ICE 2022


In this case-study we outline the importance of regional and sub-regional depositional system interpretation in development projects. We detail stratigraphic and sedimentological analysis workflows for deep-water reservoir characterization and how this impacted reservoir performance and aquifer support expectations. The Dalmatian North Field, operated by Murphy Oil in Block 4, Desoto Canyon, produces oil from two Miocene turbidite ‘Big Hum’ (BH) sands; A & B (lower & upper respectively) through two producers. DC4-1 is located structurally down-dip and DC4-2 updip. The wells are in pressure communication within each interval as well as between intervals, the latter revealed when DC4-2 found the BH-B as slightly depleted. Dalmatian North lacks aquifer support; therefore, it became important to improve the understanding of reservoir architecture to optimize plans for injector and producer placement. Careful mapping of top & base BH-A & B and deeper Top Oligocene and salt-structures was undertaken on two different seismic surveys i.e., ION WiBand PSDM (2012) & WesternGeco Broadband NAZ (2015). Multiple amplitude extractions and spectral decomposition maps were generated for each interval as well as isochores between all levels. Each product was interpreted for stratal discontinuities, depositional features, and architectures. The wells were interpreted with petrophysics, image log and biostratigraphy to estimate degree of relative confinement (sensu Stanbrook & Bentley, 2021) and resultant architectures. Derived well architectures utilised the same definitions used in the mapping, allowing direct comparison of these architectural interpretations; these were crossed referenced with depositional concepts and analogue databases. Through understanding the regional context, we establish that depositional fairways, strongly controlled by salt structure, were derived from the NE from the Oligocene through to the Miocene BH level. The rapidly deposition of sand immediately downdip of salt structures improves the probability of stratigraphic continuity making successful placement of additional injectors & producers the BH more likely. Concurrently deep-water systems were derived from the NW and ran along the front of the same salt-structures; these eroded the down-dip extension of NE derived BH sands which explains the lack of aquifer support. Stanbrook, D., & Bentley, M., 2021. MPG