Application of an expert system to optimize reservoir performance

The main challenge of oil displacement by an injected fluid, such as in Enhanced Oil Recovery (EOR) processes, is to reduce the cost and improve reservoir performance. An optimization methodology, combined with an economic model, is implemented into an expert system to optimize the net present value of full field development with an EOR process. The approach is automated and combines an economic package and existing numerical reservoir simulators to optimize the design of a selected EOR process using sensitivity analysis. The EOR expert system includes three stages of consultations: (1) select an appropriate EOR process on the basis of the reservoir characteristics, (2) prepare appropriate input data sets to design the selected EOR process using existing numerical simulators, and (3) apply the discounted-cash-flow methods to the optimization of the selected EOR process to find out under what conditions at current oil prices this EOR process might be profitable. The project profitability measures were used as the decision-making variables in an iterative approach to optimize the design of the EOR process. The economic analysis is based on the estimated recovery, residual oil in-place, oil price, and operating costs. Two case studies are presented for two reservoirs that have already been produced to their economic limits and are potential candidates for surfactant/polymer flooding, and carbon-dioxide flooding, respectively, or otherwise subject to abandonment. The effect of several design parameters on the project profitability of these EOR processes was investigated.     

OPTIMIZING OIL RECOVERY IN A CARBONATE RESERVOIR THROUGH INTEGRATED RESERVOIR SIMULATION STUDIES

A three-dimensional finite-difference reservoir simulator, integrated in an EOR expert system, has been used to determine the reservoir management and production strategies to optimize the oil recovery from a carbonate reservoir. The reservoir is a candidate for an EOR process or otherwise subject to abandonment. After screening the reservoir for an appropriate EOR process on the basis of its properties, it was determined that miscible carbon-dioxide injection is the most suitable process. The management strategies involved studying different design parameters to maximize the project profitability. The injection techniques that were tested in this study include: (1) water-alternating-gas (WAG), (2) simultaneous water-alternating-gas (SWAG) injection, and (3) gas injection in the bottom of the reservoir with water injection in the reservoir top. All simulation runs were conducted using permeability fields that have been conditioned with core data taken from wells in the field. Specific strategy that was used includes the use of horizontal injectors in conjunction with vertical producers. This well configuration has been shown to yield the best oil recovery compared to other well configurations. Simulation results show that the most economical method to produce this reservoir was to simultaneously inject water at the reservoir top and gas at the reservoir bottom. This production strategy has resulted in better sweep efficiency and therefore high oil recovery and good economics.     

OPTIMIZING OIL RECOVERY IN A CARBONATE RESERVOIR THROUGH INTEGRATED RESERVOIR SIMULATION STUDIES

ABSTRACT

A three-dimensional finite-difference reservoir simulator, integrated in an EOR expert system, has been used to determine the reservoir management and production strategies to optimize the oil recovery from a carbonate reservoir. The reservoir is a candidate for an EOR process or otherwise subject to abandonment. After screening the reservoir for an appropriate EOR process on the basis of its properties, it was determined that miscible carbon-dioxide injection is the most suitable process. The management strategies involved studying different design parameters to maximize the project profitability. The injection techniques that were tested in this study include: (1) water-alternating-gas (WAG), (2) simultaneous water-alternating-gas (SWAG) injection, and (3) gas injection in the bottom of the reservoir with water injection in the reservoir top. All simulation runs were conducted using permeability fields that have been conditioned with core data taken from wells in the field. Specific strategy that was used includes the use of horizontal injectors in conjunction with vertical producers. This well configuration has been shown to yield the best oil recovery compared to other well configurations. Simulation results show that the most economical method to produce this reservoir was to simultaneously inject water at the reservoir top and gas at the reservoir bottom. This production strategy has resulted in better sweep efficiency and therefore high oil recovery and good economics.     

A simple approach for screening enhanced oil recovery methods: Application of artificial intelligence

The main goal of the present article is to propose a machine learning model which was constructed by merging the real worldwide enhanced oil recovery (EOR) field experiences. In this regard, the aforementioned expert system is based on fuzzy C clustering approach in order to rank the appropriate EOR methods for further evaluation from environmental and economic viewpoints. The results show that fuzzy C clustering approach can be successful in the determination of appropriate EOR method by providing adequate data face to the approach evolved. Consequently, this expert system can be hybridized with commercial reservoir simulators for EOR screening purposes especially in Iranian oil and gas sector.     

An optimization methodology of alkaline–surfactant–polymer flooding processes using field scale numerical simulation and multiple surrogates

After conventional waterflood processes the residual oil in the reservoir remains as a discontinuous phase in the form of oil drops trapped by capillary forces and is likely to be around 70% of the original oil in place (OOIP). The EOR method so-called alkaline–surfactant–polymer (ASP) flooding has proved to be effective in reducing the oil residual saturation in laboratory experiments and field projects through the reduction of interfacial tension and mobility ratio between oil and water phases.A critical step to make ASP floodings more effective is to find the optimal values of design variables that will maximize a given performance measure (e.g., net present value, cumulative oil recovery) considering a heterogeneous and multiphase petroleum reservoir. Previously reported works using reservoir numerical simulation have been limited to sensitivity analyses at core and field scale levels because the formal optimization problem includes computationally expensive objective function evaluations (field scale numerical simulations). This work presents a surrogate-based optimization methodology to overcome this shortcoming.The proposed approach estimates the optimal values for a set of design variables (e.g., slug size and concentration of the chemical agents) to maximize the cumulative oil recovery from a heterogeneous and multiphase petroleum reservoir subject to an ASP flooding. The surrogate-based optimization approach has been shown to be useful in the optimization of computationally expensive simulation-based models in the aerospace, automotive, and oil industries. In this work, we improve upon this approach along two directions: (i) using multiple surrogates for optimization, and (ii) incorporating an adaptive weighted average model of the individual surrogates.The cited approach involves the coupled execution of a global optimization algorithm and fast surrogates (i.e., based on Polynomial Regression, Kriging, Radial Basis Functions and a Weighted Average Model) constructed from field scale numerical simulation data. The global optimization program implements the DIRECT algorithm and the reservoir numerical simulations are conducted using the UTCHEM program from the University of Texas at Austin.The effectiveness and efficiency of the proposed methodology is demonstrated using a field scale case study.     

卫42块特低渗透油藏氮气驱研究

在研究中原油田卫42块油藏构造,储层物性特,流体性质及开发特点的基础上,探讨了深层特低渗透油藏提高收率,提高开发水平和经济效益的有效途径。利用室内实验结果,分析了氮气驱油和水驱油的特征以及对其采收率的影响,研究分析氮气驱技术和经济上的可行性,认为卫42块低渗油藏完全满足氮气驱的条件,在卫42块进行单井注氮矿场试验,结果周围对应的2口井产量增幅达53．0％,数值模拟预测,采收率可提高8．0％。     

深层稠油油藏天然气吞吐优化方案设计

随着天然气源的大量发现与注天然气提高采收率技术的不断完善,注天然气开发稠油油藏已成为提高稠油采收率的重要技术手段。针对某油田深层稠油油藏的地质及开发特点,在室内实验和相态拟合的基础上,建立了油藏数值模拟模型。利用历史拟合调整后的组分模型对注天然气吞吐提高深层稠油采收率方案参数进行了优化。根据参数优化方案,使注天然气吞吐开发深层稠油油藏取得了较好的增油降水效果。     

聚驱后三元复合驱进一步提高采收率数值模拟研究

首先利用正交实验设计,确定了化学剂最佳注入程序为0.1PV聚合物前置段塞、0.45PV三元复合剂主段塞、0.05PV聚合物后续保护段塞,其次再依据聚驱后区块特点及实际情况,设计了三套井网方案并开展了聚驱后三元复合驱进一步提高采收率数值模拟研究。数模结果表明,三元复合驱与前一阶段聚驱相比平均可提高采收率12.9%,其中,水平井和直井的注采组合方案提高的采收率幅度最大,达到15.97%,所以聚合物驱后应综合考虑水平井的注采调整和三元复合驱的多重优势,以期取得更好的开发效果。     

聚合物驱后井网调整与非均相复合驱先导试验方案及矿场应用——以孤岛油田中一区Ng3单元为例

为了进一步提高聚合物驱后油藏原油采收率,提出了井网调整与非均相复合驱相结合的提高采收率方法,并在孤岛油田中一区Ng3单元开展了先导试验。根据试验区油藏特点,将原井网调整为变流线强波及的135 m×150m行列式井网;研制了由粘弹性颗粒驱油剂B-PPG、聚合物和表面活性剂配制而成的非均相复合驱油体系,2010年7月,试验区新钻油井投产,新水井投注,于2010年10月开始注入前置调剖段塞。矿场应用效果显著:注入井平均注入压力上升了2.6 MPa,启动压力平均上升了2.7 MPa,霍尔阻力系数达2.2;流线分布更均匀,驱替更均衡;试验区总产油量由4.5 t/d上升到81.2 t/d,油井综合含水率下降了18.5%,截至2013年2月,已累积增产原油4.3×104t,提高采收率3.5%。     

A New Material Balance Equation Model for Analyzing Dynamic Performance of CO2 Flooding

Implementing a CO2 flooding scheme successfully requires the capacity to get accurate information of reservoir dynamic performance and fluids injected. Despite some numerical simulation studies, the complicated drive mechanisms and actual reservoir performance have not been fully understood. There is a strong need to develop models from different perspectives to complement current simulators and provide valuable insights into the reservoir performance during CO2 flooding. The aim of this study is to develop a model by using an improved material balance equation (MBE) to analyze quickly the performance of CO2 flooding. After matching the historical field data the proposed model can be used to evaluate, monitor and predict the overall reservoir dynamic performance during CO2 flooding. In order to account accurately for the complex displacement process involving compositional effect and multiphase flow, the PVT properties and flowability of reservoir fluids are incorporated in the model. This study investigates the effects of a number of factors, such as reservoir pressure, the amount of CO2 injected, the CO2 partition ratios in reservoir fluids, the possibility of the existence of a free CO2 gas cap, the proportion of reservoir fluids contacted with CO2, the starting time of CO2 flooding, oil swelling, and oil flowability improvement by mixing with CO2. The model was used to analyze the CO2 flooding project in Weyburn oil field, Saskatchewan, Canada. This study shows that the proposed model is an effective complementary tool to analyze and monitor the overall reservoir performance during CO2 flooding.     

A New Material Balance Equation Model for Analyzing Dynamic Performance of C_2 Flooding

1. Introduction CO2 flooding is considered one of the most effective tertiary recovery processes in light/medium oil reservoirs and has been widely used in petroleum industry. However, the complicated displacement mechanisms involved CO2 injection have not been fully understood. Monitoring reservoir performance and obtaining accurate information regarding reservoir fluids and injected fluid by using actual field data will help to understand displacement mechanisms and manage the CO2 injectio…     

聚合物驱数学模型的若干问题

随着聚合物驱理论、油田开发技术和化学工艺的发展,现有的聚合物驱数学模型在油藏开发模拟过程中暴露出一些问题,如驱油体系流变特性、渗流特性、物理化学特性,聚合物驱提高采收率机理、开发效果,原油物性,模拟计算等。依据渗流力学、物理化学、提高采收率及物理模拟实验理论讨论了现有聚合物驱数学模型在质量守恒方程、驱油体系表观黏度模型、聚合物驱残余油饱和度模型、水相渗透率下降系数、可及孔隙体积以及原油黏度模型中存在的问题,并提出了相应的解决方法和改进的模型。     

辽河中深层稠油蒸汽驱油藏工程优化研究

齐40区块蒸汽驱先导性试验已取得阶段性成果,蒸汽驱可作为中深层稠油油藏蒸汽吞吐后有效的开发方式。利用数值模拟方法和油藏工程方法对蒸汽驱油藏工程优化设计思路、方法及转驱时机进行了研究。并对齐40区块蒸汽驱单井采液能力及注入能力、井网井距优选、蒸汽驱操作参数、射孔方式进行了优化优选。     

聚合物驱后剩余油分布核磁成像实验研究

聚合物驱后剩余油分布特征是选择进一步提高采收率技术措施的重要依据。通过利用核磁成像技术，在二维纵向层内非均质物理模型和五点法井网仿真平面非均质物理模型上对聚合物驱后剩余油分布特征进行了实验研究。实验结果表明，核磁成像实验方法所得模型剩余油分布特征与常规实验方法所得结果基本一致。由核磁成像实验方法确定的聚合物驱后剩余油分布特征是，对于二维纵向层内非均质物理模型，剩余油主要分布在中、低渗透层；对于五点法井网仿真平面非均质物理模型，剩余油主要分布在远离注入井的边、角区域。     

特高含水油藏CO_2气水交替驱注入参数优化方法

影响CO2气水交替驱开发效果的参数较多,为了得到最佳开发效果,以特高含水开发阶段的A井组为研究对象,运用数值模拟方法,对该井组CO2气水交替驱注入参数进行了优化,建立了一套CO2气水交替驱、提高采收率注入参数优化的思路和方法。结果表明:实施CO2气水交替驱能使高含水井含水率下降5~10个百分点,增加产油,并保持地层压力稳定,维持油井长时间经济有效生产。     

Pre-prepared Microemulsion Flooding in Enhanced Oil Recovery: A Review

It is evident that one of the important applications of microemulsions is in enhanced oil recovery (EOR) process due to its unique properties such as ultra-low interfacial tension. The injection of microemulsion slug reduces the interfacial tension between the crude oil and reservoir brine, which leads to mobilization of substantial fraction of residual oil. In general microemulsion flooding is classified into two distinct categories, pre-prepared and in situ prepared, depending on its preparation method. The authors present a detailed discussion of microemulsion preparation and summarizes major articles on pre-prepared microemulsion flooding in EOR processes. Their review opens new horizons for the future researches on pre-prepared microemulsion flooding in EOR processes by organizing the literature data and comparing them.     

油田弱碱三元复合驱采油工艺设计模式

聚合物驱油是大庆油田成熟配套的提高采收率技术,随着油田开发的不断深入,部分二类油层转向弱碱三元复合驱开采,普遍存在着油井产液量变化幅度大、结垢速度快、结垢量大、液体黏度大、机采井检泵周期短及投资高等问题。在南四区西部区块二类油层弱碱三元复合驱采油工艺设计过程中,提出了"地下地面协同化"提高油井产能、"机电设计一体化"降低油井能耗、"降本增效立体化"控投资降成本的思路。对三元复合驱采油工艺设计的模式和方法进行了有益探索和尝试。区块投产规模大,增油效果好,经济效益显著。对同类油田的开发具有重要的指导作用。     

A Laboratory Investigation into Carbon Dioxide Flooding by Focusing on the Viscosity and Swelling Factor Changes

Abstract

Carbon dioxide flooding is an efficacious method of enhanced oil recovery (EOR) that has become one of the most important EOR processes. It is a very complicated process, involving phase behavior that can increase oil recovery by means of swelling, evaporating, and lowering oil viscosity. The present investigation reports the results of extensive experimental and theoretical work (using Eclipse 300 [2007]) to determine the viscosity and swelling factor changes of the live oil in the Cheshmeh Khoshk reservoir in southwestern Iran (Ilam District); minimum miscible pressure (MMP) was also determined. In this study, the potential of carbon dioxide injection application in improving oil recovery by simulating slim-tube experiments was studied. In order to obtain representative fluid samples of a reservoir, the right operation of mixing the separator oil and gas samples to match the bubble point pressure was necessary. The potential application of the study is that a good estimate of the recovery improvement under carbon dioxide gas injection, which will be the basic input parameters for the economic feasibility study, and a decision can then be made whether to implement or abandon the prospective project.     

任11井山头注氮气可行性研究

碳酸盐岩潜山油藏是华北油区的主要油藏类型,其动用地质储量占全油区的60%左右,目前已进入高含水开发期,如何挖潜剩余油潜力,进一步提高采收率,是目前的主要工作方向。针对任11井山头块状底水潜山油藏的地质及生产特点,分析了注氮气提高采收率的机理及有利地质条件;在数值模拟的基础上,论证了任11井山头注氮气提高采收率的可行性,对注气井数、油气水平衡时间、采液速度、注气采油方式、注气速度、注气时机和开发井网等技术政策界限进行了优化研究。研究结果表明,任11井山头在一定工艺技术保障下,注氮气提高采收率是可行的,预计注气形成的富集油带厚度约200m,采收率提高4%左右。     

海上低渗透薄互层油藏合理动用方式研究

目前国内海上低渗透油田开发处于起步阶段,介绍了利用数值模拟与油藏工程方法,确定合理开发层系,优化注水时机,提高此类油藏开发效果和经济效益的试验研究情况。结果表明,由于海上低渗透薄互层油藏的非均质性强,低渗透层若要达到较好的水驱效果,其综合影响因子要小于5,即层间渗透率级差要控制在8以内,夹层的数目在6~7层以内。针对于公司海上油田的特殊性,应采取投产即注水的开发方式,以获得更高经济效益。