scholarly journals Numerical Study of the Effect of Perforation Friction and Engineering Parameters on Multicluster Fracturing in Horizontal Wells

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Zixi Jiao ◽  
Anlin Zhang ◽  
Longhuan Du ◽  
Yang Yang ◽  
Hua Fan
Keyword(s):  
Flow Rate ◽  
Propagation Model ◽  
Fluid Viscosity ◽  
Multiple Fracture ◽  
Multiple Fractures ◽  
Shadow Effect ◽  
Stress Shadow ◽  
Dynamic Partitioning ◽  
Initiation And Propagation ◽  
Engineering Parameters

Simultaneous multiple-fracture treatments in horizontal wellbores have become one of the key methods for economically and efficiently developing oil and gas resources in unconventional reservoirs. However, field data show that some perforation clusters have difficulty propagating fractures due to the internal mechanism of competing initiation and propagation among the fractures. In this paper, the physical mechanisms that influence simultaneous multiple-fracture initiation and propagation are investigated, and the effects of engineering parameters and in situ conditions on the nonuniform development of multiple fractures are discussed. A 3D fracture propagation model was established with ABAQUS to show the influence of the stress shadow effects and dynamic partitioning of the flow rate by simulating the propagation of multiple competing fractures generated in the perforation clusters. Based on the results of these simulations, simultaneous flow in multiple fractures can propagate evenly. Through adjusting the number of perforations in each cluster or the perforation diameter, the effect of the stress shadow can be significantly reduced by increasing the perforation friction, and the factors that affect the development of multiple fractures are changed, from the stress shadow effect to the dynamic partitioning of the flow rate. When the stress shadow effect is dominant, increasing the fracturing fluid viscosity promotes the uniform development of multiple fractures and increases the fracture width. When the dynamic partitioning of the flow rate is dominant, increasing the injection rate greatly affects the uniform development of multiple fractures.

scholarly journals Numerical Study of Simultaneous Multiple Fracture Propagation in Changning Shale Gas Field

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1335 ◽  
Author(s):  
Jun Xie ◽  
Haoyong Huang ◽  
Yu Sang ◽  
Yu Fan ◽  
Juan Chen ◽  
...  
Keyword(s):  
Shale Gas ◽  
Fracture Propagation ◽  
Injection Rate ◽  
Propagation Model ◽  
Fluid Viscosity ◽  
Multiple Fracture ◽  
Gas Field ◽  
Fracture Spacing ◽  
Stress Shadow ◽  
Engineering Parameters

Recently, the Changning shale gas field has been one of the most outstanding shale plays in China for unconventional gas exploitation. Based on the more practical experience of hydraulic fracturing, the economic gas production from this field can be optimized and gradually improved. However, further optimization of the fracture design requires a deeper understanding of the effects of engineering parameters on simultaneous multiple fracture propagation. It can increase the effective fracture number and the well performance. In this paper, based on the Changning field data, a complex fracture propagation model was established. A series of case studies were investigated to analyze the effects of engineering parameters on simultaneous multiple fracture propagation. The fracture spacing, perforating number, injection rate, fluid viscosity and number of fractures within one stage were considered. The simulation results show that smaller fracture spacing implies stronger stress shadow effects, which significantly reduces the perforating efficiency. The perforating number is a critical parameter that has a big impact on the cluster efficiency. In addition, one cluster with a smaller perforating number can more easily generate a uniform fracture geometry. A higher injection rate is better for promoting uniform fluid volume distribution, with each cluster growing more evenly. An increasing fluid viscosity increases the variation of fluid distribution between perforation clusters, resulting in the increasing gap between the interior fracture and outer fractures. An increasing number of fractures within the stage increases the stress shadow among fractures, resulting in a larger total fracture length and a smaller average fracture width. This work provides key guidelines for improving the effectiveness of hydraulic fracture treatments.

Mechanisms of Simultaneous Hydraulic-Fracture Propagation From Multiple Perforation Clusters in Horizontal Wells

SPE Journal ◽  
2016 ◽  
Vol 21 (03) ◽  
pp. 1000-1008 ◽  
Author(s):  
Kan Wu ◽  
Jon E. Olson
Keyword(s):  
Flow Rate ◽  
Flow Resistance ◽  
Fracture Propagation ◽  
Propagation Model ◽  
Additional Stress ◽  
Hydraulic Fractures ◽  
Multiple Fracture ◽  
Negative Effects ◽  
Multiple Fractures ◽  
Effects Of Stress

Summary Simultaneous multiple-fracture treatments in horizontal wellbores are becoming a prevalent approach to economically develop unconventional resources in shale reservoirs. One challenge to efficiently use the technique is the generation of effective hydraulic fractures from all perforation clusters. In this work, we conducted a fundamental study of physical mechanisms controlling simultaneous multiple-fracture propagation and discussed the potential approaches to improve nonuniform development of multiple fractures. This study was investigated by our recently developed 3D fracture-propagation model that captures the coupled elastic deformation of the rock with fluid flow in the horizontal wellbore and within the fractures. The model demonstrated that fracture geometry was controlled by both the stress-shadow effects and dynamic partitioning of flow rate. The analysis results indicated that the nonuniform development of a multiple-fracture array, for example, a three-fracture array in this study, was induced by the uneven partitioning of flow rate into each fracture, which was dependent on the flow resistance from wellbore friction, perforation friction, and fracture propagation. Furthermore, the stress shadowing from the exterior fractures exerted additional stress on the interior fractures and increased the resistance of fracture propagation, resulting in the interior fractures receiving much less fluid. To minimize the negative effects of stress shadowing and favor more-uniform fracture growth, we investigated potential approaches to promote uniform partitioning of flow rate through adjusting the flow resistance between multiple fractures. The results showed that adjusting perforation friction can provide an effective way to modify the partitioning of flow rate and mitigate the negative effects of stress shadowing. The mechanisms investigated in this study are consistent with field observations. Our approach can help field operators to improve the effectiveness of multiple fracturing treatments and maximize the production.

scholarly journals Impact of geomechanical heterogeneity on multiple hydraulic fracture propagation

2021 ◽  
Vol 18 (6) ◽  
pp. 954-969
Author(s):  
Yunlin Gao ◽  
Huiqing Liu ◽  
Chao Pu ◽  
Huiying Tang ◽  
Kun Yang ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Fracture Propagation ◽  
Poisson's Ratio ◽  
Sequential Gaussian Simulation ◽  
Hydraulic Fractures ◽  
Multiple Fractures ◽  
Shadow Effect ◽  
Stress Shadow

Abstract To extract more gas from shale gas reservoirs, the spacing among hydraulic fractures should be made smaller, resulting in a significant stress shadow effect. Most studies regarding the stress shadow effect are based on the assumption of homogeneity in rock properties. However, strong heterogeneity has been observed in shale reservoirs, and the results obtained with homogeneous models can be different from practical situations. A series of case studies have been conducted in this work to understand the effects of mechanical heterogeneity on multiple fracture propagation. Fracture propagation was simulated using the extended finite element method. A sequential Gaussian simulation was performed to generate a heterogeneous distribution of geomechanical properties. According to the simulation results, the difficulty of fracture propagation is negatively correlated with the Young's modulus and Poisson's ratio, and positively correlated with tensile strength. When each of the multiple fractures propagates in a homogeneous area with different mechanical properties, the final geometry of the fracture is similar to homogeneous conditions. When the rock parameter is a random field or heterogeneity perpendicular to the propagation direction of fracture, the fracture will no longer take the wellbore as the center of symmetry. Based on the analysis of fracture propagation in random fields, a small variance of elastic parameters can result in asymmetrical propagation of multiple fractures. Moreover, the asymmetrical propagation of hydraulic fractures is more sensitive to the heterogeneity of Poisson's ratio than Young's modulus. This study emphasises the importance of considering geomechanical heterogeneity and provides some meaningful suggestions regarding hydraulic fracturing designs.

The effects of inclusions and heterogeneous stress field on hydraulic fracture

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. MR153-MR166
Author(s):  
Yao Yao ◽  
Kaimin Wang ◽  
Tao Zeng ◽  
Leon M. Keer
Keyword(s):  
Numerical Analysis ◽  
Stress Field ◽  
Hydraulic Fracture ◽  
Oil And Gas ◽  
Gas Production ◽  
Fluid Viscosity ◽  
Multiple Fractures ◽  
Stress Shadow ◽  
Fracture Simulation ◽  
Fracture Development

Hydraulic fracture technology has been widely applied to improve unconventional oil and gas production. The prevailing numerical analysis for hydraulic fracture technology is mainly based on the assumption of a homogeneous reservoir. However, unconventional reservoirs usually have complicated geologic conditions and the hypothesis of the homogeneous reservoir can strongly affect the accuracy of fracture simulation. To better understand the influence of heterogeneity to hydraulic fracture development, the effects of inclusions and heterogeneous stress fields are investigated by using the extended finite-element method. The heterogeneous stress field with fracture processing is developed, and the corresponding interaction between fracture and inclusion is investigated. The effects of different inclusions positions, opening and rotation angles, fractures lengths, and injected fluid viscosities to the hydraulic fracture development are studied based on the developed numerical model. Compared with the homogeneous stress field, numerical analysis indicates that the heterogeneous stress field could affect fracture behaviors and change the fracture energy distribution. In addition, the effects of inclusion can be restricted to some extent with higher injected fluid viscosity. The “stress shadow” effect with multiple fractures can weaken the influence of inclusions with properly designed perforation locations, which may be applied to optimize the hydraulic fracture development.

scholarly journals The Effect of Perforation Spacing on the Variation of Stress Shadow

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4040
Author(s):  
Weige Han ◽  
Zhendong Cui ◽  
Zhengguo Zhu
Keyword(s):  
Compressive Stress ◽  
Reservoir Rock ◽  
Hydraulic Fractures ◽  
Extended Finite Element ◽  
Gas Reservoir ◽  
Fracture Length ◽  
Shadow Effect ◽  
Stress Shadow ◽  
Initiation Pressure ◽  
Small Perforation

When the shale gas reservoir is fractured, stress shadows can cause reorientation of hydraulic fractures and affect the complexity. To reveal the variation of stress shadow with perforation spacing, the numerical model between different perforation spacing was simulated by the extended finite element method (XFEM). The variation of stress shadows was analyzed from the stress of two perforation centers, the fracture path, and the ratio of fracture length to spacing. The simulations showed that the reservoir rock at the two perforation centers is always in a state of compressive stress, and the smaller the perforation spacing, the higher the maximum compressive stress. Moreover, the compressive stress value can directly reflect the size of the stress shadow effect, which changes with the fracture propagation. When the fracture length extends to 2.5 times the perforation spacing, the stress shadow effect is the strongest. In addition, small perforation spacing leads to backward-spreading of hydraulic fractures, and the smaller the perforation spacing, the greater the deflection degree of hydraulic fractures. Additionally, the deflection angle of the fracture decreases with the expansion of the fracture. Furthermore, the perforation spacing has an important influence on the initiation pressure, and the smaller the perforation spacing, the greater the initiation pressure. At the same time, there is also a perforation spacing which minimizes the initiation pressure. However, when the perforation spacing increases to a certain value (the result of this work is about 14 m), the initiation pressure will not change. This study will be useful in guiding the design of programs in simultaneous fracturing.

Local Stress Shadow Effect Analysis in Multistage Hydraulic Fracturing Design Considering Small Drillhole Spacing

2017 ◽  
Author(s):  
V. Karpov ◽  
N. Parshin ◽  
A. Ryazanov ◽  
A. Moiseenko ◽  
A. Bochkarev ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Local Stress ◽  
Effect Analysis ◽  
Shadow Effect ◽  
Multistage Hydraulic Fracturing ◽  
Stress Shadow

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

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.

Chip Removal by a Hydraulic Jet

1964 ◽  
Vol 4 (01) ◽  
pp. 21-25 ◽  
Author(s):  
J.B. Cheatham ◽  
J.G. Yarbrough
Keyword(s):  
Flow Rate ◽  
Particle Density ◽  
Experimental Studies ◽  
Fluid Viscosity ◽  
Drill Bit ◽  
Hole Size ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Jet Velocity ◽  
Chip Removal

Abstract Although adequate removal of cuttings from beneath a drill bit is important for efficient drilling operations, very little basic data are available relative to the fundamentals of chip removal by hydraulic jets. A discussion is presented in this paper of an experimental investigation of the jetting action of hydraulic jets in removing loose particles from the bottom of a cylindrical hole. Conditions for which the jet is no longer capable of removing chips from the bottom of the hole are determined. This situation represents equilibrium between the chip removal force and chip holddown forces such as gravity and pressure. In most of the tests loose particles were jetted with water or a water-glycerine mixture to determine the dependence of chip removal on hole size, jet size, height of jet off bottom of hole, flow rate, particle density and fluid viscosity. A test with a pressurized mud system indicated that relatively low pressures can completely overcome the removal action of a hydraulic jet. Although the system studied herein is not directly applicable to a rotary drill bit, the work with such simplified systems can provide a better understanding of the chip removal action of jets, and with logical extensions it may provide a reasonable basis for the best use of fluid jets in drilling. Introduction The primary deterrent to maximum drilling rates is the inability of the drilling system to remove rock cuttings efficiently enough to prevent interference with the drilling action. The objective of chip removal studies is to permit predicting and controlling removal forces under downhole drilling conditions. Conditions at the bottom of a hole during rotary drilling are exceedingly complex and are not likely to be described in a quantitative way by investigations in terms of the total drilling action until a better understanding is developed of the simplified components of the problem. The present study is concerned with the elementary condition of removal of chips by a single central jet. Even this relatively simple model provides mathematical difficulties because of the turbulent nature of the flow from the jet and because of the shape of the bottom of the hole beneath the jet. Theoretical and experimental studies have been made of turbulent jets impinging normally on an infinite body and deductions based on analytical solutions to simplified problems can give some insight into the problem of cutting removal by a jet. However, because of the present lack of understanding of the behavior of the interaction between the fluid jet and the chips being removed, an experimental approach was chosen for the present study. Methods have been developed for maximizing hydraulic horsepower, impact force and jet velocity; but whether maximizing these parameters maximizes chip removal with present drilling bits has not been demonstrated. Simplifying the problem of chip removal may make it possible to develop some understanding of the manner in which the jet velocity is dissipated. Better understanding of a simple case should materially assist in extending analysis to more complicated cases. Thus, we are not concerned in the present study with the rock fracturing process itself but only with the removal of the debris from the bottom of the hole. A problem which is quite similar to the chip removal problem is the suspension of solids in stirred vessels. This problem has been studied by the chemical industry and correlations have been obtained by dimensional analysis which permit the design of mixing vats. An approach similar to that used in the mixing vat problem is used in the analysis of the jetting data in the present paper. EXPERIMENTAL PROCEDURE The test equipment arrangement shown schematically in Fig. 1 allows the jetting action to remove particles until an equilibrium height is attained for each combination of hole size, jet size and flow rate.*** Equilibrium conditions require that the removal force is unable to remove additional particles. This balance between holddown and removal forces implies a relationship between the two forces which is constant for the particular system. When the holddown forces are constant, SPEJ P. 21ˆ

Experimental Study on the Effect of Pinch Parameters and Fluid Viscosity to Flow in Closed Loop Impedance Pump

2014 ◽  
Vol 660 ◽  
pp. 932-936
Author(s):  
M. Mazwan Mahat ◽  
R.N. Izzati ◽  
Ilya Izyan Shahrul Azhar ◽  
Izdihar Tharazi
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Supply Voltage ◽  
Maximum Flow ◽  
Elastic Tube ◽  
Fluid Viscosity ◽  
Ventricular Assist ◽  
Tube Section ◽  
Impedance Pump ◽  
Device Use

This paper aims to analyse the performance of impedance pump that uses energy mismatch to drive fluid flow. The experimental setup mainly focus to establish the relationship between the fluids flow rates in elastic tube section connected between two ends of solid tube and pinch mechanism location as well as fluid viscosity. Measurement of fluid flow rate or representation of its velocities resulting from the pumping mechanism is measured using two different supply voltage and constant pincher width. These measured parameters resulting from the pinch mechanism of the elastic tube section were varied at different pinch location along itsx-axis direction; divided into two main cases namely (1) 2 V and (2) 3 V at 40 mm to 140 mm pinch location. From the voltage variation, it is found that the maximum flow rate given by voltage 3.0 V at pinch location 40 mm while for the effect of viscosity, the highest flow rate is 93 ml/min. The profiles obtained revealed the characteristic of valve less pump to be the new model of new Ventricular Assist Device use in cardiac patient as well as further explanation about the factor that influence the characteristic of elastic tube.

NEWTONIAN AND NON-NEWTONIAN BLOOD FLOW AT A 90∘-BIFURCATION OF THE CEREBRAL ARTERY: A COMPARATIVE STUDY OF FLUID VISCOSITY MODELS

2018 ◽  
Vol 18 (05) ◽  
pp. 1850043 ◽  
Author(s):  
S. V. FROLOV ◽  
S. V. SINDEEV ◽  
D. LIEPSCH ◽  
A. BALASSO ◽  
P. ARNOLD ◽  
...  
Keyword(s):  
Blood Flow ◽  
Newtonian Fluid ◽  
Flow Rate ◽  
Fluid Model ◽  
Cerebral Arteries ◽  
High Viscosity ◽  
Flow Rate Ratio ◽  
Parent Artery ◽  
Fluid Viscosity ◽  
Recirculating Flow

The majority of numerical simulations assumes blood as a Newtonian fluid due to an underestimation of the effect of non-Newtonian blood behavior on hemodynamics in the cerebral arteries. In the present study, we evaluated the effect of non-Newtonian blood properties on hemodynamics in the idealized 90[Formula: see text]-bifurcation model, using Newtonian and non-Newtonian fluids and different flow rate ratios between the parent artery and its branch. The proposed Local viscosity model was employed for high-precision representation of blood viscosity changes. The highest velocity differences were observed at zones with slow recirculating flow. During the systolic peak the average difference was 17–22%, whereas at the end of diastole the difference increased to 27–60% depending on the flow rate ratio. The main changes in the viscosity distribution were observed distal to the flow separation point, where the non-Newtonian fluid model produced 2.5 times higher viscosity. A presence of such high viscosity region substantially affected the size of the flow recirculation zone. The observed differences showed that non-Newtonian blood behavior had a significant effect on hemodynamic parameters and should be considered in the future studies of blood flow in cerebral arteries.

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