1 FTC

DST CONCEPT

2 FTC

DST Concept• Lecture Objectives.

By the end of this lecture , YOU should be able to :

• List the 3 main DST components• List the 3 main DST pressures• List the 3 main DST types• Describe the DST concept

3 FTC

The primary DST functions, whether conducted in openhole or cased wells, are to:

• Isolate the target zone. • Control well flow. • Convey fluid to surface. • Acquire downhole data.

DST Concept

4 FTC

DST ConceptThe 3 basic equipment for a drill stem test consits of a string (tubing or drillpipe), a packer and a valve.

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.

5 FTC

Ph: Hydrostatic pressurePf: Formation pressurePc: Cushion pressure

Generally, the relationship among these pressures is:

Ph > Pf > Pc

DST Concept3

6 FTC

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 < Ph

DST Concept

7 FTC

1. W/L perforated “over-balance”

2. RIH DST with Tester valve closed, filling up tubing with cushion.

3. Set packer.

4. Open Tester valve (CM closed)

DST ConceptThe general steps (no TCP) for starting a DST are:

8 FTC

1. Open the reverse circulating valve and “Reverse out” (flush hydrocarbons from drillpipe 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)

DST ConceptThe general steps for ending a DST are:

9 FTC

DST ConceptTypes of DST

10 FTC

DST ConceptWell location & configuration

11 FTC

DST Concept / PACKERS

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

12 FTC

DST Concept / PACKERS

FlexPac

PosiTest

Positrieve

13 FTC

DST Concept / Tester Valves

Various types are used:- MFE (Multi Flow Evaluator)Operated by manipulation of the test string.Applications: Onshore and Jack-up rigs- PCT (Pressure Controlled Tester)Operated by annulus (and tubing) pressure.Application: Offshore, floating facilities.- IRIS dual-valve tool (IRDV)(IRIS= Intelligent Remote Implementation

System)Operated & Application as PCT

14 FTC

DST Concept / Tester Valve

IRIS dual-valve tool

PCT valve

15 FTC

Tubing or drillpipeSlip joints (2 or more)Drill collarsRedundant circulating valveDrill collarsSurface Read outRA markerDrills collarSurface readoutDownhole valveHydrostatic reference toolPressure recorders (2 or more)Hydraulic jarSafety jointPackerSlotted tailpipeDebris subTubingFiring headSafety spacerPerforating gun

DST Concept

Typical DST or TCP tool string

16 FTC

• During the initial phase of the test, the wellbore fluids, and, later, the drilling fluid (mud) that has invaded the formation in the vicinity of the wellbore flow to surface. This is known as the cleanup period. Cleanup is complete when the well effluent at surface is reservoir fluid that contains no mud particles or cuttings at surface.• 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 ConceptBasic operation:

17 FTC

DST CONCEPT

The END