Petro Rio S.A. HRTPF

Testing-- can be one hour or one year

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Drill Stem Tests
Used to provide a more definitive idea of the production capacity of the well, drill stem testsidentify the types of fluids within the well, as well as the flowrateof these fluids, formation permeability and reservoir pressure.
Drill stem tests involve connecting a measurement device to thebottom of the drill stem, also in place of the drillbit, and loweringthe system into the well, all the way to the formation. The instrumentis activated at the bottom of the well, measuring the flow of oil or gasfor a specified amount of time, usually an hour.

Drill Stem TestSource: www.geo.wvu.edu
The testing tool includes a perforated anchor at the bottom thatallows fluids to enter the empty pipe. Also rubber packers expandagainst the sides of the hole to seal pressure. A series of valves openand close to control the flow of the hydrocarbons into the empty drillstem. Additionally, the tool contains a pressure-measuring device.
When the tool is opened, the oil and gas enter the drill pipe and aresent through a flowline to the reserve pit on the surface. While oil orgas can reach the surface during the specified testing time, many timeshydrocarbons and water simply enter the drill pipe, but do not reachthe surface. Nonetheless, the flow, pressure and volumes are recorded.
Important factors in determining the success of the drill stem testand, in turn, the well, include the depth of the tool; duration of thetest; time required for hydrocarbons to reach the surface; fluidsrecovered in the drill pipe; initial and final flow pressures,indicating the increase in flowing capacity of the well; and the shut-inbottom hole pressure, which signifies the maximum reservoir potential.
While drilling a well can be expensive, sometimes completionoperations can be even more expensive. It is important to decide whethera well is commercially productive or it is more logical to simply plugthe well and move on to another location. Typically, one or moreformation test is performed to determine if the well is productive ornot.
If formation tests reveal that the well does not have enoughhydrocarbons present to complete the well for production, the well isplugged and abandoned. However, if the formation tests prove the wellproductive, it is moved into the completion phase, which includesrunning completion strings the length of the well, casing the well and cementing it.

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