Download Problem Set No. 2 - 1995 - University of Saskatchewan

The University of Saskatchewan
Department of Chemical Engineering
CH E 464 - Petroleum Production Engineering
Assignment Set 2
Due date: Wednesday, February 27
Please clearly state all your assumptions and their justifications.
Please give references for parameters and equations that you use.
1. The diagram on the back of this page gives Bo, Rs, and Bg as a functions of pressure for an oil reservoir. The
surface flow of oil is 520 STB/D (assume surface conditions of T = 60 o F and P = 1 atm) and
PReservoir = 3600 psia.
Determine:
i)
ii)
iii)
iv)
Is the reservoir undersaturated or saturated?
What is the flowrate of gas at the surface {scf/D}?
What is the flowrate of gas from the reservoir {RB/D}?
What is the flowrate of oil with dissolved gas at the reservoir {RB/D}?
Assume that the mobility of gas and the mobility of liquid are equal for this example (there is no preferential flow of gas
relative to liquid).
2. A well produces 150 STB/D oil at a flowing bottomhole pressure of 1,500 psig. The productive reservoir zone is
10 ft. thick. A recent pressure survey indicates the reservoir pressure to be 2,000 psig. The well has a
borehole radius of 0.25 ft and a drainage radius of 1,000 ft. The oil viscosity at reservoir conditions is 1.5 cp
and the formation volume factor is 1.5 rb/stb.
a) Estimate the formation permeability assuming single phase, steady state inflow.
b) Core data indicates that the unaltered reservoir permeability is actually 100 md. Does the result from part a)
suggest that the well is damaged or stimulated?
c) Determine the skin factor, S.
3. An investigation of an under-saturated reservoir, which is known to have a significant skin effect pressure loss,
provided the following information:
Wellbore Radius = 4 in.
Wellbore Pressure = 900 psi
Skin Effect Radius = 3 ft.
Drainage Radius = 800 ft.
Drainage/Outer Reservoir Pressure = 5600 psi
Intermediate Radius = 50 ft.
Intermediate Pressure = 4492 psi
a)
b)
c)
d)
Determine both the pressure at the skin effect radius and the skin effect pressure drop.
Determine the skin effect, S.
Calculate the effective wellbore radius.
Calculate the permeability in the skin effect region, ks, if the natural reservoir permeability, k, is 50 md.