油田地下蒸汽管道系统蒸汽干度计算方法

蒸汽吞吐是稠油开采的主导工艺技术,蒸汽干度是注汽工艺的主要参数,提高井底蒸汽干度是提高热采经济效益的核心问题.为了实现注汽锅炉蒸汽干度的高质量控制,提出一种蒸汽干度计算方法,此方法通过首先计算沿程摩擦阻力,然后求出该点的蒸汽温度,进而求出管段的热损失,最后可求出管道内任意处的蒸汽干度.该方案研究了输汽管道系统蒸汽干度的变化情况,为热采输汽系统工艺设计提供参考.     

SAGD系统输送过热蒸汽热力适应性分析

根据SAGD原理,注入蒸汽干度的高低直接影响开发效果和经济效益,因此将过热蒸汽应用于SAGD开发会带来显著经济效益。与高干度湿蒸汽相比,过热蒸汽携带热焓多、温度高,对地面管线、井筒管柱热应力、蒸汽腔发育等方面产生的影响也不同。通过输汽管线应力分析和保温设计校核,发现现有的地面注汽管线输送过热蒸汽后,虽然管线热损失增大了,但仍在国标许可范围内,因此无需更换保温层厚度。由于注过热蒸汽流动阻力大,部分工况下需更换管线,增大管径。开展过热蒸汽井筒流动传热规律研究及注入参数优化设计,建立井筒内过热蒸汽流动传热模型并模拟,得到井筒压力、温度、热损失分布规律,并对确保井底过热工况下井口所需的过热蒸汽过热度、压力等参数进行了优化计算,给出18组优化注汽参数组合,用以指导SAGD高效注汽生产。     

地面管线蒸汽干度计算模型及影响因素分析

为实现稠油热采地面管线蒸汽干度准确预测,分析其对采油效率的影响,建立了湿蒸汽在地面管线内流动的热损失和压降耦合模型,采用微元法获得地面管线蒸汽干度拟合方程,研究了不同因素对水平管线沿程蒸汽干度的影响,结果表明:湿蒸汽计算值与拟合值相对误差均在10~(-6)～10~(-5)数量级,线性拟合方程可进行地面管线任意截面蒸汽干度预测;降低注汽锅炉出口温度和压力,增加注汽流量,提高初始蒸汽干度,可有效提高地面管线末端注汽井口的蒸汽干度。为稠油热采地面管线注汽系统的评价与优化提供理论参考。     

稠油地面蒸汽管线热力参数影响及保温厚度优化

提高蒸汽注汽品质和优化保温层厚度是改善地面蒸汽管线热力输运、实现稠油高效开采的关键。建立了油田地面蒸汽管线热力参数计算模型和保温层厚度经济性分析模型,基于分段微元方法求解沿程蒸汽干度、热损等特性参数,分析了锅炉出口蒸汽参数和注汽流量的影响规律,并结合经济厚度法的计算原理优化了保温层厚度。结果表明：提高锅炉出口蒸汽温度和压力,沿程蒸汽干度降低速度变快,沿程热损增加变快,与锅炉出口蒸汽温度313 oC,压力10.2 MPa相比,其热损最大增加11.15%;增加注汽流量,蒸汽干度提升且随管线沿程降幅缩小,等梯度注汽流量差下,高注汽流量时蒸汽干度降幅较小,其降幅为3.58%;经济厚度为0.33m时,其热损费用同比原有厚度可降低68.22%。     

提高注汽锅炉排量研究

注汽锅炉是稠油热注开采的主要设备,也是热注工艺过程的能耗大户。基于某采油厂燃油注汽锅炉将燃料改为天然气,锅炉的运行蒸汽排量均较低,性能得不到充分发挥。为了提高注汽锅炉的效率,在当前运行基础上将排量提高10%,同时应用注汽锅炉蒸汽干度在线监测装置对锅炉的蒸汽干度等运行参数进行监控,提高锅炉效率,保证锅炉安全运行,降低锅炉运行成本。     

稠油蒸汽吞吐生产过程节点能耗分析及对策

通过对稠油蒸汽吞吐生产过程中热能耗分类分析,找出能耗损失的敏感性因素是锅炉本体损失、注汽管网损失、注汽井筒损失,注入地层热能有效利用率仅为48%,吞吐生产油井产出时热能有效利用率只有43.5%。结合分析结果提出了提高热效率的七项措施。     

内连接隔热油管隔热性能分析及应用

以内连接隔热油管为研究对象,建立一维传热和径向传热的数学公式推导,计算出现场注蒸汽过程中使用的E级隔热油管和接箍的综合视导热系数;通过Wellflo软件建立蒸汽吞吐模型,输入综合视导热系数0.173 W/(m·℃),计算出井筒的温度压力分布,结合现场注汽中的实际测试数据,将软件计算数据与实测数据进行拟合度,拟合度高达0.994 6。论证了试验得出的注汽中隔热油管和接箍的综合视导热系数0.173 W/(m·℃)符合现场实际,为日后的渤海油田规模化提供了现场工艺数据支撑。     

稠油井自动蒸汽伴热工艺的应用及效果

结合自动控制技术应用经验，自行研究和设计了自动蒸汽伴热工艺。通过伴热工艺的应用试验，井筒温降测试，伴热用汽计量等工作结果表明，油井成功实现了自动蒸汽伴热，保证了稠油井正常生产。     

水平井双管注汽配合分段完井技术研究与应用

随着水平井技术开发超稠油油藏实施规模的不断扩大,水平井水平段动用不均的矛盾逐渐加剧。分析认为,水平井完井工艺和注汽管柱工艺不完善,是造成水平段注汽不均、从而导致动用不均的两个主要原因。根据水平井水平段储层沿程物性差异分布特点,在水平井完井时采用分段完井技术,在水平段中间物性差井段下入封隔器,将水平段筛管外与油层裸眼之间分隔成两段独立的井段腔室,并在紧挨封隔器位置下入扶正器,保证筛管在裸眼井段居中下入。注蒸汽时,依据井温监测资料判断水平段动用状况,实施双管注汽工艺技术,采用内、外管双注汽管柱注汽方式,分别对水平井水平段跟端和指端部位同时注汽,井口配套工具采用双四通、双悬挂器,同时应用等干度分配器,实现双管柱内的蒸汽流量灵活控制及等干度分配,实现水平段前后井段同时均匀注汽,调整水平段动用程度。     

油田注汽锅炉过热爆管故障智能诊断方法

本文分析了国内注汽锅炉故障诊断方法,在利用小波变换分析注汽锅炉蒸汽干度的基础上,将径向基神经网络专家系统应用于注汽锅炉过热爆管的故障诊断。文章介绍了诊断系统的结构、学习算法和诊断步骤,提出了一种油田注汽锅炉的智能故障诊断方法。仿真结果证明了该方法的准确率与可靠性。     

A novel analytical transient heat-conduction time function for heat transfer in steam injection wells considering the wellbore heat capacity

Steam injection technique is one of the most important methods for enhancing the heavy oil production. Evaluating the reliability of steam injection projects requires the investigation of the heat transfer in the wellbore and the surrounding formation. In this study, a new formation heat-transfer model taking into account the wellbore heat capacity was developed and a novel analytical transient heat-conduction time function was presented. Comparison of the formerly used transient heat-conduction time functions with the novel analytical transient heat-conduction time function was made. The result indicated that the wellbore heat capacity has a significant influence on the transient heat-conduction time function, especially for cases of short time injection. To investigate the effect of wellbore heat capacity on the heat transfer in steam injection wells, a comprehensive wellbore/formation model incorporating the novel analytical transient heat-conduction time function was also established. Based on this model, the wellbore/formation interface temperature and the wellbore heat losses were computed by using various transient heat-conduction time functions. The comparisons showed that the formerly used transient heat-conduction time functions would lead to inadequate estimation of the wellbore/formation interface temperature and the wellbore heat losses. High accuracy and excellent applicability of the wellbore/formation model were demonstrated when performances of the proposed model were compared with the measured field data from the steam injection well.     

Simulation of Steam Injection Process for Horizontal Well with Heavy Oil Recovery

Horizontal well technology is widely used in the production of heavy oil. Steady-state model is used as main research method and assume constant wet steam parameters in wellbore, ignoring the impact of heat and mass transfers of steam from wellbore to the reservoir. Numerical calculation is used to analyze steam-water-oil three-phase on flow and heat transfer rule in reservoir and wellbore in startup phase. The influence rule on diffusion process of vapor and water hindered by oil stockpile in wellbore was analyzed, as well as vapor and water parameters change rule along the well. Result indicated that wet steam moving forward was hindered by oil stockpile in wellbore, which lead reservoir suction steam to be not uniform; dryness and temperature of steam gradually reduce, resulting in high temperature at the heel and low temperature at the toe of reservoir; reservoir suction steam effect was improved and reservoir heated range was expanded gradually with the increasing of steam injection volume and dryness; variation of reservoir porosity and permeability have a similar effect on reservoir suction steam, comparing with steam injection volume and dryness. When porosity and permeability were enlarged, reservoir suction steam effect and reservoir heated range would become better.     

Advanced mathematical model for reservoir heat efficiency with liquid in steam-injection wellbore

The accurate determination of reservoir heat efficiency of steam injection in heavy oil reservoirs is very important for heating radius calculation and production dynamic prediction. In conventional calculation methods of reservoir heat efficiency, the steam-injection wellbore is assumed as taking steam over the entire height. In fact, a liquid level in steam-injection wellbore is a very significant observation with respect to the steam override. Aiming at the actual situation that the steam-injection wellbore always has a liquid level, combined with the formation temperature distribution, the new mathematical model for reservoir heat efficiency with the consideration of liquid in steam-injection wellbore was established based on the Van Lookeren steam override theory and the energy conservation principle. The established mathematical model was used to calculate and analyze the reservoir heat efficiency of steam injection in heavy oil reservoirs. The results show that because the new mathematical model considers the liquid in the steam-injection wellbore, the predicted results are more reasonable, thus verifying the correctness of the new model. According to the influential factors analysis based on the new model, it is observed that although increasing the steam quality can effectively increase the steam-taking degree of the steam-injection wellbore, it has limited impact on reservoir heat efficiency. Moreover, the larger the steam-injection rate, the higher the steam-taking degree and reservoir heat efficiency. The reservoir heat efficiency decreases with the pay-zone thickness when the steam-injection wellbore has liquid.     

冷介质通过井筒注入某地质结构的流动与传热预测软件研发

通过井筒向某地质结构内注入冷介质时,由于地温与冷介质之间存在温差,冷介质将通过井筒结构与土壤进行热量交换,最终导致冷介质冷量损失进而温度升高而达不到所需温度要求。因此,在施工前,需要对井筒进行冷量损失和沿井筒的温度分布的预测,为保冷结构设计以及井筒结构材料选型提供数据支持。由于注入冷介质的过程中,热量交换过程是一个非稳态传热过程,通常只能采用数值模拟来进行预测。为了简化数值模拟复杂的计算过程,采用准稳态的传热方法来构建单相冷介质通过井筒注入时的流动换热的物理数学模型,并开发了一个数值仿真软件。将仿真结果同商业软件FLUENT模拟结果进行了比较,表明温度分布和冷量损失基本一致,由此验证了所提模型的正确性和可靠性,为非工程热物理专业的工程技术人员提供能够预测低温工质在井筒流动与换热过程的仿真软件。     

The numerical simulation and wellbore modelling of steam injection and stored heat recovery from light oil reservoir

ABSTRACT

Steam injection and thermal recovery of oil from the reservoir are increasing day by day. However, the recovery of the heat remained stored in the steam-flooded oil reservoir is nor in practice neither researched previously. A novel concept of steam injection and energy recovery from a light oil reservoir is presented in this paper. Reservoir numerical model of an actual oil field was generated and simulated with steam injection. Different parameters of thermal properties of geologic formations were discussed and adopted as per actual geology of the study area for more realistic simulation of heat storage, dissipation, and losses. After the optimum oil recovery, water was circulated through the same injection well into the reservoir to extract the energy in the form of heat, stored during the steam injection phase. The effects of different completion schemes of injection well were also simulated, discussed and pointed out for optimum oil recovery. Oil recovery factor is the most important parameter from both research and field development point of views. The comparative analysis was also carried out with the oil production without steam injection and found that steam flooding increased oil recovery factor up to more than 15% by decreasing the production time period up to 40% as compared to without steam injection oil production. The transmission of heat through conduction and convection mechanisms in the porous media, and through advective, dispersive and diffusive processes in the fluid was modeled. To fully investigate the feasibility of the concept presented in this paper, the production wellbore modeling was also carried out and temperature profile of recovered heat energy at the wellhead was obtained by acknowledging the thermal losses and found to be very useful for any direct and indirect utilization of heat throughout the energy recovery period of the reservoir.     

Wellbore temperature and pressure calculation model for supercritical carbon dioxide jet fracturing

A new numerical calculation model for wellbore temperature and pressure for SC-CO₂ jet fracturing was proposed in this research. In our model, the impact of tubing, casing, and cement on heat transfer, and the heat generated by fluid friction losses are all taken into consideration. The CO₂ physical properties are calculated by the Span–Wagner and Vesovic models. Based on our calculation model, the factors that may affect the wellbore temperature and pressure are discussed. The results indicated that ignoring the influence of the cement sheath thermal resistance on heat transfer would lead to a wellbore temperature higher than the actual value. The wellbore CO₂ pressure is always higher than its critical value, but the CO₂ temperature at the jet point in some cases is lower than its critical value. The wellbore CO₂ temperature is increased with the increase in injection temperature and cement sheath thermal conductivity and the decrease in annulus injection rate and coiled tubing injection rate. However, the decrease in the coiled tubing injection rate and increase in the cement sheath thermal conductivity are the only effective ways to ensure that the CO₂ temperature at the jet point exceeds its critical value.     

Wellbore temperature and pressure calculation model for coiled tubing drilling with supercritical carbon dioxide

To better control the state of carbon dioxide during supercritical carbon dioxide drilling, a mathematical model is established to analyze the wellbore carbon dioxide temperature and pressure influencing factors. In this model, the influences of formation temperature change and fluid-friction-generated heat on wellbore temperature distribution are considered. Additionally, the impact of casing, tubing, and cement sheath thermal resistance on heat transfer are considered. The model is validated by comparing the wellbore temperature data calculated from this model with data from previous models. Based on the model, the factors that may affect the wellbore carbon dioxide temperature and pressure are analyzed. The results show that the downhole temperature decreases with the decrease in nozzle diameter and geothermal gradient, and with the increase in injection rate. The injection temperature significantly affects the wellbore temperature near the wellhead, but it does not affect the downhole temperature. Therefore, for low geothermal gradient formation, reducing the injection rate and increasing the nozzle diameter are two effective methods to maintain the CO₂ at the downhole in the supercritical state. The pressure inside the coiled tubing increases with the increase in injection rate and decrease in nozzle diameter, but the injection temperature and geothermal gradient has little effect on the pressure inside both the coiled tubing and annulus.     

模拟井筒耦合传热大涡模拟的建模与数值求解

模拟井筒加温系统是研究油田井下高温高压环境的特种实验装置,其主体部分模拟井筒为耐高温高压的厚壁圆柱形封闭腔体,模拟井筒温度场是其加温系统设计与工作参数确定的基本依据。分析加热过程中腔体内流体与厚壁腔体之间的动态耦合传热,通过合理简化建立了井筒加热物理模型,给出了其基于大涡模拟方法的数学模型,采用有限差分法和应用投影法求解模型。研究结果表明：模型和求解方法可以用于高温高压模拟井筒流固耦合传热研究,其实验误差低于16%;通过模拟计算得到了井筒及其腔体内流体的动态耦合传热过程温度场分布规律,为模拟井筒加温系统设计与工作参数确定提供理论依据。     

A time-convolution approach for modeling heat exchange between a wellbore and surrounding formation

In oil, gas, and geothermal energy production, as well as geological CO₂ storage, the target formation is typically deeper than 1000 meters. As a result, associated wellbores have a large heat exchange area with the surrounding formation. Large gradients and temporal variations in temperature induced by the injection and production of fluids require accurate and efficient ways to calculate the heat exchange between fluids in the wellbore and the formation. One way to calculate this heat exchange is to fully discretize and numerically model the formation that surrounds the wellbore. However, because only the energy equation needs to be solved (i.e., there is no fluid exchange between the cased wellbore and the formation), this approach is computationally inefficient. In this work, we propose a time-convolution method, where only the wellbore is fully discretized, and heat exchange between fluids in the wellbore and the formation is calculated using semi-analytical solutions of radial conductive heat flow. The time-dependent temperature evolution in the wellbore is calculated numerically using a wellbore simulator for non-isothermal, multiphase fluid mixtures. At each time step, radial heat transfer with the formation is calculated by superposition of analytical solutions of heat flow that are dependent on the temperature differences between subsequent time steps. This coupling scheme is implemented in the TOUGH2 suite of reservoir simulators. To verify the proposed semi-analytical method and demonstrate its applicability, we present examples and compare them to full numerical solutions.     

超临界和超超临界汽轮机汽缸传热系数的研究

提出了汽轮机汽缸传热系数的计算方法。介绍了超，临界和超超临界压力汽轮机汽缸光滑内表面和安装镶片式汽封表面的对流换热表面传热系数的计算公式，安装整体车制式汽封的汽缸内表面、安装静叶的汽缸内表面和安装隔板的汽缸内表面的传热过程总传热系数的计算方法。采用圆筒壁与肋片传热等简化模型来计算汽封块、静叶和隔板的传热过程总传热系数。给出了某型号超，临界600MW汽轮机高压内缸内表面传热系数的计算结果。该方法考虑了不同运行工况下汽缸不同部位的传热过程，在超临界和超超临界压力汽轮机汽缸的温度场与热应力场的有限元法数值计算和寿命评定中，为确定传热边界条件提供了依据。