On reservoir rocks

The above experiment was conducted for a single fluid only. In hydrocarbon reservoirs there is always connate water present, and commonly two fluids are competing for the same pore space (e.g. water and oil in water drive). The permeability of one of the fluids is then described by its relative permeability (k ), which is a function of the saturation of the fluid. Relative permeabilities are measured in the laboratory on reservoir rock samples using reservoir fluids. The following diagram shows an example of a relative permeability curve for oil and water. For example, at a given water saturation (SJ, the permeability... 

Field analogues should be based on reservoir rock type (e.g. tight sandstone, fractured carbonate), fluid type, and environment of deposition. This technique should not be overlooked, especially where little information is available, such as at the exploration stage. Summary charts such as the one shown in Figure 8.19 may be used in conjunction with estimates of macroscopic sweep efficiency (which will depend upon well density and positioning, reservoir homogeneity, offtake rate and fluid type) and microscopic displacement efficiency (which may be estimated if core measurements of residual oil saturation are available). 

By 1980, research and development shifted from relatively inexpensive surfactants such as petroleum sulfonates to more cosdy but more effective surfactants tailored to reservoir and cmde oil properties. Critical surfactant issues are performance in saline injection waters, adsorption on reservoir rock, partitioning into reservoir cmde oil, chemical stabiUty in the reservoir, interactions with the mobiUty control polymer, and production problems caused by resultant emulsions. Reservoir heterogeneity can also greatly reduce process effectiveness. The decline in oil prices in the early 1980s halted much of the work because of the relatively high cost of micellar processes. 

Microbes adsorb and grow on reservoir rock surfaces fed by injected nutrients (271) and may have appHcation in plugging thief zones near injection... 

To establish the well drainage boundaries and fluid flow patterns within the TFSA-waterflood pilot, an interwell chemical tracer study was conducted. Sodium thiocyanate was selected as the tracer on the basis of its low adsorption characteristics on reservoir rocks (36-38), its low and constant background concentration (0.9 mg/kg) in produced fluids and its ease and accuracy of analysis(39). On July 8, 1986, 500 lb (227 kg) of sodium thiocyanate dissolved in 500 gal (1.89 m3> of injection brine (76700 mg/kg of thiocyanate ion) were injected into Well TU-120. For the next five months, samples of produced fluids were obtained three times per week from each production well. The thiocyanate concentration in the produced brine samples were analyzed in duplicate by the standard ferric nitrate method(39) and in all cases, the precision of the thiocyanate determinations were within 0.3 mg/kg. The concentration of the ion in the produced brine returned to background levels when the sampling and analysis was concluded. 

Adhesive force, non-Brownian particles, 549 Admicelle formation, 277 Adsorption flow rate, 514 mechanism, 646-647 on reservoir rocks, 224 patterns, on kaolinite, 231 process, kinetics, 487 reactions, nonporous surfaces, 646 surface area of sand, 251 surfactant on porous media, 510 Adsorption-desorption equilibria, dynamic, 279-239 Adsorption plateau, calcium concentration, 229... 

Carbon Sequestration Study on the potential of COj storage in the "Kempen "-Flanders a study on the influence of super critical COj on reservoir rocks and participation to the European project RECOPOLforthe enhanced coal bed methane extraction. 

From the above discussion, it is seen that the long-term performance of a geothermal reservoir depends on reservoir rock porosity, recharge, and... 

Adsorption of surfactant on reservoir rock can be determined by static tests (batch equilibrium tests on crushed core grains) and dynamic tests (core flood) in the laboratory. The units of surfactant adsorption in the laboratory can be mass of surfactant adsorbed per unit mass of rock (mg/g rock), mass per unit pore volume (mg/mL PV), moles per unit surface area (peq/m ), and moles per unit mass of rock (peq/g rock). The units used in field applications could be volume of surfactant adsorbed per unit pore volume (mL/mL PV) or mass per unit pore volume (mg/mL PV). Some unit conversions follow ... 

Retention in Porous Media. Anionic surfactants can be lost in porous media in a number of ways adsorption at the solid—liquid interface, adsorption at the gas—liquid interface, precipitation or phase-separation due to incompatibility of the surfactant and the reservoir brine (especially divalent ions), partitioning or solubilization of the surfactant into the oil phase, and emulsification of the aqueous phase (containing surfactant) into the oil. The adsorption of surfactant on reservoir rock has a major effect on foam propagation and is described in detail in Chapter 7 by Mannhardt and Novosad. Fortunately, adsorption in porous media tends to be, in general, less important at elevated temperatures 10, 11). The presence of ionic materials, however, lowers the solubility of the surfactant in the aqueous phase and tends to increase adsorption. The ability of cosurfactants to reduce the adsorption on reservoir materials by lowering the critical micelle concentration (CMC), and thus the monomer concentration, has been demonstrated (72,13). 

The molecular structure of surfactants controls not only the concentration of the surfactants at the interface and the resulting reduction in surface/interfacial tensions, but also affects the orientation of the molecules at the interface. The hydrophilic group is either ionic in nature or highly polar. Based on the nature of the polar group, surfactants can be classified as anionic, cationic, non-ionic or amphoteric. Among these types, anionic and non-ionic surfactants are preferably employed in enhanced oil recovery processes (EOR) due to their low adsorption on reservoir rocks. Therefore, these surfactants are briefly described. 

In chemical flooding processes for enhanced oil recovery, alkaline chemicals can be useful for hardness ion suppression or removal, reaction with acidic crude oils to generate surface-active species, reduction in surfactant adsorption on reservoir rock surfaces, changes in interfacial phase properties, mobility control and increased sweep efficiency, oil wettability reversal and increased emulsification. 

The interaction of inorganic species, such as those of calcium and aluminum that are normally present in reservoir fluids, with surfactants is found to produce precipitation of the surfactants followed by their redissolution above the critical micelle concentration. A maximum is often observed in the adsorption isotherm of surfactants on reservoir rocks. The contribution of the surfactant precipitation/dissolution phenomenon to the occurrence of adsorption maximum has been investigated in this study using the kaolinite/sulfonate system. The magnitude of the adsorption maximum is found to be minimized when the precipitation/redissolu-tion of the surfactant is taken into account, suggesting the important role of the latter phenomenon in determining the apparent adsorption. 

As a final result, it has been proven that the adsorption of polyacrylamides on reservoir rocks depends to a great extent on the wettability. In all probability no difference occurs whether the intermediate or oil-wet character of the rock surface is a result of adsorbed monolayer or thick oil film. A certain parallelism can be observed between the adsorption of polyacrylamides and methylene blue on a rock surface. By this far-reaching analogy a new methodological possiblity for semi-quantitative determination of the wetting character in reservoir rock is afforded, using the polymer adsorption (29) similar to the dye adsorption method of Holbrook and Bernard (28). 

A general criticism directed at mobility control agents has been their adsorption on reservoir rock. Data on a few specific types, misapplied to polymers in general, has resulted in some confusion. Polymers do adsorb, but the quantity varies widely from one polymer to another. It is, therefore, necessary to quantify adsorption for a specific polymer before its flow behavior can be accurately predicted. 

A.6 IMPORTANCE OF HETEROGENEOUS CATALYTIC REACTIONS ON RESERVOIR ROCK SURFACES... 

Our experience in treating terrigenous and carbonate reservoirs in 22 wells shows that the heating rate due to a thermochemical process depends both on the relative amounts of chemicals utilized and the reservoir rock. We attribute this observation to heterogeneous catalysis on reservoir rock surfaces. This conclusion is consistent with the results of studies of catalytic down hole upgrading (e.g., see review in Ref [8]). 

The main title Physical Properties of Rocks and parts of the two books look similar. The first mission of Physical Properties of Rocks— Fundamentals and Principles of Petrophysics —and also of this second edition—is the description of the physics behind rock properties and the different influences and correlations between physical and geological properties of rocks. This book has the character of a textbook. On the other hand, Physical Properties of Rocks—A Workbook is directed on the application of the presented experimental data and empirical and theoretical equations (therefore the name workbook ) and focused on reservoir rocks. 

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