Syed Mohammad Mahmood

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.

Effect of Aging, Antioxidant, and Mono- and Divalent Ions at High Temperature on the Rheology of New Polyacrylamide-Based Co-Polymers

The viscosity of four new polymers was investigated for the effect of aging at high temperature, with varying degrees of salinity and hardness. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; AN132 VHM; SUPERPUSHER SAV55; and THERMOASSOCIATIF copolymers. All polymer samples were aged at 80 °C for varying times (from zero to at least 90 days) with and without isobutyl alcohol (IBA) as an antioxidant. To see the effect of divalent ions on the polymer solution viscosity, parallel experiments were performed in a mixture of CaCl2-NaCl of the same ionic strength as 5 wt % NaCl. The polymers without IBA showed severe viscosity reduction after aging for 90 days in both types of preparation (5 wt % NaCl or CaCl2-NaCl). In the presence of IBA, viscosity was increased when aging time was increased for 5 wt % NaCl. In CaCl2-NaCl, on the other hand, a viscosity reduction was observed as aging time was increased. This behavior was observed for all polymers except AN132 VHM.

Comparison of neuro-fuzzy network and response surface methodology pertaining to the viscosity of polymer solutions

This study has utilized the response surface methodology (RSM) and adaptive neuro-fuzzy inference system (ANFIS) approaches for the modeling of polymer solution viscosity. In the absence of reports in the previous study on applying these two approaches, the main objective of this study has been to compare the performance of these methods toward the viscosity modeling of a polymer solution. By utilizing RSM technique, the effects of three independent parameters including shear rate, polymer concentration, and sodium chloride concentration on viscosity of polymer solution were examined. The RSM results showed that all the parameters were not equally important in the polymer solution viscosity. Moreover, analysis of variance (ANOVA) was also carried out and indicated that there was no evidence of lack of fit in the RSM model. As a second approach for polymer solution viscosity modeling, ANFIS was utilized with two rules constructed based on the first-order Sugeno fuzzy approach and trained by back propagation neural networks algorithm. High coefficient of determination (R2) values ( >99%) showed that the prediction ability of both the ANFIS and RSM models was good enough for the response when the interpolation ability of the models was considered. In order to evaluate the extrapolation abilities of the two developed models, two data sets lying beyond the originally considered data were also taken into account. The results showed that their extrapolation predictive ability was poor. The reason could simply be the inherent behavior of the polymeric solution, i.e., the correlational structure seen in the sample used in the training step did not continue outside the sample space.

Assessment of Polyacrylamide Based Co-Polymers Enhanced by Functional Group Modifications with Regards to Salinity and Hardness

This research aims to test four new polymers for their stability under high salinity/high hardness conditions for their possible use in polymer flooding to improve oil recovery from hydrocarbon reservoirs. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; SUPERPUSHER SAV55; THERMOASSOCIATIF; and AN132 VHM which are basically sulfonated polyacrylamide copolymers of AM (acrylamide) with AMPS (2-Acrylamido-2-Methylpropane Sulfonate). AN132 VHM has a molecular weight of 9–11 million Daltons with 32 mol % degree of sulfonation. SUPERPUSHER SAV55 mainly has about 35 mol % sulfonation degree and a molecular weight of 9–11 million Daltons. FLOCOMB C7035, in addition, has undergone post-hydrolysis step to increase polydispersity and molecular weight above 18 million Daltons but it has a sulfonation degree much lower than 32 mol %. THERMOASSOCIATIF has a molecular weight lower than 12 million Daltons and a medium sulfonation degree of around 32 mol %, and also contains LCST (lower critical solution temperature) type block, which is responsible for its thermoassociative characteristics. This paper discusses the rheological behavior of these polymers in aqueous solutions (100–4500 ppm) with NaCl (0.1–10 wt %) measured at 25 °C. The effect of hardness was investigated by preparing a CaCl2-NaCl solution of same ionic strength as the 5 wt % of NaCl. In summary, it can be concluded that the rheological behavior of the newly modified co-polymers was in general agreement to the existing polymers, except that THERMOASSOCIATIF polymers showed unique behavior, which could possibly make them a better candidate for enhanced oil recovery (EOR) application in high salinity conditions. The other three polymers, on the other hand, are better candidates for EOR applications in reservoirs containing high divalent ions. These results are expected to be helpful in selecting and screening the polymers for an EOR application.

A rigorous approach to analyze bulk and coreflood foam screening tests

There are many uses of foam in petroleum industry yet there is no dependable industry standard on screening a wide variety of foaming surfactants available for a particular application. This study aims to fill this gap. Three anionic foaming surfactants were characterized and tested with the two commonly used screening methods at room temperature and oil-free conditions. The results were comprehensively analyzed to compare their foaming performance. The analysis is more comprehensive than previously reported and covers many foaming attributes (peak and residual foamability, foam longevity, and rate of decay). The three surfactants for possible foaming applications in sandstone reservoirs were selected, and their foamability and foam stability performances were experimentally determined by bulk foam stability tests and coreflood tests. All methods agreed on the ratings of the three surfactants for peak and residual foaming attributes as follows in the following order of effectiveness: MFOMAX, AOS, and ENORDET. However, they broadly disagreed on ratings for other characteristics including onset of foaming, the time required for peak foaming, foam longevity, and foam decay rate. In conclusion, the screening tests revealed that the simple and faster bulk foam stability test could be cautiously used to screen out the poor performers to narrow the range of acceptable surfactants. Also, the new and rigorous analysis technique presented in this paper offers more insight than conventional half-life test.Graphical abstract

Assessing the application of miscible CO2 flooding in oil reservoirs: a case study from Pakistan

Miscible carbon dioxide (CO2) flooding has been recognized as a promising approach to enhance the recovery of oil reservoirs. However, depending on the injection strategy and rock/fluid characteristics, efficiency of the miscible CO2 flooding varies from reservoir to reservoir. Although, many studies have been carried out to evaluate the performance of the miscible CO2 flooding, a specific strategy which can be strictly followed for a hydrocarbon reservoir has not been established yet. The aim of this study is to assess one of Pakistan’s oil reservoirs for miscible CO2 flooding by applying a modified screening criterion and numerical modeling. As such, the most recent miscible CO2 screening criteria were modified, and a numerical modeling was applied on the prospective reservoir. Based on the results obtained, South oil reservoir (S3) is chosen for a detailed assessment of miscible CO2 flooding. It was also found that implementation of CO2 water-alternating gas (CO2-WAG) injection at early stages of production can increase the production life of the reservoir.

Examination and Improvement of Salama Model for Calculation of Sand Erosion in Elbows

Sand erosion is a problem recognized in many facilities and piping components used in production, treatment, and transportation of oil and gas. Proper controlling of sand erosion requires early prediction at different conditions and within various ranges of flow parameters. Numerous models and correlations are available for sand erosion prediction in varies components. The applicability and accuracy of the available models depends on many factors such as the range of conditions and the number of parameters that are taken into account in developing the model. One of the models widely used for sand erosion prediction is Salama model, which is used for calculation of sand erosion in elbows and tees. In spite of Salama model’s simplicity, it is not recommended to use in many cases due to decrease in accuracy. Salama model accuracy, in general, decreases when it is applied to viscous fluids flow and low gas–liquid-ratio multiphase flow. In this paper, the discrepancy of Salama model with field data was confirmed by comparing its output with published measured data. The model was, then, improved by comparing its results with three sets of measured sand erosion data for pure gas, high gas–liquid-ratio fluids, and low gas–liquid-ratio fluids. The model improvement results in three models for prediction of sand erosion in elbows with higher accuracy.

Comparison Study on Anionic Surfactants and Mixed Surfactant Behavior in SAG Foam Process

In order to increase the gas injection’s sweep efficiency, the assisted foam process has been introduced. The foam can be created when the gas phase moves through surfactant solution under certain conditions. Although several surfactant types are able to generate foam through porous media, finding the appropriate surfactant to achieve the best performance is the goal of foam-assisted process. In this study, the behavior of two different types of surfactant was investigated. However, there are various surfactant types; the objective of this study was to elaborate the performance of mixed surfactant and an anionic surfactant in porous media. To achieve this target, the static tests, as well as dynamic tests, were conducted in the oil-free medium. For dynamic test, core flooding was conducted which included core sample, core flooding apparatus, two surfactant types, and nitrogen as injected gas. The static tests were interpreted in terms of foam height, while the dynamic experiments were analyzed in terms of liquid recovery and pressure drop. The results show that the mixed surfactant has better efficiency compared to anionic surfactant. Furthermore, the behavior of foam reveals the consistency of the dynamic experiments with static experiments.

The effects of salt, particle and pore size on the process of carbon dioxide hydrate formation: A critical review

Hydration is an alternative method for CO2 capture. In doing so, some researchers use porous media on an experimental scale. This paper tries to gather the researches on the formation of CO2 hydrate in different types of porous media such as silica sand, quartz sand, Toyoura, pumice, and fire hardened red clay. This review has attempted to examine the effects of salt and particle sizes as two major factors on the induction time, water to hydrate conversion, gas uptake (or gas consumption), and the rate of CO2 hydrate formation. By performing a critical assessment of previous research works, it was observed that the figure for the gas uptake (or gas consumption) and water to hydrate conversion in porous media was decreased by increasing the particle size provided that the pore size was constant. Although, salt can play a role in hydrate formation as the thermodynamic inhibitor, the results show that salt can be regarded as the kinetic growth inhibitor and kinetic promoter. Because of the fact that the gas ...