Tests to Compare the Performance of Zinc and Steel Big Hole Charges: First of its Kind in an HP/HT Setting

Abstract

Using the upgraded capabilities of the perforation flow laboratory, and after some trial and error, tests were successfully conducted designed to compare zinc and steel-cased big hole (BH) shaped charges at bottomhole conditions. In the past, conducting perforation performance tests that included wellbore control were limited to matching reservoir pressures up to 5,000 psi. These tests were conducted at conditions representative of a Gulf of Mexico (GOM) reservoir exhibiting 17,200 psi overburden stress, 9,100 psi pore pressure, and a temperature of 210°F. Completion plans include setting the wellbore pressure at 10,550 psi before perforating to create a static overbalance of 1,450 psi. Aligned with American Petroleum Institute Recommended Practice 19B (2006) Section 4 (Rev. 2014), the tests were conducted to closely match the perforating portion of the completion design in the oil-producing field to provide an effective physical simulation. The outcome provides useful perforation performance data, including flow into and out of the perforation. Many design modifications from previous ambient, limited pressure Section 4 tests were necessary to successfully conduct the tests at the higher GOM reservoir pressure and 210°F. This paper discusses the difficulties encountered during testing and how workable solutions were achieved to perform such tests. Reinforcing the integrity of the soft, producing formation analog core without reducing the effective stress was the most significant challenge encountered during this study. Sustaining steady flow at pressures higher than the limits of the available high-accuracy pressure transducers and flow meters also required a new approach. The net result of this effort revealed that penetration depth differed less that previously assumed between the zinc-cased charge and the steel-cased charge at the experimental conditions and setup used in the tests. The development of perforation testing laboratories has allowed the capability to shoot any shaped charge in a simulated wellbore environment at elevated temperatures and high pressures, matching virtually any reservoir in the world.