Several recently introduced oilfield perforators incorporate reactive materials that are derivatives of military-based weapons technology. Claims have been made that reactive shaped charges provide improved downhole performance and well productivity over conventional shaped charges by creating optimized perforation tunnels. To better understand and quantify differences in penetration and flow performance between reactive shaped charges and conventional shaped charges, we designed a test matrix that takes into account various environments, such as gas in low permeability rock and oil in higher permeability rock. The performance assessments of reactive vs. nonreactive perforators were performed under controlled conditions in an API Perforation Flow Laboratory (PFL) (API 2006).
The tests, which involved shooting into stressed rock under simulated downhole conditions, were conducted in Berea Sandstone targets with mineral oil flow to simulate a typical oil-bearing formation, and in Carbon Tan Sandstone with nitrogen flow to simulate a typical gas-bearing formation. The Berea Sandstone represented moderate-to-high porosity and permeability rocks with high, unconfined compressive strength (UCS). The Carbon Tan Sandstone represented low-permeability and medium-porosity rocks with moderate UCS. To further understand the contribution of the reactive component, tests were performed in balanced, underbalanced, and overbalanced conditions. Charge performance measurements were taken for both conventional and reactive charges in each target reservoir rock. This paper describes the methodology used for the comparative tests between reactive and nonreactive perforators in the Berea Sandstone portion of the program and summarizes the observations of core penetration, clean up, and productivity.
The API Recommended Practices for evaluating well perforators (API 2006) provides an essential protocol for measuring and quantifying the effects of changes to shaped-charge perforators designed for increasing penetration and flow performance. Laboratory simulation of a downhole perforating event involves detonating a single shaped charge into a stressed porous media using a hardware configuration that is similar or equivalent to that used in the wellbore. In this study, three different reactive charges and one conventional charge, all under the sub-grouping of deep penetrators (DP), were shot into two sets of downhole-configured targets, and the penetration and flow performance were compared. Three borehole conditions were simulated for each of the four charges: underbalance, balance, and overbalance. For statistical validity and verification, the test for each borehole condition was repeated three times and independently witnessed, resulting in a total of 72 tests.
To replicate downhole perforating conditions, the setup consisted of commercially available 3-3/8-in. deep-penetrating shaped charges (listed in Table 1) that were shot from inside a pressurized wellbore using a simulated single-shot perforating gun, through a simulated scallop, fluid gap, casing plate, cement sheath, and into the formation-analog rock. Phase I used a stressed Berea Sandstone core filled with odorless mineral spirits (OMS), and Phase II used a stressed Carbon Tan Sandstone filled with nitrogen (Table 2). The acquired data include, but are not limited to, depth of open perforation tunnel, depth of total perforation penetration, the perforation geometry, hole diameter in casing and cement, flow performance, flash radiography images, and time vs. pressure traces (Appendix A), as well as statistics on significance (Appendix B), CT scans (Appendix C), and thin sections of the perforation tunnel walls (Appendix D).
