Flow Modeling for CO2 Sequestration: The Frio Brine Pilot

Bureau of Economic Geolog

The use of the bimodal production decline curve for the analysis of hydraulically fractured shale/tight gas reservoirs

The capability to conduct a rapid, near real-time model-based analysis of production data from tight/shale (TS) gas fields is important in determining fracture and matrix properties. Model-based analysis of production can range from simple analytical solutions to complex numerical models. The objective of this study is to develop a simple, Excel-based tool for the analysis of the complex problem of gas production from a fractured TS gas reservoir that is based on a robust model that is faithful to the underlying physics and can provide rapid estimates of the important system parameters. The scientifically robust model used as the basis for this tool is a significant modification and expansion of the bimodal production decline curve of Silin and Kneafsey (2012). The production period is divided into two regimes: an early-time regime before the extent of the stimulated reservoir volume (SRV) is felt, where an analytical similarity solution for gas production rate is obtained, and a late-time regime where the rate can be approximated with an exponential decline or more accurately represented with a numerical integration. Our basic model follows Silin and Kneafsey (2012) and produces the widely observed -½ slope on a log-log plot of early-time production decline curves, while our expanded model generalizes this slope to –n, where 0 < n < 1, to represent non-ideal flow geometries. The expanded model was programmed into an Excel spreadsheet to develop an interactive, user-friendly application for curve matching of well production data to the bimodal curve, from which matrix and fracture properties can be extracted. This tool allows significant insight into the model parameters that control the reservoir behavior and production: the geometry of the hydraulically-induced fracture network, its flow and transport properties, and the optimal operational parameters. This information enables informed choices about future operations, and is valuable in several different ways: (a) to estimate reserves and to predict future production, including expected ultimate recovery and the useful lifetime of the stage or the well; (b) if curve-matching is unsuccessful, to indicate the inadequacy of the mathematical model and the need for more complex numerical model to analyze the system; (c) to verify/validate numerical models, and to identify anomalous behavior or measurement errors in the data. The present approach can be adapted to gas-flow problems in dual-permeability media (hydraulically or naturally fractured) or highly heterogeneous sedimentary rock, as well as to retrograde condensation

CO2 plume evolution in a depleted natural gas reservoir: Modeling of conformance uncertainty reduction over time

Uncertainty in the long-term fate of CO2 injected for geologic carbon sequestration (GCS) is a significant barrier to the adoption of GCS as a greenhouse-gas emission-mitigation for industry and regulatory agencies alike. We present a modeling study that demonstrates that the uncertainty in forecasts of GCS site performance decreases over time as monitoring data are used to update operational models. We consider a case study of GCS in a depleted natural gas reservoir, with CO2 injection occurring over 20 years, with a 50-year post-injection site care period. We constructed a detailed model to generate the actual model output, which is considered synthetic observation data. A series of simpler operational models based on limited data and assumptions about how an operator would model such a site are then run and compared against actual model output at specific monitoring points after one year, two years, etc. The operational model is updated and improved using the synthetic observation data from the actual model at the same time intervals. Model parameter values and model features needed to be updated over time to improve matches to the actual model. These kinds of model adjustments would be a normal part of reservoir engineering and site management at GCS sites. Uncertainty in two key measures related to site performance decreases with time: extent of the CO2 plume up-dip migration, and radial extent of the pressure pulse. This conclusion should help allay the concerns of industry and regulators about uncertainty in long-term fate of CO2 at GCS sites

Using multiphase fluid flow modeling and time-lapse electromagnetics to improve 4D monitoring of CO 2 in an EOR reservoir

Understanding the changes in the saturation within a reservoir undergoing enhanced oil recovery (EOR) is crucial to optimizing production. We debut a novel, multiphase fluid flow modelling code, TOGA, to assist in modeling gas, oil, and water phases within the reservoir, and combine its output with time-lapse Depth to Surface Resistivity data in a case study involving an EOR reservoir. The results show the potential for combining the two methods to improve our understanding of reservoir saturation over an extended period of time

Sensitivity of CO2 migration estimation on reservoir temperature and pressure uncertainty

The density and viscosity of supercritical CO2 are sensitive to pressure and temperature (PT) while the viscosity of brine is sensitive primarily to temperature. Oil field PT data in the vicinity of WESTCARB's Phase III injection pilot test site in the southern San Joaquin Valley, California, show a range of PT values, indicating either PT uncertainty or variability. Numerical simulation results across the range of likely PT indicate brine viscosity variation causes virtually no difference in plume evolution and final size, but CO2 density variation causes a large difference. Relative ultimate plume size is almost directly proportional to the relative difference in brine and CO2 density (buoyancy flow). The majority of the difference in plume size occurs during and shortly after the cessation of injection. © 2009 Lawrence Berkeley National Laboratory

Computer game technology, collaborative software environments and participatory design

This paper presents a project that explores the possibilities for the use of computer game technologies in the participatory design process. Interactive 3D environments designed with the Virtools development environment were used in a Home Zone consultation process, which allowed participants to navigate, explore and contribute to proposed developments to their residential environment. These technologies were observed to benefit the participatory design process in some areas, namely the visualization and contextualizing of the developments, but also presented traditional technological barriers in others. While these barriers did not completely remove the participants from the process, they reduced the apparent level of engagement of these participants with the process. This paper concludes that the technology overall, is a positive addition to the participatory design process, and while there is still much research to be undertaken, it has many more potential applications in related areas

Contesting Community: Legalized Reconciliation Efforts in the Aftermath of Genocide in Rwanda

In recent decades, national governments and international authorities have increasingly emphasized the role of legal institutions in restoring order after political violence. This study explores how, following the 1994 genocide, the Rwandan government created new decentralized grassroots legal forums that aimed to produce community out of a divided population. The legal institutions were designed to enable Rwandans to resolve disputes with the help of locally-elected mediators, based on principles that prioritized collective cohesion over individual rights, combined with state-backed punishment. Drawing on eighteen months of ethnographic research in Rwanda between 2004 and 2008 with genocide courts (inkiko gacaca), mediation committees (comite y’abunzi) and a legal aid clinic, this study shows how the discourse of mediation in courts derived from national and transnational processes, and how it shaped people’s experiences across a wide range of disputes. People used the courts’ flexible proceedings both to rebuild inclusive relationships, and to contest belonging and reinforce divisions. The study suggests that state-backed legal forums embedded in daily life can facilitate social rebuilding in the aftermath of violence, while it examines what differences are created as “community” is brought into being through politicized processes, and shows how customary law as a tool of state development can both empower and curtail rights

Automatic signal range selector for metering devices Patent

Voltage range selection apparatus for sensing and applying voltages to electronic instruments without loading signal sourc

Can consumer-led mental health services be equally effective? An integrative review of CLMH services in high-income countries

This study examined the evidence from controlled studies for the effectiveness of consumer-led mental health services. Following an extensive search of material published in English from 1980, predefined inclusion criteria were systematically applied to research articles that compared a consumer-led mental health service to a traditional mental health service. A total of 29 eligible studies were appraised; all of them were conducted in high-income countries. Overall consumer-led services reported equally positive outcomes for their clients as traditional services, particularly for practical outcomes such as employment or living arrangements, and in reducing hospitalizations and thus the cost of services. Involving consumers in service delivery appears to provide employment opportunities and be beneficial overall for the consumer-staff members and the service. Despite growing evidence of effectiveness, barriers such as underfunding continue to limit the use and evaluation of consumer-led services. Future studies need to adopt more uniform definitions and prioritize the inclusion of recovery oriented outcome measures. © Springer Science+Business Media, LLC 2010.postprin