Dingdian Yan a,b , Luanxiao Zhao a,b,* , Xuehang Song c , Jizhou Tang a,b , Fengshou Zhang d
a State Key Laboratory of Marine Geology, Tongji University, Shanghai, 200092, China
b School of Ocean and Earth Science, Tongji University, Shanghai, 200092, China
c CAS Key Lab of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201210, China
d Key Laboratory of Geotechnical & Underground Engineering of Ministry of Education, Tongji University, Shanghai, 200092, China
*Corresponding author.
E-mail address:zhaoluanxiao@tongji.edu.cn (L. Zhao)
Abstract:
Fracability evaluation for unconventional reservoir is critical to the selection of candidate zones for post-frac productivity and plays a key role in fracturing design. Historically, the prevailing models for assessing fracability have been largely relied on brittleness indices. Brittleness indices focus mainly on rock fracture characteristics and offers limited assessment of fracture surface area and the complexity of fracture network, which are more relevant to the practical production. We explored a new fracability evaluation model for unconventional reservoirs from the perspective of fracturing performance, which comprehensively characterizes the rock’s ability to generate larger fracture surface areas, more shear fractures and complex fracture networks. The new fracability index considers both the physical processes of rock failure and fracture propagation, and is directly associated with the dynamic production capacities of reservoir. According to the analysis of energy conservation during hydraulic fracturing, we quantify the rock fracture surface area using the KGD and the PKN models. The ability of rock formation to generate shear fractures is mainly influenced by Poisson’s ratio and mode II fracture toughness. Brittle mineral content and mineral heterogeneity are two vital criteria that significantly affect the complexity of fracture networks. Based on the logging and production data, this fracability model was applied to two types of unconventional reservoirs. Preliminary results show that this fracability model has an improved correlation with the pay zones and actual production, which is beneficial for optimizing fracturing strategies and identifying production sweet spots
Full Airticle:
https://www.sciencedirect.com/science/article/pii/S1365160924002776#fig1
Fig. Variation in fracturing performance across different fracability levels.
