Micro Fracture Propagation During Post-Frac Shut in and Enhanced Gas Production From Shale

Abstract

Recently, the shale gas has become an important source of energy around the globe, thus attracting many operators to engage in research on shale gas. To support the industry efforts, it is our objective to create a simple yet robust method of image analysis which would lead to better evaluation of gas bearing intervals and higher gas production from shale gas wells. We propose an efficient method for imaging the absorbed water vapor on shale. We used the SEM to generate images of the shale samples after being exposed to water vapor. We found a remarkable contrast between the sample regions where the water vapor was absorbed randomly and the unabsorbed regions. Interestingly, various types of micro fractures initiated in and propagated from the regions of highly absorbed water vapor. To quantify the micro fractures and the contrasting regions, we processed the SEM images. We used segmentation algorithm to distinguish the above mentioned regions in the shale. Furthermore, dynamic threshholding and morphological concepts were applied to separate the absorbed water vapor regions from the rest. Finally, we filtered the SEM image spectrum for edge detection which was necessary for seamlessly transitioning the absorbed water vapor regions to micro fractures. We conclude that: (1) The amount of absorbed water vapor is directly related to the initiation of micro fractures and activation of gas bearing capillaries in the shale, (2) Dynamic thresholding and segmentation parameters illustrate the robustness of image processing technique for images with dissimilar illuminations and colors, and (3) the proposed technique can analyze the shale samples automatically, quickly, and reliably. Based on the SEM image analysis, which detect many useful attributes, the proposed method can help the operators in making the best decision for shale gas prospecting. This computerized method offers the industry with the following: (1) Increases the speed and accuracy of the analysis of intervals with high micro fracture density and identifies the micro fracture types and sizes per unit mass and (2) Accurately quantifies and separates the regions of shale where the absorbed water and the activated, gas bearing capillaries are the most. These contributions could lead to the enhanced shale gas production.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015