Enhanced Oil Recovery Techniques Research Articles

An experimental study of alternative hot water alternating gas injection in a fractured model

Alternative injection of gas as slugs with water slugs, or alternative water gas injection, is the conventional technique for improving the recovery factor due to its high potential for mobilizing the residual oil in place in the reservoirs and to control gas mobility. The water alternating gas methodology is a combination of two oil recovery procedures: gas injection and waterflooding. The principal parameters that must be evaluated in water alternating gas injection in laboratory scale are reservoir heterogeneity, rock type, and fluid properties. In the current investigation, a feasibility study has been performed to analyze the five various scenarios of enhanced oil recovery techniques and compare them experimentally. The laboratory experiments are done for one of the Iranian reservoirs which have been subjected to waterflooding for several years, and the amount of recovery factor for water flooding is about 42%. The results of this study illustrate that water alternating gas injection and hot water alternating gas injection exert a profound impact on the amount of recovery factor. Moreover, the primary purpose of this study is to assess the application of alternative hot water and hot carbon dioxide gas injections in the conventional and fractured reservoir model.

Plenty of Room at the Bottom: Nanotechnology as Solution to an Old Issue in Enhanced Oil Recovery

During the past half-century, the prefix “nano” attached to several words, such as “technology”, “motors”, “device”, and so on has denoted cutting-edge research fields and topics at the forefront of classical scientific disciplines. Possible application fields have been frequently evoked, even if real-life examples are still difficult to find. The present review analyzes how nanotechnology is utilized in enhanced oil recovery (EOR) processes so as to increase the efficiency of mature oilfields. Nanotechnology in EOR is classified into three categories: nanoparticles/nanofluids, nanoemulsions, and nanocatalysts. The advantages at the nanoscale are also described and discussed, including an overview of manufacturing methods as well as the concerns about their possible environmental impacts. Clearly, nanotechnology has the potential to boost EOR techniques, although there are still many questions and drawbacks to be tackled.

Experimental study on lateral flooding for enhanced oil recovery in bottom-water reservoir with high water cut

The regular enhanced oil recovery (EOR) methods in bottom-water reservoir aim to increase the vertical sweep efficiency. After multicycle chemical injection, the injected slug cannot effectively control the bottom water coning in the presence of fully developed water channel, decreasing the sweep efficiency and lowering economic efficiency. To improve the development effect of bottom-water reservoir, lateral flooding is proposed as a more cost-effective EOR technique by displacing the oil formation horizontally. In this study, three lateral flooding tests were performed in a three-dimensional physical model based on the geometric similarity criterion. Bottom-water reservoirs were simulated by sandpacking oil and water formations according to the parameters of the target oil reservoir. The bottom-water energy was supplied by an ISCO constant pressure, and the lateral flooding was conducted by an ISCO constant rate pumps. The oil recovery, water cut, pressure drop, and saturation variation maps obtained from these tests were recorded and analyzed. A comparison of these results between different crosslinked polymer slug tests shows that the improved oil recovery by lateral waterflooding can be mainly attributed to a significant increase in horizontal sweep efficiency. After 0.3 PV crosslinked polymer injection, about two-thirds of that was used to shut off the main water channels; the chemical packer, formed by the surplus polymer spreading along the oil/water interface under the drive of lateral injection, can inhibit bottom water from coning into the oil formation and prevent the crossflow. The 0.2, 0.3, and 0.4 PV crosslinked polymer injection can increase oil recovery by as much as 11.35, 36.23, and 39.74% of the original oil-in-place (OOIP), respectively. This confirms that lateral flooding is an efficient EOR method in bottom-water reservoir.

Stimulated-based characterization recovery enhancement feedback of oil-rim reservoirs

ABSTRACTOil-rim reservoirs are a kind of such unconventional reservoirs which the oil layer was occupied by the gas cap and aquifer layer. Regarding the economic prosperity of drilling this reservoir types, petroleum engineers would always try to find novelistic enhanced oil recovery techniques to produce more oil volume which economically profitable owing to the vast experiences of drilling and production operations are. However, oil-rim reservoirs production would be a particular challenge due to its unique characterization for several decades, in this comprehensive study, we try to simulate six different scenarios with drilling new wells horizontally or vertically on the oil recovery enhancement and choose the optimum technique which has more compatibility with the reservoir characteristics. Moreover, another objective of this study is to investigate the dominant influence of simulation procedures in each scenario on the critical parameters of gas oil ratio, water cut and, pressure drop. Consequently, scenario six regarding the drilling of a horizontal well and its potential contact with the reservoir has been the best scenario among other scenarios and scenario four and five due to the drilling new vertical wells have witnessed an excellent economical choice for commencing the production operation.

Identification of Nanocellulose Retention Characteristics in Porous Media.

The application of nanotechnology to the petroleum industry has sparked recent interest in increasing oil recovery, while reducing environmental impact. Nanocellulose is an emerging nanoparticle that is derived from trees or waste stream from wood and fiber industries. Thus, it is taken from a renewable and sustainable source, and could therefore serve as a good alternative to current Enhanced Oil Recovery (EOR) technologies. However, before nanocellulose can be applied as an EOR technique, further understanding of its transport behavior and retention in porous media is required. The research documented in this paper examines retention mechanisms that occur during nanocellulose transport. In a series of experiments, nanocellulose particles dispersed in brine were injected into sandpacks and Berea sandstone cores. The resulting retention and permeability reduction were measured. The experimental parameters that were varied include sand grain size, nanocellulose type, salinity, and flow rate. Under low salinity conditions, the dominant retention mechanism was adsorption and when salinity was increased, the dominant retention mechanism shifted towards log-jamming. Retention and permeability reduction increased as grain size decreased, which results from increased straining of nanocellulose aggregates. In addition, each type of nanocellulose was found to have significantly different transport properties. Experiments with Berea sandstone cores indicate that some pore volume was inaccessible to the nanocellulose. As a general trend, the larger the size of aggregates in bulk solution, the greater the observed retention and permeability reduction. Salinity was found to be the most important parameter affecting transport. Increased salinity caused additional aggregation, which led to increased straining and filter cake formation. Higher flow rates were found to reduce retention and permeability reduction. Increased velocity was accompanied by an increase in shear, which is believed to promote breakdown of nanocellulose aggregates.

Interfacial and Colloidal Forces Governing Oil Droplet Displacement: Implications for Enhanced Oil Recovery

Growing oil demand and the gradual depletion of conventional oil reserves by primary extraction has highlighted the need for enhanced oil recovery techniques to increase the potential of existing reservoirs and facilitate the recovery of more complex unconventional oils. This paper describes the interfacial and colloidal forces governing oil film displacement from solid surfaces. Direct contact of oil with the reservoir rock transforms the solid surface from a water-wet to neutrally-wet and oil-wet as a result of the deposition of polar components of the crude oil, with lower oil recovery from oil-wet reservoirs. To enhance oil recovery, chemicals can be added to the injection water to modify the oil-water interfacial tension and solid-oil-water three-phase contact angle. In the presence of certain surfactants and nanoparticles, a ruptured oil film will dewet to a new equilibrium contact angle, reducing the work of adhesion to detach an oil droplet from the solid surface. Dynamics of contact-line displacement are considered and the effect of surface active agents on enhancing oil displacement discussed. The paper is intended to provide an overview of the interfacial and colloidal forces controlling the process of oil film displacement and droplet detachment for enhanced oil recovery. A comprehensive summary of chemicals tested is provided.

Theories and practices of carbonate reservoirs development in China

Abstract Carbonate reservoirs in China have the characteristics of diversified accumulation pattern, complex structure and varying reservoir conditions. Concerning these characteristics, this article tracks the technical breakthroughs and related practices since the 1950s, summarizes the developed theory and technologies of carbonate reservoir development, analyzes their adaptability and problems, and proposes their development trend. The following theory and technologies have come into being: (1) carbonate reservoir formation mechanisms and compound flow mechanisms in complex medium; (2) reservoir identification and description technologies based on geophysics and discrete fracture-vuggy modeling method; (3) well testing analysis technology and numerical simulation method of coupling free flow and porous media flow; (4) enhanced oil recovery techniques for nitrogen single well huff and puff, and water flooding development techniques with well pattern design in spatial structure, changed intensity water injection, water plugging and channel blocking as the core; (5) drilling and completion techniques, acid fracturing techniques and its production increasing techniques. To realize the efficient development of carbonate oil and gas reservoirs, researches in four aspects need to be done: (1) complex reservoir description technology with higher accuracy; (2) various enhanced oil recovery techniques; (3) improving the drilling method and acid fracturing method for ultra-deep carbonate reservoir and significantly cutting engineering cost; (4) strengthening the technological integration of information, big data, cloud computation, and artificial intelligence in oilfield development to realize the smart development of oilfield.

Simultaneous feasible injectivity of foam and hydrolyzed polyacrylamide to optimize the oil recovery enhancement

Foam flooding is considered as one of the beneficial chemical enhanced oil recovery techniques to increase the value of gas viscosity and thereby, the efficiency of the produced oil would be improved dramatically rather than other methodologies. The objective of this extensive study is to determine a suitable injectivity model for one of the heterogeneous sandstone reservoir in which hydrolyzed polyacrylamide concentration in the solution foam has the most recovery factor. To do this, the results of laboratory investigation and simulation analysis are taken into consideration in different injectivity scenarios to obtain the more efficient scenario. Consequently, higher concentration of hydrolyzed polyacrylamide in the foaming agent, the high volume of oil has been produced after 10 years of producing. Furthermore, by selecting three cores from the three wells in this field, it is clarified that, owing to the increasing the volume of foam in the injectivity fluid, the pressure drop increased dramatically and subsequently has leaded to produced more oil volume.

Feasibility of spontaneous ignition during air injection in light oil reservoirs

Air injection in light oil reservoirs is a complicated EOR (enhanced oil recovery) technique. Till now, the mechanisms of HPAI (high pressure air injection) are still under controversy. Some researchers state that the heat generation is not important for the recovery of light oil during HPAI, and consider the LTO (low temperature oxidation) is only to remove the oxygen but not to establish the combustion front, while others claim that the spontaneous ignition and sustainable combustion front are the key aspects for a success HPAI project. The experimental trials on spontaneous ignition of HPAI to light oil are reviewed and discussed in this paper. This paper also investigates the spontaneous ignition feasibility through both analytical method and numerical method. The review shows that the combustion tube test is used to study combustion sustainability but not suitable to study the spontaneous ignition, and the thermal experiments can only be applied as screening tool to select favorable oil for HPAI in terms of feasibility of spontaneous ignition while further core flooding tests are still required. This paper also proposes an approach which associates thermal experiments with numerical simulation method to investigate the spontaneous ignition of a light oil. A case study is performed with a Wolfcamp light oil, the simulation study shows that the LTO of this light oil cannot induce spontaneous ignition during air injection in both core flooding experiment and field application. The analytical approach is very sensitive to the kinetic data which is used to estimate the ignition delay time. As a result, the analytical method may be misleading in terms of the feasibility of spontaneous ignition, if inappropriate data are selected.

A Study on continuous and intermittent THAI™ processes in Brazil's Northeastern Region

ABSTRACTToe-to-Heel Air Injection – THAI™ is an enhanced oil recovery technique that employs in situ combustion combined with technologies for horizontal well drilling, which is unprecedented in Brazilian oilfields. Motivated by this context, this research is intended to studying the application of the THAI™ process in a semisynthetic reservoir, with characteristics similar to those found in Brazil's Northeastern region. At the end, it was demonstrated that the intermittent air injection increased the oil recovery, when compared to the continuous injection, what reinforce the need for further research turned to ongoing and future projects in mature oilfields.

An enhanced oil recovery technique by targeted delivery ASP flooding

Abstract Aiming at the problem of the loss of the ASP flooding near the injection wells, this paper gives a new idea to enhance oil recovery called “Technique of Targeted Delivery”, which combines the radial horizontal well with ultra-short radius drilled by high pressure water jet with the ASP flooding, the horizontal wells work as the “Target channel” transport the ternary composite system to the remaining oil enrichment area directly, to avoid the loss of the ternary composite system near the injection wells. The plate homogeneous experiment and numerical simulation show that the technique can significantly improve the sweep efficiency and the effect of the oil displacement, and greatly improve the oil recovery rate. The optimal flooding parameters of the target transport technique are: the right angle target, the length of the channel is about 15% of the well distance and the injection volume of the ternary composite system is 0.4 PV. Under such conditions, this technique can enhance recovery by 48.87% and 22.04% respectively, compared with the water flooding and conventional ASP flooding. The target transport technique solves the problem of high loss of chemical agent in near-wellbore area during the ASP flooding, and compensates for the high cost of ASP flooding and the limitation of application, and has a broad application prospect.

Synthesis and Characterization of Microencapsulated Bacteria for Application in Enhanced Oil Recovery Technique

Synthesis and Characterization of Microencapsulated Bacteria for Application in Enhanced Oil Recovery Technique

Application of different EOR techniques for the energy and recovery of Ashal’cha oil field

ABSTRACTIn this research, utilizing the reservoir and produced oil data, different enhanced oil recovery (EOR) techniques known as in-situ combustion, CO2 flooding, and steam flooding were applied for Ashal’cha oil field in Republic of Tatarstan, Russia. For this purpose, In-Situ Combustion Predictive Model (ICPM), CO2 Miscible Flood Predictive Model (CO2PM) and Steam-flood Predictive Model (SFPM) are used. In addition to oil recovery, economic analysis of the discussed EOR applications was also conducted. By using the oil price forecast for 10 years, each EOR method is analyzed using their expenses and outcomes separately. Comparison among the EOR applications regarding the oil production, and economic feasibility was also given. Taking the reservoir and produced oil characteristics, oil production rate and economical payout time into account, it was observed that in-situ combustion is the most feasible and practical EOR method for Ashal’cha oil field.

Simulation of kinetic behavior of natural surfactants adsorption using a new robust approach

AbstractSurfactant‐based enhanced oil recovery techniques are known as promising methods for mobilizing the trapped oil in porous media. Surfactants can improve oil recovery by modifying the wettability of rock minerals and also by reducing the interfacial tension between injected water and the trapped oil. Natural surfactants have been introduced as good candidates for enhanced oil recovery applications. In addition, they are less expensive and also have less detrimental environmental effects in comparison with the industrial surfactants. Various empirical models have been proposed for simulating the kinetic behavior of surfactants adsorption, but these models suffer from overestimation and underestimation and they cannot be generalized for even a type of surfactant. Therefore, it is crucial to develop a new model that can overcome these issues. In this study, a new simple, rapid, and accurate model based on least square support vector machines (LSSVMs) was developed for predicting the kinetic adsorption density of natural surfactants on both sandstone and carbonate minerals. Coupled simulated annealing algorithm (CSA) is used for tuning the parameters of the model. Predicted values by this model were in an excellent agreement with experimental values with a coefficient of determination of 0.990. The results demonstrated that the proposed LSSVM‐CSA model has the best performance in comparison with the other well‐established kinetic models. Furthermore, the model reliability was investigated over input parameters changes and showed the acceptable efficiency of the proposed model.

Enhanced oil recovery by nitrogen and carbon dioxide injection followed by low salinity water flooding for tight carbonate reservoir: experimental approach

Enhanced Oil Recovery techniques are one of the top priorities of technology development in petroleum industries nowadays due to the increase in demand for oil and gas which cannot be equalized by the primary production or secondary production methods. The main function of EOR process is to displace oil to the production wells by the injection of different fluids to supplement the natural energy present in the reservoir. Moreover, these injecting fluids can also help in the alterations of the properties of the reservoir like lowering the IFTs, wettability alteration, a change in pH value, emulsion formation, clay migration and oil viscosity reduction. The objective of this experiment is to investigate the residual oil recovery by combining the effects of gas injection followed by low salinity water injection for low permeability reservoirs. This is done by a series of flooding tests on selected tight carbonate core samples taken from Zakuum oil field in Abu Dhabi by using firstly low salinity water as the base case and nitrogen & CO2injection followed by low salinity water flooding at reservoir conditions of pressure and temperature. The experimental results revealed that a significant improvement of the oil recovery is achieved by the nitrogen injection followed by the low salinity water flooding with a recovery factor of approximately 24% of the residual oil.

Importance of Well Completion Methods and Enhanced Oil Recovery Techniques in Oil and Gas Industry Operations

Importance of Well Completion Methods and Enhanced Oil Recovery Techniques in Oil and Gas Industry Operations

A computational framework for immiscible three-phase flow in deformable porous media

Several soil decontamination processes and enhanced oil recovery techniques involve the co-existence of three immiscible fluids, such as water, a nonaqueous phase liquid and a gas. In this work, a computational framework based on the individual mass balance of each phase is developed, aimed at simulating three-phase flow in a deformable rock through the finite element method, without resorting to specific simplifications that are usually required by standard numerical schemes. Key ingredients of the model are: expression of the residual in terms of mass contents, consistent lumping of the storage terms in the residual and algorithmic (tangent) matrix, consistent integration rules, the use of a minimum relative permeability and a time marching scheme based on trapezoidal integration. Special convective boundary conditions are adopted for pressures to be consistent with the assumed rock wettability properties during co-current imbibition. The resulting numerical scheme can deal with arbitrary saturation and/or pressure boundary conditions. The model is tested by simulating gas injection tests, and both co- and counter-current water imbibition tests, in a deformable core. To assess the performance and robustness of the whole framework, sensitivity analyses are performed upon varying key constitutive, loading and numerical parameters.

Adsorption of natural surfactants on sandstone rocks: Effect on the quality of the recovered asphaltenic oil

ABSTRACTNatural surfactants are important for any enhancing oil recovery applications since these kinds of surfactants have less detrimental effects and also lower cost in comparison to the industrial surfactants. Adsorption of surfactants on sandstone minerals is an important issue which needs to be considered before applying any surfactant-based enhanced oil recovery technique. In this study, a new model based on adaptive neuro-fuzzy interference system was developed in order to simulate the kinetic behavior of natural surfactants adsorption on sandstone minerals with high accuracy. Performance of the model was investigated by comparing the results of the proposed model with the results of previous well-known kinetic models. Results demonstrated that this model has the highest accuracy compared to the other well-established models found in literature. Finally, in order to show the importance of modeling surfactants adsorption, the effect of a natural surfactant on the quality of the produced oil was investigated by performing SARA analysis on the recovered oil at various conditions of surfactant adsorption. It is shown that in the case of lower surfactant adsorption on sandstone minerals, the produced oil has higher asphaltene fractions.

Wettability Alteration of Mineral Surface during Low-Salinity Water Flooding: Role of Salt Type, Pure Alkanes, and Model Oils Containing Polar Components

Low-salinity water injection is an emerging enhanced oil recovery technique and an area of active research. According to many researchers, the role of brine salinity has been attributed to its ability to change the reservoir rock wettability. The influence of different parameters such as total dissolved solids, concentration of individual ions, oil composition, lithology, acid and base number, etc., has been tested previously using different combinations of crude oil and reservoir core samples. However, because of the complex nature of crude oil–brine–rock system, there is no clear idea of the mechanism of wettability alteration and the influence of above parameters on this process. In this work, we have investigated the governing factors affecting the wettability of mineral surface using pure alkane liquids and model oils (containing organic acid and base). The wettability studies were performed through contact angle measurements over a wide range of concentration (1 mM to 1M) of monovalent and divalent ...

Interpretation of interwell tracer tests using discrete fracture model

Well-to-well tracer tests are used for getting knowledge about the flow behavior in the reservoir. The results of interpretation of these tests are especially important when enhanced oil recovery techniques that use expensive fluids such as surfactants, micellar fluids, or polymers are modeled. The classical method of quantitative interpretation assumes that the tracer filtration channels are completely isolated from the formation. In this paper, an alternative method for interpreting the results of well-to-well tracer tests is proposed. High-permeability channels are represented as discrete fractures that connect producing and injection wells. A numerical solution of the convective transport equation is used for modeling the tracer flow. The flows between the fracture and the reservoir are fully resolved, so the above-described drawback of the classical technique is overcome. The interpretation is carried out by constructing a reservoir model and determining the model parameters by solving the inverse problem. The model is verified, the well-posedness of the inverse problem is analyzed, and the comparison of the method with the classical interpretation method is performed. Using two fractures as an example, it is shown that the quasi-solution of the inverse problem exists and continuously depends on the input data. The interpretation results with this method are shown to be similar to the results of the classical interpretation in the absence of crossflows between the fracture and the reservoir. It was found that the presence of crossflows can increase the estimated fracture volume by 200 or more times. It is also shown that the crossflows between the fracture and the formation can completely prevent water breakthrough along the fracture into the production well.