A Unique Approach To Enhancing Production From Depleted, Highly Laminated Sand Reservoirs, Utilizing A Combined Propellant/Perforating Technique

The primary objective in the design of a perforating program is to remove or minimize any impedance to the desired fluid movement from the reservoir to the cased wellbore. The possible damage that could occur from drilling-fluid contacting the formation is one of the significant problems that must be addressed in selecting the perforation technique. As drilling fluid enters the formation, it can deposit solid matter, cause clay swelling, and induce chemical precipitation, creating a damaged zone area around the wellbore. All of these resulting phenomena reduce the size of the pores available for fluid flow. In addition to the induced drilling fluid damage, the radial displacement of formation materials during the perforating event causes crushing and compacting of the area that immediately surrounds the perforation (better known as the crushed zone area), which will subsequently result in a reduced permeability envelope around the perforating tunnels. Perforating the well in an underbalanced condition using super deep penetrating ‘premium’ charges has proven to be an effective technique in removing near wellbore damage, as it allows the formation pressure to remove the damaged rock instantly. However, if the formation pressure is too low to move the damaged rock, permeability at the face of the perforation can be greatly reduced. In many wells, the damage can be so severe that only 25 percent of the perforations will produce. This paper reviews the successful application of a combined propellant and perforating technique in depleted, highly laminated sand reservoirs. In the case histories discussed, applying this technique resulted in stimulated wellbore conditions that improved flow efficiency. The results from the pressure transient analysis are included and will verify the attained productivity improvements. The paper also discusses the initial operational problems encountered in implementation of the propellant/perforating technique and the precautionary methods that were taken to address these scenarios.