Browsing by Subject "Critical point"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Closed-form van der waals critical point for petroleum reservoir fluids(2005-05) Hassoun, Talal H.; Lawal, Akanni S. L.; Henize, Lloyd R.; Lea, James F.The prediction of critical points is of great practical importance because the classification of petroleum reservoir fluids as a dry gas, gas condensate, volatile oil, and crude oil depends largely on the knowledge of the critical properties of the reservoir fluid. Also, the critical pressure and critical temperature of reservoir fluids are important properties for describing the reservoir fluid phase behavior, predicting volumetric properties of reservoir fluids and designing supercritical fluid processes. Previous work for determining critical pressure, and critical temperature for reservoir fluids include, empirical correlations, corresponding states method, and pseudo-critical property methods. The generality of these previous correlations is limited to the range of conditions and parameters used in the establishment of the correlations. Methods based on the Gibbs criteria have also been used with Redlich-Kwong and Peng-Robinson equations for prediction of critical properties. However, the Gibbs criteria have not been applied to predicting critical properties of reservoir fluids. A closed-form equation is developed for predicting the critical properties (Tc, Pc) of complex reservoir fluids by using the Lawal-Lake-Silberberg (LLS) equation of state with the criticality criteria established by Nobel Laureates van der Waals (VDW) in 1873. By inverting the parameters of the LLS EOS in terms of the mixing parameters that are based on the constituent substances and composition of the reservoir fluids, experimental critical pressures and temperatures are predicted with interaction parameters expressed in terms of molecular weight ratios of the binary constituent of reservoir fluids. The prediction results of critical pressures and temperatures based on the VDW criticality criteria show that experimental data consisting of 85 reservoir fluid mixtures are within average absolute percent deviation of 3% to 5% of the measured critical pressures and temperatures. In contrast to the previous work, this research project provides an accurate method for computing the critical properties of reservoir fluids and it is easy to use because the parameters of the criticality equation are readily available. This project is useful for unifying near-critical flash routine with phase equilibria of the compositional reservoir models. The project is also very attractive for establishing reservoir models that are based on the critical composition convergence pressure concept.Item Closed-form van der waals critical point for petroleum reservoir fluids(Texas Tech University, 2005-05) Hassoun, Talal H.The prediction of critical points is of great practical importance because the classification of petroleum reservoir fluids as a dry gas, gas condensate, volatile oil, and crude oil depends largely on the knowledge of the critical properties of the reservoir fluid. Also, the critical pressure and critical temperature of reservoir fluids are important properties for describing the reservoir fluid phase behavior, predicting volumetric properties of reservoir fluids and designing supercritical fluid processes. Previous work for determining critical pressure, and critical temperature for reservoir fluids include, empirical correlations, corresponding states method, and pseudo-critical property methods. The generality of these previous correlations is limited to the range of conditions and parameters used in the establishment of the correlations. Methods based on the Gibbs criteria have also been used with Redlich-Kwong and Peng-Robinson equations for prediction of critical properties. However, the Gibbs criteria have not been applied to predicting critical properties of reservoir fluids. A closed-form equation is developed for predicting the critical properties (Tc, Pc) of complex reservoir fluids by using the Lawal-Lake-Silberberg (LLS) equation of state with the criticality criteria established by Nobel Laureates van der Waals (VDW) in 1873. By inverting the parameters of the LLS EOS in terms of the mixing parameters that are based on the constituent substances and composition of the reservoir fluids, experimental critical pressures and temperatures are predicted with interaction parameters expressed in terms of molecular weight ratios of the binary constituent of reservoir fluids. The prediction results of critical pressures and temperatures based on the VDW criticality criteria show that experimental data consisting of 85 reservoir fluid mixtures are within average absolute percent deviation of 3% to 5% of the measured critical pressures and temperatures. In contrast to the previous work, this research project provides an accurate method for computing the critical properties of reservoir fluids and it is easy to use because the parameters of the criticality equation are readily available. This project is useful for unifying near-critical flash routine with phase equilibria of the compositional reservoir models. The project is also very attractive for establishing reservoir models that are based on the critical composition convergence pressure concept.Item A new relative permeability model for compositional simulation of two and three phase flow(2010-12) Yuan, Chengwu; Sharma, Mukul M.; Pope, Gary A.; Sepehrnoori, Kamy; Mohanty, Kishore K.; Edgar, Thomas F.Chemical treatments using solvents and surfactants can be used to increase the productivity of gas-condensate wells with condensate banks. CMG’s compositional simulator GEM was used to simulate such treatments to gain a better understanding of design questions such as how much treatment solution to inject and to predict the benefits of such treatments. GEM was used to simulate treatments in vertical wells with and without hydraulic fractures and also horizontal wells. However, like other commercial compositional simulators, the flash calculations used to predict the phase behavior is limited to two phases whereas a three-phase flash is needed to accurately model the complex phase behavior that occurs during and after the injection of treatment solutions. UTCOMP is a compositional simulator with three-phase flash routine and attempts were made to use it to simulate such well treatments. However, this is a very difficult problem to simulate and all previous attempts failed because of numerical problems caused by inconsistent phase labeling (so called phase flipping) and the discontinuities this causes in the relative permeability values. In this research, a new relative permeability model based on molar Gibbs free energy was developed, implemented in a compositional simulator and applied to several difficult three-phase flash problems. A new way of modeling the residual saturations was needed to ensure a continuous variation of the residual saturations from the three-phase region to the two-phase region or back and was included in the new model. The new relative permeability model was implemented in the compositional reservoir simulator UTCOMP. This new relative permeability model makes it is unnecessary to identify and track the phases. This method automatically avoids the previous phase flipping problems and thus is physically accurate as well as computationally faster due to the improved numerical performance. The new code was tested by running several difficult simulation problems including a CO2 flood with three-hydrocarbon phases and a water phase. A new framework for doing flash calculations was also developed and implemented in UTCOMP to account for the multiple roots of the cubic equation-of-state to ensure a global minimum in the Gibbs free energy by doing an exhaustive search for the minimum value for one, two and three phases. The purpose was to determine if the standard method using a Gibbs stability test followed by a flash calculation was in fact resulting in the true minimum in the Gibbs free energy. Test problems were run and the results of the standard algorithm and the exhaustive search algorithm compared. The updated UTCOMP simulator was used to understand the flow back of solvents injected in gas condensate wells as part of chemical treatments. The flow back of the solvents, a short-term process, affects how well the treatment works and has been an important design and performance question for years that could not be simulated correctly until now due to the limitations of both commercial simulators and UTCOMP. Different solvents and chase gases were simulated to gain insight into how to improve the design of the chemical treatments under different conditions.