Do We Really Perforate Per the Design? Key Elements of Safer and High-Productivity Well Perforating

Abstract

Numerous perforation jobs are performed daily around the globe on a routine basis to establish wellbore to reservoir communication. However, in some cases, these perforating operations can result in poor well productivity or severe health, safety, security, and environment (HSSE) incidents. In this paper, the key elements of proper perforating operations, from data gathering to design and safest possible execution, are summarized to create practical guidelines for operators. Oil and gas wells are drilled, cased, cemented, and perforated as a result of diligently planned multidisciplinary engineering work. The engineers have traditionally designed perforations to have cleaner, larger, and deeper tunnels into reservoir rock to enhance the communication quality between the wellbore and reservoir. Research has proved that wellbore dynamics have significant control on the success of perforating activities during this fast-paced and short-lived event. Therefore, recently the trend has evolved from static underbalanced perforating to dynamic underbalanced perforating via advanced downhole gun system designs and downhole tools. Conventionally, operators have focused on debris and damaged rock removal from the perforation tunnels by applying static underbalanced perforating. However, static underbalance alone does not guarantee the optimal perforation tunnel structure. Research has shown that dynamic underbalance can significantly enhance tunnel cleanup and well productivity. Today, numerical perforating dynamics software is available to simulate wellbore dynamics for a given perforating design with various downhole tools. Perforating gun detonation pressures and the resulting shock waves can damage downhole tools and hinder wellbore integrity if not mitigated properly. In Oman, carefully designed and executed perforating operations have improved well productivity and operational safety for many years. Each perforating job is assiduously planned and executed. Specially designed software packages are used to simulate the wellbore conditions and downhole equipment response to identify and mitigate potential problems and to improve the efficiency of perforating tunnels cleanup prior to each perforating job. The application of this methodology has resulted in performing numerous highly successful perforating jobs in Oman. The results of these perforating jobs are presented here as case studies. The static and dynamic wellbore conditions as simulated and observed during the operations with a fast downhole gauge are compared and discussed in detail. Lessons learned and guidelines are presented in an easy-to-follow way to help operators achieve successful results. The methodologies and best practices outlined in this paper enable improved perforation designs by using available software in challenging environments where conventional approaches can be inadequate. The methodology is described systematically in detail so that the procedure and learnings from Oman's hydrocarbon producing wells and reservoirs can be adapted to other operations around the globe.