Calibrating discrete fracture-network models with a carbonate three-dimensional outcrop fracture network: Implications for naturally fractured reservoir modeling

Abstract

A B S T R A C TModeling naturally fractured reservoirs requires a detailed understanding of the three-dimensional (3D) fracture-network characteristics, whereas generally only one-dimensional (1D) data, often suffering from sampling artifacts, are available as inputs for modeling. Additional fracture properties can be derived from outcrop analogs with the scanline method, but it does not capture their full two-dimensional (2D) characteristics. We propose an improved workflow based on a 2D field-digitizing tool for mapping and analyzing fracture parameters as well as relations to bedding. From fracture data collected along 11 vertical surface outcrops in a quarry in southeast France, we quantify uncertainties in modeling fracture networks. The fracture-frequency distribution fits a Gaussian distribution that we use to evaluate the intrinsic fracture density variability within the quarry at different observation scales along well-analog scanlines. Excluding well length as a parameter, we find that 30 wells should be needed to fully (i.e., steady variance) capture the natural variability in fracture spacing. This illustrates the challenge in trying to predict fracture spacing in the subsurface from limited well data. Furthermore, for models with varying scanline orientations we find that Terzaghi-based spacing corrections fail when the required correction angle is more than 60°. We apply the 1D well Kevin Bisdom holds a M.Sc. degree in petroleum engineering and geosciences from the Delft University of Technology, Netherlands. He is currently a Ph.D. candidate in the section of applied geology at the Delft University of Technology working on geomechanical and fluid flow modeling of fracture networks in folded subsurface structures using outcrop analogs in central Tunisia. is a senior geologist and geophysicist at Total. He is currently head of the naturally fractured reservoir (NFR) study team and scientific adviser for NFR operational and research and development projects. Bertrand holds a Ph.D. in structural geology from the Pierre and Marie Curie University of Paris and has 25 years of experience in the oil and gas industry with Shell and Total. received his master's degree at the University of Pisa (Italy) and the Ph.D. at the ETH-Zurich with a thesis on the tectonosedimentary evolution of the South-Alpine rifted margin. He was then at the VU Amsterdam studying passive margins and foredeep basins. Since 2010, he has been a professor for applied geology at the Delft University of Technology working mainly on fractured reservoirs.

Tracking Fluid Flow in Shallow Crustal Fault Zones: 1. Insights From Single‐Hole Permeability Estimates

“…The probability of sampling any fracture is controlled in part by the borehole orientation (Dershowitz, ; Davy et al, ; Terzaghi, ), so extrapolating the volumetric (3‐D) fracture density from borehole traces is important to account for undersampled fractures (Dershowitz, ). While fully capturing the variability of fracture spacing is a complex task that requires a large number of boreholes (Bisdom et al, ), estimating the 3‐D fracture density may be particularly important when evaluating relations with hydraulic properties. Here, we adopt the p xy ‐system convention from Dershowitz and Herda () and applied simple stereological rules (Fox et al, ; Wang, ) to derive the volumetric fracture density, p 32 .…”

The Role of Chemistry in Fracture Pattern Development and Opportunities to Advance Interpretations of Geological Materials

“…Consequently, outcrop fracture studies are an essential element in a strategy for learning about fracture patterns existing at depth. Outcrop fracture mapping is undergoing a renaissance owing to recent advances in remote sensing, drone-based imaging, advanced image processing, and feature extraction of outcrop-based data sets (Bisdom et al, 2014(Bisdom et al, , 2017Hardebol & Bertotti, 2013;Healy et al, 2017;Madjid et al, 2018;Pollyea & Fairley, 2011;Wüstefeld et al, 2018).…”

Calibrate complex fracture model for subsurface flow based on Bayesian formulation

“…Thus, calibrating the uncertainty by matching monitoring data which is known as "inversion process" is crucial for forecast job (Chen et al 2018). Although some work about calibrating fractured geological model has been done such as quantifying the uncertainty of hydraulic tests in fractured rocks based on a geostatistical approach (Bisdom et al 2014;Blessent et al 2011;Zhang et al 2016b), there are a few studies of inversing the complex fracture model properties for both theory and application. For this reason, we are working on quantifying the uncertainty of the complex fracture model for subsurface flow based on the Bayesian formulation and we mainly focus on the two-dimensional fracture model at present.…”

“…Open fractures and veins in flat-lying carbonates in the Potiguar Basin(Bisdom et al 2014), box region A represents "Pattern A" fracture system, ellipse region B represents "Pattern B" fracture system…”