High-Speed Pressure and Accelerometer Measurements Characterize Dynamic Behavior During Perforating Events in Deepwater Gulf of Mexico

Abstract

With the current oilfield trend to pursue prolific oil and gas producers in the deepwater markets around the world; operators are drilling and completing larger boreholes to deliver and accelerate the production stream more effectively. Typically, in deepwater environments, the intervals to be perforated tend to be longer than on shelf-type completions. In addition, deepwater completions are more complicated with stacked pay zones that require additional completion steps and associated hardware. To execute these larger completions, operators normally opt to choose the largest perforating assembly that will yield the best charge performance (casing- entrance hole diameter and formation penetration) at in-situ conditions. These larger perforating systems with higher shot densities and total explosive load have the potential to create very large fluid-pressure waves and solid shock loads that can cause damage to the completion (unset packers, move bridge plugs, buckle tubing, split casing, etc.) under certain conditions. Because of the added expense of completing wells in the deepwater arena, problems during the perforation process can considerably increase completion expenditure. To help minimize potential risk during the completion program, it is critical to understand the dynamic pressure and shock events that occur during perforating. This paper will present a new numerical model that helps to ensure service quality by improving reliability on deepwater completions. The model has been validated with field measurements and employs high-speed recorders that were previously dedicated primarily to validating burn parameters for propellant-type equipment. Introduction The design of perforating assemblies up to this point in time has been based on simple rules of thumb such as: a 5 to 1 ratio of rathole volume to gun volume, standardized lengths of tubing (90 ft) between gun assembly and packer setting depth, or a minimum distance from the end of gun assembly to the well plug-back depth. Some have made arguments for stiff- versus-limber perforating assemblies and the implementation of shock absorption devices. The perforation process is normally a very safe step in the completion process when these simple rules of thumb are maintained. However, from time to time, an unexpected event such as bent tubing, collapsed spacer gun, failed packer/bridge plug, collapsed casing, etc. will occur during the perforation event even though the rules of thumb are followed. Standard root-cause analysis is to review the procedures that were executed and analyze the metallurgical properties of the failed components to ensure that no flaws due to corrosion or fatigue were present. Typically, the job parameters are compared against other jobs with similar job specifics to show how many similar jobs have been performed without incident. At the end of the post-job analysis process, if no specific cause is found, the standard response has been that this type of perforating job has been executed a given number of times with a given success rate as reported in a database. All equipment typically is observed to be in acceptable working condition (tensile, burst/collapse ratings, etc.), and the job is classified as a random event with an unknown root cause. The authors suspected that most of these supposedly random events actually were due to root causes that were beyond the capability of the technology available at the time to detect and analyze. In order to understand the responsible phenomena for these incidents more clearly, a research project was launched to quantify the dynamic perforating events with special high-speed downhole memory recorders that sample pressure, temperature and acceleration. The high-speed recorder measurements on actual field perforating jobs were then used to characterize and validate a physics-based numerical model. The concept of applying physics-based numerical models to explain dynamic behavior during perforating events has been applied previously1 and has been used specifically to characterize combined perforating/ propellant burn events.

Enabling Agile and Responsive Workflow Automation: A Hydraulic Fracture Design Case Study

“…These factors cause wellbore cleanout and displacement tasks to be extensive and time consuming. Complex multi-zone perforating (Sanders et al 2011;Burman et al 2011;Schatz et al 2004) and single-trip, multi-zone stimulation methods (Burger et al 2010) are required to stimulate these thick reservoirs. High-potential drawdowns (greater than 6,000 psi) will cause reduced proppant permeability and potential proppant fines.…”

Risk Evaluation Technique for Tubing-Conveyed Perforating

“…This simulation technique is robust and delivers accurate solutions. Gunshock simulation is described in papers by Schatz et al (2004), Zazovsky et al (2007), Baumann et al (2010a, 2010b, 2011a, 2011b, 2012), Canal et al (2010, Sanders et al (2011), andBurman et al (2011).…”

Reduction of Perforating Gunshock Loads

“…Perforation-induced pressure waves can lead to very clean perforations with low skin; but if the magnitude of the pressure waves is not properly controlled, dynamic pressure waves can produce equipment damage and other undesirable side effects, such as sanding. Other papers describing gunshock simulation include Schatz et al (2004), Zazovsky et al (2007), Baumann et al (2010aBaumann et al ( , 2010b, Canal et al (2010), and Sanders et al (2011).…”