Heat Transfer Analysis for Gas-to-Liquids Transportation Through Trans Alaska Pipeline

Abstract

Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.     

Analysis of Pressure Loss and Heat Transfer of Non-Newtonian Fluid Flow through Trans-Alaska Pipeline System

In this study, theoretical analyses have been performed to determine the feasibility of transporting gas-to-liquid (GTL) products through the Trans-Alaska Pipeline System (TAPS) using a non-Newtonian fluid flow approach. Due to heat loss, the fluid temperature decreases in the direction of flow, and this affects the fluid properties, which in turn influence the convection coefficient and pumping power requirements. This article presents fluid temperature and heat loss along the pipeline at different locations. Furthermore, this study includes calculations on the power required to pump GTL and crude oil/GTL mix. Parametric studies had been performed varying two parameters: wind velocity, to vary convection over the pipeline, and snow depth. Ambient air velocities of 0.45 m/s (1 mph), 4.47 m/s (10 mph), and 8.94 m/s (20 mph) have been considered. Snow depths of 0 m (0 ft), 0.305 m (1 ft), and 0.61 m (2 ft) have also been taken into account. These results show that the pumping power and heat loss for GTL and commingled mixtures are less than that predicted by Nerella's (2002) Newtonian flow calculations.     

Analysis of Pressure Loss and Heat Transfer of Non-Newtonian Fluid Flow through Trans-Alaska Pipeline System

Abstract

In this study, theoretical analyses have been performed to determine the feasibility of transporting gas-to-liquid (GTL) products through the Trans-Alaska Pipeline System (TAPS) using a non-Newtonian fluid flow approach. Due to heat loss, the fluid temperature decreases in the direction of flow, and this affects the fluid properties, which in turn influence the convection coefficient and pumping power requirements. This article presents fluid temperature and heat loss along the pipeline at different locations. Furthermore, this study includes calculations on the power required to pump GTL and crude oil/GTL mix. Parametric studies had been performed varying two parameters: wind velocity, to vary convection over the pipeline, and snow depth. Ambient air velocities of 0.45 m/s (1 mph), 4.47 m/s (10 mph), and 8.94 m/s (20 mph) have been considered. Snow depths of 0 m (0 ft), 0.305 m (1 ft), and 0.61 m (2 ft) have also been taken into account. These results show that the pumping power and heat loss for GTL and commingled mixtures are less than that predicted by Nerella's (2002) Newtonian flow calculations.     

塔河油田超深自喷井流态特征分析

针对塔河油田油藏埋藏深、原油粘度高、井筒热损失大导致自喷困难的实际问题，根据热量传热原理和两相流动理论，建立了自喷井中产出液沿井筒流动与传热的热力学模型。运用该模型计算了塔河油田5口稠油井产出液沿井筒的温度和压力分布。计算结果表明。随着产出液沿井筒的举升。压力逐渐减小，温度不断下降。当温度下降到一定数值时。原油粘度明显增大，即对应原油的拐点温度出现。因此，可以根据流态特征来估计该原油的拐点温度，为选择合适的降粘方法和降粘深度提供了技术指导。     

潜油电泵系统发热对稠油粘度的影响

建立电潜泵油井井筒温度计算模型,根据井筒温度随井深的分布规律,分析井筒中原油物性的变化。探讨无任何改善稠油粘度的措施下,仅利用潜油电泵油井生产过程中产生的热量来改善井筒中流体的物性,降低稠油油藏开采成本。通过油井井筒温度分布的敏感性分析,指出电机功率、下泵深度、日产液量是主要影响因素,应合理取值才能得到最佳开采效果。     

中高含水期水力活塞泵采油水基动力液可行性研究

我国使用水力活塞泵采油的油田多数已进入中高含水期，用加高压、升温原油作动力液，采出大量的高含水原油，非常不经济；其次，由于设备长期在高压、高温下运行，已达到疲劳极限，安全性变差，发生事故的可能性增加。文中研究了国内外水力活塞泵采油使用水基动力液的情况，从水基动力液的优点及地面、井下配套工艺、经济效益评估等方面对水基动力液采油进行了可行性研究。     

中高含水期水力活塞泵采油水基动力液可行性研究

我国使用水力活塞泵采油的油田多数已进入中高含水期,用加高压、升温原油作动力液,采出大量的高含水原油,非常不经济;其次,由于设备长期在高压、高温下运行,已达到疲劳极限,安全性变差,发生事故的可能性增加。文中研究了国内外水力活塞泵采油使用水基动力液的情况,从水基动力液的优点及地面、井下配套工艺、经济效益评估等方面对水基动力液采油进行了可行性研究。     

塔河油田超深井井筒掺稀降粘技术研究

基于热量传递原理和两相流动理论,建立了井筒掺稀油降粘工艺中产液沿井筒流动与传热的热力学模型。计算了产液沿井筒的温度分布和压力分布,同时进行了不同掺稀条件下降粘的室内实验。运用该模型结合实验结果对塔河油田稠油井掺稀降粘效果进行了计算,分析了不同工艺参数对掺稀降粘效果的影响。结果表明,井筒掺稀油降粘工艺适合于含水率低于20%的油井,开式掺稀油反循环比开式掺稀油正循环生产更有利于提高降粘效果,塔河油田井筒掺稀降粘合理的掺稀比率为1:2至1:1。     

高凝高粘原油井筒粘度计算模型

大港油田高凝高粘原油在不同含水、不同温度下的粘度测试结果表明,在不同含水条件下,随温度的升高,高凝高粘原油的粘度都有不同程度的降低,表现出了很明显的粘温特性;在同一温度下,原油的粘度随着含水率的变化是一个先增加后减小的过程,峰值含水区间为20%～40%;对实测原油粘度数据进行回归得到粘度计算经验模型。根据幂律流体流动规律分别建立了有杆抽油井上冲程和下冲程过程中井筒和杆管环形管道内流体流动的速度场模型和相对应的流体粘度计算模型。计算结果显示,所建立的井筒粘度计算模型与实测结果误差较小,大大优于常规油井井筒粘度计算模型,能够满足工程需要。     

海上射流泵井井筒温度场模型

稠油的开采方式主要是降低原油黏度,增加其流动性。由于原油的黏度对于温度极其敏感,热采开采方式备受关注。以渤海油田A区的实验井为例,介绍了射流泵井以多元热流体为动力液在同心管井筒的传热特点,研究了热流体在井筒各部分的传热过程,建立了综合传热系数的计算方法以及井筒温度场模型,根据相应的温度场求解流程,编制软件,并以实际射流泵生产井为例进行计算。实际测量结果与软件计算结果存在8.87%的误差,可以为后续海上稠油油田射流泵井工况诊断和参数优化提供保障。     

春风油田浅层超稠油HDNS技术研究

针对准噶尔盆地西缘春风油田浅层超稠油油层薄、地层热损失严重的难题,提出了水平井、降黏剂、氮气、蒸汽强化热采方式（HDNS）。氮气降低岩石导热系数,降低薄层稠油油藏沿上部盖层的热量损失。地层内氮气向上超覆,起到地层保温作用。降黏剂有效降低原油黏度,大幅降低了地下原油屈服值和原油能够流动的临界温度,延长了生产周期,增加了周期产油量。配套了注采一体化管柱和水平井大斜度泵工艺。春风油田应用HDNS技术已经建成产能61．7×10^4t／a,采油速度大于3％。     

原油储存温度的优化

分别研究了原油储存温度对原油输送功率,罐区加热、维温、散热负荷,以及蒸馏装置冷、热公用工程消耗的影响;结合环境温度变化,建立了相关的能耗和能耗费用计算方程,并以此为基础提出了以总能耗或总能耗费用最小为目标函数的优化原油储存温度计算方法.实例应用表明该方法应用于实际操作,可较大幅度地降低原油罐区和蒸馏装置的相关能耗.     

杆式泵泵筒内流体流动规律的数值模拟

针对杆式泵泵简内的流体流动问题,采用湍流模型的K-ε两方程模型和有限元方法,对在一个抽油循环中阀与活塞在几个特定的位置的流体流动进行了建模与计算,具体分析了处于阀道内和同心环状空间中的原油在上下冲程的运动规律。通过计算知,泵筒内流体的最大速度与入口端的初始流连基本满足线性关系,而最大流压与入口端的初始流速不满足线性关系,直径大的泵,其流压整体上要比直径小的泵要小,分析结果可为杆式泵的内部结构设计和几何参数的确定提供一定的参考依据。     

稠油集输工艺设计

在稠油集输工艺设计参数的选取中，当稠油乳状液为牛顿流体时，可按达西公式计算水力损失，其粘度可由粘度比法求出；非牛顿流体乳状液紊流态水力计算，应通过实验确定摩擦系数，再按过西公式计算压降；对纯稠油、含地层水稠油、稠稀混合油和掺破乳剂溶液稠油的停输启动压力．采用剪切力公式推算。在稠油的油气分离工艺设计中，对计量分离器，应尽量简化分离器的结构；对生产分离器．可适当增加分离元件，使油气分高效果相对提高；终端油气分离器或气体除油器，应设计较完善的油气分离结构；此外，应慎用丝网除雾器。在稠油脱水工艺设计中，应注意脱水措施及脱水方法的选择。在稠油集输中应多采用低级数、低转数的容积式转子泵。但在选用泵型时，应根据设计工作条件对泵的流量、扬程、轴功率及高效率区间进行校核。     

Wax Deposition in Flow Lines Under Dynamic Conditions

The wax deposition in the tubing, pipeline, and surface flow line is the major problem in the oil fields. It generates additional pressure drop and causes fauling and ultimately increases the operating cost during production, transportation, and handling of waxy crude oil. In this work, attempts were made to study the wax deposition in the flow lines due to Indian crude oil under dynamic condition. The experimental work was carried out for neat crude oil and pour point depressants treated crude oil at different ambient/surface temperature and pumping/reservoir temperature. It was observed that temperature has significant effect on the wax deposition of the crude oils. From these studies, ideal temperature of crude oil to pump in the pipeline or flow line was determined. The present investigations also furnishes that the selected pour point depressant in this work decreases the wax deposition significantly and may be used for controlling the wax deposition problems in case of Indian crude oil.     

东辛油田稠油举升井筒保温对策研究及现场试验

稠油在井筒举升过程中,由于热损失造成温度下降,致使其黏度迅速增大,举升负荷较大。因此,研究稠油举升中的井筒保温对策具有现实意义。基于传热学的基本原理,采用计算稠油井井筒温度场的Hansan模型,以东辛油田Y12X2X3井为例对井筒温度分布进行了计算分析,并对影响稠油井井筒温度的油管类型、油管长度和产液量等3项参数进行了优化,提出了采用长度1 000 m的D级隔热油管和普通油管组合、产液量由11 m3/d提高到20 m3/d的井筒保温措施。现场试验显示,井口温度由调整前的20.5℃升高至41.5℃,井深1 000 m以浅井段原油黏度大幅度降低,原油流动性增强,有杆泵充满程度增加,泵效提高了47%。研究结果表明,采用稠油井筒温度场计算模型能准确描述井筒温度的分布情况,并能有针对性地制订稠油井井筒保温措施。      

The Performance of Toluene and Naphtha as Viscosity and Drag Reducing Solvents for the Pipeline Transportation of Heavy Crude Oil

Heavy crude oil shows high viscosity combined with low mobility, which affects the efficient transportation through pipelines. Drag has long been identified as the main reason for the loss of energy in pipeline fluid transmission and other similar transportation channels. The main contributor to this drag is the viscosity as well as friction against pipe walls, which will result in more pumping power consumption. Various methods such as heating, upgrading, dilution, core annular flow, and emulsification in water have been used for their transportation. The influence of toluene and naphtha as a viscosity and drag reducing solvent on flow of Iraqi crude oil in pipelines was investigated in the present work. The effect of additive type, concentration, pipe diameter, solution flow rate, and heating on the percentage of drag reduction (%Dr) and percentage flow increase (%FI) were the variables of study. The maximum drag reduction was observed to be 40.48% and 34.32% using heavy oil flowing in pipeline diameter of 0.0508 m I.D. at 27°C containing 10 wt% naphtha and toluene, respectively. Also, the dimensional analysis is used for grouping the significant quantities into dimension less group to reduce the number of variables.     

喷射泵采稠油数值模拟

应用喷射泵理论和高粘流体下的喷射泵的试验数据,分析了粘度对喷射泵特性的影响,用函数拟合了影响喷射泵特性的参数——喷嘴摩擦损失系数K1’和喉管及扩散管摩擦损失系数K34,编制了喷射泵采稠油的计算机数值模拟程序,为优化设计和优化管理喷射泵热采稠油井打下了基础。     

EVALUATION OF THE MODES OF TRANSPORTING GAS-TO-LIQUID (GTL) PRODUCTS THROUGH THE TRANS ALASKA PIPELINE SYSTEM (TAPS)

ABSTRACT

As part of a project on studying the transportation of gas-to-liquids (GTL) through the Trans Alaska Pipeline System (TAPS), two GTL transportation modes are evaluated: (i) as single slugs (batches) and (ii) commingled (mixed) with the Alaskan North Slope Crude (ANSC) oil. The pertinent energy equations are solved for both the batch and commingled flow modes. The solutions of these equations are analytically presented for determining among other parameters, the pressure gradient and the slug length required for batching. A comparison of the pressure gradient calculations is presented for the batching and the commingled flow cases.     

液力驱动抽油系统动力液压力计算

液力驱动抽油系统采用高压动力液驱动井下液动机,动力液一般采用水,液动机带动井下抽油泵往复运动采油,抽油泵与常规杆式抽油泵相同,液力驱动抽油系统没有抽油杆,避免了杆管偏磨问题。分析了一种液力驱动抽油泵采油装置井下部分的结构和工作原理以及液动机和抽油泵的受力情况,利用受力平衡原理,给出了液动机上行和下行时的动力液压力计算公式,得到了抽油泵上、下冲程时地面动力液的工作压力范围。