Characteristics of reservoirs

Conventionally, the sample is initially saturated with one fluid phase, perhaps including the other phase at the irreducible saturation. The second fluid phase is injected at a constant flow rate. The pressure drop and cumulative production are measured. A relatively high flow velocity is used to try to negate capillary pressure effects, so as to simplify the associated estimation problem. However, as relative permeability functions depend on capillary number, these functions should be determined under the conditions characteristic of reservoir or aquifer conditions [33]. Under these conditions, capillary pressure effects are important, and should be included within the mathematical model of the experiment used to obtain property estimates. 

Table II. Range of Characteristics of Reservoirs in the Gilwood and Beaverhill Lake Formations...

Not all petroleum reservoirs can be exploited successfully by the in situ combustion method. The applicability of this method depends on such factors as depth to the oil reservoir, thickness of the oil-bearing bed, amount of oil in place within the reservoir, degree of water saturation of the petroliferous formation, specific gravity of the crude and its fractional composition, reservoir pressure, geological type of the oil trap, physical characteristics of reservoir rocks, and the initial oil recovery factor prior to fire flooding. All of these factors must be thoroughly studied before it is decided to apply the in situ combustion method. 

From the point of view of flow characteristics of reservoir fluids, the wettability in the reservoir is of primary importance. It seems to be established, on the basis of the fundamental works of Brown and Fatt (30), Johansen and Dunning (31), Owens and Archer (32), Mungan (33), and Salathiel (34) that the wettability in a reservoir is of heterogeneous character, that is, the small pores and consolidation points are water wet, while the inner surface of the large pores are oil wet. As a result of this, it may be expected that the sorption distribution of the polymer injected into the reservoir will likewise be characterized by heterogeneity. 

Wyllie, M.R.J., Rose, W.D., 1950. Some theoretical ctmsiderations related to the quantitative evaluation of the physical characteristics of reservoir rock from electrical log data. J. Pet. Technol. 2, 189. April. 

The characteristics of the pore system in reservoir rocks is important for the understanding of the flow of liquids through the rocks, particularly in relation to the recovery of hydrocarbons. Commonly used methods in the assesment of these characteristics of reservoir rocks are optical microscopy of thin sections and measurements of total porosity by mercury dilatometry and of air or liquid permeabilities. 

With a few exceptions reservoir rocks are sediments. The two main categories are siliciclastic rocks, usually referred to as elastics or sandstones , and carbonate rocks. Most reservoirs in the Gulf of Mexico and the North Sea are contained in a clastic depositional environment many of the giant fields of the Middle East are contained in carbonate rocks. Before looking at the significance of depositional environments for the production process let us investigate some of the main characteristics of both categories. 

There exists an important relationshiphetween the depositional environment, reservoir distribution and the production characteristics of a field (Figure 5.3). 

This behaviour is characteristic of thennodynamic fluctuations. This behaviour also implies the equivalence of various ensembles in the thermodynamic limit. Specifically, as A —> oo tire energy fluctuations vanish, the partition of energy between the system and the reservoir becomes uniquely defined and the thennodynamic properties m microcanonical and canonical ensembles become identical. 

The composition of natural gas at the wellhead depends on the characteristics of the reservoir and is highly variable with respect to both the constituents present and the concentrations of these constituents. Compositions of various natural gases are given in Table 4. 

In addition to the mobihty control characteristics of surfactants, critical issues in gas mobihty control processes are surfactant salinity tolerance, hydrolytic stabihty under reservoir conditions, surfactant propagation through the reservoir, and foam stabihty in the presence of cmde oil saturations. 

Thermal stabihty of the foaming agent in the presence of high temperature steam is essential. Alkylaromatic sulfonates possess superior chemical stabihty at elevated temperatures (205,206). However, alpha-olefin sulfonates have sufficient chemical stabihty to justify their use at steam temperatures characteristic of most U.S. steamflood operations. Decomposition is a desulfonation process which is first order in both surfactant and acid concentrations (206). Because acid is generated in the decomposition, the process is autocatalytic. However, reservoir rock has a substantial buffering effect. 

Pressure at the pulsing device and the conditions for cavitation and water hammer may be estimated by the methods of Wilhams and Little [Trans. Jnst. Chem. Eng. (London), 32, 174 (1954)] provided the pressure-drop characteristics of the tower internals are known. Jealous and Johnson (loc. cit) have had good success in computing the power required for pulsing. Since power requirement alternates, the use of a flywheel on the pulse mechanism to act as an energy reservoir is suggested as a means of reducing power requirements. Alterna-... 

The main problem of elementary chemical reaction dynamics is to find the rate constant of the transition in the reaction complex interacting with its environment. This problem, in principle, is close to the general problem of statistical mechanics of irreversible processes (see, e.g., Blum [1981], Kubo et al. [1985]) about the relaxation of initially nonequilibrium state of a particle in the presence of a reservoir (heat bath). If the particle is coupled to the reservoir weakly enough, then the properties of the latter are fully determined by the spectral characteristics of its susceptibility coefficients. 

When the characteristic time of vibrational relaxation is much shorter than tr, the rate constant is independent of Zy. For molecules consisting of not too many atoms, the inequality (2.58) is not fulfilled. Moreover, Zy may even become larger than tr. This situation is beyond our present consideration. The total set of resonant sublevels partaking in RLT consists of a small number of active acceptor modes with nonzero matrix elements (2.56) and many inactive modes with Vif = 0. The latter play the role of reservoir and insure the resonance = f. 

This treatment of the carbon cycle is intended to give an account of the fundamental aspects of the carbon cycle from a global perspective. After a presentation of the main characteristics of carbon on Earth (Section 11.2), four sections follow 11.3, about the carbon reservoirs within the atmosphere, the hydrosphere, the biosphere... 

Johnston TA, Bodaly RA, Matias JA. 1991. Predicting fish mercury levels from physical characteristics of boreal reservoirs. Can J Fish Aquat Sci 48 1468-1475. 

The state of the art in chemical oil recovery has been reviewed [1732]. More than two thirds of the original oil remains unrecovered in an oil reservoir after primary and secondary recovery methods have been exhausted. Many chemically based oil-recovery methods have been proposed and tested in the laboratory and field. Indeed, chemical oil-recovery methods offer a real challenge in view of their success in the laboratory and lack of success in the field. The problem lies in the inadequacy of laboratory experiments and the limited knowledge of reservoir characteristics. Field test performances of polymer, alkaline, and micellar flooding methods have been examined for nearly 50 field tests. The oil-recovery performance of micellar floods is the highest, followed by polymer floods. Alkaline floods have been largely unsuccessful. The reasons underlying success or failure are examined in the literature [1732]. 

The resulting model would therefore consist of component balance equations for the soluble component written over each of the many solid and liquid subsystems of the packed bed, combined with the component balance equation for the coffee reservoir. The magnitude of the recirculating liquid flow will depend on the relative values of the pressure driving force generated by the boiling liquid and the fluid flow characteristics of the system. 

Reservoir devices, as the name implies, are characterized by a core of drug, the reservoir, surrounded by a polymeric membrane. The nature of the membrane determines the rate of release of drug from the system. A schematic description of this process is given in Fig. 4, and characteristics of the system are listed in Table 3. 

Each interaction involves numerous chemical processes. The dominance of a specific interaction depends on the type of waste, the characteristics of the brine and rock in the reservoir, and environmental conditions. Table 20.14 describes some of the more common processes that may result in incompatibility. 

A pipeline network is a collection of elements such as pipes, compressors, pumps, valves, regulators, heaters, tanks, and reservoirs interconnected in a specific way. The behavior of the network is governed by two factors (i) the specific characteristics of the elements and (ii) how the elements are connected together. The first factor is determined by the physical laws and the second by the topology of the network. 

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. 

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. 

Because of the highly unstable nature of the acid attack in most of the carbonate reservoirs (propagation of wormholes), the development of a descriptive model of the skin evolution was not possible until the recent advent of the theory of fractals. In addition, the characteristics of the damaged zone greatly affect the behavior of the skin during acid injection in any type of reservoir, but particularly in carbonate ones. 

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