TY - JOUR

T1 - Experimental study on plugging performance and diverted fracture geometry during different temporary plugging and diverting fracturing in Jimusar shale

AU - Li, Minghui

AU - Zhou, Fujian

AU - Sun, Zhonghua

AU - Dong, Enjia

AU - Zhuang, Xiaoying

AU - Yuan, Lishan

AU - Wang, Bo

N1 - Funding Information: The authors would like to acknowledge the financial support from National Natural Science Foundation of China (No. 52174045 and No. 52104011 ), Research Foundation of China University of Petroleum-Beijing at Karamay (No. XQZX20210001 ), Innovation Fund of China National Petroleum Corporation (No. 2020D-5007-0207 ).

PY - 2022/8

Y1 - 2022/8

N2 - Temporary plugging and diverting fracturing (TPDF) is one promising technology to form complex fracture networks in unconventional oil and gas resources, such as Jimusar shale in China. The key to the success of this technology depends on two processes: creating a tight plug within previously-created fractures using temporary plugging agents (TPA), and then forming diverted fractures after plugging. Many scholars have studied the plugging law of TPA under different channels aiming at the first process. However, the second process of fracture re-direct to form fracture networks after effective plugging has not been investigated clearly, especially in shale formations. Based on Jimusar shale, this paper investigated the plugging performance of fibers and particles and diverting fracturing behavior under three different TPDF application scenarios: near-wellbore in-plane TPDF, multistage TPDF in the horizontal wellbore, and far-field TPDF within fractures. A series of experiments were carried out under different stress difference conditions and TPA types using true tri-axial fracturing system. Experimental results show that: firstly, in near-wellbore TPDF experiments, the plugging pressure peaks would be increased with horizontal stress difference (HSD) while the deflection angle between the diverted fracture and the initial fracture would decrease with HSD. Once the HSD is over 7.5 MPa, the diverted fractures would be nearly parallel to the initial fractures. Secondly, in far-field TPDF within 2 mm propped fractures, 1 wt% pure fibers cannot form the effective plug in any fractures regardless of the HSD, while the combination of 1 wt% fibers and 1 wt% particles could effectively plug all fractures. The diverted fractures could be only created as branch fractures at the middle of the initial fractures, but the diverted fractures would be merged into the initial fractures when HSD is over 7.5 MPa. Thirdly, in multistage TPDF in the horizontal wellbore, the initial fracture almost initiates from only one slot and becomes one transverse fracture, but multiple parallel transverse fractures after plugging could happen but not always occur. The diverted fracture may also form a longitudinal fracture under low HSD because the slots have been plugged by TPAs. In addition, influenced by bedding and natural fractures, more bedding fractures are activated after plugging, which forms a more complex fracture network. Our experimental results could deepen the understanding of TPDF in Jimusar shale reservoir and also provide fundamental for field design in similar shale reservoirs.

AB - Temporary plugging and diverting fracturing (TPDF) is one promising technology to form complex fracture networks in unconventional oil and gas resources, such as Jimusar shale in China. The key to the success of this technology depends on two processes: creating a tight plug within previously-created fractures using temporary plugging agents (TPA), and then forming diverted fractures after plugging. Many scholars have studied the plugging law of TPA under different channels aiming at the first process. However, the second process of fracture re-direct to form fracture networks after effective plugging has not been investigated clearly, especially in shale formations. Based on Jimusar shale, this paper investigated the plugging performance of fibers and particles and diverting fracturing behavior under three different TPDF application scenarios: near-wellbore in-plane TPDF, multistage TPDF in the horizontal wellbore, and far-field TPDF within fractures. A series of experiments were carried out under different stress difference conditions and TPA types using true tri-axial fracturing system. Experimental results show that: firstly, in near-wellbore TPDF experiments, the plugging pressure peaks would be increased with horizontal stress difference (HSD) while the deflection angle between the diverted fracture and the initial fracture would decrease with HSD. Once the HSD is over 7.5 MPa, the diverted fractures would be nearly parallel to the initial fractures. Secondly, in far-field TPDF within 2 mm propped fractures, 1 wt% pure fibers cannot form the effective plug in any fractures regardless of the HSD, while the combination of 1 wt% fibers and 1 wt% particles could effectively plug all fractures. The diverted fractures could be only created as branch fractures at the middle of the initial fractures, but the diverted fractures would be merged into the initial fractures when HSD is over 7.5 MPa. Thirdly, in multistage TPDF in the horizontal wellbore, the initial fracture almost initiates from only one slot and becomes one transverse fracture, but multiple parallel transverse fractures after plugging could happen but not always occur. The diverted fracture may also form a longitudinal fracture under low HSD because the slots have been plugged by TPAs. In addition, influenced by bedding and natural fractures, more bedding fractures are activated after plugging, which forms a more complex fracture network. Our experimental results could deepen the understanding of TPDF in Jimusar shale reservoir and also provide fundamental for field design in similar shale reservoirs.

KW - Diverted fractures

KW - Fibers and particles

KW - Jimusar shale

KW - Plugging performance

KW - Temporary plugging and diverting fracturing (TPDF)

KW - True tri-axial fracturing experiment

UR - http://www.scopus.com/inward/record.url?scp=85130106625&partnerID=8YFLogxK

U2 - 10.1016/j.petrol.2022.110580

DO - 10.1016/j.petrol.2022.110580

M3 - Article

AN - SCOPUS:85130106625

VL - 215

JO - Journal of Petroleum Science and Engineering

JF - Journal of Petroleum Science and Engineering

SN - 0920-4105

IS - Part A

M1 - 110580

ER -