3D Fault Zone Representation in Reservoir Modelling

 

PhD Candidate: Vasileios Papanikolaou

Supervisor: Associate Professor Tom Manzocchi, Dr. Conrad Childs

Funded by: QUAFF2 Multi-Company Project

 

Abstract:

It is widely known that faults strongly affect entrapment of hydrocarbons and reservoir compartmentalization, since they may act either as conduits, baffles or barriers to flow in a number of ways. Geometrically, faults can juxtapose permeable or impermeable units against each other and regarding their petrophysical properties, they may act as membranes, retarding in that way across-fault flow between two permeable units. It is therefore extremely vital to be able to predict fault zone complexity and in addition to be able to create flow simulation models that would honour precisely this structural complexity, along with the fault’s petrophysical properties.

Faults however rarely comprise of one single surface; instead, they tend to form segmented arrays both in map view and cross-section. Fault segmentation results in the formation of complex fault zones, such as neutral and dip relays, fault-bound lenses and regions of normal or reverse drag within the wall rocks (Childs et al., 2009; Kristensen et al., 2008).

The vast majority of flow simulation models treat faults as single and planar 2D surfaces rather than 3D volumes, mostly because of strong gridding limitations on the currently-applied technology behind software modelling tools. Furthermore, 3D fault zone modelling demands high resolution models with a large amount of cells, such that models like these cannot be simulated with the current computer technology. All these parameters mentioned above lead to the conclusion that any inclusion of realistic 3D fault zones on reservoir flow models is extremely difficult.

Published studies indicate than an attempt of capturing the 3D nature of faults has already been made. Local Grid Refinement (LGR) along with fault facies modelling are some of the methods been applied for explicitly representing 3D fault zones in production simulation models (Fachri et al., 2016; Fredman et al., 2008). In a different approach, Manzocchi et al. (2008) developed a template-based upscaling method (Geometrical Upscaling) for an implicitly representation of 3D sub-seismic fault zone structures in commercial flow simulators, with the aim of representing the actual 3D effect of faults on fluid flow.

Ultimately, the main objective of this project is to define different tools and methods for the improved implementation of realistic 3D fault zone structures in both reservoir modelling and flow simulation. On the meantime, since fault segmentation is a key parameter to fault zone complexity, the influence of different 3D fault zone structures (e.g. neutral relays, breached dip relays, fault-bound lenses) on flow will be examined.

 

References:

Childs, C., Manzocchi, T., Walsh, J. J., Bonson, C., Nicol, A., and Schopfer, M. P. J., 2009, A geometric model of fault zone and fault rock thickness variations: Journal of Structural Geology, v. 31, p. 117-127

Fachri, M., Tveranger, J., Braathen, A., and Røe, P., 2016, Volumetric faults in field-sized reservoir simulation models: A first case study: AAPG Bulletin, v. 100, no. 5, p. 795-817

Fredman, N., Tveranger, J., Cardozo, N., Braathen, A., Soleng, H., Roe, P., Skorstad, A., and Syversveen, A. R., 2008, Fault facies modeling: Technique and approach for 3D conditioning and modeling of faulted grids: AAPG Bulletin, v. 92, p. 1457-1478

Kristensen, M. B., Childs, C., and Korstgard, J. A., 2008, The 3D geometry of small-scale relay zones between normal faults in soft sediments: Journal of Structural Geology, v. 30, no. 2, p. 257-272

Manzocchi, T., Heath, A. E., Palananthakumar, B., Childs, C., and Walsh, J. J., 2008, Faults in conventional simulation models: a consideration of representational assumptions and geological uncertainties: Petroleum Geoscience, v. 14, p. 91-110