降低CO_2驱最小混相压力的方法

由于全球气候变暖,各国减排压力加大,近年来CO_2驱油技术发展迅速。该技术不仅适用于常规油藏,还适用于低渗以及特低渗透油藏,能有效提高原油采收率。CO_2混相驱的采收率明显高于非混相驱,但是中国多数油藏由于CO_2与原油的最小混相压力(MMP)过高而难以实现混相驱油。综述了国内外关于降低CO_2驱最小混相压力的方法,包括改变油藏温度,注入低分子量烃类、低碳醇、妥尔油以及近几年发展起来的表面活性剂技术等。分析了各个方法的优缺点,指出了今后CO_2驱发展的新方向。     

CO_2驱最小混相压力的影响因素分析

CO_2混相驱油方法被认为是现代驱油技术中,比较好的提高采收率方法。检测一个油藏是否能达到混相的条件是这个油藏的地层压力与最小混相压力进行比较,看是否高于最小混相压力。如此说来,确定最小混相压力就显得很有实际意义。通过研究最小混相压力,分析组分、温度、CO_2的不纯度对混相压力的影响。     

低渗透油藏CO_2驱油效果评价

针对低渗透油藏水驱采收率低,注水困难的特征,通过分析具体油藏的地质、储层及原油物性和最小混相压力等条件,确定了该油藏满足进行CO_2混相驱的要求。使用数值模拟软件Eclipse对该油藏进行模拟,对比连续注水、连续注气和周期注气三种开发方式,发现周期注气开发效果最好。当注停时间比为2:1时采出程度最高,分析其原因为注停时间比为2:1时,低渗透油藏能量的传播使地层压力重新均匀分布。对比不同CO_2驱替压力,发现当驱替压力在CO_2最小混相压力附近时采出程度最高,驱替压力大于最小混相压力,随着压力增大,采出程度越低,分析原因为储层发生堵塞现象。     

低渗油藏二氧化碳驱最小混相压力预测方法研究

向低渗油藏中注入CO2可以有效补充地层能量,显著提高采收率.最小混相压力是注气方案设计中最重要的参数,受到原油组成、注入气组成、温度等的影响.为研究不同理论方法预测注CO2最小混相压力的效果,以该油田某一油藏膨胀实验和细管实验测试的最小混相压力为基础,分别比较了经验公式、PR状态方程和系线解析法计算的二氧化碳-原油体系最小混相压力.优选了一种理论计算方法,并对该油田其他油藏的最小混相压力进行了有效预测.结果表明:系线解析方法计算的最小混相压力与细管实验测试值最接近,相对误差为2.2％,PR状态方程次之,经验公式误差最大;推荐采用系线解析方法来计算该油田低渗油藏注CO2驱最小混相压力.     

低渗透油藏二氧化碳驱油实验模拟研究

低渗透油藏在全世界油气资源中所占比例较大,气体驱替提高采收率是低渗透油藏开发的主要技术手段。本文研究了二氧化碳气体驱替原油的影响因素,并利用长细管实验法测出了本实验条件下二氧化碳的最小混相压力为20MPa,研究了不同注入压力,不同注入PV数,以及以氮气为主的杂质气体,温度等因素对二氧化碳提高采收率的影响,以期为今后二氧化碳气体驱油理论做实验参考。     

海上某油田注烃类气最小混相压力的研究

针对海上某油田采用注气提高采收率,其中重要是对最小混相压力的研究,分别采用了相态模拟法、细管实验法、经验公式法和类比法进行了最小混相压力的研究。     

低渗透油藏CO_2驱油机理及应用现状研究

当今社会快速发展,能源问题日益严峻。由于低渗透油藏低孔、低渗、自然能量不足等特点,采用常规方法已经不能有效采出原油,CO_2驱是三次采油方法中提高低渗透油藏采收率的一种方法。综述了CO_2驱油的机理、CO_2驱油效果的影响因素以及近些年来国内外CO_2驱油的应用现状,指出CO_2驱在我国低渗透油藏的可行性和巨大潜力。     

低渗透油藏二氧化碳混相与近混相驱替规律研究

实验先利用细管实验法确定出本次试验条件下二氧化碳的最小混相压力为26 MPa,再使用人造低渗透岩心并设定驱替压力分别为24 MPa近混相驱压力条件和28 MPa混相驱替压力条件进行驱油实验。结果是二者驱油效率变化基本一致,且混相驱替比近混相驱替最终驱油效率高出1.8个百分点,以期为后续研究二氧化碳驱油提供理论和实验基础。     

延长油田低渗透油藏二氧化碳驱油影响因素室内实验研究

针对延长油田低渗透油藏,通过开展岩心注气物理模拟实验,探索提高低渗透油藏CO2驱油开发效果影响因素及其规律。实验表明,不同驱替压力下,注入压力越高,采收率越高,注入压力高于最小混相压力后,采收率不再增加,采收率最高可达66.68%;并且注入压力增加,气体突破时间延迟;注入速度越高,采收率和换油率越高,CO2驱油开发效果越好,生产汽油比也越高;岩心渗透率高于1.26×10-3μm2时,渗透率增大,采收率差别不大,但相比水驱,采收率提高程度较大;岩心渗透率低于1.26×10-3μm2时,渗透率增大,采收率增大,但相比水驱,采收率提高程度较小。     

人工神经网络法预测二氧化碳-原油最小混相压力

CO2-原油的最小混相压力(MMP)是CO2采油过程中,尤其是混相驱油过程中的一个非常重要的参数。目前预测最小混相压力的方法中,实验法费时且花费很大;传统的数值方法只针对特定的油藏,适应性不强。鉴于此,亟需找到一种快速稳定的数学方法来预测最小混相压力。本文主要采用人工神经网络算法,通过建立网络模型,对地下油层中影响最小混相压力的主要因素-注入气体组分、油层温度和油层组成进行拟合来预测最小混相压力。文章还将该算法的预测结果与其它一些算法的结果进行了对比。通过对CO2-原油最小混相压力进行模拟预测,可为注入CO2采油提供可靠的理论依据,并以此指导注入CO2提高原油采收率工程的顺利实施。     

低渗断块油藏二氧化碳驱油实践

草舍油田泰州组油藏为低渗断块油藏,在二氧化碳驱油实践过程中,通过二氧化碳驱油机理、油藏适应性评价、驱油物理模拟、数值模拟等研究,优化了苏北盆地草舍油田泰州组油藏二氧化碳混相驱油方案及注入参数,方案实施取得了显著的增产效果,截止2011年底,已累积注入二氧化碳7380×104m3,油藏日产油由48t升至85t,综合含水由56.4%降为33.7%,增油5.6×104t,评价期末比水驱采收率提高16.8个百分点。该油藏二氧化碳驱油成功实践,为同类油藏大幅度提高采收率提供了方法技术借鉴。     

浅析CO_2汽提法尿素装置合成系统的NH_3/CO_2

介绍CO2汽提法尿素装置合成系统的NH3/CO2的控制方法,合成系统NH3/CO2异常的症状,判断方法,偏离正常时的处理和防范措施。     

Prediction of the viscosity reduction due to dissolved CO2 of and an elementary approach in the supercritical CO2 assisted continuous particle production of a polyester resin

The dissolution of CO₂ in a polymer causes plasticization of the polymer and hence, its viscosity is reduced. A model based on the free volume theory has been used for a polyester resin, which shows a considerable reduction in the viscosity due to dissolved CO₂. Therefore, supercritical CO₂ has been used as a processing solvent in the continuous production of micron size particles of the resin. Despite the viscosity reduction caused by the dissolved CO₂, an excess quantity of CO₂ with respect to its solubility limit has been used for micronisation of the polymer due to its high viscosity. The mixing of CO₂ and the polymer has not been possible in an extruder at high gas to polymer mass ratios and consequently, a simplified Kenics type static mixer has been used for the mixing purpose. In this study, the effect of various parameters such as temperature, pressure, nozzle diameter and gas to polymer mass ratio on the particle morphology and size has been studied. The experimental results manifest the technological as well as the theoretical insight into the particles production from a high viscosity material.     

The maximum capture efficiency of CO2 using a carbonation/calcination cycle of CaO/CaCO3

The use of natural calcium carbonates as regenerable CO₂ sorbents in industrial processes is limited by the rapid decay of the carbonation conversion with the number of cycles carbonation/calcination. However, new processes are emerging to capture CO₂ using these cycles, that can take advantage of the intrinsic benefits of high temperature separations in energy systems. This work presents an analysis of a general carbonation/calcination cycle to capture CO₂, incorporating a fresh feed of sorbent to compensate for the decay in activity during sorbent re-cycling. A general design equation for the maximum CO₂ capture efficiency is obtained by incorporating to the cycle mass balances a simple but realistic equation to estimate the decay in sorbent activity with the number of cycles.     

Kinetics of CO and H2 oxidation over CuO-CeO2 catalyst in H2 mixtures with CO2 and H2O

The kinetics of CO and H₂ oxidation over a CuO-CeO₂ catalyst were simultaneously investigated under reaction conditions of preferential CO oxidation (PROX) in hydrogen-rich mixtures with CO₂ and H₂O. An integral packed-bed tubular reactor was used to produce kinetic data for power-law kinetics for both CO and H₂ oxidations. The experimental results showed that the CO oxidation rate was essentially independent of H₂ and O₂ concentrations, while the H₂ oxidation rate was practically independent of CO and O₂ concentrations. In the CO oxidation, the reaction orders were 0.91, −0.37 and −0.62 with respect to the partial pressure of CO, CO₂ and H₂O, respectively. In the H₂ oxidation, the orders were 1.0, −0.48 and −0.69 with respect to the partial pressure of H₂, CO₂ and H₂O, respectively. The activation energies of the CO oxidation and the H₂ oxidation were 94.4 and 142 kJ/mol, respectively. The rate expressions of both oxidations were able to predict the performance of the PROX reactor with accuracy. The independence between the CO and the H₂ oxidation suggested different sites for CO and H₂ adsorption on the CuO-CeO₂ catalyst. Based on the results, we proposed a new reaction model for the preferential CO oxidation. The model assumes that CO adsorbs selectively on the Cu⁺ sites; H₂ dissociates and adsorbs on the Cu⁰ sites; the adsorbed species migrates to the interface between the copper components and the ceria support, and reacts there with the oxygen supplied by the ceria support; and the oxygen deficiency on the support is replenished by the oxygen in the reaction mixture.     

The effect of fly ash on fluid dynamics of CO2 scrubber in coal-fired power plant

Uncaptured fly ash and/or suspended solids from wet flue gas desulfurization (WFGD) scrubbing solutions are one of several factors that will influence the performance and robustness of carbon dioxide capture systems in coal-fired power plants which will be installed prior to the exhaust stack. In this study, a 100 mm ID packed column scrubber was tested with different concentrations of ash in various chemical solutions to evaluate the influence of solids on the fluid dynamics of the packing material. Data reported here are collected from three solutions including water, 30 wt% MEA (monoethanolamine), and 20 wt% potassium carbonate. The packing selected for this study was a 16 mm polypropylene pall rings. Compressed air was used to simulate flue gas at near ambient temperature and pressure.     

二氧化碳液化与输送技术

CO2过度排放导致的环境问题使世界各国都在想方设法将其回收后埋存或利用。但是,CO2的资源地离利用地一般较远,而且CO2在常温常压下为气态,如何将CO2安全经济地运输到目的地成为二氧化碳捕集技术大规模利用的技术关键。研究表明,采用液体输送方式可以降低系统能耗和成本。文章分析对比了不同二氧化碳液化方法的优劣性,并探讨了管线输送中需要注意的问题。     

薄层氮化碳光催化还原CO_2性能研究

以氮化碳(g-CN)为原料,采用水蒸汽焙烧剥离法在Ar/H2O氛围下制备薄层氮化碳(Hg-CN),并对其进行XRD、TEM、FT-IR、BET和UV-Vis DRS等表征。结果表明,进行剥离后,H-g-CN比表面积相比剥离前明显增大。H-g-CN的光催化还原CO_2活性大大高于未剥离gCN的活性,光照反应9 h,H-g-CN光催化还原CO_2活性由剥离前的11. 4μmol·g~(-1)提高至24. 6μmol·g~(-1),H-g-CN的CO选择性为91. 2%,未剥离的g-CN的CO选择性为89. 1%,并提出相应的反应机理。