Engineering Fundamentals in GATE PE
The Engineering domain in GATE PE (Petroleum Engineering) tests core subsurface and surface engineering principles: reservoir characterization, drilling mechanics, and production operations. Expect quantitative problems that combine material balance, fluid flow, and well performance. The exam emphasizes field-unit calculations and practical design choices.
Core rules and concepts
- Volumetric oil initially in place (OOIP): (N = \frac{7758 A h \phi (1-S_w)}{B_o}), where A is acres, h is ft, and (B_o) is rb/STB. The constant 7758 converts acre-ft to barrels.
- Darcy's law for radial flow: (q = \frac{0.00708 k h (P_e - P_w)}{\mu B_o \ln(r_e/r_w)}) in STB/day, with k in md, h in ft, pressures in psi, (\mu) in cp.
- Inflow performance relationship (IPR): linear for undersaturated oil; Vogel's equation for solution-gas drive.
- Drilling: specific energy and bit hydraulics; annular velocity must exceed cuttings slip velocity.
- Nodal analysis balances inflow (IPR) and outflow (tubing performance).
Worked example
Calculate OOIP for A = 640 acres, h = 40 ft, (\phi) = 0.18, (S_w) = 0.25, (B_o) = 1.3 rb/STB. (N = 7758 \times 640 \times 40 \times 0.18 \times 0.75 / 1.3). Numerator: 7758 × 640 = 4,965,120; × 40 = 198,604,800; × 0.18 = 35,748,864; × 0.75 = 26,811,648. Divide by 1.3: 20,624,344 STB, or about 20.6 MMSTB. Check that (B_o) is in rb/STB before dividing.
Traps that cost marks
- Inverting (B_o) (using STB/rb) or mixing acre-ft with cubic metres.
- Forgetting net-to-gross ratio when (\phi) is gross porosity.
- Using the wrong Darcy constant (0.00708 for radial flow, 0.001127 for linear flow).
- Applying Vogel IPR above bubble point where the linear relationship holds.