacial Tension (IFT) between displacing (solvent) and displaced (oil) phases. If IFT is zero, then residual saturation in portions of the rock contacted by the displacing phase would be essentially zero
Dispersion and mixing at the microscopic level, combined with the associated phase behavior, are the major reasons that microscopic displacement efficiencies in MCM process in the absence of water are not 100%
Efficiency typically ranges from 90% to 97%
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Macroscopic Displacement Efficiency
(No Mobile Water)
Four major factors affect recovery efficiency at
the macroscopic level in a miscible process
Mobility ratio
Viscous fingering
Gravity segregation
Reservoir heterogeneity
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Effect of Mobility Ratio
The viscosity of miscible solvents are typically small (
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Effect of Viscous Fingering
An adverse viscosity ratio in a miscible process results in viscous fingering, which
leads to reduced volumetric sweep
Effective viscosity ratio, E, that characterizes the effect of viscous fingering:
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
In the FCM process, the oil recovery was delayed because of the adverse mobility ratio
(early breakthrough of injecting fluid)The
ultimate recovery approached 100%
In the MCM process, the recovery leveled off, the final recovery would not approach 100%.
The viscous fingering not only delay the oil
recovery but also reduce total recovery.
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Effect of Gravity
A dimensionless group used to characterize
gravity effects is the viscous/gravity ratio, Rv/g
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Vertical sweep efficiency
at breakthrough as a
function of the ratios of
viscous/gravity forces,
linear system
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FACTORS AFFECTING DISPLACEMENT
EFFICIENCY OF MISCIBLE PROCESS
Displacement Efficiency When Mobile Water is Present
The presence of a water phase, flowing or stagnant, has no significant effect on phase behavior in either an FCM process or an MCM process
Miscibility is developed in basically the same manner whether water is present or not
The presence of flowing water has relatively small negative effect on displacement efficiency, but it blocks part of the oil away from the solvent, so it reduce the ability of the solvent to contact and mobilize the oil
It both occurs in FCM and MCM processes