New Technology Yields High-Resolution 3D Modeling for Fracture Analyses

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203108, “High-Resolution Fracture Analyses and 3D DMX DFN Modeling of Triassic Dolomites, Wadi Bih, Ras Al Khaimah, UAE,” by Janpieter van Dijk and Raffik Lazzar, GeoModl, prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually 9–12 November. The paper has not been peer reviewed. The complete paper outlines a high-resolution 3D fracture modeling exercise using the DMX protocol applied to Triassic dolomites of the United Arab Emirates. The outcropping rocks show a low primary porosity, are well bedded, and are highly fractured (jointed) up to centimeter scale. The exercise shows the relevance of applying new technologies to outcrop observations and shows several elements and related technologies that, to the authors’ knowledge, have not been presented previously. Introduction The focus area of the complete paper is a small outcrop situated in Wadi Bih in the territory of Ras Al Khaimah (Fig. 1) along a small road near a recently constructed artificial lake. This outcrop, which is approximately 150 m2 in size, shows well-bedded, highly fractured Triassic dolomites. Both section views and bedding-plane views can be observed. The outcrop was selected because it represents an analog of the Triassic Khuff formation, an important hydrocarbon-producing reservoir in the region. The outcrop is easily accessible and displays a clearly defined fracture (joint) network with recognizable sets, also showing truncation relationships between fractures, joints, and bedding that can be examined. Geological Context The area shows a complete series of Permian to Cretaceous, mostly carbonate sediments, outcropping in a series of north/south to north-northeast/south-southwest anticlines and synclines bounded by mostly west-vergent thrust faults. The Wadi Bih outcrop is situated on the moderately east-dipping flank of the north/south-trending Hagab Anticline, also called the Hagil Window after the area of the nearby Wadi Hagil, where the deepest Permian series are outcropping in the core of the anticline. This anticline is situated on the foot-wall of a major north/south-trending thrust fault. The geological history of the area is connected to the initial Mesozoic deposition of the series on the shelf area along the northeast flank of the Arabian shield. In the outcrop study, the focus is on the joint network. The authors write that this network is tilted together with the bedding as part of the flank of the anticline. No relation can be detected between the joint network sets and the fault and anticline axis pattern dominating the area. The joint network, therefore, most probably was formed in the early stages after lithification and dolomitization of the rock.