Questions
10-12 questions in major PSU papers
Difficulty
Hard
Importance
Core — never skip
Overview
Reservoir Engineering is a critical branch of Petroleum Engineering that focuses on quantifying fluid behavior and storage capacity within porous rock formations. It is a high-yield topic for PSU exams like ONGC and IOCL, requiring mastery of fluid dynamics and volumetric estimation techniques to solve complex numerical problems.
Porosity & Permeability
These fundamental petrophysical properties define the storage capacity and flow capability of a reservoir rock. Aspirants must distinguish between total and effective porosity to accurately assess hydrocarbon reserves.
- Porosity (phi) = (Volume of Pores / Bulk Volume)
- Permeability (k) is measured in Darcys (D) or milliDarcys (mD)
- Kozeny-Carman equation relates porosity to permeability
- Absolute vs. Effective vs. Relative permeability definitions
Darcy's Law & Flow Dynamics
Darcy's Law forms the cornerstone of fluid flow through porous media, relating flow rate to pressure drop and rock properties. Understanding the assumptions of laminar, steady-state flow is vital for solving numericals.
- Darcy's Law: q = (k * A * deltaP) / (mu * L)
- Assumptions: Homogeneous, incompressible, isothermal flow
- Radial flow equation for steady-state reservoir conditions
- Formation Volume Factor (B) definition and units
Material Balance Equations (MBE)
MBE is used to determine initial oil/gas in place and predict reservoir performance under different drive mechanisms. The Havlena-Odeh method is the standard approach for solving complex MBE problems.
- General MBE: F = N(Eo + m*Ef + Efw)
- F represents underground withdrawal
- E represents expansion terms (oil, gas, water)
- Havlena-Odeh plot linearization for reserve estimation
Pressure Transient Analysis
This subtopic involves interpreting pressure changes over time to characterize reservoir boundaries and connectivity. It is a common source of advanced numerical questions in technical PSU interviews and exams.
- The Diffusivity Equation for radial flow
- Pressure derivative analysis (log-log plots)
- Skin factor (S) effect on productivity index
- Wellbore storage effects during early-time data
Formula Sheet
phi = Vp / Vb
q = (k * A * (P1 - P2)) / (mu * L)
Bo = (Volume of oil at res. conditions) / (Volume of oil at std. conditions)
F = Np(Bo + (Rp - Rs)Bg) + Wp
S = (kh * deltaP_skin) / (141.2 * q * mu * B)
P(r,t) = (qi * mu * B / 4 * pi * k * h) * Ei(-r^2 / 4 * eta * t)
Exam Tip
Focus on the unit consistency of the Darcy's Law formula, as most PSU exam errors stem from improper conversion of permeability from mD to Darcy or area units.
Common Mistakes
- Confusing Formation Volume Factor (Bo) units, often forgetting that it is dimensionless (RB/STB).
- Neglecting the impact of gas expansion (m) in Material Balance Equations for undersaturated reservoirs.
- Incorrectly converting Darcy units to SI units during numerical calculations.
More Revision Notes
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