The Impact of Fine-Scale Reservoir Geometries on Streamline Flow Patterns in Submarine Lobes: Outcrop Analogues From the Tanqua depocentre (Fan 3 & Unit 5)

Abstract

Capturing multiscale heterogeneities within deep-water stratigraphy can help to improve reservoir models and therefore recovery factors. The use of outcrop analogues is a key tool within this process for gaining knowledge on detailed sedimentary architectures and facies relationships. The sand-rich submarine fan systems of the Tanqua depocentre allow a detailed study of individual submarine lobes. An advanced geological reservoir model of a terminal lobe complex of Fan 3 (Skoorsteenberg Formation) was constructed using ReservoirStudioTM, which permits realistic architectures and facies distributions of both lobe and channel bodies to be captured. Available data from the Glitne gas field, a similar sand-rich submarine fan system in the northern North Sea, was used to construct petrophysical property models. Artificial injectors and producers were implemented at various locations in the system. By the use of streamline analysis (RMS2012 TM) the effects on fluid flow were tested between i) traditional lobe deposit models with vertically stacked facies belts that mimic coarsening-upwards in all locations, and ii) deterministic models that include lateral facies changes with dimensions and distributions constrained from previous field data from the Karoo. The findings show that the lobe architecture model employed has a significant influence on the predictability of the breakthrough time within reservoirs. Channelized lobe areas show the best connectivity, but the presence of channels at the well location becomes less important within the more deterministic lobe models due to lobe axis amalgamation. Within channelized lobe areas, the proportion of sand the submarine lobe deposits and the level of facies detail within the channel infill have a major influence on fluid-flow behaviour. Breakthrough time becomes up to 75% shorter with added flow barriers such as mud-clast conglomerate lags and mud-bearing banded sandstones. The implementation of sedimentary detail and the use of realistic sedimentary concepts on the architectural scale are shown to be vital in accurately capturing multiscale reservoir heterogeneities, which will help to improve predictions of reservoir recovery.

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