Access depth |
  
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Access depth |
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"Access depth" is defined as the depth at which an exploration well intercepts the target reservoir. If this depth is below the hydrocarbon-water contact you will not make a discovery even if the prospect "works" in every other respect. Access depth introduces a new sort of risk.
There are two main reasons you might want to use an access depth. The first is to model a real drilling restriction preventing you from intercepting the reservoir at your preferred depth. This may be the case in particular when drilling a multi-target well. But you might also wish to establish an economically viable reservoir by proving up a deeper contact - in this case drilling below a possible contact is done by choice rather than circumstance.
Either way, using an access depth will potentially decrease the chance of success, but also increase the mean, P50 etc. volumes discovered.
Access depth can only be used if you are calculating GRV from an area/depth table.
To enable access depths go to the input data summary tab 
and click the Constants tab:
Tick the check box and enter the access depth. Shown on the right are the top and bottom contours on the top surface (adjusted for surface shifts, if necessary). Below the height is the "Access chance". This is the chance that the that hydrocarbons will be encountered, assuming that they are present - the chance, in fact, the well will intersect the reservoir body above the contact. This chance will depend on the distribution(s) which control the contact: spill point, hydrocarbon contacts or column heights.
Make sure degree of fill is 100% when using access depths.
If access chance is less than 2% the prospect calculation will not complete.
The results
The prospect summary shows 3 chances:
oGeological chance GPOS is the chance that the reservoir is present according to the standard geological risking
oChance of success is the chance that the planned well will encounter hydrocarbons = GPOS x Access chance.
oOverall chance EPOS is the chance of discovering a reservoir with a volume greater than the defined economic cut-off, if any.
Use in consolidations
Access depth can be used in consolidations, but you must "turn it on". (See Consolidation: access depths). For any prospect,, you can use a different access depth when consolidating than the one used when calculating the prospect itself.