Download or read book INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS written by and published by . This book was released on 2003 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the work performed during the second year of the project, ''Investigating of Efficiency Improvements during CO2 Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO2 flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling the fluid flow in fracture surface, examining the fluid transfer mechanisms and describing the fracture aperture distribution under different overburden pressure using X-ray CT scanner.

Download or read book Performance Evaluation of CO2 EOR in Tight Oil Formation with Complex Fracture Geometries written by Pável Zuloaga Molero and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent development of tight oil reservoirs has led to an increase in oil production in the past several years due to the progress in horizontal drilling and hydraulic fracturing. However, the oil recovery factor expected is still very low even after the wells have been fractured and therefore, tight formations are considered good candidates for enhanced oil recovery (EOR). One of the most suitable solutions to improve the oil recovery is the carbon dioxide (CO2)-based EOR. Although the injection of CO2 is not new for conventional oil reservoirs, its practice in tight oil formations is still a relatively novel idea. Two injection-production strategies are often employed: continuous CO2 injection or flooding and CO2 Huff-n-Puff. However, it is not clear which scenario is the best strategy to achieve an optimal recovery, which highly depends on many uncertain reservoir and fracture parameters and it is not clearly understood until recently. Another challenge of the estimation of the incremental recovery of these injection approaches is to properly model the hydraulic fractures and CO2 transport mechanism. The actual hydraulic fracturing process often creates complex fracture networks, especially when the fracture propagates in a formation with a large amount of pre-existing natural fractures. In this study, the CO2-EOR effectiveness is simulated and analyzed by comparing the Huff-n-Puff and the continuous injection scenarios. The effect of matrix permeability on the comparison of well performance of these two scenarios was investigated. Subsequently, Design of Experiment and Response Surface Methodology is used to perform sensitivity studies with four uncertain parameters including matrix permeability, number of wells, well pattern, and fracture half-length to determine the best injection approach. In addition, an efficient methodology of embedded discrete fracture model (EDFM) is introduced to explicitly model complex fracture geometries. The effects of complex fracture geometries on well performance of CO2 Huff-n-Puff and CO2 continuous injection were also investigated as well as the effect of natural fractures. The analysis of the CO2-EOR effectiveness confirms that the appropriate modelling of the complex fractures geometry plays a critical role in estimation of the incremental oil recovery. This study provides new insights into a better understanding of the impacts of reservoir permeability, complex hydraulic fractures and natural fractures on well performance during CO2-EOR process in tight oil reservoirs and in the determination and design of the optimal injection-production scheme to maximize the oil recovery factor for multi-fractured horizontal wells.

Download or read book Improved Efficiency of Miscible CO2 Floods and Enhanced Prospects for CO2 Flooding Heterogeneous Reservoirs Final Report April 17 1991 May 31 1997 written by and published by . This book was released on 1998 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: From 1986 to 1996, oil recovery in the US by gas injection increased almost threefold, to 300,000 bbl/day. Carbon dioxide (CO2) injection projects make up three-quarters of the 191,139 bbl/day production increase. This document reports experimental and modeling research in three areas that is increasing the number of reservoirs in which CO2 can profitably enhance oil recovery: (1) foams for selective mobility reduction (SMR) in heterogeneous reservoirs, (2) reduction of the amount of CO2 required in CO2 floods, and (3) low interfacial tension (97) processes and the possibility of CO2 flooding in naturally fractured reservoirs. CO2 injection under miscible conditions can effectively displace oil, but due to differences in density and viscosity the mobility of CO2 is higher than either oil or water. High CO2 mobility causes injection gas to finger through a reservoir, causing such problems as early gas breakthrough, high gas production rates, excessive injection gas recycling, and bypassing of much of the reservoir oil. These adverse effects are exacerbated by increased reservoir heterogeneity, reaching an extreme in naturally fractured reservoirs. Thus, many highly heterogeneous reservoirs have not been considered for CO2 injection or have had disappointing recoveries. One example is the heterogeneous Spraberry trend in west Texas, where only 10% of its ten billion barrels of original oil in place (OOIP) are recoverable by conventional methods. CO2 mobility can be reduced by injecting water (brine) alternated with CO2 (WAG) and then further reduced by adding foaming agents-surfactants. In Task 1, we studied a unique foam property, selective mobility reduction (SMR), that effectively reduces the effects of reservoir heterogeneity. Selective mobility reduction creates a more uniform displacement by decreasing CO2 mobility in higher permeability zones more than in lower permeability zones.

Download or read book CO2 Injection in the Network of Carbonate Fractures written by J. Carlos de Dios and published by Springer Nature. This book was released on 2020-12-17 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents guidelines for the design, operation and monitoring of CO2 injection in fractured carbonates, with low permeability in the rock matrix, for geological storage in permanent trapping. CO2 migration is dominated by fractures in formations where the hydrodynamic and geochemical effects induced by the injection play a key role influencing the reservoir behavior. CO2 injection in these rocks shows specific characteristics that are different to injection in porous media, as the results from several research studies worldwide reveal. All aspects of a project of this type are discussed in this text, from the drilling to the injection, as well as support works like well logging, laboratory and field tests, modeling, and risk assessment. Examples are provided, lesson learned is detailed, and conclusions are drawn. This work is derived from the experience of international research teams and particularly from that gained during the design, construction and operation of Hontomín Technology Development Plant. Hontomín research pilot is currently the only active onshore injection site in the European Union, operated by Fundación Ciudad de la Energía-CIUDEN F.S.P. and recognized by the European Parliament as a key test facility. The authors provide guidelines and tools to enable readers to find solutions to their problems. The book covers activities relevant to a wide range of practitioners involved in reservoir exploration, modeling, site operation and monitoring. Fluid injection in fractured media shows specific features that are different than injection in porous media, influencing the reservoir behavior and defining conditions for safe and efficient operation. Therefore, this book is also useful to professionals working on oil & gas, hydrogeology and geothermal projects, and in general for those whose work is related to activities using fluid injection in the ground.

Download or read book Improved Efficiency of Miscible CO2 Floods and Enhanced Prospects for CO2 Flooding Heterogeneous Reservoirs Annual Report June 1 1997 May 31 1998 written by and published by . This book was released on 1998 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this project is to improve the efficiency of miscible CO2 floods and enhance the prospects for flooding heterogeneous reservoirs. This report provides results of the first year of the three-year project that will be exploring three principle areas: (1) Fluid and matrix interactions (understanding the problems): interfacial tension (IFT), phase behavior, miscibility, capillary number, injectivity, wettability, and gravity drainage; (2) Conformance control/sweep efficiency (solving the problems): reduction of mobility using foam, diversion by selective mobility reduction (SMR) using foam, improved injectivity, alternating water and gas injection, and using horizontal wells; and (3) Reservoir simulation for improved oil recovery (predicting results): gravity drainage, SMR, CO2-foam flooding, interfacial tension, injectivity profile, horizontal wells, and naturally fractured reservoirs. Studies of surfactant foam quality were performed during this first year. Simulation studies on a foam pilot area resulted in an acceptable history match model. The results confirm that the communication path between the foam injection well and a production well had a strong impact on the production performance. A laboratory study to aid in the development of a gravity drainage reservoir was undertaken on the Wellman Unit. Experiments were begun meant to duplicate situations of injectivity loss in WAG flooding and identify factors affecting the injectivity loss. The preliminary results indicate that for a given rock the injectivity loss depends on oil saturation in the core during WAG flooding. The injectivity loss is higher in cores with high in-situ oil saturations during WAG flooding. This effect is being verified by more experimental data.

Download or read book Mobility Control of Gas Injection in Highly Heterogeneous and Naturally Fractured Reservoirs written by Jose Sergio de Araujo Cavalcante Filho and published by . This book was released on 2016 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since a significant portion of the world’s oil reserves resides in naturally fractured reservoirs (NFR), it is important to maximize oil production from these reservoirs. Mobility control EOR techniques, such as water alternating gas (WAG) and foam injection, may be used in NFRs to improve oil recovery. Foam injection may be modeled by empirical or mechanistic models, the latter being capable of representing foam generation and coalescence effects. Numerical models are needed to evaluate EOR techniques in NFR. The Embedded Discrete Fracture Model (EDFM) is capable of representing conductive faults or fractures and describing NFR and unconventional reservoirs as a triple porosity medium (hydraulic fractures, natural fractures, and matrix). This work aims at developing a general EDFM framework to allow the evaluation of different mobility control EOR methods in NFR. The mobility control EOR methods evaluated were the WAG and continuous foam injection. The formulation used to evaluate mobility control by foam injection in NFR was the population balance assuming local equilibrium and the P*c models. Nanoparticle transport models (Two Site and Two Rate models) were implemented and validated to allow simulation of nanoparticle stabilized foam injection. An EDFM preprocessor was further developed and validated against the in-house fully implicit simulator, unstructured grid models from the literature and fine-grid models using a commercial simulator. Simulation run time was reduced by applying a porosity cut-off in the fracture cells assuming constant fracture conductivity. Validation case studies included multi-fractured wells producing through depletion and a 2D quarter five-spot production scheme (water and miscible gas injection) in NFR. We obtained a good agreement between EDFM, unstructured grid, and fine-grid models. Application case studies included 3D models under water, miscible gas and WAG injection, which confirmed the efficiency of the EDFM in modeling complex fracture networks. We used the EDFM to simulate multilateral well stimulation and we performed an automated history matching of the production data of a field test. The foam model and the nanoparticle transport models were validated against experimental data from the literature. It is concluded that the effect of fractures on hydrocarbon production depends on fracture network connectivity, which may be modeled using the EDFM preprocessor. Simulation results using mobility control EOR methods show considerable improvements in oil recovery due to a postponement in gas breakthrough.

Download or read book Continuous CO2 Injection Design in Naturally Fractured Reservoirs Using Neural Network Based Proxy Models written by Hassan Hamam and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: More than 60% of the original oil in place (OOIP) is left in the ground after the primary and secondary recovery processes. With the introduction of enhanced oil recovery (EOR), that number goes down to about 40% of the OOIP. Carbon dioxide (CO2) injection is one of the most effective EOR methods in naturally fractured reservoirs. The fracture network provides a faster means for fluid flow due to its high conductivity but it is also the cause of premature breakthrough of the injected fluids. However, if employed efficiently, fractures can help push the injected CO2 to the reservoir boundaries so that a large portion of the reservoir fluid interacts with the injected CO2. Zones swept by miscible CO2 reported the lowest residual oil saturation.Continuous CO2 injection is becoming more and more preferred to the popular cyclic pressure pulsing. Continuous CO2 injection has no down time and could potentially provide better CO2 interaction with the reservoir fluid which provides a higher recovery. In this research, artificial neural networks (ANNs) are used to construct robust proxy models with highly predictive capabilities for naturally fractured reservoirs undergoing continuous CO2 injection. The main purpose of this research is to shed more light and understanding on continuous CO2 injection in naturally fractured reservoirs and provide a tool that empowers engineers to make decisions on the fly while evaluating uncertainty and mitigating risk rather than wait months or years to do so. In light of the above, various ANN designs and configurations undergo development and evolution to ultimately be able to provide valuable insights regarding reservoir performance, history matching, and injection design for naturally fractured reservoirs undergoing CO2 injection. Initial ANN designs targeted specific reservoirs using specific fluid compositions from the literature. The designed ANNs were able to provide predictions with a low degree of error. ANN designs went over many complex adjustments, variations, and enhancements until final configurations were reached. The final ANN designs developed in this research surpass previously developed ANNs in similar projects with its capability to handle a huge range of reservoir properties, relative permeability, capillary pressure, and fluid compositions under uncertainty.The reservoir simulation model used in this research is a two-well, two-layer, miscible compositional simulation model working in a dual-porosity system. Critical parameters affected the accuracy and predictability of the ANN designs and they were an essential part of the final ANN configurations. The parameters that a major effect on continuous CO2 injection are reservoir fluid composition, fracture permeability, well spacing, bottomhole flowing pressure (BHFP), thickness, and CO2 injection amount under miscible conditions had the highest impact on recovered oil.The final ANN designs were encompassed inside a graphical user interface that equipped the ANN with uncertainty evaluation capabilities. The ease to use nature of the GUI allows anyone to use the developed ANNs in this research, as well as provide a simple intuitive interface to manipulate input data, run simultaneous sensitivity and uncertainty analysis. The developed ANNs in this research bring us a step closer to achieving real-time simulation for naturally fractured reservoirs undergoing CO2 injection. The correlations embedded in the ANNs were able to overcome reservoir fluid, relative permeability, and capillary pressure limitations that existed in the previous ANN studies.

Download or read book Improved Efficiency of Miscible CO2 Floods and Enhanced Prospects for CO2 Flooding Heterogeneous Reservoirs Quarterly Technical Progress Report July 1 September 30 1995 written by and published by . This book was released on 1995 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this experimental research is to improve the effectiveness of CO2 flooding in heterogeneous reservoirs. Activities are being conducted in three closely related areas: (1) exploring further the applicability of selective mobility reduction (SMR) in the use of foam flooding, (2) exploring the possibility of higher economic viability of floods at slightly reduced CO2 injection pressures, and (3) taking advantage of gravitational forces during low interfacial tension (IFT), CO2 flooding in tight, vertically fractured reservoirs. Additional progress in task 1 has been made in the past quarter in both experimental and analytical directions. A new series assembly of two Berea cores has been made and is currently being investigated, and new and definitive results have been obtained from the parallel experiment, where the authors are studying the effect of capillary contact on foam effectiveness and SMR. Also, during this quarter, a program has been developed to process the results that are generated by the reservoir simulators MASTER and UTCOMP. This is a spreadsheet program containing a series of macros that can be used to plot the flooding performance of a simulation run after it is done. There are converting programs associated with MASTER and UTCOMP so that the results generated by the simulators can be converted into a specific input format to the spreadsheet program. Finally, research continues in two primary areas for task 3: (1) understanding the fundamentals of low interfacial tension behavior via theory and experiment and the influence on multiphase flow behavior and (2) modeling low IFT gravity drainage for application of gas injection in fractured reservoirs.

Download or read book Simulation and Production Evaluation of Multiple stage Hydraulic Fracturing in Horizontal Wellbores written by Mahdi Haddad and published by . This book was released on 2017 with total page 1150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shale formations have globally emerged as the sustainable hydrocarbon resources in the advent of the technologies for the economic production from these formations: horizontal drilling combined with multiple-stage hydraulic fracturing. The viable production from these resources requires a maximized stimulated reservoir volume encompassing a complex induced fracture network, which is highly dependent on the stimulation design. The optimization of the ultimate recovery requires integrated fracturing models with reservoir models in virtue of the limitations on the field data acquisition and their reliability, the high-cost of re-stimulation plans, and low-fidelity current reservoir simulation workflows. We proposed 2D and 3D hydraulic-fracturing models on the basis of the cohesive zone model (CZM) and extended finite element method (XFEM) with a combination of the following capabilities: (1) inclusion of fracture intersections via pore-pressure coupling; (2) fully-coupled poroelasticity in matrix, continuum-based leakoff, and slit flow in fracture(s) with the cohesive behavior for fracture growth. These models were validated in comparison with KGD solution, and were employed for the hydraulic-fracturing design and understanding microseismic event distributions. Moreover, the output of these models in a specific 2D case was integrated with a reservoir simulation workflow for the prediction of long-term production from the induced fracture network. Our 2D and 3D fracture-intersection cases demonstrate the significant role of the following parameters in the growth pattern of fractures upon intersection: (1) the length of the initially open segment of the natural fracture at the intersection; (2) the horizontal stress contrast; (3) the distance between the injection point and the intersection. Notably, hydraulic fracturing in higher depths with higher horizontal stress contrasts and closer injection points to the intersection causes more extensive natural-fracture opening and shear slippage. Also, we demonstrated the application of the proposed 3D fracture intersection model for further understanding of the anomalies observed in the Vaca Muerta Shale. This study revealed that the microseismic events at shallower depths, later times, and deviated from the expected planar distribution are mainly associated with shear slippage along weak interfaces due to the induced stresses by hydraulic fracturing. Thereby, our explicit modeling of fluid infiltration into the natural fracture(s) at the intersection leads to better understanding of the nature of microseismic events. Our multiple-stage, multiple-wellbore, hydraulic-fracturing model for naturally fractured reservoirs includes the operational and field components during the shale stimulations such as perforation tunnel length distribution, horizontal wellbores, stochastically-retrieved fully-cemented natural-fracture network, plugs for the stage stimulation (via connector elements), and external stimulation scenarios (controlled by programming the connector elements in an external user subroutine). The application of this model on synthetic cases shows the following: (1) sequential fracturing with limited number of clusters per stage leads to more control on the cluster stimulation in the presence of the non-uniform perforation tunnel length distribution and wellbore model; (2) proportional cluster efficiency with the perforation tunnel length (promoting the consistent perforation technology); (3) over-estimation of the cluster stimulation in the absence of the wellbore model and/or the natural-fracture network; and (4) more-viscous fracturing fluids conclude less complex induced fracture network (in agreement with the common field observations). The initial natural-fracture network in this model was retrieved from the proposed object-based method. Also, the transfer of the induced fracture network into an embedded discrete fracture model is featured by the higher fidelity in the estimation of long-term gas production from naturally fractured reservoirs. For the investigation of the effect of in-situ stresses on the reservoir engineering problems, we implemented the coupling of a geomechanics module with the UTCOMP reservoir simulator. We first validated this implementation via comparing the results with GPAS and CMG results at various cases. Our improvements in the geomechanics module (lowering the frequency of calling the geomechanics module and the order of the finite-element shape functions) significantly reduced the computational expenses while maintaining the solution accuracy. Overall, water flooding shows more sensitivity to the number of the reservoir-simulation time steps per geomechanics call than gas flooding cases (e.g., CO2 injection). Our reservoir simulation model for re-fracturing included various injection and production steps to show the effect of the re-fracturing fluid injection in a depleted formation on the ultimate recovery. This study showed the significant effect of the re-fracturing water injection in production via changing a single-phase to two-phase gas flow regime and deeper water invasion into the matrix due to the pressure depletion (after primary production)

Download or read book Advances in Fluid Solid Coupling Processes between Fractures and Porous Rocks Experimental and Numerical Investigation written by Shiming Wei and published by Frontiers Media SA. This book was released on with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing is the key measure for improving recovery of unconventional oil and gas reservoirs. Prediction of fracture morphology and productivity after fracturing is critical for fracturing design and optimization. The hydraulic fracturing process is to open porous rocks by artificially injecting highly compressed fluid, and the hydraulic fracture will be closed under the compaction of in-situ stress during the production process. In this regard, hydraulic fracturing and production processes are both fluid-solid coupling processes involving fractures and porous rocks. This Research Topic aims to gather the latest studies addressing how to improve the prediction accuracy of hydraulic fracturing morphology and post-fracturing productivity through experimental and numerical investigation. The experimental research shall underline hydraulic fracturing and fracture conductivity experiments and associated experimental methods, while the numerical research shall pay particular attention to discrete fracture network models, including the calculation efficiency and accuracy as well as the applicability.

Download or read book Improved Efficiency of Miscible CO2 Floods and Enhanced Prospects for CO2 Flooding Heterogeneous Reservoirs Quarterly Technical Progress Report January 1 1996 March 31 1996 written by and published by . This book was released on 1996 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research project is to improve the effectiveness of CO2 flooding in heterogeneous reservoirs. Research is being conducted in three related tasks: (1) exploring further the applicability of selective mobility reduction (SMR) in the use of foam flooding, (2) exploring the possibility of higher economic viability of floods at reduced CO2 injection pressures, and (3) understanding low interfacial tension (IFT) mechanisms with application to CO2 flooding in tight vertically fractured reservoirs. Progress made this quarter in each of the three tasks is discussed. Some of the highlights are: two new surfactants (CD 1040 and Dowfax 8390) were tested and found to reduce mobility; CO2-reservoir phase behavior tests in a static cell have been completed on recombined Spraberry reservoir oil; coreflood foam tests were performed at various CO2 by simultaneously injecting CO2 and surfactant solution into a surfactant solution saturated core until a steady-state pressure drop across the core was obtained; results indicate that the CO2-surfactant solution mobilities were always higher than the baseline tests; and for task 3, research continued in understanding the fundamentals of low interfacial tension behavior via theory and experiment and the influence on multiphase flow behavior, and modeling low IFT gravity drainage for application of gas injection in fractured reservoirs.

Download or read book Embedded Discrete Fracture Modeling and Application in Reservoir Simulation written by Kamy Sepehrnoori and published by Elsevier. This book was released on 2020-08-27 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of naturally fractured reservoirs, especially shale gas and tight oil reservoirs, exploded in recent years due to advanced drilling and fracturing techniques. However, complex fracture geometries such as irregular fracture networks and non-planar fractures are often generated, especially in the presence of natural fractures. Accurate modelling of production from reservoirs with such geometries is challenging. Therefore, Embedded Discrete Fracture Modeling and Application in Reservoir Simulation demonstrates how production from reservoirs with complex fracture geometries can be modelled efficiently and effectively. This volume presents a conventional numerical model to handle simple and complex fractures using local grid refinement (LGR) and unstructured gridding. Moreover, it introduces an Embedded Discrete Fracture Model (EDFM) to efficiently deal with complex fractures by dividing the fractures into segments using matrix cell boundaries and creating non-neighboring connections (NNCs). A basic EDFM approach using Cartesian grids and advanced EDFM approach using Corner point and unstructured grids will be covered. Embedded Discrete Fracture Modeling and Application in Reservoir Simulation is an essential reference for anyone interested in performing reservoir simulation of conventional and unconventional fractured reservoirs. Highlights the current state-of-the-art in reservoir simulation of unconventional reservoirs Offers understanding of the impacts of key reservoir properties and complex fractures on well performance Provides case studies to show how to use the EDFM method for different needs

Download or read book Saudi Aramco Journal of Technology written by and published by . This book was released on 2005 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of Unconventional Reservoirs written by Reza Rezaee and published by MDPI. This book was released on 2020-04-16 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need for energy is increasing and but the production from conventional reservoirs is declining quickly. This requires an economically and technically feasible source of energy for the coming years. Among some alternative future energy solutions, the most reasonable source is from unconventional reservoirs. As the name “unconventional” implies, different and challenging approaches are required to characterize and develop these resources. This Special Issue covers some of the technical challenges for developing unconventional energy sources from shale gas/oil, tight gas sand, and coalbed methane.

Download or read book IMPROVING CO2 EFFICIENCY FOR RECOVERING OIL IN HETEROGENEOUS RESERVOIRS written by and published by . This book was released on 2002 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document is the First Annual Report for the U.S. Department of Energy under contract No., a three-year contract entitled: ''Improving CO2 Efficiency for Recovering Oil in Heterogeneous Reservoirs.'' The research improved our knowledge and understanding of CO2 flooding and includes work in the areas of injectivity and mobility control. The bulk of this work has been performed by the New Mexico Petroleum Recovery Research Center, a research division of New Mexico Institute of Mining and Technology. This report covers the reporting period of September 28, 2001 and September 27, 2002. Injectivity continues to be a concern to the industry. During this period we have contacted most of the CO2 operators in the Permian Basin and talked again about their problems in this area. This report has a summary of what we found. It is a given that carbonate mineral dissolution and deposition occur in a formation in geologic time and are expected to some degree in carbon dioxide (CO2) floods. Water-alternating-gas (WAG) core flood experiments conducted on limestone and dolomite core plugs confirm that these processes can occur over relatively short time periods (hours to days) and in close proximity to each other. Results from laboratory CO2-brine flow experiments performed in rock core were used to calibrate a reactive transport simulator. The calibrated model is being used to estimate in situ effects of a range of possible sequestration options in depleted oil/gas reservoirs. The code applied in this study is a combination of the well known TOUGH2 simulator, for coupled groundwater/brine and heat flow, with the chemistry code TRANS for chemically reactive transport. Variability in response among rock types suggests that CO2 injection will induce ranges of transient and spatially dependent changes in intrinsic rock permeability and porosity. Determining the effect of matrix changes on CO2 mobility is crucial in evaluating the efficacy and potential environmental implications of storing CO2 in the subsurface. Chemical cost reductions are identified that are derived from the synergistic effects of cosurfactant systems using a good foaming agent and a less expensive poor foaming agent. The required good foaming agent is reduced by at least 75%. Also the effect on injectivity is reduced by as much as 50% using the cosurfactant system, compared to a previously used surfactant system. Mobility control of injected CO2 for improved oil recovery can be achieved with significant reduction in the chemical cost of SAG, improved injectivity of SAG, and improved economics of CO2 injection project when compared to reported systems. Our past work has identified a number of mobility control agents to use for CO2-foam flooding. In particular the combination of the good foaming agent CD 1045 and a sacrificial agent and cosurfactant lignosulfonate. This work scrutinizes the methods that we are using to determine the efficiency of the sacrificial agents and cosurfactant systems. These have required concentration determinations and reusing core samples. Here, we report some of the problems that have been found and some interesting effects that must be considered.

Download or read book Energy Research Program of the U S Department of the Interior written by United States. Department of the Interior. Office of Research and Development and published by . This book was released on 1974 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improved Efficiency of Miscible C02 Floods and Enhanced Prospects for C02 Flooding Heterogeneous Reservoirs written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A grant, Improved Efficiency of Miscible CO2 Floods and Enhanced Prospects for CO2 Flooding Heterogeneous Reservoirs, DOE Contract No. DE-FG26-97BC15047, was awarded and started on June 1, 1997. This project examines three major areas in which CO2 flooding can be improved: fluid and matrix interactions, conformance control/sweep efficiency, and reservoir simulation for improved oil recovery. In this quarter we continued the examination of synergistic effects of mixed surfactant versus single surfactant systems to enhance the properties of foams used for improving oil recovery in CO2 floods. The purpose is to reduce the concentration of surfactants and find less expensive surfactants. Also, we are refining reservoir models to handle the complex relationships of CO2-foam and heterogeneous reservoirs. The third area of our report this quarter comprises the results from experiments on CO2-assisted gravity drainage in naturally fractured oil reservoirs. Two more CO2 core flood experiments have been conducted under reservoir conditions to investigate the effect of pressure on oil recovery efficiency during CO2-assisted gravity drainage.