well evaluations

Warning this has no specific advice on J-50 but is meant as a summary of the technical side of the announced evaluation and how a geoscience team figures out how much is down there and how much will come out. I will attempt to keep it focused on J-50. The steps are presented in the order that JPR has announced they will be performed.

While drilling - mud log - shows general rock type, measure gas release and can turn up oil shows. When drilling close to a thick pay zone as is J-50 it can be accurate enough to confirm the presence of the oil zone.

Core - an actual cylinder of the rock - it provides porosity, permeability, saturation, depositional, age dating information on a mm scale. This is the holy grail for geos to figure out a reservoir. We are currently waiting on news of the first of 5? 9m cores from the reservoir.

Wireline logs - these measure the various electrical, radioactive etc. tests on the well on a ~.3m scale. Log analysts combine all the readings to predict various important parameters - again porosity, saturation etc. While on a grosser scale than core, you get wireline logs over the whole well. This is information for all geos/engineers - the all rounder of the team.

Image/dipmeter logs - these are a specialized intermediate set of logs on a ~1cm scale but run over the whole reservoir. These are mainly for saturation, fracturing (stress field) and bed forms which leads to depositional environment. These are the holy grail of the sedimentologist and horizontal drillers.

Flow testing - after the well is cased, the rig leaves and a wireline completion unit perforates the well opening up select depths of the well to flow to the surface. After the well settles down for a few days (sometimes a few weeks), a stable oil flow rate can be measured. An extended flow test like JPRs planned 2-3 month test can also do all sorts of pressure tests which give information on flow decline, area of sweep, barriers to sweep and even ultimate recovery for the well (although this may take 6-12 months in a lot of cases). This is the holy grail of engineers (and a lot of people in the stock market - but a 1000 bbl a day well may look to be x2 better than a 500 bbl a day well but if the first dies after a week and the second produces (with normal decline)flows commercial oil for 20 years - I know which one I like).

volumes and reserves - all this info combined with structure maps largely from seismic allow an estimate of the oil in the field and how much can be extracted and at what rate. These estimates are continually refined as information is added and there are many different ways of calculating and catagorizing these numbers (like doctors writing perscriptions in latin we like to look smart but even confuse ourselves sometimes).

I hope this helps people understand why it is not a simple 'we drilled the well and now we have X added value'.
From what I can see it looks like they pretty much got what they expected so far which is not much of a surprise when really they were drilling a short distance step out to a producing field.