Systematic study of foam for improving sweep efficiency in chemical enhanced oil recovery

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Title: Systematic study of foam for improving sweep efficiency in chemical enhanced oil recovery
Author: Nguyen, Nhut Minh, 1984-
Abstract: Foam -assisted low interfacial tension and foam -improved sweep efficiency are attractive enhanced oil recovery (EOR ) methods with numerous studies and researches have been conducted in the past few decades . For example , CO₂ -Enhanced Oil Recovery (CO₂ -EOR ) is very efficient in terms of oil displacement . However , due to the low viscosity of super critical CO₂ , the process usually suffers from poor sweep efficiency . One method of increasing sweep efficiency in CO₂ -EOR has been identified through the use of surfactants to create "foams" or more correctly CO₂ -in -water (C /W ) macroemulsions . Polymer flooding techniques such as Alkali - - Polymer (AP ) , Surfactant - - Polymer (SP ) , and Alkali - - Surfactant - - Polymer (ASP ) have been the only proven chemical EOR method in sandstone reservoirs with many successful pilot tests and field projects . However , the use of polymer is limited in carbonates due to unfavorable conditions related to natural characteristics of this type of lithology . In this case , foam -assisted EOR , specifically Alkali - - Surfactant - - Gas (ASG ) process , can be an alternative for polymer flooding . It is a fact that large amount of the world's oil reserves resides in carbonate reservoirs . Therefore , an increase in oil recovery from carbonates would help meet the world's increasing energy demand . This study consists of two parts : (1 ) the development of new surfactant for creating CO₂ - - in - - water macroemulsions for improving sweep efficiency in CO₂ - - EOR processes ; (2 ) systematic study of ASG method as a novel EOR technique and an alternative for polymer flooding in carbonate reservoirs . Both studies are related to the use of foam as a mobility control agent . In the first part , the design and synthesis of twin tailed surfactants for use at the CO₂ /water interface is discussed . The hydrohobes for these surfactants are synthesized from epichlorohydrin and an excess alcohol . Subsequent ethoxylation of the resulting symmetrical dialkyl glycerin yields the water soluble dual tailed surfactants . The general characteristics of these surfactants in water are described . A comparison is carried out between twin -tailed dioctylglycerine surfactants and linear secondary alcohol surfactant based on results from a core flood . The results show that even above the cloud point of the surfactants , the twin tailed surfactants create a significant mobility reduction , likely due to favorable partitioning into the CO₂ phase . The data covers surfactant structures designed specifically for the CO₂ -water interface and can be used by producers and service companies in designing new CO₂ -floods , especially in areas that might not have been considered due to problems with reservoir heterogeneity . Second part contains a systematic study of ASG process on carbonate rocks through a series of experiments . The purpose is to demonstrate the performance as well as the potential of ASG as a new EOR technique . In this study , basic concepts in chemical EOR are presented , while the design of chemical formulation , phase behavior , and the role of foam are discussed in details . Experimental results showed relatively good recovery , low surfactant retention . However , pressure drop during chemical injections were high , which indicates the formation of both strong foam and viscous microemulsion at the displacement front when surfactant starts solubilizing oil . Overall , ASG showed good performance on carbonate rocks . Optimization can be made on surfactant formula to form less viscous microemulsion and therefore improve efficiency of the process .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2649
Date: 2011-02-17


Systematic study of foam for improving sweep efficiency in chemical enhanced oil recovery. Master's thesis, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2649 .

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