Subscriber access provided by University of Otago Library
Article
Interactions between Formation Rock and Petroleum Fluids during Microemulsion Flooding and Alteration of Heavy Oil Recovery Performance Ronald Nguele, Kyuro Sasaki, Yuichi Sugai, Brian A. Omondi, Hikmat Said-Al Salim, and Ryo Ueda Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02216 • Publication Date (Web): 22 Nov 2016 Downloaded from http://pubs.acs.org on November 25, 2016
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 38
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
Interactions
between
Formation
Rock
and
Petroleum Fluids during Microemulsion Flooding and Alteration of Heavy Oil Recovery Performance
Ronald Nguele†*, Kyuro Sasaki†, Yuichi Sugai†, Brian Omondi‡, Hikmat Said Al-Salim₴ and Ryo Ueda₡ †
Resource Production & Safety Engineering Laboratory, Kyushu University, Fukuoka 819-0395
Japan; ‡
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka
819-0395, Japan; ₴
Department of Chemical & Petroleum Engineering, UCSI University, 56000 Kuala Lumpur,
Malaysia; ₡
Research Center, Japan Petroleum Exploration, Chiba 261-0025, Japan
KEYWORDS: Microemulsion; Heavy oil; enhanced oil recovery, ex-situ solubilization
ABSTRACT- In-situ emulsification/solubilization is an oil recovery technique routinely used to mobilize residual oil after the secondary oil production (waterflooding). The oil is produced after a subsequent reduction of interfacial tension (IFT) between stranded crude oil and water in the reservoir. Herein is presented a recovery method for heavy crude oils whose scheme consists of the injection of a fully solubilized (or emulsified) oil. Theoretically, the fully solubilized oil, referred hereinafter as microemulsion formulation, reduces the viscous forces that keep residual oil stranded. Different microemulsion formulations were prepared ex-situ from two heavy oils (API 11.5 and 16.6), micellar ACS Paragon Plus Environment 1
Energy & Fuels
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 38
slugs (formulated from cationic Gemini surfactant) and low saline water (0.1 wt.% NaCl). Tertiary heavy oil recovery consisted in displacing residual oil, from a waterflooded core, by a specific microemulsion formulation followed by low-saline water, which acted as buffer solution. 31% of initial oil-in-place (IOIP) was recovered from waterflooded core by microemulsion followed by an incremental oil recovery of about 20% of IOIP with chase water. The oil recovery efficiency, by microemulsion and chase water floodings, was lowered to 15% and 28% respectively in a strong oilwet core (i.e. non waterflooded core). Despite the promising results presented herein, the performance of the microemulsion formulations, and thus the oil recovery efficiency, was found to be strongly dependent of (1) the nature of the core i.e. its mineralogy, (2) the wetting state of plug and (3) the chemical composition advancing fluid. The microemulsion formulations prompted a series of chemical reactions, which subsequently altered their performance as displacing agent. Ion tracking analysis of the effluent fractions showed that the pH and the concentration in divalent and/or monovalent ions were also altered at each stage of production. When the plug was not waterflooded, the oil was produced along with a deposit of sludge and a high emulsion cut. However, the use of preflush enriched with an alkali (Na2CO3), was found to abate both effects. Furthermore, the spectral analysis of effluent fractions revealed the formation of calcium bridges, which are thought to alter the efficiency of microemulsion formulations. Also, a series of chemical schemes, are proposed in this investigation, to support these results. Lastly, this investigation proposes a simplified electrostatic model that explains further the formations of clusters, which were promoted by propagation of displacing fluids.
1.0 INTRODUCTION Substantial reserves of heavy oils and bitumen are reported to sit within the reach of existing oilfields. Meyers et al.1 reported an estimated volume of extractable heavy oils of 3396 billion barrels of original oil-in-place (OOIP) of which 30 billion barrels are included as prospective additional oil. The main challenge of heavy oil recovery lies primarily on the physical properties of heavy oils, i.e. its asphaltenic, dense and viscous nature. During the primary production, a small fraction of the oil-inACS Paragon Plus Environment 2
Page 3 of 38
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
place (OIP) is recovered using the reservoir internal energy. Upon which, it is routinely injected a cheap fluid (water and/or gas) that keeps not only the reservoir pressure, but also enables a further increment in oil. However, the high viscosity and low mobility of the heavy oil lower the recovery efficiency at this production stage. Thus, mature technologies including thermal methods, whose mechanism lies upon viscosity reduction by heat injection, are often considered. For example, thermal techniques, are reported to account for over 40% of U.S. enhanced oil recovery (EOR) production2. However, when the candidate formation is either (i) a formation with large depth (> 1,000 m) and/or (ii) a formation with a thin reservoir (
