Perforation Location Optimization Considering Microscopic Structure for Multi-Cluster Fracturing Technology
Authors: Xiao Fengchao , Zhang Shicheng , Li Xuechen , Ma Xinfang 
Published: September 2022

ABSTRACT:
Multi-cluster fracturing technology of horizontal wells is the main technical method for effective and economic development in tight reservoirs. The optimization of perforation location is the key to the simultaneous initiation of multiple clusters. Perforation locations are usually determined based on rock mechanics and in-situ stress conditions interpreted by logging and loboratory test. In this study, the parameters such as microscopic mineral composition , micropore and microfracture were introduced to establish a multi-scale data set. Besides, the equilibrium degree of fracture propagation is characterized by the multi-cluster uniform growth coefficient calculated by the perforation eroded area. Then, a fuzzy comprehensive evaluation was developed to analyze the influence of the multi-scale features on the uniform growth of fractures, and the mathematical relationship between them was established, the perforation location was optimized based on the relationship. Finally, the feasibility of the method is verified by case study. Our study results can provide us with more insights into the optimization of the multi-cluster fracture technology.

1. INTRODUCTION
The development of a tight conglomerate reservoir is based on horizontal multi-cluster fracturing technology. In the process of treatments, multi-fractures often initiate and expand unevenly, which is directly due to the uneven flow distribution of each cluster. Scholars have conducted a large number of numerical simulation studies on the initiation and propagation mechanism of multiple fractures (Liu P. et al, 2016; Li L. et al, 2013; Wu K. et al, 2015; Fragacha et al, 2019). It is pointed out that the non-uniform propagation of multiple fractures is not only affected by reservoir heterogeneity and stress interference but also affected by perforation friction. Increasing perforation friction can promote fractures’ uniform initiation and propagation (Wu K. and Olson J. E., 2016). So, The behaviors of hydraulic fracture propagation are very complex.
Hydraulic fracture field monitoring technology is an effective means to understand the shape of hydraulic fractures, which can be divided into indirect monitoring technology and direct monitoring technology. Indirect monitoring technology includes net pressure analysis, well test analysis, production analysis, etc. Direct monitoring technology can be subdivided into near-well zone monitoring technology and far-field zone monitoring technology. Near well zone monitoring technology includes radioactive tracer method, well temperature logging, well diameter logging, optical fiber monitoring (DTS/DAS), perforation imaging monitoring, etc (Barree R. et al, 2002; Roberts G. et al, 2018; Ugueto C. et al, 2016). Far-field zone monitoring technology includes microseismic monitoring, surface inclinometer monitoring, downhole inclination image monitoring of surrounding wells, deep shear wave imaging monitoring (DSWI), etc (Stolyarov S. et al, 2019; Xiu N. et al, 2020). Among them, perforation imaging monitoring technology can directly obtain a large number of high-definition perforation hole images. Calculating the eroded area of the perforation (the area change of the perforation pre-and post-fracturing) can reflect the abrasion degree of the perforation and judge the sand inflow of the fracture.