Drill steam test

1. Majeed Talal Majeed

3. - A drill stem test is a test which uses a special tools mounted on
the end of the drill string .
- It is commonly used to test a newly drilled well, since it can
only be carried out while a rig is over the hole .
- Reservoir characteristics that may be estimated from (DST)
analysis include;
• Average effective permeability
• Reservoir pressure
• Identify reservoir fluids
• Well-bore damage
• Barriers, fluid contacts
• Radius of investigation
• Depletion

4. 1- The flow rate is not constant as the fluid rises in
the drill string .
2- Complications also arise to momentum and
friction effects.
3- The well condition is affected by recent drilling
and completion operations may influence the results.

5. - cased hole DST became a standard for many exploration companies,
particularly offshore
- open hole Drill Stem Testing (DST) based on conventional
technology with mechanically set packer was gradually replaced by
inflatable packer based DST tools
Disadvantages of open hole:-
- some companies still avoid open hole testing based result of:
1-poor success ratios of outdated conventional tools.
2-wireline formation testing has become more frequent due to
advances made in wireline test tools.
Advantages of open hole:-
1-lower cost of the open hole DST service compared to wireline formation
testing.
2-Open hole DSTs are quick and simple to run.
3-Hydrocarbons do not need to be produced to the surface, but a significant
volume of reservoir fluid can be produced
Types of DST tools depend on the testing well completion either CASED
and OPEN hole

6. There is three major methods to analysis the (DST)
data:-
◆ Horner’s plot method
◆ Type curve matching method
◆ Computer matching (DST)

7. The build up and draw down

8. ●Type curves first appeared in oil industry literature in the seventies.
●Several kinds, as listed below, are used to interpret a test in a vertical
well with an infinite homogeneous reservoir:
–Ramey Agarwal et al. type curves
–McKinley type curves
–Earlougher and Kersch type curves
–Gringarten et al. type curves
Type curve matching method

9. Gringarten et al. type curves
• A type curve represents the variations in pressure
versus time for a specified reservoir‐well
configuration.
• It is calculated using an analytic model and
expressed in dimensionless variables.
• The analytic model used by Gringarten to describe a
vertical well in an infinite homogeneous reservoir.

11. •The proportionality factor between pD and Δp
can be used to determine the reservoir’s kh:
kh =141.2qBμ (pd )M/(△p)M
•The ordinate of the match point is measured:-
- in the type curve system of axes: pD
– in the field data system of axes: Δp.
pD=(kh / qBμ 141.2) △p (in practical US units)

12. •In the same way the abscissa of the match point, M, is measured in the
type curve system of axes, tD/CDand in the field data system of axes:
Δt..
tD/CD = ( kh 0.000295/ μC ) Δt (in practical US units)
We can also determine :
- the wellbore storage.
- CDexp(2S).
- the skin.

13. •Type curves were established for constant flow rate production
(drawdown).
•The curves can be used directly to analyze buildup if:
– Δt << tpafter constant flow rate;
– Δt << tp(n‐1) after a multirate history
tp(n‐1) duration of the last production period before shut‐in.
•If these conditions do not exist, using the types directly may lead to
inaccurate results.

14. Using curves to analysis buildup