Hi Danestock Maybe, but only when they hit the hard drilling See...

Hi Danestock

Maybe, but only when they hit the hard drilling See GDN ann 210509 "As the well appears to have crossed a fault in the Barker Creek Formation, part of the Lower Barker Creek
Formation was not penetrated. The gas show of 207 units is considered to juxtapose the
lower Barker Creek gas zone."
Below is a description of Juxtapose

Analysis of Fault Seal Capacity
Given that adequate top seal exists there are a number of ways that a fault will seal.

· Primary seal through juxtaposition of reservoir against seal units.

· Secondary seal through the development of low permeability fault rocks in juxtaposition of reservoir against thief zones.

Juxtaposition provides an indication of the connectivity or ‘plumbing’ between reservoirs.

Understanding the juxtaposition area is vital when trying to understand hydrocarbon migration and also for production scenarios.

The degree of fault seal or conversely fault connectivity is usually variable at different locations along the fault plane.

Faults may juxtapose sealing lithologies against reservoir, or reservoir against reservoir.

It is important to understand the juxtaposition relationships as a first order analysis, but then progress to determine whether faults will seal - even if reservoir is juxtaposed against reservoir.

Juxtaposition Seal
To determine whether a reservoir will juxtapose a seal it is necessary to create a fault plane diagram. This shows the top and base of seal/reservoir for the hanging-wall superimposed onto the footwall traces. These diagrams are known as Allan Maps. The figure below show schematically how the Allan Map is constructed.

The Allan Map provides a method for visualizing and calculating the areas of reservoir-seal juxtaposition on the fault plane
Ideally reservoir units are juxtaposed against low permeability units so that a full lateral seal is formed.

These diagrams are the foundation of all fault seal analysis. They show the reservoir: thief zone connections available across a fault surface.



It is very important to mathematically produce Allan Maps, rather than use sections crossing the fault. It is possible to miss a range of juxtapositions if only the maximum displacement across the fault is considered.

An ideal reservoir seal is one in which sands are juxtaposed against the sealing lithology, comprising shale or other low permeability rocks.

For reservoir: thief zone juxtapositions / connections, the maximum hydrocarbon column expected is the highest structural point of that juxtaposition

Allan Maps can incorporate seal analysis algorithms to give a more accurate answer to complex fault seal questions.



They stopped the drill because they may have been too close to the hanging fault in the lower levels. Therefore drilling on at this location would have been extremley risky, plus many other factors suddenly come into play.

THe top of the well was read correctly, the drill location was updip of PB1, However, at the depth of LBC the stucture changed significantly.

400m or even as low as 50m down dip from PB2 may have made all the difference in the world.

When they choose to drill the lower levels again, probably from a new location we will all know.