Fathollah Gozalpour

Viscosity and Density of Methane+cis-Decalin from 323 to 423 K at Pressures to 140 MPa

Dynamic viscosity (η) and density (ρ) data are reported for methane+cis-decahydronaphthaline (decalin) binary mixtures of 25, 50, and 75 mass% (74, 90, and 96 mol%) methane at three temperatures (323, 373, and 423 K) from saturation pressure to 140 MPa. A capillary tube viscometer was used for measuring the dynamic viscosity, with the density being calculated from measurements of sample mass and volume. The overall uncertainties in the reported data are 1.0 and 0.5% for the viscosity and density measurements, respectively.

RAPID AND ROBUST PHASE EQUILIBRIUM CALCULATION TO MODEL FLUIDS IN RESERVOIR AND SURFACE PROCESSING

Compositional simulation is widely used in the petroleum industry to predict the phase behaviour of reservoir fluids within the reservoir, flow lines and process facilities. Computational time is an important factor in compositional simulation where CPU time exponentially increases with the number of components. It has been shown that by omitting binary interaction parameters (BIPs) from the mixing rules of the equation of state (EOS), phase split calculations can be carried out much faster than when using conventional methods, when a large number of components is used to describe the reservoir fluid. However, using the rapid flash calculation method, the phase behaviour calculation may fail to converge, particularly for gas condensate systems. Omitting BIPs may also deteriorate the predictive capability of the EOS for some fluids. In this paper, the original rapid flash calculation method is modified to improve its convergence for gas condensate systems. To compensate for the omitted binary interaction parameters, the temperature dependency of the attractive term (α) in EOS has been modified to improve its phase behaviour prediction over a wide range of temperatures. A number of binary systems were used to determine the α function for supercritical compounds. This improved the EOS predictions for systems with high concentrations of supercritical compounds. The objective is to perform the phase equilibrium calculation as rapidly as possible with a large number of components in the reservoir without compromising on accuracy of predictions. Then, using the same number of components, detailed compositional analysis can be used to design efficient process facilities.

Predicting Reservoir Fluid Phase and Volumetric Behaviour from Samples Contaminated with Oil-Based Mud

Oil based muds are widely used in offshore drilling applications. Of concern however is the resulting contamination associated with obtaining high quality samples of formation hydrocarbons. The filtrate of oil based muds is highly soluble in formation hydrocarbon fluids, therefore, any contamination of the sample with oil based mud filtrate can significantly affect the composition and phase behaviour of the formation fluids. In this study the impact of contamination on the phase behaviour and properties of different types of reservoir fluids, including gas condensate and volatile oil samples, is investigated. Various types of oil based muds, synthetic (with limited number of hydrocarbons) and natural oil (wide range of petroleum fractions), are used to contaminate reservoir fluids and their composition and phase behaviour are measured at surface and reservoir conditions in this laboratory. Two simple methods have been developed to determine the uncontaminated fluid composition from contaminated samples. Highly contaminated field samples have been used to demonstrate the capability of the developed methods. The phase behaviour and volumetric properties of the original reservoir fluid predicted by phase behaviour models developed for contaminated samples can highly be erroneous. A method has also been developed in this study which can determine the required equation of state (EOS) parameters of the uncontaminated fluid, using the developed phase behaviour models from data of contaminated samples. The capability of the method has been examined against experimental data of different types of reservoir fluids. The proposed method in all cases provided accurate predictions of PVT data. The developed method is general and it can be applied to any cubic EOS.