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.     

The Semi-Analytical Modeling and Simulation of the VAPEX Process of “Kuh-e-Mond” Heavy Oil Reservoir

Abstract

The vapor extraction process (or VAPEX) uses vaporized solvents injected into a horizontal well to form a vapor chamber within the reservoir. Vapor dissolves in the oil and enhances the oil production by decreasing the oil viscosity in heavy oil reservoirs. To evaluate the process we conduct a simulation study on an Iranian heavy oil reservoir called Kuh-e-Mond. In addition, a semi-analytical investigation of the VAPEX process has been performed. The idea is to perform VAPEX simulation for a laboratory model and find a methodology to compare the results of the simulator with the semi-analytical Butler's model. In particular, a semi-analytical dimensionless correlation for production rate that incorporates all involved physical parameters in the VAPEX process is developed. Also, we performed a sensitivity analysis on the proposed correlation to obtain its adjustable parameters and optimize using available experimental data.     

溶剂辅助重力泄油技术开采稠油室内试验

多孔介质和Hele-Shaw设备中的溶剂辅助重力泄油开采机理不同,特别是两者产生脱沥青作用的压力范围是否一致及增产幅度的差别程度如何尚不明确。为研究溶剂辅助重力泄油技术开采多孔介质中稠油的机理,建立了3层结构的溶剂辅助重力泄油可视化填砂模型,对高渗岩心溶剂辅助重力泄油不同注入压力与泄油速率关系及相同注入压力下不同渗透率岩心溶剂辅助重力泄油脱沥青降黏作用和堵塞流动通道的复合作用机理进行了室内试验研究。试验结果表明:多孔介质溶剂脱沥青作用出现在饱和蒸气压附近,试验泄油速度提高3倍,但脱沥青作用发生的压力范围较小;脱沥青作用会造成低渗地层部分孔喉堵塞。因此,低渗地层VAPEX溶剂注入压力应低于溶剂的饱和蒸气压,而高渗地层则可以充分利用脱沥青降黏作用来提高泄油速率。      

注有机极性气体开采稠油技术

针对储层薄、埋藏深的稠油油藏开发难度大及开采成本高的问题,在注溶剂萃取稠油技术（VAPEX）的基础上,提出向稠油油藏注入一种低饱和蒸汽压的有机极性气体PE提高采收率的采油技术。利用相态观察及黏度测定两种方法研究了该气体与稠油在气态和液态两种情况下的降黏效果。另外,还对比了该气体与VAPEX中常用烃类气体LPG对稠油降黏及萃取效果。实验结果表明:该气体在原油中具有很好的溶解性,能大幅度降低原油黏度;和LPG与稠油作用不同,该有机气体在液态状态下能大量分散稠油中的沥青,形成一种低密度低黏度混合相。现场应用表明注入该气体的措施井增产效果明显,因此,该注气技术可适用于一些埋藏深、油层薄、渗透性差和黏度高的稠油油藏。     

注水开发砂岩油田参数计算方法

本文考虑地质、开发、经济和提高采收率方法及各开发参数间的定量影响关系,提出和推导了一套注水开发砂岩油田参数(提高采收率方法提高采收率幅度,合理注入化学剂段塞体积、合理井网密度、界限井网密度、合理采油速度、最大采液速度、合理稳产时间、合理油水井数比)的计算方法。并举出一个应用这套方法的实际油田算例,     

An Efficient Approach for the Determination of Oil Production Rate During the Water-flooding Recovery Method

In this work, a mathematical methodology namely, least square support vector machine (LSSVM) is implemented to predict the variation of oil production rate as a function of oil water viscosity ratio and water injection rate for water-flooding. Furthermore, the coupled simulated annealing (CSA) optimization technique is coupled with LSSVM to find the optimal architecture and parameters of the LSSVM. The obtained results demonstrate that the CSA-LSSVM estimations are in a satisfactory agreement with literature-reported data and the previously published correlation. Consequently, the R² and average absolute relative deviation of CSA-LSSVM model in testing phase are reported 0.979 and 8.15, respectively.     

On the determination of breakthrough time for water coning phenomenon in oil reservoirs

The water coning phenomenon leads to decrease the wellhead pressure with moving of water into oil production zone, which is regarded as one of most serious problems during oil production. Therefore, the development of reliable models is important to predict the water coning breakthrough time, and consequently avoid the water coning phenomenon and production of water. To this end, the artificial neural network modeling strategy optimized with particle swarm optimization, least square support vector machine (LSSVM) approach coupled with the coupled simulated annealing optimization method, and finally decision tree method are implemented in current study to accurately predict the dimensionless breakthrough time of water coning. The results obtained in the present study demonstrate that the models proposed provide acceptable results in predicting the dimensionless breakthrough time of water coning. Furthermore, comparative study conducted illustrates the superiority of LSSVM methodology in terms of accuracy compared to the other methods investigated.     

用钻特殊井方法提高采收率

尽管三次采油过程的各种提高采收率技术在经济、合理、最大限度的开采石油方面发挥了重要作用,但由于许多技术目前尚处于部分工业运用及实验室研究阶段,加上许多技术本身的局限性和油藏的复杂性,导致其效果并不理想。随着钻井技术的进步,水平井、侧钻水平井、分支井、大位移井等特殊井在提高石油采收率上的贡献日见报道,但是从观念认识上,往往没有把这些钻井方法列入提高石油采收率的技术之列。文中在讨论目前各种提高采收率技术的优点和不足之处的基础上,提出了对现有采收率技术不适用的油藏而言,用特殊井提高采收率比现有各种提高采收率技术优越,并阐述了钻井方法提高采收率技术的优点及其前景。     

Evaluation of the EOR Potential in Hydraulically Fractured Shale Oil Reservoirs by Cyclic Gas Injection

Gas flooding in fractured reservoirs may not be an effective avenue for improving oil recovery because the injected fluids could break-through to production wells via the fracture network. A cyclic injection scheme is one way to solve this problem. In this study, the authors propose to use cyclic gas injection to improve hydraulically fractured shale oil recovery. They used a simulation approach to evaluate the enhanced oil recovery (EOR) potential from cyclic gas injection. The simulation results indicate that total oil recovery can be increased up to 29% by cyclic gas injection, compared with the 6.5% recovery from the primary depletion. If a higher pressure is used to reach fully miscibility with reservoir oil and more cycles are employed, more oil recovery is expected.     

Application of CFD technique to simulate enhanced oil recovery processes:current status and future opportunities

Nowadays,because of the reduction in oil resources and the passage of the first and second life period of current reservoirs,using enhanced oil recovery(EOR) methods is of great importance.In recent years,due to the developments in technology and the advent of powerful computers,using simulation methods in enhanced oil recovery processes is on the rise.The computational fluid dynamics(CFD) method,as a branch of fluid mechanics,is a suitable method for studying and simulating EOR methods.In this study,a review was done on the application of CFD studies for simulating EOR methods.Also,potentials for future studies and the challenges researchers may face in this method were mentioned.Although using this method in enhanced oil recovery processes has recently started,different areas for more studies still exist.To optimize the usage of this method in future studies,the necessity of multiphase models and solution methods development,as well as considering all microscopic parameters such as interfacial tension and viscosity in investigating oil recovery factor is of great importance.     

Microbial Enhanced Oil Recovery (MEOR)

Microbial enhanced oil recovery (MEOR) represents the use of microorganisms to extract the remaining oil from reservoirs. This technique has the potential to be cost-efficient in the extraction of oil remained trapped in capillary pores of the formation rock or in areas not swept by the classical or modern enhanced oil recovery (EOR) methods, such as combustion, steams, miscible displacement, caustic surfactant-polymers flooding, etc. Thus, MEOR was developed as an alternative method for the secondary and tertiary extraction of oil from reservoirs, since after the petroleum crises in 1973, the EOR methods became less profitable. Starting even from the pioneering stage of MEOR (1950s) studies were run on three broad areas, namely, injection, dispersion, and propagation of microorganisms in petroleum reservoirs; selective degradation of oil components to improve flow characteristics; and metabolites production by microorganisms and their effects.     

The influence of steam injection for Enhanced Oil Recovery (EOR) on the quality of crude oil

Currently, due to reduction of oil reservoirs and the increasing need for oil as the main source for world energy, the need for production of heavy oil reservoirs is inevitable. The main purpose of this study is to determine the effectiveness of some operational and reservoir parameters and their impact on thermal and productive efficiency of thermal process of steam injection and quality of crude oil. In order to model the process, Eclipse-300 simulator was employed. Detection of these parameters, in addition to determining the best production scenario, can lead to the use of this method with better economic conditions. Hence, the results obtained from this study show that the optimal values obtained for operational parameters of stream injection such as steam quality, steam injection pressure, injection rate and well completion injection depth. The simulation results show that the use of optimal values of steam injection parameters can enhance efficiency of steam injection method and can make this method considered as third EOR method in heavy oil reservoirs than previously known in the petroleum industry.     

Microbial Enhanced Oil Recovery (MEOR)

Abstract

Microbial enhanced oil recovery (MEOR) represents the use of microorganisms to extract the remaining oil from reservoirs. This technique has the potential to be cost-efficient in the extraction of oil remained trapped in capillary pores of the formation rock or in areas not swept by the classical or modern enhanced oil recovery (EOR) methods, such as combustion, steams, miscible displacement, caustic surfactant-polymers flooding, etc. Thus, MEOR was developed as an alternative method for the secondary and tertiary extraction of oil from reservoirs, since after the petroleum crises in 1973, the EOR methods became less profitable. Starting even from the pioneering stage of MEOR (1950s) studies were run on three broad areas, namely, injection, dispersion, and propagation of microorganisms in petroleum reservoirs; selective degradation of oil components to improve flow characteristics; and metabolites production by microorganisms and their effects.     

The Effective Diffusion/Dispersion Coefficient in Vapor Extraction of Heavy Oil

Abstract

In this study, a new correlation for determination of effective diffusion/dispersion coefficients in the vapor extraction of heavy oil/bitumen (VAPEX) is introduced. This model takes into account the solvent concentration as well as the drainage height and permeability dependency of these coefficients. The concentration dependency in this model stems from the mixture viscosity changes, while the height dependency appears directly in the correlation. The correlation was obtained using the experimental results of the VAPEX experiments that were conducted with physical models of varying sizes and different permeability sand-packs. Estimation of a proper mass transfer coefficient has been a challenging issue for the analytical and numerical simulation of the VAPEX and other similar processes. Incorporating the effect of drainage height on dispersion with a concentration-dependent diffusivity model enables one to estimate the dispersion coefficient values involved in this process.     

Application of LSSVM algorithm as a novel tool for prediction of density of bitumen and heavy n-alkane mixture

The most of oil reservoirs in the world are heavy oil and bitumen reservoirs. Due to high viscosity and density of these types of reservoirs the production has problems so importance of enhanced oil recovery (EOR) processes for them is clear. The injection of solvents such as tetradecane is known as one of methods which improve oil recovery from bitumen reservoirs. In the present investigation, the Least squares support vector machine (LSSVM) algorithm was used to estimate density of Athabasca bitumen and heavy n-alkane mixture in term of temperature, pressure and weight percent of the solvent. The Root mean square error (RMSE), average absolute relative deviation (AARD) and the coefficient of determination (R²) for total dataset are determined 0.033466, 0.0025686 and 1 respectively. The predicted results indicate that the LSSVM algorithm has potential to be a predicting machine for the bitumen-heavy alkane mixture density prediction.     

水力振动采油技术研究及试验

水力振动增产技术是一种新的提高采收率方法。近年来，振动采油技术的研究和应用进展很快。介绍了水力振动器的结构、工作原理和现场试验效果，通过现场试验，并且对试验井增油资料的统计分析认为．使用水力振动器产生的低频率、高振幅的水力脉冲波，能够解除油层近井地带的堵塞和污染，从而使原油增产明显，且产量稳定。对推动振动采油技术的研究和应用具有十分重要的意义．     

A shortcut model to estimate oil production rate in VAPEX process

An analytical model for estimating the oil production rate in the vapor extraction process (VAPEX) is presented in this work. It regards the most effective properties of fluid and reservoir in the form of the Rayleigh number. The model involves three coefficients (x₁, x₂ and x₃) that are determined through minimizing an objective function based on the difference between experimental VAPEX data and calculated data. The strength of the model was examined through comparison experimental work. Having an average relative error of 15% against the real data, the model showed its high capability for predicting the VAPEX production rate.     

A Laboratory Study of Recovery with Carbon Dioxide around Critical Conditions of Trinidad's Heavy Oil and Tar Sands

Abstract

VAPEX is a heavy oil recovery process where two horizontal wells are placed low in a reservoir and solvents passed into the reservoir via the higher of the two wells. This lowers the oil viscosity and allows the oil–solvent mixture to move to the lower well. CO₂ could be a suitable solvent.

Some experimental work on heavy oil recovery using CO₂ at points around its critical conditions of 31°C and 73.3 bar is presented here. The recovery was between 15 to 30% with most of the extracts lying in the range above C₁₂. Reservoirs deeper than 2500 ft are therefore suited to this type of process.     

改变微观水驱液流方向提高剩余油采收率试验研究

为了弄清特高含水油藏微观剩余油类型及提高剩余油的动用效果,进行了微观水驱油特征试验研究.在分析剩余油的几何特征和建立孔喉特征分析方法的基础上,进行了剩余油分类.采用微观可视化驱替试验、图像识别与统计等方法,定量分析了改变液流方向对微观剩余油的影响.试验结果分析表明:不改变液流方向的水驱剩余油饱和度为20.90%;改变液流方向后,继续水驱后剩余油饱和度降为9.69%;改变液流方向后原油采收率可提高11.2百分点.研究表明,改变液流方向后,随着注水量增加,分支状和连片型剩余油饱和度呈指数递减,油膜状、柱状和滴状剩余油饱和度先增大后减小,符合二次多项式函数关系.研究结果为水驱提高剩余油采出程度提供了理论基础.      

喇萨杏油田特高含水期油层分类

大庆油田已进入特高含水阶段,随着开采技术政策的转变,特别是三次采油技术的发展,传统上的油层分类已很难满足当前生产的需要.为此,在论述了喇萨杏油田特高含水期油层重新分类必要性的基础上,本着油层分类概念要有延续性、油层类别平面上具有整体性、对现有技术有一定的适应性、分类标准具有可操作性的思想,同时考虑三次采油的需要,制定了油层分类的具体原则.按照砂体沉积类型、主要砂体钻遇率、单层有效厚度、有效渗透率等4个参数建立定量标准,将喇萨杏油田的油层分为3大类,6小类.油层重新分类后,每一类的油层性质更接近,有利于开发层系的组合;对于聚合物驱来说,还有利于聚合物分子量的选择和注入参数的确定;对于三元复合驱,还有利于配方的选择与设计.