JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III PETROLEUM RESERVOIR ENGINEERING Previous Question Paper (August/September - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
Explain in detail about volumetric reservoir of a gas including z-factors.
Answer
A volumetric gas reservoir is a closed system where the gas expansion is the primary drive mechanism, and there is no significant water influx or pressure support from an aquifer. The material balance equation for such a reservoir is based on the real gas law, modified to account for non-ideal behavior using the gas deviation factor, or z-factor.
The relationship is expressed as:
Where P is the reservoir pressure, Gp is the cumulative gas production, and G is the initial gas in place. The z-factor is a dimensionless ratio that accounts for the deviation of real gas behavior from the ideal gas law (PV = nRT). It is a function of reduced pressure (Pr) and reduced temperature (Tr), typically determined from the Standing-Katz correlation or experimental data. As reservoir pressure declines, the z-factor changes, directly impacting the calculated gas recovery and the pressure-production decline curve.
What do you mean by collection of fluid samples? Explain briefly the basic PVT parameters in the laboratory and conversion for field operating conditions.
Answer
Collection of fluid samples involves obtaining representative samples of reservoir fluids (oil, gas, or condensate) from the wellbore or bottom-hole to characterize their physical and chemical properties. This is typically achieved through bottom-hole sampling, where a sampler is lowered to the sand face, or surface sampling (separator sampling), where gas and liquid phases are recombined based on measured gas-oil ratios.
The basic PVT parameters measured in the laboratory include:
- Bubble Point Pressure (Pb): The pressure at which the first bubble of gas evolves from the oil.
- Oil Formation Volume Factor (Bo): The ratio of the volume of oil at reservoir conditions to the volume at standard surface conditions.
- Solution Gas-Oil Ratio (Rs): The amount of gas dissolved in the oil at reservoir conditions.
- Oil Viscosity (μo): The internal resistance of the oil to flow, which varies with pressure and temperature.
Conversion to field operating conditions requires adjusting laboratory data to account for the specific reservoir temperature and the pressure depletion history. This involves using flash liberation or differential liberation tests to simulate the physical processes occurring in the reservoir and the separator, ensuring that the fluid properties used for material balance and reservoir simulation accurately reflect the actual field performance.
What is the significance of real gas equation of state? Derive the equation and write briefly the applications.
Answer
Sign in to view the complete answer paper.
Explain in detail about subsurface sampling and surface recombination sampling with neat diagrams.
Answer
Sign in to view the complete answer paper.
What is radial steady state flow? Derive an equation for radial steady state flow equation.
Answer
Sign in to view the complete answer paper.
What do you mean by reservoir drive mechanism? Explain in detail about different types of drive Mechanisms.
Answer
Sign in to view the complete answer paper.
Define Darcy’s law? Derive and explain in detail about Darcy’s law with a neat diagram.
Answer
Sign in to view the complete answer paper.
What do you mean by natural water drive? Discuss briefly about compaction drive and related pore compressibility phenomena.
Answer
Sign in to view the complete answer paper.
What do you mean by semi steady state in a well flow? Derive an equation for semi steady state in a well flow.
Answer
Sign in to view the complete answer paper.
A homogeneous formation has an average effective permeability ke. The effective permeability out to a radius ra from the well has been altered (damage/stimulation) so that its average value in this region is ka. Show that, for this situation, the skin factor may be expressed as where rw is the wellbore radius. Assume that for r< ra, the flow can be approximately described under steady state conditions and that for r >ra, semi-steady state.
Answer
Sign in to view the complete answer paper.
Derive an equation for generalized form of inflow equation under semi-steady state conditions.
Answer
Sign in to view the complete answer paper.
During drilling, a well is damaged out to a radius of 4 ft from the wellbore so that the permeability within the damaged zone is reduced to 1/100 th of the undamaged effective permeability. After completion the well is stimulated so that the permeability out to a distance of 10 ft from the wellbore is increased to ten times the undamaged permeability. What will be the PI ratio increase if the wellbore radius is 0.333 ft and the drainage radius 660 ft?
Answer
Sign in to view the complete answer paper.
Discuss in detail about Mathews, Brons and Hazebroek pressure buildup theory.
Answer
Sign in to view the complete answer paper.
What do you mean by general theory of well testing? Discuss briefly the salient points.
Answer
Sign in to view the complete answer paper.
What is radial flow? Derive Russell, Goodrich, et. al. solution technique for the solution of the basic differential equation for the radial flow of a real gas
Answer
Sign in to view the complete answer paper.
Discuss briefly about pressure build up analysis in solution gas drive reservoirs.
Answer
Sign in to view the complete answer paper.