The current API RP-43 procedures for deep penetrating shaped charges require that they be tested to Section 1 (Evaluation of Perforating Systems Under Surface Conditions, Concrete Targets) and Section 2 (Evaluation of Perforators Under Stress Conditions, Berea Targets).1  The Section 2 procedures compare charges and estimate penetration in natural rock under simulated downhole conditions. This test is conducted on a single charge.

The objectives of the Section 1 (Concrete Target) procedures are

  • to estimate the hole size in the perforated casing

  • to test the system.

The primary objective of a system test is to determine if the single charge performance on the Section 2, test will be representative of the shots in actual field hardware. Many variables of the system can effect actual field performance.2  This paper discusses one factor that can adversely effect shaped charge performance in a perforator system: explosive interference.

For the purposes of this paper, explosive interference is defined as the reduction of shape charge performance under single shot performance as a result of geometric and explosive factors in a gun system. Many factors can contribute to explosive interference in a perforating system. These factors are not the subject matter of this paper; rather, this paper focuses on detecting explosive interference with modified API RP-43 Section 1 procedures.

Explosive interference in a gun system can range from very severe to very slight. Severe interference may be obvious by the condition of the gun carrier and the casing hole size. Penetration reductions of 50% or more have been observed with this type of explosive interference. However, observations made on modified API Section 1 tests have shown "slight interference" can reduce overall penetration by as much as 35%. This interference can not be detected by observation of the gun, casing, or standard Section 1 concrete penetration data.

After performing many API RP-43 Section 1 tests with high shot density perforators (over 4 spf), an improved API RP-43 Section 1 test procedure has been used successfully to determine whether significant explosive interference exists in a perforating gun system. This modified procedure assures that field perforator systems do not have an explosive interference problem that reduces perforator performance significantly below published Section 2 data.

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