Large-scale Physical Experiments Research Articles

Effect of Fault Slip on the Casing Passability of Horizontal Shale Oil and Gas Wells

Summary Fault slip, a secondary effect of the hydrofracture to extract shale oil and gas, deforms the casing locally and affects downhole tools going through it, hindering the exploitation plan. The casing passability is introduced to evaluate the casing passability for the downhole tool. A simulation model of the fault slip was established to analyze the effect of fault type, slip distance, and fault dip on the casing passability. Meanwhile, the simulation method adopted in this paper was verified by the large-scale physical experiments of the perforated casing subjected to uniform outer pressure. Based on the experimental results and the geometry of fault slip, an empirical formula is proposed for the relationship between casing passability and fault slip. The result shows that the sensitivity of casing passability affected by fault type is ranked from highest to lowest by strike-slip fault, normal fault, and reverse fault. This study provides a reference for determining the available diameter of downhole tools quickly and reduces the cost of exploring wells when downhole tools are obstructed.

Techniques for improving fracture-controlled stimulated reservoir volume in ultra-deep fractured tight reservoirs: A case study of Kuqa piedmont clastic reservoirs, Tarim Basin, NW China

Based on analysis of the reasons for low efficiency and low production after fracturing of some wells in the ultra-deep fractured tight reservoirs of the Kuqa piedmont zone, Tarim Basin and the matching relationship between the in-situ stress field and natural fractures, technological methods for creating complex fracture networks are proposed. Through theoretical study and large-scale physical simulation experiments, the mechanical conditions for forming complex fracture network in the Kuqa piedmont ultra-deep reservoirs are determined. The effectiveness of temporary plugging and diversion, and multi-stage fracturing to activate natural fractures and consequently realize multi-stage diversion is verified. The coupling effect of hydraulic fractures and natural fractures activating each other and resulting in “fracture swarms” is observed. These insights provide theoretical support for improving fracture-controlled stimulated reservoir volume (FSRV) in ultra-deep tight reservoirs. In addition, following the concept of volume fracturing technology and based on the results of fracture conductivity experiments of different processes, fracturing technologies such as multi-stage fracture-network acid fracturing, “multi-stage temporary plugging + secondary fracturing”, fracturing of multiple small layers by vertically softness-and-hardness-oriented subdivision, and weighted-fluid refracturing are proposed to increase the FSRV. New environment-friendly weighted-fluid with low cost and new fracturing fluid system with low viscosity and high proppant-carrying capacity are also developed. These techniques have achieved remarkable results in field application.

Real-Time Data Processing Pipeline for Trigger Readout Board-Based Data Acquisition Systems

Large-scale physics experiments running at high interaction rates place a high demand on the data acquisition system (DAQ) responsible for transporting the data from the detector to the storage. The antiProton ANihilation at DArmstadt (PANDA) at the facility for anti-proton and ion research (FAIR) is one such experiment of the future that will not use fixed hardware triggers; instead, the event selection is based on real-time feature extraction, filtering, and high-level correlations. A firmware framework for such real-time data processing has been developed and tested with hardware setup for a PANDA Forward Tracker (FT) prototype. The solution is applicable for other detector subsystems based on the so-called Trigger Readout Board (TRB) data read-out system.

Short-Term Morphological Responses of Adjacent Intertidal Flats to the Construction of Tidal Gates in an Estuarine Tributary

Tidal gates cause adverse effects on the ecological environment through the downstream acceleration of sediment deposition. This deposition process and its quantitative analysis have become a hot topic in marine science. A large-scale physical model experiment of morphological responses to the construction of a tidal gate in an estuarine tributary was performed in this study. The sediment distribution characteristics, morphologic patterns, and further analysis of the adjacent intertidal flats were investigated, triggered by the construction of tidal gates at the mouth of the Nanxi River in Zhejiang, China. The results indicated that the flood and ebb tide velocities change dramatically after the construction of the tributary tidal gates. Large amounts of sediment from the mouth of the estuary could not be entirely carried away from the flood phase to the ebb phase, resulting in downstream deposition in the vicinity of the gates. The ebb tide caused erosion of the tidal flats’ surface in the silted intertidal zone that gradually developed into a tidal channel network. The tidal channel bifurcated in the middle–upper part of the intertidal flats through continuous headward erosion, thus promoting the landward expansions of channels. Applying a set of logistic growth models to the mean sinuosity, Hausdorff dimension, and junction number data indicated that the tidal channel development progressively tended toward a state of morphodynamic equilibrium.

Depositional styles and adjustment of channel cross-sections in a seasonal deltaic system: a large-scale physical experiment

Depositional styles and adjustment of channel cross-sections in a seasonal deltaic system: a large-scale physical experiment

Numerical Simulation Study on Heat Transfer Mechanism of Excavation Based Enhanced Geothermal System

The innovative excavation based EGS (EGS-E) scheme uses mining techniques to form deep underground access for creating artificial heat reservoir with multi-level fracture networks using excavation, blasting, and caving. The two-level heat transfer mechanism of distributed artificial heat reservoir has a dominant influence on the performance of excavation based Enhanced Geothermal System(EGS-E). However, due to the large-scale field testing and laboratory physical experiment are not yet realistic, the process of natural convection heat transfer within the surrounding rock enhanced permeability and water filled zones hasn’t been effectively studied. The simulation software COMSOL Multiphysics was used to numerically simulate the natural convection heat transfer within the enhanced stimulated surrounding rock around a single straight roadway with its circular opening, which should be an elemental unit for mining heat in deep underground engineering structure. The simulation results demonstrated that the temperature difference inside the surrounding rock of a roadway causes the density of working fluid to vary. Driven by buoyancy, the natural convection of working fluid occurs in the surrounding rock. It enhances the heat transfer inside hot dry rock, and its efficiency is significantly more remarkable than that of the conduction through hot dry rock itself, which can improve the efficiency of heat recovery with regards to EGS-E. Due to the low solid heat conduction efficiency of the surrounding dry hot rock, adjusting the speed of the water flow inside the pipe can effectively control the temperature of the water outlet to improve the heat collection life of the system.

Effect of molecular carbon structures on the evolution of the pores and strength of lignite briquette coal with different heating rates

Briquette coal (BC) is the material produced from coal and gas outburst experiments. Preparing BC via the heating and pressure method can improve its low mechanical strength in physical simulation tests and gas outbursts while increasing experimental reliability. However, the influence of heating rate on the mechanical properties and microstructure of BC and the reasons underlying the evolution of its mechanical strength analyzed in terms of carbon molecular structure still need to be further studied. In this study, we developed an experimental system to prepare BC. The influence of the pore and carbon molecular structure on the BC uniaxial compressive strength was examined via a rock mechanics test system, scanning electron microscopy, nuclear magnetic resonance, specific surface area analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that when the heating rate was increased from 3 to 6 °C/min, the briquette structure changed from looser smooth sheets to rough agglomerates of coal. The pore types observed after four different heating treatments (3, 4, 5, and 6 °C/min) on briquette samples were primarily micropores and mesopores. At 5 ℃/min, the number of micropores in the briquette sample were significantly higher than that observed in other samples. All samples exhibited similar adsorption curves as those of inverted “S”-type coal samples, which can be regarded as a combination of Type IV isotherms. With increasing heating rates, the La and Lc first increased and then decreased, with a decrease in Aar/Aal, whereas Hal/H and CH2/CH3 increased. The strength of coal samples under the increasing heating rates were 5.62, 6.43, 7.07, and 5.99 MPa, respectively. The heating rate of 5 ℃/min was found to be the appropriate heating rate for briquette preparation. These results can provide an excellent alternative raw material required for large-scale physical simulation experiments for the prevention and control of coal and gas outbursts.

Effect of heating on the molecular carbon structure and the evolution of mechanical properties of briquette coal

Preparing briquette coal (BC) via the heating and pressure method can improve its low mechanical strength in physical simulation tests and gas outbursts while increasing experimental reliability. However, the influence of temperature on the mechanical properties of BC, microstructure, and the reasons underlying the evolution of mechanical strength of BC analyzed in terms of the carbon molecular structure of coal still need to be further studied. For this purpose, a rock mechanics test system, scanning electron microscopy, X-ray diffraction, and Fourier Transform Infrared Spectroscopy were used to analyze the optimum temperature for BC preparation and identify how the heating temperature affects the molecular carbon structure of BC to increase its strength. The result showed that as the temperature increases from 150 °C to 600 °C, the aromatic d002 layer spacing decreased, whereas the aromatic layers of La and Lc increased, leading to an order degree increase of coal molecules. In addition, Hal/H and CH2/CH3 decreased, whereas Aar/Aal increased, indicating that the aliphatic chains shortened and the aromaticity increased, ultimately improving the strength of BC. However, when the temperature exceeds 300 °C, the pores suffers damage, increasing the width of the pores and crack. Through uniaxial compression, the mechanical strength of BC first increases and then decreases. Moreover, the mechanical strength, Poisson's ratio, and elastic modulus at 300 °C were close to that of raw coal (RC). These results provide guidance to prepare excellent raw materials needed for large-scale physical simulation experiments to prevent and control coal and gas outbursts.

A Clock Distribution and Synchronization Scheme Over Optical Links for Large-Scale Physics Experiments

In large-scale physics experiments, there is a trend to implement clock distribution and synchronization over multi-Gigabit serial links on optical networks. The accuracy of clock synchronization in such a fashion is mainly determined by two aspects: one is the stability of the clock distribution over the links, and the other is the employed mechanism of clock synchronization. To achieve a high synchronization accuracy in a range of tens of picoseconds, this article proposes a new optical fiber link and synchronization scheme based on optical circulators and serial transceivers embedded in field-programmable gate arrays (FPGAs). Benefiting from the single wavelength fiber connection, high-precision time-to-digital converters (TDCs) and phase interpolator (PI) sub-block in state-of-the-art Serializer-Deserializer (SerDes) transceivers on FPGAs, the offset of distributed clocks can be measured on-line and precisely compensated. The time synchronization performance is evaluated on a prototype system with three levels of structure. Through multiple power or reset cycles and long-term operation tests, the clock synchronization accuracy over a 5-km fiber connection is measured to be lower than 15 ps, and the recovered clocks at nodes at different levels have independent jitter, all lower than 4.2 ps. In addition, the achieved high performance is also proved to be insensitive to operating temperature and the connection distance.

Experimental Study on Stress Transfer and Fracture Law During the Hydraulic Fracturing of Coal Seams

Hydraulic fracturing is a key technology for increasing the permeability of coal seams and improving the extraction effect of coalbed methane. Exploring the parameters that represent the infiltration effect is an essential part of the optimization process of hydraulic fracturing. In this work, based on a similarity principle design, a hydraulic fracturing test was carried out on large raw coal samples using an indoor hydraulic fracturing physical simulation test system. Based on the distribution of primary cracks in the coal samples, the law of crack extension during hydraulic fracturing was studied. The stress variations before and after hydraulic fracturing of the coal seams were monitored, and the stress transfer laws during confining pressure loading and hydraulic fracturing were investigated. The experiment showed that the new fissures in the fracturing process are more likely to extend to the primary fissure development area. When the applied coal body stress exceeds the strength of the coal sample body, the internal cracks in the coal sample are completely penetrated. During this complete penetration, the energy accumulated by pressure water injection is continuously released, and the count detected by the acoustic emission increases sharply. The coal is mainly subjected to compressive stress during the confining pressure loading process, whereas the coal body is mainly subjected to a shear stress during the hydraulic fracturing process. Both the stresses can be transferred through the coal samples. When the stress increase during hydraulic fracturing is greater than the confining load, the overall effect is due to different stresses. As the cracks continue to expand and extend during hydraulic fracturing, the stress transfer effect becomes weaker. Through the exploration of the law of crack extension and stress transmission, this experiment showed that large-scale physical simulation experiments in a laboratory setting can help effectively simulate on-site hydraulic fracturing conditions. The test method and results reported herein provide a reference and basis for the design and optimization of on-site hydraulic fracturing parameters.

Multistage Acid-fracturing Increases the Dolomite Production in High Temperature Deep Horizontal Well

The Sinian dolomite reservoirs in Southwest Oil and Gas Field, China, are characterized by HTHP, high stress, low porosity and permeability, large thickness, and presence of natural fractures and holes. Highly deviated well multistage acid fracturing can help expand the contacting area between wellbore and reservoir, thereby increasing the well production. Through experiments, acid fracturing simulations, staging optimization and field applications, some conclusions were obtained. Large-scale physical modelling experiments and numerical simulations show that, given the high horizontal stress difference, presence of natural fractures, can induce a complex fractures networks. The acid systems with different viscosities, such as self-generating acid, gelled acid and diverting acid, are optimized to, in conjunction with highrate injection and temporary diverting, improve the stimulated reservoir volume and conductivity of acid-fractures in the dolomite reservoirs. The combination of mechanical packers and sliding sleeves facilitate the effective isolation of HTHP dolomite reservoir. The positions of the sliding sleeves are designed according to the high-quality reservoir intervals determined by logging interpretation. The lateral of deviated well is 480m-970m long and stimulated by acid fracturing in 3-6 stages. The post-fracturing tracer testing proves the effectiveness of isolation. This technology was applied for 6 wells, with a daily gas production of (21–110) × 104m3/d after acid fracturing. It provides a new method to increase the production of highly deviated wells or horizontal wells in deep carbonate reservoirs.

Numerical implementation of bounding-surface model for simulating cyclic inelastic response of metal piping components

The present paper describes the numerical implementation of the bounding-surface cyclic-plasticity model in a finite element environment, suitable for simulating the structural behavior of metal components subjected to strong cyclic loading. The model is based on the Dafalias-Popov “bounding surface” concept, equipped with appropriate enhancements that allow for simulation of repeated, alternate inelastic deformation. The numerical implementation is performed using an elastic-predictor/plastic-corrector method. Special features of the model are examined, focusing on the influence of several material parameters on cyclic material response. The model is also employed for simulating laboratory physical experiments. First, stress-controlled and strain-controlled experiments are simulated, in strip specimens made of regular (mild) steel and high-strength steel. Upon appropriate calibration from these material tests, the model is employed in a finite element model for predicting the mechanical response of a large-scale physical experiment on a steel pipe elbow. The very good comparison between the experimental and the numerical results demonstrates the suitability of the numerical model for large-scale structural computations and its capability of predicting the mechanical response of structural metal components under severe repeated loading, with emphasis on the simulation of ratcheting.

Numerical simulation of the mechanical behaviour of steel pipe bends under strong cyclic loading

The present study uses advanced numerical tools to examine the mechanical behavior of steel pipe bends (elbows), subjected to strong cyclic loading, associated with repeated plastic deformations of alternate sign. The elbows are modeled with finite elements, accounting for the measured elbow geometry and the actual properties of steel elbow material. The main feature of the present work is the simulation of material response using an advanced cyclic-plasticity model, based on the bounding-surface concept, implemented through an in-house material subroutine. Upon appropriate calibration with material tests in strip specimens, extracted from the bends under consideration, the constitutive model is employed for predicting the mechanical response of large-scale physical laboratory experiments. Very good predictions are obtained in terms of global load-displacement response, as well as in terms of local strains and their accumulation over the loading cycles (ratcheting) at specific elbow locations. This indicates that the bounding-surface model can be an efficient tool for predicting accurately the mechanical response of piping components under severe cyclic loading conditions. Finally, using the validated numerical models, extensive results are obtained, focusing on the effects of internal pressure on strain accumulation at specific locations of the elbow, for three values of pipe thickness.

Clock-Centric Serial Links for the Synchronization of Distributed Readout Systems

Detector readout systems for medium to large scale physics experiments, and instruments in some other fields as well, are generally composed of multiple front-end digitizer boards distributed over a certain area. Often, this hardware has to be synchronized to a common reference clock with minimal skew and low jitter. Today's mainstream solutions to precise clock distribution and deterministic latency messaging rely on the capabilities of high speed serial transceivers (a.k.a. SerDes) embedded in modern Field Programmable Gate Arrays (FPGAs). An alternative option uses distinct clock and data links. This can potentially reach higher synchronization accuracy, at significant hardware expenses. This work reports some first steps to explore a third scheme for clock and synchronous message distribution. Like the standard approach, the same media is used to convey clock and data, but instead of using today's "data-centric" links where the recovered clock is only a by-product of a SerDes, this paper defines and investigates "clock-centric" links where, at the opposite, a clock is carried by the link, and synchronous data are embedded into it by a modulation technique. After defining the concepts and principles of data-centric links, experimental studies are presented. Finally, the merits and limitations of the proposed approach are discussed.

Experimental study on combining heterogeneous phase composite flooding and streamline adjustment to improve oil recovery in heterogeneous reservoirs

The heterogeneity of reservoirs is the key factor restricting the development performance of oilfields. Heterogeneous phase composite flooding (HPCF) and streamline adjustment (SA) are both viable strategies for improving oil recovery of heterogeneous reservoirs. However, both strategies have their own deficiencies, which limits further development. In recent years, a hybrid strategy combining HPCF and SA has attracted considerable interest from oil industry. In this paper, two-dimensional (2D) large-scale physical model experiments were performed to verify whether the hybrid strategy could offer better development performance than the single strategy, and the mechanism of hybrid strategy for improving oil recovery was elucidated. On this basis, the influence of SA angle on improved development performance was investigated. Finally, the affected regions of remaining oil in different strategies were proposed. The experimental results indicate that HPCF can effectively improve sweep efficiency and oil displacement efficiency in the main streamline regions; furthermore, it prolongs the time of incremental oil production. Streamline adjustment can forcibly utilize the remaining oil in the low-permeability regions at non-main streamline where water flooding and HPCF are poorly affected. The hybrid strategy can give full play to the respective strengths of each single strategy. Meanwhile, SA provides a good induction effect on HPCF, which creates an excellent opportunity for the latter to effectively displace the remaining oil in the low-permeability regions at non-main streamline over extended periods. When the SA angle is 90°, the best development performance can be achieved. The affected regions of remaining oil in different strategies were proposed in this paper, which affords significant guidance for effective development of heterogeneous reservoirs.

An extended finite element method for the prediction of acid-etched fracture propagation behavior in fractured-vuggy carbonate reservoirs

Acid fracturing is an important method of achieving high-efficiency economic development of carbonate reservoirs. The propagation of acid-etched fractures is affected significantly by geological discontinuities such as natural fractures and limestone caverns. Therefore, acid-etched fractures in carbonate reservoirs also differ greatly in morphology to those inhomogeneous reservoirs. However, no clear propagation mechanism has been available to describe and predict the propagation behavior of acid-etched fractures. In order to investigate the process, based on the extended finite element method, a set of acid-etched fracture propagation models for fracture-vuggy reservoirs, including mechanical, hydro and acid-rock reaction modules, were established. The effect of vuggy, natural fracture and acid on the initiation and propagation of induced fracture, the surface morphology of the acid-etched fractures, the effects of the number of perforation clusters, and natural limestone caverns, were considered. The calculated geometric size of the fracture was compared with the results based on the CGD (Christianovich-Geertsma-Daneshy model) model, for validating the reliability of the present model. The effects of the injection fracturing liquid type and the number of perforation clusters on fracture initiation position, propagation path, and surface morphology were evaluated. The calculation results also were compared with large-scale tri-axial physical experiment data. Finally, the fracture propagation behavior in rock samples containing natural fractures and limestone caverns was simulated in order to examine examining the effects of the limestone caverns with different sizes at different positions on the propagation path of acid-etched fractures. The interaction between induced fractures and limestone caverns was discussed. The induced fractures priority was given to activating natural fractures around the wellbore and extending along the natural fractures and tended to be deflected from the maximum horizontal principal stress direction due to the existence of caverns arrested fractures to a certain degree.

Numerical Modeling of Wave Feature to Enhance the Performance of Buried Steel Pipelines Subjected to Faulting Displacements

Earthquake-induced permanent ground deformations are among the most important causes of damage to lifelines. Buried pipelines are longitudinal structures that are prone to be exposed to the faulting displacements. Improving the performance of these lifelines is of particular importance. This research numerically investigates the effect of a recently introduced wave feature (segments with rotational and axial flexibilities) on the behavior of buried pipes subjected to the displacement of the strike-slip faulting. Three-dimensional nonlinear finite element simulations were conducted in which the pipe and wave feature were modeled by shell element and peripheral soil was modeled by three-dimensional continuum elements. The accuracy of numerical simulations was examined by comparing the results with large-scale physical experiment. The comparison shows that the results of numerical modeling are in good agreement with experimental results. As an advantage of a calibrated numerical simulation, it is possible to extend the range of predictions and get the generalized response of the system in other geometrical and boundary conditions in which the experimental data are not available. In order to study the effect of the wave feature joint on the behavior of buried pipeline, the results were compared with a pipe with identical conditions in which the wave feature was not installed. It was found that wave feature substantially reduces the longitudinal forces and strains and preserves the cross-sectional area of the pipeline. Therefore, it considerably improves the performance of the pipe against faulting displacements.

Experimental Study on Structural Form and Excavation Model of Urban Metro Cross Transfer Station with Super Large Cross Section and Shallow Excavation

The construction of urban underground cross‐interchange transfer subway stations often encounters the difficulties of shallow‐buried, different surrounding rock, large spans and heights, congested road traffic, and surrounding buildings sensitive to the construction sequence. Therefore, there is a need for an underground project that controls the stability of underground space and ground subsidence. Based on the construction difficulties of a certain station (the maximum excavation area over 760 m2), this paper conducts a comprehensive selection design of the structure, construction mechanics response, and control technology of this type of interchange station structure and construction excavation. First of all, based on the design experience of large‐scale underground transfer transportation engineering and taking full consideration of the stratum conditions, an “arch‐wall” cross transfer structure method is proposed. The refined numerical analysis shows that the structure can fully utilize the stratum conditions to reduce the ground surface settlement. Then, in view of the stability of surrounding rock during the construction of a large section, based on the traditional large section excavation method, a construction method of “cross rock beam + heading method” was proposed. In order to verify the effect of the construction method, the three‐dimensional detailed numerical model was used to simulate the construction conditions, and the mechanical response characteristics and displacement changes of surrounding rock under each excavation step are explored. Simultaneous interpreting with the traditional large section excavation method, the results show that the new method has advantages in controlling the stability of the surrounding rock. Meanwhile, in order to ensure the safe construction of the project, the self‐developed multifunctional engineering test system for traffic tunnels is used to carry out a large‐scale physical model experiment to simulate the entire process of the “arch‐wall” cross transfer structure construction response characteristics. By analyzing the data of measuring points, the results show that the structure form and the excavation method cause the ground surface settlement, stress, and structural forces meet the requirements for safe construction. Finally, the station can be safely constructed under the new structure form and construction method. Therefore, the structure form and method proposed in this paper can be adapted to the large‐scale underground structure under construction in complex environments.

Laboratory and field-scale parameter optimization of CO2 huff–n–puff with the staged-fracturing horizontal well in tight oil reservoirs

With the help of large-scale physical simulation experiment technology, the physical simulation experiments of the CO2 huff–n-puff with the staged-fracturing horizontal well could be acheived. We studied the production process of CO2 huff–n–puff and influence of different parameters affect oil recovery during the CO2 huff-n-puff procedure, ultimately, the operation parameters were optimized by numerical simulation. The results show that CO2 can quickly enter the deep formation through the horizontal well and the fracture during the huff period and staged-fracturing horizontal well can greatly increase the contact area between CO2 and crude oil, which improves the efficiency of extraction, dissolution, reduction of viscosity between CO2 and crude oil. During the puff period, the horizontal well and fractures can reduce the flow resistance effectively, so as to improve the flow capacity of crude oil. After 3 cycles of CO2 huff and puff, the oil recovery can be enhanced by 11.13%~21.39% compared with that obtained by elastic flooding, which indicates that the exploitation method of CO2 huff–n–puff can improve the development effects of tight oil reservoirs. CO2 huff-n-puff injection parameters are optimized, the results show that the optimum time of injection is 1 year, the optimum soaking time is 30d, and the optimal injection pore volume is 0.18HCPV. This research can provide a certain technical support for effective development of tight oil reservoirs.

Research and Application of Radial Borehole Fracturing Based on Numerical Simulation

The radial borehole fracturing technology has been applied in a certain number of oilfields with good results being achieved. However, the morphology and variation of fracture still require further study. In this paper, the reservoir model based on formation fluid-solid coupling equation is established with the extended finite element method (XFEM) in ABAQUS, and the fracture morphologies in the single-radial borehole, vertical multiradial borehole, and horizontal multiradial borehole are simulated and analyzed with criteria of maximum principal stress and maximum energy release rate as the damage mechanism. Moreover, the accuracy of numerical simulation results is verified with the large-scale true 3D physical simulation experiment. The results show that the induced stress field along the radial borehole during fracturing is the root cause of fracture directional propagation along the radial borehole whose effective guidance distance reaches 40 m. The vertical multiradial borehole can effectively enhance fracture directional propagation and is capable of reducing fracture initiation pressure. In the horizontal multiradial borehole, the major fracture propagating along each radial borehole is formed in the remote-borehole area, and the secondary fracture connecting the neighboring radial boreholes is formed in the near-borehole zone. Coordination of major and secondary fractures can effectively increase the drainage area and reduce the flow resistance in the near-borehole zone. Based on the research on fracture morphology of multiradial borehole fracturing, the scheme of radial borehole arrangement is optimized and verified through numerical simulation of deliverability. The final optimum borehole arrangement scheme is the intersectional angle of 45° between four orthogonal radial boreholes and horizontal maximum principal stress.