RE: Helium Flowed Freely Without Stimulation6 Mar 2024 10:57
Tutorial Transcript with comments
Part 1
DST temporarily produces hydrocarbons/formation fluids (Gases) through the drill string, or stem.
DSTs also measure formation pressure and formation temperature.
The tool is run on the drill string (stem)
The test evaluates selected test zones. Like well logging DSTs help well owners decide whether to run casing and complete a well
RJ Comment: They subsequently ran a casing to complete the well so there must be something worth having to go through that expensive process.
A DST tool lets formation fluids flow to the surface or sometimes into a sample chamber inside the downhole tool.
While the well flows, the well owner can determine the producing characteristics of the well. Such information allows the owner to produce the well more efficiently when completed.
DST Tool Components
Reverse Circulation Sub
Shut In Valve
Recorder
Hydraulic Bypass
Hydraulic Jar
Safety Joint
Packer
Perforated Pipe
Anchor Shoe
The crew lowers this assembly to the depths/zones the well owner wants to test (in this example the bottom of the hole)
RJ Comment: In HeliumOne’s case, three separate zones
Part 2
The crew lower the DST tool into the hole on the drill pipe after the well is well circulated and conditioned with drilling fluid.
The hydraulic bypass is opened because the packer has limited clearance with the upper casing and open well bore.
The open bypass allows drilling fluid in the hole to flow up inside the tool as the crew lowers it.
Letting drilling fluid flow up inside the tool prevents it from creating pressure surges.
Pressure surges could fracture the formation to be tested.
With the DST tool on the bottom,(or zone) the driller slacks off the draw works brake to put weight on the tool.
Weight causes the packer to expand.
The packer seals off the hole beneath it.
With the hole sealed by the expanded packer, the DST operator rotates the drill string.
Rotation opens ports inside the DST tool.
With the ports open, formation fluids flow into the tool and to the surface, during this time crew members closely monitor annulus pressure. They monitor annulus pressure to make sure the packer maintains a good seal between the hole section being tested and the annulus above the packer.
The test crew puts water into the pipe above the DST tool, this is a water cushion. The water cushion supports the drill pipe against mud pressure in the annulus until the test starts. The water cushion also puts hydrostatic pressure on the formation when the DST tool ports are open.
The hydrostatic pressure is however not enough to keep the formation from flowing into the DST tool.
The water cushion is just that, ‘A Cushion’ it keeps the formation fluids from surging with great force into the tool and the drill string.
If allowed to surge, the force could damage the recording instruments in the tool and the formation rock.