Isa M. Tan

The Synthesis and Performance of Sodium Methyl Ester Sulfonate for Enhanced Oil Recovery

Abstract Due to the high cost of surfactant production caused by petrochemical feedstocks, much attention has been given to nonedible vegetable oils as an alternative source of feedstock. A new nonedible oil-derived surfactant based on the Jatropha plant is synthesized. A single-step route was used for synthesizing sodium methyl ester sulfonate (SMES) for enhanced oil recovery application. The performance of the resultant surfactant was studied by measuring the interfacial tension between the surfactant solution and crude oil and its thermal stability at reservoir temperature. The SMES showed a good surface activity, reducing the interfacial tension between the surfactant solution and crude oil from 18.4 to 3.92 mN/m. The thermal analysis of SMES indicates that 26.1% weight loss was observed from 70°C to 500°C. The advantage of the new SMES is the low cost of production, which makes it a promising surfactant for enhanced oil recovery application and other uses.

Development of a New Polymeric Surfactant for Chemical Enhanced Oil Recovery

Abstract This work presents a new alkaline–surfactant (AS) flooding formulation that replaces and improves the traditional alkaline–surfactant–polymer (ASP) flooding slug. With the design of a cost-effective AS slug, a new series of polymeric surfactants was produced based on agriculture material. In this article, the polymeric surfactant was produced by a graft polymerization process using several surfactant-to-acrylamide ratios. This surfactant was designed to graft the sulfonated group to the polymer backbone as one component system for interfacial tension (IFT) reduction and viscosity control. The performance of the resultant surfactants was studied in the presence and absence of sodium carbonate as an alkaline agent at reservoir temperature of 90°C. The feasibility of applying the AS formula was based on IFT measurement between crude oil and AS solution and viscosity tests. As a result, the ratio of 1:0.5 (S:A) was selected as the optimum ratio for IFT reduction and viscosity control. A combination of alkali and surfactant with a concentration of 0.8 and 0.4% was found to significantly reduce the IFT while maintaining the desired viscosity of the solution.

A New Approach to Low-Cost, High Performance Chemical Flooding System

This paper presents a new Acid-Alkali-Surfactant (AAS) flooding formulation as an alternative to conventional alkaline/surfactant/polymer (ASP) process. It is a cost-effective formula that is able to overcome precipitation problems prevalent with ASP flooding when natural sea water was used. The acid was evaluated in an AAS formulation using sodium carbonate and introducing a new polymeric surfactant derived from Jatropha oil. The feasibility of applying the new AAS formula was demonstrated by a series of experiments involving fluid compatibility test with natural sea water having a large quantity of divalent metal cations, interfacial tension between Angsi crude oil and AAS solution, surfactant adsorption, and core flood using Berea core samples. The acid effectively prevented divalent metal cations from precipitating and all solutions remained clear for 90 days at 90oC. The optimum acid concentration was found to be proportional to alkali concentration in the ratio of 1.66:1. A combination of the new system was found to significantly reduce the IFT and the adsorption level of the surfactant. The best chemical concentrations were then validated in core flood tests using various alkali and surfactant concentrations. The optimum alkali and surfactant concentrations were confirmed as 0.6% and 0.6% respectively. Using the optimum concentrations, another series of core flood tests were conducted by changing the injection volume. Only a small incremental recovery was obtained with slugs higher than 0.5 PV. Injection of 0.5 PV of the formulated slug followed by chase water produced an additional 18.8% OOIP over water flood, accomplishing a total oil recovery of 77.3% OOIP. This makes the new AAS formula an attractive and cost-effective agent for CEOR particularly for offshore field application.

Oleate Ester-Derived Nonionic Surfactants: Synthesis and Cloud Point Behavior Studies

The synthesis and cloud point behavior of high oleate ester-derived nonionic surfactants are now reported. The effect of various polyethoxylate chain lengths (polyethylene glycol with 7, 11, and 16 units of ethylene oxide (EO) monomer) as the surfactants hydrophilic head on the cloud point was investigated. The effect of varying amounts of sodium chloride and five different ionic surfactants on the cloud points of the synthesized nonionic surfactants were also presented. When the chain length of polyethoxylate increased, the cloud point of the synthesized nonionic surfactant also increased, ranging from 16°C, 43°C, and 64°C for 7, 11, and 16 EO units, respectively. Increments in sodium chloride concentration depressed the cloud point values of the synthesized nonionic surfactants linearly. The addition of ionic surfactants elevated the cloud points of the synthesized nonionic surfactant. However, in the presence of sodium chloride, the cloud point of the mixed ionic-nonionic solution was suppressed and anincrease in ionic surfactant concentration was required to elevate the cloud point. It was also found that the cloud points of synthesized surfactants can be raised up to 95°C in the presence of 4wt% NaCl solution.

Empirical Correlations for Viscosity of Polyacrylamide Solutions with the Effects of Salinity and Hardness

A series of experiments have been conducted to characterize and quantify the effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. A set of correlations were developed to predict the viscosity of polymer solutions. These correlations consider the individual and combined effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. The power-law model for the viscosity behavior has been modified to accommodate the influence caused by these three factors. Nonlinear regression was performed on the experimental data to develop the proposed correlations. The proposed correlations can be integrated into any reservoir simulator for polymer injection and should prove useful for the initial screening for the selection of the polymer for enhanced oil recovery applications in oil reservoirs.

Novel Surfactant for the Reduction of CO2/Brine Interfacial Tension

The synthesis of novel CO2 philic surfactant using maleic anhydride and dipropylene tertiary butyl alcohol is reported. The synthesis involved the esterification of maleic anhydride to produce bis(2-(2-(tert-butoxy)propoxy)propyl) maleate and subsequent sulfonation of the esterified product. Para toluene sulfonic acid was employed as catalyst for the esterification reaction. The esterification reaction was optimized for the maximum yield of 98% of bis(2-(2-(tert-butoxy)propoxy)propyl) maleate. The esterification reaction kinetics employing heterogeneous catalyst were also studied. Although this is a bimolecular reaction, a first order reaction kinetics with respect to acid has been observed. The activation energy was found to be 58.71 kJ/mol. The diester was followed by the sulfonation process and a yield of 85% of surfactant was achieved. The synthesized surfactant successfully lowered down the IFT between CO2/brine to 1.93 mN/m. This surfactant has a great potential to be used for CO2-EOR applications.

Synthesis of a New CO2 Philic Surfactant for Enhanced Oil Recovery Applications

The synthesis of CO2 philic surfactant using maleic anhydride and 4-tert-butylbenzyl alcohol is reported. We reacted maleic anhydride with 4-tert-butylbenzyl alcohol to form bis(4-(tert-butyl)benzyl) fumarate and sulfonated the produced diester. The esterification reaction was optimized for a maximum yield of 98% of bis(4-(tert-butyl)benzyl) fumarate. First-order reaction kinetics with respect to acid was observed. The activation energy was found to be 55.62 kJ/mol. The sulfonated product of diester was obtained by the sulfonation reaction and the yield of 82% of surfactant was achieved. The in-house developed surfactant effectively lowered down the IFT between CO2/brine to 4.2 mN/m. This surfactant is targeted for CO2-EOR applications.

The Application of a New Polymeric Surfactant for Chemical EOR

Crude oil makes a major contribution to the world economy today. The provision of heat, light, and transportation depends on oil and there has not been yet a single energy source to replace crude oil that is widely integrated. Moreover, the global economy currently depends on the ability to acquire the energy required and it is indisputable that oil is the main contributor to this demand. Currently, there is no an energy source available that could compete with oil, making the world, and mainly the high energy consumers to rely on countries with large reserves (Energy Information Administration, 2003).

Design and Application of a New Acid-Alkali-Surfactant Flooding Formulation for Malaysian reservoirs

A new Acid-Alkali-Polymeric Surfactant (AAPS) flooding formulation has been developed to overcome the precipitation problems caused by the divalent metal cations prevalent with conventional ASP flooding. The acid was evaluated in an acidalkali-surfactant formulation using sodium carbonate and introducing a new polymeric surfactant derived from Jatropha oil. The effect of the new formula on IFT, viscosity, and oil recovery was studied using natural seawater having a large quantity of divalent metal cations. The tolerance of the AAPS towards natural untreated sea water was monitored for 90 days at 90 C. No precipitations were formed with the acid additive, while precipitations were always generated without the acid. A combination of the new system was found to significantly reduce the IFT between Angsi crude oil and AAPS solution. The most outstanding feature of the AAPS formulation lies in its viscosity insensivity towards an increasing alkali concentration up to 1.2%. Core flood tests with alkali and acid concentrations of 0.6% and 1% respectively confirmed an optimum surfactant concentration of 0.6%. Using the optimum AAPS concentrations, another series of core flood were conducted by changing the injection volume. Only a small incremental recovery was obtained with AAPS slugs higher than 0.5 PV. Injection of 0.5 PV of the formulated AAPS slug followed by chase water produced an additional 18.8% OOIP over water flooding. The benefit of the new system is the use of seawater rather than softened water while maintaining the desired slug properties. Introduction In Malaysia and many other countries, most mature reservoirs are already waterflooded, or are presently being subjected to secondary and tertiary recovery processes. In Malaysian oil reservoirs, only about 36.8% of original oil in place (OOIP) is produced through the entire life of mature reservoirs that have been developed under conventional methods (Hamdan et al., 2005). A significant amount of the hydrocarbon would not be recovered utilizing the current production strategies, and that has motivated Malaysia to attempt Enhanced Oil recovery (EOR). Recognizing the potential of EOR in the fields, the national oil company (PETRONAS) endorsed a comprehensive EOR screening in year. The screening study on seventy two reservoirs has identified almost a billion barrels of additional reserves can be achieved through EOR (Samsudin et al., 2005). The Chemical Enhanced Oil Recovery (CEOR) was identified as one of the key EOR processes that have good potential for field implementation to increase ultimate recovery in Malaysian oil fields (Othman et al., 2007). Chemical EOR processes are being considered for large field applications with recent high price of crude oil (Ibrahim et al, 2006). These include surfactant (S), surfactant-polymer (SP), and alkali-surfactant-polymer (ASP). ASP flooding has been used widely in a field application with great success (Pitts et al., 2006; Pratap and Gauma, 2004; Clara et al., 2001; Wang, et al., 1997; Hong-Fu, et al., 2008). It uses the benefits of the three flooding methods simultaneously and oil recovery is sufficiently improved by decreasing the interfacial tension (IFT), increasing the capillary number, and improving the mobility ratio (Pingping et al., 2009). Despite the potential of ASP flooding, the approach towards ASP in Malaysia has taken a conservative route. This could be attributed mostly to the fact that all of the producing fields are located offshore. Offshore environment poses a number of challenges (Hamdan et al., 2005). One of the primary considerations for chemical flooding application in Malaysia is the use of seawater rather than softened water as injection water (Hamdan et al., 2005). However, using seawater adds other problems to the process. Adding alkaline agents such as sodium carbonate or sodium hydroxide will result in precipitation of the anions with divalent metal cations (calcium, magnesium, potassium. etc) in the seawater. The alkali has also a detrimental effect on polymer performance and in

Experimental investigation of the effect of different process variables on the viscosity of sulfonated polyacrylamide copolymers

Increasing the viscosity of injected water by the addition of polymer improves the displacement efficiency during the water flooding process. In this study, a sulfonated polyacrylamide copolymer has been added to salt water. Several parameters, such as polymer concentration, shear rate, NaCl concentration, molecular weight and sulfonation degree, have a significant effect on the polymer solution viscosity. The main objective of this paper is to investigate how the polymer solution viscosity varies with changes in the input parameters so as to identify the relative importance of these parameters. This paper incorporates the Design of Experiments technique using Taguchi’s method and the Analysis of Variance (ANOVA) to investigate the effect of process variables on the viscosity of a polymer solution. Five input parameters and six possible interactions have been investigated. The analysis of the experimental results revealed that two input parameters, namely, polymer concentration and shear rate, have the most significant impact on polymer viscosity. Two strong interactions were observed in the (1) NaCl concentration and sulfonation degree and (2) molecular weight and NaCl concentration studies. The results show that the Taguchi method was successful in identifying the main effects and interaction effects. ANOVA further buttresses the results from Taguchi’s method by showing a strong similarity in its results.