Multi-fracture nonuniform initiation and vertical propagation behavior in thin interbedded tight sandstone: An experimental study

Zou, Yushi; Gao, Budong; Zhang, Shicheng; Ma, Xinfang; Sun, Zhixin; Wang, Fan; Liu, Changyin

doi:10.1016/j.petrol.2022.110417

Cited by 22 publications

(6 citation statements)

References 16 publications

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“…This process involves the propagation of hydraulic fractures driven by high-pressure fluids, as well as complex physical phenomena such as the interference of hydraulic fractures and the interaction between hydraulic fractures and the interfaces of the reservoir layers. , When conducting hydraulic fracturing in deep shale formations, it is important to consider the varying layers of cementation between reservoirs of different properties . These differences can lead to the loss of fracturing fluid, which can significantly impact the effectiveness of reservoir modification. − Therefore, it is important to not overlook the role of interface cementation during the hydraulic fracturing construction process.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Engineering Parameters on Fracture Vertical Propagation in Deep Shale Reservoir: A Numerical Study Based on FEM

Zhang,

Liao,

et al. 2024

ACS Omega

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The geometry of hydraulic fractures in deep shale facies is significantly affected by the longitudinal inhomogeneity of rock physical properties and stresses. Numerous studies have been conducted on the influence of the longitudinal inhomogeneity of rocks on fracture morphology. However, there is still a lack of research that simultaneously considers the reservoir dip, bedding plane interface, and longitudinal inhomogeneity of the reservoir. To fill this gap, a three-dimensional (3D) numerical model of multireservoir hydraulic fracturing, which takes into account the bedding plane interface, was developed using the finite element method (FEM). The Drucker−Prager elastic-plasticity criterion was incorporated to accurately represent the plasticity of deep shale. The research revealed the influence of the formation dip angle on fracture morphology. Additionally, the perforation layer position and pump rate were optimized based on the actual geological parameters in North Jiangsu shale reservoir. The study findings indicate that reservoir fractures with a formation dip are easily detected by the interface. However, it is not necessarily true that the larger the formation dip, the easier it is for fluids to enter the interface. Fracturing from high-strength and stress reservoirs to lower reservoirs promotes the propagation of fracture height and the connectivity of multiple reservoirs. On the other hand, fractures initiated from low-strength and stress reservoirs tend to be confined to adjacent reservoirs more easily. The pump rate significantly affects the vertical propagation of fractures. At high interface strength, fractures with pump rate below 2.4 m 3 /min can only propagate at the perforation layer. The limited fracture height in shale reservoirs is likely due to substantial energy consumption by the fracturing fluid at the bedding plane interface. These studies offer theoretical guidance for understanding the vertical propagation of fractures in a deep multilayer reservoir.

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Section: Introductionmentioning

confidence: 99%

“… 17 These differences can lead to the loss of fracturing fluid, which can significantly impact the effectiveness of reservoir modification. 18 − 21 Therefore, it is important to not overlook the role of interface cementation during the hydraulic fracturing construction process.…”

Section: Introductionmentioning

confidence: 99%

Influence of Engineering Parameters on Fracture Vertical Propagation in Deep Shale Reservoir: A Numerical Study Based on FEM

Zhang,

Liao,

et al. 2024

ACS Omega

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“…As oil and gas exploration progresses, high-quality thick sandstone reservoirs (TSR) are becoming scarce, while there is a growing trend in discovering thick–thin interbedded sandstone reservoirs (TTISR), and the comparison between the two is shown in Figure b and Table . − Using China National Offshore Oil Corporation as an illustration, as of 2023, approximately 20% of proven reserves and 19% of annual production stem from TTISR. The shift toward TTISR introduces distinct challenges, marked by significant variations in a sand body scale, an increased prevalence of thin layers, and a propensity for internal fault development .…”

Section: Introductionmentioning

confidence: 99%

Factor Analysis and Prediction on Recovery Efficiency in Offshore Sandstone Reservoirs with Thick–Thin Interbedding

Wu,

Yuan,

Gao

et al. 2024

Energy Fuels

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Chinese oil companies have formulated an empirical recovery efficiency model derived from an analysis of over 140 waterflooded oilfields. Initially successful in thick sandstone reservoirs (TSR), the industry has shifted focus to thick−thin interbedded sandstone reservoirs (TTISR). The empirical formula, however, falls short of the desired accuracy (below 60%) in TTISR due to the unique challenges posed, including diverse sand body scales, strong heterogeneity, and easily developed faults. To address these challenges, a comprehensive prediction model (CPM) has been introduced. This model integrates key parameters and refines the predictive capabilities. Noteworthy relationships include the arctangent function correlation between water flooding control (E s ) and well density, as well as the linear relationship between the fault interference coefficient (E f ) and fault block. Reservoir heterogeneity, assessed using Lorenz coefficient L, is intricately incorporated into the CPM. The resulting relationship with the heterogeneity interference coefficient (E L ) follows a quadratic function. The presence of these typical features results in a lower recovery efficiency for TTISR compared to TSR. The CPM unfolds in a three-stage pattern, featuring a concaveascending trend, followed by a period of linear increase, and concluding with a convex-ascending trend as well density grows. This implies that the incremental oil yield diminishes in later stages compared to earlier stages. The effectiveness of the CPM is substantiated by verifying recovery data from the A area of the PL oilfield, achieving an impressive accuracy rate of 91%. Furthermore, the CPM facilitates the swift prediction of well numbers in the B area, showcasing its practical utility. This method not only serves as a robust tool for predicting recovery efficiency but also offers valuable insights for optimizing well numbers in similar oilfield development schemes.

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“…Proppants mainly concentrate in the main hydraulic fractures with larger widths near the perforated layers, and only a small amount (or none) of proppant is found in the activated layers, branched fractures, and adjacent layer fractures. The limit width for proppants to enter fractures is approximately 2.7 times the proppant particle size [35][36][37]. Among numerous controllable engineering factors, completion type, pumping method, pumping volume, and fracturing sequence are the primary considerations.…”

Section: Introductionmentioning

confidence: 99%

Study on Fracture Propagation Rules of Shale Refracturing Based on CT Technology

Zhang,

Wang,

Xiao

et al. 2024

Processes

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Reactivating oil and gas wells, increasing oil and gas production, and improving recovery provide more opportunities for energy supply especially in the extraction of unconventional oil and gas reservoirs. Due to changes caused by well completion and production in pore pressure around oil and gas wells, subsequently leading to changes in ground stress, and the presence of natural and induced fractures in the reservoir, the process of refracturing is highly complex. This complexity is particularly pronounced in shale oil reservoirs with developed weak layer structures. Through true triaxial hydraulic fracturing experiments on Jimsar shale and utilizing micro-CT to characterize fractures, this study investigates the mechanisms and patterns of refracturing. The research indicates: (1) natural fractures and the stress states in the rock are the primary influencing factors in the fracture propagation. Because natural fractures are widely developed in Jimsar shale, natural fractures are the main influencing factors of hydraulic fracturing, especially in refracturing, the existing fractures have a greater impact on the propagation of secondary fracturing fractures. (2) Successful sealing of existing fractures using temporary blocking agents is crucial for initiating new fractures in refracturing. Traditional methods of plugging the seam at the root of existing fractures are ineffective, whereas extensive injection of blocking agents, forming large “sheet-like” blocking bodies in old fractures, yields better sealing effects, promoting the initiation of new fractures. (3) Moderately increasing the pumping rate and viscosity of fracturing fluid is advantageous in forming “sheet-like” temporary blocking bodies, enhancing the complexity of the network of new fractures in refracturing. (4) When there is a high horizontal stress difference, after sealing old fractures, the secondary hydraulic fractures initiate parallel to and extend from the old fractures. In cases of low horizontal stress difference, the complexity of secondary hydraulic fractures increases. When the horizontal stress changes direction, the secondary hydraulic fractures also change direction. It is recommended to use high-viscosity fracturing fluid and moderately increase the pumping rate, injecting blocking agents to seal old fractures, thereby enhancing the complexity of the network of refracturing. These findings provide important technical guidance for improving the efficiency of shale oil reservoir development.

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Multi-fracture nonuniform initiation and vertical propagation behavior in thin interbedded tight sandstone: An experimental study

Cited by 22 publications

References 16 publications

Influence of Engineering Parameters on Fracture Vertical Propagation in Deep Shale Reservoir: A Numerical Study Based on FEM

Influence of Engineering Parameters on Fracture Vertical Propagation in Deep Shale Reservoir: A Numerical Study Based on FEM

Factor Analysis and Prediction on Recovery Efficiency in Offshore Sandstone Reservoirs with Thick–Thin Interbedding

Study on Fracture Propagation Rules of Shale Refracturing Based on CT Technology

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