# Reservor Hw

Topics: 5th millennium, Logarithmic scale, Statistical charts and diagrams Pages: 2 (334 words) Published: August 28, 2013
PETR 4308

HW# 7- Solution

Problem Statement The following Draw down test has been performed in a cylindrical reservoir assumed to have a drainage area equal to 5,760,000 sqft and the following data: Table 1: Reservoir Data

Q h rw

90 stb/d 23 ft 0.401 ft

φ μ ct B

0.14 1.5 cp 1.6 E-6 1/psi 1.15 Rb/stb

1. 2. 3. 4.

Estimate Permeability Estimate the Skin factor S Estimate pressure drop due to skin Estimate flow efficiency

Solution Part 1 In a drawdown test, plot of Pwf versus production time in a semi log plot, can give us the reservoir properties as follows: Table 2: Data for semi-log plot
Δt Pws

0.25 0.5 1 1.5 2 2.5 3 4 5 7 10 12 15 20 25

4394 4390 4380 4369 4366 4361 4360 4355 4353 4347 4341 4337 4331 4324 4318

2|Advanced Reservoir Engineering - Hom ew o rk 7- So lut io n

And the semilog plot is as shown in figure 1:

Draw- Dawn test semi log plot
4400 4390 4380 4370 Pwf (psi) 4360 4350 4340 4330 4320 4310 0.1 1 Δt 10 100

Slope of the Horner plot (the straight line) is:

And then k is calculated to be

Part 2 To calculate skin, the following equation is used: [ ( ) ]

Where Pwf(1hr) is the well flowing pressure at at time Δt=1 on the straight line and initial reservoir pressure is the pressure before the production starts or at t = 0, Pi = 4663 Pwf1hr = 4375 S = 3.1 Positive skin is the indication of a damaged well.

3|Advanced Reservoir Engineering - Hom ew o rk 7- So lut io n

Part 3 Pressure drop due to skin can be calculated as

Part4

( (

) )

( (

) )

Since this is a damaged well, the flow efficiency is less than 1.

4|Advanced Reservoir Engineering - Hom ew o rk 7- So lut io n