Concurrent 6. Oral Presentation for: Geophysical characterisation and improved delineation of coaly source rocks from integrated analysis of laboratory, well and seismic data

Abstract

Presented on Tuesday 16 May: Session 6

Coaly facies (coal, shaly coal and coaly mudstone) are proven petroleum source rocks in many sedimentary basins in New Zealand, Australia and Southeast Asia. Often these source rocks are mapped in the subsurface based on sparse well data and seismic amplitude character and their organic richness is estimated using average TOC (total organic content) values from well data. However, as the lateral distribution and organic richness of coaly facies are highly heterogeneous and the seismic amplitude response of facies is non-unique, delineation of coaly facies and TOC estimation away from wells are highly uncertain. To reduce this uncertainty, we characterised coaly facies in Cretaceous–Eocene intervals in Taranaki and Great South Basins using density, P-wave velocity, P-impedance and TOC data from 13 wells, supplemented with rock physics and TOC data of numerous coal samples collected from mines and outcrops around New Zealand. We then carried out a case study from the Paleocene–Eocene interval in the Maari 3D seismic survey area in offshore Taranaki Basin in which we develop a P-impedance model and delineate the coaly facies away from wells based on P-impedance character. Average P-impedance maps were analysed together with seismic amplitude character, structure maps and depositional environment maps to understand lateral and temporal variation of coaly facies. These maps were then converted to proxy-TOC maps using a relationship developed from the outcrop coal samples. The coaly facies show density <2.5 g/cc, P-wave velocity <4000 m/s, P-impedance <9000 m/s × g/cc and varied TOC character in the Cretaceous–Eocene interval.

To access the Oral Presentation click the link on the right. To read the full paper click here