A petroleum reservoir is a subsurface pool of hydrocarbons that have porous or fractured rock formations. The two major categories of petroleum reservoirs: conventional and unconventional reservoirs. For conventional reservoirs, the hydrocarbons that occur naturally, such as natural gas and crude oil, are trapped by the overlying rock formations that have low permeability. On the other hand, unconventional reservoirs are characterized by a high porosity of the rocks with low permeability. This keeps the hydrocarbons trapped in a place with no need for a cap rock.
Reservoir management
Managing petroleum reservoirs is a dynamic process. There are uncertainties surrounding the reservoir performance. Managing the reservoirs ensures optimal performance with mitigated effects of the uncertainties. According to the presenters at the society of petroleum engineers gas show and conference 2013, effective reservoir management can be achieved through the systematic application of multidisciplinary and integrated technologies. Unlike the unorthodox practices of reservoir control, as disjointed functions, this approach ensures that the control and operation of petroleum reservoir is a system. Therefore, this is a strategic application of various technologies to achieve synergy through optimal performance.
The technology behind building a petroleum reservoir is mainly determined by the processes involved. The two main factors to consider when building a petroleum reservoir are:
1. Pressure
Fluids flow due to pressure. This is driving factor of the flux. Oil can easily flow to the ground since there is sufficient pressure underground. To avoid the fluids in the reservoir from the poor flow, there is need to maintain a minimum pressure level. In the common practice, this was combined with the use of pumps to pump out the oil in case the pressure dropped. This technology is often known as the ‘primary depletion.’
2. Saturation
This is a second most influential factor that plays a part in building a petroleum reservoir. This is a measure of the quantity within the inner, porous space. The modern technology behind building a petroleum reservoir indicates that about 80% oil saturation be maintained. This comes with a 20% water saturation. This is referred to as the ‘connate water.’
As the main variables of consideration, pressure and saturation are complemented by other quantities. These properties include:
- Rock properties
- Rock-fluid properties
- Fluid properties
- Initial and boundary conditions
Basic principles
Modern technologies in building a petroleum reservoir are anchored on the ability to derive major phenomena from various principles. The Newtonian laws of mechanics are known to play a role in the process. The two main principles of this technology are the Darcy’s Law and the Material Balance. The other optional principle is the Fluid Phase behavior.