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Robert J Pugh - One of the best experts on this subject based on the ideXlab platform.

Katarina Theander - One of the best experts on this subject based on the ideXlab platform.

George J. Hirasaki - One of the best experts on this subject based on the ideXlab platform.

  • Determination of the Active Soap Number of Crude Oil and Soap Partitioning Behavior
    Energy & Fuels, 2016
    Co-Authors: Lei Ding, Guicai Zhang, Jacob Behling, Jose Luis Lopez-salinas, Jijiang Ge, Maura Puerto, George J. Hirasaki, Clarence A. Miller
    Abstract:

    The optimal salinity of the alkali/Surfactant/crude oil system in an alkali/Surfactant/polymer (ASP) flooding process was found previously to be a function of the Soap/Surfactant ratio. Therefore, the Soap number is of great importance in formulation design and simulation of ASP flooding processes for enhanced oil recovery. However, there is as yet no established way to quantitatively determine the amount of Soap in crude oil relevant to an ASP process. Soaps are the salts of fatty acids, a definition generalized here to include the salts of naphthenic acids. In this paper, we present a method to determine the amount of “active Soap”, which consists only of Soap that partitions into the aqueous phase at low ionic strength and transfers into the oleic phase at high ionic strength. Two fast and accurate methods, aqueous-phase potentiometric titration and two-phase colorimetric titration, were used to determine the water-soluble active Soap number (WSASN), a measure of the active Soap. Both methods were prov...

  • Alkaline/Surfactant/Polymer Processes: Wide Range of Conditions for Good Recovery
    Spe Journal, 2010
    Co-Authors: Clarence A. Miller, Robert Feng Li, George J. Hirasaki
    Abstract:

    This paper (SPE 113936) was accepted for presentation at the SPE/DOE Symposium on Improved Oil Recovery, Tulsa, 20–23 April 2008, and revised for publication. Original manuscript received for review 20 February 2008. Revised manuscript received for review 23 March 2009. Paper peer approved 8 September 2009. Summary Design of an alkaline/Surfactant/polymer (ASP) process requires knowledge of the amount of Soap formed under alkaline conditions from naphthenic acids in the crude oil. We show here for several crude oils that, when substantial acid is present, the acid number determined by nonaqueous-phase titration is approximately twice that found by hyamine titration of a highly alkaline aqueous phase used to extract Soaps from the crude oil. This acid number by Soap extraction should provide a better estimate than nonaqueous-phase titration because the extracted Soap interacts with the injected Surfactant to form Surfactant films and microemulsion droplets during an ASP process. In a previous paper (Liu et al. 2008), an unusually wide range of salinities of ultralow oil/water interfacial tensions (IFTs) was found for one alcohol-free crude-oil/anionic-Surfactant system under alkaline conditions where naphthenic Soaps were present. Solubilization results indicate that this favorable behavior exists with the same Surfactant blend and another crude oil. In the same paper, a 1D simulator for the ASP process was presented. Here, this ASP simulator has been used for various acid contents, injected-Surfactant concentrations, slug sizes, and salinities to show that high recoveries of waterflood residual oil (> 90%) can be expected for a wide range of near-optimal (Winsor III) and underoptimum (Winsor I) conditions for a constant-salinity process, even with relatively small slug sizes. A key factor leading to this good performance is development of a gradient in Soap/Surfactant ratio, which ensures that a displacement front with ultralow IFT forms and propagates through the formation. Similar high recoveries can be attained for certain Winsor II conditions but only for much larger slug sizes, owing to the tendency for Surfactant to partition into the oil phase and become retarded. Large dispersion, such as might be expected for field conditions, can reduce recovery significantly for small Surfactant slugs even for near-optimal and underoptimum conditions. However, this problem can be overcome by injecting the slug or drive at salinities below reservoir salinity, thereby creating a salinity gradient.

Clarence A. Miller - One of the best experts on this subject based on the ideXlab platform.

  • Determination of the Active Soap Number of Crude Oil and Soap Partitioning Behavior
    Energy & Fuels, 2016
    Co-Authors: Lei Ding, Guicai Zhang, Jacob Behling, Jose Luis Lopez-salinas, Jijiang Ge, Maura Puerto, George J. Hirasaki, Clarence A. Miller
    Abstract:

    The optimal salinity of the alkali/Surfactant/crude oil system in an alkali/Surfactant/polymer (ASP) flooding process was found previously to be a function of the Soap/Surfactant ratio. Therefore, the Soap number is of great importance in formulation design and simulation of ASP flooding processes for enhanced oil recovery. However, there is as yet no established way to quantitatively determine the amount of Soap in crude oil relevant to an ASP process. Soaps are the salts of fatty acids, a definition generalized here to include the salts of naphthenic acids. In this paper, we present a method to determine the amount of “active Soap”, which consists only of Soap that partitions into the aqueous phase at low ionic strength and transfers into the oleic phase at high ionic strength. Two fast and accurate methods, aqueous-phase potentiometric titration and two-phase colorimetric titration, were used to determine the water-soluble active Soap number (WSASN), a measure of the active Soap. Both methods were prov...

  • Alkaline/Surfactant/Polymer Processes: Wide Range of Conditions for Good Recovery
    Spe Journal, 2010
    Co-Authors: Clarence A. Miller, Robert Feng Li, George J. Hirasaki
    Abstract:

    This paper (SPE 113936) was accepted for presentation at the SPE/DOE Symposium on Improved Oil Recovery, Tulsa, 20–23 April 2008, and revised for publication. Original manuscript received for review 20 February 2008. Revised manuscript received for review 23 March 2009. Paper peer approved 8 September 2009. Summary Design of an alkaline/Surfactant/polymer (ASP) process requires knowledge of the amount of Soap formed under alkaline conditions from naphthenic acids in the crude oil. We show here for several crude oils that, when substantial acid is present, the acid number determined by nonaqueous-phase titration is approximately twice that found by hyamine titration of a highly alkaline aqueous phase used to extract Soaps from the crude oil. This acid number by Soap extraction should provide a better estimate than nonaqueous-phase titration because the extracted Soap interacts with the injected Surfactant to form Surfactant films and microemulsion droplets during an ASP process. In a previous paper (Liu et al. 2008), an unusually wide range of salinities of ultralow oil/water interfacial tensions (IFTs) was found for one alcohol-free crude-oil/anionic-Surfactant system under alkaline conditions where naphthenic Soaps were present. Solubilization results indicate that this favorable behavior exists with the same Surfactant blend and another crude oil. In the same paper, a 1D simulator for the ASP process was presented. Here, this ASP simulator has been used for various acid contents, injected-Surfactant concentrations, slug sizes, and salinities to show that high recoveries of waterflood residual oil (> 90%) can be expected for a wide range of near-optimal (Winsor III) and underoptimum (Winsor I) conditions for a constant-salinity process, even with relatively small slug sizes. A key factor leading to this good performance is development of a gradient in Soap/Surfactant ratio, which ensures that a displacement front with ultralow IFT forms and propagates through the formation. Similar high recoveries can be attained for certain Winsor II conditions but only for much larger slug sizes, owing to the tendency for Surfactant to partition into the oil phase and become retarded. Large dispersion, such as might be expected for field conditions, can reduce recovery significantly for small Surfactant slugs even for near-optimal and underoptimum conditions. However, this problem can be overcome by injecting the slug or drive at salinities below reservoir salinity, thereby creating a salinity gradient.

Gary A. Pope - One of the best experts on this subject based on the ideXlab platform.

  • Mechanistic Modeling of Alkaline/Surfactant/Polymer Floods
    SPE Reservoir Evaluation & Engineering, 2009
    Co-Authors: Hourshad Mohammadi, Mojdeh Delshad, Gary A. Pope
    Abstract:

    Alkaline/Surfactant/polymer (ASP) flooding is of increasing inter-est and importance because of high oil prices and the need to increase oil production. The benefits of combining alkali with Surfactant are well established. The alkali has very important benefits such as lowering interfacial tension (IFT) and reducing adsorption of anionic Surfactants that decrease costs and make ASP a very attractive enhanced-oil-recovery method, provided that the consumption is not too large and the alkali can be propagated at the same rate as the synthetic Surfactant and polymer. However, the process is complex, so it is important that new candidates for ASP be selected taking into account the numerous chemical reac-tions that occur in the reservoir. The reaction of acid and alkali to generate Soap and its subsequent effect on phase behavior is the most crucial for crude oils containing naphthenic acids. Mecha-nistic simulation of the ASP flood considering the chemical reac-tions, alkali consumption, and Soap generation and the effect on the phase behavior is the key to success of future field operations. Using numerical models, the process can be designed and opti-mized to ensure the proper propagation of alkali and effective Soap and Surfactant concentrations to promote low IFT and a favorable salinity gradient. In this paper, we describe the ASP module of the UTCHEM simulator, which is the University of Texas chemical compositional simulator, with particular attention to phase behav-ior and the effect of Soap on optimum salinity and solubilization ratio. Phase behavior data are presented for sodium carbonate and a blend of Surfactants with an acidic crude oil that followed the conventional Winsor phase transition with significant three-phase regions even at low Surfactant concentrations. The solubilization data at different oil concentrations were successfully modeled using Hand's rule. Optimum salinity and solubilization ratio were correlated with Soap mole fractions using mixing rules. ASP coreflood results were successfully modeled taking into account the aqueous reactions, alkali/rock interactions, and phase behavior of Soap and Surfactant. Mechanistic simulations give insights into the propagation of alkali, Soap, and Surfactant in the core and aid in future coreflood and field-scale ASP designs. Introduction There exists a rich literature on alkaline flooding. A majority of the papers discuss the importance of maintaining an effective level of alkalinity during the flood and alkali consumption because of chemical reactions or ion exchange (Bunge and Radke 1983, 1985; Novosad and Novosad 1984). The paper by Nelson et al. (1984) is the first that describes the benefits of combining alkali with Surfactants and demonstrates the effect of in-situ generated Surfactant referred to as Soap on phase behavior. Nelson et al. (1984) pointed out that the Soap generated is a distribution of relatively-high-molecular-weight carboxylic structures, which result in a very low optimal salinity. By adding a more water-soluble Surfactant, the region of optimum salinity could be raised to the desired level. Martin et al. (1985) studied the effect of different alkalis on mixtures of Surfactants, brine, and oil. The results showed that the presence of any alkali lowered the optimum salinity of the Surfactant. At a 1-wt% sodium alkali concentration, sodium silicate had the least effect, sodium carbonate was intermediate, and sodium hydrox-ide had the most effect. They found a linear relationship between the optimal salinity and milliequivalents of sodium present. Their conclusion was that the alkaline chemicals affect phase behavior because they provide an additional source of electrolytes. The cat-ions were effective in the order of potassium > sodium > ammonium. The alkali anion had very little effect on the phase behavior. More recently, Zhang (2006) and Liu et al. (2008) made an interesting observation based on the laboratory phase behavior study that the optimum salinity for a mixture of Surfactant, sodium carbonate, and crude oil containing naphthenic acids depends on the molar ratio of the in-situ generated Surfactant referred to as Soap to the synthetic Surfactant. A 1D simulator was developed to history match their oil recovery experiments in sandpacks. Both Soap and Surfactant components were tracked, but there was no chemical reaction modeled. Soap concentrations were calculated assuming that alkali was present and that the naphthenic acid in oil was completely converted to Soap based on the mass of oil present. The phase behavior was modeled using a partition coef-ficient between oil and water for the Soap/Surfactant mixture that is dependent on the ratio of optimum salinity to salinity. The challenge and success of an ASP flood depends on the simultaneous propagation of Surfactant and Soap in the reservoir and proper mobility control. If Soap moves ahead of the injected Surfactant, the phase behavior becomes overoptimum, and Soap partitions into the trapped oil and remains trapped until the injected Surfactant reaches that point and moves the phase behavior back toward the optimum salinity. On the other hand, if the injected Surfactant moves ahead of Soap, it will adsorb on the rock. The adsorbed Surfactant later gets partially desorbed when the high-pH alkali front reaches it. There are three categories of reactions that control the alkali consumption as follows: ion exchange, precipita-tion, and mineral dissolution. deZabala et al. (1982) and Bunge and Radke (1983, 1985) pointed out the importance of ion exchange on hydroxide ion uptake and the resulting lag between the injected Surfactant and alkali. Bung and Radke (1985) used mass action to model reversible hydroxide ion uptake by sodium/hydrogen ion exchange with minerals. Alkaline flooding is a complex process where IFT reduction is not always the key mechanism. Depending on the rock and crude properties, emulsification, and wettability alteration can play a major role in oil recovery from mixed-wet naturally fractured carbonates (Liu et al. 2008; Fathi et al. 2008; Zhang et al. 2008). Alkali coupled with Surfactant and polymers is also beneficial even if the crude oils have a low acid number when the major effects of alkalis are lowering IFT and decreasing Surfactant retention by increasing pH (Martin et al. 1985). Flaaten et al. (2008) studied sodium metaborate and sodium carbonate in their ASP corefloods. These alkalis gave pH values of approximately 11 at 1 wt% alkaline concentration and generated Soap for acidic crude oils. A major advantage of sodium metaborate species was their tolerance to divalent cations. This significant finding expands the application of ASP flooding to reservoirs with high salinity and hardness and formations with anhydrite minerals (Zhang et al. 2008). In this paper, laboratory phase behavior data are presented for a mixture of Surfactant/alkali/acidic crude oil. The effect of Soap on the phase behavior is modeled successfully. Sodium carbon-ate chemistry was incorporated in an in-house chemical flooding simulator to model both phase behavior and coreflood results.