Home work Properties of reservoir fluids dr.Baharimoghadam Sajjad Ahmadinasab 9851102 Solid phases in petroleum reservoirs 1-Asphaltenes A phase diagram is a graphical representation of the equilibrium conditions of different phases of a substance or a mixture. A phase diagram for asphaltene shows the temperature and pressure ranges where asphaltene can precipitate and deposit from petroleum fluids. Asphaltene is a complex and heterogeneous mixture of heavy hydrocarbons that have high molecular weight, high aromaticity, and high polarity. Asphaltene can precipitate and deposit when the temperature or pressure changes, or when an incompatible solvent is added to the petroleum fluid. This can cause problems such as reduced production, increased costs, equipment damage, and environmental issues. The phase diagram for asphaltene depends on the type and composition of the petroleum fluid, the type and amount of the solvent, and the presence of inhibitors or promoters. The phase diagram can be divided into two regions: • Single-phase region: This is the region where asphaltene is dissolved in the petroleum fluid and no solid phase is formed. The single-phase region is bounded by the asphaltene onset curve, which shows the temperature and pressure combinations where asphaltene starts to precipitate at equilibrium. • Two-phase region: This is the region where asphaltene is separated from the petroleum fluid and forms a solid phase. The two-phase region is bounded by the asphaltene precipitation curve, which shows the temperature and pressure combinations where asphaltene reaches its maximum precipitation at equilibrium. The phase diagram for asphaltene can be obtained from experimental measurements or from thermodynamic models. Experimental measurements can use different techniques, such as titration, filtration, gravimetry, spectroscopy, or microscopy, to determine the onset and amount of asphaltene precipitation under different conditions. Thermodynamic models can use different approaches, such as activity coefficient models or equation of state models, to predict the equilibrium conditions of asphaltene precipitation based on thermodynamic principles. 2-Gas Hydrate A phase diagram for gas hydrate shows the temperature and pressure ranges where gas hydrate can form, exist, or dissociate in the presence of water and gas. Gas hydrate is a solid crystalline compound that consists of water molecules forming cages around small gas molecules, such as methane, ethane, propane, carbon dioxide, hydrogen sulfide, and others. Gas hydrate can form when water and gas contact under low temperature and highpressure conditions, such as in deep ocean sediments or permafrost regions. The phase diagram for gas hydrate depends on the type and composition of the gas, the salinity of the water, and the presence of inhibitors or promoters. The phase diagram can be divided into three regions: • Hydrate region: This is the region where gas hydrate is stable and can exist as a solid phase. The hydrate region is bounded by the hydrate equilibrium curve, which shows the temperature and pressure combinations where gas hydrate can form or dissociate at equilibrium. • Ice region: This is the region where ice is stable and can exist as a solid phase. The ice region is bounded by the ice melting curve, which shows the temperature and pressure combinations where ice can melt or freeze at equilibrium. • Liquid-gas region: This is the region where water and gas are stable and can exist as liquid and gas phases. The liquid-gas region is bounded by the vapor pressure curve, which shows the temperature and pressure combinations where water can boil or condense at equilibrium. The phase diagram for gas hydrate also shows the triple point and the quadruple point. The triple point is the point where three phases (hydrate, ice, and liquid) coexist at equilibrium. The quadruple point is the point where four phases (hydrate, ice, liquid, and gas) coexist at equilibrium. To draw a phase diagram for gas hydrate, you need to have experimental or computational data on the hydrate equilibrium conditions for a given gas-water system. 3-Wax A phase diagram for wax shows the temperature and pressure ranges where wax can precipitate and deposit from petroleum fluids. Wax is a mixture of long-chain hydrocarbons that have high melting points and low solubility in oil. Wax can precipitate and deposit when the temperature or pressure changes, or when an incompatible solvent is added to the petroleum fluid. This can cause problems such as reduced production, increased costs, equipment damage, and environmental issues. The phase diagram for wax depends on the type and composition of the petroleum fluid, the type and amount of the solvent, and the presence of inhibitors or promoters. The phase diagram can be divided into two regions: • Single-phase region: This is the region where wax is dissolved in the petroleum fluid and no solid phase is formed. The single-phase region is bounded by the wax appearance temperature (WAT) or cloud point curve, which shows the temperature and pressure combinations where wax starts to precipitate at equilibrium. • Two-phase region: This is the region where wax is separated from the petroleum fluid and forms a solid phase. The two-phase region is bounded by the wax precipitation curve, which shows the temperature and pressure combinations where wax reaches its maximum precipitation at equilibrium. The phase diagram for wax can be obtained from experimental measurements or from thermodynamic models. Experimental measurements can use different techniques, such as titration, filtration, gravimetry, spectroscopy, or microscopy, to determine the onset and amount of wax precipitation under different conditions. Thermodynamic models can use different approaches, such as activity coefficient models or equation of state models, to predict the equilibrium conditions of wax precipitation based on thermodynamic principles.
