drill stem test

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Drill Stem Testing (DST):

Drill Stem Testing (DST) 2

Objectives::

Objectives: Understanding of DST Tools used in DST General considerations of DST Advantages/Disadvantages of DST Summary 3

Drill Stem Testing:

Drill Stem Testing Drill Stem Test (DST) is used primarily to determine the fluids present in a particular formation and the rate at which they can be produced. A temporary well completion to gather information on the potential productivity of a formation . 4

Slide 5:

Data Source Possible Analysis Seismic Identify possible Accumulations Regional Information Qualitative Accumulation size and shape using assumed Velocity Profile Hydrocarbon Prospectivity (Seismic oddities / regional information ) Degree Of Development Uncertainty = Very High PRE-DRILLING PHASE

Slide 6:

Data Source Possible Analysis Mud Log Lithology Hydrocarbon Shows Geological Profile Core Samples Depositional Environment MWD Logs Qualitative Hydrocarbons Pressure Regime (Qualitative) Formation Characteristics at the wellbore Fluid Contacts Near-wellbore petrophysical parameters Degree Of Development Uncertainty = High DRILLING A WELL

Slide 7:

REASONS TO DO A DRILL STEM TEST Despite the tremendous value of Core Analysis and Well logging some doubt always remains concerning the potential productivity of an exploratory well .

Slide 8:

KNOWLEDGE + RISK LOW HIGH KNOWLEDGE vs RISK

Slide 9:

REASONS TO DO A DRILL STEM TEST WE NEED TO KNOW : IF THERE IS A RESERVOIR WHAT DOES IT CONTAIN AT WHAT RATE WILL IT PRODUCE FOR HOW LONG WHAT FACILITIES WILL BE REQUIRED AND WHEN WHAT HAZARDS ARE THERE

Slide 10:

Although the cost of such detailed testing is quite high, it is much better to test and be sure, rather than miss a productive zone. Drill Stem Testing (DST) is usually applied to open holes. 10

Commonly Used Tools:

Commonly Used Tools The basic tool assembly consists of: Packer Closed –in pressure valves Anchor shoe Pressure Recorder Safety joint Perforated pipe 11

Slide 13:

Function of DST tools Isolation of producing interval from mud hydrostatic Test “Cushion” - lighter fluid than mud hydrostatic fluid column Down hole shut-in valve to minimise wellbore storage Reverse valves to “kill” the well at the end of the test Slip joints to compensate for tubing length changes due to temperature & pressure changes DRILL STEM TEST TOOLS

Procedure:

Procedure Lowering of DST tool Opening the bypass valve Sealing the hole by packers Rotation of drill string and flow of formation fluid Formation fluid flow Shut in valve and building of pressure Removing DST tool 15

Points of Particular Importance:

Points of Particular Importance Condition of the hole Pressure surges Operating conditions 16

Condition of the hole:

Condition of the hole The close tolerance between the hole and the tool assembly requires a clean well bore if the tool is to reach bottom in an undamaged, unplugged condition The drilling mud should be conditioned to the desired density and viscosity before the test is started 17

Pressure surges:

Pressure surges The pressure effects of pipe movements are of fundamental importance. Special consideration should be given to pipe running and pulling speeds to avoid undue bottom hole pressure variations 18

Operating conditions:

Length and location of the test section Packer seat location Size and number of packers Choke sizes Use of cushions Length of test Handling of test production at the surface Operating conditions 19

Advantages of DST:

Advantages of DST Reasonable sample of formation fluid Can find fluid potential directly Gives better measurements than others Prove reserves by producing hydrocarbons 20

Disadvantages of DST:

Disadvantages of DST Not very Economical Quantitative analysis is not highly accurate Time consuming 21

SUMMARY:

SUMMARY DST determines The formation productivity The flow rate of a reservoir by taking a sample of reservoir rock 22

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