Research advancement in polymer flooding for Enhanced Oil Recovery (EOR) has been growing over the last decade. This growth can be tied to increased funding towards the development of superior polymers such as hydrophobically associating polymers when oil prices were high and increasing concern that "easy oil" has been exploited with the focus now on "difficult to extract" oil. The use of hydrophobically associating polymers for EOR was discussed along with its limitations. In this context, the improved rheological properties of associating polymers cannot only be linked to the molecular structures arising from different synthesis methods. Equally, external parameters similar to conditions of oil reservoirs affect the rheological properties of these polymers. As such, this review placed critical emphasis on the molecular architecture of the polymer and the synthesis route and this was linked to the observed rheological properties. In addition, the influence of some key oilfield parameters such as temperature, salinity, pH, and reservoir heterogeneity on the rheological behaviour of hydrophobically associating polymers were reviewed. In this respect, the various findings garnered in understanding the correlation between polymer rheological properties and oilfield parameters were critically reviewed. For associating polymers, an understanding of the molecular architecture (and hence the synthesis method) is crucial for its successful design. However, this must be theoretically linked to the preferred EOR application requirements (based on oilfield parameters).

The application of superabsorbent polymer hydrogels in the oil and gas industry for reservoir and well management is gaining more traction. In this study, the swelling performance and adsorption kinetics of two commercial superabsorbent polymer hydrogels-poly(acrylamide-co-acrylic acid) potassium salt and sodium polyacrylate-were evaluated based upon their stimuli response to pH and salinity at varying temperature and reaction time periods. Characterisation and evaluation of the materials were performed using analytical techniques-optical microscopy, scanning electron microscopy, thermal gravimetric analysis and the gravimetric method. Experimental results show that reaction conditions strongly influence the swelling performance of the superabsorbent polymer hydrogels considered in this study. Generally, increasing pH and salinity concentration led to a significant decline in the swelling performance of both superabsorbent polymer hydrogels. An optimal temperature range between 50 and 75 °C was considered appropriate based on swell tests performed between 25 c to 100 °C over 2-, 4-and 6-h time periods. These findings serve as a guideline for field engineers in the use of superabsorbent polymer hydrogels for a wide range of oilfield applications. The study results provide evidence that the two superabsorbent polymer hydrogels can be used for petroleum fraction-saline water emulsions separation, reservoir zonal isolation, water shutoff and cement plugging applications.

Sand failure may result in the production of formation sand at the same time the formation fluids are being produced. This work examines the effects of some commonly used oilfield chemicals, specifically, biocide, corrosion inhibitor and scale inhibitor, on the geomechanical strength of reservoir rocks such as limestone and sandstone. A combination of rock mechanical testing, grain size distribution analysis and analytical techniques are used to establish and define the effects of these chemicals on grain dissolution and unconstrained compressive strength. The results suggest that some interactions such as chemical reaction (dissolution/precipitation) between the oilfield chemicals and the two different types of reservoir formation rocks and transport of grains occurred following the exposure of the rocks to the oilfield chemicals leading to the weakening of the grain fabrics rocks and consequent reduction in unconfined compressive strength. The implications of the results for the strength reduction and sand production are discussed.

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Value of information is a widely accepted methodology for evaluating the need to acquire new data in the oil and gas industry. In the conventional approach to estimating the value of information, the outcomes of a project assessment relate to the decision reached following Boolean logic. However, human thinking logic is more complex and include the ability to process uncertainty. In addition, in value of information assessment, it is often desirable to make decisions based on multiple economic criteria, which, independently evaluated, may suggest opposite decisions. Artificial intelligence has been used successfully in several areas of knowledge, increasing and enhancing analytical capabilities. This paper aims to enrich the value of information methodology by integrating fuzzy logic into the decisionmaking process; this integration makes it possible to develop a human thinking assessment and coherently combine several economic criteria. To the authors' knowledge, this is the first use of a fuzzy inference system in the domain of value of information. The methodology is successfully applied to a case study of an oil and gas subsurface assessment where the results of the standard and fuzzy methodologies are compared, leading to a more robust and complete evaluation.