Thermodynamics of a Petroleum Reservoir System
1. Feasible to apply the classical thermodynamics principle to a complete ‘petroleum reservoir system’ (physical entity) that is composed of two distinct parts namely ‘solid-grains’ and ‘pore-spaces’ - in the presence of a specified ‘reservoir boundary’ that keeps exchanging the fluid mass and heat fluxes with its surroundings?
2. Feasible to precisely specify energy exchanges associated either with surrounding aquifers; or, upon injection of water/gas/chemicals; or, upon hydrocarbon extraction (volume changes of water, oil & gas upon the work done by pressure) - as a function of exchanges in reservoir pore-fluids, if the reservoir boundaries become mobile, porous & diathermic?
3. Prior to any drilling/puncturing of a reservoir, it is easy to conceptualize that the reservoir would be under steady-state condition pertaining to the state of thermodynamic equilibrium, whereby the petroleum reservoir system would return to its previous stead-state condition following any infinitesimal disturbance with respect to its reservoir boundaries. If so, how exactly thermodynamic equilibrium gets disturbed (a) upon commencing hydrocarbon production (when making use of elastic storage of energy during primary production); (b) upon injecting water/gas (2ry recovery); and (c) upon injecting chemicals (chem EOR)?
Which ONE of them could be considered as a quasi-static transformation?
4. Although, fluid phases via water, oil and gas refer to the entirety of intensive properties such as reservoir pressure and temperature; and fluid density, how do such intensive properties (potentials) intervene in conjunction with corresponding extensive rock property such as permeability (which keeps varying as the size of the reservoir keeps increasing)?
5. When exactly the concept of ‘internal energy’ (as a function of ‘intra-atomic cohesive energy’, ‘inter-atomic cohesive energy’, ‘inter-molecular cohesive energy’ on top of ‘kinetic energy’) becomes very sensitive in case of a ‘petroleum reservoir system’ – with reference to ‘potential energy’ (as a function of datum, mass and acceleration of gravity) and ‘kinetic energy’ (as a function of mass, moment of inertia and the speed of the system)?
6. Can we theoretically apply first law of thermodynamics to a closed petroleum reservoir system, where, an exact balance is established between the variation of the total energy of the reservoir system upon hydrocarbon production, and the total work, and with the quantities of heat absorbed by the petroleum reservoir system – in the absence of explicitly specifying the distribution of energy exchanges upon hydrocarbon production (and only the total energy exchange)?
7. Whether ‘entropy’ would keep on increasing - upon hydrocarbon production - until its abandonment?
Whether any petroleum reservoir’s entropy has stabilized itself @ maximum value by achieving equilibrium condition following hydrocarbon production?
Hello,
The questions you ask are at the heart of all materials problems and in all fields. They are far ahead of the usual paradigms. The answers I propose are based on experimental evidence and are expressed by an equation of state for materials. They apply to seismic phenomena and should allow to predict rock fractures.
1. Is it possible to apply the principle of classical thermodynamics to a complete "petroleum reservoir system" (physical entity) composed of two distinct parts, namely the "solid grains" and the "pore spaces", ......
Effectively, the reservoir reaches a limit at which additional internal energy is transformed with entropy jumps and heat dissipation.
2. Is it possible to precisely specify the energy exchanges associated with either the surrounding aquifers or the injection of water, gas or chemicals, or the extraction of hydrocarbons .....
Yes. Energy exchanges depend on viscosity in interfaces, internal energy of constituents, interfacial energy, and velocity of interfaces.
3. Before any drilling or perforation of a reservoir, it is easy to conceive that the reservoir is in a state of thermodynamic equilibrium, ...../
The state of thermodynamic equilibrium before drilling can be known by analysis of rocks taken under specific conditions.
The elastic storage of energy during primary production is measurable.
The effect of recovery fluids on internal energy is measurable.
The effect of chemicals on internal energy is measurable.
4. Although fluid phases (water, oil and gas) refer to the set of intensive properties such as reservoir pressure and temperature and fluid density, how do these intensive properties (potentials) ......
The intensive properties of the fluid phases are related to the potential at the zero zeta of the interfaces, to the polarity of the fluid molecules. The interfacial fields depend on the particle size, the size and the density of the majority defects and are realized by charge transfers and internal energy changes. The velocity of the fluid in the interfaces is an important factor.
5. When exactly does the concept of "internal energy" (as a function of "intra-atomic cohesive energy", "inter-atomic cohesive energy", "inter-molecular cohesive energy" in addition to "kinetic energy") become ......
The components of "intra-atomic cohesion energy", "inter-atomic cohesion energy", "inter-molecular cohesion energy" in addition to "kinetic energy" are measurable. This energy starts to transform when the internal energy reaches its maximum value. Either the initial state of the rock is maximal before drilling and its transformation rate is very sensitive to the applied stress, or it is lower than this value. In this case it is necessary to wait for the energy supplied to the system to make up the difference and the cracking of the rock is delayed. The transformation depends on the energy, the energy density of the rate of deformation and the speed of the volume that is transformed. The rate of transformation decreases with the rate of transformation. All these parameters are measurable.
6. Can we theoretically apply the first law of thermodynamics to a closed system?
The first law is not enough, otherwise the transformation would not take place.
7. Would the "entropy" continue to increase...
The entropy increases only during the phase before the transformation; then it decreases while the applied stress becomes more and more compressive in the constrained volume whose Young's modulus decreases. In the phase of decrease the bonds break in a progressive way and there is fragmentation more and more slowly. When the internal stress reaches its explosive value, all the bonds break simultaneously
To characterize the system it is necessary to measure the constrained volume, its energy density and its internal energy, its deformation site, its transformation speed and the transformation speed of its energy.
Regards
Claude LE GRESSUS
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