Numerical Simulation on Fracture Propagation Behaviors in Grid-like Fractured Carbonate Reservoirs in Shunbei
Authors: Liu Xiongwei , Zhao Bing , Wang Zikang , Sun Yaoyao , Wu Xiaoguang , Zhang Xu , Zou Wenchao 
Published: August 2024

ABSTRACT:
The carbonate formations are characterized by developing continuous grid-like fractured structures, which pose a great challenge on effective hydraulic fracturing. In order to investigate the fracture propagation behavior in such grid-like fracture carbonate reservoirs and the interaction between hydraulic fracture and grid-like fracture, we employed a Unconventional Fracture Model (UFM) based on the boundary element approach in this paper to simulate the fracturing process in fractured carbonate reservoirs. The effects of key geological and engineering parameters such as fracture approach angle, pump displacement, and stress difference on stimulated reservoir volume were analyzed, and well trajectories were also optimized. Under the condition of Shunbei carbonate reservoir, when the angle α between the grid-like fracture and the horizontal well is 90°, the hydraulic fracture tends to extend parallel to the direction of the grid-like fracture, when α is 45°, the hydraulic fracture tends to penetrate the grid-like fracture and then propagate along the maximum principal stress, and when α is less than 45°, the hydraulic fracture tends to penetrate the grid-like fracture and then be captured by the natural fracture. In the Shunbei reservoirs, with a local stress difference of 40 MPa, the optimal pump displacement is 4∼6 m3/min.

1. INTRODUCITON
Marine carbonate reservoirs are rich for oil and gas resources. In world's proven oil and gas reserves, 60% in the marine carbonate reservoirs, that has become a key area of oil and gas exploitation. Among the marine carbonate reservoirs, grid-like fractured reservoirs is a special structure. Marine carbonate reservoirs are stretched and shear by geological processes, forming deep faults and grid-like fractured zones, that are grid-like fractured reservoirs. Which generally exist in ultra-deep, high-temperature and high-pressure geologic environments, and have received focused attention in recent years (Wang W et al., 2023; LI Y et al., 2022).
Currently, hydraulic fracturing is the main means for exploiting grid-like fracture reservoirs. However, hydraulic fracturing communication large grid-like fractures and many natural fractures has limited, and the classical theory of fracture propagation is not applicable (Hui G et al., 2023). Therefore, to study the propagation law of hydraulic fracture in grid-like fracture reservoirs is important. So far, many scholars have conducted a lot of research on the interaction between hydraulic fracture and grid-like fracture (Zhang Q et al., 2021). However, fracture propagation in grid-like fracture Still have not theoretical support, and the mechanism of hydraulic fracture propagation in grid-like fractured reservoirs is not clear. Based on the UFM model and with the help of Kinetix (Kresse O et al., 2013), which is an integrated software platform for geo-engineering. The authors modeled the grid-like fractured reservoirs, and studied the propagation of hydraulic fracture under the condition of grid-like fracture medium (Ma D C et al., 2023).