Characterizing Static Reservoir Connectivity of Deepwater Slope Deposits Using Sub-Seismic Outcrop-Based Facies Models, Tres Pasos Formation, Magallanes Basin, Chilean Patagonia

Abstract

As petroleum exploration ventures further offshore, the ability to more accurately predict and characterize the architecture of deep-water slope deposits is increasingly important. With well costs of 100's of millions of dollars, limited seismic resolution, and sparse well control, insight beyond well and seismic data is of increased importance. Leveraging outcrop analogs can aid in understanding the impact of inter- and intra-channel architecture on pay connectivity. Such architecture is generally below the resolution of subsurface seismic-reflection imaging and is difficult to deduce from well data. A high-resolution digital model of stacked, deep-water channels from the Laguna Figueroa section of the Late Cretaceous Tres Pasos Formation in Chile was created. This model is based on > 1,600 meters of cm-scale measured section, > 100 paleoflow measurements, and 1,000's of dGPS points (10 cm accuracy) from a well-exposed outcrop belt 2.5 km long and 130 m thick. The model elucidates the effects of facies relationships and intra-channel architecture on channel connectivity. The model captures observed facies geometries at a resolution of 2 m horizontally and 1/4 m vertically (~600M cells). Emphasis was placed on accurate and detailed intra-channel architecture. Three channel width (200, 250, and 300 m) models and two channel base drape (CBD) scenarios were created, for a total of six models. Static connectivity analyses were performed on the models by (1) calculating an overall model value; (2) by channel pair to assess connectivity through stratigraphy; and (3) down depositional-dip to capture planview connectivity variability. As such a fine-scale model would likely not be used in flow simulations, an upscaling analysis was performed to explore architecture degradation and its effects on connectivity. Results of the connectivity analysis show that the CBD scenarios strongly impact sandstone connectivity and that smaller channel widths are more susceptible to poor connectivity and disconnected sandstone. Net-to-gross was calculated to explore its relationship with connectivity metrics. Upscaling the models consistently increases connectivity, and small changes in cell geometry impact architecture, which can artificially induce connectivity. Ultimately, this work aims to constrain uncertainty related to sub-seismic scale architecture and its impact on reservoir connectivity by providing concrete connectivity data and contributing to better predictive models.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015