华北BN油藏注二氧化碳混相驱室内试验评价

对CO2与华北BN油藏原油之间的相态特性和驱替特性进行了较系统的实验室试验评价，内容包括：油气系统的相态特性试验研究、注CO2模型试验研究和CO2与地层原油间的界面特性测量。通过这些试验认为，CO2溶于地层原油后，可以较大幅度地降低油气界面张力和原油粘度，提高驱油效率。     

文184断块二氧化碳混相驱及油藏数值模拟研究

依据１８４断块油藏条件和原油物性特点,认为采用ＣＯ２混相驱是提高该区采收率的一种有效方法。通过对全区注水处理的历史拟合,设计了两种不同注入方式－－单段塞注气和水气交替注入。油藏数值模拟结果表明,ＣＯ２与１８４断块地层流体在目前压力下可以混相,水气交替注入方式比单段塞柱气方式提高采收率幅度要高。     

水驱废弃油藏注二氧化碳驱室内试验研究

为探讨进一步提高高温、高盐水驱废弃油藏采收率潜力,以河南濮城沙一下亚段油藏为目标,开展了注入CO2流体性质变化、细管驱替、长岩心驱替室内试验。试验验证了注入CO2可改善原油流动性、有效增加地层能量和可动油等驱油机理;油藏原油性质好,混相压力低,目前油藏条件可达到混相;优选CO2/水交替驱为最佳注入方式;优化了注入段塞组合;组分检测分析认为CO2/水交替驱波及到了水波及不到的原油。研究结果为濮城沙一下亚段油藏CO2驱矿场试验提供了技术支持,并对其他特高含水期油藏注CO2进一步提高采收率同样具有借鉴意义。     

大庆油田注天然气非混相驱矿场试验研究

大庆油田已进入高含水期，河流三角洲相正的律厚油层存在着严重的非均质性，注水开发效果较差，为了改善开发效果，选择低，高弯度河型厚油层两个试验区进行了注天然气非混相驱先导性矿场试验，试验表明，水，气交替注入后，在油层中的形成油，气，水三相流动，增加了渗流阻力，改善了吸入剖面，由于重力分异作用，驱扫了正韵律厚油层顶部的剩余油，对于河流相储层，顺点坝走向或河道沉积方向注气效果好，试验区现已有提高采收率３．     

注天然气混相驱油藏筛选新方法

注天然气混相驱是提高原油采收率的重要手段之一.在注富气和贫气天然气混相驱替机理分析和注气工程动态分析的基础上,找出各种影响注气效果的因素,并选取其主要的参数,建立其相应的评价指标体系;结合油层物理和油藏工程评价方法,在对相应评价指标进行量化的基础上,引入现代决策分析方法,利用基于理想最优方案的指标赋权法,对候选油藏进行筛选排序和综合评价,体现各种影响因素对注气的整体影响,最后用于矿场试验.     

国外混相驱动态

混相驱作业,美国主要用CO_2气作工作剂,加拿大主要用富烃气作工作剂,另外还有用丙烷、石油液化气,也有用C_2—C_6的烃化物作工作剂的。35年来,混相驱已发展成为一种成功的EOR方法,对美国、加拿大的油田增产潜力可观。但各国发展缓慢。文中对美加两国研制使用情况作了一定介绍。     

烃类混相驱的室内研究

９０年代初开始，中国西部不断发现挥发油藏，在编制部分此类油藏的开发方案过程中，进行了较系统的烃类混相驱的室内研究。室内研究包括各种物理实验和一维，二维，三维的混相，近混相，非混相及水气交替的组份模型模拟计算。文中总结了北京石油勘探开发科学研究院在烃类混相驱室内研究中的一些成果，提出了此类研究的推荐工作流程，同时讨论了对烃混相机理的一些新认识 。     

注富烃气凝析/蒸发混相驱机理评价

基于状态方程和气液两相相平衡理论,建立了注气压力组成及多级接触实验相平衡的计算模型,再应用建立的计算模型,根据室内注气配套实验(压力组成实验、多级接触实验、细管实验)数据,模拟压力-组成相图、多级接触拟三元相图和细管特征曲线,评价注气驱混相能力及驱替机理。应用该方法对吐哈盆地丘陵油田注富烃气混相驱机理进行了评价,研究了该过程中油气两相中的C1、C2-C6和C7-组分、界面张力、密度与黏度等特性参数的变化规律,证实了注富烃气驱替过程中存在凝析和蒸发双重作用,因此在较低界面张力状态(即近混相)下采收率可以达到与混相驱接近的效果,认为凝析／蒸发混相就是近混相的提法不妥。图5表1参12     

商13—22单元CO2驱室内实验研究

通过对胜利油田商１３－２２单元进行的ＣＯ２驱室内实验研究,确定了商１３－２２单元的最小混相压力,原油与ＣＯ２体系的基本物性、ＣＯ２原油的膨胀降粘效果以及现场进行驱替时的合理注入方式,提出了胜利油田ＣＯ２驱室内研究的一般思路,对胜利油田利用ＣＯ２驱提高低渗透油田采收率具有一定的指导意义。     

Flow Properties of CO2/Crude Oil in Miscible Phase Flooding

Abstract

The high-temperature and high-pressure three-dimensional (3D) device is used to study miscible flooding of CO₂ and crude oil. The experiment model is a real sand plate. In oil reservoir condition, there is a large difference between production and injection volume. The complex flowing characteristics of CO₂ flooding in pore media are observed in recovery, water cut, and gas–oil ratio curves. By analyzing the water saturation contour plot measured by a saturation probe, CO₂ and oil can be miscible. The viscosity of miscible liquid and flowing pressure decreases. This is the important mechanism of enhanced oil recovery. When the viscosity of miscible liquid and flowing pressure decreases, miscible CO₂ and oil contacted with water can make a similar three phase. This is the important mechanism of enhanced oil recovery. Based on the conclusion, the main reason for the production and injection difference is that high-density CO₂ would flow into pore media in which water and oil cannot flow.     

Experimental Investigation of Miscible CO2 Flooding

Abstract

Management of water alternating gas (WAG) injection projects requires making decisions regarding the WAG ratio, half-cycle-slug size, and ultimate solvent slug size. The impact of these decisions affects the capital cost and ultimate incremental oil recovery. Core flooding runs were conducted on 2 and 4 ft core samples. Injection scheme (continuous gas injection [CGI] vs. WAG), WAG ratio, and slug size were investigated. In addition, miscible WAG flooding as a secondary process was investigated and its efficiency was compared to the conventional tertiary miscible gas flooding. Miscible gas flooding at different miscible WAG parameters (WAG ratio and slug size) indicate that 1:2 WAG ratio at 0.2 PV slug size is the best combination yielding the highest recovery and tertiary recovery factors. Miscible WAG flooding as a secondary process indicated a higher ultimate recovery compared to the conventional tertiary WAG flooding. However, a larger amount of gas injection is consumed particularly in the early stages of the injection process. Miscible CGI mode conducted using n-Decane as oleic phase appears to have better performance than miscible WAG injection in term of recovery. When light Arab crude oil was used as oleic phase, higher recovery was obtained for miscible WAG flooding. The reversal trend seen in is believed to be due to the presence of crude oil, which alters the rock wettability toward an oil-wet condition, preventing the water blockage during the WAG process.     

低渗透油藏 CO2混相条件及近混相驱区域确定

为了探究CO_2在低渗透油藏中与原油的混相条件及在近混相条件下的驱油效果,采用室内物理模拟方法,通过均质、非均质长方体岩心实验,在评价影响CO_2驱油效果的渗透率、岩心长度、渗透率级差和压力因素的基础上,借助采收率与各影响因素参数指标,分析非混相、近混相和混相不同阶段的曲线特征,建立了近混相驱区域的确定方法。采用该岩心实验方法,在模拟油藏条件下,CO_2与原油的最小混相压力为18.5 MPa左右,比传统细管实验确定的17.8 MPa高出0.7 MPa,同时根据驱油曲线特征,划分了CO_2非混相、近混相和混相区域,并根据驱油效率确定出近混相驱的压力区域为16.5数18.5 MPa。建立的最小混相压力岩心测定方法和近混相驱区域划定的方法,为进一步深化CO_2近混相驱油机理的认识及YC油田CO_2矿场驱油方案的设计提供了参考。     

Modeling of Asphaltene Deposition During Miscible CO2 Flooding

The authors present the results of numerical tests and simulations to investigate and analyze the likelihood of asphaltene precipitation and deposition during CO₂ flooding in a reservoir. The effects of asphaltene precipitation on oil properties such as oil viscosity and density during miscible CO₂ flooding process were elaborated by using Winprop software of Computer Modeling Group. Also oil properties change during CO₂ miscible flooding by numerical slim tube were investigated by a compositional simulator (GEM). A fluid sample of Saskatchewan Reservoir that had been flooded miscibly with CO₂ was chosen for performing the sensitivity analyses. The results showed that asphaltene precipitation reduces the oil viscosity and density that is in favor of production increasing. On the other hand asphaltene deposition causes resistance in oil production due to porosity and permeability reduction. The competition between these two effects declares the positive or negative effect of asphaltene on recovery that could be different for each reservoir. The results also show that decreasing the rate of CO₂ injection leads to an increase in asphaltene deposition near the injective well. Due to this phenomenon in higher injecting rates the increment in well bottom-hole pressure becomes less.     

富民油田CO2混相驱提高采收率现场分析

注气是继水驱、聚合物驱、蒸汽驱之后提高原油采收率的又一重要技术.富民油田富14块具有CO2 混相驱的各种有利地质条件;CO2混相驱有效地提高了该区块的采收率,在试验阶段内原油采收率提高了2.09%;CO2混相驱的关键在于确保油藏的地层压力高于最小混相驱压力值及合理的注入方式与注入速度.     

长庆油田CO2驱储层溶蚀与地层水结垢规律*

针对长庆油田CO_2先导试验驱地层水矿化度高,Ca~(2+)、Mg~(2+)、Ba~(2+)、Sr~(2+)含量高,储层岩石易溶蚀的特点,开展了CO_2-地层水与CO_2-岩石-地层水相互作用的研究以及CO_2驱对储层岩石的影响模拟实验。结果表明,在地层水注入CO_2的过程中,pH值、压力和温度的改变对地层水中阳离子浓度的影响很小,不会导致无机垢的生成。在注气井近井地带,随着注入压力不断升高,溶解在地层水中的CO_2增加,溶液pH值下降,储层岩石发生溶蚀。岩心片与CO_2作用后,岩心片更加亲水,这有利于改善储层物性,提高原油采收率。在采出井近井地带,由于压力的降低,使原本溶解于地层水中的CO_2大量逸出,地层水中的碳酸氢盐矿物分解成不溶性的碳酸盐沉淀,导致储层渗透率降低,孔隙度减小,对储层造成伤害,不利于长8储层低渗油藏采油。图10表3参13     

沥青质沉积对轻质油藏CO2驱的影响

为了解沥青质沉积对轻质油藏CO_2驱的影响,以CO_2及延长轻质原油为介质,在不同压力、不同CO_2与原油物质的量比的实验参数下,研究了CO_2对沥青质的沉积规律以及沥青质沉积对油水界面性质、原油组成、储层渗透率及采收率的影响。研究结果表明:当压力从0 Pa升至20 Pa时,沥青质沉积量从0.17%增至6.27%;沥青质沉积导致的储层渗透率损害程度从1.87%增至13.64%,油水界面张力原来的2.40 mN/m增至16.80 mN/m。压力在25 MPa时原油采收率最大,达到11.83%。     

判断CO2混相段形成时机的方法

分析了两相流体稳定发展过渡带的存在特点,引入瞬时换油率随注入孔隙体积倍数的三段式变化规律,定义最小稳定注入量概念,并阐述了其物理意义.设计常规细管实验,在混相驱状态下测试瞬时换油率曲线,通过图解法得到瞬时换油率开始转向近水平的A点,进而确定最小稳定注入量.实验还发现,混相程度越高,最小稳定注入量越小,混相段形成的越早.     

沙一下油藏CO2混相驱替提高采收率的研究

以沙一下区块油藏为对象,研究了CO2混相驱技术可行性及提高采收率,通过PVT实验和细管模拟实验,确定了油藏原油的最小混相压力为18.41 MPa,原油采收率达90.01%。实验结果表明,注气驱达到混相压力后,注入压力对驱油效率影响不大,而在混相压力以下的近混相区,注入压力对驱油效率影响非常大。通过长岩心驱替模拟实验,对比了水驱和CO2驱替效率,结果表明CO2混相驱提高采收率达40.8%。     

河南油田高温油藏聚合物驱的驱油效率

针对河南双河油田V下区块高温(84.3℃)低渗的油藏特点,选取不同水解度的聚丙烯酰胺(1630s和ZL-I)进行驱油实验.结果表明,高浓度聚合物驱油效率明显高于低浓度聚合物,最佳聚合物浓度为1 600～2 000 mg/L.驱替实验表明,现场聚合物最佳注入量为0.4～0.5 PV.聚合物老化前后对比驱油实验表明,低水解...