TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWhen designing fracture treatments for high permeability formations, fracture conductivity is a primary factor in attaining maximization of completion economics. Optimum fracture design would dictate the knowledge of fracture orientation and the utilization of oriented perforation to optimally place the fracture. While in many unconsolidated formations, the contrast between horizontal stress is small or even insignificant; taking advantage of this situation often improves the efficiency and placement of a fracture.It is generally believed that existing spiral patterns used in more conventional slurry pack completions give better radial flow performance because of the uniform perforation distribution around the wellbore. However, when a hydraulic fracture is created, the majority of flow into the wellbore is delivered through the perforations that are communicated to the fracture. This is especially true when many of the unconsolidated formations suffer a high degree of damage around the wellbore. For this reason, it is important to focus fluids injected during the completion directly to the fracture and increase the number of perforations communicating with the fracture. This paper will discuss the justification and theoretical background for a newly proposed design that develops this concept. The paper also discusses the tools and procedures necessary to achieve the stated goals.A case history will be presented that will discuss the methods employed by an operating company in offshore Louisiana in perforating unconsolidated formations with the new system to obtain highly conductive gravel-pack fractures in deviated vertical wells. Significant to the success of the completions was the use of a high shot density perforating gun, oriented at 180-degree phasing. To facilitate the new approach, an innovative perforating gun system was also developed, and a wide perforation was designed to minimize friction.

Traditionally, underbalance perforating has been the preferred perforation technique. Recently, however, a new extreme overbalance perforating (EOBP) that has the potential to improve the completion efficiency of a well without additional stimulation has been introduced. With this method a well with a fluid column is pressurized with nitrogen to above fracturing pressure of the formation before the gun is fired. Gas is then injected, with or without acidor proppants, to create short fractures that extend from the perforation tunnels. The presence of gas lowers the amount of liquid that contacts with the formation, facilitates the well's coming into production after perforation, and results in less formation damage. This new EOBP method creates highly conductive short fractures, the benefits of which outweigh any restriction that may be caused by perforating debris. The debris that exits the gun when it detonates will be pushed away from the wellbore during the pumping stage, and this will greatly diminish any adverse effects on productivity that overbalanced perforating could cause. This can be considered as a near-wellbore stimulation method that also improves the completion efficiency of a well by allowing perforating and stimulation to be accomplished in one operation. By performing two or more completion procedures during a single trip into the wellbore, service operators have been able to generate economical advantages. There are numerous ways in which EOBP may be performed. This paper will cover the design, planning techniques, and equipment that can be used to perform tubing-conveyed overbalance perforating. Examples and field cases will show scenarios in which wells with a variety of wellbore conditions such as open perforations and packerless and tubingless installations can be perforated in an extremely overbalanced condition. An analysis technique that can be applied to a short falloff test immediately following the perforation treatment as well as the standard well testing is also described in this paper. The method of analysis can be used to calculate skin damage, formation permeability, reservoir pressure, and if applicable, fracture parameters such as fracture half-length and conductivity. Several field cases are included to illustrate application of this method.