Open Access

ARTICLE

Experimental Study on Conductivity of Fractures Supported by Deep Shale in the Sichuan Basin of China

Chunting Liu¹, Xiaozhi Shi¹, Juhui Zhu¹, Bin Guan¹, Subing Wang¹, Le He¹, Tianjun Qi¹, Wenjun Xu^2,3,4, Shun Qiu^2,3,4,*
1 CNPC Chuanqing Drilling Engineering Company, Chengdu, 660051, China
2 School of Petroleum Engineering, Yangtze University, Wuhan, 430100, China
3 State Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization, Wuhan, 430100, China
4 Key Laboratory of Drilling and Production Engineering for Oil and Gas, Wuhan, 430100, China
* Corresponding Author: Shun Qiu. Email:
(This article belongs to the Special Issue: Enhanced Oil and Gas Recovery in Unconventional Reservoirs)

Energy Engineering https://doi.org/10.32604/ee.2025.073233

Received 13 September 2025; Accepted 10 November 2025; Published online 22 December 2025

Abstract

To investigate the long-term fracture conductivity behavior of propped fractures under the high-temperature and high-pressure conditions of deep shale gas reservoirs in the Sichuan Basin, this study systematically analyzed the effects of closure stress, proppant concentration, formation temperature, and proppant size combination. Conductivity experiments were conducted using the HXDL-2C long-term proppant conductivity evaluation system under simulated reservoir conditions to determine the time-dependent evolution of fracture conductivity. The results showed that the 50-h conductivity retention of the rock-plate experiments ranged from 22% to 28%. With increasing closure stress, fracture conductivity exhibited a rapid decline. Under a formation temperature of 120°C and a proppant concentration of 5 kg·m⁻², the short-term conductivity of 70/140 mesh quartz-sand-propped fractures was 2.37 μm²·cm, which decreased to 0.66 μm²·cm after long-term testing. When the closure stress increased to 80 MPa, the short-term and long-term conductivities further declined to 1.36 μm²·cm and 0.39 μm²·cm, respectively. Increasing the proppant concentration from 5 to 7.5 kg·m⁻² at 120°C and 80 MPa improved both short-term and long-term conductivities by enlarging the effective fracture width; however, the conductivity decay rate accelerated, and the 50-h retention dropped from 27.2% to 22.8%. Raising the temperature from 120°C to 140°C promoted proppant crushing and compaction, intensified shale creep, and accelerated fracture closure, reducing long-term conductivity from 0.37 to 0.30 μm²·cm. Under identical conditions, 40/70 mesh ceramic proppants maintained significantly higher conductivities than 70/140 mesh quartz sand, with short-term and long-term values of 8.71 and 2.19 μm²·cm, respectively, at 120°C, 80 MPa, and 5 kg·m⁻². Pure quartz-sand systems failed to maintain effective conductivity under high-temperature and high-stress conditions, whereas adding 20% 40/70 mesh ceramic proppant and thoroughly mixing it, the long-term conductivity has increased by 2.3 times, improving fracture stability while reducing overall cost. A predictive equation was derived from the experimental results to capture the dynamic decay characteristics of fracture conductivity. These outcomes provide a valuable experimental basis and technical support for optimizing fracturing fluid design, proppant selection, and operation parameters in deep shale formations.

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Keywords

Deep continental shale; conductivity; supporting fractures; high-temperature; high-closure-pressure

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