This paper investigates some fundamental aspects of a "vaporiser" for recovering trapped retrograde condensate in the formation that is formed during exploitation gascondensate reservoirs in depletion regime. The thermodynamic test of seven different gas-condensate systems and analysis of the liquid and gas phase's samples which were taken under the same thermobaric conditions was provided wide information about the occurrences in the reservoir fluids. It was identified that the solubility capability of gas mixture in the hydrocarbon condensate is elevated and improved as a "vaporiser" if it's critical temperature is increased but compressibility factor and critical pressure are decreased. It was determined that, improving the solubility of gas components in the condensate decreases the system fog up and retrograde condensation pressures and improves stability of aerosol condition of gas-condensate fluid. Therefore, injected gas for gas cycling or re-vaporization of condensate from the core can be controlled for the purpose of increasing its solubility.Keywords: gas-condensate, gas injection, fog up pressure, gas solubility, gas solubility, dissolved gas vaporization of heavy hydrocarbon ends and connate water, the reduction of the condensate/gas ratio and RDP pressure, etc. 12,15 Nevertheless, successful design and implementation of enhanced condensate recovery schemes require accurate prediction of the compositional effects that control the local vaporization/displacement efficiency. In line with these conclusions, and also results which were obtained in the earlier works 4,14,15 in this paper, we intended to find out a way of improving the effectiveness of "vaporiser" for the recovering trapped retrograde condensate in the formation, which is left after primary production. To this purpose, this paper performed an experimental investigation into this phenomenon as it is problematic during mathematical modelling. Investigation method and procedure Laboratory apparatusesExperiments were carried out on a УГК type of PVT bomb, which is a standard apparatus for determining thermodynamic characteristics and the phase behaviour of gas condensate systems. 1 The schematic diagram of the experimental laboratory apparatus and the purposes of the laboratory modules are presented in the Figure 1. The maximum working pressure of the PVT bomb is 45MPa, maximum working temperature is 80°C and cell volume is 3x10 -3 m 3 . As shown in the diagram Figure 1, the laboratory facility can be divided into 9 Modules: Figure 1 Schematic representation of laboratory apparatusModule 1: Module 1 is for handling natural gas from the bottle. It is equipped with Natural Gas Bottle-NGB, CO 2 Bottle-CB, Nitrogen Bottle-NB, Pressure Control Valve-PCV, Flow Meter-FM and normal Isolation Valve-IV. Sample Connection-SC allows the provision of sampling for composition analyses. This module can be linked very easily with Modules 3 and 5 by manifold (Module 9) for recombining gas mixture and gas-condensate system. Module 2:Module 2 is for han...
The work presents results of experimental and analytical investigations enabling to comment on some aspects of phase transformations taking place in natural hydrocarbon systems during the development of deposits. The following issues have been considered:-A new phenomenon in phase transformations of gascondensate systems and its experimental investigation;-Experimental investigation of the influence of different composition gases solubility in hydrocarbonoceous condensates on the exploration of gascondensate pools;-Impact of the porous medium on the evaporability of condensate while affecting it by "dry" hydrocarbon gas. The main text. a) A new phenomenon in phase transformations of gascondensate systems and its experimental investigation. There has been also considered a phenomenon of retrograde condensation and evaporation with its further physical explanation which are of great interest during the development of gascondensate deposits. As has been shown in [1–3, and others], a partial evaporation of the liquid condensate at constant temperature and pressure can be realized by the replacement of the gas phase of the system by gases that are highly soluble in condensate (e.g., "dry" hydrocarbon gas). It has also been shown that the amount of condensate evaporated under the influence of dry hydrocarbon gas increases with pressure, mechanism of this process explains by solubility of gas in liquid. At the same time, one can state that when any liquid is compressed by gas, the critical temperature of which is higher than that of the system, gas molecules are dissolved in the liquid. Consequently, the forces of intermolecular interaction in the liquid are diminished and the liquid evaporates at the temperature, which is lower than the temperature of evaporation of the individual substance . We conditionally distinguish two types of interactions responsible for the evaporation and condensation of the gas-condensate system. In the first case, evaporation (condensation) is a response to changes in thermal characteristics of molecules affected by temperature and pressure of the system. In the second case, the process is related to the dissolution of gas molecules in the liquid. Thus, the retrograde process may be explained as follows. System near point 1 (Fig. 1) is in the gas phase. If we increase pressure at a constant temperature, the system should normally condensate beginning from point 2. In this case, both scenarios will develop. However, the first scenario will be more active, because the liquid contains some gas. As a result, the pressure of the onset of condensation at the given temperature will be higher than the respective value for individual substances. Condensation is accompanied by increase in pressure and the process slows down as point 3 is approached, because the quantity dissolution gas in liquid accelerates with pressure. Condensation ceases already at point 3, because the amount of dissolved gas becomes high enough. At the same time, the intensification of the second type of interaction triggers an anomalously active evaporation of the liquid. Thus, under increasing pressure, the retrograde evaporation continues with the active participation of the second scenario beginning from point 3 and terminates with the complete evaporation of the condensed liquid at point 4. Above this point (including point 5), the system occurs in the one-phase (gas) state.
The conventional equations for describing the flow characteristics of the mixtures merely consider fluid that is homogenic, if it is above the bubble point conditions but ignore that a system containing sub-micron sized gas or vapor bubbles distributed throughout the volume of the liquid, which can exhibit unexpected heterogenic and complex phase properties. In this paper, a new mathematical model for the flowing gas-liquid mixture is presented, which has been proposed considering the colloidal feature of the system above the saturation or bubble point pressure. This approach is more in line with the actual dynamic performance of the oil and gas mixture export pipeline. Experimental data, simulations and field case studies validate the new proposed mathematical model of flow characteristics in pipeline. The obtained results confirmed that the calculated data are in good agreement with the experimental data. Based on Azerbaijan oil-gas-condensate field “Guneshli” data, this new model was used for calculating the condition in which the transformation of the flow characteristics from stable into instable is occurred. It has been discovered that the flow becomes unstable at a pressure about 30% higher than Bubble Point Pressure, which causes pulsation effect in the pipeline structure. However, homogenic behavior should be observed in this hydrodynamic condition. Also, the model provides a guideline on how to optimize the flow rate by adjusting the pipeline parameters to minimize the flow resistance, liquid slugging and hydraulic hammering effects, which cause instable operation.
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