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h i g h l i g h t sWe propose the GAF decision support methodology for optimal site selection. The GAF methodology builds decision support from multi-dimensional imprecise data. We present a real-case application for biogas facilities at Ringkøbing-Skjern, Denmark. a b s t r a c tThe purpose of this paper is to model the multi-criteria decision problem of identifying the most suitable facility locations for biogas plants under an integrated decision support methodology. Here the Geographical Information System (GIS) is used for measuring the attributes of the alternatives according to a given set of criteria. Measurements are taken in interval form, expressing the natural imprecision of common data, and the Fuzzy Weighted Overlap Dominance (FWOD) procedure is applied for aggregating and exploiting this kind of data, obtaining suitability degrees for every alternative. The estimation of criteria weights, which is necessary for applying the FWOD procedure, is done by means of the Analytical Hierarchy Process (AHP), used jointly with the LLSM-AHP for the estimation of upper and lower bounds for the weights. Then, a combined AHP-FWOD methodology allows identifying the more suitable sites for building biogas plants. We show that the FWOD relevance-ranking procedure can also be successfully applied over the outcomes of different decision makers, in case a unique social solution is required to exist.The proposed methodology can be used under an integrated decision support frame for identifying the most suitable locations for biogas facilities, taking into account the most relevant criteria for the social, economic and political dimensions.

During the early 21st century, nanotechnology has stood strong in the oil and gas industry, with many applications that have gone from laboratory and numerical simulation studies to successful trial applications in the field. In this Review, recent advances of nanofluid and nanoparticle applications in real environments of the oil and gas industry are presented. These applications cover more than 20 wells in Colombia that have been treated to overcome different formation damage mechanisms, such as asphaltene precipitation/deposition, fines migration, and inorganic scale deposition. Also, different approaches to enhance drilling fluids in Canada, Brazil, Iran, and Colombia are examined. In the case of improved oil recovery (IOR), different applications are discussed, including strategies to improve the productivity of heavy crude oil and extra-heavy crude oil reservoirs through enhanced mobility and hydraulic fracturing in Colombia, a field trial for water shutoff in Csongrad-3 formation in the Algyo field in Hungary, nanocapsules injection for wettability alteration, applications of gas injection (N2 and CO2) in the presence of nanoparticles in Austin chalk, Buda and Eagle Ford formations in the United States, and the use of nanoparticle-assisted foams for well dewatering in China. For secondary and tertiary recovery, we explore the design and implementation of A-Dots and carbon quantum dots as tracers in Saudi Arabia and Colombia, respectively, hydrophobic nanoparticles as drag reducers in injector wells in China, and nanofluids for enhancing chemical enhanced oil recovery processes in southern Colombia. It is worth mentioning that the results were based on oil production and reserves derived from production curves and analysis of the declination curves. Finally, challenges and perspectives of the role of nanotechnology in the oil and gas industry today are discussed.

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In this position paper we propose a consistent and unifying view to all those basic knowledge representation models that are based on the existence of two somehow opposite fuzzy concepts. A number of these basic models can be found in fuzzy logic and multi-valued logic literature. Here it is claimed that it is the semantic relationship between two paired concepts what determines the emergence of different types of neutrality, namely indeterminacy, ambivalence and conflict, widely used under different frameworks (possibly under different names). It will be shown the potential relevance of paired structures, generated from two paired concepts together with their associated neutrality, all of them to be modelled as fuzzy sets. In this way, paired structures can be viewed as a standard basic model from which different models arise. This unifying view should therefore allow a deeper analysis of the relationships between several existing knowledge representation formalisms, providing a basis from which more expressive models can be later developed.Recent advances in Psychology and Neurology are providing relevant results for the development of decision making models. The human brain has specifically and successfully evolved to manage complex, uncertain, incomplete, and even apparently inconsistent information. For example, neurologists have shown that the part of the brain taking care of making up the last decision is different to the part of the brain in charge of the previous rational analysis of alternatives, being the first part associated to emotions (see, e.g., [6],[7]). A number of similar results within neurology (see, e.g.

In the Oil & Gas industry, preserve filtration properties of the drilling fluids based on the rheological behavior under prolonged exposure time, and temperature (aging process) are the most important challenges due to the implications that lead to the formation damage. The polymers as xanthan gum (XG) suffer degradation due to the drilling processes losing their viscosifying capacity, solid suspension, and subsequent the filtration control since the effective build-up of the mudcake is not possible. In this way, this study aims to evaluate the effect of SiO2 nanoparticles on thermal stability under thermal rolling process in the filtration properties through of the rheological behavior in bentonite-free water-based mud (BFWBM). Two kinds of SiO2 nanoparticles were evaluated: (1) synthesized through the sol-gel method and (2) fumed silica nanoparticles. SiO2 nanoparticles were characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and zeta potential (ZP). The SiO2 -XG interactions were evaluated through polymer adsorption onto nanoparticles using a batch-mode, rheological studies, and evaluation of thermal stability. Additionally, the effect of SiO2 nanoparticles on basic (pH, density, solid content, rheological, and filtration) properties in BFWBM were studied according to American Petroleum Institute (API) standard after aging through hot roller oven at 77°C for 16 hours. Results of adsorption experiments showed that adsorption isotherms of XG polymer onto silica followed a Type I behavior and these were modeled using solid-liquid equilibrium (SLE) model, showing an uptake adsorbed higher for the SiC nanoparticle than other materials. The rheological conduct of XG polymer - SiO2 nanoparticles system showed a pseudoplastic behavior with a high performance of SiC nanoparticles with an increase of 15% of the viscosity and inhibition of the degradation of the 32.2% compared with the polymer sample without nanoparticles. Also, the experimental results showed that the addition of SiO2 nanoparticles did not alter the basic properties such as pH, density, and solid content. Meanwhile, SiC increased the plastic viscosity (PV), yield point (YP), yield stress (YS), and gel strength of the drilling fluid and reduced the filtration volume and the mudcake thickness of the drilling fluid after the thermal rolling process. Also, these nanoparticles showed the highest increase of the VP, YP, and YS by 12, 19, and 100%, respectively. Additionally, SiC nanoparticles reduced the spurt loss and total filtration volume by 67 and 49%, respectively. Nanoparticles strengthened the hydrogen bonds with polymer preventing the hydrolysis.

The main objective of this study is to develop nanotechnology-based materials, specifically carbon quantum dots (CQDs), as alternative nonpolluting, nontoxic, and easily manipulated tracers for the oil industry using an easy and rapid synthesis from Mortinõ (Vaccinium meridionale Swartz) extract, a process that was evaluated in the laboratory and subjected to a Colombian oil field trial. The CQDs were synthesized using an easy and rapid microwave-assisted carbonization (MWC) methodology involving aqueous natural extraction in the presence of an organic nitrogen precursor. A displacement test at reservoir conditions in a porous media was used for evaluating CQDs retention, and a breakthrough curve with a CQDs saturation of around 1 pore volume injected was obtained, indicating that the CQDs could be completely removed from the porous media with null retention due to a poor interaction with the formation and preferential affinity to the aqueous phase. Fluorescence tests showed that quantification of the synthesized CQDs could be achieved for up to 1 ng L −1 . Coreflooding tests at reservoir conditions were performed under two scenarios: (1) monophase coreflooding (the core was saturated with water) and (2) biphasic coreflooding (at residual saturation of crude oil). The results showed that the CQD S behave excellently within these outlines and are not affected by the presence of crude oil, obtaining a breakthrough that is almost ideal for a tracer. A CQDs field trial in Colombia was conducted by injecting 20 kg of the nanomaterial at a concentration of 500 000 mg L −1 . The CQDs were analyzed in 10 producer wells, showing that they are useful as interwell tracers and the different interconnections between the different wells in the field were stablished. This study places the technology at a technology readiness level (TRL) of around 8, opens a broader landscape for the use of nanotechnology in the oil industry, and maintains Colombia as a pioneer in the application of nanoparticles and nanofluids under field conditions.