Modeling Of Enhanced Oil Recovery Research Articles

Technology Focus: EOR Modeling (January 2024)

The oil and gas industry is at a critical juncture in addressing the pressing need to balance operational efficiency with environmental stewardship. With the world’s growing emphasis on climate change and sustainability, the industry is tasked with the dual objectives of refining operational efficiency and simultaneously diminishing its carbon footprint. This balancing act has become a strategic imperative crucial for the long-term viability of the industry. In light of the recent COP28 agreement, which emphasizes a “swift, just, and equitable energy transition,” the role of low-emission enhanced oil recovery (EOR) and operational optimization becomes increasingly significant. This period of transition, which may span several decades, demands a pragmatic approach where the existing hydrocarbon resources are used as efficiently and responsibly as possible. In the quest to optimize operations and reduce carbon footprint, three innovative technical papers present a cohesive story of advancement through modeling and machine learning. These papers underscore the industry’s shift toward more efficient practices, each contributing a crucial piece to the larger puzzle of EOR.The first paper introduces an advanced modeling approach for fractured reservoirs, a significant development in tight rock simulations that simplifies fracture heterogeneity characterization and enhances computational efficiency, crucial for optimizing asset development decisions in shale and tight oil resources. Building on the theme of efficiency, the second paper pivots to the realm of surfactants, exploring their role in wettability alteration within unconventional liquid-rich reservoirs. This research provides a systematic approach for screening thermally stable surfactants under reservoir conditions, crucial for improving hydrocarbon recovery without unnecessary field trials. The final piece of this narrative is a study using machine learning to predict gas-injection parameters in EOR processes. This approach addresses the lack of extensive gas-injection laboratory data, demonstrating the power of data-driven predictions in enhancing operational efficiency and decision-making. These papers weave a compelling narrative of technological innovation, highlighting the role of advanced modeling and machine learning. As the oil and gas industry progresses in its vital mission to supply the world’s energy needs, the pivotal role of technology innovation becomes increasingly evident. Advanced technologies focused on operational optimization and reducing carbon emissions are essential in reinforcing the industry’s adaptability and resilience in the context of this rapidly evolving energy landscape. Recommended additional reading at OnePetro: www.onepetro.org. SPE 215083 An Analytical Tool to Predict Fracture Extension and Elastic Desaturation for Polymer Field Projects by M.B. Abdullah, The University of Texas at Austin, et al. SPE 216822 First Pilot Design of Low-Tension-Gas (LTG) Flooding in Carbonate Field in North Oman by Mohammed Al-Abri, Petroleum Development Oman, et al. SPE 213037 Field-Scale Multistage and Multiobjective Optimization of Rate and Concentration for Polymer Flooding by Ruxin Zhang, Texas A&M University, et al.

Technology Focus: EOR Modeling (January 2023)

The oil and gas industry is facing unprecedented responsibility and expectations to keep fueling the world’s economies and social developments with reliable, accessible, safe, and affordable energy sources while responding to the global urgency to safeguard natural resources and protect the environment. Most major oil and gas companies have announced decarbonization strategies for low-carbon or net-zero emissions associated with their business operations. Consequently, reducing the carbon intensity of oil production [kilograms of carbon dioxide (CO2) equivalent emitted per produced barrel of oil] will be pivotal to meeting the environmental mandate. On the other hand, approximately 70% of the world’s counties have set targets to reach net zero within the next 3–5 decades, including emissions from burned hydrocarbon, which is a major challenge. Within this exigent mission to transition the industry, a major question arises about the merit and the role of enhanced oil recovery (EOR). With a share below 3% of the global oil production, field-scale EOR deployment and contribution have been modest despite substantial investments made in research and development and piloting in the last 4 decades. This underperformance of EOR has been attributed mostly to competitive alternatives (waterflooding), high cost, complex infrastructure and supply chains, fluctuating oil prices, and others. In the era of thirst for sustainability in our industry, there are reviving opportunities for selective EOR methods that can achieve efficient oil production with low carbon intensity. For instance, CO2 EOR is intuitively a win/win technology. This method may not be feasible everywhere for various reasons, however, including the availability and proximity of CO2 sources and the suitability of reservoir conditions. Chemical EOR methods, such as low-salinity, polymer-, and surfactant-based methods with low chemical usages have the potential to reduce water usage and enhance recovery factors, particularly from tight oil reservoirs. In contrast, EOR methods that are inherently associated with high carbon intensity, such as thermal EOR, will face stricter constraints to perform, including prohibitive costs for carbon offsetting. Advanced modeling and optimization, including guided machine learning and data analytics, will be crucial to maximizing recovery, quantifying uncertainties, and managing risk while preserving resources and reducing costs. The selected papers in this feature include examples of innovative approaches for developing efficient EOR schemes and advanced modeling and optimization. In one inclusion, optimized water chemistry is engineered for various EOR schemes (e.g., polymer, surfactant, CO2) to improve efficiency while reducing chemical usage. The second inclusion demonstrates an integrated core-to-field work flow to design surfactant-based EOR for a tight formation at the laboratory scale and demonstrate its performance using field-scale simulations. An integrated optimization approach for a Permian CO2-EOR field is demonstrated in the third paper, where an advanced Bayesian framework is used to capture uncertainties. Our industry has consistently demonstrated resilience, adaptivity, and creativity. In the era of industry transition to low-carbon operations, opportunities exist for selective EOR methods to revive and contribute. Recommended additional reading at OnePetro: www.onepetro.org. SPE 208121 Polymer Injection To Unlock Bypassed Oil in a Giant Carbonate Reservoir: Bridging the Gap Between Laboratory and Large-Scale Polymer Project by Clement Fabbri, ADNOC, et al. SPE 208127 The World’s First Offshore Gravity-Assisted Simultaneous Water-Alternating-Gas EOR Full-Field Implementation by Ahmad Khanifar, Petronas, et al. SPE 207449 Numerical Optimization of Water-Alternating-Gas Injection in a Sandstone Field Using a Coupled Surface and Subsurface Model by Thaer I. Ismail, Khalifa University of Science and Technology, et al.

Technology Focus: EOR Modeling (January 2022)

No one will be surprised to learn of the reduction in the produced literature on enhanced oil recovery (EOR) this past year measured in terms of papers produced through various SPE forums. The constraints created by the COVID-19 pandemic have been unprecedented. More encouraging and noteworthy is the fact that, even in such hard times, the wheels of knowledge have kept turning. Statistics are important in knowing where the sharp minds of SPE members are investing their energies. Typically, this is also in proportion to what those members need. Hence, it is noteworthy that more than a fifth of the papers were about CO2-based EOR, indicating not only renewed interest but also the motivation for carbon capture, use, and storage. You will find CO2-based EOR represented in the recommended-reading papers by a paper that describes use of simple techniques to predict fieldwide behavior using the Pulser method. What’s more, old is new again. In an enhanced shale gas recovery technique, as summarized in this issue, you will recognize repurposing of a much-discussed coalbed-methane method from a couple of decades ago. CO2-EOR literature is closely followed by continued momentum in the area of data science (DS) and machine learning but with a perceptible degree of maturity in the types of application. As opposed to the “everything goes in the Wild West” approach of a couple of years ago, more and more researchers are realizing that a practical application of DS must respect the underlying fundamentals. No wonder, then, that we are seeing a gradual return of physics, though now strengthened with the power of DS. A good examples of this is found in a paper summarized here that presents data-driven approaches for waterfloods. The other two inclusions presented in this feature combine learnings from other areas to extend and strengthen the frontiers of EOR modeling—namely, a coupled geomechanical and wellbore model, and an elegant manner of simulating phase appearance/disappearance in thermal simulations in the recommended-reading papers. I hope this brief primer will not only bring you up to date with the trends in the EOR literature but also equip you with a good sense of emerging tools and their applications. Recommended additional reading at OnePetro: www.onepetro.org. SPE 200390 - Pulser Model: Updated Framework and Lessons Learned From Applications in Forecasting CO2 Flood Performance by Deepanshu Kumar, Occidental Petroleum, et al. SPE 203912 - Development of a Thermal Stability Method for Phase Appearance and Disappearance Handling in Thermal Compositional Simulators by Mohammad Reza Heidari, Schlumberger, et al.

Technology Focus: EOR Modeling (January 2021)

The enhanced-oil-recovery (EOR) literature produced in the past several months was dominated by reservoir modeling and characterization; flood enhancements; machine learning; and, more notably, relative permeability estimation. This last one needs to be under-stood further. Relative permeability characterizes flow in porous media, the understanding and manipulating of which is key to the success of EOR. Our fascination with the topic during the last 75 years, therefore, is understandable. Starting with a seminal paper from W.R. Purcell in 1949, we have more than 12,000 articles in the SPE collection alone on relative permeability estimation, of which more than 400 were published in the last year. Mechanics of motion is also important to mankind, but we do not have literature piling up on Newton’s laws of motion. Is it that we haven’t understood flow in porous media yet, or is it because the subject matter is so complex? The truth, perhaps, lies somewhere in between. Flow in pores that are randomly sized, randomly connected, and have variable chemical makeup is, by nature, complex and mathematically unmanageable. Relative permeability has been our attempt to lend its aggregate behavior some sense of manageability. This has always been done in a fit-for-purpose manner. What is fit for one context, however, may not be so for the others, and this uncertainty continues to churn out theses, antitheses, and syntheses. Expectedly, even more such activity arises with every improvement in computing capabilities, as is once again evident with advances in machine learning—new tools to handle old problems. That is where my first pick is for you, with some additional suggested readings in references that follow. Data analytics does much more than estimate relative permeability, and the second paper abridged here uses it to predict a flood performance. To allow a break from data science, the third paper chosen deals with the important topic of electromagnetics as applied to reservoir characterization and heating. I hope you find these to be useful and interesting reads.

Technology Focus: EOR Modeling (January 2020)

Technology Focus The bulk of the literature on enhanced oil recovery (EOR) from the past year has been devoted to an improved understanding of trends started more than a decade ago with physical and numerical modeling. A quick review of the basics will be helpful for putting these developments in perspective. The concept of displacement in an EOR method requires bringing the mobility ratio of displacing fluid to that of displaced oil under unity [Kw µ o / Ko µw less than 1; Ko, Kw being relative permeabilities of displaced oil and displacing fluid (e.g., water), respectively, and µ o, µw being their respective viscosities], and increasing sweep efficiency (Es) of the displacement process. Various established EOR methods try to accomplish this in different ways, depending on the formation and oil types, aiming to keep costs and environmental impact down while obtaining high and quick recovery. Thus, polymers or foams have been used traditionally to increase viscosity of displacing fluids (µw). To reduce Kw/Ko, surfactant; alkaline; microbes, which create in-situ surfactants; or low-salinity water, which changes wettability to water, were used. Steam or hot water have also been used to reduce both Kw and µo. Miscible gas or solvent displacements were used to attack µo. Quite frequently, a combination of these mechanisms has been applied, alkaline/surfactant/ polymer being a good example. Similarly, to address improvement in sweep, blocking agents such as polymers, microgels, or microbes, or a combination of a couple of these mechanisms, have been applied. While the underlying mechanisms remain the same, major developments in EOR in recent years center on the use of engineered water or nanoparticles to reduce Kw, on the experimental development of chemicals that are less susceptible to high-temperature and high-salinity environments, or on the use of novel computational techniques and machine learning to design and monitor the flood operations better. The literature of the last year is an important reflection of that evolution, as the selected papers reflect. Recommended additional reading at OnePetro: www.onepetro.org. SPE 195553 Investigation of Pore-Scale Mechanisms of Microbial Enhanced Oil Recovery Using Microfluidics by Calvin Gaol, Clausthal University of Technology, et al. SPE 192110 Polymers and Their Limits in Temperature, Salinity, and Hardness: Theory and Practice by Eric Delamaide, IFP Technologies Canada, et al. SPE 192651 Performance Evaluation and Field Trial of Self-Adaptive Microgel Flooding Technology by Zhe Sun, China National Offshore Oil Corporation, et al.

A complete workflow applied on an oil reservoir analogue to evaluate the ability of 4D seismics to anticipate the success of a chemical enhanced oil recovery process

In an Enhanced Oil Recovery (EOR) process, one of the main difficulties is to quickly evaluate if the injected chemical products actually improve oil recovery in the reservoir. The efficiency of the process can be monitored in the vicinity of wells, but it may take time to estimate it globally in the reservoir. The objective of this paper is to investigate the ability of 4D seismics to bridge this gap and to help predict the success or breakdown of a production strategy at reservoir scale. To that purpose, we consider a complete workflow for simulating realistic reservoir exploitation using chemical EOR and 4D seismic modeling. This workflow spans from geological description to seismic monitoring simulation and seismic attributes analysis, through geological and reservoir modeling. It is applied here on a realistic case study derived from an outcrop analog of turbiditic reservoirs, for which the efficiency of chemical EOR by polymer and surfactant injection is demonstrated. For this specific field monitoring application, the impact of both waterflooding and proposed EOR injection is visible on the computed seismics. However, EOR injection induces a more continuous water front that can be clearly visible on seismics. In this case, the EOR efficiency can thus be related to the continuity of the water front as seen on seismics. Nevertheless, in other cases, chemical EOR injections may have more moderate impacts, or the field properties may be less adapted to seismic monitoring. This points out the importance of the proposed workflow to check the relevance of seismic monitoring and to design the most adapted monitoring strategy. Numerous perspectives are proposed at the end of the paper. In particular, experts of the different disciplines involved in the proposed workflow can benefit from the availability of a complete set of well-controlled data of various types to test and improve their own tools. In contrast, the non-experts can easily and quickly benefit from “hands-on” experiments for understanding the involved phenomena. Furthermore, the proposed workflow can be directly applied to geological reservoirs all over the world.

Technology Focus: EOR Modeling (January 2019)

Technology Focus As far as I am concerned, 2018 became the year I dealt with some aspect of enhanced oil recovery (EOR) every week. I had noticed that, in recent years, interest in bringing EOR to field operations had been growing everywhere. As operators and asset owners worked continually to increase efficiency in oil production, they all realized that part of efficiency improvement is increasing recovery factors. Everybody now is extremely focused on recovering more from the reservoirs they have. Of course, limited exploration and maturing fields are some of the motives behind that new attitude. Additionally, oil price is at a point now that allows for EOR but is still too low for exploration. Global interest in implementing EOR had a clearly positive outcome on the quality of the technical papers reviewed this year. All EOR schemes were covered superbly, and discussions were well advanced. Along with new insights for conventional EOR schemes, emerging EOR schemes such as low-salinity waterflooding and EOR for unconventionals were deliberated extensively. Enhancements in understanding how each EOR system works, leading to improvements in EOR modeling and forecasting, certainly will make future EOR projects more successful. We should add the effect of ever-growing cloud computation and the Internet of Things to the anticipated success of new EOR projects. The effect of those enablers is going to benefit EOR projects in every way, from better project design to improved field management. Finally, we are able to construct reservoir models that include all EOR-relevant aspects of the reservoir in all scales. Along with that, the physics for almost all EOR schemes are captured in EOR forecasting models. Practically limitless computer access also will play a significant role in ensuring the success of EOR field management. Selecting only three papers among so many good ones was a difficult task. The following papers will give you some feeling about the noteworthy advancements happening in EOR performance and modeling. While you are focused on EOR, please consider checking out the other great papers listed as recommended additional reading. Recommended additional reading at OnePetro: www.onepetro.org. SPE 189785 A Parametric Study on the Applicability of Miscible-Gases-Based EOR Techniques in Unconventional Liquids-Rich Reservoirs by Dheiaa Alfarge, Iraqi Ministry of Oil, et al. SPE 190250 Systematically Optimized Surfactant Formulation and Injection Design To Reduce Chemicals While Maintaining Performance by Gayani W.P. Pinnawala Arachchilage, Chevron, et al. SPE 190305 Diffusion-Dominated Proxy Model for Solvent Injection in Ultratight Oil Reservoirs by M. Cronin, The Pennsylvania State University, et al. SPE 191474 Application of Artificial Intelligence for Mechanistic Modeling and Probabilistic Forecasting of Hybrid Low-Salinity Chemical Flooding by Cuong Dang, Computer Modelling Group, et al. SPE 191530 An Equation of State To Model Microemulsion-Phase Behavior in the Presence of Cosolvents Using Average-Solubilization Theory by Soumyadeep Ghosh, Chevron, et al.

Technology Focus: EOR Performance and Modeling (January 2018)

Technology Focus Efforts for increasing recovery factors in all reservoir types continued with increasing momentum during the past year. Maturing fields combined with limited exploration forced operators to focus on recovering more from existing fields. Implementing enhanced oil recovery (EOR) in a depressed-oil-price environment is accepted as a challenge by our resilient industry, and, therefore, all aspects of EOR, including EOR agents, EOR physics, and EOR modeling and monitoring, improved further. We saw progress in all EOR schemes in the past year, from expanding-solvent steam-assisted gravity drainage (SAGD) to increasing recovery factors in unconventional fields in the US. While carbon-dioxide EOR continues to be used in conventional reservoirs, it is also becoming a desired EOR agent for unconventionals. EOR implementations in high-viscosity-oil reservoirs continued to see improvements with more chemistry, with heat, with improved reservoir characterization, and with advancements in SAGD implementation. Progress in chemical EOR, from polymer to alkaline/surfactant/polymer, has been significant. Not only are there new chemicals with improved recovery capabilities, but also the cost of the chemicals is being reduced continuously. All those factors led to more operators using chemical EOR. It is worth reiterating that increasing recovery factors in unconventionals will remain the top priority for many years to come. The next chapter of the exciting unconventionals journey will be more about EOR. EOR momentum on all fronts is reflected in the technical papers reviewed this year. This is the first time I have seen that all EOR schemes were covered. Half the technical papers were about fundamentals, and the other half were about field implementation. I found that to be the best indicator that EOR is becoming an integral part of managing oil fields. The selected papers provide a summary of some of the noteworthy advancements in EOR performance and modeling. Recommended additional reading at OnePetro: www.onepetro.org. SPE 187032 Nanoscale-Flow-Chip Platform for Laboratory Evaluation of Enhanced-Oil-Recovery Materials by Michael Engel, IBM Research, et al. SPE 185526 Surveillance and Initial Results of an Existing Polymer Flood: A Case History From the Rayoso Formation by L.A. Martino, YPF, et al. SPE 183165 Borehole Controlled-Source Electromagnetics for Hydrocarbon-Saturation Monitoring in the Bockstedt Oil Field, Onshore Northwest Germany by K. Tietze, GFZ Potsdam, et al. SPE 182669 Uncertainty Quantification for Foam Flooding in Fractured Carbonate Reservoirs by A. Almaqbali, Heriot-Watt University, et al. SPE 185002 ES-SAGD Relative Permeability as a Function of Temperature and Solvent Concentrations by M. Zeidani, University of Calgary, et al.

Enhanced Oil Recovery in Liquid–Rich Shale Reservoirs: Laboratory to Field

Summary Production of tight oil from shale reservoirs in North America reduces oil imports and has better economics than natural gas. Currently, there is a strong interest in oil production from Bakken, Eagle Ford, Niobrara, and other tight formations. However, oil-recovery fraction for Bakken remains low, which is approximately 4–6% of the oil in place. Even with this low oil-recovery fraction, a recent United States Geological Survey study stated that the Bakken and Three Forks recoverable reserves are estimated to be 7.4 billion bbl; thus, a large volume of oil will remain unrecovered, which was the motivation to investigate the feasibility of enhanced oil recovery (EOR) in liquid-rich shale reservoirs such as Bakken. In this paper, we will present both laboratory and numerical modeling of EOR in Bakken cores by use of carbon dioxide (CO2), methane/ethane-solvent mixture (C1/C2), and nitrogen (N2). The laboratory experiments were conducted at the Energy and Environmental Research Center (EERC). The experiments recovered 90+% oil from several Middle Bakken cores and nearly 40% from Lower Bakken cores. To decipher the oil-recovery mechanisms in the experiments, a numerical compositional model was constructed to match laboratory-oil-recovery results. We concluded that solvent injection mobilizes matrix oil by miscible mixing and solvent extraction in a narrow region near the fracture/matrix interface, thus promoting countercurrent flow of oil from the matrix instead of oil displacement through the matrix. Specifically, compositional-modeling results indicate that the main oil-recovery mechanism is miscible oil extraction at the matrix/fracture interface region. However, the controlling factors include repressurization, oil swelling, viscosity and interfacial-tension (IFT) reduction, diffusion/advection mass transfer, and wettability alteration. We scaled up laboratory results to field applications by means of a compositional numerical model. For field applications, we resorted to the huff ’n’ puff protocol to assess the EOR potential for a North Dakota Middle Bakken well. We concluded that long soak times yield only a small amount of additional oil compared with short soak times, and reinjecting wet gas, composed of C1, C2, C3, and C4+, produces nearly as much oil as CO2 injection.

Technology Focus: EOR Performance and Modeling (January 2016)

Technology Focus Efforts to increase recovery factors in all types of oil reservoirs keep increasing, regardless of the fluctuations in oil prices. It is a historical fact that, when oil price drops, industry’s focus turns to produce/recover more oil where the oil is already found. In my career, this is the sixth oil-price crush I have seen, and the same behavioral change is happening again. The only difference between now and my first experience, in the 1980s, is that the need for enhanced-oil-recovery (EOR) applications today is a must, not a luxury. Luckily, activity in the world of EOR is continuing and for the better. Recovery-optimization efforts of the national oil companies are expanding with larger and well-designed EOR pilots and even with offshore chemical EOR projects. It is worth mentioning here that the EOR experience gathered by the international oil companies and service companies over the decades is definitely finding its way to provide a stable foundation to those new EOR projects. Additionally, new EOR projects are getting the benefit of the significant enhancements in reservoir characterization and evaluation, flow physics, EOR chemicals, modeling capabilities, conformance capabilities, and monitoring and control systems. All those are happening; therefore, it is safe to say the new EOR projects will be significantly more successful compared with the older ones from 1980s. Mitigating declining pressures in the 1970s and 1980s was basically handled by injection of water with simple vertical injectors with limited design. Now, companies think about low-salinity (LoSal) options every time pressure maintenance with water is considered. Alternatively, companies can design reliable water-alternating- gas (WAG) -injection schemes by placing the right-trajectory wells in the right locations of heterogeneous reservoir systems, which were already illuminated sufficiently with advanced reservoir characterization. Placing in-situ sensors and digital feedback mechanisms enables companies to optimize the new recovery process significantly. To start with, instead of just going with pressure maintenance, smart EOR screening systems that might have already been used may be more promising EOR options. Accessibility to fast EOR pilots suitable for the heterogeneity of the reservoir could be used, and the decision for field expansion takes place much faster and more reliably than it did in the 1980s. More-reliable modeling capabilities, coupled with cloud computing, are providing an environment in which refining EOR decisions in the presence of the uncertainties of the reservoirs is now possible. Limited design capability, smaller number of field tests, and lack of monitoring and control were the reasons most EOR projects did not perform in the past. All those issues are history now. Over the last year, irrespective of the inclement times in our industry, fundamental sciences, EOR physics, numerical modeling, monitoring and controlling capabilities, and EOR chemicals all demonstrated advancements. Ironically, fast exploitation of the unconventional liquids is considered to be one of the key reasons for the drop in oil prices; there are efforts to identify EOR potential for those reservoirs. The efforts consist of advancements in reservoir characterization suitable to those unique reservoir systems, smarter fracturing fluids, and EOR pilots. As a result of the continuing momentum in EOR efforts, many excellent technical papers were developed and, once again, selecting only a few was rather difficult. The following pages provide some insights on how EOR is being tested for “tight/light” reservoirs, CO2/LoSal WAG experimentation, and giant-field EOR applications. JPT Recommended additional reading at OnePetro: www.onepetro.org. SPE 173322 A Four-Phase-Flow Model To Simulate Chemical EOR With Gas by Mohammad Lotfollahi, The University of Texas at Austin, et al. SPE 174648 Novel Visualization of Chemical EOR Flooding Using a Lab-on-a- Chip Setup Supported by an Extensive Rheological Characterization by J. Wegner, Clausthal University of Technology, et al. SPE 173205 Reduced-Order Models for Rapid EOR Simulation in Fractured Carbonate Reservoirs by S. Agada, Heriot-Watt University, et al.

Technology Focus: EOR Performance and Modeling (January 2015)

Technology Focus We can easily state that incorporating enhanced-recovery focus into field- management practices as early as possible is finally becoming the norm. No longer is enhanced oil recovery (EOR) something operators procrastinate about and not act on until the end of the life of a field. Growing recovery challenges of maturing fields definitely are one of the reasons for this historical change in focus. We should also acknowledge the effect of growing unconventional oil operations and, more importantly, their severe recovery challenges. Increasing recovery factors in tight, light reservoirs is one of the more prominent research topics in the oil industry in recent years. Last but not least, EOR is being implemented in offshore operations. This new paradigm—caring for production and recovery, optimizing production rates and recovery factors simultaneously—is being realized with significant help from new technologies. Significant enhancements in reservoir characterization, EOR chemicals, modeling capabilities (EOR software and computational power), conformance capabilities, and monitoring and control systems, along with improved understanding of flow physics, are making EOR easier for our industry. Ongoing EOR research is bringing complex EOR schemes to the industry; some of the examples are low-salinity CO2 water-alternating-gas (WAG) injection, CO2/steam injection, steam/ solvent injection, and microbial EOR. Integration for successful EOR projects is also maturing. Historically, with steam-assisted gravity drainage, we all recognized the effect of well trajectory on recovery. More recently, we have identified the relationship between massive fracture architecture and EOR in tight, light reservoirs. It is worth mentioning that unconventionals have been pushing reservoir characterization, drilling, and completions to yet another level. All that effort not only improves the performance of those special reservoirs but also makes EOR easier for conventionals. As a result of the focus on enhancing recovery for all types of reservoirs, many great technical papers were available for this feature this year. The following pages will provide some insights into how EOR is being tested for tight, light reservoirs; into low-salinity CO2 WAG experimentation; and into giant-field EOR applications. More papers can be found in the OnePetro online library, including those listed for recommended additional reading. JPT Recommended additional reading at OnePetro: www.onepetro.org. SPE 169076 Modeling of Viscous Displacement in Dual-Porosity Naturally Fractured Reservoirs: Application to Surfactant Enhanced Oil Recovery by Mojtaba Kiani, Tiorco, et al. SPE 169170 Assessment of Three-Phase Relative Permeability and Hysteresis Models for Simulation of Water- Alternating-Gas Injection in Water- Wet and Mixed-Wet Systems by Omid Shahrokhi, Heriot-Watt University, et al. SPE 169102 Low-Salinity Waterflooding at West Salym: Laboratory Experiments and Field Forecasts by B.M.J.M. Suijkerbuijk, Shell, et al. OTC 24483 Relative Permeability Effects on the Miscible CO2 WAG Injection Schemes Through Compositional Simulations of Brazilian Small-Scale Water-Wet Synthetic Presalt Reservoir by S.F. Mello, Universidade Estadual de Campinas, et al.

Modeling of EOR in Shale Reservoirs Stimulated by Cyclic Gas Injection

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 169069, ’Compositional Modeling of EOR Process in Shale Oil Reservoirs Stimulated by Cyclic Gas Injection,’ by Tao Wan, Xingbang Meng, James J. Sheng, SPE, and Marshall Watson, SPE, Texas Tech University, prepared for the 2014 SPE Improved Oil Recovery Symposium, Tulsa, 12-16 April. The paper has not been peer reviewed. Cyclic gas injection combined with modern technologies such as horizontal drilling and hydraulic fracturing has achieved promising results in low-permeability formations. This paper focuses on the effects of injected-gas composition and fracture properties on oil recovery, concluding that cyclic gas injection in hydraulically fractured shale oil reservoirs is feasible for improving oil production substantially over primary production. Introduction Cyclic gas injection is an effective and quick-responding enhanced-oil-recovery (EOR) method in intensely naturally fractured or hydraulically fractured reservoirs. The short payout is a characteristic that should attract industry’s interest in investing in these types of projects. Recent studies showed that cyclic gas injection could be a viable method to improve the oil recovery in shale oil reservoirs, but those studies were performed on the basis of black-oil models without detailed analysis of the phase behavior of the reservoir-oil/injected-gas system. The reliability of using the blackoil model to simulate the cycling of gas/ condensate reservoirs is questionable because the two-component description may not be able to represent the active compositional phenomena adequately. This paper describes the use of an equation-of-state (EOS) approach to model the phase behavior of the oil and injected-solvent system. Description of Models The reservoir-fluid-composition data are from the published data of the fifth SPE comparative solution project, which aimed to illustrate the comparison of results between a four-component black-oil miscible-flood simulator and a fully compositional reservoir-simulation model. Minimum-Miscibility-Pressure (MMP) Determination Local displacement efficiency by gas or solvent injection is closely dependent on the MMP. Most gas- or solvent-injection cases operate in a regime in which true miscibility is not achieved; however, high recoveries still could be attained. The analytical method for MMP determination focused on finding the key crossover tie-lines for a dispersion- free displacement when one of the key tie lines becomes a critical-tie line (a tie-line of zero length). This paper shows the use of a cell-to-cell simulation method to determine the MMP of the given solvent composition and reservoir fluids. The pseudoternary diagram is generated from the calculations to study the vaporization or extraction process and interprets MMP as 3,440 psi. The multiple-contact miscibility occurs at approximately 3,400 psi, and a very small increase in recovery is observed at higher pressures. A slimtube simulation model also was developed that has good agreement with the MMP calculated by the tie-line method.

Technology Focus: EOR Performance and Modeling (January 2014)

Technology Focus This is the most exciting time for enhanced oil recovery (EOR) in recent memory. At last, almost everyone is talking about increasing recovery factors, and improved oil recovery (IOR) and EOR are being considered natural components of reservoir management. Furthermore, many traditional philosophies are being openly challenged. EOR planning is happening as part of field-development plans. Proven technologies are being adapted in new, smart ways, and new technologies are constantly evolving from research to commercial applications, making EOR projects more economical. These new directions are the result of the following factors: Most fields, including the giant ones, are maturing, and producing liquid hydrocarbons is becoming more difficult in all types of reservoirs (conventional and unconventional). Leaving approximately 70% of the in-place reserves unrecovered has been challenged. There have been developments on many fronts (e.g., advanced reservoir characterization, multiphase-flow physics, smart-well and intelligent completions, recovery research, monitoring and control technologies, EOR chemicals, EOR pilot concepts, and observation-well concepts); the collective effect of all of those is going to make new EOR projects more successful. Increasing recovery factors has been considered a fully integrated multidomain activity (from pore space to separator and everything in between). Severe production decline in tight/light (unconventional) reservoirs is making the industry think about recovery challenges. EOR has been considered during field-development planning in most recent offshore oil developments. We lived through the most active period of EOR—between the mid-1970s and the mid-1980s—and learned about recovery fundamentals then. However, if we look back at that era carefully, most of the wells were single and vertical; reservoir characterization was very elementary, with no digital geological modeling capabilities; and there were no concepts such as monitoring systems or intelligent completions. All of those factors created a significant gap between what was planned in the EOR laboratory and what was achieved in field application. Other than those implemented in extremely viscous oils (heavy-oil EOR operations), projects recovered far less than planned. Overall, such recovery gave a stigma to EOR as inherently difficult and expensive. Most of the factors that made EOR difficult and expensive are gone today. That is why we will see more fields using EOR operations in upcoming years. Broadening the scope of recovery challenge to all domains will make realizations of new reserves more likely, but this change will bring additional challenges. Recommended additional reading at OnePetro: www.onepetro.org. SPE 162701 Geomechanics Considerations in Enhanced Oil Recovery by Tadesse Weldu Teklu, Colorado School of Mines, et al. SPE 166597 BP North Sea Miscible Gas Injection Projects Review by Pinggang Zhang, BP, et al. IPTC 17157 The Development of a Workflow To Improve Predictive Capability of Low-Salinity Response by B.M.J.M. Suijkerbuijk, Shell, et al. SPE 166075 The Upscaling of Discrete Fracture Models for Faster, Coarse-Scale Simulations of IOR and EOR Processes for Fractured Reservoirs by Mun-Hong Hui, Chevron, et al.

Technology Focus: EOR Performance and Modeling (January 2012)

Technology Focus In spite of continued investment and advances in exploiting alternative-energy sources, oil and natural gas will continue to be a significant portion of US and global energy portfolios for decades. Enhanced oil recovery (EOR) uses unconventional hydrocarbon-recovery methods that target the approximately two-thirds of the oil volume remaining in reservoirs after conventional-recovery methods have been exhausted. Though limited by high capital and operating costs, EOR techniques will have a substantial effect on the future supply of oil. In 2011, SPE hosted an EOR conference in Kuala Lumpur, and three workshops to address EOR technologies in Malaysia, Kuwait, and the Syrian Arab Republic. The Malaysia workshop focused on chemical-EOR methods, the Kuwait workshop addressed opportunities and for challenges of EOR methods in the Middle East, and the Syrian Arab Republic workshop discussed EOR in carbonate reservoirs. More than 300 EOR papers were published in SPE conferences, with many additional presentations in EOR workshops. These papers address important issues related to practical application of conventional EOR methods and the development of novel EOR technologies. The topics cover experience with, opportunities for, and challenges of EOR technologies; fundamental study of EOR mechanisms for different methods; feasibility study and improvement of an EOR method for a specific reservoir; EOR-screening criteria; reservoir surveillance, monitoring, and evaluation technologies; reservoir simulation and modeling; lessons learned from EOR pilot and field trials; and some novel EOR methods. Polymer flooding has been proved the most cost-effective chemical-EOR method in the laboratory and in the field. A recent focus on polymer flooding evaluated associative polymers because of their advantage over traditional hydrolyzed polyacrylamide (HPAM) polymers; thus, one paper about comparing the flow behavior of associative polymer and HPAM in porous media was selected for this feature. CO2 injection is a win/win strategy because it can enhance oil recovery and be used for CO2 storage in reservoirs to reduce greenhouse-gas levels in the atmosphere. However, CO2 EOR targets maximum oil recovery while CO2 sequestration targets maximum storage capacity without leakage. One paper featured here provides some guidance to balance the two technologies. Steamflooding has been applied successfully in heavy-oil reservoirs. However, one paper synopsized in this feature will describe successful steamflooding in a light-oil reservoir. Recommended additional reading at OnePetro: www.onepetro.org. SPE 142668 Enhanced Waterflood for Middle East Carbonate Cores—Impact of Injection-Water Composition. By Robin Gupta, ExxonMobil Upstream Research, et al. SPE 142105 A Simplified Model for Simulations of Alkaline/Surfactant/Polymer Floods. By Mojdeh Delshad, SPE, University of Texas at Austin, et al. SPE 144294 Large-Scale High-Viscous-Elastic-Fluid Flooding in the Field Achieves High Recoveries. By Wang Demin, SPE, Daqing Oil Company, et al. \ SPE 144599 A Combined Experimental and Simulation Workflow To Improve Predictability of In-Situ Combustion. By M. Bazargan, Stanford University, et al. SPE 147858 In-situ Combustion Using Sugar Dust, ‘Sweet Reservoirs’—A Smart and Better Alternative by Panchamlal, SPE, Maharashtra Institute of Technology, et al. SPE 147999 Lessons Learned From Nine Years of Immiscible-Gas-Injection Performance and Sector-Modeling Study of Two Pilots in a Heterogeneous Carbonate Reservoir by Lakshi Konwar, SPE, Zakum Development Company, et al.

Technology Focus: EOR Performance and Modeling (January 2011)

Technology Focus SPE hosted two enhanced-oil-recovery (EOR) conferences in 2010: One was the 2010 SPE Improved Oil Recovery Symposium in Tulsa and the other was the 2010 SPE EOR Conference at Oil & Gas West Asia, Muscat, Oman. Many other SPE conferences had sessions on EOR technologies. Therefore, it is not surprising that more than 350 papers were presented on the topic in the past year. These papers covered past field-application experiences and accomplishments, current strides, and future directions. As in previous years, when I selected papers to highlight EOR this year, I classified the papers into the categories of gas injection, chemical methods, thermal methods, conformance control, microbial EOR, carbonate-reservoir EOR, reservoir-problem-identification technologies, and novel EOR methods such as low-salinity waterflooding and nanoparticles for EOR. However, it was still quite difficult to select only four to highlight from so many outstanding papers. In the past few EOR features, I highlighted chemical methods, CO2 EOR and sequestration, low-salinity waterflooding, particle gel for conformance control, wettability alteration, and methods to identify reservoir channels. Even though those topics are still quite important and many new ideas and information were presented this year, I decided to give preference to topics not highlighted before and to papers that comprehensively summarize field experiences. Overall, the leading-edge EOR technologies presented in SPE meetings this past year will be applied increasingly on a global scale and will increase the oil recovery of mature oil fields significantly as the technologies mature. EOR Performance and Modeling additional reading available at OnePetro: www.onepetro.org SPE 133089 • “Rock/Fluid Characterization for Miscible-CO2 Injection: Residual-Oil Zone, Seminole Field, Permian Basin” by M.M. Honarpour, SPE, Hess Corporation, et al. SPE 129899 • “Potential for Polymer Flooding Reservoirs With Viscous Oils” by R.S. Seright, SPE, New Mexico Petroleum Recovery Research Center. See SPE Res Eval & Eng, August 2010, page 730. SPE 132487 • “Air Injection in Heavy-Oil Reservoirs—A Process Whose Time Has Come (Again)” by M.G. Ursenbach, SPE, University of Calgary, et al. See J Can Pet Technol, January 2010, page 48. SPE 129925 • “Nanoparticle-Stabilized Supercritical CO2 Foams for Potential Mobility-Control Applications” by David Espinosa, SPE, University of Texas at Austin, et al. SPE 129692 • “Demonstration of Low-Salinity EOR at Interwell Scale, Endicott Field, Alaska” by Jim Seccombe, SPE, BP plc, et al. SPE 139667 • “Tertiary Oil Recovery and CO2 Sequestration by Carbonated-Water Injection” by N.I. Kechut, SPE, Heriot-Watt University, et al. SPE 132359 • “Identifying Injector/Producer Relationships in Waterflood Using Hybrid Constrained Nonlinear Optimization” by H. Lee, University of Southern California, et al.

Technology Focus: EOR Performance and Modeling (January 2010)

Technology Focus The demand for oil continues to grow, and it is forecasted that oil will continue to dominate the world share of energy supply for the next 3 decades. Accordingly, new discoveries tend to decrease on an annual base, and enhanced oil recovery (EOR) has the potential to reclassify unrecoverable and contingent reserves. EOR is viable because there are many available mature technologies, its implementation usually does not require drilling and completion cost, and most of the existing infrastructure can be used. When I selected the EOR papers to highlight this year, I classified the papers into the categories of gas injection, chemical methods, thermal methods, conformance control, microbial EOR, carbonate-reservoir EOR, reservoir-problem-identification technologies, and novel EOR methods including low-salinity waterflooding, imbibition EOR, alkaline/surfactant/gas injection, and CO2-miscible combined with alkaline/surfactant/polymer injection. Not surprisingly, CO2 EOR and polymer floods have drawn great interest this last year because CO2 sequestration has been a great interest to the community and polymer flooding is a proven cost-effective chemical-EOR method. The published polymer papers cover mainly the topics of thermal-stability evaluation of different polymers, novel polymer-flooding modeling, polymer-rheology database, and the formation effects on polymer properties. The CO2 publications discussed mainly the feasibility-evaluation results of CO2-EOR projects in different oil fields worldwide. An EOR project is not just a matter of injecting materials, with many factors affecting whether the project is successful. The design and implementation of an EOR project require a systematic integration from a multidisciplinary team. It is critically important to identify the problems of mature oil fields for a successful EOR project, and, thus, the papers to identify channels in mature oil fields were included in this EOR feature. EOR Performance and Modeling additional reading available at OnePetro: www.onepetro.org SPE 121460 • “Stability of Partially Hydrolyzed Polyacrylamides at Elevated Temperatures in the Absence of Divalent Cations” by R.S. Seright, SPE, New Mexico Institute of Mining and Technology, et al. SPE 123971 • “Streamline-Based Simulation of Non-Newtonian-Polymer Flooding” by Abdulkareem M. AlSofi, SPE, Imperial College—London, et al. SPE 123930 • “Identification and Characterization of High-Conductive Layers in Waterfloods” by C.S. Kabir, SPE, Hess, et al. SPE 124930 • “Mechanistic Modeling of Emulsion Formation and Heat Transfer During the Steam-Assisted Gravity-Drainage (SAGD) Process” by Prince N. Azom, University of Texas at Austin, et al. SPE 124946 • “Pore-Level Mechanics of Forced and Spontaneous Imbibition of Aqueous Surfactant Solutions in Fractured Porous Media” by Amar J. Alshehri, SPE, Stanford University, et al.

Technology Focus: EOR Operations (June 2009)

Technology Focus Welcome to the Enhanced Oil Recovery (EOR) Operations feature. This past year provided stimulating and rewarding times for all involved with EOR technologies. The interest in EOR technologies is higher than ever, despite the current fall in global crude-oil prices, which, by the way, is believed to be temporary by most analysts. This amplified attention in the EOR area results from the decrease of new discoveries and the ever-increasing number of maturing fields worldwide. It is expected that many EOR projects planned in the recent past will be implemented in the coming years. Thus, it is fundamental to revisit the lessons learned from previous EOR applications and to pay attention to the development of new techniques. Regarding technical publications, this past year alone, more than 300 SPE papers related to EOR were presented at various SPE events. As a result, the EOR feature is divided this year: EOR Performance and Modeling published in January and EOR Operations published in this issue. The papers featured here will give you only a few examples of the immense amount of high-quality material that was published last year. I hope that you enjoy reading these paper highlights and that you will search for additional interesting contributions that are available in the SPE eLibrary (OnePetro as of 1 July 2009). IPTC 11613 • "Blending Optimization of Contaminated Gas in a Miscible Gasflood" by J.T. van Berkel, SPE, Shell International E&P, et al.