_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 36084, “Use of PWC Technique for Abandonment in Deepwater Scenarios: Overview and Lessons Learned From Operations in Brazil, ” by Rafael P. M. Moreira, SPE, Aline G. G. de Oliveira, and Rodrigo D. Lucchesi, Petrobras, et al. The paper has not been peer-reviewed. Copyright 2025 Offshore Technology Conference. _ The perforate, wash, and cement (PWC) technique was developed to improve abandonment efficiency and enhance the quality of hydraulic isolation required to establish dependable barriers. In subsea scenarios, significant logistical challenges exist, such as the use of a large volume of spacers and high operational times for complete circulations, which can prolong the operations before actual cementing operations. The complete paper details the first four operations carried out in deepwater scenarios in Brazil, where PWC application in scenarios in other countries required adaptation for the unique characteristics of the operator’s wells. PWC Technique The PWC technique consists of a sequential operation that allows casing communication (perforation), annular cleaning (washing), and final cementing. Compared with conventional methods, PWC typically is more productive because all steps can be performed with a single bottomhole assembly (BHA) that allows sequential processes on the wellbore. The three steps can be detailed as follows: 1. Perforate: This stage allows communication between the internal string and the annulus. This region may be a concentric casing annulus or an openhole annulus. Typically, explosive charges are used previously installed at the PWC BHA. 2. Wash: To clean the annulus for further cementing operation, the washing is performed to ensure that no solids, mud cake, or any other undesired fluid remains at the interval. Based on the basic principles of well cementing, wellbore cleanliness will allow cement to fill the zones and guarantee continuity and bonding to the wellbore or casing. Washing is performed by controlling pump rates while pulling the BHA in front of the interval. 3. Cement: This operation is performed controlling the pump rate while pulling the BHA. Cement slurries must be designed and tested properly for the right thickening time, rheology, free fluid, and fluid-loss parameters. Sensitivity tests also are required to evaluate the effect of slurry contamination by spacers or well fluid. With regard to the main components of a PWC BHA, from the bottom, the perforation section is located immediately above the BHA base, followed by the internal cement foundation (ICF). This equipment seals the internal casing as a cement base after explosives are fired. Placed a few subs above, the jetting tool washes and cleans debris in the annuli behind the perforated casings. Finally, for the cementing itself, specific equipment is associated with a flux diverter. PWC technology has been used in several locations, with more than 660 operations globally and a high success rate. However, it has been introduced only recently in Brazilian shallow and deepwater scenarios.
Chris Carpenter (Fri,) studied this question.