Research Progress on Calculation and Control of Unaccounted for Gas of Natural Gas Pipeline Network

At present, volume measurement is still used in transfer measurement of natural gas in China, so the calculation and management of Unaccounted for Gas are based on volume measurement. With the change of natural gas measurement method from volume measurement to energy measurement, the calculation and management of Unaccounted for Gas based on energy measurement will be paid more and more attention. This paper investigates the calculation methods and management measures of Unaccounted for Gas based on volume measurement in China and Unaccounted for Gas based on energy measurement in other countries, and compares the research progress. The results show that: the general principles of Unaccounted for Gas calculation in China and other countries are basically the same, but the calculation formulas are not completely the same. All countries consider the input gas, output gas, line pack variation and self-consumption gas. On this basis, Italy considers the known leakage, and Britain considers the known leakage and the daily calorific value shrinkage caused by its settlement rules. In order to reduce Unaccounted for Gas, the UK regularly verifies meter, carries out the research on Unaccounted for Gas baseline, and actively participates in the global Unaccounted for Gas benchmarking. Australia replaces the old main line and reduces the operation pressure of pipeline, which significantly reduces Unaccounted for Gas. The calculation methods and control measures of Unaccounted for Gas based on energy measurement in Italy, Britain and Australia can be used for reference in China.

Use of Horizontal Drift-Flux Models For Simulating Wellbore Flow in SAGD Operations

The paper examines new horizontal drift-flux correlations for their ability to accurately model phase flow rates and pressure drops in horizontal and undulating wells that are part of a Steam-Assisted Gravity Drainage (SAGD) field operation. Pressure profiles within each well correlate to the overall performance of the pair. SAGD is a low-pressure process that is sensitive to reservoir heterogeneity and other factors, hence accurate simulation of in situ wellbore pressures is critical for both mitigating uneven steam chamber evolution and optimizing wellbore design and operation. Recently published horizontal drift-flux correlations have been implemented in a commercial thermal reservoir simulator with a multi-segment well model. Valid for horizontally drilled wells with undulations, they complement previously reported drift-flux models developed for vertical and inclined wells down to approximately 5 degrees from horizontal. The formulation of these correlations has a high degree of nonlinearity. These models are tested in simulations of SAGD field operations. First, an overview of drift-flux models is discussed. This differentiates those based on vertical flow with gravity segregation to those that model horizontal flow with stratified and slug flow regimes. Second, the most recent and significant drift-flux correlation by Bailey et al. (2018, and hereafter referred to as Bailey-Tang-Stone) was robustly designed to be used in the well model of a reservoir simulator, can handle all inclination angles and was optimized to experimental data from the largest available databases to date. This and earlier drift-flux models are reviewed as to their strengths and weaknesses. Third, governing equations and implementation details are given of the Bailey-Tang-Stone model. Fourth, six case studies are presented that illustrate homogeneous and drift-flux flow model differences for various well scenarios.

Multi-Objective Optimization of CO2 Sequestration in Heterogeneous Saline Aquifers under Geological Uncertainty

This paper presents a Pareto-based multi-objective optimization for operating CO2 sequestration with a multi-well system under geological uncertainty; the optimal well allocation, i.e., the optimal allocation of CO2 rates at injection wells, is obtained when there is minimum operation pressure as well as maximum sequestration efficiency. The distance-based generalized sensitivity analysis evaluates the influence of geological uncertainty on the amount of CO2 sequestration through four injection wells at 3D heterogeneous saline aquifers. The spatial properties significantly influencing the trapping volume, in descending order of influence, are mean sandstone porosity, mean sandstone permeability, shale volume ratio, and the Dykstra–Parsons coefficient of permeability. This confirms the importance of storable capacity and heterogeneity in quantitatively analyzing the trapping mechanisms. Multi-objective optimization involves the use of two aquifer models relevant to heterogeneity; one is highly heterogeneous and the other is less so. The optimal well allocations converge to non-dominated solutions and result in a large injection through one specific well, which generates the wide spread of a highly mobile CO2 plume. As the aquifer becomes heterogeneous with a large shale volume and a high Dykstra–Parsons coefficient, the trapping performances of the combined structural and residual sequestration plateau relatively early. The results discuss the effects of spatial heterogeneity on achieving CO2 geological storage, and they provide an operation strategy including multi-objective optimization.

Construction of Loose Positively Charged NF Membrane by Layer-by-Layer Grafting of Polyphenol and Polyethyleneimine on the PES/Fe Substrate for Dye/Salt Separation

The effective separation of dyes and inorganic salts is highly desirable for recycling inorganic salts and water resource in printing and dyeing wastewater treatment. In this work, tannic acid (TA) and polyethyleneimine (PEI) were grafted on the PES/Fe ultrafiltration membrane via the coordination assembly and Michael addition strategy to fabricated a loose nanofiltration membrane (LNM). The effect of PEI concentration on membrane morphologies and properties was systematically investigated. The membrane surface becomes more hydrophilic and transforms into positive charge after the PEI grafting. The optimized PES/Fe-TA-PEI membrane possesses high pure water flux (124.6 L·m−2·h−1) and excellent dye rejections (98.5%, 99.8%, 98.4%, and 86.4% for Congo red, Eriochrome black T, Alcian blue 8GX, and Bromophenol blue, respectively) under 2 bar operation pressure. Meanwhile, the LNM showed a high Alcian blue 8GX rejection (>98.4%) and low NaCl rejection (<5.3%) for the dye/salt mixed solutions separation. Moreover, the PES/Fe-TA-PEI LNM exhibited good antifouling performance and long-term performance stability. These results reveal that such LNM shows great potential for effective fractionation of dyes and salts and recycling of textile wastewater.

Evaluation of the Structural Integrity of Bell-Spigot Joints in Steel Gas Pipelines

The most common joining method in steel gas pipelines is welding; however, this method involves time-consuming, expensive manufacturing and assembly processes to ensure quality in operation. Bell-Spigot joints, which work by mechanical interference, have started to be used as an alternative joining method in steel pipes. Its use has increased due to its reduced assembly time and less post-assembly inspection requirements. In this paper, the structural performance of Bell-Spigot joints in 16-inch steel pipe API 5L X70 with Fusion Bonded Epoxy (FBE) coating for Natural Gas transmission pipeline are evaluated experimentally and by modeling. Test pieces were taken from the gas pipeline after 3 years of operation. Then, tensile pull-out and bending with hydrostatic pressure tests were performed to replicate operating conditions. Deformations, displacements, and the potential presence of leaks were monitored. Experimental results were compared with a Finite Element Method model. Finally, an analytical model for the calculation of stresses and strains in the joint system's components was developed. It was determined that the tightness of the joint depends mainly on the radial interference and the interference length. A higher safety factor can be obtained at the bell-spigot joint than the base pipeline by optimizing selection of joint design variables and the service loading conditions. If the interference pressure is lower than half of the operation pressure, the joint's mechanical strength will be higher or equal that the base pipe.

Study of livestock biogas upgrading using a pilot-scale photocatalytic desulphurizer followed by a hollow fibre carbon dioxide adsorption module

The objective of this project is to integrate a domestic photocatalytic desulphurization facility with a biogas upgrading module and try to develop a system for biogas desulphurization and upgrading under ambient conditions. Four photocatalytic desulphurization reactors (PDRs) and one activated carbon reactor (ACR) were applied for biogas desulphurization and filtration under ambient conditions. Moreover, a hollow fibre carbon dioxide (CO2) adsorption module was applied for biogas upgrading. The operation pressure of the PDR and ACR was under ambient pressure. Results showed that hydrogen sulphide removal efficiency of the photocatalytic desulphurizer was about 0.99–1.00 (v/v) under the inlet biogas flow less than 5 litres/min and the concentration of inlet hydrogen sulphide was lower than 5600 mg/m3. For desulphurized biogas upgrading, the removal efficiency of CO2 was higher than 0.90 (v/v) under the outlet biogas flow was 1 litre/min (i.e. inlet biogas flow was about 2 litres/min). However, the ratio of methane in the upgrading biogas was lower than 0.90 (v/v). Thus, nitrogen gas removal cartridges will be integrated with the biogas upgrading module to promote methane concentration in the upgraded biogas.

Fatigue Evaluation of API 12F Shop-Welded Tanks With a New Roof-to-Shell Junction Detail

The American Petroleum Institute (API) provides a series of standards and specifications on storage tanks, in which the API 12F specification provides 12 tank designs that can be fabricated in the shop and transported to the field. The nominal capacity of the 12 API 12F tank designs ranges from 90 bbl (14.3 m3) to 1000 bbl (158.99 m3). The minimum required thickness and operational pressure levels that each tank case can sustain are given in Table 1 of the current 13th edition of API 12F (API, 2019, “API 12F Specification for Shop-Welded Tanks for Storage of Production Liquids,” 13th ed., API Publishing Services, Washington, DC, Standard No. API 12F). The objective of this study is to estimate the fatigue life of API 12F tanks under normal operation pressure cycles following the procedure presented in ASME VIII-2. The stored liquid product specific gravity is assumed to be 1.2 when the liquid height is half of the tank height, while the specific gravity is assumed to be 0.7 when the stored liquid height is 18 in. (460 mm). Meanwhile, a new roof–shell attachment detail is proposed in this study, the new rectangular cleanout junction detail presented in the 13th edition of API 12F is modeled, and various component thickness combinations are considered to investigate the effect of component thickness on fatigue life. The roof–shell joint (top junction) and shell–bottom plate (bottom junction) are studied by axisymmetric models under axisymmetric idealization as they are away from the cleanout junction, while the cleanout junction is studied by applying a submodeling technique. Stress classification is performed at each location of interest to obtain the stress components to calculate the stress range within each loading cycle that is needed to perform fatigue evaluation. The results and discussion about fatigue evaluation of API 12F tanks are presented in this report.

Analysis of Compressed Air Energy Conversion Processes in a Rotary Piston Pneumatic Engine

This article describes a rotary piston pneumatic engine with a gas exchange system design that minimizes the value of the relative dead volume, as well as ensures the minimum dimensions and weight of the engine. The main purpose of the study is to evaluate the conversion efficiency of compressed air energy in the working cylinder of the rotary piston pneumatic engines using the exergy method of thermodynamic analysis. To achieve the set goal of the study, physical modeling of various operation modes has been performed. The most significant result is that, based on the physical and mathematical modeling, a thermodynamic assessment of the efficiency of the compressed air energy conversion has been performed. The significance of the results obtained lies in the fact that the effect of the main operational parameters of the pneumatic engine on the efficiency of energy conversion is established. The basic equations of the exergy method of the thermodynamic analysis are presented. The results of physical and mathematical modeling of various operation modes are presented. The main reasons for the decrease in the energy conversion efficiency at low and rated loads are emphasized. The amount of exergy supplied with the air flow was established, which, depending on the operation mode, amounted to 2.2…11.4 kW. According to the presented results, the most optimal speed range, based on the achievement of the maximum values of the specific efficient work and exergy efficiency, is 55…70% of the nominal value. It was found that an increase in the operation pressure decreases slightly the exergy efficiency. A twofold increase in the operation pressure of the pneumatic engine increases the efficient power by 46 % at a simultaneous decrease in the exergy efficiency by 8.2 %.