Direct Thickeners for Mobility Control of CO2 Floods

Heller, J.P.; Dandge, D. K.; Card, Roger J.; Donaruma, L. Guy

doi:10.2118/11789-pa

Cited by 108 publications

(126 citation statements)

References 14 publications

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“…Conceptually, the simplest and most direct way to ameliorate the adverse mobility ratios encountered in gas flooding would be to dissolve a viscosifying agent in the injection fluid, just as water-soluble polymers are used to improve water flooding. However, it has proven difficult to find viscosifiers for C0 2 (30). The polymers investigated tend to be soluble only at low molecular weights and to increase viscosities by relatively small amounts.…”

Section: Methods Of Gas-flood Mobility Controlmentioning

confidence: 99%

Promise and Problems of Miscible-Flood Enhanced Oil Recovery

Smith

1988

ACS Symposium Series

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There is no known method or collection of methods that can recover all of the petroleum from an underground reservoir. Even when several different methods are applied sequentially over a period of decades, on average, they leave about two-thirds of the oil trapped in the reservoir (1).Enhanced oil recovery (EOR) is a collective term for various methods of increasing oil recoveries that have been developed since about 1970. Up until about 1980, the use of surfactants in EOR was more or less synonymous with "micellar/polymer" flooding, in which surfactants are used to decrease the interfacial tension between "oil" and "water" from ~ 10 dyne/cm to ≤ 0.01 dyne/cm. However, the term "surfactant flooding" is now becoming increasingly associated with ways to improve gas and steam flooding, rather than with its earlier usage. In the early 1980's disappointment with micellar/polymer flooding became widespread, as almost all oil being produced by EOR was due to steam flooding. But steam flooding was appropriate only for shallow reservoirs containing viscous, "heavy" oil. Hence, the oil industry turned to "gas" flooding, especially with CO 2 , as the main hope for producing substantially more oil by EOR. Thus, in the early 1980's the industry began to make very large investments in gas-flood EOR, and the results of those investments are just beginning to become known.Because they have very low viscosities (compared to oil), steam, CO 2 , and other gases suffer from a major problem: these injected fluids never make contact with much of the reservoir and the oil it contains, but instead channel more or less directly from injection to production well, leaving the uncontacted oil unproduced.By improving "sweep" and "mobility control," surfactant-based methods offer the most promising ways to alleviate these problems. This use of surfactants appears to be just on the verge of commercialization for steam flooding. Because miscible CO 2 flooding has been commercialized more recently, the use of surfactants to improve gas-flood EOR has not yet been commercialized. Conceivably, however, the long-term viability of gas flooding could prove to be dependent on the success of current research efforts in the use of surfactants to alleviate "bypass" problems.This chapter not subject to U.S.

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Section: Methods Of Gas-flood Mobility Controlmentioning

confidence: 99%

Promise and Problems of Miscible-Flood Enhanced Oil Recovery

Smith

1988

ACS Symposium Series

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“…The characteristic of hydrocarbons most commonly associated with enhanced CO 2 -solubility is the presence of polymer side chains [42] or a high degree of branching [43]. This enhanced solubility is usually attributed to the increased polymer free volume and the diminished intermolecular interactions [43].…”

Section: Design Of Oxygenated Hydrocarbon and Hydrocarbon-based Co 2 mentioning

confidence: 99%

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Enick¹,

Beckman²,

Johnson³

2009

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The objective of this research was to use molecular modeling techniques, coupled with our prior experimental results, to design, synthesize and evaluate inexpensive, non-fluorous carbon dioxide thickening agents.The first type of thickener that was considered was associating polymers. Typically, these thickeners are copolymers that contain a highly CO 2 -philic monomer, and a small concentration of a CO 2 -phobic associating monomer.Yale University was solely responsible for the synthesis of a second type of thickener; small, hydrogen bonding compounds. These molecules have a core that contains one or more hydrogen-bonding groups, such as urea or amide groups. Non-fluorous, CO 2 -philic functional groups were attached to the hydrogen bonding core of the compound to impart CO 2 stability and macromolecular stability to the linear "stack" of these compounds.The third type of compound initially considered for this investigation was CO 2 -soluble surfactants. These surfactants contain conventional ionic head groups and composed of CO 2 -philic oligomers (short polymers) or small compounds (sugar acetates) previously identified by our research team. Mobility reduction could occur as these surfactant solutions contacted reservoir brine and formed mobility control foams in-situ.The vast majority of the work conducted in this study was devoted to the copolymeric thickeners and the small hydrogen-bonding thickeners; these thickeners were intended to dissolve completely in CO 2 and increase the fluid viscosity. A small but important amount of work was done establishing the groundwork for CO 2 -soluble surfactants that reduced mobility by generating foams in-situ as the CO 2 +surfactant solution mixed with in-situ brine. PolymersIn this final report, we review our entire co-polymeric thickener effort and detail, for the first time, the phase behavior and viscosity results of the first non-fluorous, oxygenated hydrocarbon-based, associating polymer CO 2 thickener, poly(vinyl acetate -co -benzoyl 5% ). The CO 2 -philic monomer was vinyl acetate, and the associative thickener monomer was vinyl benzoate. Poly(vinyl acetate -co -benzoyl 5% ), Mw ~ 12000, is capable of increasing the viscosity of CO 2 by 70% at a concentration of 2wt%, a shear rate of ~5000s -1 , 298K and 9500 psia. Unfortunately, poly(vinyl acetate -co -benzoyl 5% ) is not capable of dissolving in CO 2 at pressures close to the MMP, roughly 1200 psia at 298 K. In fact, we are now convinced that a non-fluorous, hydrocarbon-based copolymeric thickener cannot be designed that will dissolve in CO 2 at typical reservoir conditions. Why? Every polymer that we designed using molecular modeling tools was indeed CO 2 soluble, a somewhat remarkable achievement given the small number of CO 2 soluble surfactants that have ever been identified, but each one was less soluble in CO 2 than poly(vinyl acetate). Therefore co-polymeric thickeners based on any CO 2 soluble polymer will undoubtedly be less soluble in CO 2 (i.e. require even greater pressures than 9500 psia)...

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“…14,15,[56][57][58][59] In a CO 2 flood, the large viscosity contrast between the reservoir crude oil and injected CO 2 (often >1 cp versus <0.1 cp) induces an unfavorable mobility ratio that can results in early gas breakthrough (increased processing and compression cost) and poor reservoir sweep (lower oil production). Processes such as the injection of water alternating with gas (WAG), 60 direct CO 2 thickeners, 61,62 and surfactant solution alternating with gas (SAG) 63,64 are being used or have been proposed to mitigate these problems. Each has its potential and limitations.…”

Section: Chapter 4 Cost Reduction and Injectivity Improvements For Cmentioning

confidence: 99%

“…[64][65][66][67][68][69][70] It has been shown both in the laboratory and, more importantly, in field demonstration projects that CO 2 foam can improve CO 2 floods in heterogeneous reservoirs. Extensive laboratory evaluations on the effectiveness of CO 2 foam have been reported, but only a limited number of field tests have been performed, with mixed results.…”

Section: Chapter 4 Cost Reduction and Injectivity Improvements For Cmentioning

confidence: 99%

“…81,84 Several surfactants have been identified as relatively good mobility control agents in heterogeneous rocks. 64,85,86 Previous work has shown the effect of foam on delaying CO 2 breakthrough time and the resulting favorable impact on oil recovery. 67,70,87 The decrease or elimination of foam formation in the presence of oil has been reported by several authors.…”

Section: Laboratory Testsmentioning

confidence: 99%

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