Abstract
The application of horizontal completions in lower-permeability formations is continuing to proliferate on a global scale. Caused either by formation damage issues or the very heterogeneous nature of many such reservoirs, actual wells will underperform when compared to original predictions from reservoir simulations. This will continue to result in a need for effective hydraulic-fracturing stimulations for many of these wells to reach economic production levels. Horizontal completions in moderate- to low-permeability reservoirs present the challenge of cost constraints that seldom allow the use of long-proven methods such as cemented completions and individual-fracturing of numerous zones with bridge plug isolation and multiple perforating runs. Some new methods being applied to overcome this problem require expensive downhole "jewelry" and some added risks that the liner and jewelry can be entirely run to the predetermined depth. In some methods, the operator must also accept reduced completion IDs that can later restrict production rates or hinder workover operations. These increased costs and risks must be accepted even before the actual fracturing treatments are attempted.
This paper will discuss a new approach to controlled placement of multiple-stage fracturing treatments without the risks involved with packers or bridge plugs. By implementing a coiled tubing (CT) deployed hydrajet-perforating method, immediately followed by a fracturing treatment pumped down the annulus, the operator can use lower cost (and lower risk) liner completions, and delay the decision of selecting exactly where the perforated sections should be placed. In many cases, the final decisions on placement of the next perforated location can even be delayed until after the wellbore displacement of the preceding fracturing stage. By pumping the fracturing fluid slurry down the annulus of the CT and the casing the allowable frac rates can be higher than with tubing-deployed techniques. The total stimulation related costs are greatly reduced by being able to perforate/frac multiple times within the same day. Even where more than one day is required to complete the stimulation of all desired locations along the lateral, only one CT intervention and one pumping service company mobilization and rig-up will be needed, which will still improve the job economy over conventional methods. An additional benefit includes a reduction in the potential for excessive multiple fractures or near-wellbore tortuosity encountered with explosive charge perforating.
