Application of Fuzzy C-means algorithm as a novel approach to predict solubility of hydrocarbons in carbon dioxide

In the recent years, declination of oil reservoir causes the importance of researches on enhancement of oil recovery processes become more important. One of wide applicable approaches in enhancement of oil recovery is carbon dioxide injection which becomes interested because of relative low cost, good displacement and environmentally aspects. The injection of carbon dioxide to oil reservoir causes the lighter hydrocarbons of crude oil are extracted by CO₂. This phenomena can be affected by various factors such the solubility of hydrocarbons in carbon dioxide so in the present investigation Fuzzy c-means (FCM) as a novel approach for estimation of solubility of alkanes in carbon dioxide in terms of temperature, pressure and carbon number of alkane were utilized. The predicting algorithm FCM has reliable ability to estimate solubility based on graphical and statistical results. The coefficient of determination (R²) for training and testing data are calculated as 0.9856 and 0.9529 respectively.     

Prediction of the interfacial tension between hydrocarbons and carbon dioxide

In the recent years due to increasing demand for energy and declination of reservoir production, an impressive notice on enhancement of oil recovery has been found. The gas injection especially carbon dioxide injection due to low cost and friendly environmentally of this approach the special attention to CO₂ injection increased. The miscibility is known as key factor which effects on enhancement of recovery. The miscibility is controlled by interfacial tension of hydrocarbons and carbon dioxide so the importance of investigation of the interfacial tension becomes highlighted.in this investigation by using radial basis function (RBF) artificial neural network (ANN) as a novel approach the interfacial tension of hydrocarbons and carbon dioxide in terms of pressure, temperature, liquid and gas densities and molecular weight of alkane. The graphical and statistical results illustrated the fact that RBF-ANN algorithm is applicable for estimation of interfacial tension between hydrocarbons and carbon dioxide with great accuracy.     

Utilization of Grid partitioning based Fuzzy inference system approach as a novel method to estimate solubility of hydrocarbons in carbon dioxide

Recently due to increasing demand for energy and declination of oil reservoir the researchers have been encouraged to investigate the enhancement of oil recovery (EOR) approaches. One of popular and wide applicable processes in EOR is carbon dioxide injection which is attractive for researchers and industries due to environmentally aspects, good efficiency in displacement and low cost. The carbon dioxide injection causes the hydrocarbons extracted from crude oil so the solubility of hydrocarbon in carbon dioxide which is one of the critical parameters affects this phenomenon becomes interesting topic for researchers. In the present work Grid partitioning based Fuzzy inference system approach as a new method for prediction of solubility of hydrocarbons in carbon dioxide as function of temperature, pressure and carbon number of alkane was applied. To show the accuracy of the model the coefficients of determination were determined as 0.9902 and 0.9584 for training and testing phases respectively.     

Rigorous modeling of solubility of normal alkanes in supercritical CO2

In this contribution, ANFIS approaches are developed for the prediction of normal alkane solubility in supercritical carbon dioxide. Regarding the economic and environmental benefits of carbon dioxide injection, it introduced as a well-known procedure of EOR. With this in mind that solubility of normal alkanes followed by CO₂ injection affected by various operational condition, in this article functionality of solubility of normal alkanes in supercritical carbon dioxide from operational condition was investigated using Adaptive Neuro Fuzzy Interface System (ANFIS). Results demonstrate that the model is precise. The model shows an overall R² and AARD% estimations of 0.9921 and 0.89%, respectively.     

Simulation Study of Different Modes of Miscible Carbon Dioxide Flooding

Carbon dioxide flooding has been applied worldwide as a successful enhanced oil recovery. Carbon dioxide flooding may be applied as a continuous injection or as water-alternating-gas (WAG) process. Optimization of the injection mode of carbon dioxide is important for economical field application. This paper focuses on using a fully compositional simulation model for “AEB-3C” sandstone oil reservoir of one of the Western Desert oil fields in Egypt to predict the impact of CO₂ miscible flooding on the reservoir oil recovery and net present value (NPV), to define the best mode of operation that is straight CO₂ injection or water alternating gas (WAG) processes and to show the difference between pure and impure CO₂. Moreover, several sensitivity runs were done on the oil price to show minimum profitable value of oil price when applying such a tertiary method in the subject field.The reservoir under study has been producing under a successful water flooding project since May-2010. The recovery factor by the end of water flooding project is predicted as 32%. CO₂ flooding processes have started by the end of water flooding. A significant increase in the oil recovery factor was noticed due to applying this method; it reached up to 57%. Comparisons between different modes of operations were shown which showed better results when applying WAG process than that with straight CO₂ injection. Moreover; sensitivities were done on the cycle periods in WAG processes and showed increase in the recovery factor with shortening the cycle periods. In addition to a comparison between pure and impure CO₂ which showed very close results.     

Application of ANFIS-GA as a novel and accurate tool for estimation of interfacial tension of carbon dioxide and hydrocarbon

In the recent years, the enhancement oil recovery processes become the one of the interesting topics in petroleum engineering because of declination of oil reservoirs. One of the most popular processes is the carbon dioxide injection that has special importance because of its environmentally friendly and high efficiency of displacement. The interfacial tension (IFT) between carbon dioxide and hydrocarbon is known as a key parameter in this process so in the present investigation the Adaptive neuro-fuzzy inference system (ANFIS) was coupled with Genetic Algorithm (GA) to create a novel tool for prediction IFT between carbon dioxide and hydrocarbon in terms of temperature, pressure, molecular weight of alkane, gas and liquid densities. The outputs of predicting model were compared with experimental IFT statistically and graphically. The comparisons showed that predicting model has acceptable accuracy in prediction of IFT of hydrocarbon and carbon dioxide.     

Evaluation of miscible and immiscible CO2 injection in one of the Iranian oil fields

Carbon dioxide (CO₂) flooding is one of the most important methods for enhanced oil recovery (EOR) because it not only increases oil recovery efficiency but also causes a reduction of greenhouse gas emissions. It is a very complex system, involving phase behavior that could increase the recovery of oil by means of swelling, evaporation and decreasing viscosity of the oil. In this study, a reservoir modeling approach was used to evaluate immiscible and miscible CO₂ flooding in a fractured oil field. To reduce simulation time, we grouped fluid components into 10 pseudo-components. The 3-parameter, Peng–Robinson Equation of State (EOS) was used to match PVT experimental data by using the PVTi software. A one-dimensional slim-tube model was defined using ECLIPSE 300 software to determine the minimum miscibility pressure (MMP) for injection of CO₂. We used FloGrid software for making a reservoir static model and the reservoir model was calibrated using manual and assisted history matching methods. Then various scenarios of natural depletion, immiscible and miscible CO₂ injection have been simulated by ECLIPSE 300 software and then the simulation results of scenarios have been compared. Investigation of simulation results shows that the oil recovery factor in miscible CO₂ injection scenario is more than other methods.     

A laboratory investigation of carbon dioxide-enhanced oil recovery by focusing on CO2-oil physical properties

Carbon dioxide (CO₂) miscible flooding has become an important method in enhanced oil recovery (EOR) for recovering residual oil. In addition it may help in protection of the environment as (CO₂) is widely viewed as an important agent in global warming. Knowledge of the interactions between (CO₂) and reservoir crude oil is very critical for any (CO₂)-enhanced oil recovery (EOR) projects. This paper shows the effect of (CO₂) miscible flooding application for Egyptian oil fields by swelling studies. The swelling test is a laboratory simulation of the process of injecting gradually different percentage of (CO₂) gas into a reservoir containing under-saturated oil. The gas (injection solvent) can dissolve, causing the reservoir fluid to swell. This paper presents a summary of a wide range of laboratory tests conducted on ten different crude oils varying from 26.4 to 40.5 API. These were used to invested the use of (CO₂) and its effect on parameters such as viscosity, density, gas solubility and swelling factor as a function of pressure at temperature from 620.3 to 706.0?°R.     

The Experimental Investigation of Nitrogen and Carbon Dioxide Water-alternating-gas Injection in a Carbonate Reservoir

Abstract

Floods were conducted using rock–fluid systems consisting of carbonate cores from Binak reservoir, which is located in southwest of Iran, oil and brine. The coreflood protocol consisted of a series of steps including brine saturation, absolute permeability determination, flooding with oil to initial oil saturation, endpoint oil permeability determination, and, finally, nitrogen and carbon dioxide water-alternating-gas (WAG) injections. The effect of slug size on oil recovery was investigated using immiscible nitrogen (N₂) WAG injection and the amount of oil recovered was compared with continuous injection of N₂. Experimental results show that ultimate oil recovery is not very sensitive to changing the slug sizes for N₂ WAG injection, although the slug size of 0.15 pore volume (PV) injection is better than others. As less PV is injected, a higher oil production rate is achieved. Also, N₂ WAG flood appeared to be better in performance than continuous gas injection (CGI) of nitrogen. Carbon dioxide (CO₂) injection was performed in three modes, including CGI, WAG injection, and hybrid WAG. Experimental results show that for optimization of oil recovery in CO₂ floods, a continuous gas slug of 0.4–0.5 PV followed by 1:1 WAG needs to be injected.     

Application of Grid partitioning based Fuzzy inference system method as a novel approach for prediction of interfacial tension of hydrocarbon and carbon dioxide

Nowadays the importance of enhanced oil recovery (EOR) processes increases because of increasing demand of energy and declination of oil reservoirs. Due to this fact the researchers attracted to study performance of EOR methods. one of the high efficient methods is carbon dioxide injection which is favorable because of low cost and environmental friendly viewpoints. One of important parameters which have straight effect on recovery of injection is interfacial tension between carbon dioxide and hydrocarbons. In the present investigation the main objective is proposing the Grid partitioning based Fuzzy inference system method as novel approach to predict interfacial tension of carbon dioxide and hydrocarbon in terms of temperature, pressure, liquid and gas densities and molecular weight of alkane. The coefficients of determination for different datasets of training and testing of estimating algorithm are determined as 0.9919 and 0.9899. This results express the algorithm has potential of estimating interfacial tension of hydrocarbons and carbon dioxide.     

Black Oil and Compositional Reservoir Simulation for Increasing the Recovery Performance of an Iranian Fractured Carbonate Reservoir

Abstract

Naturally fractured reservoirs contain a significant amount of world oil reserves. Accurate and efficient reservoir simulation of naturally fractured reservoirs is one of the most important, challenging, and computationally intensive problems in reservoir engineering. Black oil and compositional reservoir simulators have been used to determine the reservoir management and production strategies to increase the oil recovery from a low-porosity, low-permeability fractured carbonate reservoir, with an average matrix permeability of 0.8 md, average fracture permeability of 500 md, and an average matrix porosity of 10%. This reservoir is a candidate for an enhanced oil recovery (EOR) process, because the reservoir production rate has been declined due to increasing the water cut as a result of rising the water oil contact. The injection techniques that have been considered in this study for black oil model include (a) gas injection, (b) water injection, and (c) simultaneous water alternating gas injection and for the compositional model include (a) dry gas injection, (b) CO₂ injection, and (c) N₂ injection. Simulation results show that CO₂ injection has the maximum oil recovery between the EOR scenarios.     

SCREENING CRITERIA FOR CO2 STORAGE IN OIL RESERVOIRS

ABSTRACT

Oil fields are likely to the first category of geologic formation where carbon dioxide (CO₂) is injected for sequestration on a large scale, if geologic sequestration proves feasible. About 1.4 BCF per day (69 300 tonnes/day) of CO₂ are currently injected for oil recovery in the U.S. Replacing this naturally occurring CO₂ with anthropogenic CO₂ would have a minor, but measurable, effect on overall CO₂ emissions. However, CO₂ is injected into only a small fraction of reservoirs and it is estimated that upwards of 80% of oil reservoirs worldwide might be suitable for CO₂ injection based upon oil recovery criteria alone. These facts combined with the generally extensive geologic characterization of oil reservoirs and the maturity of CO₂–oil recovery technology make oil reservoirs attractive first targets as CO₂ sinks. This paper lays the groundwork necessary to evaluate whether an oil reservoir might be suitable for CO₂ storage. As such, a series of criteria for injection into currently producing, depleted, or inactive reservoirs are proposed. Aspects considered include the reservoir depth, storage capacity, water and oil volumes in place, formation thickness, and permeability. Importantly, the effect of oil production on reservoir properties, especially fault movement and induced fractures must be gauged and included in assessments. It is demonstrated that CO₂ density with depth alone is not a sufficient criterion for choosing candidate sites. It is necessary to consider also porosity and the amount of water and oil that are displaceable. The end result is a criteria table for rapid screening of candidate reservoirs.     

烃组分对CO2驱最小混相压力的影响

针对CO_2-EOR原油组分对混相能力影响的问题,应用界面张力消失法设计了不同碳数烃组分、不同族烃组分、不同含量烃组分混合模拟油与CO_2的最小混相压力实验,分析不同族烃组分与CO_2最小混相压力的变化规律,探寻原油中影响CO_2驱最小混相压力的关键组分。研究表明:原油中不同组分与CO_2的最小混相压力不同,相同碳数烃组分最小混相压力依次为:烷烃、环烷烃、芳香烃;同族烃的碳数越小,最小混相压力越小;相同碳数烃类的混合组分模拟油的最小混相压力小于单一烃组分的最小混相压力;原油中低碳数烷烃含量增加,最小混相压力降低,高碳数芳香烃含量增加,最小混相压力升高。该研究结果为多种类型油藏实施CO_2驱提高采收率提供了数据材料及理论支撑。     

A numerical simulation study of CO 2 injection for enhancing hydrocarbon recovery and sequestration in liquid-rich shales

Less than 10% of oil is usually recovered from liquid-rich shales and this leaves much room for improvement, while water injection into shale formation is virtually impossible because of the extremely low permeability of the formation matrix. Injecting carbon dioxide (CO₂) into oil shale formations can potentially improve oil recovery. Furthermore, the large surface area in organicrich shale could permanently store CO₂ without jeopardizing the formation integrity. This work is a mechanism study of evaluating the effectiveness of CO₂-enhanced oil shale recovery and shale formation CO₂ sequestration capacity using numerical simulation. Petrophysical and fluid properties similar to the Bakken Formation are used to set up the base model for simulation. Result shows that the CO₂ injection could increase the oil recovery factor from 7.4% to 53%. In addition, petrophysical characteristics such as in situ stress changes and presence of a natural fracture network in the shale formation are proven to have impacts on subsurface CO₂ flow. A response surface modeling approach was applied to investigate the interaction between parameters and generate a proxy model for optimizing oil recovery and CO₂ injectivity.     

Applying Fuzzy c-means approach as a novel method for prediction of interfacial tension between carbon dioxide and hydrocarbons

The worldwide demand for energy increases and also the price of crude oil increases so these reasons have been caused the searchers have motivated to investigate enhanced of oil recovery (EOR) processes. The carbon dioxide injection is recognized as one of the favorable approaches of EOR because of high displacement efficiency, environmentally aspects and lower cost. The Interfacial tension between crude oil and carbon dioxide is known as one of the critical factors which affect the performance of injection. The main objective of the present investigation is development of Fuzzy c-means (FCM) approach as novel method to estimate interfacial tension between carbon dioxide and hydrocarbons as function of pressure, temperature, liquid and gas densities and molecular weight of alkane. The performance of predicting model was evaluated statistically and graphically and the results confirmed the ability of the model to predict interfacial tension between carbon dioxide and hydrocarbons.     

延长油田致密砂岩油藏CO2驱油机理研究

CO_2驱是提高低渗透油田产量、缓解温室效应的有效途径。针对鄂尔多斯盆地油藏压力系数低、原油轻质组分含量高的特点,通过PVT和最小混相压力等测试分析方法,揭示了低压、低孔、低渗油藏CO_2驱提高采收率主要机理。开展了CO_2注入储层与无机、有机物作用后的沉淀研究,表明CO_2在无机盐溶液中不会形成沉淀堵塞孔隙,CO_2与有机质作用后沉积点高于油藏压力,且注入压力越高,CO_2在地层原油中的溶解能力越强,目标区块CO_2注入后不易形成沥青质沉淀。物模驱替实验结果表明,均质岩心的采出程度明显高于非均质岩心,且随着岩心非均质性的增加,水驱采出程度、气驱采出程度及最终采出程度均明显下降。     

A simulation approach in economic assessment and risk analysis of the CO2 miscible flooding process

Due to high cost and technical uncertainty of recovery processes, predictive models developed for CO₂ miscible flooding processes should be used to evaluate the production performance of projects. This study presents the reservoir simulation study and probabilistic cash flow analysis of CO₂ miscible flooding projects in West Virginia. An extended black oil reservoir simulator was used in this study. Historical data and information from a CO₂ injection pilot in Granny's Creek Field of Clay County in West Virginia were used. A history match was done, and then alterative matched cases were run, such as pure CO₂ injection and water-alternate-gas (WAG) injection. A PC-based probabilistic cash flow analysis (PCFA) model was developed to analze the economic evaluation of the CO₂ miscible flooding project on a popular spreadsheet.Statistical analysis of the results shows: (1) the WAG case is more profitable than the pure CO₂ injection case; (2) the pure CO₂ injection case and the WAG case are more economical than the base case. Therefore, given current oil prices, the CO₂ processes have a higher potential to succeed in tec technical aspects but not in economical aspects. This study initiates the adaptation of the model to specific parameters of West Virginia oil fields. The newly formulated microcomputer PCFA model overcomes some of the problems commonly found in the conventional Monte Carlo simulation. Thus, the simulation approach in economic assessment and risk analysis can be readily adopted in future projects.     

Compositional modeling and simulation of dimethyl ether (DME)- enhanced waterflood to investigate oil mobility improvement

Dimethyl ether (DME) is a widely used industrial compound, and Shell developed a chemical EOR technique called DME-enhanced waterflood (DEW). DME is applied as a miscible solvent for EOR application to enhance the performance of conventional waterflood. When DME is injected into the reservoir and contacts the oil, the first-contact miscibility process occurs, which leads to oil swelling and viscosity reduction. The reduction in oil density and viscosity improves oil mobility and reduces residual oil saturation, enhancing oil production. A numerical study based on compositional simulation has been developed to describe the phase behavior in the DEW model. An accurate compositional model is imperative because DME has a unique advantage of solubility in both oil and water. For DEW, oil recovery increased by 34% and 12% compared to conventional waterflood and CO₂ flood, respectively. Compositional modeling and simulation of the DEW process indicated the unique solubility effect of DME on EOR performance.     

Enhanced Natural Gas and Condensate Recovery by Carbon Dioxide and Methane Flooding

Abstract

The authors quantitatively investigates the recovery efficiency, pattern behavior, and relative permeability of (a) condensate following supercritical carbon dioxide (CO₂) injection, methane (CH₄) injection, and the injection of their mixtures; and (b) natural gas of various compositions following pure supercritical CO₂ injection. A high-pressure high-temperature experimental laboratory was established to simulate reservoir conditions and to perform relative permeability measurements on sandstone cores. This work is part of an integrated enhanced natural gas and condensate recovery project conducted for a local reservoir in Western Australia. This data will help the operators develop operational and design strategies for their present and future EOR projects.     

A Simulation Study of Carbon Dioxide Sequestration in a Depleted Oil Reservoir

Abstract

Oil fields offer significant potential for storing carbon dioxide (CO₂) and will most likely be the first large-scale geological targets for sequestration because the infrastructure, experience, and permitting procedures already exist. In addition, almost 40 years' experience in enhanced oil recovery (EOR) allows utilization of carbon capture and storage (CCS) and CO₂ sequestration techniques in such a way as to improve recovery of petroleum fields and reduce the environmental issue of fossil fuel combustion gas products, particularly carbon dioxide. Carbon dioxide is one of the main greenhouse gases that causes global warming.

As a response to global warming, geologic sequestration of CO₂ in oil and gas reservoirs is one possibility to reduce the amount of CO₂ released to the atmosphere. This simulation study presents a synthetic geologic model that is used to sequestrate carbon dioxide beside an EOR immiscible displacement process.