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Deposits of gas condensate is formed at high pressures and high temperatures and therefore should be found at greater depths that the typical reservoirs of oil and gas. Many gas condensate reservoirs are found in the range of 3000 8000 psia and 200 400 ° F . These gas condensate deposits have a wide range of fluids in their composition.

Once it started to production, reservoir pressure and begins to decline when the pressure dew point, generate the first occurrence of the liquid. As the pressure decreases continuously flowing from the bottom at a constant temperature (in the phase diagram is shown as the line 1-2-3) dropped the percentage of condensate in the reservoir rises to a maximum storage. This process is known as retrograde condensation then the condensate fraction starts to drop, as the pressure continues to decline as a result of the revaporización.

The term retrograde condensation is used to describe the anomalous behavior of a mixture to form a liquid isothermal decrease in pressure or by an increase in temperature isobarito.

Behavior backward region (striped area in Figure No. 3) is defined by a line of quality to produce a maximum with respect to temperature or pressure. Figure 3 shows that for retrograde phenomenon occurs, the temperature should be between the critical temperature and crincondentermica. If the initial condition of the reservoir was represented by 1 point in the phase diagram in Fig. 1, then the decline of pressure during isothermal depletion of the reservoir would continue the line 1-2. Because the initial pressure of the reservoir pressure is above dew point (dew point), the hydrocarbon system exists as a single phase (vapor phase) and remains so during the isothermal pressure decline of 1-2A as the reservoir pressure drops below the point 2, the dew point will be reached and passed and a liquid phase develops at the site. The liquid (dropout9 continue to rise and a peak that occurs between 2-3 points. However, as the pressure declines, the dew point curve can be crossed again. This means that any liquid that was formed, it should be vaporized and will result in a system composed exclusively of steam in the lower dewpoint.

Understanding the phenomenon of flow multifacico, it is important to characterize and develop gas condensate reservoirs. When the pressure falls well below the dew point of the liquid, the drop of the liquid occurs due to retrograde condensation. This results in an increase in liquid saturation, starting from the pit and moving inward reservoir tiempo.Dependiendo depending on the value of the critical condensate saturation (SCC), the liquid phase can be mobile or inmóvil.Aún, If the liquid is stationary, this may reduce the relative permeability to gas, at a magnitude that it is not feasible to understand and measure the fall estimar.A liquid continuous flow produced is poor in as much liquid the heavy components are deposited in the reservoir.

When the liquid saturation exceeds the critical condensate saturation, both the gas phase and liquid phase are movil.El movement of the liquid phase reduces the relative permeability to gas drastically and thus reduces the productivity of the well and the fall of these fluids in the reservoir becomes unrecoverable. Once the liquid is mobile, the composition of the flow produced (GOR) reaches a constant value (greater that the fluid GOR original). The phenomenon of the collapse of the condensate is named and BANK OF CONDENSED these liquids can not be produced or revaporizados even if the pressure of the reservoir was increased by injection of gas until a pressure above the dew point (dew point).
Block condensate
Not all gas condensate deposits are limited by pressure due to the formation of a block of condensate in the region adjacent to the well, although all of these areas have experienced this phenomenon. The extent to which the condensate is segregation or for the production problem, it depends on the relationship between the pressure drop experienced in the field and the total pressure drop that occurs from the remote areas of the site until a control point of surface.

If the pressure drop the reservoir is significant, the additional pressure drop due to the segregation of condensate can be very important to the productivity of the well. This condition is typical of training with a low value of the flow capacity is the product of the permeability of the formation of the net thickness (kh). Conversely, if the site is a small fraction of the total pressure drop, which is normal in formations with high values of kh, the additional pressure drop in the deposit as a result of the block will probably have little impact condensate on productivity of wells. As a general guideline, one can assume that the block of condensed doubles the pressure drop in the deposit for the same flow rate. Conceptually, the flow of gas condensate reservoirs can be divided into three regions of deposits, although in certain situations are not present the three regions.

The two regions closest to a well can be formed when the fund is well below the dew point of the fluid. The third region, which is formed far from the producing wells, exists only when pressure is above deposits point rocio.Esta third region includes most of the area l encentra site is remote from the producing wells. Since the pressure above the dew point, and there is only one phase of hydrocarbon flows: gas. The interior boundaries of this region where the pressure equals the pressure dew point of the original deposit. This limit is not fixed but moves outward as the low pressure oil and produces training falls, finally disappearing brother the pressure outer limit falls below the dew point. In the given region as the region of separation of condensate, the liquid is separated from the gas phase, but the saturation is still low enough to remain motionless, still gas flow SINGLE. The amount of liquid that condenses determined by the characteristics of the fluid phase, as shown in diagram PVT: Saturation of the liquid increases and the gas phase becomes poorer as the gas flows into the well. This saturción at the boundary inside the region are usually close to saturation for the critical fluid flow is the residual oil saturation. In the first region, the closest to a well producing both the flowing gas phase and condensed phase. The saturation of the condensate in this region is greater than the saturation critical dimension of this region ranges from tens of feet to the poor or condensed hundreds of feet to the condensate rich. Its size is proportional to the volume of gas drained and the rate of condensation of liquid. This region extends farther to the well layers as a permeability higher than average since the permeability through the fluid layer has a larger volume of gas. Even in fields containing gas with low condensation of liquid condensate in the block may be significant because the capillary forces can hold a condensate that eventually develops high saturation.

This region corresponds to block condensate in the neighborhood to the well controls the productivity of it. The gas / condensate circulating basically constant and PVT condition is considered a region of constant composition expansion. This condition simplifies the condition between the gas permeability and relative permeability on oil, which makes the relationship between the two is a function of PVT properties, however, the region adjacent to the well is producing effects on permeability because additional the gas velocity and thus the viscous force is extreme. The relationship between the viscous force and capillary force is called the capillary number.

The block condensate indicated by a more pronounced pressure gradient near the well with test times more prolonged the effective permeability of gas away from the well dominates the response, the permeability can be determined to give birth to the curve of the resulting change pressure in a double logarithmic graph of changes PSEUDO - PRESION and closing time is extended if the test time and test the time of closure depends on the permeability of the formation properties of the flow away from the well will be evident.