
TY  - JOUR
A1  - Rek, Anna 
A1  - Dorling, Mathew 
T1  - Silvereye 1 Case Study ? the False Positive
JF  - ASEG Extended Abstracts
JO  - ASEG Extended Abstracts
Y1  - 2012
VL  - 2012
IS  - 1
SP  - 1
EP  - 10
KW  - 
UR  - https://doi.org/10.1071/ASEG2012AB267 
N2  - The objective of the recent Silvereye 1 exploration well in Bass Basin was to test Paleocene and Cretaceous sandstone reservoirs of the Eastern View Coal Measures (EVCM). The well was designed to test a faulted four-way dip closure and stratigraphic trap interpreted as a sand filled channel. Pre-drill analysis relied on a recent 3D marine seismic survey with well control provided by 2D seismic ties to wells located in adjacent exploration permits. The pre-drill interpretation of a gas-bearing sandstone-filled channel was based on a brightening of seismic amplitude (a predominantly class 3 AVO anomaly) associated with the channel feature. The AVO behaviour was consistent with the response at the same gas-bearing stratigraphic level in the nearby White Ibis 1 well, hence the presence of hydrocarbons (gas) was considered likely. The well intersected the predicted stratigraphy but failed to encounter hydrocarbons at any of the reservoir intervals. A channel sand was intersected within a thick claystone interval at the pre-drill proposed stratigraphic trap. The claystone is characterised by low-velocity and high density, while the sandstone has slightly higher porosity than sand typically encountered in this section. It was the contrasting characteristics of these lithologies that determined the class 3 AVO response and the misinterpretation of the anomaly. We show that a close examination of the rock physics trends of reservoir and non-reservoir rocks in surrounding wells could have allowed this scenario to be recognised pre-drill.  Failure to recognise all possible lithological characteristics in the pre-drill AVO model meant that not all outcomes were analysed, and hence were not included in the risking of the prospect . The post drill evaluation has recognised that rock physics studies are an important tool for recognising all possible scenarios to aid in prospect evaluation. Had a more comprehensive rock physics evaluation been conducted, the actual outcome would likely have been recognised as one of several possibilities, but would not necessarily have prevented drilling of the well. 
ER  -

