Vertical propagation behavior of hydraulic fractures in coal measure strata based on true triaxial experiment

Research on hydraulic fracture initiation and vertical propagationbehavior in laminated tight formationAnan Wu1, Bing Hou*1, Fei Gao2&#65292;Yifan Dai1&#65292;Mian Chen1<ul><li>(1. State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum-Beijing, Beijing, China No.1 Cementing Company, Bohai Drilling Engineering Company Limited, CNPC, China. Renqiu,062550)</li> </ul>&#160;Abstract: The extent of hydraulic fracture vertical propagation extent is important in evaluating simulated reservoir volume for laminated tight reservoirs. Given that it is affected by the discontinuities (beddings, natural fractures, and other factors), fracture geometry is complex in the vertical plane and is different from a simple fracture in a homogeneous formation. Because the tight formation bedding is very developed, hydraulic fracture is difficult to spread vertically. Now,the propagation mechanism of hydraulic fracture in the vertical plane has not been well understood. To clarify this mechanism, several groups of large-scale tri-axial tests were deployed in this study to investigate the fracture initiation and vertical propagation behavior in laminated tight formation. The influences of multiple factors on fracture vertical propagation were studied.we carried out the indoor hadraulic fracturing physical simulation experiments of the bedding-developed rocks. Tight cores obtained from the core well were wrapped with cement into 30 cm cubes, and samples were drilled and cemented. Before the experiment ,three-dimensional axial stress was applied to simulate the stratigraphic environment. When the stress was balanced, a certain flowing rate was set for hadraulic fracturing. After the fracturing work was completed, the cement block was opened to observe the hydraulic fracture propagation pattern.The results showed that the ultimate fracture geometries could be classified into three categories: simple bedding fracture, slight turning fracture, stair-like fracture, and multilateral fishbone-like fracture network. Here comes some research knowledge:(1)When the difference between the vertical stress and the minimum horizontal principal stress is less than 12Mpa, the hydraulic fracture will only expand along the rock bedding plane Furthermore. (2)when the vertical stress difference is close to 14 MPa, hydraulic fractures will generate vertical fractures that will communicate multiple beddings of the rock. (3)Increasing flowing rate will cause a slight turning or jumping fractures and improve the complexity of fractures to a certain extent. (4)because of the influence of beddings and lithology,the fracture pressure is usually high.Key words: Hydraulic fracturing, tight reversior Bedding plane, fracture morphology.

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Experimental and numerical investigations on the vertical propagation of hydraulic fractures in laminated shales

Journal of Geophysics and Engineering ◽

10.1088/1742-2140/aac12f ◽

2018 ◽

Vol 15 (4) ◽

pp. 1729-1742 ◽

Cited By ~ 10

Author(s):

Qinglin Shan ◽

Yan Jin ◽

Peng Tan ◽

Ruxin Zhang

Keyword(s):

Hydraulic Fractures ◽

Numerical Investigations ◽

Vertical Propagation

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Near-Wellbore Hydraulic Fracture Non-Planar Propagation and Torturous Morphology in Tight Sandstone Formation

10.4043/31313-ms ◽

2021 ◽

Author(s):

Ruxin Zhang ◽

Qinglin Shan ◽

Wan Cheng

Keyword(s):

Stress Distribution ◽

Fracture Initiation ◽

Damage Mechanism ◽

Fracture Morphology ◽

Propagation Model ◽

Hydraulic Fractures ◽

Tight Sandstone ◽

Propagation Behavior ◽

Stress Shadow ◽

Sandstone Formation

Abstract In this paper, a 3D near-wellbore fracture propagation model is established, integrating five parts: formation stress balance, drilling, casing and cementing, perforating, and fracturing, in order to investigate fracture initiation characteristics, near-wellbore fracture non-planar propagation behavior, and torturous hydraulic fracture morphology for cased and perforated horizontal wellbores in tight sandstone formation. The method is based on the combination of finite element method and post-failure damage mechanism. Finite element method is used to determine the coupling behavior between the pore fluid seepage and rock stress distribution. Post-failure damage mechanism is adopted to test the evolution of hydraulic fractures through simulating rock damage process. Moreover, a user subroutine is introduced to establish the relation between rock strength, permeability, and damage, in order to solve the model. This model could simulate the interaction between fractures during their propagation process because of the stress shadow. The simulation results indicate that each operation could cause redistribution and reorientation of near-wellbore stress. Therefore, it is important to know the real near-wellbore stress distribution that affects near-wellbore fracture initiation and propagation. Initially, hydraulic fractures initiate independently from each perforation and propagate along the direction of maximum horizontal stress. However, hydraulic fractures divert from original direction gradually to interconnect and overlap with each other, because of stress shadow, resulting in non-planar propagation behavior. Individual fractures coalesce into a spiral-shaped fracture morphology. In addition, a longitudinal fracture could be observed because of wellbore effect, which is a result of weak cementing strength or near-wellbore weak plane. Finally, the complex and torturous fracture morphologies are created near the wellbore, incorporating Multi-spiral shaped fracture and horizontal-vertical crossing shaped fracture. However, the propagation behavior of fracture far away from wellbore is controlled by in-situ stress, forming a planar fracture. The highlights of this 3D near-wellbore fracture propagation model are following: 1) it considers near-wellbore stress change caused by each construction to ensure the accuracy of near-wellbore stress distribution; 2) it achieves 3D simulation of fracture initiation and near-wellbore propagation from perforations; 3) the interaction between fractures is involved, resulting in complex and torturous morphology. This model provides the theoretical basis for fracture initiation and propagation, which also could be applied into heterogenous formations considering the effect of discontinuities.

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Effect of initial minimum principal stress and unloading rate on the spalling and rockburst of marble: a true triaxial experiment investigation

Bulletin of Engineering Geology and the Environment ◽

10.1007/s10064-020-01995-5 ◽

2020 ◽

Cited By ~ 1

Author(s):

Quan Jiang ◽

Meizhu Zhang ◽

Fei Yan ◽

Guoshao Su ◽

Xiating Feng ◽

...

Keyword(s):

Principal Stress ◽

True Triaxial ◽

Minimum Principal Stress ◽

Unloading Rate ◽

Triaxial Experiment

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From Peak Force Quantitative Nanomechanical Mapping Measurements to Triaxial Testing: A Comparative Study of Geomechanical Properties of Clay-Rich Carbonates

Volume 11: Petroleum Technology ◽

10.1115/omae2020-18318 ◽

2020 ◽

Author(s):

Kim S. Mews ◽

Mustafa M. Alhubail ◽

Luka Hansen ◽

Hem B. Motra ◽

Frank Wuttke ◽

...

Keyword(s):

Young’S Modulus ◽

Poisson’S Ratio ◽

Young's Modulus ◽

Peak Force ◽

Poisson's Ratio ◽

Triaxial Testing ◽

Hydraulic Fractures ◽

True Triaxial ◽

Geomechanical Properties ◽

Drill Cutting

Abstract The assessment of geomechanical properties of unconventional reservoirs is significant as they assist in placement as well as understanding of the geometry and properties of multi-stage hydraulic fractures in horizontal wells. Severe heterogeneities at micro-scale in addition to possibility of having non-intact samples provide opportunities for using micro-mechanics techniques on drill cutting size samples. This will lead to not only have a continuous log of geomechanical properties on heterogeneous formations but also be able to measure the mechanical properties of non-intact samples accurately. This study presents a multi-scale comparison of the elastic properties such as Young’s modulus and Poisson’s ratio on the Eagle Ford Formation. Peak Force Quantitative Nano-mechanical (PF-QNM) AFM-based technique has been performed and compared with true triaxial testing. A new model for AFM evaluation that corrects Young’s modulus in dependency of Poisson’s ratio has been developed. The results indicate that the distribution of Young’s modulus is separated into two regions, one dominated by brittle minerals indicating higher values and one dominated by ductile rock components resulting in lower values. The findings are significant as PF-QNM testing can be performed where only drill cutting-size samples are available, as it shows strong agreement with the triaxial testing result.

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Fracture Angle Analysis of Rock Burst Faulting Planes Based on True-Triaxial Experiment

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-014-0639-0 ◽

2014 ◽

Vol 48 (3) ◽

pp. 1017-1039 ◽

Cited By ~ 29

Author(s):

Weili Gong ◽

Yanyan Peng ◽

Hu Wang ◽

Manchao He ◽

L. Ribeiro e Sousa ◽

...

Keyword(s):

Rock Burst ◽

Fracture Angle ◽

True Triaxial ◽

Triaxial Experiment

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Hydraulic fracture vertical propagation behavior in transversely isotropic layered shale formation with transition zone using XFEM-based CZM method

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2021.107707 ◽

2021 ◽

Vol 248 ◽

pp. 107707

Author(s):

Peng Tan ◽

Yan Jin ◽

Huiwen Pang

Keyword(s):

Transition Zone ◽

Hydraulic Fracture ◽

Transversely Isotropic ◽

Propagation Behavior ◽

Vertical Propagation ◽

Shale Formation

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The Propagation Behavior of Hydraulic Fracture in Rock Mass with Cemented Joints

Geofluids ◽

10.1155/2019/5406870 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Yongxiang Zheng ◽

Jianjun Liu ◽

Yun Lei

Keyword(s):

Hydraulic Fracturing ◽

Univariate Analysis ◽

Fracture Propagation ◽

Fracture Network ◽

Parameter Analysis ◽

Natural Fracture ◽

Hydraulic Fractures ◽

Fracture Networks ◽

Form Complex ◽

Propagation Behavior

The formation of the fracture network in shale hydraulic fracturing is the key to the successful development of shale gas. In order to analyze the mechanism of hydraulic fracturing fracture propagation in cemented fractured formations, a numerical simulation about fracture behavior in cemented joints was conducted based firstly on the block discrete element. And the critical pressure of three fracture propagation modes under the intersection of hydraulic fracturing fracture and closed natural fracture is derived, and the parameter analysis is carried out by univariate analysis and the response surface method (RSM). The results show that at a low intersecting angle, hydraulic fractures will turn and move forward at the same time, forming intersecting fractures. At medium angles, the cracks only turn. At high angles, the crack will expand directly forward without turning. In conclusion, low-angle intersecting fractures are more likely to form complex fracture networks, followed by medium-angle intersecting fractures, and high-angle intersecting fractures have more difficulty in forming fracture networks. The research results have important theoretical guiding significance for the hydraulic fracturing design.

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