New Insights in Zinc-Cased Charges Enable the Development of a True Low-Debris Shaped Charge
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Cited by 4 publications
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Understanding the Origin and Removal of Downhole Debris: Case Studies From the GOM
Potential damage to the formation and generation of destructive wellbore debris can occur during perforating operations with shaped charges. One type of damage is to the formation, which is related in part to the powdered metals and metal alloys incorporated into the metal casings that contain the explosive charges in controlled debris perforating systems. Upon discharge, gun debris, including casing-metal residue and reaction products from the perforating system, can also contribute significantly to the overall amount of destructive wellbore debris generated. In addition, the debris often includes metal fragments from the wellbore casing, formation sand and other minerals, cement, and drilling fluid remnants that eventually are ejected into the wellbore. All of these materials can promote costly mechanical failures, contribute to well control problems, and hamper onsite operations. Various factors influence the ultimate generation of destructive wellbore debris. These factors include gun type, fluid type, fluid density, bottom hole pressure and temperature, and the specific wellbore configuration and completion scenario employed. While previous authors have addressed formation damage issues or the impact resulting from the use of various casing metals, this work focused on the actual downhole debris generated and collected from the wellbore just after perforating the well, and relates these findings to the influencing factors. With the use of advanced downhole filtration and collecting techniques, downhole debris was collected from a series of deepwater projects in the GOM. Debris analysis coupled with well completion information has been studied. Results from the examination of downhole wellbore debris collected after perforating the well is presented and discussed. Improved wellbore integrity and reduced risk are obtained through proper management of perforation and wellbore cleaning practices. Introduction Universally accepted, downhole debris is responsible for numerous problems associated with well completions, evidenced by the disclosures presented in each paper on this topic cited herein.1–10 Downhole debris has been associated with formation damage issues, failure in mechanical shifting of downhole flow control systems, retrieving temporary packer plugs, interfering with the setting of landing tools, and other problems. Much of the destructive wellbore debris is directly associated with tools used to perforate and the perforation process itself. Other debris can occur from material accidentally introduced from the surface. Several papers address the relative merits of zinc-cased perforating charges, steel-cased perforating charges, and a newly developed low-debris steel-cased perforating charges.1–4 Case histories demonstrating the usefulness of both zinc-cased2 and the newly developed steel-cased3,4 perforating charges are available in their respective publications. The perceived problems and benefits associated with zinc-cased charges has been described in some detail.5 Part of the potential damage from zinc-cased charges was found to be associated with the potential formation of complex zinc-hydroxy-chloride cements similar to the magnesia cements known as Sorel cements. In addition to acid, some products were reported effective in certain brine systems, but limited solubility of the product, incomplete control of precipitation, and potential formation damage prevented further application without modifying the product chemically. A method of preventing perforation damage from zinc-cased charges in high temperature applications by use of a long-chain organic acid was reported; 6 corrosion data was provided only for 22-chrome material.
Understanding the Origin and Removal of Downhole Debris: Case Studies From the GOM
Potential damage to the formation and generation of destructive wellbore debris can occur during perforating operations with shaped charges. One type of damage is to the formation, which is related in part to the powdered metals and metal alloys incorporated into the metal casings that contain the explosive charges in controlled debris perforating systems. Upon discharge, gun debris, including casing-metal residue and reaction products from the perforating system, can also contribute significantly to the overall amount of destructive wellbore debris generated. In addition, the debris often includes metal fragments from the wellbore casing, formation sand and other minerals, cement, and drilling fluid remnants that eventually are ejected into the wellbore. All of these materials can promote costly mechanical failures, contribute to well control problems, and hamper onsite operations. Various factors influence the ultimate generation of destructive wellbore debris. These factors include gun type, fluid type, fluid density, bottom hole pressure and temperature, and the specific wellbore configuration and completion scenario employed. While previous authors have addressed formation damage issues or the impact resulting from the use of various casing metals, this work focused on the actual downhole debris generated and collected from the wellbore just after perforating the well, and relates these findings to the influencing factors. With the use of advanced downhole filtration and collecting techniques, downhole debris was collected from a series of deepwater projects in the GOM. Debris analysis coupled with well completion information has been studied. Results from the examination of downhole wellbore debris collected after perforating the well is presented and discussed. Improved wellbore integrity and reduced risk are obtained through proper management of perforation and wellbore cleaning practices. Introduction Universally accepted, downhole debris is responsible for numerous problems associated with well completions, evidenced by the disclosures presented in each paper on this topic cited herein.1–10 Downhole debris has been associated with formation damage issues, failure in mechanical shifting of downhole flow control systems, retrieving temporary packer plugs, interfering with the setting of landing tools, and other problems. Much of the destructive wellbore debris is directly associated with tools used to perforate and the perforation process itself. Other debris can occur from material accidentally introduced from the surface. Several papers address the relative merits of zinc-cased perforating charges, steel-cased perforating charges, and a newly developed low-debris steel-cased perforating charges.1–4 Case histories demonstrating the usefulness of both zinc-cased2 and the newly developed steel-cased3,4 perforating charges are available in their respective publications. The perceived problems and benefits associated with zinc-cased charges has been described in some detail.5 Part of the potential damage from zinc-cased charges was found to be associated with the potential formation of complex zinc-hydroxy-chloride cements similar to the magnesia cements known as Sorel cements. In addition to acid, some products were reported effective in certain brine systems, but limited solubility of the product, incomplete control of precipitation, and potential formation damage prevented further application without modifying the product chemically. A method of preventing perforation damage from zinc-cased charges in high temperature applications by use of a long-chain organic acid was reported; 6 corrosion data was provided only for 22-chrome material.
The ability to predict and reduce large perforating gunshock loads and the associated risk of damage and nonproductive time is very important because of the high cost of most wells, especially deepwater high-pressure wells. The aim of this paper is to present the most current (as of 2014) capabilities in simulation software to predict perforating gunshock loads produced by hollow carrier guns. This is a joint effort between operators and service companies to promote the discussion on dynamic gunshock modelling. The end goal of this paper is to communicate to a broader audience of oil and gas companies the most current knowledge on predicting perforating wellbore dynamics and the associated gunshock loads and to look ahead for future developments in dynamic gunshock modelling. Both low- and high-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems and/or under adverse conditions. As of 2014, there are several software tools available to predict gunshock loads. These software tools help engineers identify perforating jobs with significant risk of gunshock damaged, such as bent tubing and unset or otherwise damaged packers, gun damage, wireline weak-point pull-offs, etc. When the predicted risk of gunshock damage is large, engineers can make changes to the perforating equipment or job execution parameters to reduce gunshock loads and the associated risk of equipment damage and nonproductive time. With the available gunshock software, engineers can also evaluate the sensitivity of gunshock loads to changes in the perforating equipment, such as: gun type, charge type, shot density, tubing size and length, rathole length, and placement/setting of packers and shock absorbers. In this paper, we describe the main sources of gunshock loads. We present examples showing typical loads on tubing and packers, and we elaborate on the load levels that can lead to equipment damage. Simulation examples included in this paper also illustrate how to reduce gunshock loads by modifying the equipment used. We illustrate how small changes that cost very little to implement can lead to a large reduction in both gunshock loads and the associated job failure risk.
All perforating operations cause debris, which can lead to wellbore restrictions, choked downhole hardware, plugged perforations, formation damage and operational problems throughout the installation of the completion. As a result, the industry has taken significant efforts to develop low-debris perforating systems. Low debris perforating techniques are important in maintaining a clean and productive perforation tunnel, as well as helping to reduce the risk of operational issues associated with debris during subsequent downhole tool operations. This risk minimization becomes even more important in complex completions with long zones at high shot densities (as often seen in sand control completions), in stacked completions where perforating on top of packers is required, and in horizontal completions, where debris can't fall into a sump area.One of the common methods for reducing the effect of perforating debris has been the use of zinc cased perforating charges. However, any low-debris system must also still create the optimum perforation in terms both of tunnel dimensions (maximum depth and diameter) and tunnel clean-up (minimum debris / reduced perm zone). Further, to maintain the connectivity of the perforation, consideration must be given to how the debris is handled after the perforating event and to potential interactions among the perforating debris and the wellbore and reservoir fluids. Extensive lab studies have examined all the effects of zinc perforating charges in these areas, but it is also critical to properly apply this to field scale applications through procedural examination.This study seeks to examine effects of perforating debris on field mechanical operations comparing different types of perforating debris. A comparison versus conventional steel-cased charges is also presented in terms of charge performance and dynamic clean-up effects of low-debris zinc charges. Further, an examination of chemical interactions of these low-debris systems in the field will be presented, and most critically, a comparative evaluation of procedural decisions and methods will be presented to show an optimum application of lab learnings to field scale applications. This paper also presents several case histories of wells that have been successfully completed using low debris perforating gun systems with zinc cased charges. Critical aspects of minimizing and managing debris, well productivity and other operational successes will be presented as part of the case histories.
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