TY - JOUR

T1 - Enhance liquid nitrogen fracturing performance on hot dry rock by cyclic injection

AU - Hong, Chun Yang

AU - Yang, Rui Yue

AU - Huang, Zhong Wei

AU - Zhuang, Xiao Ying

AU - Wen, Hai Tao

AU - Hu, Xiao Li

N1 - Funding Information: This research was supported by the Youth Program of the National Natural Science Foundation of China (52004299), Major Project of the National Natural Science Foundation of China (52192621), the National Science Foundation for National R&D Program for Major Research Instruments of China (51827804), Beijing Outstanding Young Scientist Program (BJJWZYJH01201911414038) and the National Science Foundation for Distinguished Young Scholars of China (51725404). The authors also would like to thank Peking University for our Cryo-SEM work and the Yinghua Inspection and Testing (Shanghai) Co. Ltd for their help in CT scanning and data collection.

PY - 2023/4

Y1 - 2023/4

N2 - Producing complex fracture networks in a safe way plays a critical role in the hot dry rock (HDR) geothermal energy exploitation. However, conventional hydraulic fracturing (HF) generally produces high breakdown pressure and results only in single main fracture morphology. Furthermore, HF has also other problems such as the increased risk of seismic events and consuption of large amount of water. In this work, a new stimulation method based on cyclic soft stimulation (CSS) and liquid nitrogen (LN2) fracturing, known as cyclic LN2 fracturing is explored, which we believe has the potential to solve the above issues related to HF. The fracturing performances including breakdown pressure and fracture morphology on granites under true-triaxial stresses are investigated and compared with cyclic water fracturing. Cryo-scanning electron microscopy (Cryo-SEM) tests and X-ray computed tomography (CT) scanning tests were used for quantitative characterization of fracture parameters and to evaluate the cyclic LN2 fracturing performances. The results demonstrate that the cyclic LN2 fracturing results in reduced breakdown pressure, with between 21% and 67% lower pressure compared with using cyclic water fracturing. Cyclic LN2 fracturing tends to produce more complex and branched fractures, whereas cyclic water fracturing usually produces a single main fracture under a low number of cycles and pressure levels. Thermally-induced fractures mostly occur around the interfaces of different particles. This study shows the potential benefits of cyclic LN2 fracturing on HDR. It is expected to provide theoretical guidance for the cyclic LN2 fracturing application in HDR reservoirs.

AB - Producing complex fracture networks in a safe way plays a critical role in the hot dry rock (HDR) geothermal energy exploitation. However, conventional hydraulic fracturing (HF) generally produces high breakdown pressure and results only in single main fracture morphology. Furthermore, HF has also other problems such as the increased risk of seismic events and consuption of large amount of water. In this work, a new stimulation method based on cyclic soft stimulation (CSS) and liquid nitrogen (LN2) fracturing, known as cyclic LN2 fracturing is explored, which we believe has the potential to solve the above issues related to HF. The fracturing performances including breakdown pressure and fracture morphology on granites under true-triaxial stresses are investigated and compared with cyclic water fracturing. Cryo-scanning electron microscopy (Cryo-SEM) tests and X-ray computed tomography (CT) scanning tests were used for quantitative characterization of fracture parameters and to evaluate the cyclic LN2 fracturing performances. The results demonstrate that the cyclic LN2 fracturing results in reduced breakdown pressure, with between 21% and 67% lower pressure compared with using cyclic water fracturing. Cyclic LN2 fracturing tends to produce more complex and branched fractures, whereas cyclic water fracturing usually produces a single main fracture under a low number of cycles and pressure levels. Thermally-induced fractures mostly occur around the interfaces of different particles. This study shows the potential benefits of cyclic LN2 fracturing on HDR. It is expected to provide theoretical guidance for the cyclic LN2 fracturing application in HDR reservoirs.

KW - Cyclic injection

KW - Fatigue damage

KW - Hot dry rock

KW - Liquid nitrogen fracturing

KW - Thermal stress

UR - http://www.scopus.com/inward/record.url?scp=85138308186&partnerID=8YFLogxK

U2 - 10.1016/j.petsci.2022.07.004

DO - 10.1016/j.petsci.2022.07.004

M3 - Article

AN - SCOPUS:85138308186

VL - 20

SP - 951

EP - 972

JO - Petroleum science

JF - Petroleum science

SN - 1672-5107

IS - 2

ER -