NANOSTRUCTURES MANAGEMENT TECHNOLOGY TO REDUCE THE FIRE RISK IN THE OIL AND GAS INDUSTRY: PERFORMANCE, FEATURES AND IMPLEMENTATION

Oil and gas enterprises are characterized by an increased ﬁ re risk. There is high probability of occurrence and spread of large ﬁ res when oil production and processing, transportation and storage of oil products occurs. There is high probability of large ﬁ res during the oil production, oil processing and during the transportation and storage of petroleum products. New materials created using nanotechnology principles are needed to improve the efﬁ ciency of ﬁ re prevention and extinguishing systems. The technology for controlling the properties and performance characteristics of nanoﬂ uids based on liquid hydrocarbons and water is based on the methods of functionalization and interaction of clusters of the base liquid and multilayer carbon nanotubes, methods for stabilizing nanoﬂ uids, for changing the thermophysical, rheo-logical and electrostatic properties of substances and materials on their basis. The proposed technology makes it possible to create nanomaterials based on various scenarios for the development of emergency situations and to apply them to reduce ﬁ re risk at oil and gas facilities.


INTRODUCTION
The development of the oil and gas complex is related to the unstable demand of the world market, the growth of capital investments in the industry, the low level of profi tability caused by the state's require-ments for labor protection and environmental safety, the need to process raw materials with worsening commodity indicators [1]. The development trends of the oil and gas industry are an increase in the share of "heavy" oil in total production, an increase in the number of drilling rigs from large depths, an expansion of the geography of production towards the northern territories with diffi cult climatic conditions [2], a shift in priorities towards oil refi ning [3]. The methodology of fi re risk assessment in oil and gas refi neries and related industries includes the de-scription of process control tools and emergency systems, identification of hazards, scenarios and fre-quency of incidents, simulation of consequences and assessment of the impact of potential accidents and fi res. Common emergencies and complications in the extraction, transportation, processing of petroleum and petroleum products are strait fi res, fl ares, hydrocarbon fl ames, the formation of a fi reball, the combustion of a vapor cloud under pressure. The most dangerous of them occur on land tanks with the subsequent ignition of oil or oil products with fi re and complete destruction. Partial destruction and leaks from process equipment and pipelines are most likely [4]. When implementing measures to reduce fi re risk, restrictions arise due to the "growth limits" of modern fi re safety technologies, which are associated with a number of factors: • the impossibility of changing physical properties (evaporation rate, surface tension, viscosity, static electrifi cation, etc.) when handling substances and materials without the use of technical solutions that make signifi cant changes in the process parameters; • problems of ensuring the required values of thermal conductivity, adhesive strength, thermal stability of thermal protection means and intumescent fi re retardant compositions for metal structures at tem-perature conditions corresponding to the conditions of fl are hydrocarbon combustion; • limited possibility to use materials with high fi re-extinguishing effi ciency and thermal protection under standard fi re extinguishing systems. • The solution to this problem of increasing the efficiency of technical solutions for ensuring fi re safety in modern oil and gas enterprises is possible when developing methods for modifying and producing nanomaterial with desired physicochemical proper-  ties. Successful implementation of such technologies is possible when solving problems: • development of methods for "reverse" changes in the properties of substances at the stage of application of technologies characterized by the highest probability of an emergency or fire; • provide relatively low material costs for the implementation of the so-called "smart materials" in exist-ing production and maintenance of fire safety systems; • exclude the negative impact of the proposed technologies on the person, the environment, applying to the production of substances, materials and products. One of the most promising ways to solve this problem is the development of nanotechnologies for the formation and use of supra molecular self-organizing carbon meso structures with predictable characteristics, in chemical reactions and at the interface, which have already found application in technologies for creating nanofluids, structural materials and composites. These characteristics depend largely on thermal physics electrostatic properties of carbon nanomaterial, as well as their linear and volumetric characteristics on nanostructures [5].

MATERIALS AND METHODS
The objects of study were selected multilayer carbon nanotubes (MWCNT), which are extended cylindrical and branching nanostructures (d = 30 nm, l = 1 ... 5 μm). MWCNT were obtained by catalytic pyrolysis using the CVDomna. MWCNTs underwent reagent functionaliza-tion for purification from synthesis by-products in order to improve their performance characteristics [6]. Distilled water, mixtures (NEFRAS C3-80 / 120 "BR-1" gasoline, TS-1 kerosene) liquid hydrocarbons and individual organic substances (o-xylene, ethanol) were used as base fluids. The main properties of the studied base fluids under normal conditions are presented in Table 1. For nanofluids based on water, the red-cross-linked acrylic acid polymer (PAA) "Carbopol ETD 2020" was used as a surfactant to stabilize water clusters and carbon nanostructures. The effect of variable frequen-cy-modulated potential (VFMP) with parameters 56 ... 220 V (50 Hz) [7] for 30 min was applied when dis-persing MWCNT and adding surfactant. The following methods were used in the work: Raman spectroscopy [8]; measurements of the dielectric constant of nanofluids by the method of a flat capacitor; electrical resistivity measurements [9]; measurements of the surface tension coefficient by the method of detachment of drops [10]; atomic force microscopy [11]; studies of the thermo physical properties of liquids in a laboratory setup for studying the processes of surface and bulk boiling of liquids [12]; studies of the processes of flow and evaporation of modified hydrocarbon liquids [7]; studies of electrification processes when handling modified hydrocarbon liquids during their pumping, homogenization and spraying [13]; studies of the extinguishing properties of modified formulations based on water and hydrogels [14]; studies of the operational characteristics of nanomodified flame retardant intumescent compositions in the conditions of the flare combustion of hydrocarbons (jetfire) [15].

THE RESULTS OF EXPERIMENTAL STUDIES
In the study of MWCNT using Raman spectroscopy, data were obtained on the presence of large amounts of amorphous carbon and impurities in non-functionalized MWCNT, as evidenced by the ab-sence of pronounced D-lines (~ 1400 cm) and G-lines (~ 1600 cm -1 ) in the spectrum of the substance. After functionalization, the carbon nanomaterial contained a structured carbon material and had a well-defined G-line in the region of 1600 cm -1 ( Figure 1). The results suggest that dispersion of non-functionalized MWCNT in water reduces surface tension by 10-22% compared with the base fluid, which is associated with the presence of by-products of the syn-thesis of nanoparticles acting as surfactants.  Data on the relative change in the specific volume electrical resistance of modified liquids is presented in Fig. 4. The specific volume electrical resistance of nanofluids is reduced with the introduction of non-functionalized and functionalized nanoparticles to 96%. In general, an increase in the concentration of nanoparticles contributes to a decrease in the specific volume electrical resistance of nanofluids.
When studying the effect of dispersed MWCNT on the properties of nanofluids, it was noted that for individual samples of nanofluids with an increase in the concentration of MWCNT nanoparticles to 1.0 vol. % there is no significant change in the values of surface tension, dielectric constant and specific volume electrical resis-tance, which is associated with exceeding the percolation threshold for nanofluids, as well as intensive agglomeration of nanoparticles [18]. In the conditions of electrophysical exposure, there is an additional change (from 3% to 20%) of the studied values. The result obtained is associated with a decrease in the aggregation of MWCNT in nanofluid and a slower decrease in the working concentration of nanoparticles with macromolecules of basic liquids [19].
The results of the study of nanoparticle traces in nanofluids based on water, o-xylene and ethanol at an MWCNT concentration of 1.0 vol.% Using the AFM method (AFM) are presented in Fig. 5.    [26] In the course of the study, it was revealed that under electro physical effects, self-organization of MWCNT nanoparticles in nanofluids, a reduction in the size of aggregating particles and the distance between individual particles occurs. A decrease in the aggregation of nanoparticles and the stabilization of nanofluids occurs due to the adsorption of ions on the surface of the material. Adsorption creates a double electric layer, in consequence of which repulsion appears between the nanoclusters. The application of an alternating electric field to a solution or a dispersed system leads to the forced motion of charged particles, thereby changing the value of the zeta potential, which leads to a change in the stability parameters of liquid systems [20]. Metallic nanoparticles (Ni) are present in the MWCNT obtained by the method of catalytic pyrolysis, which causes the appearance of "micro wires" with simultaneous orientation along the lines of force of the electric field [21]. Data on changes in the properties of substances and materials obtained using modified liquids are pre-sented in Table 2

DISCUSSION
To implement the fire risk management system at oil and gas enterprises, it is necessary to take a set of organizational and technical measures to reduce the hazardous manifestations of ignition sources, re-duce the likelihood of leaks, limit the spreading and evaporation of flammable and combustible liquids, and protect against local liquid exit due to the destruction of process equipment. When fires and fires occur in process plants and tanks, it is necessary to use fire extinguishing and thermal protection systems, intumescent fire retardant coatings and structural thermal protection [4]. The decision-making process in managing fire risks at oil and gas facilities is based on the results of the assessment of the fire protection status of the objects of protection, the assessment of environmental parameters, the choice of technologies and methods for determining fire risks, as well as methods of their management and control. In this case, the likelihood of emergency situations and the effects of fire hazards is largely determined by the physicochemical properties of substances and materials circulating in technological processes and used to eliminate accidents and extinguishing fires. The introduction of Nano technological solutions to change the properties of the circulating substances and materials, as well as the use of fire extinguishing agents and fire protection equipment of increased efficiency allows redistributing the likelihood of emergency situations and reducing the calculated fire risk values at oil and gas enterprises ( Table 3).
The process of developing technologies for the creation and use of nanomaterials to ensure fire safety at oil and gas facilities can be represented as a functional flowchart (Fig. 6

CONCLUSIONS
The results obtained during the study lead to the following conclusions. 1. The need to develop new technologies for creating nanomaterials to ensure fire safety at oil and gas facilities is due to the "growth limits" of modern technologies for limiting and localizing emergency situations and fire extinguishing, which does not allow you to quickly manage the physical and chemical properties of the circulating substances and materials when handling liquid hydrocarbons.

The direction of developing new technologies to
improve the efficiency of emergency and fire extin-guishing at oil and gas facilities is associated with the creation of new methods for modifying the base substance in the meso structure (in particular, water and liquid hydrocarbons) by introducing carbon clusters (nanomaterials with MWCNT) and management into it processes of stabilization and self-organization of nanostructures in liquids and composites due to external electro physical effects. 3. The proposed technology for controlling the thermo physical, rheological and electrostatic properties of substances allows you to create nanomaterials based on various scenarios of emergency situations and apply them to reduce the fire risk at oil and gas facilities. 4. The implementation of the technology for controlling the properties of substances should be carried out when developing requirements for designing nanomaterials, assessing fire risks for technologies for creating, operating and using nanofluids and composite materials under conditions of possible emergencies at oil and gas facilities, as well as economic assessment of the prospects for using nanomaterials enterprises.