Novel empirical correlations for estimation of bubble point pressure,saturated viscosity and gas solubility of crude oils

Knowledge of petroleum fluid properties is crucial for the study of reservoirs and their development. Estimation of reserves in an oil reservoir or determination of its performance and economics requires a good knowledge of the fluid physical properties. Bubble point pressure, gas solubility and viscosity of oils are the most important parameters in use for petroleum and chemical engineers. In this study a simple-to-use, straight-forward mathematical model was correlated on a set of 94 crude oil data. Three correlations were achieved based on an exponential regression, which were different from conventional empirical correlations, and were evaluated against 12 laboratory data other than those used for the regression. It is concluded that the new exponential equation is of higher precision and accuracy than the conventional correlations and is a more convenient mathematical formulation.

Thermodynamic modeling of gas solubility in aqueous sodium chloride solution

An electrolyte Equation of State is presented by combining the Cubic Plus Association Equation of State,Mean Spherical Approximation and the Born equation.This new model uses experimental relative static permittivity,intend to predict well the activity coefficients of individual ions(ACI)and liquid densities of aqueous solutions.This new model is applied to model water+Na Cl binary system and water+gas+Na Cl ternary systems.The cation/anion-water interaction parameters of are obtained by fitting the experimental data of ACI,mean ionic activity coefficients(MIAC)and liquid densities of water+Na Cl binary system.The cation/anion-gas interaction parameters are obtained by fitting the experimental data of gas solubilities in aqueous Na Cl solutions.The modeling results show that this new model can correlate well with the phase equilibrium and volumetric properties.Without gas,predictions for ACI,MIAC,and liquid densities present relative average deviations of 1.3%,3.6%and 1.4%compared to experimental reference values.For most gas-containing systems,predictions for gas solubilities present relative average deviations lower than 7.0%.Further,the contributions of ACI,and salting effects of Na Cl on gases are analyzed and discussed.

COSMO-based models for predicting the gas solubility in polymers

We like to highlight the extension of COSMO-based models(COSMO RS-FV and COSMO SAC-FV)to the prediction of gas solubility in polymers,including polymerized ionic liquids(PILs)for the first time.To verify the applicability of COSMO-based models,the predicted values for gas solubility in both common polymers(CH_(4)/N_(2)+PEG)and PELs(CO_(2)+P[MATMA][BF_(4)]/P[VATMA][BF_(4)])were evaluated based on previous experimental data.It was confirmed that the COSMO-RS(Klamt)model performs better than the COSMO-SAC model for common polymers,whereas the COSMO-RS(ADF-Lei 2018)exhibits the best predictions for PILs.The moderately accurate predictions of COSMObased models demonstrate the high potential for predicting gas solubility in polymers.

Machine learning prediction of methane,ethane,and propane solubility in pure water and electrolyte solutions:Implications for stray gas migration modeling

Hydraulic fracturing is an effective technology for hydrocarbon extraction from unconventional shale and tight gas reservoirs.A potential risk of hydraulic fracturing is the upward migration of stray gas from the deep subsurface to shallow aquifers.The stray gas can dissolve in groundwater leading to chemical and biological reactions,which could negatively affect groundwater quality and contribute to atmospheric emissions.The knowledge oflight hydrocarbon solubility in the aqueous environment is essential for the numerical modelling offlow and transport in the subsurface.Herein,we compiled a database containing 2129experimental data of methane,ethane,and propane solubility in pure water and various electrolyte solutions over wide ranges of operating temperature and pressure.Two machine learning algorithms,namely regression tree(RT)and boosted regression tree(BRT)tuned with a Bayesian optimization algorithm(BO)were employed to determine the solubility of gases.The predictions were compared with the experimental data as well as four well-established thermodynamic models.Our analysis shows that the BRT-BO is sufficiently accurate,and the predicted values agree well with those obtained from the thermodynamic models.The coefficient of determination(R2)between experimental and predicted values is 0.99 and the mean squared error(MSE)is 9.97×10^(-8).The leverage statistical approach further confirmed the validity of the model developed.

Solubility of Ammonia in Ethylene Glycol Between 303K and 323K under Low Pressure from 0.030 to 0.101 MPa

The solubility of ammonia in ethylene glycol is measured by an isothermal solubility equilibrium method at temperatures of （303.2, 308.2, 313.2, 318.2 and 323.2） K and total pressures of （0.030, 0.040, 0.050, 0.060, 0.070, 0.080, 9.090 and 0.101） MPa. The molality of ammonia in ethylene glycol ranges from 1.925 mol·kg-1 to 8.265 mol·kg-1. The experimental results are used to determine Henry＇s law constant of ammonia in ethylene glycol Furthermore, experimental data are correlated by applying the thermodynamic model on the basis of extended Raoult＇s law, extended Henry＇s law, corresponding-states correlations and Pitzer＇s molality scale based equation. The overall average relative deviation between the calculated data and the experimental data of Henry＇s law constant and ammonia solubility are 2.029% and 2.164% respectively.

The behaviors of gas-liquid two-phase flow under gas kick during horizontal drilling with oil-based muds

Natural gas is easily soluble in oil-based muds(OBM),leading to complex flow behavior in wellbores,especially in horizontal wells.In this study,a new transient flow model considering wellbore-formation coupling and gas solubility on flow behavior is developed to simulate gas kicks during horizontal drilling with OBM.Furthermore,the effect of gas solubility on parameters such as bottom-hole pressure(BHP),gas void fraction and mixture velocity in the flow behavior is analyzed.Finally,several critical factors affecting flow behavior are investigated and compared to gas kicks in water-based muds(WBM)where the effect of solubility is neglected.The results show that the invading gas exists as dissolved gas in the OBM and as free gas in the WBM.Before the gas escapes from the OBM,the pit gain is zero and there is barely any change in the BHP,annulus return flow rate and mixture velocity,which means that detecting gas kicks through these warning signs can be challenging until they get very close to the surface and develop rapidly.However,in WBM drilling,these parameters change quickly with the increasing gas kick time.Additionally,for both cases,the longer the horizontal length and the greater reservoir permeability,the greater the decrease in BHP,and the shorter the time for gas to migrate from the bottom-hole to the wellhead.A larger flow rate contributes to a greater initial BHP and a lesser BHP reduction.This research is of value in characterizing gas kick behavior and identifying novel ways for early gas kick detection during horizontal drilling with OBM.

Solubilities of CO_2, CH_4,H_2,CO and N_2 in choline chloride/urea

Solubilities of CO_2, CH_4, H_2, CO and N_2 in choline chloride/urea(ChCl/Urea) were investigated at temperatures ranging from 308.2 to328.2 K and pressures ranging from 0.6 to 4.6 MPa. The results show that the solubilities of gases increase with increasing pressure and decreasing temperature. The solubility of CO_2 is higher than that of CH_4, H_2, CO and N_2, which indicates that ChCl/Urea may be used as a potential solvent for CO_2 capture from the gas mixture. Solubility of CO_2 in ChCl/Urea was fitted by Non-Random Two-Liquid and Redlich-Kwong(NRTL-RK) model, and solubility of CH_4, H_2, CO or N_2 in ChCl/Urea was fitted by Henry's Law. The standard enthalpy, standard Gibbs energy and standard entropy of gases were calculated. Additionally, the CO_2/CH_4 selectivities in water, dry ChCl/Urea and aqueous ChCl/Urea were further discussed.

Prediction of Absorption Enthalpy from Solubility Data for the MDEA-H_2O-CO_2 System

A thermodynamic model about the absorption of CO 2 by a solution of methyl diethanol amine (MDEA) and water was established with the electrolytic NRTL (non random two liquid) equation for the calculation of activity coefficients of components in the solution. The gas absorption solubility data was used to obtain the parameters in the electrolytic NRTL equation by regression and to directly predict the absorption enthalpy.

Water Soluble Gas in Deep Carbonate Reservoir, Sichuan Basin, Southwest China

Based on temperature and pressure of fluid inclusion, phase of organic inclusion in calcite and quartz filled in vug in the deep carbonate reservoir and the natural gas composition in Weiyuan （威远） gas field in Sichuan （四川） basin, research indicates that water soluble gas exists in deep carbonate reservoir, which reconstructs development and effusion process of water soluble gas. The overpressure formed during oil thermal cracking can reach 105-170 MPa in Sinian and Cambrian reservoir in Central Sichuan and 78-86 MPa in Cambrian reservoir in Southeast Sichuan. The high temperature caused by deep burial and overpressure caused by thermal cracking make thermal cracking gas dissolve in water so that it becomes water soluble gas. The ratios of gas to water can reach 50-90 m^3/m^3 and 10-30 m^3/m^3, respectively, in deep carbonate reservoir in Central and Southeast Sichuan. Methane dissolving in water exists in form of liquid phase. Until now, the decreases in temperature and pressure due to the uplift during 74 Ma make water soluble gas separate from water, water soluble gas pool or mixed gas pool of thermal-cracking gas and water soluble gas are modified or even destroyed in varying degrees.This may be the case of Weiyuan gas field.

Paleo-temperature Evolution and Water Soluble Gas in Sinian Reservoir, Anpingdian-Gaoshiti Structural Zone, Central Sichuan Basin

The paleo-temperature evolution of Sinian reservoir of Anping （安平） 1 well was rebuilt by taking the method of apatite fission track and Easy%Ro model. The result of apatite fission track determines the accurate burial history and overcomes the flaw that the vitrinite reflectance is taken as paleo-temperature indicator simply. The authors used the laser Raman technique to analyze the methane present in the calcite and quartz fluid inclusions of Sinian reservoir, finding that the methane is water soluble gas. The authors also simulated the paleo-pressure of fluid inclusion by using PVTsim software and finally worked out the methane solubility in water.