This paper describes the operational planning and process safety due diligence performed to ensure safe and successful operations in the world's first deepwater propellant perforation in a carbonate reservoir. The Malampaya gas field in the Philippines is a depleted carbonate reservoir with five subsea development wells. The Malampaya Phase 2 Project that concluded in Q2 2013 involved drilling two new infill wells MA-11 and MA-12. Given the uncertainty in prognosis (Carbonate K-Phi) and the greater risk of not securing wells with high deliverability as per the well objectives, it was decided to use some form of near wellbore stimulation to bypass the near well bore damage zone caused by cement losses and cuttings lost to the formation while drilling the 300 m reservoir section. Propellant perforation technology solution was selected based on optimization of rig time, ineffectiveness of acid jobs in a karstified, fractured carbonate and process safety considerations of acid handling on a dynamically positioned rig. 200 m reservoir section was perforated safely and successfully with 3–3/8″ propellant perforation gun with 30% propellant loading on a 2″ coiled tubing in each of these two subsea wells. A standard 6 SPF shot density and 60 degree phasing was adopted with deep penetrating charges to bypass the damage zone suspected from drilling and cementing losses in this depleted carbonate. Both the wells delivered finally in excess of 100 MMscf/day during the well test on the rig as expected. This paper outlines the expected vs. actual well performance; process safety due diligence with an elaborate modeling focus on the worst case scenario (i.e. no cement behind the 7″ liner). Static and dynamic coil modeling results are shared along with an overview of the transient modeling conducted to optimize the final perforation interval on both the wells based on the actual lithology information.
Prediction of perforating gunshock loads and the associated risk of tool damage is very important because of the high cost of nonproductive time associated with fishing jobs, particularly for deep-water wells. We have examined real examples of gunshock damage to determine how these incidents could have been prevented by using the most current (2014) capabilities in simulation software to predict gunshock loads. Our goal was to evaluate the latest software advances for predicting perforating wellbore dynamics and the associated gunshock loads and gauge the usefulness of the simulations in common perforating operations. Both low- and high-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems and/or under adverse conditions. Examples of tool damage due to gunshock include bent tubing and unset or otherwise damaged packers and wireline weak-point pull-offs. Using gunshock simulation software, we can identify perforating jobs with significant risk of gunshock damage, and then we can make changes to the perforating equipment or job execution parameters to reduce gunshock loads to safe levels, thus reducing the risk of equipment damage and nonproductive time. Using the latest gunshock software, engineers can also evaluate the sensitivity of gunshock loads to changes in perforating equipment, such as gun type, charge type, shot density, tubing size and length, cable size, rathole length, and placement/setting of packers and shock absorbers. We analyzed two examples of gunshock damage: a tubing-conveyed perforation (TCP) job with 7-in. guns that produced a bent firing head fill-sub and tubing joints and a deep-water wireline job that broke the cable weak point. For both cases, we first simulated and analyzed the jobs as run to understand the observed damage and then we developed solutions to reduce the gunshock loads to a safe level. Introduction The objective of well perforating is to connect the reservoir rock to the wellbore for hydrocarbons to be easily produced or for fluids to be easily injected. Perforating with hollow carrier guns begins with the detonation of shaped charges contained inside thick-walled tubes called gun carriers. Shaped charges create high-velocity jets (~ 25,000 ft/sec) that produce tunnels in the reservoir rock. Shaped charges are selected based on the target completion type, either to penetrate deeply into the reservoir or, sacrificing penetration, open up an enlarged area for flow. When the shaped charges detonate, the hollow carriers deform due to internal gas pressure and debris impacting the inner side of the carrier. At the same time, the perforating jets puncture the hollow carrier wall, and the detonation gas inside the gun interacts with the wellbore fluid. All of these events combined lead to the onset of wellbore hydrodynamics, which includes large-amplitude pressure waves that produce very large loads on the equipment. The origin of gunshock loads generated by wellbore pressure waves will be explained in the gunshock studies presented in the following sections.
Many large wells have been drilled in the Gulf of Mexico's Lower Tertiary play. These wells are completed with single-trip multizone systems, and they have gross perforated lengths exceeding 1,500 ft. The main difficulty in perforating these wells is the high-pressure environment (~20,000 psi). Under these conditions, the challenges are to create sufficiently large entrance holes in the casing, minimize the high-risk of equipment damage due to gunshock, and minimize the amount of perforating debris created. Perforating several intervals in a single run is required to complement single-trip multizone systems. Perforating all zones simultaneously in one trip saves time and reduces risks when compared with stacked completions requiring multiple trips for each zone. Safety and cost reduction are extremely important in deepwater operations. Risk control is very important because gunshock and/or debris problems can lead to multimillion dollar losses in non-productive time, and in extreme cases, gunshock problems can lead to lost wells. To undertake these challenges, a new Low Perforating Shock and Debris (LPSD) gun system was used. In comparison with standard high-pressure guns, the LPSD gun system produces much less gunshock and negligible amounts of debris; thus, minimizing gunshock risk and reducing cleanup runs typically needed to recover perforating debris. LPSD guns produce negligible amounts of debris because LPSD guns contain all the metallic components, including the shaped charge cases, which remain virtually intact inside of the guns. A key element in planning these perforating jobs is gunshock prediction to evaluate if the equipment will be able to withstand the transient loads produced by the perforating guns. The gunshock prediction process is described in detail in this paper. For a typical 4-zone 1,500 ft gross length perforating job, the time needed from picking up the first gun to laying out the last gun averages 84 hours. All zones are simultaneously perforated, which eliminates three perforating runs per well, saving approximately 9.2 days per well while minimizing personnel exposure. By perforating the largest high-pressure wells in the Gulf of Mexico's Lower-Tertiary play with LPSD guns, we minimized personnel exposure, minimized debris and reduced execution time up to 72%.
Explosive thermal stability is an important topic for oilfield perforating operations and impacts perforating system performance and safety. Explosives have time dependent temperature limits which can lead to thermal decomposition when exceeded and, under some circumstances, can result in performance losses and safety hazards. Explosive thermal stability information is currently provided by perforating system manufacturers through time versus temperature plots. While these plots have proved useful for many years, this review of current industry thermal stability data and practices aims to highlight a need for improvement and expanded testing representative of the energetic materials as used in actual well environments. More specifically, this review discusses the potential economic impact on well performance and operational safety when thermal stability limits are exceeded. When using currently available time versus temperature plots, operators sometimes must select lower performing explosives which are thermally stable at higher temperatures especially for high temperature well environments. As a result, operators risk optimal well inflow performance with significant economic impact. Furthermore, exceeding the time dependent temperature limits can lead to thermal decomposition. Off-gassing from thermal decomposition can trap pressure inside of gun carriers creating safety hazards during misruns. This review includes a reference to a known occurrence where overexposure to temperature led to thermal runaway and a surface explosion of a recovered perforating system. Additionally, this review discusses shortcomings in thermal stability test methods and related API recommended practices. Current methods assessing thermal stability, including vacuum thermal stability, ampule, and ODTX (One Dimensional Time to Explosion) tests tend to use unrealistic test conditions. The API recommended practices do not directly assess thermal decomposition which is important in developing safe practices for recovered perforating systems which may have been exposed to temperatures exceeding thermal stability limits. This review concludes with recommendations for future work to better understand thermal stability in oilfield explosives. More suitable thermal stability tests which evaluate oilfield explosives in well environment conditions will lead to improved safety recommendations and has the potential for significant economic impact on well productivity through enhanced understanding of the time dependent temperature limits. Finally, this paper draws on the urgent requirements of the Operator community, the experience of the manufacturing community and the advanced technical support of a US National Laboratory to provide a concise review and recommendations which can then be promulgated through the API, as a major step in enhancing safety and ultimately well performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.