Vapex—Gravity-assisted Film Drainage for Heavy Oil Recovery

Abstract

Reservoir heavy oils of viscosity higher than 20 cp are difficult to recover efficiently. A new vapor extraction process called Vapex which uses horizontal wells and volatile solvents is being developed, primarily in Canada. This process lowers the viscosity of the oil by dilution and the oil is produced by gravity drainage (vertical movement of fluids) to horizontal wells placed low in the reservoir. More oil should be produced at lower production and energy costs. The Vapex process is outlined in this article and followed by some experimental work demonstrating gravity drainage flow in films at the macro- and micro-scale.     

水平井火驱辅助重力泄油燃烧状态及燃烧前缘预测

为预测超稠油水平井火驱辅助重力泄油燃烧状态和燃烧前缘,采用自主研发的火驱物理模拟实验装置,利用物质平衡法,结合生产动态数据,计算得到燃烧腔体积,预测水平井火驱辅助重力泄油的燃烧前缘;利用生产过程中的气体组分、温度和压力等参数,表征油层燃烧状态。结果表明,温度是最能直观反映燃烧状态的参数,稳定燃烧状态下的燃烧腔与水平井水平段延伸方向存在30°左右的夹角,呈超覆燃烧特征,在水平井上端形成结焦带和油墙,可防止火线进入水平井筒。水平井火驱辅助重力泄油的稳定燃烧期,产出气中CO₂含量高于10%,O₂含量低于3%,水平井段温度低于300 ℃,且油墙压差低于生产压差的一半,若以上特征参数不能满足,水平井则可能出现气窜。     

Determination of gas dispersion in vapor extraction of heavy oil and bitumen

In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier.     

基于井筒离散模型的多元热流体吞吐机理

海上稠油油藏在多元热流体多轮次吞吐后,产量明显递减,开发效果变差。由于缺乏对多元热流体吞吐机理的认识,很难提出吞吐后开发调整的有效措施,有必要对水平井多元热流体吞吐开发机理进行研究。采用数值模拟方法,优选出井筒离散模型,通过与热水吞吐对比,剖析了多元热流体吞吐过程。结果表明,考虑多元热流体变质量流动影响以及井筒与地层耦合作用的井筒离散模型,能更真实反映稠油油藏水平井多元热流体吞吐的温度场和黏度场变化。井筒离散模型下的多元热流体吞吐模拟结果表明,沿水平井加热范围呈“长勺”状,且气液分离导致降黏范围逐渐增加。多元热流体吞吐通过热气复合降黏、扩大波及系数、气体辅助重力泄油和提高热效率,达到提高采收率的目的。     

稠油油藏水平井热采应用研究

本文油藏数值模拟技术研究了不同类型稠油油藏水平井注蒸汽开采的可行性、相应的开采方式及油层厚度与原油粘度对水平井注蒸汽开采效果的影响。     

Feasibility study on application of the recent enhanced heavy oil recovery methods (VAPEX,SAGD, CAGD and THAI) in an Iranian heavy oil reservoir

Enhanced oil recovery (EOR) methods assisted by gravity drainage mechanism and application of sophisticated horizontal wells bring new hope for heavy oil extraction. Variety of thermal and non-thermal EOR techniques inject an external source of energy and materials such as steam, solvent vapor, or gas through a horizontal well at the top of the reservoir to reduce in-situ heavy oil viscosity. So, the diluted oil becomes mobile and flows downwards by gravity drainage to a horizontal producer located at the bottom of the reservoir.

In this paper, a sector model of an Iranian fractured carbonate heavy oil reservoir was provided to simulate and evaluate capability of some EOR techniques such as Vapor Extraction (VAPEX), Steam Assisted Gravity Drainage (SAGD), Combustion Assisted Gravity Drainage (CAGD), and Toe to Heel Air Injection (THAI) at its reservoir conditions and fluid properties. The simulation results demonstrated that wet CAGD in comparison with other nominated methods could improve heavy oil recovery factor to around 19% much more than each of SAGD, THAI, and VAPEX techniques. It could also reduce the total energy to produced oil ratio index up to 82% with respect to SAGD process in a year.

Although lower oil recovery has been gained by VAPEX process, but using a proper vaporized solvent could produce a kind of de-asphalted and upgraded oil with increased API gravity up to 29°API with no considerable solvent loss.     

TTHW-趾端至跟部驱油法进行重力稳定注水开发的实验室研究——HeleShaw模型试验结果

论述了一种新颖的、重力稳定的注水开发过程--趾端至跟部注水开发（TTHw）的二维Hele-Shaw模型实验研究结果。该技术以直井作为注水井,水平井为生产井,采用井位交错排列的线性注水方式。水平井的趾端靠近直井,水平段位于油层上部,直井在油层下部处射孔,形成一种短距离驱油过程。油水重力分异作用使注入水向下流动,而水平井作为接收器引导水向上流动;两种力共同作用的结果是在跟部见水,然后是驱油前缘沿水平井段向前流动,从而使水流波及大部分生产层段。选用5种不同粘度的原油（10-12000mPa·s）进行实验,注水速率为2．5-320ml／h。总体来说,对中等粘度的稠油,传统水驱和TTHW水驱见水时的采收率相差不多,但水淹时,TTHW的最终采收率要高得多。     

Design and Numerical Study of a New Hybrid CSS-SAGD Process Using Horizontal Wells for Recovering Heavy Oil

Abstract

The cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) processes have extensively been applied as standard methods for Canadian oil sands extraction. Recently, many studies have been concentrated on CSS with horizontal wells and hybrid CSS-SAGD processes. In this article, a new hybrid CSS-SAGD process with two CSS horizontal wells and a single SAGD well is developed and investigated for shallow reservoirs by using the fourth SPE Comparative Solution Project adapted for oil sands reservoirs. Compared with the conventional CSS process, it is shown from simulation results that this new hybrid CSS-SAGD process is a more efficient recovery process.     

辽河油田超稠油油藏开采方式研究

辽河油田杜８４ 块兴隆台油层是一个超稠油油藏。由于地下原油粘度大,流动性差,因此常规直井蒸汽吞吐效果很差,平均周期油汽比只有０．３５。为了提高蒸汽吞吐开采效果,在油田现场采取了一系列技术措施,包括采用高效真空隔热油管、加深注汽管柱、采用大泵抽油等,措施后,周期油汽比提高到了０．５５９。同时,根据该油藏地质特征及原油性质,研究并试验了水平井注蒸汽开采、成对水平井蒸汽辅助重力泄油、水平裂缝辅助蒸汽驱及垂向燃烧辅助水平井重力泄油等新技术及开采方式。结果表明,水平井技术与重力泄油相结合,将是提高厚层超稠油开采效果的一种主要方式。     

浅层超稠油水平井微压裂扩容技术及应用

针对新疆油田F油田齐古组非均质油藏驱泄复合井网加密水平井与老井不均匀连通的问题,从改善水平段井筒周围渗流条件出发,提出水平井微压裂扩容改造技术。通过室内岩心实验、地质力学有限元模拟及热采数值模拟技术,分析了微压裂扩容技术的可行性及扩容后储层变化特征。结果表明:储层石英含量高,黏土矿物含量低且孔隙结构发育,有利于注水扩容改造;稳定提压过程中扩大挤注液的波及范围,进而降低周围储层有效围压,可大幅提升扩容改造程度;扩容后储层纵向位移量和孔隙度增大幅度明显优于横向,有助于上下注采井连通。微压裂扩容后经过5周期吞吐预热,油井间可快速建立热连通,预热期间周期产油、油汽比明显提升,且水平段动用程度大幅改善。研究结果可为提高驱泄复合井网的注采井间连通性提供借鉴。     

提高直井与水平井组合SAGD泄油速率技术研究

针对辽河油田直井与水平井组合SAGD井组在开发过程中存在泄油速率低、蒸汽腔扩展不均匀等问题,以R.M.Bulter建立的双水平井泄油模型为理论基础,将直井与水平井简化为双水平井,在考虑端点效应有限长度水平井日产量方程的基础上,建立了水平井的泄油速率模型,并得到直井与注汽水平井组合SAGD上产和稳产阶段的泄油速率方程。分析泄油速率方程发现,直井与水平井组合SAGD井组泄油速率的主控因素为泄油井点数和蒸汽腔纵向扩展高度,结合辽河油田稠油开发实践,给出了直井与水平井组合SAGD井组提高泄油速率的技术措施,即水平段跟部注汽井增加2口,并将注汽井注汽排量提高20%,同时将最佳射孔位置设在靠近低物性段处,补孔长度确定为8 m。该技术在辽河油田6井组进行了现场应用,日产油量均呈现不同程度的上升,取得阶段性成功,为进一步提高SAGD井组泄油速率奠定了良好的基础。      

蒸汽超覆对块状超稠油油藏剩余油分布影响研究

利用测井资料，结合油藏地质特征，建立了非均质地质模型。通过高温吸汽剖面、井温剖面、产液剖面等测试资料的分析，利用数值模拟手段研究了蒸汽吞吐开采过程中蒸汽的超覆作用，揭示了蒸汽超覆导致独特的油层温度分布特征及井间剩余油分布特征。研究表明，通过改变油井射孔方式、调整注汽参数等措施可以有效地减缓蒸汽超覆，提高油层纵向动用程度，降低油层纵向上的剩余油。在油层下部钻水平井，采取直井与水平井组合重力泄油方式，可以有效地动用井间剩余油，提高原油采收率。     

A NUMERICAL ANALYSIS OF THE SINGLE-WELL STEAM ASSISTED GRAVITY DRAINAGE PROCESS (SW-SAGD)

Steam assisted gravity drainage (SAGD) is an effective method to produce heavy oil and bitumen which are important energy resources. In a typical SAGD approach, steam is injected into a horizontal well located directly above a horizontal producer helping to displace heated oil. Single-well (SW) SAGD attempts to create a similar process using only one horizontal well. To improve early-time response of SW-SAGD, it is necessary to heat the near-wellbore area to reduce oil viscosity and allow gravity drainage to begin. Ideally heating should occur with minimal circulation or bypassing of steam. We have investigated early-time processes to improve reservoir heating. A numerical simulation study was performed to gauge combinations of cyclic steam injection and steam circulation prior to SAGD in an effort to better understand and improve early-time performance. Results from this study, include cumulative recoveries, temperature distributions, and production rates. It is found that cyclic steaming of the reservoir offers the most favorable option for heating the near-wellbore area to create conditions that improve initial SAGD response. More favorable reservoir conditions such as low viscosity, thick oil zones, and solution gas, improved reservoir response. Under unfavorable conditions, response was limited.     

A NUMERICAL ANALYSIS OF THE SINGLE-WELL STEAM ASSISTED GRAVITY DRAINAGE PROCESS (SW-SAGD)

Steam assisted gravity drainage (SAGD) is an effective method to produce heavy oil and bitumen which are important energy resources. In a typical SAGD approach, steam is injected into a horizontal well located directly above a horizontal producer helping to displace heated oil. Single-well (SW) SAGD attempts to create a similar process using only one horizontal well. To improve early-time response of SW-SAGD, it is necessary to heat the near-wellbore area to reduce oil viscosity and allow gravity drainage to begin. Ideally heating should occur with minimal circulation or bypassing of steam. We have investigated early-time processes to improve reservoir heating. A numerical simulation study was performed to gauge combinations of cyclic steam injection and steam circulation prior to SAGD in an effort to better understand and improve early-time performance. Results from this study, include cumulative recoveries, temperature distributions, and production rates. It is found that cyclic steaming of the reservoir offers the most favorable option for heating the near-wellbore area to create conditions that improve initial SAGD response. More favorable reservoir conditions such as low viscosity, thick oil zones, and solution gas, improved reservoir response. Under unfavorable conditions, response was limited.     

射孔水平井产液剖面均衡性影响因素分析

水平井产液剖面的均衡性间接反映了储层动用程度的均衡性,是射孔参数优化设计的重要依据。将源函数方法与表皮系数模型相结合,基于势的叠加原理,建立了各向异性油藏射孔水平井的油藏-井筒耦合模型,该模型可考虑地层损害和射孔等因素对水平井流入动态的影响,并给出了产液剖面和势分布剖面的求解方法。采用该模型分析得到了井斜角、油层厚度、地层原油黏度和垂向渗透率对射孔水平井产液剖面均衡性的影响规律。受井筒各处流态、泄油面积差异以及井筒内压力损失影响,射孔水平井的流量分布呈现端部效应和跟趾端差异,产液剖面呈斜"U"形;端部效应随着井斜角减小和垂向渗透率降低而减弱,随着油层厚度减小和原油黏度降低而增强;跟趾端的流量差异随着井斜角减小及油层厚度和垂向渗透率降低而减小,随着原油黏度的降低而增大。      

正韵律厚油层剩余油的水平井开发技术研究

与直井相比,水平井开发具有缩短油井井距,扩大泄油面积,提高临界锥流量,更好地控制注入流体、改善波及效率等优势。在相同采液量的情况下,水平井可以降低采液强度,减缓含水上升速度。特高含水期河流相储集层的顶部是剩余油富集区,利用水平井技术挖掘正韵律厚油层顶部剩余油,取得了很好的开发效果,最终采收率较直井开发提高了14个百分点。     

基于旋转磁偶极子的钻井轨迹高精度导向定位方法

传统随钻测量无法满足水平对接连通井、蒸汽辅助重力驱油中的成对平行井钻井等复杂结构井高精度导向定位技术需求。为直接测量钻头与目标靶点的距离及方位信息,提出了一种基于旋转磁偶极子模型的高精度导向定位方法。通过对动态旋转磁偶极子的磁信号空间传播规律的研究发现,旋转磁偶极子可以等效为正交磁偶极子的叠加,并且存在能够对旋转磁偶极子进行导向定位的特征磁场信号,该特征信号可以通过希尔伯特变换对三轴可测磁信号进行相位解调和幅度解调获得。仿真结果表明,钻头越接近目标靶点,定位误差越小,定位精度越高。基于旋转磁偶极子的钻井轨迹高精度导向定位方法对SAGD成对平行井、煤层气开发水平对接连通井及可溶性盐卤矿井高精度钻井轨迹导向定位具有重要应用价值。     

泡沫油型超重油冷采后转SAGD开发数值模拟

泡沫油型超重油油藏原始溶解气油比高,地下可形成泡沫油流,水平井冷采初产较高,但一次衰竭开发采收率低。因此,开展了泡沫油型超重油冷采后转SAGD开发技术研究。根据研究区块油藏地质特征,建立了泡沫油冷采及热采数值模拟模型,研究了泡沫油SAGD驱油机理和开发技术政策。研究结果表明,与油砂SAGD不同,泡沫油具有流动性,泡沫油SAGD驱油机理为在注采井形成热连通之前蒸汽驱油为主、重力泄油为辅,形成热连通后蒸汽驱油为辅、重力泄油为主。泡沫油SAGD启动阶段不需要预热,注采井间垂向井距应适当增大。地层压力下降后油相中析出的溶解气附着在蒸汽腔侧面上影响蒸汽腔的横向扩展。因此,冷采转SAGD时机应尽量延后,当冷采至较低地层压力、溶解气含量大幅降低时转SAGD开发效果更好。由于区块构造具有倾角,生产井水平段井轨迹应保持水平,有利于形成合理的SAGD汽液界面;在满足技术经济条件下,缩小SAGD排距可提高采出程度。提出了提高SAGD开发效果的措施：1采用上下两口水平井冷采,有利于减少溶解气含量,提高SAGD开采效果;2对于多井SAGD,采用（交替）不平衡注汽,可促进蒸汽腔发育,提高采出程度。     

双水平井蒸汽辅助重力泄油生产井控制机理与应用

结合现场监测资料和解析方法,对双水平井蒸汽辅助重力泄油（SAGD）开采的机理进行了研究。分析表明,在蒸汽腔中,流动以重力泄油为主,压力梯度较低;在注汽井和采油井间汽液界面下的流体流动规律与蒸汽腔中靠重力泄流为主不同,汽液界面下的流动以注汽井和采油井间的压力驱替为主,压力梯度相对较高。在认识采油井压力梯度分布的基础上,运用离散化井筒模型对采油井的汽阻温度（sub-cool）控制进行了优化,并与现场分析结果进行了对比。结果表明,双水平井蒸汽辅助重力泄油采油井的汽阻温度控制在10~15℃为宜。     

丛式水平井组在复杂断块油藏开发中的应用研究

胜利油田永8复杂断块油藏的特点是断层多、油层层数多、含油面积小、储量丰度高，开发过程中油层易出砂，直井产量低。水平井的优点是泄油面积大、生产压差小、产量高。在优选水平井在断块平面和油层纵向的位置、水平段长度高等基础上，设计并实施了永8－X4块的一个丛式水平井组。该水平井组投产初期的平均日产量是直井的两倍。实现了高效开发复杂断块的目的。图2参18（李顺明摘）