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Traditional API Recommended Practice 431 Section 1 test of a gun system is focused on determining the perforation characteristics from the point of view of a perforating gun fired into rock of significant unconfined compressive strength. Entrant hole size and depth of penetration are the key parameters measured to demonstrate the gun system performance. These parameters do not tell how the energy of the penetrating jet is dissipated in the formation nor do they characterize flow from the formation through the perforation. The API Section 4 test is a means of producing the information desired, flow characteristics of the rock after perforating. These tests are expensive, long and difficult. Furthermore, the API Recommended Practice 43 does not include a test method for evaluating perforators used in unconsolidated sand formations, but only simulates perforation in competent rocks. However, in unconsolidated sands, the guns do not produce a "tunnel or cavity" in the sand. Rather, the perforation path is filled with crushed sand and debris that strongly influence the flow properties of the perforation and requires characterization. Two years ago the authors presented data showing a simple sand filled clamshell target could provide useful information for the development and design of shaped charges for unconsolidated sand. Suggested here is a standardized test method for a target focused on measuring the gun performance from the viewpoint of the formation while retaining the gun system performance parameters and developing a correlation between perforation path damage and perforation flow characteristics. |
