边底水稠油油藏吞吐后期转驱研究

锦45块为辽河油田典型的中厚互层状边底水普通稠油油藏,2000年区块产量进入递减阶段,为了控制吞吐后期产量递减趋势,转换开发方式势在必行。在广泛调研国内外类似油藏转驱研究成果和现场实施效果的基础上,在锦45块开展了室内物理模拟研究和数值模拟研究,最终确定了锦45块于Ⅰ组推荐转连续蒸汽驱方式,预计最终采收率55．26％。     

The effect of bitumen molecular fractions on diffusivity and rheology of bitumen under high-temperature conditions: Molecular dynamics (MD) simulation study

Heavy oil and bitumen play an incredible role in Canada's energy resources. The main processes that have already been applied to produce heavy oil and bitumen are in-situ thermal methods. The primary mechanism of production in these reservoirs is a reduction in heavy oil and bitumen viscosities via heat transfer. Having deep knowledge about the rheological behaviour of heavy oil and bitumen is crucial to designing a more accurate and efficient in-situ thermal recovery method. In this work, molecular dynamics (MD) simulation was used to model the rheological behaviour of bitumen under different temperatures. According to MD outputs, the highest diffusion coefficient between bitumen fractions belongs to saturate fractions. On the other hand, the lowest diffusion coefficient belongs to asphaltene fractions. The size of asphaltene, its polarity, and the polarity of a resin fraction affect the diffusion coefficient of asphaltene in a bitumen sample and its rheological behaviour. The MD simulation aims to provide molecular insights and essential information about the rheological trend of bitumen under different thermodynamic conditions. The results of the current work provide essential information about the effect of bitumen fractions on its rheological behaviour.     

Simulating the displacement of a heavy oil by a lighter oil in an offshore production line

An analysis was conducted on the displacement of a heavy fluid by a miscible light fluid in the flow assurance operation of injecting diesel oil to displace heavy oil in an insulated offshore production line. A three-dimensional computational fluid dynamics model was developed and implemented in OpenFOAM®. It stimulates the production stages, no-touch time, and oil displacement, considering heat transfer through natural convection and conjugated heat transfer through the solid layers of the pipeline. The specific test case focused on the first 180 m of an existing offshore production line. The simulations revealed two primary mechanisms of mixing: turbulence and secondary flows generated by the pipeline curves. Remarkably, the results demonstrate that by injecting a volume of lighter oil 1.3 times the pipeline volume, approximately 90%–95% of the heavy oil can be effectively removed.     

薄层稠油油藏水平井分段蒸汽驱筛选研究

针对小断块或井场开采条件受限的薄层稠油油藏,提出水平井分段蒸汽驱的开发方式。因蒸汽驱对油藏条件要求高,故投产前须进行筛选。根据不同原油粘度和油层厚度的组合模拟计算结果,研究原油粘度和油层厚度对稠油油藏水平井分段注采开发效果的影响,建立筛选评价标准。研究结果表明,当油层有效厚度超过7.2m时,可利用水平井分段蒸汽驱经济开采原油粘度低于5000mPa.s的普通稠油油藏;油层有效厚度达9.6m时,该技术可用于开采原油粘度低于20000mPa.s的稠油油藏。     

A review on the application of nanofluids in enhanced oil recovery

Enhanced oil recovery (EOR) has been widely used to recover residual oil after the primary or secondary oil recovery processes. Compared to conventional methods, chemical EOR has demonstrated high oil recovery and low operational costs. Nanofluids have received extensive attention owing to their advantages of low cost, high oil recovery, and wide applicability. In recent years, nanofluids have been widely used in EOR processes. Moreover, several studies have focused on the role of nanofluids in the nanofluid EOR (N-EOR) process. However, the mechanisms related to N-EOR are unclear, and several of the mechanisms established are chaotic and contradictory. This review was conducted by considering heavy oil molecules/particle/surface micromechanics; nanofluid-assisted EOR methods; multiscale, multiphase pore/core displacement experiments; and multiphase flow fluid-solid coupling simulations. Nanofluids can alter the wettability of minerals (particle/surface micromechanics), oil/water interfacial tension (heavy oil molecules/water micromechanics), and structural disjoining pressure (heavy oil molecules/particle/surface micromechanics). They can also cause viscosity reduction (micromechanics of heavy oil molecules). Nanofoam technology, nanoemulsion technology, and injected fluids were used during the EOR process. The mechanism of N-EOR is based on the nanoparticle adsorption effect. Nanoparticles can be adsorbed on mineral surfaces and alter the wettability of minerals from oil-wet to water-wet conditions. Nanoparticles can also be adsorbed on the oil/water surface, which alters the oil/water interfacial tension, resulting in the formation of emulsions. Asphaltenes are also adsorbed on the surface of nanoparticles, which reduces the asphaltene content in heavy oil, resulting in a decrease in the viscosity of oil, which helps in oil recovery. In previous studies, most researchers only focused on the results, and the nanoparticle adsorption properties have been ignored. This review presents the relationship between the adsorption properties of nanoparticles and the N-EOR mechanisms. The nanofluid behaviour during a multiphase core displacement process is also discussed, and the corresponding simulation is analysed. Finally, potential mechanisms and future directions of N-EOR are proposed. The findings of this study can further the understanding of N-EOR mechanisms from the perspective of heavy oil molecules/particle/surface micromechanics, as well as clarify the role of nanofluids in multiphase core displacement experiments and simulations. This review also presents limitations and bottlenecks, guiding researchers to develop methods to synthesise novel nanoparticles and conduct further research.     

Optimization strategies and impact of low oil price on long term SAGD projects

Steam assisted gravity drainage (SAGD) has been known as a commercially proven high ultimate recovery process for bitumen and heavy crudes. It is an energy intensive process, which is economical when oil price is above certain value. When the oil price goes below the economic threshold of project, steam injection can be decreased or completely stopped for a certain period of time, and can resume thereafter when the condition alters. The objective of this study is to provide comprehensive information about the effect of steam injection interruptions on thermal project performance. An optimization strategy for the SAGD process, in cases where steam injection interruption occurs, is discussed using actual reservoir models of different geological formations. An economical model is used to evaluate operating strategy effect on the net present value (NPV) of the project. The parameters, like shut-in period, initial steam injection period, etc, are optimized for Athabasca type oil sand reservoirs. The results show several key mechanisms exist in the life cycle of the SAGD process that must be included to reflect the field scale behaviour; otherwise, the mechanistic simplicity of the models could lead to directional and semi-quantitative conclusions. Among the mechanisms, temperature effect on basic petrophysical properties of reservoir rocks was found to have an important role in the oil recovery, and considerably impacts the results of optimization. When the steam injection is interrupted, an optimum shut-in period can be determined to maximize the oil recovery. The optimum length of steam injection interruption depends on the initial steam injection period.     

Optimal rate allocation for production and injection wells in an oil and gas field for enhanced profitability

An oil and gas field requires careful operational planning and management via production optimization for increased recovery and long-term project profitability. This article addresses the challenge of production optimization in a field undergoing secondary recovery by water flooding. The field operates with limited processing capacity at the surface separators, pipeline pressure constraints, and water injection constraints; an economic indicator (net present value, NPV) is used as the objective function. The formulated optimization framework adequately integrates slow-paced subsurface dynamics using reservoir simulation, and fast-paced surface dynamics using sophisticated multiphase flow simulation in the upstream facilities. Optimization of this holistic long-term model is made possible by developing accurate second-order polynomial proxy models at each time step. The resulting formulation is solved as a nonlinear program using commercially available solvers. A comparative analysis is performed using MATLAB's fmincon solver and the IPOPT solver for their robustness, speed, and convergence stability in solving the proposed problem. By implementing two synthetic case studies, our mathematical programming approach determines the optimal production and injection rates of all wells and further demonstrates considerable improvement to the NPV obtained by simultaneously applying the tools of streamline, reservoir, and surface facility simulation for well rate allocation via systematic NLP optimization.     

B16油藏合理开发技术政策研究

B16油藏于1989年3月投产,1990年4月开始注水开发,截止2008年6月累积产油206.4674×104t,累计产气2.9871×108m3,原油采出程度和溶解气采出程度分别为23.12%和44.14%。为了高效开发该气藏,以获取较高的采收率和经济效益,对该油藏进行了开发数值模拟研究。利用地质研究成果对B16油藏建立了相应的地质模型,在此基础上进行了储量拟合。对该油藏的生产历史数据进行历史拟合研究,取得了良好的拟合效果。对油藏"保持现有井网"继续开发20年,模拟预测相关的开发指标,总结剩余油的分布状况。从注采井网完善、地层压力保持程度、初期注采比等几个方面对该油藏的开发技术政策进行了数值模拟研究,所得的研究结论有利于指导该油藏实际开发生产。     

Multiphase isenthalpic flash: General approach and its adaptation to thermal recovery of heavy oil

Isenthalpic flash is a basic equilibrium calculation in process simulation. The recent interest in isenthalpic multiphase flash is mainly caused by the need for simulating thermal recovery of heavy oil. We present here systematic solutions to multiphase isenthalpic flash with full thermodynamics (such as EoS models) or with correlations for K-factors, and discuss how to tailor the general methods to systems encountered in thermal recovery of heavy oil. First, for the general situation with full thermodynamics we recommend a solution strategy which uses Newton's method for rapid convergence in the majority of cases and Q-function maximization to safeguard convergence when Newton's method fails. The solution procedure is a generalization of Michelsen's state function based two-phase flash to multiple phases. The general solution does not need special considerations for the components in the system and is not limited to the selected thermodynamic models and the number of phases. For thermal recovery processes where gas, oil, and aqueous phases are typically involved, the stability analysis and initialization steps are tailored to improve the efficiency. Second, as it is quite common in thermal reservoir simulators to describe phase equilibrium and heat properties with temperature-dependent K-factors and separate correlations for heat capacities, we propose a formulation as an extension of the ideal solution isothermal flash formulation to solve such problems. It uses a Newton–Raphson procedure to converge in the majority of cases and a nested loop procedure with the outer loop for a temperature search as a fallback approach for convergence. If the correlations for K-factors and for heat capacities are thermodynamically consistent, the outer loop can be treated as a maximization. Finally, we present systematic tests of the proposed algorithms using examples with full thermodynamics or K-factor based thermodynamics. The algorithms prove robust and efficient even in challenging cases including a narrow-boiling system, a degenerate system, and a four-phase system. The additional computational cost relative to the corresponding isothermal flash is modest and would be suitable for the purpose of thermal reservoir simulation. © 2018 American Institute of Chemical Engineers AIChE J, 65: 281–293, 2019     

秦皇岛32-6南区少井高产虚拟开发研究

秦皇岛32—6南区原油粘度高密度大,具有常规稠油的特点,目前生产状况极不乐观。本文采用数值模拟方法,对边底水油藏进行了垂向渗透率及开采速度敏感性分析,从储量合理动用、先进井型确定、合理产能设计等几个方面进行了虚拟开发研究。结果表明,秦皇岛32—6油田南区采用水平井开发可有效提高采出程度,改善开发效果。开发过程中先动边水主力油藏、然后动用边水构造岩性油藏、最后动用底水油藏可取得最佳开发效果。通过虚拟开发,提出了少井高产的思路。     

注蒸汽热采技术研究进展

在研究大量文献的基础上,总结了注蒸汽采油的机理,概述了稠油注蒸汽热采的研究现状与发展趋势,着重探讨了稀油注蒸汽热采的应用前景、研究现状以及稀油注蒸汽热采还需要深入研究的课题。研究认为：稠油注蒸汽热采已是比较成熟的技术,在稠油开发中占有重要的地位,其发展趋势为利用天然气、溶剂、高温泡沫、聚合物等来改善注蒸汽热采效果;稀油油藏水驱、聚驱后转注蒸汽热采具有可行性,今后需重点解决的问题包括采用煤或核能生产蒸汽、采用水汽交注、蒸汽泡沫等方法提高稀油油藏注蒸汽热采的采收率。     

页岩油冷凝回收油洗工艺模拟与优化

针对我国页岩油冷凝回收油洗工艺尚不成熟的问题,提出了一种用于油页岩干馏油气冷凝回收的油洗工艺,并运用PRO/II流程模拟软件对工艺流程进行模拟,分析模拟结果表明,所提出的油洗工艺能够有效地完成页岩油的冷凝回收,并将油气粗分为净油气、汽油、柴油和重油。针对所提出流程能量利用率低的缺点进行流程改造优化,优化后的热量回收率提高了约14.63%,并且能够获得高品位热源,能量匹配更加合理。同时对油洗塔汽油回流量进行了分析,确定最优的汽油回流量为3100 kg/h。     

From pore scale to wellbore scale: Impact of geometry on wormhole growth in carbonate acidization

Acid injection in carbonate reservoir is commonly used in the oil industry to improve, or at least recover, its productivity. The aim of this stimulation technique is to create empty channels called wormholes which, if successful, would bypass the damaged area near the wellbore. During production, wormholes become pathways for the reservoir oil to reach the well. This technique increases near-wellbore permeability, and therefore improves oil production. The interaction between the transport of acid, chemical reaction, and heterogeneities encountered at different scales, controls the unstable behaviour of wormholing and, thus, the success of the treatment. Most of the experimental and numerical studies done on this subject in the past have been limited in their observations because they only considered the dissolution process at a small scale (from pore scale to core scale). The purpose of this work is to study how the geometry of the domain can constrain wormhole competition, and influence wormholing dynamics in a core submitted to acidizing.After a short review of the literature on wormholing to see how the geometry effect could have influenced previous experiments, we study specifically the question of wormhole density. We emphasize that two mechanisms are involved in wormhole competition, with one of them being effective only at small scale. Thus we conclude that wormholing is not a full-scale independent process. We describe differences in the wormhole growth dynamics between “confined” and “unconfined” domains for different dissolution regimes. We focus on optimum conditions and their transition from “confined” to “unconfined” domain to realize that the flow rate in the dominant wormhole does not depend on geometric effects. We conclude by a comparison between 2D and 3D simulations, in both linear and radial flow, and observe changes in the wormholing process. All our results serve as a discussion about definitions of optimum conditions in the literature.     

重质油包水乳液破乳过程及降黏强化机制

重质油包水（W/O）乳液普遍存在于石油开采与加工过程中,因其高黏度、高密度、强界面稳定特性,导致重质油包水乳液分离困难,生产成本增加。为了提高重质W/O乳液的分离效率,本文探究了温度与甲苯加入量对重质油黏度的影响规律。在此基础上,研究了上述降黏过程与脱水率之间的协同机制。采用自制的TJU-3破乳剂对重质W/O乳液进行破乳,通过调整破乳剂在乳液中的浓度和破乳温度得到了最佳工艺条件。利用分子模拟的方法构建了重质油平均分子模型并计算了SARA四组分在不同甲苯含量的重质油中的扩散系数,分析了甲苯添加量对重质油中SARA四组分相互作用的影响规律,研究了沥青质分子和TJU-3破乳剂分子在油水界面的运移过程。结果表明：重质油的黏度降低到1500mPa·s时,可实现在1h内完全破乳;黏度降低到50mPa·s时可实现在20min内完全破乳。当破乳剂在乳液中的浓度为400mg/L时,乳液的脱水率最高;破乳温度为60℃时,破乳速度最快。SARA四组分中胶质的扩散系数增大最显著,是重质油的黏度能被甲苯迅速降低的主要原因。TJU-3分子能够破坏沥青质界面膜,进而实现破乳。该协同机制和工艺条件可为石油工业中重质W...     

延长油区低渗透油藏提高采收率技术对策

针对延长油田开发中存在的储层物性差,自然产能低;裂缝多,油井水淹严重;地层压力低,生产压差难以保证;注水启动压力高,注水效果差等主要问题,提出了加强储层研究、加强成熟技术推广应用、开展提高采收率方法适应性及潜力评价研究等提高采收率途径和对策。     

Application of the dual-drop dual-crystal contact angle technique to characterize heavy oil reservoir wettability

Reservoir wettability characterization is often important for planning and predicting depletion strategies, including primary and enhanced recovery schemes. This paper compares wettability evaluations in terms of water-advancing contact angles measured using the recentlydeveloped 'dual-drop-dual-crystal (DDDC)' technique with the traditional 'modified sessile drop' procedure. The DDDC technique was found to be a more reliable method for the Elk Point crudeoil/brine/rock systems. The DDDC experimental procedure is less time consuming because this technique achieves rapid adsorption equilibrium between two crude oil drops and two crystal surfaces. Moreover, it is reproducible as it is designed to overcome the difficulties commonly associated with the traditional contact angle methods. On the basis of the DDDC contact angle experiments, it was concluded that both the Lindbergh and Frog Lake Cummings heavy oil reservoirs of the Elk Point field exhibited intermediate wettability near the native reservoir conditions (characteristic of primary depletion). The water-advancing contact angles for the crude-oil/brine/quartz systems (near the reservoir conditions of 4400 kPa and 28°C) were determined to be 92 and 90° for Lindbergh and Frog Lake systems, respectively. These angles were reproducible within 1°. This reproducibility is the result of meticulous application of wateradvancing contact angle definition by means of a procedure that recognizes the effects of adhesion and buoyancy and allows shifting of the lower crystal so that the brine advances over an area that was previously exposed to crude oil. In addition, a careful monitoring of three-phase (oil/water/solid) contact line movements ensures conformance to the definition of water-advancing contact angle as demonstrated in this paper.     

From Phase Behavior to Understand the Dominant Mechanism of Alkali-Surfactant-Polymer Flooding in Enhancing Heavy Oil Recovery

The primary objective of this work was to understand the dominant mechanism(s) of alkali‐surfactant‐polymer (ASP) flooding in enhancing heavy oil recovery. Chemical formulations were first optimized based on phase behavior studies. The data indicated that alkali and surfactant created a synergistic effect at the oil/water interface, which further decreased the interfacial tension (IFT) and improved the emulsification. However, it was also found that the addition of alkali was detrimental to the viscous properties of the chemical systems and caused the ultimate oil recovery to decrease. In other words, the macroscopic sweep efficiency as a result of viscosity was the primary factor determining the overall recovery of heavy oil followed by emulsification, which was verified by the phase behavior of the effluent. Based on the experimental results, we found that for this targeted heavy oil reservoir, surfactant‐polymer (SP) flooding was more appropriate than ASP flooding and it was not necessary to decrease the IFT to the ultralow level (10^?3 mN/m) using alkali. Through chemical flooding, the incremental oil recovery was increased up to 27% of original oil in place, indicating the potential of this technique in heavy oil reservoirs.     

CO_2辅助蒸汽驱驱油效率实验研究

稠油开发是世界性的大难题。在中国能源紧缺的今天,稠油资源无疑是中国不可忽视的能源之一。传统的稠油开采方法采用的是单一注蒸汽的热力开采方式,但单一的注蒸汽会带来很多的问题,如汽窜、产量递减过快等问题。随着稠油开采技术的进步,发现在蒸汽中加入CO_2会改善注汽效果。本文进行了CO_2辅助蒸汽驱驱油进行了室内研究,通过改变CO_2与蒸汽的注入比、注入段塞的大小、注入速度来确定最优的注入参数。     

单家寺稠油油藏不稳定汽驱数值模拟技术研究

在单家寺稠油油藏开采过程中,暴露出了油井吞吐轮次多,开发效果差,汽窜现象严重等问题。通过利用成熟的数模软件对井组进行数值模拟,根据现场生产动态分析蒸汽吞吐阶段的汽窜规律,研究单家寺稠油油藏不稳定蒸汽驱的机理,认清不稳定蒸汽驱参数的影响规律,确定了各参数之间的相互关系,并根据正交实验法对参数进行了优化。研究表明不稳定蒸汽驱能有效改善特稠油油藏多轮次吞．吐后期的开发效果,是蒸汽吞吐开采提高采收率的一种新途径,同时进行了不稳定蒸汽驱的配套工艺的研究,为大规模推广不稳定蒸汽驱提供了先决条件。     

Microfluidic study of surfactant flooding of heavy oil in layered porous media containing fractures

Surfactant injection is a promising method for enhanced oil recovery (EOR) due to its effective micro-displacement mechanisms. However, understanding the interaction of a surfactant solution with heavy oil in porous media is neither straightforward nor well understood, particularly in heterogeneous systems. By enabling in-situ real-time monitoring of flow transport, microfluidic studies have provided novel insights into the underlying multiphase physics of flow at the pore scale. This paper examines the two-phase displacement efficiency of a new surfactant in layered–fractured porous microfluidic patterns, a topic seldom discussed in the literature. To evaluate the performance of the proposed surfactant, we considered several heterogeneous media with varying layer and fracture geometrical characteristics, quantifying displacement efficiency for each case. Based on the analysis of pore-scale snapshots, it was inferred that the primary mechanisms responsible for EOR during surfactant flooding into heavy oil include pore wall transportation, emulsifications, the deformation of residual oil, inter-pore or intra-pore bridging, and wettability alteration. Macroscopic displacement experiments revealed that the width of the swept area from surfactant injection significantly exceeded that of water injection, resulting in a substantially higher oil recovery. Furthermore, it was demonstrated that the direction of fluid flow in relation to fracture orientation plays a critical role in the dynamics of surfactant solution movement and, consequently, the ultimate oil production.