ITC impress energy limited

dst mdt and completetions

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    while we wait for the results of Snatcher 1 I thought some clarification on the main 3 types of testing would be useful.

    DST - a drill stem test is not surprisingly a flow test through the drill string. The zone to be tested is pressure isolated from the rest of the well. If it is done while drilling like Snatcher 1 the bottom seal is the base of the well while the top seal is an inflated packer. Open the zone up and see what comes up the drill string. The wells are controlled these days with pressure chokes so the hollywood gushers are a thing of the past. DSTs can also be done after the well is drilled with a top and base packer.
    The test gives a flow rate and a large fluid sample. Depending on the reservoir, a DST can last 4-12 hours.
    DST can mechanically fail (packer does not hold - tool plugs etc.) or not recover anything (reservoir is tight or mud has 'invaded' and damaged the reservoir).
    Snatcher 1 DST was reported as a mechanical failure

    MDT - Modular Formation Dynamics Tester is widely used offshore but is used onshore more and more. It simply measures the pressure of a reservoir at various depths. The depth vs pressure is plotted as a graph and the slope of the resulting line(s) is used to determine the fluid. The tool can also capture a sample in a small chamber.
    The test yields which part of the reservoir is gas, oil or water and can capture a small sample for analysis. It does not give any indication of flow rate.
    The MDT run at Snatcher 1 recovered a sample of oil (therefore the oil is 'moveable') and would be used to determine how much of the reservoir contained oil (14m gross oil pay in press release).
    The curious can read more at:
    http://www.slb.com/media/services/resources/oilfieldreview/ors92/0492/p58_65.pdf

    Completetion - the last major way to test a reservoir is to 'complete' it, in other words to prepare it for production. A normal completion is fitting a metal casing down the hole and cementing it in place against the surrounding rock. Think of fitting hundreds of metres of 7 inch pipe remotely down a 2 km hole and then cementing it in place. This takes a little time.
    When the hole has casing and a flow control unit at the top (the 'christmas tree'), the well can be perforated. This is done by setting off explosive charges down the hole which are shaped to knock a hole through the casing pipe, through the cement, through the mud clogged reservoir near the well and into the virgin reservoir. A whole series of these perforations are made are the well bore and over the desired interval (usually over all of the oil zone except the bottom few meters to stay away from the water).
    The well is then opened up, allow to clean up (sometimes for a few days) before a stable flow of oil can be measured. The oil produced in this way is usually put in tanks until connected to a pipeline or a steady land transport.
    This method of course gives samples and flow rates and can even give pressure variations over time which tell the engineers how the reservoir is likely to perform in the future.

    Cost and time wise, MDT give the least direct information, don't work well in tight rocks but are the fastest and cheapest. DST are more expensive (partly because they take a long time to set up and run) but give direct flow information useful for deciding if a reservoir will flow at commercial rates.
    Completing a well is much more expensive than the other 2 (10-30 times) and as such is not a light decision. A JV must feel very confident that the reservoir will flow at commercial rates and contain commercial quanties to case a well.
 
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