Abstract
Most microfractures generated within a complex fracture network return to a closed state soon after the release of hydraulic pressure, unless propping agent has been successfully placed inside these fractures. However, particle size and proppant density control the success of such placement. This paper presents the results of a laboratory study that demonstrates and quantifies the effectiveness of methods for enhancing and sustaining the conductivity of microfractures in tight formations.
This study examines the conductivity performance of placing microproppant particulates compared to performing an acid fracturing treatment in a created fracture. Various shale core samples were obtained and split along the core length to create artificial fracture faces. Before placement of microproppant into the fracture, the split core fracture faces were first treated with an aqueous-based surface modification agent (ASMA) solution that creates tacky sites to capture any proppant exposed to the treated surface and to mitigate proppant settling. This was then followed by exposure to microproppant slurry. The core halves were then reassembled for core flow testing under closure stress. An acid fracturing treatment administered through the split core fracture involved injection of a sequence of materials that slowly releases organic acid and inorganic acid to etch fracture faces, forming gaps or channels within the fractures, by allowing acid to efficiently dissolve the solid structures on the split core fracture faces.
The experimental results are presented by examining the reliability of ASMA treatments to mitigate proppant settling. A permeability comparison of the fractured cores, with and without treatment with ASMA and proppant slurry, demonstrates a dramatic increase to permeability in the treated cores. Permeability measurements of acidized split cores also demonstrate a drastic improvement compared to those of untreated split cores, indicating the importance of maintaining acid activity to maximize fracture etching effectiveness.
