04 DST Concepts
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Transcript of 04 DST Concepts
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DST CONCEPTS
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2
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Module Objectives
To describe the DST concepts
To identify the main DST tools and their functionalities
To go through a DST example
To review the different DST configurations
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Definitions DST :Temporary completion of the well with downhole tools to control the WELL under dynamic reservoir
conditions
A reservoir test can only be performed under dynamic conditions. This means the reservoir must be exposed to a disturbance that will cause the reservoir pressure to change
This pressure change, when recorded and interpreted along with the measured flow rates, will yield information about the reservoir parameters and geometry
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Pressure Disturbance
Creation of a pressure disturbance depends on whether the reservoir is producing or shut in:
if the well has been shut in for a long time, flowing the reservoir creates the disturbance. This is called drawdown
if the well has been flowing for a long time, shutting in the well creates the disturbance. This is called build up
Disturbance can also be created by increasing or decreasing the flow rate
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Flowing the well at several flow rates
using different choke sizes while measuring the stabilized
bottomhole pressure and temperature with accurate downhole gauges for each corresponding choke
Pressure Disturbance Data
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The primary DST functions, whether conducted in open hole or cased wells, are to: Isolate the target zone. Control well flow. Convey fluid to surface. Acquire downhole data.
DST Concepts
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1. The string channels the flow to surface.
2. The packer is a rubber element to isolate the zone to be tested.
3. The valve provides a method of controlling the well near the reservoir.
4. circulating valve provides communication between annulus and tubing.
The 4 basic equipment for a DST consist of a string (tubing or drill pipe), a packer a tester and a circulating valve.
DST Key Components
Circulating valve
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Pc
Pf
Ph
Drill pipe or Tubing
Tester Valve
Packer
Annulus pressure (Ph)
Cushion pressure (Pc)
Formation pressure (Pf)
Pc < Pf < Ph
Circulate/ Reverse Valve
TCP guns
Casing
Downhole Pressures
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The Packer isolates the formation from the annulus, the two pressures (Ph and Pf) must be isolated from one another.
The Tester valve : - controls the formation. - shut the well downhole to minimize wellbore storage effect - isolates annular fluid from cushion while RIH, preventing U-tubing -provides a seal for pressure test the string
After the packer is set and sealed, the test valve can then be opened and hydrocarbons can be produced to surface. This will only occur if Pc < Pf
DST Tools 1/2
Jars
Gauge carrier
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1. Open the reverse circulating valve and Reverse out (flush hydrocarbons from drill pipe or tubing).
2. Close the reverse circulating valve.
3. Open the tester valve.
4. Pump mud into test string to kill the tested interval.
5. Unseat the packer.
6. Pull the string out of the hole (POOH)
The circulating valve can be used for ending a DST :
DST Tools 2/2
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During the initial phase of the test, the well bore fluids, and later, the drilling fluid (mud) that has invaded the formation in the vicinity of the well bore flow to surface. This is the cleanup. It is complete when the well effluent at surface is pure reservoir fluid.
Once cleanup is complete, the main flow period can be maintained for the planned duration, during which downhole pressure measurements and surface flow rates are recorded. At the end of the main flow period, the tester valve is closed. Formation pressure builds up against the valve while downhole pressure measurement continues.
DST Operation Summary
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BHP
Time
Pressure & Temp Recorders
RIH and Set Packer
Example of a DST Sequence 1/9
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BHP
Time
Open Tester valve
Example of a DST Sequence 2/9
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BHP
Time
Flow well
Example of a DST Sequence 3/9
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BHP
Time
Shut in well
Example of a DST Sequence 4/9
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Circulating Valve
BHP
Time
Open circulating valve
Example of a DST Sequence 5/9
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BHP
Time
Reverse Out String Content
Example of a DST Sequence 6/9
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kill the tested interval BHP
Time Circulating Valve closed first
Apply pressure in to annulus to open Tester valve
Tester Valve is open
Open tester valve and bullhead
Example of a DST Sequence 7/9
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BHP
Time
Unset Packer
Example of a DST Sequence 8/9
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BHP
Time
POOH
Example of a DST Sequence 9/9
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Types of DST
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Well Location & Configuration
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PACKERS are designed to isolate the perforated interval from the mud column. The weight applied on the packer compress its rubber elements against the casing and creates a seal between the annulus and tubing.
Three main types of Packers
- FlexPac packer
- PosiTest packer
- Positrieve packer
DST Packers
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FlexPac PosiTest Positrieve
DST Types of Packers
-2 Parts
-Upper & lower slips
-DP 7500 psi
-WP 10 kpsi
-1 Part
-Only lower slips
-Is not used for stimulation jobs
-1 integral Part
-Upper and lower slips
-DP 12kpsi
-WP 15 kpsi
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Various types are available:
- MFE (Multi Flow Evaluator)
Operated by manipulation of the test string.
Applications: Only fixed rigs (onshore & jack-up)
- PCT (Pressure Controlled Tester)
Operated by annulus (and tubing) pressure.
Application: Offshore, floating facilities, only cased hole.
- IRIS dual-valve tool (IRDV)
(IRIS= Intelligent Remote Implementation System)
Operation & application similar to PCT
DST Tester Valves
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IRDV valve PCT valve
IRDV & PCT Valves
- 1 tester valve
- 1 circulating valve
- 1 electronic module
- lower operating pressures than PCT
- pre-programmed sequences
- 1 tester valve
- 1 hold open module
-1 Nitrogen chamber
- longer than IRDV
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Tubing or drillpipe
Slip joints (2 or more)
Drill collars
Redundant circulating valve
Drill collars
Circulating valve
RA marker
Drills collar
Surface readout
Downhole tester valve
Hydrostatic reference tool
Pressure recorders (2 or more)
Hydraulic jar
Safety joint
Packer
Slotted tailpipe
Debris sub
Tubing
Firing head
Safety spacer
Perforating gun
DST/TCP String
Example of a DST / TCP string
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THE END
DST CONCEPTSSlide Number 2Module Objectives Definitions Pressure Disturbance Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29