Factors that affect the difficulty of putting reserves into production include permeability, porosity, depth and pressure.
Degradation occurs through chemical and biological processes when oil reservoirs become contaminated by bacteria through subsurface water.
When crude oil is enclosed by a poor quality seal, lighter molecules separate and escape, leaving behind the heavier components through devolatilization.
The injection pattern refers to the arrangement of the production and injector wells to the position, size, and orientation of flow of a reservoir.
[8] Sweep efficiency is the measure of the effectiveness of an EOR method that depends on the total volume of the reservoir that the injected fluid contacts.
Sweep efficiency is affected by multiple factors: mobility ratio, directional permeability, cumulative water injected, flood pattern, geological heterogeneity and distribution of pressure between injectors and producers.
[9] Amplitude Versus Offset (AVO) is a technique used in seismic inversion to forecast the existence of reservoirs and the rock types surrounding it.
The calculation of synthetic seismographs for the ideal model is carried out using the reflectivity technique for those materials whose velocities and attenuations are frequency dependent.
Furthermore, hydrocarbon-saturated zones have extremely high values of attenuation from the direct quality factor (Q) measurements.
The primary objective is balancing the frequency content of near and far stacks, while correcting for the effect of the attenuation over the overburden.
The time lapses between the incident and reflected waves, as well as the properties of the received wave, provide information about the types of rocks and the possible reserves of petroleum and gas deposits If the geological heterogeneity of a reservoir is known, the injection patterns can be designed to direct the injections to the less permeable layers of the rock that have oil.
Therefore, to maximize oil recovery (sweep efficiency), it is necessary to monitor and map the orientation of the permeability layers via seismic surveys.
[18] Over time the artificial pressure loses efficacy because the remaining (heavy) oil is too viscous to flow and is held by sandstone in the reservoirs.
[17] Non-thermal methods include the use of chemicals and microbes to loosen trapped heavy oil and carbon dioxide under pressure.
However, thermal methods - mainly steam injection - are the most efficient way of reducing viscosity and mobilizing heavy oil.
Because of this, ERO begins with analysis of the reservoir, rock formations, permeability, pore geometry and viscosity.
High-temperature, high-pressure steam is left in the reservoir from days to weeks so that the heat can be absorbed by the oil.
After the first treatment, oil production takes place through natural lifting because of the initial reservoir energy.
[12] However, the high costs involved mandate careful evaluations, in-depth study of the oil reservoir and proper design.
[22] Traditionally, the properties of rocks and minerals beneath the earth's surface were defined through seismic exploration and seismology from earthquakes.
However, due technological advances, seismic data became useful to determine pore fluids, saturation, porosity and lithology.
[23] Reservoir properties and seismic data have been linkedby a recent development called rock physics.
Rock physics applications are based on understanding the different properties that affect seismic waves.
The rock-forming minerals are the solid matrix, the frame is the skeleton rock sample, while the pore fluid is gas, water, oil, or some combination.
As a result, the velocities calculated using Gassmann's equation are lower than those measured using logging or laboratory frequencies.
Assumption 4) suggests that the rock-fluid flow is sealed at the boundaries for a laboratory rock sample meaning that the changes in stresses caused by a passing wave do not cause a significant flow of fluid from the rock sample.
Assumption 5) prevents any disrupting interaction between the chemical or physical properties of the rock matrix and the pore fluid.
For example, when sand interacts with heavy oil, the result is a high shear and bulk modulus mixture.