Components of the Petroleum Production System

Two Interconnected Systems: Petroleum production relies on two main systems: the reservoir (a porous medium with unique storage and flow properties) and artificial structures (including wells, wellheads, and surface facilities for gathering, separation, and storage).

Role of Production Engineering: Focuses on maximizing production or injection in a cost-effective manner, playing a critical role in enhancing recovery techniques like hydraulic fracturing and evolving well architectures.

Short-Term vs Long-Term Focus: Production engineering emphasizes short-term optimization of specific wells, while reservoir engineering targets long-term recovery and reserve management.

Integration with Other Disciplines: Production engineering is interdependent with formation evaluation, drilling technologies, and reservoir engineering to optimize performance and ensure efficient reservoir exploitation. within a reservoir.

1. Preface Two Interconnected Systems: Petroleum production relies on two main systems: the reservoir (a porous medium with unique storage and flow properties) and artificial structures (including wells, wellheads, and surface facilities for gathering, separation, and storage). Role of Production Engineering: Focuses on maximizing production or injection in a cost-effective manner, playing a critical role in enhancing recovery techniques like hydraulic fracturing and evolving well architectures. Short-Term vs Long-Term Focus: Production engineering emphasizes short-term optimization of specific wells, while reservoir engineering targets long-term recovery and reserve management. Integration with Other Disciplines: Production engineering is interdependent with formation evaluation, drilling technologies, and reservoir engineering to optimize performance and ensure efficient reservoir exploitation. within a reservoir.

2. Components of the Petroleum Production System Volume and Phase of Reservoir Hydrocarbons Reservoir Geological Flow Units and Modern Techniques: A reservoir consists of interconnected geological flow units, with modern tools like 3-D seismic and advanced well logging enabling detailed identification of shapes, boundaries, and heterogeneities. Impact of Horizontal Wells: Horizontal and complex wells, with extended reservoir exposure, have made understanding heterogeneities, discontinuities, and anisotropies essential for optimal performance. Reservoir Boundaries and Anisotropies: Features like lateral discontinuities, vertical boundaries (e.g., shale lenses), and anisotropies (e.g., stress, permeability) significantly affect well production, especially for horizontal and complex wells.

3. Components of the Petroleum Production System

4. Components of the Petroleum Production System Porosity

5. Components of the Petroleum Production System Reservoir Height

6. Components of the Petroleum Production System Reservoir Height

7. Components of the Petroleum Production System Reservoir Height

8. Components of the Petroleum Production System Reservoir Height

9. Components of the Petroleum Production System Saturation Water and Hydrocarbon Saturation: In any reservoir, water is always present along with oil and/or gas. Reservoir rocks can be either oil-wet or water-wet , depending on how the oil or water interacts with the rock surface. Most rocks are typically water-wet , meaning the water molecules are more strongly attracted to the rock surface, while oil molecules cling to the water. Connate or interstitial water refers to water that is trapped in the pores of the rock but does not flow. It is usually bound by electrostatic forces and surface tension, and is not part of the free-flowing water in the reservoir. Saturation refers to the fraction of the pore space that is occupied by a particular fluid. If the water saturation is greater than the connate water, it can flow freely along with the hydrocarbons.

10. Components of the Petroleum Production System Saturation 2. Oil and Gas as Phases : Oil and gas are two distinct phases of petroleum hydrocarbons. Depending on the pressure and temperature conditions, they can exist either as liquid (oil), gas, or a combination of both. The terms produced oil and produced gas refer to the portions of the mixture that are separated into liquid and gas phases under standard surface conditions (usually 14.7 psi and 60°F). Reservoir conditions (initial pressure or induced flowing bottomhole pressures) need to allow both phases to coexist and flow together. Temperature remains relatively constant except in high-rate gas wells.

11. Components of the Petroleum Production System Saturation 3. Critical Parameters for Reservoir Evaluation : Before a well is tested or completed, three key parameters need to be determined: porosity , reservoir height , and hydrocarbon saturation . Hydrocarbon saturation can be measured using formation electrical resistivity . Since brines in the formation are conductive (low resistivity), and hydrocarbons are non-conductive (high resistivity), a resistivity log can help determine the presence of hydrocarbons in the reservoir. By calibrating the resistivity data, the fraction of the pore space occupied by hydrocarbons can be estimated. The SP log (spontaneous potential) and resistivity log together help to identify zones of hydrocarbon saturation. High resistivity in a zone, combined with a typical response from the SP log, indicates that the porous medium is likely filled with hydrocarbons.

12. Components of the Petroleum Production System Saturation 4. Estimation of Hydrocarbons : The combination of porosity , reservoir height , and saturations is crucial for determining whether a reservoir is attractive for further exploration or development. These parameters allow engineers to estimate the amount of hydrocarbons near the wellbore, which is essential for making decisions about whether to proceed with production.

13. Components of the Petroleum Production System Classification of Reservoirs 1. Hydrocarbon Phase Diagram : A phase diagram plots temperature (x-axis) and pressure (y-axis) to describe hydrocarbon behavior. Key points on the diagram include the critical point (where liquid and gas properties converge) and the bubble-point pressure . 2. Undersaturated Reservoirs : Occur when the initial reservoir pressure is above the bubble-point pressure. Only liquid (oil) is present, with no free gas. 3. Saturated or Two-Phase Reservoirs : Form when the reservoir pressure is at or below the bubble-point pressure. Free gas coexists and may flow along with the liquid. 4. Lean Gas Reservoirs : Exist when the temperature is higher than the critical temperature. Outside the two-phase envelope, only gas is present.

14. Components of the Petroleum Production System Classification of Reservoirs 5. Retrograde Condensate Reservoirs : Occur within the retrograde condensation region, where pressure reduction leads to liquid (condensate) formation initially, followed by revaporization at lower pressures. The cricondentherm is the maximum temperature for the two-phase envelope. 6. PVT Properties : Each reservoir has unique physical and thermodynamic properties, measured as pressure–volume–temperature (PVT) data through specialized laboratory tests.

15. Components of the Petroleum Production System Classification of Reservoirs

16. Components of the Petroleum Production System Areal Extent 1. Insufficiency of Single Well Data : Porosity, reservoir height, fluid saturations, and pressure from a single well are not enough for decisions on reservoir development or exploitation strategies. 2. Advances in Reservoir Assessment : 3-D seismic techniques and well testing greatly expand the area of reservoir knowledge, including height, porosity, and saturation. These techniques help identify discontinuities and refine reservoir boundaries.  

17. Components of the Petroleum Production System Areal Extent

18. Components of the Petroleum Production System Areal Extent

19. Components of the Petroleum Production System Permeability · Porosity and Permeability : Porosity refers to the fraction of rock volume occupied by pores. Permeability is the property describing the ease with which fluids can flow through the interconnected pores. A high porosity often indicates good permeability (e.g., sandstones), but this relationship is not always direct (e.g., chalks with high porosity but low permeability). · Caution in Correlations : Porosity vs. permeability correlations are lithology-dependent and should be used cautiously. These correlations are mainly useful for matrix stimulation calculations where changes in porosity and permeability are assessed post-treatment. · Historical Background (Darcy’s Law) : The concept of permeability was introduced by Darcy (1856) . Darcy’s experiment demonstrated that fluid flow through a porous medium is linearly proportional to the pressure difference (or head) and the medium's permeability.

20. Components of the Petroleum Production System Permeability Darcy’s Experiment : Water was passed through a sand pack. The pressure difference (head) between inlet and outlet was recorded, and the relationship between flow rate and pressure was observed. Darcy’s Law : q : Flow rate (or velocity) of fluid. ΔP : Pressure difference across the porous medium. k : Permeability, a characteristic property of the medium. Impact of Fluid Viscosity : When fluids other than water are used, the flow depends on the fluid’s viscosity (μ) . The term mobility is defined as ​, representing the ability of a fluid to move through the medium.