First Campos Basin Raw-Water-Injection Well: Sand Control and Stimulation

Abstract

As part of the production sustainability project for the Albacora Field, in Campos Basin, Brazil, it has been planned to inject raw water (RWI) above the fracture pressure (IAFP). The main drive for choosing RWI was the big difficulty to properly treat the injection water in the very busy Albacora platforms.The injection target reservoirs are unconsolidated, demanding a robust sand control method. The operator's first choice would be an OHHGP with premium screens. However, due to extremely aggressive amount of dissolved oxygen, the RWI demands a very special metallurgy. The manufacturing and acquisition process of mesh premium screen or wire wrapped screens, in this special metallurgy are extremely expensive and can last many years. Besides that, these kinds of screens are prone to crevice corrosion.To cope with this new challenging scenario, an innovative lower completion was planned and executed: -use of a 4,5" alloy 625 sloted liner, run in an 8,5" hole; -maximizing the slot opening to 400 micrometers, in order to minimize the plugging process and the corrosion by the non treated sea water and to maximize the liner mechanical resistance; -use of 3 ABTs (2 ECPs and 1 swelling packer) to protect the production casing. Also, due to the low fracture gradient, combined with an unfavorable mechanical configuration, it was necessary to reduce the risk of partial packing:-use of the Rat Hole Zero conception, with the pioneer application of a retractable casing shoe in the 9 5/8" production casing; -use of light proppant (alpha wave) combined with ultralight proppant (beta wave). Besides that, due to the inexistence of inverted seals to provide the divergence for the conventional mud cake removal through an acid treatment, the option was:-the mud cake removal using a pre-cursor formic acid. The desired injectivity index was not obtained and the contingency was applied: -backflow, followed by the bullheading of foamed 15% HCl (it was the first application of this stimulation method in a Campos Basin OHHGP well). The final result, in spite of this great amount of technological innovations, were wells that fulfill all the reservoir engineering requirements.