Quantitative Evaluation of Controlling Factors of Nonuniform Production in Deep Shale Gas Based on Optic Fiber Logging Technology
Authors: Shao S. R. , Hu H. , Yang Z. X. , Tan P. 
Published: August 2024

ABSTRACT:
The performance of deep shale gas reservoirs is controlled by several factors, and there is a difference in gas production between fracturing stages. Thus, clarification and quantification of main controlling factors of production is indispensable. In this paper, based on the distributed optic fiber logging data of a deep shale gas well in southern Sichuan, the hierarchical fuzzy comprehensive evaluation method and analytic hierarchy process were used to determine major controlling factors, and a performance evaluation model was established. The results show that the gas production of fracturing stages calculated by above model is highly consistent with measured results. Reservoir physical properties are major factors affecting gas production. The production potential of a stage with high geological quality can be improved by increasing clusters, average pumping rate, proppant injection intensity to achieve complicated fracture networks and increasing the proportion of ceramic proppant to ensure effective conductivity. Given that the contribution of stage lengths to gas production is low, for an interval with poor geological quality, stage lengths can be increased appropriately to reach a balance point of cost-effectiveness and stimulation effect. This study provides a basis for shale gas fracturing optimization and production improvement.

1. INTRODUCTION
With increasing demand for clean energy, the shale gas plays a vital role in global energy market (Ma & Xie, 2018; Zhang et al., 2019; Zou et al., 2021). Sichuan Basin has abundant shale gas resources (Ma, 2017; J. Wang et al., 2023). Changning, Fuling, Weiyuan, Weirong shale gas fields have been discovered successively in Upper Ordovician Wufeng Fm and Lower Silurian Longmaxi Fm marine shale (Feng, 2022; Guo, 2021). In more than ten years of exploration and practice, understanding on reservoir has been deepened, and the horizontal well drilling and fracturing technology has been improved. At present, the development technology for shale gas reservoirs shallower than 3500 m is sophisticated, and Weiyuan-Changning-Zhaotong National Shale Gas Demonstration Zone has been formed, realizing large-scale industrial development of medium-depth and shallow shale gas (He et al., 2023; P. F. Jiang et al., 2023; Xie et al., 2019). Deep shale gas has become an important replacement target for shale gas development in China, and enhancing exploration and development of deep shale gas is of great strategic significance to ensure national energy security (Yang et al., 2019). The shale gas production capacity is affected by many factors, and there is difference in EUR of single wells in the same block and even in fracturing stages (He et al., 2018). Jia et al. (2017) analyzed geological and engineering factors affecting the production of shale gas horizontal wells in Changning-Weiyuan and Zhaotong demonstration zones, and proposed the technical direction of increasing the production of horizontal wells in different blocks. Wang et al. (2017) carried out study on the trend of effects of key geological and engineering factors on fracturing effect, and analyzed the influence degree of factors on the 6 months cumulative production of single wells by using multiple linear regression method. X. Chen et al. (2020) carried out fine reservoir evaluation based on the geological and well logging data of coring wells in Weiyuan area, and quantified relationship between fracturing fluid volume, proppant volume and pumping rate and fracture network effectiveness. J. Chen et al. (2020) et al. carried out study on main controlling factors of shale gas production of horizontal wells in Changning area, and established the production prediction model of productivity in shale gas horizontal well fracturing with the BP neural network method based on genetic algorithm. A lot of efforts have been put in research on analysis of controlling factors of shale gas productivity and establishment of productivity prediction models. Nevertheless, there is a lack of research on deep shale gas and systematic research on quantitative evaluation of non-uniform production control factors. Therefore, understanding the origin of gas production differences and quantification of main factors are of great significance to deepen geological understanding, optimize development plan and increase the single well production.