Effect of Multiple Flow Pulses on Hydraulic Fracture Network Propagation in Naturally Fractured Volcanic Rock

Guangzhi Yang, Shicheng Zhang, Jia Wang, Ning Li, Xinfang Ma and Yushi Zou
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Guangzhi Yang: College of Petroleum Engineering, China University of Petroleum–Beijing, Beijing 100083, China
Shicheng Zhang: College of Petroleum Engineering, China University of Petroleum–Beijing, Beijing 100083, China
Jia Wang: Engineering Technology Research Institute of PetroChina Xinjiang Oilfield Company, Karamay 843000, Xinjiang, China
Ning Li: College of Petroleum Engineering, China University of Petroleum–Beijing, Beijing 100083, China
Xinfang Ma: College of Petroleum Engineering, China University of Petroleum–Beijing, Beijing 100083, China
Yushi Zou: The Unconventional Oil and Gas Institute, China University of Petroleum–Beijing, Beijing 100083, China

Energies, 2020, vol. 13, issue 3, 1-21

Abstract: Exploring engineering methods for increasing fracture network complexity is important for the development of unconventional oil and gas reservoirs. In this study, we conducted a series of fracturing experiments on naturally fractured volcanic samples. An injection method, multiple flow pulses, is proposed to increase fracture complexity. The results show that fluid leaked into the natural fracture network (NFN) when the injection rate was low (0.2 mL/min); hydraulic-fracture-dominant fracture geometry was created with an injection rate of 2 and 5 mL/min. Under the 2 mL/min-injection scheme with 3 pulses, the injection pressure during the intermittent stage was low (<5 MPa), resulting in a limited increase in fracture complexity. When the number of the flow pulses increased to 5, the pressure drop rate in the fourth and fifth intermittent stage significantly increased, indicating an increase in the aperture of natural fractures (NFs) and in the fluid leak-off effect. Under the 5 mL/min injection scheme containing 5 pulses, besides the enhanced fluid leak-off, a sharp injection pressure drop was observed, indicating the activation of NFs. The complexity and the aperture of the ultimate fracture network further increased. The injection method, multiple flow pulses, can be used to create complex fracture networks effectively.

Keywords: volcanic rock; multiple flow pulses; hydraulic fracture; natural fracture; fracture network (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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