Gas condensate fluids

Figure 21. Comparisons of experimental and predicted K values for two gas condensate fluids (----), predicted. (A) (O, , A), Data of Hoff-...

The sixth system used for comparison is a gas condensate fluid. Four sets of companion separator samples were collected during the initial flow tests on the producing well, and an experimental phase-distribution test was performed using one set of the samples. The compositions of the recombined wellstream based on the producing gas-oil ratio and the... 

Table VI. Recombined Wellstream Compositions for Produced Gas Condensate Fluid...

Figure 3.20 Comparison of the measured and computed if-values of the GPA gas-condensate fluid at 100 F (from Firoozabadi,...

Components in a gas-condensate fluid contain hydrocarbons from methane, C, ethane, C2, and other hydrocarbons as heavy as or Qo or even heavier. Reservoir crudes may contain hydrocarbons as heavy as C oo- At room temperature (75T) and atmospheric pressure, Cl, C2, C3, and C4 are in the gas state, nC to nC- are in the liquid state, and normal alkanes heavier than nC- are in the solid state. The broad volatility and melting-point range of these hydrocarbon components found in petroleum fluids cause formations of gas, liquid, and solid phases in response to changes in pressure, temperature, or composition. Let us consider a mixture of two hydrocarbons—nC and nC. The melting-point temperature of nC. is 57" C at atmospheric pressure. The solubility of n Cqs in nC at atmospheric pressure is 0.5 mole percent at 14"C. At 40"C and atmospheric pressure, the solubility of nC2R in increases to 12 mole percent. [it is therefore natural that when the temperature falls, heavy hydrocarbons in a crude or even a gas condensate may precipitate as wax crystals. In the petroleum industry, wax precipitation is undesirable because it may plug the pipeline and processing equipment.)... 

Carbon dioxide (CO2) is a very common contaminant in hydrocarbon fluids, especially in gases and gas condensate, and is a source of corrosion problems. CO2 in the gas phase dissolves in any water present to form carbonic acid (H2CO3) which is highly corrosive. Its reaction with iron creates iron carbonate (FeCOg) ... 

The four vertical lines on the diagram show the isothermal depletion loci for the main types of hydrocarbon gas (incorporating dry gas and wet gas), gas condensate, volatile oil and black oil. The starting point, or initial conditions of temperature and pressure, relative to the two-phase envelope are different for each fluid type. 

The initial temperature of a gas condensate lies between the critical temperature and the cricondotherm. The fluid therefore exists at initial conditions in the reservoir as a gas, but on pressure depletion the dew point line is reached, at which point liquids condense in the reservoir. As can be seen from Figure 5.22, the volume percentage of liquids is low, typically insufficient for the saturation of the liquid in the pore space to reach the critical saturation beyond which the liquid phase becomes mobile. These... 

The diagram (Fig. 5.21) shows that as the pressure is reduced below the dew point, the volume of liquid in the two phase mixture initially increases. This contradicts the common observation of the fraction of liquids in a volatile mixture reducing as the pressure is dropped (vaporisation), and explains why the fluids are sometimes referred to as retrograde gas condensates. 

Design Procedure for Shell-Side Condensers and Shell-Side Condensation with Gas Cooling of Condensables, Fluid-Fluid Convection Heat Exchange... 

Petroleum crude oil, gas condensate, and natural gas are generally complex mixtures of various hydrocarbons and nonhydrocarbons with diverse molecular weights. In order to analyze the contents of a petroleum fluid it is a general practice to separate it first into five basic fractions namely, volatiles, saturates, aromatics, resins, and asphaltenes [74, 77]. Volatiles consist of the low-boiling... 

A gas condenses to a liquid if it is cooled sufficiently. Condensation occurs when the average kinetic energy of motion of molecules falls below the value needed for the molecules to move about independently. Thus, the molecules in a liquid are confined to a specific volume by intermolecular forces of attraction. Although they cannot readily escape, liquid molecules remain free to move about within the liquid phase, hi this behavior, liquid molecules behave like the molecules of a gas. The large-scale consequences of the molecular-level properties are apparent. Like gases, liquids are fluid, so they flow easily from place to place. Unlike gases, however, liquids are compact, so they cannot expand or contract significantly. 

Van der Waals sought to address two basic defects of the KMT noninteracting point mass picture (i) neglect of the finite molecular volume that distinguishes molecules from mathematical points and (ii) neglect of the intermolecular attraction that leads to condensation (liquid formation) at sufficiently low temperature. Whereas the ideal gas equation (2.2) exhibits no vestige of condensation phenomena, the Van der Waals equation (2.13) is intended to provide a unified description of gas-liquid ( fluid ) behavior, exhibiting the essential commonality that must be shared by these disparate forms of matter at the molecular level. 

Do not attempt to compare fluid types as defined here with the reservoir descriptions as defined by the state regulatory agencies which have jurisdiction over the petroleum industry. The legal and regulatory definitions of oil, crude oil, gas, natural gas, condensate, etc., usually do not bear any relationship to the engineering definitions given here. In fact, the regulatory definitions are often contradictory. 

Retrograde gases are also called retrograde gas-condensates, retrograde condensate gases, gas condensates, or condensates.1,2 The use of the word condensate in the name of this reservoir fluid leads to much confusion. Initially, the fluid is gas in tire reservoir and exhibits retrograde behavior. Hence, the correct name is retrograde gas. 

Miscible fluid displacement (miscible displacement) is an oil displacement process in which an alcohol, a refined hydrocarbon, a condensed petroleum gas, carbon dioxide, liquefied natural gas, or even exhaust gas is injected into an oil reservoir, at pressure levels such that the injected gas or fluid and reservoir oil are miscible the process may include the concurrent, alternating, or subsequent injection of water. 

Equation (5.40) is good and applicable for film heat-transfer coefficients for gas-phase, vapor-phase, and condensing fluids. The Cp, K, and U isc input values should be accurate for the tube-side fluid being cooled. 

The specific heat value Cp should reference the gas phase for a condensing fluid. 

The third form in which conventional natural gas reserves occur might be called a single-phase fluid, because it is neither a true gas nor a true liquid. It is not a gas or liquid because no surface boundary exists between gas and liquid. Reservoirs of this type are called gas condensate reservoirs, and usually are found in moderately deep formations, have very high pressures, and pose special problems in production and processing. 

Figure 2. Simplified schematic drawing of the extraction plant (1 regenerative pump, 2 fluid cyclone, 3 storage tank, 4 gear pump, 5 circulation gas condensator, 6 diaphragm pump, 7 heat recovery, 8 preheater, 9 heat exchanger, 10 cyclone separator, 11 feed pump, 12 feed preheater, 13 thermostatic chamber)...

The main differences between adsorption from the gas phase and that from liquid phase are as follows [3]. First, adsorption from solution is essentially an exchange process, and hence, molecules adsorb not only because they are attracted by solids but also because the solution may reject them. A typical illustration is that the attachment of hydrophobic molecules on hydrophobic adsorbents from aqueous solutions is mainly driven by their aversion to the water and not by their attraction to the surface. Second, isotherms from solution may exhibit nonideality, not only because of lateral interactions among adsorbed molecules but also because of nonideality in the solution. Third, multilayer adsorption from solution is less common than from the gas phase, because of the stronger screening interaction forces in condensed fluids. 

---