Perforations are used to flow hydrocarbons into a well. Impeding that flow are damaged zones from drilling and the crushed zone lining the walls of perforation tunnels into the rock. In addition, charges can affect a region beyond the crushed zone. This region is termed the "fracture damage zone," and the nature of this region is examined in this paper. The fracture damage zone is the area where the concrete model shows altered effects. This region of damage is not necessarily failed, but is the most likely region of fracture. This work discusses the use of a shock hydrocode to delineate this region. Because the hydrocode is a continuous code, specific fracture paths are not predicted. The code is run for big hole (BH). deep penetration (DP), and fracture (Frac) shaped charges. The damaged region is compared for the types of shaped charges. Simulation results indicate that the region of fracture damage follows the bow shock. This semicircular bow shock region continues propagation after the jet has stopped, but eventually diminishes outward from the jet origin. Generally, the BH charge has a wider damage region than the DP charge, with the DP charge damage region being narrower and deeper than the BH (because of the depth of penetration). The damage zone of the Frac charge is between those of the BH and DP charges. In addition, the damaged region may not be sufficiently affected to actually create failure caused by fractures. "Distance" to the fracture limit is characterized. This ready-to-fracture region is discussed in terms of making it a failed fracture region by external influences, such as propellant stimulation.

The effective combination of propellants to generate a high-pressure pulse to create micro fractures has been proven to be successful in a number of wells in Ecuador.Recently, the inclusion of surge chambers in the bottom hole assembly has been proven to provide improved cleanup of the perforation tunnels created by jet perforators. This minimum surge pressure across the formation results in a dynamic underbalance that improves well productivity. Owing to the improved cleanup, there is a better path between the reservoir and the wellbore, which has demonstrated a more than 50% increase in well productivity. The ability to delay the opening of the chambers after gun detonation is critical in creating a dynamic surge from reservoir to wellbore, thus enhancing the dynamic flow and removal of fluids and solids from the perforation tunnels.This combination of overbalance and dynamic-underbalance immediately after perforating has also provided a method for cleaning perforation tunnels, even when perforating overbalanced with wireline-conveyed guns.This technique has been highly successful in the East Basin of Ecuador, especially now that near-wellbore stimulation techniques to clean the perforation tunnels can be achieved with wireline-conveyed guns instead of using a rig to provide tubing-conveyed perforating (TCP) services to create optimum conditions during perforating. This combination of techniques provides an effective solution at a reasonable cost that optimizes reservoir connectivity with the wellbore, significantly increasing the productivity index.However, for these techniques to be used successfully and create the necessary conditions to remove debris damage from the perforation tunnels, it is imperative that the software models and simulations be provided by experienced and well-trained engineers.Prior to the job, the service is modeled using state-of-the-art software simulators to predict the dynamic forces acting on the wellbore. When the job is executed, fast-gauge memory recorders are used to capture the pressure and temperature data at the time of the perforation event to validate the modeling. This technology has demonstrated great success in Ecuador by improving well productivity by as much as 50% when compared to other nearby wells in the field.

This paper discusses using a perforating toolkit as a computational paradigm to provide perforating solutions to field personnel. This toolkit provides an extensive list of charges and gun systems and generates the effects on the target rock and overburden pressure. Outputs include depth of penetration and casing hole sizes. It has an improved graphical user interface (GUI) and updated algorithms based on data from the flow laboratory. The perforating toolkit uses up-to-date API data as the basis for the calculations; simulations are based on parameters set by the user and outputs are in a graphical format, showing the perforating performance within the reservoir. The perforating toolkit software is designed to use improved data obtained from recent laboratory testing. The most up-to-date flow laboratory testing was used to generate the algorithms for the perforating toolkit, generating more precise algorithms and producing improved perforation predictions. Testing involved a broader range of data than was previously used, allowing the software to make more accurate predictions. This new tool was benchmarked using laboratory testing, which demonstrated the quality of the paradigm and its functional use for improved downhole perforating. The software provides the field user with a tool to predict downhole shaped-charge performance quickly and in a cost-effective manner. The models also allow a number of parameters to be varied for a better comparison of different scenarios. This paper discusses how new data across a broader range from the flow laboratory was used to improve the basic software algorithms and help provide the most accurate prediction of downhole charge performance.

The detonation of explosives in the wellbore produces hazardous gas; however, these gases are not typically observed in high concentrations at the surface. Recently, during plug and abandonment (P&A) operations, carbon monoxide (CO) from perforation activities was observed in high concentrations. This paper examines these types of operations to determine root causes and mitigation methods. The anticipated amount of CO produced by detonation is calculated by both the empirical equation and reaction-equilibrium simulation methods for cyclotetramethylene tetranitramine (HMX), as well as by the simulation method for cyclotrimethylene trinitramine (RDX), hexanitrostilbene (HNS), and 2,6-bis,bis-(pikrylamino)-3,5-dinitropyridine (PYX). The life cycle of this gas from the time of generation through its potential release to the surface is discussed with the intent to reduce its quantity or concentration throughout. Mitigation methods include the incorporation of an oxidizer in the explosive reaction, chemical scavenging in the wellbore, and controlled venting or catalytic conversion at the surface. Significant quantities of CO are produced by perforating guns, with the proportion increasing for explosives of greater thermal stability until it is the single largest reaction product. During perforation, these gases are usually controlled by gas-handling equipment on the platform; however, the reduced availability of this equipment on the platform at the time of P&A operations is thought to be a contributing factor to the hazard. Another significant factor could be the use of a high circulation rate, which has the effect of increasing the concentration of the gas on the surface. Controlled venting, flaring, and catalytic conversion to carbon dioxide are feasible methods to help mitigate this hazard if conducted in accordance with regulations. This paper details the life cycle of CO gas generated from perforating activities and discusses how it can be hazardous during P&A operations. In addition, several methods are discussed that can help mitigate this hazard.

Side-mounted gun strings present a unique challenge for predictive perforation modeling tools because of their asymmetric geometry. To fully capture the dynamic response of the side-mounted system and more accurately predict the response of any gun system in general, it is important to fully capture the three-dimensional (3D) effects of model geometry and detonation-induced loading. This work details the modeling approach developed for a side-mounted gun system that enables the full geometry to be simulated so that accurate predictions of stresses and displacements could be made; these predictions are necessary for evaluating the damage potential to sensitive tools in the string, It is important to allow operation designers to optimize gun spacing and provide string flexibility to help ensure it can withstand downhole conditions without affecting performance. The simulation methodology was calibrated against previous test measurements, where loads and accelerations were captured during surface testing of a gun string. A detailed model was developed for the planned operation, and simulations were performed to predict the dynamic response of the wellbore fluid and tool string. Multiple damage sensitivities were identified for particular tools, and model results were extracted to evaluate 1) pressure dynamic loading on the tool, 2) displacement levels where movement is expected, and 3) dynamic loading of the tool. These results were provided to the developers of the sensitive tool to help assess potential damage risks. For each case, predictions were compared to previous test results and operation experience to develop a risk evaluation for the planned operation. Further, results were used to make adjustments to the operation to help optimize performance; comparison plots are presented for the different configurations evaluated. This overall process provided confidence to the operators that the operation would be performed successfully with no damage to the sensitive tool.