Field Outcrop Analogue Studies - A Vital Resource for Heavy Oil Reservoir Development in North Kuwait

Abstract

North Kuwait heavy oil development continues to benefit from detailed study of outcrops at the Jal Az-Zor escarpment that are stratigraphic equivalents to some of their reservoirs. During the 2018-19 field season, focus was placed on recording the internal architectures of specific stratigraphic layers, developing a deeper understanding of the diagenetic processes in the basin and relating these observations to the North Kuwait reservoirs. These are all key controls on reservoir quality and connectivity. Inter-well scale heterogeneities were identified for inclusion into subsurface models to predict steam/polymer conformance and oil production better. Building on work of the 2017-18 field season when the Jal Az-Zor sequence was logged, measured, described and interpreted; units were tracked and correlated laterally for around 3km. Internal architectures of prominent layers were mapped through conventional and drone mounted photographic surveys, and satellite images. X-Ray Diffraction and thin section studies of hand samples were analyzed, to understand mineralogical controls on porosity & permeability. Integrated field trips were conducted with members from subsurface, reservoir and well-engineering disciplines, to engender common perspectives on subsurface uncertainties and development risks. They also served to close the communications gap between disciplines. Interpreted high-resolution photographic data, sediment flow direction measurements and other observations gave clues to environments of deposition and their implications for lateral connectivity for each layer. Observations on vertical connectivity between and within layers were recorded. Geological heterogeneities were considered in the context of the typical inter-well separation spacing for their implications on injected steam or polymer conformance, & water-cut. Depositional models were compiled and interpreted with regard to their implications for reservoir plumbing, H2S risk, top-seal integrity, sand production etc. Additionally, increased awareness of the stratigraphic relationships between zones was utilized to resolve correlation ambiguities for closed spaced wells in a water injection pilot and led to the development of a screening tool to predict water-coning risk in wells and informed a similar study for injected steam-conformance risk mapping. Field analogues at Jal Az-Zor are key to defining and characterizing the key genetic flow units of the heavy-oil reservoirs in North Kuwait and it is rare to have closely linked field-outcrop analogues so readily accessible. They represent an important cost-effective resource for field development and operations as they bridge the scale gap between well-derived and seismic data as they provide insight to the nature of flow unit connectivity (i.e. the reservoir plumbing – heterogeneities that matter-for-flow) in way that other data types do not. Field analogue observations therefore directly inform the grid scale permeability estimates that are used in the dynamic simulator for production forecasting and field development and operations optimization.