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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Optimization of a CO2 flood design Wesson Field - west Texas

Garcia Quijada, Marylena 30 October 2006 (has links)
The Denver Unit of Wasson Field, located in Gaines and Yoakum Counties in west Texas, produces oil from the San Andres dolomite at a depth of 5,000 ft. Wasson Field is part of the Permian Basin and is one of the largest petroleum-producing basins in the United States. This research used a modeling approach to optimize the existing carbon dioxide (CO2) flood in section 48 of the Denver Unit by improving the oil sweep efficiency of miscible CO2 floods and enhancing the conformance control. A full compositional simulation model using a detailed geologic characterization was built to optimize the injection pattern of section 48 of Denver Unit. The model is a quarter of an inverted nine-spot and covers 20 acres in San Andres Formation of Wasson Field. The Peng-Robinson equation of state (EOS) was chosen to describe the phase behavior during the CO2 flooding. An existenting geologic description was used to construct the simulation grid. Simulation layers represent actual flow units and resemble the large variation of reservoir properties. A 34-year history match was performed to validate the model. Several sensitivity runs were made to improve the CO2 sweep efficiency and increase the oil recovery. During this study I found that the optimum CO2 injection rate for San Andres Formation in the section 48 of the Denver Unit is approximately 300 res bbl (762 Mscf/D) of carbon dioxide. Simulation results also indicate that a water-alternating-gas (WAG) ratio of 1:1 along with an ultimate CO2 slug of 100% hydrocarbon pore volume (HCPV) willallow an incremental oil recovery of 18%. The additional recovery increases to 34% if a polymer is injected as a conformance control agent during the course of the WAG process at a ratio of 1:1. According to the results, a pattern reconfiguration change from the typical Denver Unit inverted nine spot to staggered line drive would represent an incremental oil recovery of 26%.
2

Study of CO2 Mobility Control Using Cross-linked Gel Conformance Control and CO2 Viscosifiers in Heterogeneous Media

Cai, Shuzong 2010 August 1900 (has links)
CO2 has been widely used as a displacement fluid in both immiscible and miscible displacement processes to obtain tertiary recovery from the field. There are several problems associated with the application of CO2 flooding, especially when there is a significant presence of heterogeneous elements, such as fractures, channels and high permeability streaks within the reservoir. With flooding, CO2 will finger through the target zone while leaving most of the residual/trapped oil untouched. As a result, early gas breakthrough has been a very common problem in CO2-related projects, reducing the overall sweep efficiency of CO2 flooding. This research aims at improving the CO2 flood efficiency using cross-linked gel conformance control and CO2 viscosifier technique. A series of coreflood experiment studies have been performed to investigate the possibility of applying CO2 mobility control techniques. Corresponding simulation works have also been carried out to predict the benefits of applying CO2 mobility control techniques in the field. In the laboratory study, the CO2 coreflood system was integrated with the CT (Computed Tomography)-scanner and obtained real-time coreflood images of the CO2 saturation distributions in the core. This system was applied to the research of both cross-linked polymer gel treatment and CO2 viscosifier study and produced images with sharp phase contrasts. For the gel conformance study, promising results were obtained by applying cross-linked gel to eliminate permeability contrast and diverting CO2 into low permeability regions to obtain incremental oil recovery; also studied were the gel strength in terms of leak-off extent with the aid of CT (Computed Tomography) images. For the CO2 viscosifier research, we tested several potential viscosifier chemicals and found out PVAc (Polyvinylacetate)/toluene combination to be the most promising. The follow-up study clearly demonstrates the superiority of viscosified CO2 over neat CO2 in terms of sweep efficiency. This research serves as a preliminary study in understanding advanced CO2 mobility control techniques and will provide insights to future studies on this topic.
3

Mobility control of CO₂ flooding in fractured carbonate reservoirs using faom with CO₂ soluble surfactant

Zhang, Hang 06 November 2012 (has links)
This work investigates the performance of CO₂ soluble surfactants used for CO₂ foam flooding in fractured carbonate reservoirs. Oil recovery associated with the reduction of CO₂ mobility in fractures is assessed by monitoring oil saturation and pressure drops during injection of CO₂ with aqueous surfactant solution in artificially fractured carbonate cores. Distinct novel CO₂ soluble surfactants are evaluated as well as a conventional surfactant. Water flooding and pure CO₂ injection are conducted as baseline. Characterization of fluids and rock are also reported which include Amott test, oil phase behavior and slim tube test. Transport and thermodynamic properties of surfactant and supercritical CO₂ are used to evaluate the process on a core scale using a commercial reservoir simulator. / text
4

Decision support for enhanced oil recovery projects

Andonyadis, Panos 14 February 2011 (has links)
Recently, oil prices and oil demand are rising and are projected to continue to rise over the long term. These trends create great potential for enhanced oil recovery methods that could improve the recovery efficiency of reservoirs all over the world. The greatest challenges for enhanced oil recovery involve the technical uncertainty with design and performance, and the high financial risk. Pilot tests can help mitigate the risk associated with such projects; however, there is a question about the value of information from the tests. Decision support can provide information about the value of an enhanced oil recovery project, which can assist with alleviating financial risk and create more potential opportunities for the technology. The first objective of this study is to create a new simplified method for modeling oil production histories of enhanced oil recovery methods. The method is designed to satisfy three criteria: 1) it allows for quick simulations based on only a few physically meaningful input parameters; 2) it can create almost any potential type of realistic production history that may be realized during a project; and 3) it applies to all nonthermal enhanced oil recovery methods, including surfactant-polymer, alkali-surfactant polymer, and CO₂ floods. The developed method is capable of creating realistic curves with only four unique parameters. The second objective is to evaluate the predictive method against data from pilot and field scale projects. The evaluations demonstrate that the method can fit most realistic production histories as well as provided ranges for the input parameters. A sensitivity analysis is also performed to assist with determining how all of the parameters involved with the predictive method and the economic model influence the forecasted value for a project. The analysis suggests that the price of oil, change in oil saturation, and the size of the reservoir are the most influential parameters. The final objective is to establish a method for a decision analysis that determines the value of information of a pilot for enhanced oil recovery. The analysis uses the predictive method and economic model for determining economic utilities for every potential outcome. It uses a decision-based method to ensure that the non-informative prior probability distributions have an unbiased, consistent, and rational starting point. A simple example demonstrating the process is discussed and it is used to show that a pilot test provides some valuable information when there is minimal prior information. For future work it is recommended that more evaluations are performed, the decision analysis is expanded to include more input parameters, and a rational and logical method is developed for determining likelihood functions from existing information. / text
5

Laboratory and modelling studies on the effects of injection gas composition on CO₂-rich flooding in Cooper Basin, South Australia.

Bon, Johannes January 2009 (has links)
This Ph.D. research project targets Cooper Basin oil reservoirs of very low permeability (approximately 1mD) where injectivities required for water flooding are not achievable. However, the use of injection gases such as CO₂ would not have injectivity problems. CO₂ is abundant in the region and available for EOR use. CO₂ was compared to other CO₂-rich injection gases with a hydrocarbon content including pentane plus components. While the effect of hydrocarbon components up to butane have been investigated in the past, the effect of n-pentane has on impure CO₂ gas streams has not. One particular field of the Cooper Basin was investigated in detail (Field A). However, since similar reservoir and fluid characteristics of Field A are common to the region it is expected that the data measured and developed has applications to many other oil reservoirs of the region and similar reservoirs elsewhere. The aim of this Ph.D. project is to determine the applicability of CO₂ as an injection gas for Enhanced Oil Recovery (EOR) in the Cooper Basin oil reservoirs and to compare CO₂ with other possible CO₂-rich injection gases. The summarised goals of this research are to: • Determine the compatibility of Field A reservoir fluid with CO₂ as an injection gas. • Compare CO₂ to other injection gas options for Field A. • Development of a correlation to predict the effect of nC₅ on MMP for a CO₂- rich injection gas stream. These goals were achieved through the following work: • Extensive experimental studies of the reservoir properties and the effects of interaction between CO₂-rich injection gas streams and Field A reservoir fluid measuring properties related to: • Miscibility of the injection gas with Field A reservoir fluid • Solubility and swelling properties of the injection gas with Field A reservoir fluid • Change in viscosity-pressure relationship of Field A reservoir fluid due to addition of injection gas • A reservoir condition core flood experiment • Compositional simulation of the reservoir condition core flood to compare expected recoveries from different injection gases • Development of a set of Minimum Miscibility Pressure (MMP) measurements targeted at correlating the effect of nC₅ on CO₂ MMP. The key findings of this research are as follows: • Miscibility is achievable at practical pressures for Field A and similar reservoir fluids with pure CO₂ or CO₂-rich injection gases. • For Field A reservoir fluid, viscosity of the remaining flashed liquid will increase at pressures below ~2500psi due to mixing the reservoir fluid with a CO₂-rich injection gas stream. • Comparison of injection gases showed that methane rich gases are miscible with Field A so long as a significant quantity of C₃+ components is also present in the gas stream. • There is a defined trend for effect of nC₅ on MMP of impure CO₂. This trend was correlated with an error of less than 4%. • Even though oil composition is taken into account with the base gas MMP, it still affects the trend for effect of nC₅ on MMP of a CO₂-rich gas stream. • An oil characterisation factor was developed to account for this effect, significantly improving the results, reducing the error of the correlation to only 1.6%. The significance of these findings is as follows: • An injection pressure above ~3000psi should be targeted. At these pressures miscibility is achieved and the viscosity of the reservoir fluid injection gas mix is reduced. • CO₂ should be compared to gases such as Tim Gas should after considering the cost of compression, pipeline costs and distance from source to destination will need to be considered. • The addition of nC₅ will reduce the MMP and increase the recovery factor, however the cost of the nC₅ used would be more than the value of increased oil recovered. • The developed correlation for the effect of nC₅ on impure CO₂ MMP can be used broadly within the limits of the correlation. • Further research using more oils is necessary to validate the developed oil characterisation factor and if successful, using the same or similar method used to improve other correlations. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1369016 / Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 2009.

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