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Gold/Mining/Energy : KOB.TO - East Lost Hills & GSJB joint venture -- Ignore unavailable to you. Want to Upgrade?

To: Rocket Red who wrote (994)	12/13/1998 2:14:00 PM
From: JL	Read Replies (2) \| Respond to of 15703

Here's another post from wellgeo... It contains some good thoughts so I'm posting it as a courtesy. Hey, wellgeo! When the vacation is over you BETTER be getting your membership!! To: JL From: wellgeo (Trial Member) Friday, Dec 11 1998 3:12AM ET A message from the poor unqualified wellsite geologist -post it if you like - as I'm still on a trial membership and on vacation thus not using my own computer. 1. Any fluids in the tremblor sand ( gas, oil, water, condensate) will all be at the same pressure in that sealed trap which the drill bit penetrated. When those reservoir fluids were allowed to flow to surface (low pressure) their physical state may change ie. gas down hole then change the pressure ,volume, temperature properties ( remember those nasty little phase diagrams from thermodynamics?) just open a can of pop to see what I mean. But that really doesn't provide much explaination of where the water is coming from - so it goes - assuming that the water is not entering the wellbore through faulty casing up hole - what other possibilities do we have for a sudden large increase in the proportion of water coming to surface after 2 weeks of steady gas/light oil/condensate production. 1. The 17 ft of sand penetrated by the drill bit has a high water saturation ( % of pore space occupied by water vs hydrocarbon - ie. Sw=70% Sh=30% of 14% porosity. A high water saturation - therefore produces a lot of formation water with the gas, but this doesn't make sense since water production was very low to nil for the first 2 weeks of the blowout unless the relative permeability (ability of rock media to transmit a fluid)of the sandstone to water has increased with respect to the realtive perm of the gas - not likely. 2. This could be a relatively small isolated sandstone reservoir (seperated by shales - impermeable boundry- from the overlying formation on the adjacent fault and the rest of the underlying sands) in which case once most of the gas had been flowed - the pressure would be so low that gas would have to be pumped the bring it to the surface (artificially inducing that pressure gradient we were talking about eariler) and the water would be pumped with it because it physically must be at the same pressure as all ther other fluids in the reservoir (ie very low if a small reservoir is the case). So I guess this one's out the door also since the water coming (what % of total the total amount of fluid coming to surface I have no idea) out of the well bore has either has enough pressure head to cause it to rise 200 ft above ground level or it is being carried up with the true reservoir fluids. 3. We have drilled in to a small gas cap on top of a large water zone and the well is mostly in contact with the gas saturated rock. The gas was easily produced at first (accounting for gas being a large % of the fluid to surface) due to the fact that the sand has a higher relative perm to the gas than other fluids. Producing this gas decreases the pressure local to the well bore casing a P grad - this inturn allows an increasing % of formation water (also under high P)to move up and towards the well bore and voila increasing water cut. This would be the worst case senario but on the upside 1. the high pressure proves the fault is sealed 2. the same source rock that filled the sands on the other side of the fault ( which have produced 400 million bbls) must be present on the side of the fault bellevue #1 penetrated ( shales are laterally continous by nature). So chances are that some where in that remaining 980 odd ft of tremblor sands which supposed to be drilled is at least a couple of serious payzones - also remember the seismic shows the structure 14 mi x 4 mi so there is a lot of room to move laterally. Personally I think that water is coming into the well from a shallow aquifer due to casing damage from attempted well control and subsequent blowout. That concludes his post. smile JL