Microscopic experiment on efficient construction of underground gas storages converted from water-invaded gas reservoirs

Based on the microfluidic technology,a microscopic visualization model was used to simulate the gas injection process in the initial construction stage and the bottom water invasion/gas injection process in the cyclical injection-production stage of the underground gas storage(UGS)rebuilt from water-invaded gas reservoirs.Through analysis of the gas-liquid contact stabilization mechanism,flow and occurrence,the optimal control method for lifecycle efficient operation of UGS was explored.The results show that in the initial construction stage of UGS,the action of gravity should be fully utilized by regulating the gas injection rate,so as to ensure the macroscopically stable migration of the gas-liquid contact,and greatly improve the gas sweeping capacity,providing a large pore space for gas storage in the subsequent cyclical injection-production stage.In the cyclical injection-production stage of UGS,a constant gas storage and production rate leads to a low pore space utilization.Gradually increasing the gas storage and production rate,that is,transitioning from small volume to large volume,can continuously break the hydraulic equilibrium of the remaining fluid in the porous media,which then expands the pore space and flow channels.This is conducive to the expansion of UGS capacity and efficiency for purpose of peak shaving and supply guarantee.

Assessment of Fatigue Strength of An Offshore Floating Production and Storage Unit

The procedure of assessment of structural fatigue strength of an offshore floating production and storage and offloading unit (FPSO) in this paper. The emphasis is placed on the long-term prediction of wave induced loading, the refined finite element model for hot spot stress calculation, the combination of stress components, and fatigue damage assessment based on S-N curve.

Investigation of Internal Turret Mooring System for Oil Production Storage Vessels

The internal turret mooring system for oil production storage vessels is a developing type ofoffshore floating production system suitable for deep water and harsh environmental application. In this paper, some achievements in our research work are presented. The description includes: dynamic analysis of mooring system, research on performance of turret assembly, influence of vessel dimensions and hull forms on mooring performance, model tests under combined action of environmental forces in basin, and hull structural strength analysis.

Optimal Design for Main Dimensions of a 75000t Floating Production and Storage Vessel

The basis, process and results of the demonstration of the main dimensions of a 75000t floating production and storage vessel are discussed in this paper. A simple but reliable orthogonal design method is applied in the main dimension optimization. The ideas of gradual approximation and feedback from various aspects are put into effect. During the demonstration, in order to make the model tally with the actual situation, the draft design is closely related to the computational analysis, so that the demonstration model can be verified at any time; the handling of the overall system is closely related to the research of each item, which is beneficial not only to the mastery of various regularities, but also to the balance of decisions. Finally, according to the computational results and the regularities obtained from analysis, the main dimensions are determined.

Research on Innovation of Floating Production Storage and Offloading Unit’s Rent Mode under Low Oil Price

After many years of exploitation,onshore oil and gas resources are about to enter a recession period.Oil and gas will mainly come from oceans in the future.Generally speaking,the exploration and production(E&P)cost of oil from offshore is much higher than that of oil from onshore,so it is more sensitive to oil price.However,in recent years,oil price has been hovering at a low level for a long time,almost close to or even lower than the E&P cost of oil,which directly affects the development of oilfields.Besides the influence of oil price,some oilfields present the characteristics of marginal reserve scale,short peak production period and output rapidly declining.There leads to short economic life period and makes the economic benefit close to or lower than oilfield’s hurdle rate,which increases the difficulty of offshore oilfield development.As an important part of oilfield development,Floating Production Storage and Offloading unit,its investment mode and rent mode directly affect overall oilfield’s rate of return and the economic life.This paper chooses lease mode as the research object based on the analysis of investment mode,and further puts forward rent mode related with oil price through the analysis of traditional rent mode,and illustrates the advantages and disadvantages of various rent modes and their applicability so that the lessor chooses the right mode to achieve Win-Win with Oil Company and promotes the development of oilfields under low oil price.

Studies on Tomato Seedling Quality Indices Under Simulated Shipping and Storage Conditions

Indices of the tomato seedling quality maintenance level after production before field planting were studied through simulated experiments, small—scale operation, indoor analyses and measurements, and field observation. The results showed that under simulated shipping and storage conditions, seedling quality change following different durations (days) of shipping and storage was correlated significantly or even very significantly with certain physiological and morphological indices. With various measured indices following different periods of shipping and storage treatment subjected to multinomial successive regressive correlation analysis, the principal factors influencing seedling quality maintenance level are identified to be chlorophyll content →dry short weight → leaf freshness index in order of their importance. Significance analysis with multinomial fitted equation indicated that correlations between any one of above three factors and the growth index after field planting reached very significant difference level.

Forecast of natural gas supply and demand in China under the background of “Dual Carbon Targets”

As a kind of clean energy which creates little carbon dioxide, natural gas will play a key role in the process of achieving “Peak Carbon Dioxide Emission” and “Carbon Neutrality”. The Long-range Energy Alternatives Planning System(LEAP) model was improved by using new parameters including comprehensive energy efficiency and terminal effective energy consumption. The Back Propagation(BP) Neural Network–LEAP model was proposed to predict key data such as total primary energy consumption, energy mix, carbon emissions from energy consumption, and natural gas consumption in China. Moreover, natural gas production in China was forecasted by the production composition method. Finally, based on the forecast results of natural gas supply and demand, suggestions were put forward on the development of China’s natural gas industry under the background of “Dual Carbon Targets”. The research results indicate that under the background of carbon peak and carbon neutrality, China’s primary energy consumption will peak(59.4×10^(8)tce) around 2035, carbon emissions from energy consumption will peak(103.4×10^(8)t) by 2025, and natural gas consumption will peak(6100×10^(8)m^(3)) around 2040, of which the largest increase will be contributed by the power sector and industrial sector. China’s peak natural gas production is about(2800–3400)×10^(8)m^(3), including(2100–2300)×10^(8)m^(3)conventional gas(including tight gas),(600–1050)×10^(8)m^(3)shale gas, and(150–220)×10^(8)m^(3)coalbed methane. Under the background of carbon peak and carbon neutrality, the natural gas consumption and production of China will further increase, showing a great potential of the natural gas industry.

晃荡力对FPSO货油舱管道的影响分析

为确保管路系统的安全有效运行,着重考虑舱内液体部分装载时晃荡载荷对舱内管路及支架的影响。以某浮式生产储卸油装置(Floating Production Storage and Offloading,FPSO)货油系统工程为例,基于CAESARⅡ软件建立管路模型,并对其进行管路应力分析。计算结果表明:系统在受到晃荡力作用后,管路的一次应力明显增加,且已经超过材料许用值,初始设定的管路壁厚与支架数量不能满足系统的使用要求。可通过增加管路壁厚或支架数量的方式来降低一次应力,解决因应力超标引起管路损坏、系统失效的危害。研究成果可为FPSO货油舱管道分析提供一定指导。

Risk Management of Key Issues of FPSO

Risk analysis of key systems have become a growing topic late of because of the development of offshore structures. Equipment failures of offioading system and fire accidents were analyzed based on the floating production, storage and offioading （FPSO） features. Fault tree analysis （FTA）, and failure modes and effects analysis （FMEA） methods were examined based on information already researched on modules of relex reliability studio （RRS）. Equipment failures were also analyzed qualitatively by establishing a fault tree and Boolean structure function based on the shortage of failure cases, statistical data, and risk control measures examined. Failure modes of fire accident were classified according to the different areas of fire occurrences during the FMEA process, using risk priority number （RPN） methods to evaluate their severity rank. The qualitative analysis of FTA gave the basic insight of forming the failure modes of FPSO offioading, and the fire FMEA gave the priorities and suggested processes. The research has practical importance for the security analysis problems of FPSO.

Numerical analysis of coupled sloshing and motion of a cylindrical FPSO in regular waves

In this paper,the coupled sloshing and motion characteristics of a cylindrical floating production storage offloading(CFPSO)are numerically investigated by means of computational fluid dynamics(CFD)tool.The simulations are performed using an in-house CFD solver naoe-FOAM-SJTU which is developed based on OpenFOAM.The active wave generating-absorbing boundary condition(GABC)is utilized for wave generation and absorption.The stabilized k-omega SST turbulence model are used to avoid excessive eddy viscosity near the free surface.CFPSO with and without partially filled liquid tanks in regular waves with different wave periods are simulated and vertical planar motions such as surge,heave and pitch response amplitude operators(RAOs)are compared.Forces due to liquid sloshing and wave loads are extracted and analyzed.The free surface motions inside liquid tanks in one wave period presented to explain the motion characteristics.

缆绳破断条件下FPSO码头系泊系统安全性分析

为研究浮式生产储卸油船(Floating Production Storage and Offloading, FPSO)在码头舾装期间系泊系统的安全性,对某30万吨级FPSO的码头系泊系统在台风条件下单系泊缆破断后的安全性进行分析。基于模拟结果,分别计算了受力最大和受力第二大的缆绳破断后,码头系泊系统中剩余缆绳的张力和安全系数。结果表明:缆绳破断后,剩余缆绳的安全系数总体是减小的,但有部分剩余缆绳的最小安全系数有明显的上升;在系泊系统完整和破断条件下,安全系数最小的缆绳均为同一组缆绳;在一根缆绳破断后,码头系泊系统仍具有足够安全性。研究成果可为FPSO码头系泊系统安全评估提供一定参考。

Numerical simulation and analysis of periodically oscillating pressure characteristics of inviscid flow in a rolling pipe

Floating liquefied natural gas （LNG） plants are gaining increasing attention in offshc,re energy exploitation. The effects of the periodically osciUatory motion on the fluid flow in all processes on the oil＂shore plant are very complicated and require detailed thermodynamic and hydrodynamic analyses. In this paper, numerical simula- tions are conducted by computational fluid dynamics （CFD） code combined with user defined function （UDF） in order to understand the periodically oscillating pressure characteristics of inviscid flow in the rolling pipe. The computational model of the circular pipe flow is established with the excitated rolling motion, at the excitated frequencies of 1-4rad/s, and the excitated amplitudes of 3^-15~, respectively. The influences of flow velocities and excitated conditions on pressure characteristics, including mean pressure, frequency and amplitude are systematically investigalted. It is found that the pressure fluctuation of the inviscid flow remains almost constant at different flow velocities. The amplitude of the pressure fluctuation increases with the increasing of the excitated amplitude, and decreases with the increasing of the excitated frequency. It is also found that the period of the pressure fluctuation varies with the excitated frequency. Furthermore, theoretical analyses of the flow in the rolling circular pipe are conducted and the results are found in qualitative agreement with the numerical simulations.