Abstract

Several recently introduced oilfield perforators incorporate reactive materials that are derivatives of military-based weapons technology. Perforator suppliers claim that using reactive charges facilitates tunnel cleanup creating optimized perforations, thus improving downhole performance leading to increased well productivity. To better understand and quantify differences in penetration and flow performance between reactive shaped charges and conventional shaped charges, a comprehensive test matrix was designed. The performance assessments of reactive versus nonreactive perforators were carried out under controlled conditions in an API Perforation Flow Laboratory (PFL) (API, 2006).

The Phase I tests for this study, 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. Phase II testing will be conducted 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 will represent low-permeability and medium-porosity rocks with moderate-UCS.

In order to further understand the contribution of the ‘reactive’ component, tests designed for this study are carried out in balanced, underbalanced and overbalanced conditions. Charge performance measurements are 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, tunnel cleanup and productivity.

Introduction

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 similar to, 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 the same downhole-configured target and the penetration and flow performance are compared. Three borehole conditions were simulated for each of the four charges: underbalance, balance, and overbalance. For statistical validity, the test for each borehole condition was repeated three times and independently witnessed.

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 a stressed Berea sandstone core filled with odorless mineral spirits (OMS). 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, the flow performance, flash radiography images, CT scans, time versus pressure traces, and thin sections of the perforation tunnel walls.

Test Conditions

Phase I of this study focused on simulating perforation of an oil-producing formation in an API test chamber (Fig. 1) using Berea Sandstone with OMS as the flowing fluid. Phase II focused on simulating a low-permeability gas formation using Carbon Tan Sandstone with nitrogen as the flowing fluid. Phases I and II consisted of 36 tests each. This paper describes the results of Phase I. The results of Phase II will be presented at a later date.

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