Hydrate Formation Temperature Research Articles

Comparison of several methods for obtaining hydrate formation pressure

ABSTRACTIn petroleum engineering hydrate is referred to as crystalline and snow like compounds Which consists of the capture of gaseous molecules among water molecules. The primary requirement for the prevention of hydrate is to recognize the conditions for its formation. Hydrate formation conditions include the presence of water, small gas molecules and the appropriate conditions of temperature and pressure. Several models have been proposed to determine the hydration pressure and temperature. Van der waals-platteeuw is a model base on statistical thermodynamics. In this model, the determinant is the fugacity of the gas phase. In this paper, the fugacity is obtained with different equations of state and replaced by the pattern provided by Parish and Prasnitz, to obtain the pressure and temperature of hydrate formation. In the end, results are compared with laboratory data and results from the CSMHyd Software and the experimental data to Check the accuracy of the model.

Effectiveness of Hydrate-Formation Inhibitors Evaluated by a Polythermal Method

The effectiveness of hydrate-formation inhibitors is evaluated to select the best reagents for preventing hydrate formation in gas wells that are active-gas donors for conditions in the eastern part of Orenburg oil and gas condensate fields. A polythermal method that involves cooling at a constant rate of 1°C/h a system consisting of an inhibitor dissolved in simulated strata water and a gas mixture was used for the study. The inhibiting properties of the samples were characterized from the initial hydrate-formation temperature and the amount of gas turned into hydrate at the end of the test.

Assessing thermodynamic models and introducing novel method for prediction of methane hydrate formation

Transmission of natural gas with methane as the main constituent has been a subject of interest to industrial companies. Predicting hydrate formation conditions is important to prevent formation of methane hydrate in gas pipeline. Also, attention has been taken to account for capture and storage of pure methane. In this paper, a comprehensive comparison is performed between empirical correlations and different equation of state in van der Waals Platteeuw (VdW-P) thermodynamic model to determine the most accurate method of hydrate formation condition of methane. In addition, a novel, simple and accurate correlation is developed to predict methane hydrate formation temperature using genetic programming. Error analysis on a wide range of experimental data indicates that the new proposed correlation is superior over existing correlations and all VdW-P models with R2 = 0.999.

Formation Behaviors of CO2 Hydrate in Kaoline and Bentonite Clays with Partially Water Saturated

CO2 hydrates can be used for long term storage of CO2 in the deep ocean. Clay minerals are the most important components of the marine sediments. In this study, the formation behaviors of carbon dioxide hydrate in kaoline clay and bentonite clay with partially water saturated were studied in a closed system. The mass ratio of water to Kaoline and Bentonite clays is 20%. The experiments were carried out at the temperature of 279.15 K and the initial formation pressure range of 4.8-3.4 MPa. The liquefaction of the carbon dioxide was observed in the cooling process by setting the temperature of the water bath to the valued experimental temperature. The temperature in the crystallizer begins to rise quickly when the hydrate starts to form and then decreases gradually after reaching the highest value. For the experiments in kaoline clay, the temperature decreases gradually along with the equilibrium hydrate formation temperature, and the hydrate formation rate is controlled by the heat transfer process. The final conversion of the water to hydrate increases with the increase of the initial formation pressure and restrained by the equilibrium hydrate formation pressure. For the experiments in bentonite clay, the temperature during the hydrate formation is much higher than the equilibrium temperature for CO2 hydrate formation. The final pressure is much higher than the equilibrium pressure of CO2 hydrate, and increases with the increase of the initial formation pressure, indicating that the equilibrium pressure CO2 hydrate in bentonite clay is higher than the bulk CO2 hydrate.

Modeling of hydrate formation condition for binary gases containing methane and ethane

ABSTRACTThe present study was purposed to model the hydrate formation temperature of the pure gas containing CH4 and C2H6 in a certain pressure range from 1 to 50 MPa by Peng–Robinson (PR). Hydrate forming temperature depends on pressure and composition of gases. Accuracy of this model was evaluated by data collected from other previously published research. Results from the model showed the hydrate formation temperatures have great agreement with reported values. High value of R2 (0.99) confirms its satisfactory performance.

Transient Simulation for Hydrate Mitigation Aims for Optimal Production in Kuwait Fields

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 182237, “Assuring Optimal Production and Enhanced Operational Efficiency Through Transient Simulation—A Case Study in North Kuwait Jurassic Fields,” by Mohammad Al-Sharrad, Kuwait Oil Company; Roshan Prakash, SPE, and Christian F. Trudvang, SPE, Schlumberger; and Noura Al-Mai, Abrar A. Hajjeyah, SPE, and Abdulaziz H. Al-Failakawi, SPE, Kuwait Oil Company, prepared for the 2016 SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 25–27 October. The paper has not been peer reviewed. In the deep high-pressure/high-temperature North Kuwait Jurassic (NKJ) fields, the pipelines connecting the wells to the processing facility are neither buried nor insulated. During the winter, the well fluid cools to below hydrate-formation temperature in the flowline, causing hydrate crystallization and even plugging. This paper presents the traditional methods of hydrate mitigation used in the NKJ fields and the way in which a transient model was initially built and continuously improved. Challenges Hydrate Formation. When the well forms hydrates, usually at night and early morning in winter, the field operators must wait for the ambient temperature to rise in order to melt the hydrate plugs. In general, well production declines for 6–8 hours because of hydrates. Because hydrate formation is the main cause of concern, a robust solution is needed to minimize production downtime. No proper flow-assurance study or modeling was conducted to understand the effect of water and inhibition details on the hydrate curve. To address this challenge, a predictive transient tool is needed to know in advance when hydrate will start to form, the location of hydrate formation, and the required methanol (MeOH) dosage rate to avoid hydrate formation. The current practice of hydrate inhibition is mainly based on past experience. Injecting MeOH on the basis of past experience, without knowing the optimal MeOH-injection rate, could lead to other flow-assurance challenges. Slug Flow. Low-condensate/gas-ratio and high-water/gas-ratio wells have a tendency to create slug flow in the pipeline because of continuous changes in the phase holdups. Because of wide temperature fluctuations between night and day, the fluid in the pipeline is always in a transient state. The pipeline acts as storage because of its large volume (1,000–3,000 bbl). In the morning, when the pipeline is heated, the fluids expand and gas holdup increases in the line, which pushes the liquid to the facility and causes a surge at the facility inlet. At night, when the pipeline cools, liquid hydrocarbon accumulates in the line, increasing the liquid holdup. High-water wells always will have a tendency to accumulate water in the low-lying zones. This water generally moves as a slug. Modeling of the multiphase fluids to understand the slug behavior is required for balancing the fluid in and fluid out of the facility. Long and complicated flowline geometry further complicates the system dynamics and will affect the flow behavior.

New predictive method for estimation of natural gas hydrate formation temperature using genetic programming

Diagnosis of detailed conditions of hydrate formation, as an important issue of gas fuels, can help related industries a lot, particularly in storing, transportation and processing equipment. Hydrate formation temperature or pressure can be predicted by application of mathematical models, due to thermodynamic behavior of hydrate phenomenon. A number of thermodynamical approaches along with some mathematical techniques (analytical and numerical methods) have been used to estimate hydrate formation temperature. However, there are also a variety of other techniques which have not been investigated. Application of genetic programming in developing predictive models seems novel. In the present study, three new data-based models were produced for estimation of hydrate formation temperature of natural gas, as functions of equilibrium pressure and gas molecular weight by implementation of genetic programming methodology. A total of 891 experimental data covering large range of temperatures (10.31–89.33 °F), pressures (8.1511–10,004.7 psi) and molecular weights (16.04–58.12 g/mol) were collected from the literature and used in correlation developing. The correlation coefficient (R2 = 0.9673), root-mean-square deviation (RMSD = 2.2083 °F) and average absolute relative deviation percent (AARD = 3.0830%) show that the genetic-based new models have acceptable accuracy and efficiency.

Influence of gas hydrate formation on methane seeps at the bottom of water reservoirs

It is shown by numerical modeling that the height of gas flares above underwater methane seeps depends strongly on water parameters. A simulation model of the dynamics of a rising bubble was used. Along with gas exchange through the bubble wall, the model takes into account gas hydrate formation, whose rate is determined by turbulent heat exchange with water. Calculations were performed for depths of 250 to 1500 m with an initial bubble diameter of 0.2 to 1.5 cm. It is shown that at the water temperature of the Arctic seas, rising methane bubbles transform into gas hydrate ice within the first 1-2 m of their path. At the same time, when the water temperature is higher than the hydrate formation temperature near the sea bottom or close to it, the bubbles travel a distance of tens or hundreds of meters before complete dissolution or complete hydration.

Geothermal analysis of boreholes in the Shenhu gas hydrate drilling area, northern South China Sea: Influence of mud diapirs on hydrate occurrence

Mud diapirs developed on the northern South China Sea continental slope are important indicators for gas hydrate exploration. The Guangzhou Marine Geological Survey (GMGS) of the Chinese Ministry of Land and Resources targeted mud diapirs and deployed gas hydrate drilling in the Shenhu area. Although an obvious bottom-simulating reflection (BSR) was detected below borehole number SH5, no gas hydrates were found at this borehole. Scientists encountered several contradictions when they analyzed the formation mechanism of hydrates related to mud diapirs. It was important to resolve this problem by sophisticated detection and thermodynamic analysis. In this study, we analyzed the thermodynamic mechanism of mud diapirs and their relationship to the occurrence of gas hydrates based on seismic profiles, mineral identification, sediment thermal conductivity measurements, and other available datasets. Our study concludes that gas hydrates were not detected at SH5 because a mud diapir pierced into the gas hydrate stability zone, leading to the decomposition of hydrates. The evolution of a mud diapir could be divided into three stages with a continuous geological process that controlled the accumulation of gas hydrates. The seismic profile and lithologic analysis showed that the mud diapir below SH5 was in the late stage of mud diapir evolution. The gas leakage system of the mud diapir was evident in the seismic profile, and the typical V-AMP (velocity-amplitude anomaly) structure displayed free gas accumulation under the BSR. The anaerobic oxidation of leaking methane promoted the formation of authigenic carbonate minerals. Thus, the deep layer of SH5 contained a relatively high percentage of carbonates and had a low thermal conductivity. In this stage, higher-temperature liquid migrated into the gas hydrate stability zone. The in situ temperature measured in this borehole was higher than the critical temperature of hydrate formation and decomposition. The liquid changed the temperature field of the region and altered the geothermal environment of hydrate accumulation, which led to the dissociation of hydrates.

The effect of a TEG additive on hydrate formation

ABSTRACTIn gas industry, gas hydrate formation has both advantages and disadvantages. The best advantage of gas hydrate is Persian Gulf water sweetening, carbon dioxide capture, and gas storage, and its drawbacks are pressure drop, plugging, and explosion in pipelines. In recent years, using the inhibitors to prevent hydrate formation is being considered among researchers. In this study, the new equilibrium data for hydrate formation of inlet natural gas to Gachsaran NGL-1200 refinery with addition of Tri ethylene glycol (TEG) with mass concentration of 5% and 15% in distilled and Persian Gulf waters were measured by constant-volume method. The experimental results show that the hydrate formation conditions will be hard with the increase of TEG concentration in distillated and Persian Gulf waters. In other words, TEG addition to Persian Gulf water had more inhibitory effect in hydrate formation than TEG addition to distilled water. The hydrate formation temperature, in pressure range of 28–29 bars, reduced 0.3°C and 2.7°C for distilled water and 2.8°C and 4.6°C for Persian Gulf water in presence of TEG with mass concentration of 5% and 15%, respectively.

Prediction of hydrate equilibrium conditions using k-nearest neighbor algorithm to CO2 capture

ABSTRACTGas or clathrate hydrates are an important issue when they form in the oil and gas pipelines. Since the determination of the hydrate formation temperature and pressure is very difficult experimentally for every gas system and it is impossible in terms of cost and time approximately, mathematical models can be useful tools to overcome these difficulties. In this study, k-nearest neighbor model was used to predict the equilibrium conditions of hydrate formation in absorption and separation of carbon dioxide from flue gas mixture, containing carbon dioxide and nitrogen. At the training phase, temperature and composition data of nitrogen and carbon dioxide in the flue gas mixture at equilibrium conditions and the equilibrium pressures of hydrate formation were used as input and output, respectively. The error percentage less than 0.38% indicates the high accuracy of the proposed model. In this study, 80%, 85%, and 90% of the training data are examined for three numbers of nearest. For three numbers of used nearest (k = 1, k = 2 and k = 3), the value of k = 1 leads to the lowest error; so, it is selected as the best nearest in the presented model.

Thermoresponsive Microcarriers for Smart Release of Hydrate Inhibitors under Shear Flow.

The hydrate formation in subsea pipelines can cause oil and gas well blowout. To avoid disasters, various chemical inhibitors have been developed to prevent or delay the hydrate formation and growth. Nevertheless, direct injection of the inhibitors results in environmental contamination and cross-suppression of inhibition performance in the presence of other inhibitors against corrosion and/or formation of scale, paraffin, and asphaltene. Here, we suggest a new class of microcarriers that encapsulate hydrate inhibitors at high concentration and release them on demand without active external triggering. The key to the success in microcarrier design lies in the temperature dependence of polymer brittleness. The microcarriers are microfluidically created to have an inhibitor-laden water core and polymer shell by employing water-in-oil-in-water (W/O/W) double-emulsion drops as a template. As the polymeric shell becomes more brittle at a lower temperature, there is an optimum range of shell thickness that renders the shell unstable at temperature responsible for hydrate formation under a constant shear flow. We precisely control the shell thickness relative to the radius by microfluidics and figure out the optimum range. The microcarriers with the optimum shell thickness are selectively ruptured by shear flow only at hydrate formation temperature and release the hydrate inhibitors. We prove that the released inhibitors effectively retard the hydrate formation without reduction of their performance. The microcarriers that do not experience the hydration formation temperature retain the inhibitors, which can be easily separated from ruptured ones for recycling by exploiting the density difference. Therefore, the use of microcarriers potentially minimizes the environmental damages.

Phase Equilibria of Carbon Dioxide Hydrates in the Presence of Methanol/Ethylene Glycol and KCl Aqueous Solutions

In this study, the experimental data for dissociation conditions of carbon dioxide hydrates in the presence of 0.05 and 0.1 mass fraction KCl solution + 0.1 and 0.2 mass fraction methanol and ethylene glycol were measured and then reported at different temperatures and pressure ranges not available in the related literature. The phase equilibrium curves were drawn using an isochoric pressure-search method. To validate the used apparatus and the experimental findings of the current study and also to show the inhibition effects of the aqueous solutions used in this study, the experimental values were compared with some selected experimental data from the literature about the dissociation conditions of carbon dioxide hydrates in the presence of pure water and aqueous solution with 0.05 mass fraction KCl. Finally, to examine the inhibitory effect of various inhibitors and their synergies on each other, the suppressed temperature for hydrate formation was evaluated in the presence of different inhibitor soluti...

Development of a hydrate formation prediction model for sub-sea pipeline

ABSTRACTIn this research work, a novel model is developed to the hydrate formation pressure and hydrate formation temperature for a single component of methane (CH4) gas. This research model holds at a temperature and pressure of real-time data for pure water, methane, and other mixtures of gases, respectively. Furthermore, the modelling and statistical analysis conducted in this research were divided into three major segments; the assessment of the computability of the mathematical models, the performance of the proposed optimization techniques, and the comparison of the proposed techniques with real-time data of gas pipeline. Results showed that the improved optimization algorithms are in admirable compliance with the real-time data. These correlations are providing the capability to predict gas-hydrate-forming conditions for a wide range of hydrate formation data.

Chemical Control of Natural Gas Hydrate

The study investigates chemical control of hydrates in pipeline by the application of different chemical substances such as methanol, ethylene glycol, diethylene glycol and triethylene glycol. Aspen Hysys simulator was used to determine hydrate formation temperature based on gas field composition and operating pressure by using Peng-Robinson equation. Similar simulations were carried out with the injection of chemical inhibitors such as methanol, ethylene glycol, diethylne glycol and triethylene glycol. The chemical inhibitors prevents hydrate formation by reducing hydrate formation temperature, thereby mitigating against hydrate formation and ensuring constant flow and production of fluid with methanol been the most effective chemical inhibitor based on the hydrate formation temperature reduction trends and analysis.

An improved Parrish-Prausnitz (P-P) model to predict the hydrate formation condition of natural gas with a high volume content of CO2

Predicting the hydrate formation condition is an important issue for determining high CO2 content natural gas transport. The widely used Parrish-Prausnitz (P-P) model cannot predict the hydrate formation temperatures and pressures accurately for high CO2 content natural gas. This paper introduced a simple correction factor into the P-P model, resulting in an improved P-P model. The analytical expression of this new parameter is developed by correlating the deviations of the predicted hydrate formation temperatures with the CO2 molar fraction in the gas mixtures. A total of 140 sets of experimental data were applied to validate the proposed model, which covered wide pressure and CO2 molar fraction ranges of 1.45–13.0 MPa and 0–90%, respectively. The results show that the improved P-P model balances a simple form with high accuracy. The average deviation of the improved P-P model is 0.098 °C, whereas that of the original P-P model is 2.424 °C. It is essentially comparable in its prediction ability to CSMGem software and the cell potential method when it is applied to predicting the hydrate temperatures of high CO2 content natural gases.

Development of a least squares support vector machine model for prediction of natural gas hydrate formation temperature

Hydrates always are considered as a threat to petroleum industry due to the operational problems it can cause. These problems could result in reducing production performance or even production stoppage for a long time. In this paper, we were intended to develop a LSSVM algorithm for prognosticating hydrate formation temperature (HFT) in a wide range of natural gas mixtures. A total number of 279 experimental data points were extracted from open literature to develop the LSSVM. The input parameters were chosen based on the hydrate structure that each gas species form. The modeling resulted in a robust algorithm with the squared correlation coefficients (R2) of 0.9918. Aside from the excellent statistical parameters of the model, comparing proposed LSSVM with some of conventional correlations showed its supremacy, particularly in the case of sour gases with high H2S concentrations, where the model surpasses all correlations and existing thermodynamic models. For detection of the probable doubtful experimental data, and applicability of the model, the Leverage statistical approach was performed on the data sets. This algorithm showed that the proposed LSSVM model is statistically valid for HFT prediction and almost all the data points are in the applicability domain of the model.

Phase equilibrium modelling of natural gas hydrate formation conditions using LSSVM approach

ABSTRACTThe formation of gas hydrates in industries and chemical plants, especially in natural gas production and transmission, is an important factor that can lead to operational and economic risks. Hence, if the hydrate conditions are well addressed, it is possible overcome hydrate-related problems. To that end, evolving an accurate and simple-to-apply approach for estimating gas hydrate formation is vitally important. In this contribution, the least square support vector machine (LSSVM) approach has been developed based on Katz chart data points to estimate natural gas hydrate formation temperature as function of the pressure and gas gravity. In addition, a genetic algorithm has been employed to optimize hyper parameters of the LSSVM. Moreover, the present model has been compared with five popular correlations and was concluded that the LSSVM approach has fewer deviations than these correlations so to estimate hydrate formation temperature. According to statistical analyses, the obtained values of MSE and R2 were 0.278634 and 0.9973, respectively. This predictive tool is simple to apply and has great potential for estimating natural gas hydrate formation temperature and can be of immense value for engineers who deal with the natural gas utilities.

An intelligent optimization–based prediction model for natural gas hydrate formation in a deepwater pipeline

ABSTRACTTemperature, pressure, and composition of gas mixtures in deepwater pipelines promote rapid formation of gas hydrates. To avert this dilemma, it is more significant to find out the temperature and pressure limits in gas hydrates formation of the deepwater pipeline. The objective of this research is to develop an optimization method that finds the optimal temperature and pressure profile for natural gas hydrate formation conditions and an error calculation method to find the realistic approach of the hydrate formation prediction model. A newly developed correlation model is computing the hydrate formation pressure and temperature for a single component of methane (CH4) gas. The proposed developed prediction model is based on the 2 and 15 constant coefficients and holds a wide range of temperature and pressure data about 2.64 to 46°C and 0.051 to 400 MPa for pure water and methane, respectively. The reducing error discrepancies are 1.2871, 0.35012, and 1.9052, which is assessed by GA, PSO, and GWO algorithms, respectively. The results show the newly developed optimization algorithms are in admirable compliance with the experimental data and standards of empirical models. These correlations are providing the capability to predict gas hydrate forming conditions for a wide range of hydrate formation data.

Prediction of phase equilibrium conditions for gas hydrates formed in the presence of cyclopentane or cyclohexane

In this work, we predicted the hydrate formation conditions for the pure and mixed gas systems of CH4, N2, O2 and CO2 in the presence of cyclopentane or cyclohexane. Chen-Guo model coupled with the predictive Soave-Redlich-Kwong (PSRK) group contribution method was used to calculate the three-phase equilibrium, and the UNIFAC model was employed to calculate the activity coefficient of the liquid phase. The pressure-corrected Henry’s law was employed to calculate the mole fraction of gas components existing in the aqueous phase except water. The prediction results and the percent of Absolute Average Deviation for the calculated hydrate formation pressures and temperatures were presented. It was found that the results predicted in this work agree well with those reported in the literature. Cyclopentane and cyclohexane in aqueous phase was assumed to evaporate into the gas phase and may change the gas components and the corresponding mole fractions in the gas phase. However, the results showed that the concentration variation of cyclopentane or cyclohexane has slight impact on the hydrate formation thermodynamics.