Zion Oil & Gas Inc (ZNOG)

[KyOil]

Well Test #2 - Pressure Transient Test

This step collects a pressure signature and makes an estimate of the reservoir boundaries (size).

In this test the well is cased and the zone under test has been perforated. Notice that no wireline tests are ran in this condition because the steel pipe hinders taking readings and samples directly from the rock. The tests ran in this phase are DST or drill stem tests. In a DST test the drill bit is removed from the drill pipe and a packer is attached to it. When downhole, the packer is expanded and seals against the inside of the casing. There may be a packer above and below the perfed zone to be tested so that it can be isolated from other zones that have been perfed. Unlike the wireline which can be lowered and raised quickly, it can take a day or so just to lower a packer to the bottom on a pipe.

In addition to a packer, the drill pipe has a section that is perforated so that fluids coming into the casing can also flow into the drill pipe and up to the surface.

Notice that the downhole pressure is the only parameter measured with a wireline that is also measured with DST.

We've talked about pressure tests before and it is well defined in the source document:

Pressure transient test – combination of shut-in and flowing periods of the well with measuring of
dynamic bottomhole pressure and production rate (for flowing part) for understanding of
productivity of the well, formation parameters evaluation.

The pressure tests can take some time if the reservoir is large due to needing to lower the pressure from flowing and then allowing time for the pressure to recover. The pressure "signature" gives evidence to how large the reservoir is.

Also, the flow capacity of the well is measured. This is info in addition to permeability measured with the wireline that tells how easily oil (or gas) will move through the rock to the wellbore.