Drillstem Testing

1
Drillstem Testing

• 22.3

2
DST assembly using two straddle packers
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Test Tree
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Test Choke
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Typical DST
The typical drill stem test will be split into
four period, Pre flow.  initial shut in period, a
main flow period and a final shut in period.
Times of for each test are dependent on
conditions at the well site Drill stem tests may
be run at any time during the drilling operation
at the current depth or may be used to test any
interval in the hole after TD has been reached.
Using these data and based on the evaluation of
engineers and geologists, management can base a
decision to complete the hole for potential
production of oil or gas or proceed with
abandonment.
6
Pre-Flow Period

• is a  production period to clean up the well and
  is used to remove any supercharge given to the
  formation due to mud infiltrating into the
  prospective formation during the drilling
  operation.

7
Initial Shut In

• This period is to allow the formation to recover
  from pressure surges caused during the pre flow.
  this is often referred to as "closed in for the
  pressure build up" this period will be  longer.

8
Main Flow

• a more lengthy production period designed to test
  the formations flow characteristics more
  rigorously. Samples of any fluids will be checked
  for water content Gas bubble bust pressure 
  temperature and many other nice surprises. This
  will be done using set choke or variable chokes.
  Sample  reaching surface will be measured as to
  volume and gathered for analysis in a laboratory.
  Samples of any fluids in the drill string at the
  conclusion of the test will be measured as to
  volume and gathered for analysis. Flowing
  pressures and temperatures will be recorded.

9
Final Shut-In

• formation pressure is recorded over this period.
  The shape of the pressure build up curve will
  tell us the permeability of the formation, the
  degree of formation damage (likely caused during
  the drilling operation), It  will also tell us if
  we have found a small reservoir but there is no
  telling if it a big one.