A three-dimensional model to simulate joint networks in layered rocks

Abstract

Modelling the discontinuity network of fractured reservoirs may be addressed (1) by purely stochastic means, (2) with a fractal approach, or (3) using mechanical parameters describing the spatial organisation of fracture systems. Our paper presents an approach where the geometrical properties of the fracture networks are incorporated in the form of both statistical and mechanical rules. This type of approach is particularly suitable to model stratified fractured rock masses comprising two orthogonal families of joints and a family of sedimentary discontinuities. Their geometrical arrangement is governed by two kinds of rules based on (1) statistical parameters such as the mean, standard deviation of joint length and of bed thickness, both determined by field observations, and (2) geometrical parameters that result from genetic processes inferred from field observations and analogue experiments on the nucleation and propagation mechanisms of joints. Using these parameters, we generate realistic networks in terms of the relative position of joints that control the overall network connectivity: the model enables all combinations of joint spacing and vertical persistence for orthogonal patterns ranging from ladder type to grid type patterns. It also integrates the concept of mechanical "saturation" of a bed, thereby permitting the generation of both "saturated" and "unsaturated" networks.

Topological impact of constrained fracture growth

“…Instead the model creates X-shaped intersections since the fractures are free to cross each other. This could be addressed by integration of simplified mechanical rules to take into account the fracture interaction and their consequences on the distribution of intersection and spatial organization of the network fracture [3,[18][19][20]. Building on simplified mechanical rules Davy et al have introduced a mechanical DFN model [3,20].…”

Carbon dioxide storage risk assessment: Analysis of caprock fracture network connectivity

“…Shape of fractures is an unresolved problem, although measurements suggest that an ellipse is a reasonable approximation (Pollard and Aydin, 1988;Nicol, 1995) and in sedimentary rocks, fractures shape can tend towards rectangular (Josnin et al, 2002). For this reason, as well as the greater computational ease of dealing with rectangles, the fractures in the current model are represented as rectangles.…”

“…Stopping criteria are included such that fractures stop growing when they encounter another fracture. A hybrid model also performs this function in a stochastic framework (Josnin et al, 2002). An advantage of propagating models over marked point process models is their ability to replicate the truncated fractures seen in the field.…”

“…This region around the fracture is referred to as the forbidden zone. The inclusion of a forbidden zone is included in some models (Bourne et al, 2000;Josnin et al, 2002) and can be incorporated into a marked point process model. Another approach taken in the past involves using observations that fractures show fractal behaviour (Barton and Hsieh, 1989;Poulton et al, 1990;Sammis et al, 1991) to create fractal models of the fracture networks (Velde et al, 1991;Acuna and Yortsos, 1995).…”

Impact of a stochastic sequential initiation of fractures on the spatial correlations and connectivity of discrete fracture networks

“…Another is to incorporate the effects of mechanical interactions which control fracture initiation, growth, and arrest. This has been done by reproducing the effects of these interactions on the fracture geometry [Josnin et al, 2002], and mimicking the fracture growth using planar fractures [Cladouhos and Marrett, 1996;Swaby and Rawnsley, 1996;Davy et al, 2013] or nonplanar fractures [Cacas et al, 2001;Srivastava et al, 2005;Bonneau et al, 2013]. Among these methods, Cladouhos and Marrett [1996] relate a simplified two-dimensional linkage model to the emergence of power law distributions.…”