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Dynamic mechanisms of lamina-induced fracture propagation in tight oil-sand formations

Liu Dan, Li Yaohua, Luo Qun, Wang Qianyou, Meng Xiangzhen, Ge Yunjin, Luo Jiaguo, Feng Hairu, Li Yang and Zhang Xin
Dynamic mechanisms of lamina-induced fracture propagation in tight oil-sand formations
Interpretation (Tulsa) (February 2019) 7 (1): T179-T193

Abstract

Lamina-induced fractures (LFs) are abundant in lacustrine formations, playing an important role in tight oil resource exploration. There is a lack of research on the dynamic mechanisms of LF propagation in heterogeneous formations characterized by complex combinations of lamina and surrounding rock. For this reason, we conducted triaxial compressive tests of 28 long column samples and Brazil split tests of 37 short column samples using six core samples with different lithologies, including nine column samples tested using a CT scanner and an acoustic emission apparatus. We designed this experiment to study the LF propagation process and its dynamic mechanisms within different lithologies. Our results show that (1) we classified three mechanical LF types based on the relationship between stress state and lamina angle: tensile LF (T-LF), shear LF (S-LF), and hybrid LF (H-LF); (2) H-LF only propagated in the middle lamina angle range (approximately 11 degrees -64 degrees ); T-LF was inclined to propagate in the low lamina angles; and S-LF was inclined to propagate in the high lamina angles; and (3) in the Ordos Basin, T-LF, TF, and SF propagated mutually in outcrops with low confining pressures. T-LF, H-LF, and SF propagated mutually in the Yanchang Formation, an outcrop that greatly contributes to tight oil sweet spot exploration. Furthermore, unlike the in situ accumulation theory, we find that it is possible for hydrocarbon migration to occur in tight reservoir formations, in which the LF acts as a hydrocarbon migration pathway during the tectonic phase.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 7
Serial Issue: 1
Title: Dynamic mechanisms of lamina-induced fracture propagation in tight oil-sand formations
Affiliation: China University of Petroleum, State Key Laboratory of Petroleum Resources and Prospecting, Beijing, China
Pages: T179-T193
Published: 201902
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 48
Accession Number: 2019-009265
Categories: Economic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Technical papers
Illustration Description: illus. incl. 2 tables, block diag.
Secondary Affiliation: Shanxi Yanchang Petroleum Company, CHN, ChinaChina Petroleum Logging Company, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 2019
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