The combined use of propellants and perforating for production enhancement is not new to the petroleum industry, especially for natural completions in competent formations. When used together, the propellant is shaped in the form of a cylindrical sleeve that is positioned over a typical scalloped perforating carrier to combine the perforating and stimulation processes into one step. The perforating event is performed in either an under-balanced or balanced condition, followed immediately with the extreme over-balance or rapid-gas pulse generated from the propellant burn. This technique provides an effective method to ensure that all perforations are sufficiently broken down with the fracturing to accept either produced or injected fluids.
This paper will review a new application for the combined propellant / perforating technique that has been successfully used in unconsolidated formations in the Gulf of Mexico. The propellant / perforating technique was used to enhance the placement of proppant during frac-and-pack treatments while perforating in a balanced condition. The propellant / perforating technique was used on several formation types; i.e., long intervals, highly deviated, and highly laminated with extreme permeability contrasts, that would traditionally be deemed as high risk for proper sand placement. The propellant sleeves are positioned across the lower quality portions of the intervals with low permeability and resistivity to ensure that the perforations performed in these intervals are broken down to accept fracturing fluids and proppant during the fracturing treatment consistent with the entire treated interval.
Two case histories from a major gulf-of-Mexico operator will be presented and will discuss the steps that led this operator to use this propellant/perforating technique to overcome sand placement problems (screenouts).
In the case histories presented, it will be shown that that this technique is effective in both underbalanced and overbalanced perforating situations. With the trend in the industry to reduce cycle time, the elimination of the underbalance/surge process to ensure clean perforations and all the associated rig time in obtaining control of the well following the surge are seen as opportunities for rig-time savings. It has now been proven that combining propellant/perforating in a balanced scenario can also offer cost efficiency and safety when used as a near wellbore clean up tool for pre-frac preparation.
Propellants have been available to the industry for many years and have been used in a variety of applications, primarily in the United States, Canada, China, and Russia. Review of the literature1–11 reveals the variety of applications in the industry where propellants have been used along with the degrees of success attained in these applications. The concept of using the propellants in combination with the initial tubing-conveyed perforating (TCP) to enhance the placement of proppant during a frac-and-pack completion, however, is a new application for the oilfield.