Perforation Tunnels Research Articles

Understanding cone crack formation in cosmic dust aerogel collectors by low-velocity similitude impact test

Low-density silica aerogel is an ideal medium for capturing cosmic dust in space, as the perforated tracks provide valuable insights into the characteristics of interplanetary particles. However, the mechanism behind track formation remains unclear. This paper examines the skirt-shaped or cone-in-cone cracks commonly observed in both ground experiments and returned aerogel samples. Similitude impact tests using various techniques compare cone cracks formed at different velocities. Results show that cone cracks typically form at lower impact velocities. Additionally, impact tests with hard spherical projectiles at speeds below 50 m/s, conducted using an electromagnetic coilgun, produced multiple tracks with single cone cracks. The impact process is captured in real-time using a high-speed camera, and the formation mechanism is investigated. A theoretical model, based on contact mechanics and energy methods, is developed to quantify the relationship between cone crack morphology and projectile impact parameters. The model's accuracy is validated through experimental results. This study reveals the formation of cone cracks in penetration tracks within silica aerogel. The proposed model identifies the energy absorption mechanism during single cone crack formation, potentially improving the understanding of key parameters (initial size, composition, velocity distribution, astrophysical source) from the perforated tunnels in cosmic dust aerogel collectors.

Study on transient prediction method of dynamic underbalanced pressure after perforation detonation in ultra-deep wells

Dynamic underbalanced pressure creates a significant transient pressure difference between the upper and lower ends of the packer and the inner and outer walls of the string below the packer, which can lead to the failure of the packer, the tubing, and the casing and is one of the main reasons for the low success rate of the perforation-acidizing-testing combined technology in ultra-deep wells. A danger caused by the dynamic underbalanced pressure is increased rapidly with an increase in the well depth. Despite the fact that researchers have a well enough understanding of the applications and benefits of the dynamic underbalanced pressure, the mechanism of the wellbore failure caused by the dynamic underbalanced pressure is inadequate. Therefore, a pressure drop model of tubing-casing annulus fluid is established, and a seepage model of reservoir rock is given. A transient prediction method of the dynamic underbalanced pressure is developed by coupling the pressure drop model and the seepage model. Then, the determining factors, key nodes of the maximum value, and derivation and propagation laws of the dynamic underbalanced pressure are revealed. An influence study focusing on an ultra-deep well is conducted. The obtained results indicated that the dynamic underbalanced pressure describes a fast drop in the annulus fluid pressure caused by the fluid flow among the annulus, the perforating guns, and the perforation tunnels since the pressures in the perforating guns and the perforation tunnels are lower than the annulus pressure after the perforation detonation. The annulus fluid pressure can slowly recover and increase due to the fluid flow between the screens and the annulus and the fluid flow between the reservoir rock and the wellbore. The main form of the wellbore failure caused by the dynamic underbalanced pressure is the casing collapse deformation. Therefore, changing perforating conditions, wellbore conditions, and reservoir rock conditions can increase the maximum for the dynamic underbalanced pressure to improve the success rate of the combined technology. The research presented in this paper can provide a new understanding and prediction method of the dynamic underbalanced pressure.

Numerical investigation of the effect of perforated almond, tunnel, and bishop shaped pin fin heat sinks on the hydrothermal performance enhancement

The pin-fin design of the heat sink optimizes thermal dissipation by enhancing surface area and enabling efficient heat transfer in high-performance devices. The primary objective of the highly functionalized and convenient heat sink is to provide a competitive advantage in the field of efficient thermal management systems. The primary objective of this study is to investigate various designs of pin-fin heat sinks with unique shapes. These heat sinks are intended to operate in varying dynamic situations and necessitate an efficient convective heat transfer. The current technique has been thoroughly confirmed using earlier research, and computational investigations were conducted to improve the hydrothermal performance of staggered organized pin-fin heat sinks compared to the baseline case adopted from previous studies. Research is underway to examine the collective impact of the fin's unique structure, ideal aerodynamic form, and quality of perforations. A simulation of three-dimensional incompressible flow was conducted using the realizable k- ԑ model to generate turbulence flow that satisfies the relevant boundary conditions for solving the governing equations. When comparing fins shaped like a bishop to the standard hemispherical instance mentioned in recent work, the Nusselt number is 33 % higher. In addition, when the Reynolds number reaches 21,367, the presence of almond-shaped fins with circular perforations leads to a significant reduction in pressure drop, namely by 53.24 %. The almond-shaped hexagonal perforated fins, formed of a copper-diamond composite material, achieved the maximum hydrothermal performance factor (HTPF) of around 1.52 at a Reynolds number of 21,367. These layouts can be considered in various industrial applications.

Experimental Evaluation of the Integrated Composite Perforation System under Simulated Tight Reservoir Conditions

This paper aims to evaluate the performance of the integrated composite perforation system in tight reservoirs. To simulate complex pressure conditions of the reservoir, a perforation test device was developed in accordance with API RP 19B sections 4.2 and 4.4 procedures, and a set of test evaluation methods was designed. Using a type 4-1/2in perforating charge and pre-propellant charge, a tight sandstone target with rock physical characteristics similar to the real reservoir were selected for the perforation test under simulated reservoir pressure, pore pressure, and wellbore pressure. The characterization of the perforation tunnel and fracture morphology using CT scanning and thin-section analysis techniques. The results show that under the simulated reservoir pressure conditions, the integrated composite perforation system reduces the penetration depth by nearly 8% compared with the conventional perforation, improves the average flow efficiency by 17.2%, and creates multiple 40mm-100mm extended fractures at the end of the tunnel, the perforation and fracture enhancement is improved by an average of 1.34 times.

Complex Flow Mechanism and Pressurization Effect of Liquid Nitrogen Jet Fracturing Formation Perforation Tunnel

As an anhydrous fracturing method, liquid nitrogen jet fracturing technology is expected to become an efficient development method for shale gas resources. In order to explore the influence of the pressurization effect in the liquid nitrogen jet channel, the flow field in the perforation tunnel during the liquid nitrogen jet fracturing process was simulated by computational fluid dynamics, and the complex flow mechanism of liquid nitrogen in the perforation tunnel was analyzed. The pressurization effect of liquid nitrogen jet and water jet fracturing was compared, and the influence of various parameters on the pressurization effect of liquid nitrogen jet fracturing was studied. The research results indicate that under the same conditions, liquid nitrogen jets have a pressurization effect comparable to water jets, and the difference between the pressurization values of the liquid nitrogen jet and the water jet in the perforation tunnel is not more than 0.4 MPa under different nozzle pressure drop conditions. The larger the nozzle pressure drop and nozzle diameter, the greater the pressure increase value in the perforation tunnel of liquid nitrogen jet fracturing, which decreases with the increase in casing hole diameter. Further analysis shows that the pressurization effect is most affected by the two parameters of casing hole diameter and nozzle diameter. The essential reason for its influence on the pressurization value is the squeezing effect of the jet on the perforation tunnel fluid and the sealing effect of the shrinking part of the perforation tunnel on the backflow. The ambient pressure, the temperature of liquid nitrogen, and the diameter of the wellbore have no obvious effect on the pressurization effect. Therefore, through the reasonable combination of casing hole diameter and nozzle diameter, the sealing effect of the contraction part of the perforation tunnel on the fluid and the squeezing effect on the fluid in the perforation tunnel will be affected, which will significantly improve the pressurization effect of the liquid nitrogen jet in the perforation tunnel.

Numerical simulation of near wellbore fracture propagation in interbedded continental shales with competing perforations

To reduce near wellbore fracture complexity in continental laminated shales, in-plane perforations completion technology is introduced. The global embedded cohesive elements are capable to simulating arbitrary fracture propagation growth while the laminae effects on fracture propagation path can be considered in established finite element model. Numerical simulations reflect that the existence of weak micro fractures only locally alter the fracture propagation path but laminae can change the fracture propagation path greatly. Furthermore, the in-situ stress anisotropy, pump rate, perforation intersection angle and perforation angle with laminae are critical factors for affecting the fracture propagation path and breakdown pressure. There is a great impact of laminae on the fracture branching at the contact interface and hydraulic fracture tends to cross laminae at high approaching angle but propagate horizontally along laminae at low approaching angle. In most cases, hydraulic fracture tends to propagate along the laminae rather than across the laminae. The adjustment of pump rate, fluid viscosity, perforation intersection angle and perforation angle with laminae can enhance the possibilities of hydraulic fracture across laminae. It was also found that hydraulic fractures induced from different perforations can interact and overlap with each other, resulting in different fracture geometry and pressure behavior for individual fracture. The fracture width of interior fracture is almost close at the near wellbore zone at the end of pumping, and exterior fractures generally deviated away from the perforation tunnel direction because of stress interference of neighboring fractures. Additionally, although a fracture initiated initially from a perforation tunnel to short distance, hydraulic fractures still finally would reorient itself to maximum principle in-situ stress direction, thus increase more chances of creating one large and main fracture along the maximum principle in-situ stress orientation with larger horizontal stress contrast. Therefore, the existence of laminae can enhance the potential of fracture complexity near wellbore but the selection of suitable perforation scenarios in one defining plane can increase the possibility of form a main fracture. The simulation results from this study offer some important insights to hydraulic fracturing design with multiple perforations on interbedded continental shales stimulation.

Performance simulation and perforated parameters optimize for perforated wells with compaction zone and drilling damage in tight gas reservoirs

It is essential to understand how to improve the production of perforated well in tight reservoirs. In this paper, based on the experiment of experiment evaluation of perforation tunnel and perforation compaction zone, the drilling mud invasion zone and stress sensitivity, a new productivity numerical model is established considering the damaged zone being drilling, and the compaction zone being penetrated and the sensitivity in tight gas reservoirs. Considering perforation interaction, drill damage and seepage interference, the production rate under different parameters of perforation, compaction zone, damaged zone is discussed to yield the highest productivity. The numerical results show that it exists an optimal hole density in specific formation and when the perforated hole penetrates the invasion zone, increasing the depth of the perforation hole by the same amount would not result in a significant increase in gas production. The invasion and compaction zone permeability have little effect on the cumulative gas production, but an inflexion point still existed. Further, according to the principle of orthogonal experimental design, forty-one groups of orthogonal experimental calculations are designed and conducted. By analyzing the experimental results, the perforation density, hole diameter, invasion thickness, compaction zone thickness, invasion permeability, compaction zone permeability and stress sensitivity on productivity of perforated well is in descending order. The work presented in this paper can offer a technological basis and theoretical foundation for optimizing perforation parameters in specific tight gas reservoirs.

Evaluation of the porosity parameter for a perforated wall wind tunnel using measured wall pressure distributions

The existing analytical methods for determining and correcting the effect of wind tunnel walls on experimental data are based on the hypothesis of potential flow. A useful simplification of the boundary conditions used to describe the perforated walls was to consider the wall as homogeneous, the solid and free portions not being treated separately, but as an equivalent permeable surface. The approximation of the wall behaviour during the experiment was possible by defining a porosity parameter. The purpose of this paper is to estimate the porosity parameter for the perforated walls of a trisonic wind tunnel by evaluating the pressure distributions measured on the walls of the test section.

Quest CCS facility: Halite damage and injectivity remediation in CO2 injection wells

The Quest CCS facility (located in Alberta, Canada) is a fully integrated carbon capture, transport and storage facility operated by Shell Canada. It continuously captures and stores about 1.1Mt of CO2 per year. While the initial injectivity for the Quest CO2 injection wells was very high, significant injectivity reductions have been observed. As dry CO2 is injected, water can evaporate from the brine into the CO2 driving precipitation of halite. Plugging of the perforation tunnel and pore throats in the near wellbore area can cause injectivity damage.One method to remediate halite damage is to inject a water-based fluid to dissolve the halite precipitate. Quest performed the first halite remediation treatment on one of the CO2 injector wells in 2020. The objective of this paper is to present the design, execution and results of this initial halite remediation treatment. An outline of the design of the halite remediation treatment will be provided. Subsequently the halite remediation treatment as executed in the field will be reviewed including the timing of operations and the pumping pressure and rate data. Finally, to evaluate the effectiveness of the treatment, skin analysis and injectivity trends pre and post remediation treatment shall be presented.

Numerical Investigation on Interference of Multiple Hydraulic Fractures in Layered Formation

Staged treatment in vertical wells is extensively applied in layered formation to obtain commercial exploitation of hydrocarbon resources. Large-sized heterogeneities always exist between multiple hydraulic fractures in different layers. To reveal the interference of multiple hydraulic fractures in layered formation, a series of numerical investigations were conducted based on the cohesive zone finite element method. The results show that the sole stress interference is too small to exert an effective impact on adjacent pay zones, which is quite different from those in horizontal wells. The flow distribution in one pay zone can reach 56.2%, which is more than five times the magnitude of the least 10.5% during the fracturing in three pay zones. The fracture size heterogeneities are mainly caused by the interference of the fluid flow into multiple perforation tunnels in different pay zones. To further clarify how the flow distribution in the pay zones is affected, five related factors, including perforating thickness, pay zone thickness, rock permeability, minimum horizontal stress of the pay zone, and rock strength, are analyzed. The results show that it is through the manner of flow distribution adjustment in each pay zone that the five factors affect the fracture size. This study is of critical importance to clarify how the multiple hydraulic fractures from vertical wells interfere in layered formation and explain why the hydraulic fractures we get in the field are far away from what we want ideally.

Quantitative experimental study on the rule of fluid flow and its influencing factors in hydraulic fractures

Hydraulic fracturing has become a necessary tool for developing unconventional oil and gas resources. The goal is to create fractures in the subsurface and transport proppant from the surface into the subsurface fractures, which is accomplished by pumping a high-pressure fluid to open formation and using the energy of fluid to extend the fractures. Then, the fluid carries the proppant into the fracture and fills it. Therefore, the fluid plays a crucial role in the fracturing process, and the rule of fluid flow in the fracture affects the effectiveness of hydraulic fracturing. Based on this, this paper establishes a quantitative experimental device to simulate the process of fluid being injected into a fracture. The device achieves the first acquisition of the information of the flow field in the fracture by introducing the technology of particle image velocimetry (PIV). Our study found that the fluid flows through the perforation tunnel will occur obvious jet phenomenon thus causing the formation of a large number of vortices in the flow field near the entrance of fracture, and the turbulence of the flow field is high and the fluid flow is complex. As the fluid flows toward the distal end of the primary fracture, the vortices in the flow field disappear, and the flow field gradually becomes stable and the fluid flow is regular. And according to the characteristics of the distribution of the vorticity of the fluid in the primary fracture, we divide the flow field into three main characteristic areas, namely, the jet vortex zone, the turbulent transition zone and the stable development zone. When the fluid flows to the secondary fracture, vortices are formed and there is a obvious area of disturbance which affects the flow of fluid. In addition, we analyzed the effects of pump rate, viscosity, and perforation location on each area in the fracture and obtained the main control factors for each zone. This study provides the first systematic analysis of the law of flow in the fracture from the perspective of flow field, which profoundly reveals the rule of fluid flow in the process of hydraulic fracturing. This study provides theoretical guidance for the design and optimization of fracturing schemes, and provides reference significance for the microscopic study of flow in the fracture.

Effect of proppant pumping schedule on the proppant placement for supercritical CO2 fracturing

Supercritical CO2 fracturing is a potential waterless fracturing technique which shows great merits in eliminating reservoir damage, improving shale gas recovery and storing CO2 underground. Deep insight into the proppant-transport behavior of CO2 is required to better apply this technique in the engineering field. In the present paper, we adopted a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach to simulate the proppant transport in a fracking fracture with multiple perforation tunnels. Previous experiments were first simulated to benchmark the CFD-EDM approach, and then various pumping schedules and injection parameters (injection location, multi-concentration injection order, multi-density injection order and injection temperature) were investigated to determine the placement characteristics of proppant. Results indicate that the swirling vortex below the injection tunnels dominates the proppant diffusion in the fracture. The velocity of fluid flow across the proppant bank surface in multi-concentration injection shows a positive correlation with the proppant concentration. Injecting high-density proppant first can promote the transportation of low-density proppant injected later in the fracture to a certain extent. Decreasing the initial injection temperature of supercritical CO2 slurry helps enhance the particle-driving effect of fluid and improve the performance of supercritical CO2 in carrying proppant.

The impact of variable density in-plane perforations on fracture propagation and complexity control in the horizontal well

To understand the fracture behavior for variable density in-plane perforations on a horizontal well, true triaxial hydraulic fracturing experiments were performed with acoustic emission monitoring. The experimental results indicate that the variable density in-plane perforations can not only create transverse fractures but also arrest fracture propagation toward undesirable zones. The in situ stress and treatment parameters play significant roles in the fracture morphology and breakdown pressure. Under a large horizontal principal stress difference, there is a high possibility for simple transverse fracture creation, which results in a lower breakdown pressure. Moreover, the decrease in fracturing fluid viscosity can increase the fracture complexity and increase in pump rate can increase breakdown pressure and induce the complex fracture geomtetry. The acoustic emission (AE) characteristics and cutting fracture morphology demonstrate that not all perforations can be successfully initiated during the fracturing process. Because of the stress interaction from side perforations, fracture initiation and propagation from the middle perforation are strongly suppressed. Although the middle fracture is not fully initiated and propagated, it is still beneficial for the side hydraulic fracture connection and propagation in one plane. Secondary and axial fractures can still be observed, primarily due to the stress interaction between neighboring perforations and misalignment of the perforation tunnel orientation with the principal stress direction. In addition, the creation of complex fractures tends to occur using a high pump rate, which relates to tense fluid distribution competition from each perforation tunnel. Fracture initiation may follow an order but mostly tends to initiate from side perforations. Because of the stress interaction, hydraulic fractures from the side perforation can sometimes deviate from the perforation tunnel direction, twist and kink, and finally, generate nonplanar fractures. A large horizontal principal stress difference is recommended and beneficial for simple, straight and planar fracture creation during hydraulic fracturing stimulation with variable density in-plane completion for the horizontal well.

Numerical simulations of sand production in oil wells using the CFD-DEM-IBM approach

Three-dimensional CFD-DEM-IBM simulations of sand production in a sandstone formation, using periodic boundaries, were performed using 10000 frictional elastic spheres bonded together and compressed at 1 MPa of overburden pressure. Sand production simulation geometry and procedures are proposed, in which the cone penetration test (CPT) has been used to investigate the physical perforation penetration of the cemented sandstone material with the real-world grain size distribution from the Ustyurt-Buzachi Sedimentary Basin. The Immersed Boundary Method (IBM) was adapted for the sand production simulation geometry to simulate the fluid flow near the well casing. Oil with low viscosity and density was used as an injection fluid (reservoir fluid). This study shows what happens in the first 0.1 s immediately after perforating of the cased horizontal oil well. Erosion near the perforation tunnel was triggered due to the pressure drawdown, where the production of sand particles was initiated during the first flow due to the drag force that lifted the sand particles from the perforation damage zone. At the beginning of the simulation a sand arch was captured around the perforation tunnel and due to the fluid flow it collapsed and the perforation cavity became larger. The amount and mass of produced sand particles were calculated. The research findings provide insight into the sanding process and could be helpful for practicing engineers to understand the sanding mechanism at micro and macro scales. The results show that the proposed model is promising, and the innovative CFD-DEM-IBM-based system should be further elaborated to simulate the sand production in a sandstone formation.

Prefabricated UHPC-concrete-ECC underground utility tunnel reinforced by perforated steel plate: Experimental and numerical investigations

In this study, perforated steel plate-reinforced utility tunnel with the use of ultra-high-performance concrete (UHPC) and engineered cementitious composite (ECC) was proposed. The mechanical performance of the composite utility tunnel was experimentally investigated, and the cracking behavior and failure process were analyzed based on the digital image correlation (DIC) technique. It was found that the crack-control (durability) performance of the composite utility tunnel was superior to that of concrete utility tunnel with the same reinforcement ratio, and the composite utility tunnel can be used in severe corrosive environment. Additionally, the composite action between perforated steel plate and ECC was evaluated based on direct tension test and DIC analysis. Finite element (FE) analysis was conducted on the perforated steel plate-reinforced ECC and composite utility tunnel for a comprehensive understanding of the mechanical behaviors. The findings of this study provided useful knowledge for the design and application of the proposed composite utility tunnel for underground construction.

Production Performance of Perforation Clusters during Multistage Fracturing in Shale Gas Reservoirs

Gas production from each perforation cluster has an obvious difference along with the horizontal wellbore in shale gas reservoirs. Some special perforation clusters evenly do not produce any gas, which means that those perforation clusters are not fractured. In shale gas reservoirs, only when the shale gas section was fractured with equal volumes of fracturing fluids, gas can be produced evenly. In this study, a stress theory around the perforation tunnel considering the stress around the wellbore and an induced stress by leaking of the fluid and the tunnel is presented. The results show that (1) fractures will quickly be created at two of the three perforation clusters and then the fracture of the cluster initiates. (2) The rate through each cluster is different, and the fracture volume created will have a big difference. (3) The fracture distribution between three perforation clusters are different, thus shale gas production also will be different. The theory and the method presented in this paper, can be used for different reservoirs besides shale gas reservoirs, thus it can be applied and referred widely.

Research of Near-Wellbore Fracture Morphology, Formation Mechanism, and Propagation Law for Different Perforation Modes During the Perforation Process

Perforation plays an important role in the fracture morphology near the wellbore and the propagation of hydraulic fracturing fractures. Therefore, it is of great significance to find out the fracture morphology and propagation law during perforation for optimizing perforation technology, enhancing fracture control, and realizing complementary advantages of different perforation schemes. Based on analyzing the characteristics of perforation fracturing at each stage and existing perforation technology, two types of deep-penetrating perforating bullets were used to carry out large-scale perforation shooting experiments. The real processes of spiral perforation, directional perforation, conventional fixed-plane perforation, and interlaced fixed-plane perforation were simulated, respectively. The near-wellbore fracture morphology, formation mechanism, and propagation rule during perforation with different perforation modes were analyzed. The results show that (1) perforation is accompanied by the formation of tunnels, and there are three kinds of source microfractures developed around the tunnels, namely Type I radial microfractures, Type II oblique microfractures, and Type III perforation tip divergent microfractures. The three microfractures are interconnected to form more complex near-wellbore fractures. (2) Under different perforation modes and parameters, the near-wellbore fracture morphology and propagation law formed by microfractures around tunnels are also different. (3) The existence and expansion of near-wellbore fractures validate Chen et al.’s (2005) conjecture that there are “pre-existing fractures” in perforation and negate the assumption that the perforation tunnels are complete. There are no near-wellbore fractures when the perforation method is optimized. The research results in this paper can provide guidance and reference for improving the perforation fracturing effect in oil and gas reservoirs.

Experimental near-wellbore hydraulic fracture initiation and growth for horizontal wells with in-plane perforations

To understand the fracture behavior during different perforation modes on horizontal wells, laboratory-scale hydraulic fracturing experiments with acoustic emission monitoring were conducted on tight concrete samples. The experimental results indicated that the breakdown pressure could be greatly reduced and that a simple fan-like structure was created with in-plane perforations on a horizontal well under the same fracturing treatment conditions. Furthermore, there was a positive relationship between treatment parameters and breakdown pressure for helical perforations. Because of the small pressurization rate and large stress interaction, the breakdown pressure with in-plane perforations is smaller than that of helical perforations. However, the treatment parameters were not sensitive to the breakdown pressure but correlated with the shut-in pressure for the in-plane perforation mode. In general, increasing the pump rate and fracturing fluid viscosity can slightly increase the breakdown pressure and substantially increase the shut-in pressure. The increase in fracture extension pressure in the in-plane perforation mode refers to different fracture initiation orders of individual perforations. Although the deviation and failure of fracture initiation of some perforations can be observed due to the strong stress interaction of in-plane perforations, the existence of perforation tunnels can guide hydraulic fracture propagation within one plane. Thus, hydraulic fractures can connect and create large-scale fractures because of the close perforation spacing. The results of trace length and microscale fracture demonstrate that twisted and curved fractures with smaller widths can be significantly created by the helical perforation mode, but large-scale fractures can be created by the in-plane perforation mode, which is beneficial to sand plugging mitigation.

Comparison of Crushed-Zone Skin Factor for Cased and Perforated Wells Calculated with and without including a Tip-Crushed Zone Effect

A number of different factors can affect flow performance in perforated completions, such as perforation density, perforation damage, and tunnel geometry. In perforation damage, any compaction at the perforation tunnels will lead to reduced permeability, more significant pressure drop, and lower productivity of the reservoir. The reduced permeability of the crushed zone around the perforation can be formulated as a crushed-zone skin factor. For reservoir flow, earlier research studies show how crushed (compacted) zones cause heightened resistance in radially converging vertical and horizontal flow entering perforations. However, the effects related to crushed zones on the total skin factor are still a moot point, especially for horizontal flows in perforations. Therefore, the present study will look into the varied effects occurring in the crushed zone in relation to the vertical and horizontal flows. The experimental test was carried out using a geotechnical radial flow set-up to measure the differential pressure in the perforation tunnel with a crushed zone. Computational fluid dynamics (CFD) software was used for simulating pressure gradient in a cylindrical perforation tunnel. The single-phase water was radially injected into the core sample with the same flow boundary conditions in the experimental and numerical procedures. In this work, two crushed zone configuration scenarios were applied in conjunction with different perforation parameters, perforation length, crushed zone radius, and crushed zone permeability. In the initial scenario, the crushed zone is assumed to be located at the perforation tunnel’s side only, while in the second scenario, the crushed zone is assumed to be located at a side and the tip of perforation (a tip-crushed zone). The simulated results indicate a good comparison with regard to the two scenarios’ pressure gradients. Furthermore, the simulations’ comparison reveals another pressure drop caused by the tip crushed zone related to the horizontal or plane flow in the perforations. The differences between the two simulations’ results show that currently available models for estimating the skin factor for vertical perforated completions need to be improved based on which of the two cases is closer to reality. This study has presented a better understanding of crushed zone characteristics by employing a different approach to the composition and shape of the crushed zone and permeability reduction levels for the crushed zone in the axial direction of the perforation.

Technology Focus: Acidizing (June 2021)

Hydraulic fracturing technologies propagated from North America outward to other oil- and gas-producing regions in the world. In earlier days, the main technology developments were mostly related to the materials, such as fluids and proppants, and their characterizations. In recent years, more advancements have been made in tools, engineering processes, and analyses. In a cased-hole fracturing treatment, perforating plays a critical role to the success of the job, though it is often overlooked because perforations are visualized as holes with empty tunnel behind the pipe. Any damage is irrelevant because fracturing will simply bypass the damage. In fact, a shaped charge is made of metal liner and case with explosive loaded in between. The metal material is pushed into the formation under extremely high pressure from the detonation of the explosive. Without backflow of reservoir fluid to flush out the debris, the perforation tunnels are very likely plugged. In tight formations, the backflow is not efficient because the permeability is too low and the time scale of the surge is very short. Obtaining information about perforation before pumping the fracture treatment allows the engineers to adjust the job design, adding perforations or other means to deliver a more-desirable outcome for the fracturing treatment. Not all the wells or zones are suitable for hydraulic fracturing. Concerns over the well completion rating, nearby water layers, equipment and water availability, and other environmental and infrastructure constraints can limit the selection of stimulation method. Matrix chemical injection has often been the preferred or sometimes the only option. More-advanced technologies, however, are needed to extend reservoir access beyond the distance of matrix stimulation. Mechanical tunneling tools have been developed in recent years. They can bridge the gap between matrix and fracturing treatment very well. When combined with chemicals, this process can add efficiency in certain carbonate reservoirs. Hydrochloric acid continues to be the most effective and low-cost material for carbonate stimulation. Though exotic chemistries such as chelating agents and organic acids have been promoted for being less corrosive at high temperatures, the cost and dissolving capacity limit their use to large-scale implementation. The ability to inhibit the corrosion tendency of hydrochloric acid can prove to be beneficial in the economics of acidizing. New technologies in corrosion prevention, both in acid stimulation and production processes, should always be beneficial. During the tough year of 2020, and for the foreseeable future, implementation of engineering ingenuity will become more critical to maintain economical energy delivery in our industry. Recommended additional reading at OnePetro: www.onepetro.org. SPE 202369 Novel High-Effective Component for Acidizing Corrosion Inhibitors: Indolizine Derivatives of the Quaternary Quinolinium Salts by Zhen Yang, China University of Petroleum, et al. SPE 203086 First Successful Fishbone Stimulation Completion in Onshore Oil Field in the United Arab Emirates by Fernando Quintero, ADNOC, et al.