Three-Dimensional Geomechanical Modeling and Well Spacing Optimization Application in Sichuan Shale Gas Block
Authors: Qian Wang , Haoyong Huang , Hongwei Jiang , Chao Fang , Wenbao Zhai , Chenxi Ye , Xiao Feng 
Published: September 2022

ABSTRACT:
At present, unconventional reservoirs require horizontal drilling and large-scale hydraulic fracturing technology to increase artificial fracture networks in the reservoir. Due to regional differences in geological characteristics, geomechanical properties and reservoir characteristics, the fracturing results are different under the same hydraulic fracturing conditions. In some regions, horizontal well groups with the same spacing have poor fracturing connectivity, and in some regions, the fracturing interference with each other seriously, which makes it impossible to extract oil/gas efficiently and achieve the optimal production capacity. Aiming at the fracturing interference problem of shale gas block in Sichuan province, the three-dimensional geomechanical models are studied. Using the geological structure, geological and geomechanical properties, natural fracture system and stress distribution data provided by the 3D comprehensive model, the dynamic coupling simulation between hydraulic fracturing and geomechanics of adjacent typical wells are carried out on the high precision model of typical platform. Considering reservoir heterogeneity, in-situ stress anisotropy, the interaction between hydraulic fractures and natural fractures, the interaction between hydraulic fractures and the distribution of hydraulic fracture network under the current main fracturing technology and process conditions are simulated. Based on hydraulic fracturing network parameters and morphology, reasonable horizontal well spacing is determined to ensure maximum fracturing effect without fracturing interference and improve shale gas productivity. The research results show that, The well spacing decrease while horizontal in-stress, horizontal stress difference increase. The well spacing increase while natural fracture development, fluid volume and cluster spacing increase.

1. INTRODUCTION
Shale gas reservoirs can only be developed effectively through horizontal well and volumetric fracturing. Horizontal well fracturing creates complex artificial fracture networks around the wellbore (He Hui, 2019; Li Yumei, 2019; Xu Chongzhen, 2018). Due to regional differences in geological characteristics, geomechanical properties and reservoir characteristics, the fracturing results are different under the same hydraulic fracturing conditions. In some regions, horizontal well groups have poor fracturing connectivity, and in some regions, the fracturing interference with each other seriously with the same spacing, which makes it impossible to extract oil/gas efficiently and achieve the optimal production capacity. Some well spacing optimization experiences have been developed in north American shale gas over a long period of time. Cakici (2013) carried out dynamic monitoring test of variable well spacing in well group in Marcellus shale gas reservoir, and determined the effective fracture extension distance. Foluke (2017) studied interwell interference at 201 m and 402 m well spacing in the Permian Avalon shale reservoir based on discrete fracture network model. Apiwat (2019) studied hydraulic fracture characteristics and optimal well spacing in Bakken gas reservoirs through field pilot tests combined with multidisciplinary data analysis methods. Richard (2017) studied the optimal well spacing for the Wolfcamp gas reservoir and found that there was no significant interwell interference when the well spacing was greater than 402 m. Pankaj (2018) evaluated well spacing of Marcellus shale gas by means of integrated geological engineering modeling and numerical simulation, and believed that the optimal well spacing under the current fracturing process conditions was about 300 m, and proposed that well spacing was closely related to fracturing scale. But how to judge the most reasonable well spacing has not formed a unified understanding at home and abroad, so it is necessary to carry out targeted research.