JFTS+H: A Julia-Based Parallel Simulator for the Description of the Coupled flow, Thermal and Geochemical Processes in Hydrate-Bearing Geologic Media

2021 ◽  
Author(s):  
Kotaro Anno ◽  
George J. Moridis ◽  
Thomas A. Blasingame
Keyword(s):  
Programming Language ◽  
Gas Hydrate ◽  
Computational Efficiency ◽  
Message Passing Interface ◽  
Jacobian Matrix ◽  
Water Soluble ◽  
Geochemical Processes ◽  
Persistent Problem ◽  
Flow And Transport ◽  
Geologic Media

Abstract The objectives of this study are to develop (a) the Julia Flow and Transport Simulator (JFTS), a serial and parallel, high performance non-isothermal, multi-phase, multi-component general simulator of flow and transport through porous/fractured media, and (b) an associated module that describes quantitatively the Equation-of-State (EOS) of the complete H2O+CH4 system by covering all combinations of phase coexistence that are possible in geologic media and including all the regions of the phase diagram that involve CH4-hydrates. The resulting simulator (hereafter referred to as the JFTS+H code) can describe all possible scenarios of hydrate occurrence, dissociation and formation/evolution and is to be used for the investigation of problems of (a) gas production from natural CH4-hydrate accumulations in geologic media, as well as for (b) the analysis of any laboratory experiments involving CH4-hydrates. As indicated by the JFTS name, this simulator is written in the Julia programming language and its parallelization is based on the Message Passing Interface (MPI) approach. The JFTS+H simulator is a fully-implicit, Jacobian-based compositional simulator that describes the accumulation, flow and transport of heat, and up to four mass components (H2O, CH4, CH4-hydrate and a water-soluble inhibitor) distributed among four possible phases (aqueous, gas, hydrate, and ice) in complex 3D geologic systems. The dissociation and formation of CH4-hydrates can be described using either an equilibrium or a kinetic model. The automatic derivate capability of Julia greatly simplifies and enhances the Jacobian computations. The MPI Interface (Blaise, 2019) is implemented in all components of the code, and the METIS library (Karypis, 2013) is used for the domain decomposition needed for the effective parallelization of the solution of the Jacobian matrix equation that is accomplished using the LIS library (Nishida, 2010) of parallel Conjugate Gradient solvers for large systems of simultaneous linear equations. The JFTS+H code can model the fluid flow, thermal and geochemical processes associated with the formation and dissociation of CH4-hydrates in geological media, either in laboratory or in natural hydrate accumulations. This code can simulate any combination of the three possible gas hydrate dissociation methods (depressurization, thermal stimulation, and inhibitor effects), and computes all associated parameters describing the system behavior. The JFTS+H results show very good agreement with solutions of standard reference problems, and of large 2D and 3D problems obtained from another well-established and widely used numerical simulator. The code exploits the speed, computational efficiency and low memory requirements of the Julia programming language. The parallel architecture of JFTS+H addresses the persistent problem of very large computational demands in serial hydrate simulations by using multiple processors to reduce the overall execution time and achieve scalable speedups. The code minimizes communications between processors and maximizes computations within the same computational node, which has important consequences (especially when coupled with the automatic derivative capabilities of Julia) on performance in the development of the Jacobian matrix. An optimal LIS solver is recommended for this type of problem after evaluating different options. This approach provides both speedup and computational efficiency results when different numbers of processors are called in the solution process. This work is believed to be the first application of Julia (a new, highly efficient language designed for demanding scientific computations) to create a simulator for flow and transport in porous media. JFTS+H is a fast, robust parallel simulator that uses the most recent scientific advances to account for all known processes in a dynamic hydrate system and works seamlessly on any computational platform (from laptop computers to workstations, to clusters and supercomputers with thousands of processors).

scholarly journals Application of Seq2Seq Models on Code Correction

2021 ◽  
Vol 4 ◽  
Author(s):  
Shan Huang ◽  
Xiao Zhou ◽  
Sang Chin
Keyword(s):  
Transfer Learning ◽  
Programming Language ◽  
Computational Efficiency ◽  
Test Suite ◽  
Classification Task ◽  
Repair Rate ◽  
Error Type ◽  
Memory Efficiency ◽  
Type Classification ◽  
Software Assurance

We apply various seq2seq models on programming language correction tasks on Juliet Test Suite for C/C++ and Java of Software Assurance Reference Datasets and achieve 75% (for C/C++) and 56% (for Java) repair rates on these tasks. We introduce pyramid encoder in these seq2seq models, which significantly increases the computational efficiency and memory efficiency, while achieving similar repair rate to their nonpyramid counterparts. We successfully carry out error type classification task on ITC benchmark examples (with only 685 code instances) using transfer learning with models pretrained on Juliet Test Suite, pointing out a novel way of processing small programming language datasets.

Gas hydrate nucleation and growth in the presence of water-soluble polymer, nonionic surfactants, and their mixtures

2020 ◽  
Vol 82 ◽  
pp. 103491 ◽  
Author(s):  
Anton P. Semenov ◽  
Rais I. Mendgaziev ◽  
Andrey S. Stoporev ◽  
Alexandra A. Kuchierskaya ◽  
Andrei A. Novikov ◽  
...  
Keyword(s):  
Gas Hydrate ◽  
Nonionic Surfactants ◽  
Nucleation And Growth ◽  
Water Soluble ◽  
Soluble Polymer ◽  
Water Soluble Polymer

Development and Implementation of Green Inhibitors of Gas Hydrate Formation in the Fields of Western Siberia

2021 ◽  
Author(s):  
Aleksander Voloshin ◽  
Nikolay Nifantiev ◽  
Mikhail Egorov ◽  
Robert Alimbekov ◽  
Vladimir Dokichev
Keyword(s):  
Molecular Weight ◽  
Gas Hydrate ◽  
Induction Time ◽  
Western Siberia ◽  
Inhibition Efficiency ◽  
Hydrate Formation ◽  
Water Soluble ◽  
Hydrocarbon Gases ◽  
Green Inhibitors ◽  
Gas Hydrate Formation

Abstract The effect of biodegradable polysaccharides – sodium (NaCMC) and ethanolammonium salts of carboxymethylcellulose, dextran and arabinogalactan on the process of gas hydrate formation was studied in order to search for new "green" inhibitors of low-concentration gas hydrate formation. The ability of polysaccharides to inhibit gas hydrate formation was studied in a quasi-equilibrium thermodynamic experiment. A mixture of hydrocarbon gases with a composition typical of the composition of petroleum gas and containing 78% methane was used as a gas-hydrate-forming model medium. It was found that in concentrations of 0.005, 0.0065 and 0.008%, dextran, NaCMC and arabinogalactan as thermodynamic inhibitors exceed methanol by 170-270 times in inhibitory properties. Dextran is superior to NaCMC and arabinogalactan in terms of inhibition efficiency, reduction of gas hydrate formation rate and induction time. Since with an increase in the concentration of polysaccharides, the pressure drop of gas hydrate formation increases and the rate of formation of gas hydrates decreases according to the mechanism of action, the studied polysaccharides can be attributed to both thermodynamic and kinetic inhibitors. It is established that the molecular weight of water-soluble polysaccharides has a significant effect on their inhibitory properties. A polysaccharide with a molecular weight of 250,000 demonstrated the highest inhibitory activity among the studied samples of NaCMC, which is 400 times more effective than methanol. NaCMC with a mass of 700 thousand did not have any effect on the formation of hydrates. Among the ethanolammonium salts, the monoethanolammonium salt CMC showed the greatest effectiveness in inhibiting the formation of tetrahydrofuran hydrates. An increase in its concentration from 0.02 to 0.1% leads to an increase in the induction time required for the nucleation and subsequent growth of crystals by 10 times. When switching from mono - to di - and triethanolammonium salts of carboxymethylcellulose, the inhibition efficiency decreases. It is shown that sodium and ethanolammonium salts of carboxymethylcellulose, arabinogalactan and dextran are promising for creating new "green" highly effective inhibitors of gas hydrate formation on their basis. The results of laboratory and field tests of the preparative form of the "green" gas hydrate formation inhibitor at the fields of Western Siberia are presented. It was found that at dosages of 500 g/m3 or less, there is no formation of hydrate plugs in the annulus of wells.

scholarly journals A Parallel Approach for Multi-GNSS Ultra-Rapid Orbit Determination

2021 ◽  
Vol 13 (17) ◽  
pp. 3464
Author(s):  
Chunhua Jiang ◽  
Tianhe Xu ◽  
Wenfeng Nie ◽  
Zhenlong Fang ◽  
Shuaimin Wang ◽  
...  
Keyword(s):  
Computational Efficiency ◽  
Orbit Determination ◽  
Message Passing ◽  
Message Passing Interface ◽  
High Efficiency ◽  
Normal Equation ◽  
Parallel Optimization ◽  
Observation Data ◽  
Computation Efficiency ◽  
Update Frequency

Global Navigation Satellite System (GNSS) ultra-rapid orbit is critical for geoscience and real-time engineering applications. To improve the computational efficiency and the accuracy of predicted orbit, a parallel approach for multi-GNSS ultra-rapid orbit determination is proposed based on Message Passing Interface (MPI)/Open Multi Processing (OpenMP). This approach, compared with earlier efficient methods, can improve the efficiency of multi-GNSS ultra-rapid orbit solution without changing the original observation data and retaining the continuity and consistency of the original parameters to be estimated. To obtain high efficiency, three steps are involved in the approach. First and foremost, the normal equation construction is optimized in parallel based on MPI. Second, equivalent reduction of the estimated parameters is optimized using OpenMP parallel method. Third, multithreading is used for parallel orbit extrapolation. Thus, GNSS ultra-rapid orbit determination is comprehensively optimized in parallel, and the computation efficiency is greatly improved. Based on the data from MGEX and IGS stations, experiments are carried out to analyze the performance of the proposed approach in computational efficiency, accuracy and stability. The results show that the approach greatly improves the efficiency of satellite orbit determination. It can realize 1-h update frequency for the multi-GNSS ultra-rapid orbit determination using 88 stations with four-system observations. The accuracy of the GPS, GLONASS, Galileo and BDS ultra-rapid orbit with 1-h update frequency using the parallel approach is approximately 33.4%,31.4%,40.1% and 32.8% higher than that of the original orbit, respectively. The root mean squares (RMS) of GPS, GLONASS, Galileo and BDS predicted orbit are about 3.2 cm, 5.1 cm, 5.6 cm and 11.8 cm. Moreover, the orbit provided by the proposed method has a better stability. The precision loss of all parallel optimization can be negligible and the original correlation between the parameters is fully preserved.

Parallel Linear Equation Solvers and OpenMP in the Context of Multibody System Dynamics

2009 ◽  
Author(s):  
Francisco Gonza´lez ◽  
Alberto Luaces ◽  
Daniel Dopico ◽  
Manuel Gonza´lez
Keyword(s):  
System Dynamics ◽  
Linear Equation ◽  
Computational Efficiency ◽  
Message Passing Interface ◽  
Multibody System ◽  
Simulation Software ◽  
Multibody System Dynamics ◽  
Code Structure ◽  
Wide Range ◽  
Multibody Problems

Computational efficiency of numerical simulations is a key issue in multibody system (MBS) dynamics, and parallel computing is one of the most promising approaches to increase the computational efficiency of MBS dynamic simulations. The present work evaluates two non-intrusive parallelization techniques for multibody system dynamics: parallel sparse linear equation solvers and OpenMP. Both techniques can be applied to existing simulation software with minimal changes in the code structure; this is a major advantage over MPI (Message Passing Interface), the de facto standard parallelization method in multibody dynamics. Both techniques have been applied to parallelize a starting sequential implementation of a global index-3 augmented Lagrangian formulation combined with the trapezoidal rule as numerical integrator, in order to solve the forward dynamics of a variable number of loops four-bar mechanism. This starting implementation represented a highly optimized code, where the overhead of parallelization would represent a considerable part of the total amount of elapsed time in calculations. Several multi-threaded solvers have been added to the original software. In addition, parallelizable regions of the code have been detected and multi-threaded via OpenMP directives. Numerical experiments have been performed to measure the efficiency of the parallelized code as a function of problem size and matrix filling ratio. Results show that the best parallel solver (Pardiso) performs better than the best sequential solver (CHOLMOD) for multibody problems of large and medium sizes leading to matrix fillings above 10 non-zeros per variable. OpenMP also proved to be advantageous even for problems of small sizes, in despite of the small percentage of parallelizable workload with respect to the total burden of the execution of the code. Both techniques delivered speedups above 70% of the maximum theoretical values for a wide range of multibody problems.

Application of various water soluble polymers in gas hydrate inhibition

2016 ◽  
Vol 60 ◽  
pp. 206-225 ◽  
Author(s):  
Muhammad Shahzad Kamal ◽  
Ibnelwaleed A. Hussein ◽  
Abdullah S. Sultan ◽  
Nicolas von Solms
Keyword(s):  
Gas Hydrate ◽  
Water Soluble ◽  
Water Soluble Polymers ◽  
Soluble Polymers

scholarly journals Multi-functional oilfield production chemicals: maleic-based polymers for gas hydrate and corrosion inhibition

2021 ◽  
Vol 1201 (1) ◽  
pp. 012081
Author(s):  
M A Kelland ◽  
J Pomicpic ◽  
R Ghosh ◽  
C Undheim ◽  
T H Hemmingsen ◽  
...  
Keyword(s):  
Natural Gas ◽  
Corrosion Inhibition ◽  
Gas Hydrate ◽  
Open Circuit ◽  
Gas Production ◽  
Water Soluble ◽  
Test Method ◽  
Production Flow ◽  
Flow Lines ◽  
Better Than

Abstract Several chemical problems can occur during the production of oil and gas through flow lines. This includes corrosion, scale deposition and gas hydrate plugging. Three separate chemicals may be needed to treat these issues. Kinetic hydrate inhibitors (KHIs) are used in cold oil or natural gas production flow lines to prevent the formation and plugging of the line with gas hydrates. They are often injected concomitantly with other production chemicals such as corrosion and scale inhibitors. KHIs are specific low molecular weight water-soluble polymers with amphiphilic groups formulated with synergists and solvents. However, many corrosion inhibitors (CIs) are antagonistic to the KHI polymer, severely reducing the KHI performance. It would be preferable and economic if the KHI also could act as a CI. We have explored the use of maleic-based copolymers as KHIs as well as their use as film-forming CIs. KHIs were tested using a natural gas mixture in high pressure rocking cells using the slow constant cooling test method. A terpolymer from reaction of vinyl acetate:maleic anhydride copolymer with cyclohexy lamine and 3,3-di-n-butylaminopropylamine (VA:MA-60% cHex-40% DBAPA), gave excellent performance as a KHI, better than the commercially available poly(N-vinyl caprolactam) (PVCap). CO2 corrosion inhibition was measured by Linear Polarization Resistance (LPR) in a 1 litre CO2 bubble test equipment using C1018 steel coupons. The new terpolymer gave good CO2 corrosion inhibition in 3.6 wt% brine, significantly better than PVCap, but not as good as a commercial imidazoline-based surfactant corrosion inhibitor. The terpolymer also showed good corrosion inhibition efficiency at high salinity conditions, (density 1.12 g/cm3). VA:MA-60% cHex-40% DBAPA shifted the open-circuit potential to more positive values and significantly decreased the corrosion rate.

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