Mole Fraction Of H2S Research Articles

Solubility of H2S-CH4 mixtures in calcium chloride solution: Insight from molecular dynamics simulations

This study uses equilibrium molecular dynamics (EMD) simulations to gain microstructural insight into and predict crucial properties of gas-brine mixtures affecting sour gas reservoir development. The effects of pressure, temperature, gas composition and salinity on the solubility and density of H2S-CH4 mixtures in pure water and CaCl2 brine were investigated at industrially relevant conditions (temperature range of 280 − 340 K, pressures up to 20 MPa, and a salinity range of 4.78 − 17.32 wt%). The force fields used in the MD simulations were validated using experimental data for pure H2S and CH4. The results showed that the solubility of pure H2S and CH4 in pure water increases with pressure, with the latter having a higher solubility. For H2S-CH4 mixtures, the solubility of H2S increased while that of CH4 fell with increasing H2S mole fraction, with the solubilities of the two gases intersecting at an H2S mole fraction of 0.28. Further, the solubility of H2S shows a greater pressure dependence than that of CH4, and H2S gas tends to reach saturation in pure water. In calcium chloride solution, the gas solubility decreases as the ions reduce the interaction between water and gas molecules. The solubility of H2S gas is a stronger function of the ion concentration compared with CH4, and increases 6-fold as the H2S mole fraction increases from 0.5 to 0.8. The overall solubility ranges were 0.45 to 3.48 mol/kg for H2S and 0.15 to 0.25 mol/kg for CH4.

Adsorption behavior of CO2/H2S mixtures in calcite slit nanopores for CO2 storage: An insight from molecular perspective

It is acknowledged that injecting CO2 into oil reservoirs and saline aquifers for storage is a practical and affordable method for CO2 sequestration. Most CO2 produced from industrial exhaust contains impurity gases such as H2S that might impact CO2 sequestration due to competitive adsorption. This study makes a commendable effort to explore the adsorption behavior of CO2/H2S mixtures in calcite slit nanopores. Grand Canonical Monte Carlo (GCMC) simulation is employed to reveal the adsorption of CO2, H2S as well as their binary mixtures in calcite nanopores. Results show that the increase in pressure and temperature can promote and inhibit the adsorption capacity of CO2 and H2S in calcite nanopores, respectively. CO2 exhibits stronger adsorption on calcite surface than H2S. Electrostatic energy plays the dominating role in the adsorption behavior. Electrostatic energy accounts for 97.11% of the CO2-calcite interaction energy and 56.33% of the H2S-calcite interaction energy at 10 MPa and 323.15 K. The presence of H2S inhibits the CO2 adsorption in calcite nanopores due to competitive adsorption, and a higher mole fraction of H2S leads to less CO2 adsorption. The quantity of CO2 adsorbed is lessened by approximately 33% when the mole fraction of H2S reaches 0.25. CO2 molecules preferentially occupy the regions near the pore wall and H2S molecules tend to reside at the center of nanopore even when the molar ratio of CO2 is low, indicating that CO2 has an adsorption priority on the calcite surface over H2S. In addition, moisture can weaken the adsorption of both CO2 and H2S, while CO2 is more affected. More interestingly, we find that pure CO2 is more suitable to be sequestrated in the shallower formations, i.e., 500–1500 m, whereas CO2 with H2S impurity should be settled in the deeper reservoirs.

Adsorption Characteristics of CO2/CH4/H2S Mixtures in Calcite Nanopores with the Implications for CO2 Sequestration

Summary Injecting CO2 into reservoirs for storage and enhanced oil recovery (EOR) is a practical and cost-effective strategy for reducing carbon emissions. Commonly, CO2-rich industrial waste gas is used as the CO2 source, whereas contaminants such as H2S may severely impact carbon storage and EOR via competitive adsorption. Hence, the adsorption behavior of CH4, CO2, and H2S in calcite (CaCO3) micropores and the impact of H2S on CO2 sequestration and methane recovery are specifically investigated. The Grand Canonical Monte Carlo (GCMC) simulations were applied to study the adsorption characteristics of pure CO2, CH4, and H2S, and their multicomponent mixtures were also investigated in CaCO3 nanopores to reveal the impact of H2S on CO2 storage. The effects of pressure (0–20 MPa), temperature (293.15–383.15 K), pore width, buried depth, and gas mole fraction on the adsorption behaviors are simulated. Molecular dynamics (MD) simulations were performed to explore the diffusion characteristics of the three gases and their mixes. The amount of adsorbed CH4, CO2, and H2S enhances with rising pressure and declines with rising temperature. The order of adsorption quantity in CaCO3 nanopores is H2S > CO2 > CH4 based on the adsorption isotherm. At 10 MPa and 323.15 K, the interaction energies of CaCO3 with CO2, H2S, and CH4 are −2166.40 kcal/mol, −2076.93 kcal/mol, and −174.57 kcal/mol, respectively, which implies that the order of adsorption strength between the three gases and CaCO3 is CO2 > H2S > CH4. The CH4-CaCO3 and H2S-CaCO3 interaction energies are determined by van der Waals energy, whereas electrostatic energy predominates in the CO2-CaCO3 system. The adsorption loading of CH4 and CO2 are lowered by approximately 59.47% and 24.82% when the mole fraction of H2S is 20% at 323.15 K, reflecting the weakening of CH4 and CO2 adsorption by H2S due to competitive adsorption. The diffusivities of three pure gases in CaCO3 nanopore are listed in the following order: CH4 > H2S ≈ CO2. The presence of H2S in the ternary mixtures will limit diffusion and outflow of the system and each single gas, with CH4 being the gas most affected by H2S. Concerning carbon storage in CaCO3 nanopores, the CO2/CH4 binary mixture is suitable for burial in shallower formations (around 1000 m) to maximize the storage amount, while the CO2/CH4/H2S ternary mixture should be buried as deep as possible to minimize the adverse effects of H2S. The effects of H2S on CO2 sequestration and CH4 recovery in CaCO3 nanopores are clarified, which provides theoretical assistance for CO2 storage and EOR projects in carbonate formation.

Transport property of hydrogen sulfide in amorphous polyethylene using grand canonical Monte Carlo and molecular dynamics simulations

H2S corrosion poses a significant hurdle to safely transporting sulfur-containing natural gas through metal gathering pipes. Reinforced thermoplastic composite pipes have emerged as a solution, using the polyethylene inner lining layer that resists H2S corrosion. However, the permeation of H2S in the polyethylene may lead to the failure of reinforced thermoplastic composite pipes, resulting in natural gas leakage and environmental pollution. Therefore, it is crucial to investigate the gas transport properties of H2S in polyethylene materials to ensure the reliable functioning of gathering pipes. In this study, the dissolution behavior of H2S for pure H2S and H2S/CH4 mixture in amorphous PE is investigated using the grand canonical Monte Carlo method in conjunction with the NPT, with consideration given to the swelling effect. In addition, the diffusion characteristic is explored through the NVT on the amorphous PE adsorbing H2S. Subsequently, the permeability coefficient is calculated based on the obtained data. The findings reveal that with as the temperature increases, the solubility coefficient decreases, while both the diffusion and permeability coefficients increase. With increasing pressure, both the diffusion and permeability coefficients increase. Additionally, the above three coefficients all increase with increasing H2S mole fraction. The relationships between solubility, diffusion, and permeability coefficients & temperature all conform to the Arrhenius law. Finally, the diffusion mechanism of H2S in amorphous PE is revealed at the microscopic level as the “jumping” mechanism by tracking the diffusion pathway of H2S molecule.

Optimizing Sour Gas Qualification Testing—Modeling the Effects of Temperature and Total Pressure on H2S Fugacity, Activity, and Solubility Coefficients up to 138 MPa and 204°C

Traditionally, the sour severities of high-pressure high-temperature (HPHT) oil and gas production wells were assessed by H2S partial pressure (PH2S): The mole fraction of H2S in the gas (yH2S) multiplied by the total pressure (PT). However, PH2S usually over-predicts the actual sour severity of HPHT systems, leading to suboptimal material selection choices. To reflect recent advances in thermodynamic modeling and to avoid over-conservatism, after careful deliberation, ANSI/NACE MR0175-2021/ISO 15156-2:2022 recently expanded the number of sour severity metrics to four: PH2S, fugacity (fH2S), chemical activity (aH2S), and dissolved concentration (CH2S) of the aqueous phase. The new metrics are often computationally derived and account for thermodynamic nonidealities, which are significant at HPHT conditions. Regardless of the preferred metric, quantifying the sensitivity of each metric to a wide range of temperatures and total pressures is critical when conducting H2S service assessments. In this article, the effect of increasing temperature and total pressure on the thermodynamically derived apparent H2S solubility (KH2S = CH2S/PH2S) was investigated. KH2S is a critical parameter for quantifying changes in H2S phase behavior/sour severity of HPHT systems. Apparent KH2S values were calculated by two different thermodynamic models and benchmarked to two publicly available H2S/H2O datasets up to 120°C and 10.3 MPa equilibrated in a brine containing 165,000 mg/L Cl−. The model that provided the best match to the experimental data was later used in a much broader thermodynamic sensitivity study of the H2S/CH4/H2O/NaCl “oilfield” system. For this sensitivity analysis, changes in fH2S, aH2S, CH2S, and KH2S were individually modeled between 4°C and 204°C, at total pressures up to 138 MPa, and in brines containing up to 25 wt% NaCl (180,000 mg/L Cl−). Lastly, a comparison of the predicted sour severity by pseudo-PH2S, fH2S, and CH2S metrics, over the same temperature and total pressure parameter space, is presented.

Experimental and kinetic study on laminar burning velocities of NH3/CH4/H2S/air flames

Recently, ammonia has been favored by scientists and engineers as a new type of carbon-free fuel for future carbon–neutral society. Before large-scale application, some existing drawbacks including extremely low reactivity need to be overcomed by enhancing combustion technology. Blending ammonia with sour gas, a type of natural gas resource containing amounts of H2S, can be a solution to enhance the combustion of ammonia as well as efficiently utilize natural gas resource. In this study, the laminar burning velocities of NH3/CH4/H2S/air flames were investigated using the Heat Flux method over a wide range of equivalence ratios and and mixing ratios. A kinetic model for NH3/CH4/H2S/air flames simulation was developed by integrating ammonia sub-mechanism with the mechanism of Han et al. and validated based on the experimental data. The experimental results show that the H2S addition has a negative effect on the flame speed, which reaches 13.36 % decrease at ϕ = 1.25 when the H2S mole fraction is 12 %. Kinetic analysis was performed for exploring the effect of H2S addition on the laminar flame propagation of NH3/CH4/H2S mixtures. The results show that the elevated H2S content significantly impacts the radicals pool in flame, where the mole fraction of H, OH radicals decreases while the S-containing species content increases obviously. Sensitivity analysis shows that the reactions involving S-containing species become important for laminar flame speed determination at high H2S content. Besides, the increament of NH3 ratio in the fuel significantly improves the concentration level of NH2 radical in the flame, leading to the increased importance of NH2 chemistry.

Experimental and kinetic modeling study of the CH4+H2S+air laminar burning velocities at atmospheric pressure

With the increasing demand for natural gas and depletion of many sweet gas fields, direct usage of sour gas, usually containing a large percentage of hydrogen sulfide (H2S), becomes a more economical choice in recent years. However, the laminar burning velocity (SL) of CH4+H2S flames have seldom been investigated due to the corrosivity and toxicity of H2S, and no available experimental data can be found for these mixtures burnt in the air. In this work, the laminar burning velocities of CH4+H2S+air flames were measured using the heat flux method at 1 atm and 298 K. The experimental data were obtained at various equivalence ratios and xH2S = 0–0.25, where xH2S refers to the mole fraction of H2S in the fuel. Simulations using a detailed mechanism of Mulvihill et al. (2019) were carried out, showing good agreement with the present experimental results. Kinetic analyses of A-factor SL reaction sensitivities, reaction pathways, and dominant intermediate species pointed out the importance of the C- and S-containing species interactions. To overcome the convergence problem of the Mulvihill mechanism, an examination of the unphysical reactions and species was carried out, which could be alleviated by making several reactions that violate the collision limit irreversible, accompanied by updating the heat capacity data. It's also found that substituting the hydrocarbon subset of the Mulvihill mechanism with mechanisms from FFCM-1, Konnov, San Diego, as well as Aramco noticeably deteriorates the simulation results due to the selection of different reaction rate constants.

Detection of hydrogen sulfide above the clouds in Uranus’s atmosphere

Visible-to-near-infrared observations indicate that the cloud top of the main cloud deck on Uranus lies at a pressure level of between 1.2 bar and 3 bar. However, its composition has never been unambiguously identified, although it is widely assumed to be composed primarily of either ammonia or hydrogen sulfide (H2S) ice. Here, we present evidence of a clear detection of gaseous H2S above this cloud deck in the wavelength region 1.57–1.59 μm with a mole fraction of 0.4–0.8 ppm at the cloud top. Its detection constrains the deep bulk sulfur/nitrogen abundance to exceed unity (>4.4–5.0 times the solar value) in Uranus’s bulk atmosphere, and places a lower limit on the mole fraction of H2S below the observed cloud of $$(1.0-2.5)\times 1{0}^{-5}$$ . The detection of gaseous H2S at these pressure levels adds to the weight of evidence that the principal constituent of 1.2–3-bar cloud is likely to be H2S ice. Ground-based near-infrared spectra of Uranus detected hydrogen sulfide (H2S) above the main cloud deck (at a pressure of 1.2–3 bar), suggesting that the bulk sulfur/nitrogen ratio in Uranus’s atmosphere exceeds unity and that the clouds are dominated by H2S ice.

Numerical study of the burner parameters on the thermal field in a sulfur recovery unit thermal reactor

A sulfur recovery unit (SRU) thermal reactor is the most important equipment in a sulfur plant and is negatively affected by high temperature operations. In this paper, the effect of burner parameters, including the clearance of the acid gas tip and the inlet air swirler angle, on the thermal field in a SRU thermal reactor are investigated numerically, with the aim to reduce the high temperature inside the thermal reactor and to ensure an acceptable sulfur recovery. The simulation results show that the burner with a smaller clearance of the acid gas tip produces a lower temperature, a lower exit SO2 mole fraction and higher exit S2 and H2S mole fractions. Among the clearancs of the acid gas tip investigated, the horizontal clearance of 152.4mm and vertical clearance of 240mm yield the lowest temperature, exit SO2 mole fraction and highest exit S2, H2S mole fractions. The burner with a smaller inlet air swirler angle produces a higher temperature, a higher exit SO2 mole fraction and lower exit S2 and H2S mole fractions. Among the swirler angles investigated, 60° yields the lowest temperature, exit SO2 mole fraction and highest exit S2 , H2S mole fractions.

Developing a K-value equation for predict dew point pressure of gas condensate reservoirs at high pressure

Abstract This paper proposed a new empirical K-value equation is developed to calculate dew pressure for gas condensate reservoirs. This equation is applicable in the wide ranges of composition, temperature, and pressure by considering the effect of composition via two equations for normal boiling point and critical temperature of the mixture. The range of dew pressure, temperature, heptane plus mole fraction, methane mole fraction, N2 mole fraction, CO2 mole fraction, and H2S mole fraction are fallen into 2666.7–9655 Psia, 40–350.87 °F, 0.0021–0.213, 0.3344–0.9668, 0–0.4322, 0–0.0864, and 0–0.942 respectively. As an important point, the proposed equation has any adjustable parameters, in addition, this equation indicates that in order to predict of dew pressure of gas condensate reservoirs, trial and error was not needed and therefore, computational speed increases beyond the accuracy. Moreover, the accuracy is validated by comparing against the experimental data of 81 gas condensate reservoirs samples from published literature and the results of Wilson, Whitson, and Ghafoori equations. Compared to the experimental data, the absolute average deviations of dew pressure calculations for the proposed equation, Wilson, Whitson, and Ghafoori were 7.6%, 97.6%, 99.4%, and 94.9% respectively.

THE EFFECTS OF INLET AIR QUANTITY AND INLET OXYGEN MOLE FRACTION ON THE COMBUSTION AND FLUID FLOW IN A SULFUR RECOVERY UNIT THERMAL REACTOR

Owing to the high temperature inside a sulfur recovery unit (SRU) thermal reactor, detailed experimental measurements are difficult. In the author’s previous studies, several methods have been assessed to resolve the abnormality of the SRU thermal reactor under high temperature operation. This paper presents a new easier and more economical method. The effects of inlet air quantity and inlet O2 mole fraction on the combustion and fluid flow in a SRU thermal reactor are investigated numerically. The flow field temperature, S2 recovery, H2S mole fraction, and SO2 emissions are analyzed. This paper provides a guideline for adjusting the inlet air quantity and the inlet O2 mole fraction to reduce the high temperature inside a thermal reactor and to ensure an acceptable sulfur recovery.

Estimation of natural gases water content using adaptive neuro-fuzzy inference system

ABSTRACTTo appropriate design and satisfactory performance of utilities in the gas processing and transmission plants, a crucial factor that should be taken in consideration is the natural gas water content. The present research aimed to develop a precise strategy for estimating sour gas/sweet gas water content ratio. This developed predictive tool is based on adaptive neuro-fuzzy inference system (ANFIS). In this regard, a comprehensive data bank that contains 1,126 data points was collected. This model predicts ratio of sour gas to sweet gas as function of pressure, temperature, and equilibrium H2S mole fraction. The ranges of pressure and temperature were 200–70000 KPa and 10–150°C, respectively. In addition, the equilibrium H2S mole fraction ranges between 0.076 and 0.492. Results obtained from the ANFIS model confirmed acceptable and reasonable predictive capability of this model. This tool is simple to use and can be help petroleum engineers to predict water content of natural gas at broad ranges of conditions.

Erosion corrosion failure analysis of the elbow in sour water stripper overhead condensing reflux system

The erosion corrosion failure of elbow of one oil refinery was investigated by using Aspen software, CFD technology and experiments. And the gas–liquid equilibrium distribution of H2S and NH3 and multiphase flow simulation in the overhead system of a sour water stripper were obtained. The result shows that the component mole fraction of H2S and NH3 rises markedly with decreasing temperature. At the outlet of air cooler, the temperature drops to 85°C to form high concentration of ammonium bisulfide (NH4HS), which would cause serious erosion corrosion at a certain flow rate and reveals an inhomogeneous thinning. The liquid phase fraction mainly distributes on the outside part of elbow, the more sour water accumulates there resulting in localized corrosion thinning. Meanwhile, the experiments show that when the concentration of NH4HS reaches 10wt.%, the corrosion rates increase rapidly with increased velocity. Thus controlling the concentration of NH4HS below 10wt.% in reflux drum would reduce the risk of erosion corrosion failure.

Monte Carlo simulation study of the halogenated MIL-47(V) frameworks: influence of functionalization on H2S adsorption and separation properties

Monte Carlo simulation calculations were performed to explore the H2S adsorption and separation in the initial MIL-47(V) and the monohalogenated MIL-47(V)-X (X = F, Cl, Br). Both initial and halogenated MIL-47(V) metal–organic framework materials (MOFs) exhibit an ultra-high H2S adsorption ability, which is much higher than that of CH4 and N2. Halogen functionalization could enhance the H2S uptake in unit volume of MOFs especially in low-pressure range, with the sequence: MIL-47(V) MIL-47(V)-F > MIL-47(V)-Cl > MIL-47(V)-Br, because of the increasing mass density of MOFs after halogenation. The adsorption behavior of four MOFs for the H2S/CH4 and H2S/N2 mixtures are explored as a function of both pressure and H2S mole fraction, and all of four MOFs show the ultraselectivity toward H2S molecule. Compared to the initial MIL-47(V), the halogenated MOFs exhibit the preferable H2S/CH4 and H2S/N2 selectivity under the conditions of low temperature, high pressure, and high H2S mole fraction.

Xylene addition effects to H2S combustion under Claus condition

Experimental results are presented on the combustion of H2S and mixtures of H2S and xylene at an equivalence ratio of three (Claus condition). The H2S mole fraction decreased along longitudinal central axis of the reactor to a minimum value. The SO2 mole fraction increased to a maximum value, which subsequently decomposed due to the formation of elemental sulfur, which is favorable under Claus condition. In contrast, mixtures of H2S and trace amounts of xylene (0.5%, 1% and 2%) favored the formation of H2 and increased the amounts of H2S at reactor exit. Xylene addition reduced the maximum mole fraction of SO2, and resulted to the formation of CH4 and CO. The formed SO2 decomposed faster to yield COS and CS2 from its reaction with CH4 and CO. The formation of CH4, CO, COS and CS2 poses severe impact on sulfur capture efficiency from acid gases. These results reveal a direct impact on the Claus reactor performance with trace amount of xylene present in H2S thermal processing.

Removal of hydrogen sulfide from natural gas by the graphene-nanotube hybrid structure: A molecular simulation

The molecular simulations are adopted to investigate the separation of H2S/CH4 mixture by the graphene-nanotube hybrid structure (GNHS). The effects of pressure, temperature and H2S mole fraction on the adsorption and separation behaviors are examined. The results show that the separation performance of the GNHS can be enhanced by reducing the adjacent carbon nanotubes (CNTs) distance. The self-diffusivity of H2S molecules in the GNHS is 1.83×10−8m2s−1 which is less than that of CH4. Therefore, enlarging the diffusivity discrepancy of the two components can improve the separation performance of the GNHS.

Reliable estimation of optimal sulfinol concentration in gas treatment unit via novel stabilized MLP and regularization network

Proper technology or configuration for sulfur recovery units (SRUs) strongly depends on H2S concentration of inlet acid gas stream. Various acid gas enrichment (AGE) schemes with different solvents can be used to reduce the concentration of carbon dioxide and heavy aromatic hydrocarbons while enriching the H2S content of SRU feed stream. The present article uses combinations of Aspen-HYSYS software and two in-house artificial neural networks (namely, Regularization and stabilized multilayer perceptron networks) to compare the AGE capability of sulfinol-M (sulfolane + MDEA) solvent at optimal concentration with traditional MDEA solution when both of them are used in a conventional gas treating unit (GTU). The simulation results indicate that the optimal concentration of Sulfinol-M aqueous solution (containing 37 wt% Sulfolane and 45 wt% MDEA) will completely eliminate toluene and ethylbenzene from the SRU feed stream while removing 80% of benzene entering the GTU process. Furthermore, mole fraction of H2S in the SRU feed stream increases from the conventional 33.48 mol % to over 57 mol %. Increased H2S selectivity of optimal sulfinol-M aqueous solution will elevate the CO2 slippage through sweet gas stream at around 4.5 mol % which is still below the permissible threshold. To the best of our knowledge, the stabilized MLP network has not been addressed previously.

Simulation of Liquid and Supercritical Hydrogen Sulfide and of Alkali Ions in the Pure and Aqueous Liquid

A polarizable model for hydrogen sulfide (H2S) is optimized based on the experimental properties of the monomer and of the bulk liquid. The model is characterized by rigid SH bonds but flexible HSH angle and the polarizability is based on the Drude oscillator model. Bonded parameters and atomic charges are based on the experimental properties of the gaseous monomer. Atomic Lennard-Jones (LJ) parameters are adjusted based on the density of H2S around the critical point (in the temperature range 363-393 K and pressure range 8.023-10.013 MPa). The model gives binding energies for H2S dimers, trimers, and tetramers in good agreement with ab initio MP2(full)/6-311++G(d,p) results. It shows a liquid structure in very good agreement with neutron diffraction data. The model also gives density, self-diffusion coefficient, heat of vaporization, and dielectric constant of liquid hydrogen sulfide at the normal boiling point in good agreement with experimental data. In addition, the model is transferable to high temperature and pressure conditions, as evidenced from simulations up to 542.2 K and 40 MPa. The model is used in combination with the SWM4-NDP water model, with LJ parameters between the S and O atoms adjusted to reproduce the experimental hydration free energy of H2S. Simulations suggest that, in its first solvation shell, a single H2O molecule is solvated by 10 H2S molecules while a single H2S molecule is solvated by 20.5 H2O molecules. Pair-specific LJ parameters between alkali ions (Li(+), Na(+), K(+), Rb(+), Cs(+)) and the S atom are adjusted to reproduce ab initio binding energies of the ion-H2S pairs at the CCSD(T) level. Simulations based on these parameters show that alkali ions have higher coordination numbers and lower solvation free energies in liquid H2S than in liquid water or liquid ammonia. The model is also used to investigate the preferential solvation of the ions in aqueous solutions with a 10% H2S mole fraction. Results show that the ions are preferentially solvated by water in their first solvation shell but have no significant selectivity to either ligands in their second shells.

The genetic algorithm based back propagation neural network for MMP prediction in CO2-EOR process

In this study, a genetic algorithm based back propagation artificial neural network model was developed and used to predict the minimum miscibility pressure, i.e. MMP, for both pure and impure CO2 injection cases. Ten parameters that affecting the MMP were chosen as input variables, while the MMP was selected as output parameter. These parameters were reservoir temperature-TR, mole fraction of volatile oil components-xvol, mole fraction of intermediate oil components-xint, mole fraction of C5–C6 oil components-xC5-C6, molecular weight of C7+ components-MWC7+, mole fraction of CO2 in solvent-xCO2, mole fraction of C1 in solvent-xC1, mole fraction of N2 in solvent-xN2, mole fraction of H2S in solvent-xH2S, and mole fraction of C2–C4 in solvent-xC2–C4. The performance of the newly developed model was evaluated by calculating the deviations between the predicted and the target values, and was compared with four well known correlations in published literature. Through the comparison, it can be found that our new model outperformed those four correlations with the lowest average absolute relative error of 5.51% and mean square error of 7.01%. The influence degrees of each factor on MMP were also analyzed qualitatively and quantitatively by sensitivity analysis. It was found that xint, xC5–C6, and xH2S have positive effects on MMP, while TR, xvol, MWC7+, xCO2, xC1, and xN2 have negative effects on MMP. In addition, the effect of xC2–C4 on MMP can be neglected. Furthermore, the variations of MMP with the increase of each factor were also considered, and it can be found that the slopes of these curves are not constant all the time and change with the variations of the influence factors.

A Neural Network Based Model for Prediction of Saturation Pressure from Molecular Components of Crude Oil

Saturation pressure is a crucial property of reservoir fluid, which is widely used in petroleum engineering calculations. In this study, a neural network model was developed for prediction of saturation pressure based on molecular components of 100 crude oils samples. Inputs of a neural network model include mole fractions of hydrocarbon and non-hydrocarbon components (C1–C6, C7+, H2S, CO2, and N2), specific gravity of C7+, molecular weight of C7+, and reservoir temperature. Molecular components of 30 crude oil samples were employed to judge the efficiency of the proposed neural network model against the Elsharkawy model and Soave–Redlich-Kwong and Peng-Robinson equations of state. Results showed that the neural network model achieved the lowest average absolute relative error and the highest correlation coefficient. Furthermore, relative contribution of network inputs on saturation pressure was obtained by sensitivity analysis, which indicated high influence of C1 and H2S mole fractions on saturation pressure.