Optimization of Composite Layering Effect Based on Measured Formation Fracture Height to Length Ratios

Abstract

This study achieves two main goals. First, it develops a method that uses the Composite Layering Effect (CLE) Equation to predict the behavior of potential fractures in conventional and unconventional reservoirs from core samples. The second goal of this study is to determine how different mineralogical and elemental components affect the behavior of fractures predicted using the CLE equation. After the samples are fractured, X-ray Powder Diffraction (XRD) and X-ray Fluorescence (XRF) techniques are executed to measure the mineralogical and elemental compositions of the core samples respectively. In this method, core samples are first obtained from the formation. Next, X-Ray Computed Tomography (CT) is used to determine if core samples have preexisting fractures. The samples are then fractured slightly using Uniaxial Compressive Strength (UCS), in which a compressive-strength machine initiates fractures by applying uniaxial load and stopping automatically upon reaching a predetermined load. CT then confirms the existence of the new fractures, and Image J interprets the height–length ratio of each fracture. These results are used in calculating the CLE. The results of these experiments revealed the relationship between the mineral and elemental compositions of the rocks and the crack dimensions. It was seen that the presence of quartz and clay minerals had the strongest influence on the CLE value due to the brittle behavior of the quartz and ductile behavior of the clay minerals (nacrite). The highest CLE value was recorded for the shale sample that had a preexisting fracture. The fracture patterns developed in the shale samples were mainly parallel to one another. In contrast, the fracture patterns developed in sandstones started out parallel and later merged together to form a connected fracture network.