This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper IPTC 12581, "Effective Perforating and Gravel Placement: Key to Low-Skin, Sand-Free Production in Gravel Packs," by Samyak Jain, SPE, Raymond Tibbles, SPE, and Jock Munro, Schlumberger, and Rajeswary Suppiah and Norhisham Safin, SPE, Petronas Carigali, originally prepared for the 2008 International Petroleum Technology Conference, Kuala Lumpur, 3-5 December. The paper has not been peer reviewed.
Cased-hole gravel packing is used to control sand production from oil and gas wells. The success of a cased-hole gravel-pack job depends on the ability to pack perforation tunnels effectively. The full-length paper presents a systematic approach for perforation-damage removal, effective gravel placement, and packing of the perforation tunnels. Guidelines to surging the formation and executing the perforation-packing job are presented.
Every year the petroleum industry spends USD millions cleaning sand out of wells and repairing problems related to sand production, and it loses additional dollars by restricted production rates. Sand production is a common occurrence in highly unconsolidated formations.
In cased-hole applications, perforations act as a conduit for fluid flow between the formation and the wellbore. Production rates can be reduced severely if the packed perforations are damaged. The ability of the well to deliver its potential productivity depends on the inflow area these perforations provide for fluid flow. Perforations may be dam-aged for a number of reasons including perforation debris, a compacted or crushed zone consisting of pulverized sand grains, perforations filled with reservoir sand, and other drilling- and completion-related activities.
Perforation Surging. Perforating is the critical process connecting the reservoir with the wellbore. The selection of the gun system is driven by many factors including wellbore dimensions and formation and reservoir properties. One of the most critical parameters for perforation strategy is the rock strength, measured as unconfined compressive strength. It is recognized throughout the industry that for sand-control completions, both high shot density and big-hole charges are the optimum gun/charge configuration.
Increased area open to flow maximizes the productivity of the well while it reduces the fluid velocity per perforation, reducing the risk of sand production through the gravel pack and sand screens. High-velocity flow through isolated perforations can create "hot spots" that, with time, can erode through the screens, resulting in massive sand production and sometimes the loss of the zone or the well.
