Effect of High Molecular Weight Asphaltenes on the Phase Stability of Methane Hydrates
Asphaltenes are heavy and polar fractions present in crude oil. Literature survey reveals that studies underlying the effect of individual components of crude oil on hydrate formation are rare. In this work, asphaltene fractions were extracted from a vacuum residue of the crude oil according to method based on IP143/90 (AlHumaidan et al., 2017) and characterized by FTIR, element analysis, SEM and MALDI-TOF MS. Thereafter, the effect of asphaltenes was studied on the phase stability of pure methane hydrate system at 1000 ppm and 10000 ppm concentration. It has been observed that the asphaltene plays an important role in elucidating the phase stability of methane hydrate systems.
Gas Hydrate Equilibrium Measurement of Methane + Carbon Dioxide + Tetrahydrofuran+ Water System at High CO2 Concentrations
Application of gas hydrate in separation of carbon dioxide (CO2) form nitrogen in Carbon Capture and Storage (CCS) chain is recently studied by many researchers. Tetrahydrofuran (THF) is suggested as promoter for this process. The same process can be suggested for separation of CO2 from methane (CH4) for gas treatment and sweetening, especially for high CO2 content mixtures such as landfill gas. The first step in development of such process is understanding of the phase boundary of this mixture at different pressure-temperature condition and gas/liquid composition. In this work, gas hydrate phase boundary of CH4, CO2, THF and water at different pressure from 4.5 to 8.1 MPa is experimentally measured. CO2 mole fraction in gas phase is fixed at 0.7 and THF concentration in the liquid phase set at 0.03 mole fraction. Results show that presence of THF in the mixtures shift the phase boundary to the lower pressure / higher temperature condition. This effect is favorable for industrial applications.
Semiclathrate hydrate of methane and quaternary ammonium salts for natural gas storage and gas separation
Methane is the smallest and cleanest burning fuel. It is found in the form of natural gas in which methane present in bulk but contains many impurities such as CO2, H2S which must be removed before being used by the consumer. In addition, it must be stored efficiently and transported economically. Gas hydrate is proposed to be one of the methods for storage, transportation and separation. A subclass of hydrate known as semiclathrate hydrate is capable of acting as a sieve for different sized gas molecules and have the capability to cohost smaller guest gases of specific size. Theses semiclathrate hydrate can be very useful for gas storage and multicomponent gas separation. In this work, a family of quaternary-ammonium salts such as tetra n-methyl/n-ethyl ammonium bromide (TMAB/TEAB) from the clan of tetra-alkyl ammonium bromide are examined at concentrations of 5wt% and 10 wt% for their phase stability along with the TBAB. Additionally, non-isothermal kinetics have been studied. Various experimental data have been obtained at different initial pressures of 8 MPa, 7.5 MPa, and 5.5 MPa to find out the influence of alkyl chain length on methane hydrate formation. It can be observed from experiential results that both TMAB and TEAB have shown thermodynamic inhibition as compared to TBAB. It can also be concluded from the phase stability curves that TBAB has more potential to aid in methane storage and separation than TMAB and TEAB at moderate pressure and temperature. An effect of carbon alkyl chain length is clearly seen on methane gas consumption. It has been witnessed that gas storage in hydrate increases with increase in the alkyl chain length of the salts. From this study, TBAB has found to be a more promising agent for gas processing and methane storage in the form of gas hydrate.
Bioremediation of costal and marine pollution due to crude oil using a microorganism Bacillus subtilis
Marine and costal pollution has become a global concern in recent years due to the increase in intensity of contaminants in the marine environment. The release of crude oil in the marine environment during exploitation and transportation cause serious environmental pollution, owing to the presence of toxic organic compounds. Crude oil, which is the most predominant energy resource throughout the word is the complex mixtures of hydrocarbons including more than 70% of alkanes along with aromatics, naphthenes and resins. The long chain alkanes present in the crude oil remains persistent due to its non-volatile nature and pose a major menace to terrestrial and marine ecosystems. Biodegradation has emerged as a potential and economical technology for the restoration of oil spilled environment. It provides efficient, economical and environment friendly solution for on-shore and off-shore oil spill remedies. The present study investigates the degradation of crude oil using a biosurfactant producing microorganism 'Bacillus subtilis' to obtain maximum degradation. Bacillus subtilis isolated from polymer dump site, Chennai, India was used for the degradation of crude oil. Crude oil degradation and viscosity reduction was observed to be 80% and 60%, respectively, in 10 days. The high microbial adherence, surface tension reduction, emulsification activity, production of higher amount of biosurfactant, stability of the produced biosurfactant at extreme environment conditions, viscosity reduction and high rate of degradation indicates the potential of the microorganism for oil spill treatment.
Enhancement of flow assurance by the degradation of wax using pseudomonas fluorescens
Conventional oil reserves are under production past several years, leaving the higher end hydrocarbons (paraffins/waxes) in the reservoir. The separation and deposition of these waxy components in the production and surface facilities are predominant when the system temperature reduces below the wax appearance temperature (WAT) during the flow of crude oil from a reservoir to the surface. It is, therefore, necessary to address various challenges posed by long chain paraffins using an economical, versatile, and eco-friendly technique. In the current scenario, microbial degradation of paraffins has gained considerable attention because of its environmentally friendly and operationally safer nature than other methods for sustainable development. In this study, the bio-surfactant producing microorganism Pseudomonas fluorescens, isolated from the marine port in Chennai, India, is used to degrade a wax sample, namely eicosane. The viscosity reduction and the delay in wax appearance temperature has been noticed. This study also analyzes the physico-chemical characteristics of the bio-surfactant produced by the microbe. The degradation of long chain paraffin to short chain molecule is confirmed by the gas chromatography-mass spectrometry (GCMS) result. From the GCMS results, it has been observed that 93% of the wax degraded in 10 days. The amount of bio-surfactant produced by the microbe is found to be as high as 9.5 g/L. The high surface tension reduction, production of higher amount of bio-surfactant, viscosity reduction and high rate of degradation indicates the potential of the microbe in flow assurance, oil-spill, enhanced oil recovery, etc.
A strategic approach for the development of next generation reservoir simulators
In present scenario the applications of numerical reservoir simulators are very wide and extensive. Simulation is the only tool to describe quantitatively multi-phase flow in a heterogeneous reservoir. But, nowadays most of the users of reservoir simulators are becoming the hostages of computer- generated results, even though, many incorrect analysis techniques, mathematical models and computational approaches are used extensively in reservoir simulation study. This paper revealing such incorrect but commonly accepted approaches presents alternate and correct mathematical approaches for the advancement of simulators. First of all authors take privilege of their previous work where, through wide literature survey, various examples (e.g. fracture and shale flow solutions where fine mesh discretization technique may lead to erroneous results due to singular velocities at the fracture and shale tips, fracture flow modeling using discrete point source which was replaced by continuous line source, etc.) of incorrect models were shown and proved to be the source of erroneous results and numerical instability [5]. After revealing such incorrect models, the solutions for eliminating this incorrect techniques and models are presented and proved numerically and analytically. Mathematical techniques and formulations used in this paper are finite element method, finite volume method, advanced conformai mapping, streamfunction and streamline tracing, modern singular integral equation approaches, moving boundary value problems technique, artificial viscosity analysis, generalization of coordinate system, curvilinear grid generation, integral transformations, etc., which stabilize the mentioned simulation models. The recent technological innovations in drilling and production and complicated reservoir studies have challenged the existing simulators so is the key target of this paper is to move in direction of the next generation simulators that can solve the various mentioned inaccuracies. Various accurate mesh generation algorithms are anticipated to develop through this paper to revolutionize the modern reservoir simulation study. Copyright 2012, Society of Petroleum Engineers.
Nanoparticle stabilized solvent-based emulsion for enhanced heavy oil recovery
The objective of this study is to develop a solvent-based Pickering emulsion stabilized by silica nanoparticle for enhanced heavy oil recovery. Unlike the light oil, the recovery of heavy oil is quite challenging because of its high viscosity. To reduce the viscosity of heavy crude oil, solvent-based Pickering emulsion is explored to improve the recovery of heavy oil. The approach is to use solvent-in-water emulsion stabilized by nanoparticle which is more economical as compared to thermal or solvent-based enhanced oil recovery (EOR) methods. In this work, the solvent-in-water Pickering emulsion has been prepared by homogenizing the mixture with the help of homogenizer at 13000 rpm for 3 minutes. It can be inferred from the experimental results that the use of nanoparticle has helped to improve the stability of solvent-based Pickering emulsion for a longer period of time as compared to conventional surfactant based emulsions due to irreversible adsorption of silica nanoparticle at the oil-water interface. The silica nanoparticle of 15 nm size is used to make the Pickering emulsion. The colloidal stability and surface charge of the nanoparticle is evaluated by zeta potential. Silica nanoparticle is expected to improve the rheological stability of solvent-based emulsion and provides favorable mobility. Hence, these solvent-based emulsion flooding can provide high displacement efficiencies like miscible solvent flooding and better sweep efficiency like polymer flooding and helps to improve the enhanced heavy oil recovery. The novelty of the nanoparticle stabilized solvent-based Pickering emulsion is that it can sustain harsh reservoir conditions and remains very stable for a longer period of time as compared to other EOR techniques. The droplet size of these emulsions is few micron in size so that it can easily flow through the pore throat size of the formation reservoir and helps in improving the enhanced heavy oil recovery.
Accurate phase equilibria predictions for hydrates of multi-component natural gases
The sour natural gas at higher temperatures and lower pressures readily forms hydrates and stays stable and hence are responsible for plugging and causing flow assurance related issues. Predictions of formation and dissociation conditions of these hydrates are necessary in applications for preventing such hazards primarily due to the blockages of pipelines. However, natural gases from the gas reservoirs can have combinations of different concentrations of each of the following constituents, CH4, C2H6, C 3H8, C4H10, N2, C0 2 and H2S. Presence of C02 and/ or H 2S in the natural gas leads to the corrosion of the offshore pipelie installations, which are difficult to access and fix. Presence of high concentrations of C02 and/ or H2S along with other components often found in natural gas, confines the accurate functioning of several of the available phase behavior models. The major limitation for their inaccuracy can be attributed to the association of C02 and H 2S in hydrate system. In the present work, a new thermodynamic computing approach is developed for predicting the phase equilibria for hydrates of multicomponent sour natural gases (with C02 and H2S) from different natural gas systems. The model of Chen and Guo is extended for multicomponent sour natural gas hydrate system using the Kihara potential functions to model the guest-host interaction energies. Adjacently, a semi-empirical form is proposed to calculate the equilibrium hydrate temperature for hydrates of natural gas with and without C02 and H2S. The developed model is fitted with experimental data on the phase equilibria of sour natural has hydrate system and found to be satisfactory. The average absolute deviation pressure percentage (AADP %) for most of the cases studied is observed to be well within 10%, thus proving its efficiency. The present model can, therefore, find prospective applications for developing mitigation techniques to address flow assurance issues as well as for robust natural gas and hydrate reservoir models containing sour gases. Copyright 2014, Offshore Technology Conference.
Modeling of methane hydrate inhibition in the presence of green solvent for offshore oil and gas pipeline
In offshore gas transmission pipeline systems, typically gas and water are produced under high pressure and low temperature conditions causing the formation of gas hydrates blocking pipelines. Thermodynamic modeling is necessary to understand the phase stability of hydrate in the presence of green solvents namely, ionic liquids (ILs). In this work, the thermodynamic models are based on the computation of fugacity of hydrate phase using Van der Waals and Platteeuw solid solution theory combined with Peng - Robinson equation of state (PR-EoS) for fugacity of hydrate former in the gas phase and the computation of fugacity of aqueous water phase using activity coefficient models such as the non - random two - liquid (NRTL) model and Pitzer - Mayorga model. The model results are compared with available experimental data from open literature and observed to be in good agreement with the reported literature. Finally, the hydrate suppression temperature due to ILs on methane hydrate is calculated to know the inhibition effectiveness of IL on methane hydrate formation in offshore pipeline system. The overall accuracy of Pitzer-Mayorga model is found to be 5.8 % while NRTL model's accuracy was 6.3 % for various ILs and methane hydrate system. Model results further indicated that ILs with shorter alkyl chain length exhibit better inhibition effect. The model developed in this work shows potential application in the determination of hydrate phase stability using green solvent for offshore oil field applications. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).
Investigations on gas trapping phenomena for different EOR-water alternate gas injection methodologies
Water Alternate Gas (WAG) injection methods are the derivative of gas injection methods, wherein water and gas are injected intermittently. WAG injection can lead to improved oil recovery by combining better mobility control and contacting upswept zones and by leading to improved microscopic displacement. Gas trapping in the reservoir after WAG process is an important parameter that affects the recovery of oil. Trapped gas refers to the immobile gas saturation remaining after the rock is flooded with oil or water. Trapped gas creates significant hysteresis effect (during drainage and imbibition) and reduces the relative permeability of water in the mixed wet or oil wet reservoirs. In this work, gas trapping phenomena is presented for different WAG methods for a Indian Brownfield, namely, single, five cycle WAG, tapered WAG, five cycle WAG with Hydrocarbon gas (HC) and CO 2 gas. Experiments are carried out on the recombined fluid in the core flooding apparatus at the reservoir conditions. The crude oil and gas is obtained from the separator at separator conditions and recombined at the reservoir conditions of 120°C and 230 kg/cm 2 at reservoir gas-oil ratio (GOR) to become representative of the reservoir fluid. The actual core sample is obtained from the field and is used for the study. The water and gas injection rate used for this study are 20 and 10 cc/hr, respectively, for all the experimental studies. Two types of gases are used for WAG method, namely, hydrocarbon gas (collected from the field and having about 90 % methane by composition in mole %) and CO 2 gas. The results on the saturation of phases and Land's trapping constant have been calculated for several cases of production life cycle and for different WAG methods.