Como determinar a pressão do ponto de bolha de um fluido reservatório?

Experimentally taking the fluid samples (PVT) data to get the bubble point pressure. Or using correlations such as : Standing-Katz Chart or Standing's Correlation.

Presión a la cual el crudo líquido libera la primera burbuja de gas previamente disuelto en él. Se denota como: Pb, también se le conoce cómo Presión de Saturación.

In my experience bubble point is more faster done on clear oil and it’s very important to be done on the product of hydrocarbons for safety reasons.

Una de las importancias del uso de los completamientos inteligentes es el monitoreo de los parámetros de producción en tiempo real para evitar llegar al punto de burbuja del yacimiento.

Boiling point: when a liquid got to turn into gas , due to a higher temperature and pressure.

Because it determines when the reservoir transitions from a single or two phase state to a three phase (+gas) state, see, for instance Lake 87. Note that when this happens depends on the pore structure of the reservoir rock, determining the local capillary pressure. Thus, the process starts in the rocks with the largest pores or within fractures and voids, gradually spreading into finer grained facies.

It's a crucial property for the reservoir. Because it determines the reservoir energy and drive mechanism. Also determine the reservoir type and estimate productivity through the production performance .

The appearance of the gas phase happens when the pressure becomes lower than the bubble pressure at the reservoir temperature. Gas bubbles will occupy pore spaces, at a saturation below the minimum requierd to flow due to capillary pressure. The inmobile gas will be an obstacle for the oil flow: the relative permeability to oil being lower than the total permeability. Further descent in pressure will result in increase in gas saturation to a point when it will flow. The oil phase permeability will still be lower, the oil viscosity will increase as it looses gas; both effects are against the flow of oil. Then the reservoir will loose gas, which means a descent of its energy. Therefore oil reserves may decrease at pressure below bubble point.

El control de la presión de fondo fluyente por encima de la presión de burbuja en yacimientos subsaturados resulta vital en el ciclo de vida productiva del pozo y en la mayor recuperación de reserva posible. La toma de decisiones oportuna en superficie para su control define la optimización de este ciclo de vida. La importancia de entender el comportamiento de los fluidos es primordial para que los proyectos sean rentables. A nivel de yacimiento esto se traducirá en utilizar eficientemente la energía natural del mismo para maximizar la extracción de la reserva. Mientras que, a nivel superficial, el adecuado dimensionamiento de las instalaciones y la máxima recuperación de líquidos serán el resultado de este entendimiento.

The bubble point pressure plays a significant role in estimating reservoir productivity and designing production strategies. In an undersaturated reservoir, maintaining the pressure above the bubble point can lead to higher oil production rates and better recovery efficiency. Additionally, understanding how the bubble point relates to the reservoir's pressure and temperature conditions can help in optimizing well completions and production operations to maximize output.

McCain et al. (in their book “Petroleum Reservoir Fluid Property Correlations”) compared the accuracy of several correlations available for Pb estimation. Some of their interesting findings: • They proposed Valko-McCain (2003) correlation as the best correlation. (doi: 10.1016/S0920-4105(02)00319-4.) • Regarding the correlations more popular in the industry, Standing and Lasater showed better prediction results. • The average absolute relative errors are approximately the same for different geographical datasets. They concluded that regional correlations are not necessary for Pb.

En la Literatura existen diversas correlaciones para las distintas propiedades PVT, entre ellas la Presión de burbuja (Pb). Casi todas requieren la misma data, pero los resultados no son necesariamente similares, dado que estas son ecuaciones empíricas desarrolladas para adaptaciones a condiciones específicas. Lo recomendable es contar con data real de campo (un análisis PVT) que permita determinación de un valor de Pb real de un yacimiento y compara estas correlaciones con este valor. También es recomendable conocer los rangos de aplicación de las correlaciones

PVT application for the estimation of bubble point pressure is an effective means that doesn't only give the variables but also helps describe the properties of the fluid as a result of the changes in variables such as pressure, temperature, and volume.

During the PVT test, the fluid is driven to a repeatable equilibrium end-point condition through agitation or stirring. In a coreflood experiment with depressurization, the fluid isn’t agitated or stirred. As a result, with some live oils, it is possible during a coreflood test for gas to stay in solution for some time when pressure is somewhat below the PVT-defined bubble point pressure. This condition contributes to experimental mis-interpretation of critical gas saturation, relationship between critical gas saturation and depressurization rate, and fluid saturations after depressurization steps.

Exactly from the plot of a relative volume versus pressure by conducting a CCE test You can read the bubble pressure directly from the plot where the relative volume equals to 1.

While PVT analysis is a powerful tool for estimating bubble point pressure, the accuracy of the results heavily depends on the integrity of the fluid sample from the point of sampling to analysis in the lab. Use of downhole sampling and maintaining reservoir conditions during sampling and transport can mitigate these errors. If the sample has flashed, recombination experiments based on separator gas and liquid can be used to recreate the reservoir fluid for PVT analysis. Rigorous quality control in laboratory procedures is necessary to ensure the reliability of the results. This includes cross-checking with other reservoir data when possible.

El análisis PVT tiene varias pruebas, concretamente para efectos de la determinación de la presión de burbuja (Pb) se utiliza la Liberación Instantánea. En este caso se tiene la muestra a una determinada presión superior al valor de Pb (masa en estado totalmente líquido). Se determina el volumen de la muestra. Se hacen sucesivas disminuciones de presión, y se registran los volúmenes en cada caso, se procede a graficar Presión vs Volumen, y el valor de presión donde se observa el cambio de pendiente corresponde al valor de Pb. Existe una función (denominada función Y) que se utiliza para corregir este valor, en caso de sobreestimación o subestimación del valor de Pb, y utiliza los mismos datos del análisis

The saturation pressure can be estimated by going through the below steps. - Split up the plus fraction in carbon number fractions. - Assign a critical temperature, a critical pressure and an acentric factor to each component and carbon number fraction. - Use an equation of state (Soave-Redlich-Kwong or Peng-Robinsen) to estimate the saturation pressure. Several commercial PVT software packages exist that can carry out the above steps.

Reservoir fluids, a complex mix of organic molecules, undergo a detailed analysis called crude assay. This assessment yields crucial data on properties. Using a simulation package, we model the bubble point based on reservoir pressure and temperature for enhanced reservoir understanding in petroleum engineering.

Los softwares de simulación utilizan mayormente 2 modelos de fluidos: el de petróleo negro (correlaciones PVT) o el composicional (ecuaciones de estado). Los de petróleo negro requerirían conocer que correlación aplica en el caso a simular, en tanto que el composicional requiere un análisis cromatográfico a fin de determinar la envolvente de fases en base a ecuaciones de estado, igualmente se recomienda contar con al menos un dato real de Pb para corroboración. Por supuesto, diferentes simuladores hacen diferentes procesos, simuladores como Hysys y ProII se especializan en Procesos, y son ideales para estos cálculos, pero software como Pipesim, Wellflo y Prosper también tienen la capacidad de hacer tal cálculo

Unusual increase in Gas Oil Ratio of a well may be a good indication that it may have started to flow below its bubble point pressure. This could be verified by carefully reviewing downhole pressure data if such a system has been installed or it could be confirmed by running downhole pressure survey. Wellbore damage is the main reason of FBHP falling below BPP. If wells equipped with downhole ESPs flow below BPP, the pump may cavitate due to presence of excessive free gas. At this stage the well should be evaluated for a stimulation job to restore its FBHP above BPP.

Production data are another source of information for verification or estimation of Pb esp. when no lab measurements are available. For example, on a plot of reservoir pressure against cumulative production (or time), Pb may be estimated as the point where the slope changes. This is due to the fact that below Pb the liberated gas - with its higher compressibility - provides the reservoir with more energy, hence a reduction in pressure decline trend. Another example is a plot of GOR vs. cumulative production (or time): as long as P>Pb, GOR = solution gas oil ratio. It then tends to increase as P falls below Pb. This fact can be used to estimate the time and its corresponding pressure when P=Pb.

Look for the “break” in the material balance Pressure vs. Cum Oil plot. The slope changes as the gas breaks out of solution. Compare that observed break-point with PVT analysis.

When reviewing old field data the bubble point can be determined by observing a flattening in a trend of reservoir pressure versus cumulative production. The pressure drops quickly while the reservoir is above bubble point, then after the reservoir pressure falls below bubble point the pressure will fall more slowly for the same rate of production.