Download or read book Final Report of A Detailed Study of the Physical Mechanisms Controlling CO2 Brine Capillary Trapping in the Subsurface University of Arizona DE SC0006696 written by and published by . This book was released on 2016 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon capture and storage (CCS) of carbon dioxide emissions generated by production or combustion of fossil fuels is a technologically viable means to reduce the build-up of CO2 in the atmosphere and oceans. Using advantages of scale and location, CCS is particularly suitable for large point sources near ubiquitous deep saline aquifers, depleted gas reservoirs, or at production reservoirs for enhanced oil recovery (EOR). In the BES-funded research project, Oregon State University (OSU) carried out capillary trapping experiments with proxy fluids that mimic the properties of the scCO2/brine system under ambient temperatures and pressures, and successfully developed a unique and novel x-ray compatible, high-pressure, elevated temperature setup to study the scCO2/brine system under challenging reservoir conditions. Both methodologies were applied to a variety of porous media, including synthetic (glass bead) and geologic (Bentheimer sandstone) materials. The University of Arizona (UA) developed pore-scale lattice Boltzmann (LB) models which are able to handle the experimental conditions for proxy fluids, as well as the scCO2/brine system, that are capable of simulating permeability in volumes of tens of millions of fluid elements. We reached the following summary findings (main institute indicated): 1. (OSU/UA) To understand capillary trapping in a multiphase fluid-porous medium system, the system must be analyzed from a pore-scale force balance perspective; trapping can be enhanced by manipulating wetting and nonwetting phase fluid properties. 2. (OSU) Pore-scale fluid connectivity and topology has a clear and direct effect on nonwetting phase capillary trapping efficiency. 3. (OSU) Rock type and flow regime also have a pronounced effects on capillary trapping. 4. (OSU/UA) There is a predictable relationship between NWP connectivity and NWP saturation, which allows for development of injection strategies that optimize trapping. The commonly used Land model (Land, 1968) does not predict amount of trapped NWP accurately. 5. (UA) There are ambiguities regarding the segmentation of large-volume gray-scale CT data into pore-volumes suitable for pore-scale modeling. Simulated permeabilities vary by three orders of magnitude and do not resemble observed values very well. Small-volume synchrotron-based CT data (such as produced by OSU) does not suffer significantly from segmentation ambiguities. 6. (UA) A standard properly parameterized Shan-Chen model LB model is useful for simulating porous media with proxy fluids as well as the scCO2/brine system and produces results that are consistent with tomographic observations. 7. (UA) A LB model with fluid-interactions defined by a (modified) Peng-Robinson Equation of State is able to handle the scCO2/brine system with variable solid phase wettability. This model is numerically stable at temperatures between 0 and 250 °C and pressures between 3 and 50 MPa, and produces appropriate densities above the critical point of CO2 and exhibits three-phase separation below. Based on above findings OSU and UA have proposed continued experimentation and pore-scale modeling of the scCO2/brine system. The reported research has extensively covered capillary trapping using proxy fluids, but due to limited beam-time availability we were unable to apply our high-pressure CO2 setup to sufficient variation in fluid properties, and initial scCO2 connectivity. New data will also allow us to test, calibrate and apply our LB models to reservoir conditions beyond those that are currently feasible experimentally. Such experiments and simulations will also allow us to provide information how suitable proxy fluids are for the scCO2/brine system. We believe it would be worthwhile to pursue the following new research questions: 1. What are the fundamental differences in the physics underlying capillary trapping at ambient vs. supercritical conditions? 2. Do newly developed pore-scale trapping interactions and relations ...

Download or read book A Detailed Study of CO2 brine Capillary Trapping Mechanisms as Applied to Geologic Carbon Storage Final Report written by and published by . This book was released on 2017 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proposed research focuses on improved fundamental understanding of the efficiency of physical trapping mechanisms, and as such will provide the basis for subsequent upscaling efforts. The overarching hypothesis of the proposed research is that capillary pressure plays a significant role in capillary trapping of CO2, especially during the water imbibition stage of the sequestration process. We posit that the relevant physics of the sequestration process is more complex than is currently captured in relative permeability models, which are often based on so-called trapping models to represent relative permeability hysteresis. Our 4 main questions, guiding the 4 main tasks of the proposed research, are as follows: (1) What is the morphology of capillary trapped CO2 at the pore scale as a function of temperature, pressure, brine concentration, interfacial tension, and pore-space morphology under injection and subsequent imbibition? (2) Is it possible to describe the capillary trapping process using formation-dependent, but otherwise unique continuum-scale functions in permeability-capillary pressure, interfacial area and saturation space, rather than hysteretic functions in permeability-saturation or capillary pressure-saturation space? (3) How do continuum-scale relationships between kr-Pc-S-Anw developed based on pore-scale observations compare with traditional models incorporating relative permeability hysteresis (such as Land's and other models,) and with observations at the core (5-10cm) scale? (4) How can trapped CO2 volume be optimized via engineered injection and sweep strategies, and as a function of formation type (incl. heterogeneity)?

Download or read book Local Capillary Trapping in Geological Storage of Carbon Dioxide CO2 written by Ehsan Saadatpoor and published by . This book was released on 2017 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: After the injection of CO2 into a subsurface formation, storage mechanisms help immobilize the CO2. Injection strategies that promote the movement of CO2 during the post-injection period can increase immobilization by mechanisms of dissolution and residual phase trapping. This book argues that the heterogeneity intrinsic to sedimentary rocks gives rise to another category of trapping called "local capillary trapping." The study presented in this book evaluates local capillary trapping, its effectiveness to add an element of increased capacity and containment security in CO2 storage, and assesses the amount and extent of local capillary trapping expected to occur in typical storage formations.

Download or read book An Investigation Into the Pore scale Mechanisms of Capillary Trapping written by Anna L. Herring and published by . This book was released on 2015 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geologic CO2 sequestration is a climate change mitigation strategy that prevents CO2 emissions to the atmosphere by capturing CO2 gasses from large point source emissions streams and then pressurizing and pumping the supercritical-state CO2 into underground geologic storage reservoirs. Once underground, CO2 is prevented from buoyant migration to the surface by various trapping mechanisms, one of which is capillary trapping. Capillary trapping is a secure trapping mechanism that immobilizes CO2 on relatively short timescales; accurate prediction and optimization of capillary trapping of CO2 is crucial to ensure the safety and success of a sequestration operation. The research comprising this dissertation utilizes x-ray computed microtomography (x-ray CMT) to allow for three-dimensional (3D) investigation of the main factors influencing nonwetting phase capillary trapping from a pore-scale in-situ perspective. Results from ambient- and supercritical-condition experiments are presented that provide insight as to the controls on capillary trapping during multiphase flow in porous media. The presented findings may be used to help design injection strategies that optimize capillary trapping of CO2 during sequestration operations and to help develop more accurate predictive transport models.

Download or read book Optimization of Capillary Trapping of CO2 Sequestration in Saline Aquifers written by Elizabeth Joy Harper and published by . This book was released on 2012 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geological carbon sequestration, as a method of atmospheric greenhouse gas reduction, is at the technological forefront of the climate change movement. During sequestration, carbon dioxide (CO2) gas effluent is captured from coal fired power plants and is injected into a storage saline aquifer or depleted oil reservoir. In an effort to fully understand and optimize CO2 trapping efficiency, the capillary trapping mechanisms that immobilize subsurface CO2 were analyzed at the pore-scale. Pairs of proxy fluids representing the range of in situ supercritical CO2 and brine conditions were used during experimentation. The two fluids (identified as wetting and non-wetting) were imbibed and drained from a flow cell apparatus containing a sintered glass bead column. Experimental and fluid parameters, such as interfacial tension, fluid viscosities and flow rate, were altered to characterize their relative impact on capillary trapping. Computed x-ray microtomography (CMT) was used to identify immobilized CO2 (non-wetting fluid) volumes after imbibition and drainage events. CMT analyzed data suggests that capillary behavior in glass bead systems do not follow the same trends as in consolidated natural material systems. An analysis of the disconnected phases in both the initial and final flood events indicate that the final (residual) amount of trapped non-wetting phase has a strong linear dependence on the original amount of non-wetting phase (after primary imbibition), which corresponds to the amount of gas or oil present in the formation prior to CO2 injection. More importantly, the residual trapped gas was also observed to increase with increasing non-wetting fluid phase viscosity. This suggests that CO2 sequestration can be optimized in two ways: through characterization of the trapped fluid present in the formation prior to injection and through alterations to the viscosity of supercritical CO2.

Download or read book Local Capillary Trapping in Geological Carbon Storage written by Ehsan Saadatpoor and published by . This book was released on 2012 with total page 750 pages. Available in PDF, EPUB and Kindle. Book excerpt: After the injection of CO2 into a subsurface formation, various storage mechanisms help immobilize the CO2. Injection strategies that promote the buoyant movement of CO2 during the post-injection period can increase immobilization by the mechanisms of dissolution and residual phase trapping. In this work, we argue that the heterogeneity intrinsic to sedimentary rocks gives rise to another category of trapping, which we call local capillary trapping. In a heterogeneous storage formation where capillary entry pressure of the rock is correlated with other petrophysical properties, numerous local capillary barriers exist and can trap rising CO2 below them. The size of barriers depends on the correlation length, i.e., the characteristic size of regions having similar values of capillary entry pressure. This dissertation evaluates the dynamics of the local capillary trapping and its effectiveness to add an element of increased capacity and containment security in carbon storage in heterogeneous permeable media. The overall objective is to obtain the rigorous assessment of the amount and extent of local capillary trapping expected to occur in typical storage formations. A series of detailed numerical simulations are used to quantify the amount of local capillary trapping and to study the effect of local capillary barriers on CO2 leakage from the storage formation. Also, a research code is developed for finding clusters of local capillary trapping from capillary entry pressure field based on the assumption that in post-injection period the viscous forces are negligible and the process is governed solely by capillary forces. The code is used to make a quantitative assessment of an upper bound for local capillary trapping capacity in heterogeneous domains using the geologic data, which is especially useful for field projects since it is very fast compared to flow simulation. The results show that capillary heterogeneity decreases the threshold capacity for non-leakable storage of CO2. However, in cases where the injected volume is more than threshold capacity, capillary heterogeneity adds an element of security to the structural seal, regardless of how CO2 is accumulated under the seal, either by injection or by buoyancy. In other words, ignoring heterogeneity gives the worst-case estimate of the risk. Nevertheless, during a potential leakage through failed seals, a range of CO2 leakage amounts may occur depending on heterogeneity and the location of the leak. In geologic CO2 storage in typical saline aquifers, the local capillary trapping can result in large volumes that are sufficiently trapped and immobilized. In fact, this behavior has significant implications for estimates of permanence of storage, for assessments of leakage rates, and for predicting ultimate consequences of leakage.

Download or read book CO2 Exsolution Challenges and Opportunities in Subsurface Flow Management written by Lin Zuo and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon dioxide is known to be highly soluble in water/brine, up to 5% mass fraction under reservoir conditions. In geological carbon sequestration, a large amount of injected CO2 will dissolve in brine over time. Exsolution occurs when pore pressures decline and CO2 solubility in brine decreases, resulting in the formation of a separate CO2 phase. This scenario occurs in carbon sequestration reservoirs by upward migration of CO2 saturated brine, through faults, leaking boreholes or even seals. In this way, dissolved CO2 could migrate out of storage reservoir and form a gas phase at shallower depths. Questions such as how exsolved CO2 distributes and transports, and how multiphase flows and trapping are altered in a reservoir undergoing exsolution need to be answered to achieve better subsurface flow management and risk evaluation. This study summarizes the results regarding the implications of exsolution on storage security, including pore-scale and core-scale experiments, pore-scale modeling, and numerical simulations. Applications of CO2 exsolution in Enhanced Oil Recovery are also explored. Microscopic observation of CO2 exsolution in porous media under reservoir conditions have shown that, different from an injected CO2 phase, where the gas remains interconnected and distributes at capillary equilibrium, exsolved CO2 nucleates in various locations of a porous medium, forms disconnected bubbles and propagates by repeated expansion-snap off process under capillary instability. A good correlation between bubble size distribution and pore size distribution is observed, indicating that geometry of the pore space plays an important role in controlling the mobility of brine and exsolved CO2. Core-scale multiphase flow experiments demonstrate that in the process where growing gas bubbles displace water (drainage), the water relative permeability drops significantly and is disproportionately reduced compared to gas injection, and the CO2 relative permeability remains very low, 10^-5 to 10^-3, even when the exsolved CO2 saturation increases to over 40%. Furthermore, during imbibition, exsolved CO2 remains trapped even under relatively high capillary numbers (~ 10^-6), and the water relative permeability at the imbibition endpoint is one third to one half of that with water displacing injected CO2. A model is developed to simulate the growth of exsolved gas phase in porous media under capillarity. Results are compared with experimental observations using three dimensional micro X-ray tomography. Convective transfer in the aqueous phase has been demonstrated to play an important role in controlling bubble growth and accumulation. With a Stokes flow simulator, water relative permeability curves are estimated for various sedimentary rocks under different conditions. We are capable of matching modeled gas distribution and relative permeabilities with experimental data, and extrapolating expected phase mobility reductions under reservoir conditions. CO2 exsolution does not appear to create significant risks for storage security. Due to the low mobility of exsolved CO2 and its large impact on reducing water flow, if carbonated brine migrates upwards and exsolution occurs, brine migration would be greatly reduced and limited by the presence of exsolved CO2 and the consequent low relatively permeability to brine. Similarly, if an exsolved CO2 phase were to evolve in the seal, for example, after CO2 injection stops, the effect would be to reduce the permeability to brine and the CO2 would have very low mobility. It is also possible that CO2 exsolution could have an effect on CO2-EOR recovery. This flow blocking effect is studied in experiments with water/oil/CO2 for the purpose of water conformance and oil recovery enhancement. Experiments show that exsolved CO2 performs as a secondary residual phase in porous media that effectively blocks established water flow paths and deviates water to residual oil zones, thereby increasing recovery. Overall, our studies suggest that CO2 exsolution provides an opportunity for mobility control in subsurface processes. For example, CO2 exsolution generated intentionally increases water sweep efficiency in oil reservoirs and forms gas barriers to seal high permeability zones. However, while the experimental evidence for dramatic mobility reduction is clear, the lack of simulation capability that accounts for differences between the CO2 phase morphology resulting from gas injection and gas exsolution creates challenges for modeling and hence, designing studies to exploit the mobility reduction capabilities of CO2 exsolution. Not only is history dependent behavior (hysteresis) important, but also process dependent behavior is needed. Using traditional drainage multiphase flow parameterization in simulations involving exsolution will lead to overestimates of flows and large errors in transport rates. Development of process dependent parameterizations of multiphase flow properties will be a key next step and will help to unlock the benefits from gas exsolution.