Jitendra S. Sangwai

Modeling phase equilibria of semiclathrate hydrates of CH4, CO2 and N2 in aqueous solution of tetra-n-butyl ammonium bromide

Abstract Semiclathrate hydrates of tetra- n -butyl ammonium bromide (TBAB) offer potential solution for gas storage, transportation, separation of flue gases and CO 2 sequestration. Models for phase equilibria for these systems have not yet been developed in open literatures and thus require urgent attention. In this work, the first attempt has been made to model phase equilibria of semiclathrate hydrates of CH 4 , CO 2 and N 2 in aqueous solution of TBAB. A thermodynamic model for gas hydrate system as proposed by Chen and Guo has been extended for semiclathrate hydrates of gases in aqueous solution of TBAB. A correlation for the activity of water relating to the system temperature, concentration of TBAB in the system and the nature of guest gas molecule has been proposed. The model results have been validated against available experimental data on phase equilibria of semiclathrate hydrate systems of aqueous TBAB with different gases as guest molecule. The extended Chen and Guos model is found to be suitable to explain the promotion effect of TBAB for the studied gaseous system such as, methane, carbon dioxide and nitrogen as a guest molecule. Additionally, a correlation for the increase in equilibrium formation temperature (hydrate promotion temperature, Δ T p ) of semiclathrate hydrate system with respect to pure gas hydrate system has been developed and applied to semiclathrate hydrate of TBAB with several gases as guest molecules. The developed correlation is found to predict the promotion effect satisfactorily for the system studied.

Viscosity of the oil-in-water Pickering emulsion stabilized by surfactant-polymer and nanoparticle-surfactant-polymer system

Information on the viscosity of Pickering emulsion is required for their successful application in upstream oil and gas industry to understand their stability at extreme environment. In this work, a novel formulation of oil-in-water (o/w) Pickering emulsion stabilized using nanoparticle-surfactant-polymer (polyacrylamide) system as formulated in our earlier work (Sharma et al., Journal of Industrial and Engineering Chemistry, 2014) is investigated for rheological stability at high pressure and high temperature (HPHT) conditions using a controlled-strain rheometer. The nanoparticle (SiO2 and clay) concentration is varied from 1.0 to 5.0 wt%. The results are compared with the rheological behavior of simple o/w emulsion stabilized by surfactant-polymer system. Both the emulsions exhibit non-Newtonian shear thinning behavior. A positive shift in this behavior is observed for surfactant-polymer stabilized emulsion at high pressure conditions. Yield stress is observed to increase with pressure for surfactant-polymer emulsion. In addition, increase in temperature has an adverse effect on the viscosity of emulsion stabilized by surfactant-polymer system. In case of nanoparticle-surfactant-polymer stabilized o/w emulsion system, the viscosity and yield stress are predominantly constant for varying pressure and temperature conditions. The viscosity data for both o/w emulsion systems are fitted by the Herschel-Bulkley model and found to be satisfactory. In general, the study indicates that the Pickering emulsion stabilized by nanoparticle-surfactant-polymer system shows improved and stable rheological properties as compared to conventional emulsion stabilized by surfactant-polymer system indicating their successful application for HPHT environment in upstream oil and gas industry.

Use of Oil-in-water Pickering Emulsion Stabilized by Nanoparticles in Combination With Polymer Flood for Enhanced Oil Recovery

Efficient flooding agents are required to produce additional oil from mature reservoir. In this work, oil-in-water Pickering emulsion systems stabilized using nanoparticles, surfactant, and polymer have been developed and tested for enhanced oil recovery with and without a conventional polymer flood. Stability of nanoparticles in the dispersion of surfactant-polymer solution was tested using zeta-potential before use. Several flooding experiments have been conducted using Berea core samples at 13.6 MPa and temperatures of 313 and 353 K. It has been observed that a combination of 0.5 PV polymer flood with 0.5 PV Pickering emulsion was efficient and have resulted in 1–6% additional oil recovery as compared to 0.5 PV Pickering emulsion flooding alone. The injection of polymer flood have shown to enhance the pressure drop in the core sample after emulsion flooding and considered as an important factor for an additional recovery of oil. The effect of temperature on the viscosity of flooding agents in relation to pressure drop and oil recovery have also been investigated. Viscosity and pressure drop of emulsion flood systems have shown to marginally decrease with increase in temperature. Studies on nanoparticle retention using SEM have shown that nanoparticles were retained in the core sample during emulsion flooding which may be detrimental for permeability of core sample. It is observed that Pickering emulsion flood with polymer flood would be effective for the enhanced oil recovery suitable for matured reservoirs.

Experimental investigations on the phase equilibrium of semiclathrate hydrates of carbon dioxide in TBAB with small amount of surfactant

Experimental studies are carried out on a semiclathrate hydrate system of carbon dioxide in tetra-n-butyl-ammonium bromide (TBAB) with a small amount of surfactant, sodium dodecyl sulfate (SDS), for 5, 10, and 20 wt.% TBAB to determine the phase equilibrium temperature and pressure conditions. It is observed that the presence of SDS did not influence the equilibrium conditions of the semiclathrate hydrate. Re-nucleation (memory) effect of semiclathrate hydrates of CO2 is studied for few cases of TBAB concentration in an aqueous solution. The equilibrium pressure and temperature conditions obtained for memory effect and regular experimental run without memory effect were observed to be quite close. It is concluded that in the case of no memory effect, with increasing TBAB percentage in the system, the time required for nucleation is reduced. For the same TBAB concentration, the incipient pressure and temperature required for nucleation and re-nucleation of semiclathrate hydrates increase while the time required for re-nucleation decreases.

Enhanced oil recovery using oil-in-water (o/w) emulsion stabilized by nanoparticle, surfactant and polymer in the presence of NaCl

A conventional waterflood often leads to unsuccessful recovery of oil, as most of the injected water tends to channel into the more permeable zones. Pickering emulsions stabilized using surfactant and colloidal particles, such as nanoparticles, are gaining wider recognition in the petroleum industry due to their better thermal stability and stabilized flow behavior. In this work, a novel formulation of oil-in-water (o/w) emulsion stabilized using nanoparticle–surfactant–polymer in the presence of salt (NaCl) is investigated for improved oil recovery at conditions of high pressure (13.6 MPa) and high temperature (313–363 K). We report a comparative study of performance of o/w emulsion flooding with conventional water flooding for enhanced oil recovery of a crude oil having a viscosity of 161 mPa s at 313 K in a Berea sandstone core using core-flood experiments. The results of core flooding tests show that an incremental oil recovery of more than 23% of original oil in place over water flooding can be obtained using an emulsion flooding formulated in this work.

Eco-efficient and green method for the enhanced dissolution of aromatic crude oil sludge using ionic liquids

The upstream petroleum industry faces operational and technical problems due to increased deposition of waxes, aromatics and asphaltene from crude oil sludge in oil storage tanks in the form of tank-bottom sludge (TBS). This results in huge production losses, and threatens environmentally safe operation; therefore, safer solutions are needed. In this work, nine aromatic ionic liquids (ILs) are synthesized and tested for the dissolution of TBS with the aid of five solvents, namely, toluene, heptane, decane, ethyl acetate and hexane. The UV absorbance values of the standard solutions (TBS in solvent) are compared with the sample solutions (TBS in solvent + ILs). It is observed that ILs significantly improve the dissolution of TBS in solvents compared with neat solvent alone. Different weight ratios of TBS : ILs (1 : 1, 1 : 0.5 and 1 : 0.1) are considered in this study. Ionic liquids (ILs) based on an imidazolium cation and various anions, such as [Cl]−, [Br]−, [BF4]−, [H2PO4]−, [HSO4]−, and [PF6]−, are considered in this investigation. It is observed that the dissolution of TBS in heptane in the presence of [HMIM]+[Br]− is efficient to a maximum extent of 66% with other solvents showing similar increased solubility effect with various ILs. In the case of hexane, it should be noted that the efficiency of dissolution of TBS goes on decreasing with increasing concentration of TBS in hexane. A hold-time study is also performed with heptane containing ILs and heptanes without ILs to determine the maximum time required for efficient dissolution of TBS. It is observed that the efficiency is increased beyond 66% in the presence of ILs for the dissolution of TBS in heptane, provided that the mixture of solvent and ILs are in contact with the TBS for a prolonged period of 30 days, or even longer as required. FT-IR and 13C-NMR spectral analyses are also performed so as to understand the efficiency of the ILs in the dissolution of TBS in various solvents, and it was observed that there is a decrease in the intensity of the peaks in the spectra of treated TBS with solvents, which is further enhanced by the addition of ILs.

Applications of Nanotechnology for Upstream Oil and Gas Industry

Oil and Gas industry is going through a phase where there is an increased demand of energy sources (particularly oil and gas) and reduced production due to mature oilfields. There is a need for new technologies which can help improve production from the reservoir and develop new fields. Nanotechnology offers promising solution for the same. Nanotechnology is the study of science of materials at nanoscale which help in enhancing the performance of processes. Nanoparticles are the nanosized materials in the range of 1-100 nm. Nanoparticles have high specific surface area and unique properties, such as high adsorption potential and heat conductivity. These particles when mixed with base fluids, also called as nanofluids, and used for several application related to upstream oil and gas industry, help improve the performance of several processes. The use of nanoparticle in exploration and production is an attractive tool for petroleum engineers that have been improved by many researchers in recent years. This paper discusses about how the nanotechnology plays an important role in an upstream oil and gas industry which includes exploration, drilling, and completion, production and enhanced oil recovery operation.

High pressure rheology of gas hydrate formed from multiphase systems using modified Couette rheometer

Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as gas hydrates. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane hydrate formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any hydrates in situ and thus failed to measure rheological properties during hydrate formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming gas hydrate from the gas-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure gas hydrate viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of hydrate slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the hydrate dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of gas hydrate formed from various systems containing promoters and inhibitors in the context of flow assurance.

Production performance of water alternate gas injection techniques for enhanced oil recovery: effect of WAG ratio, number of WAG cycles and the type of injection gas

Production performance of a water alternate gas injection (WAG) method has been reported for the effect of several operating parameters, such as, WAG injection cycles, viz., single cycle WAG and five-cycle WAG and the tapered WAG at the reservoir conditions of 120°C and 230 kg/cm2 for hydrocarbon gas and CO2 gas. It is observed that the number of cycles in the WAG injection process affects the recovery of oil from the core sample. It is observed that the tapering in the WAG injection process improves the recovery of oil initially in place. The observations on the effect of gases revealed that the CO2 gas with five-cycle WAG process gives higher incremental recovery than the five cycle WAG process using hydrocarbon gas. It is observed that the saturation profile of CO2 WAG injection shows the better gas saturation in the core as against the hydrocarbon gas in the WAG process.

Analysis of Flow through Ocean Energy Harvesting Bidirectional Impulse Turbine

Oscillating water column based wave energy device uses bi-directional flow impulse turbine. In this paper, a computational analysis of an impulse turbine has been performed using Ansys-CFX 14.0 code. Initially, a CAD model was prepared and unstructured meshing strategy was implemented in the flow domain. Reynolds-averaged Navier Stokes equations were solved to analyse the fluid flow properties. The efficiency, torque coefficient and input coefficient were compared for the evaluations. The flow features through the turbine shows that the flow separation occurs near the trailing edge of the suction surface of the blade.