Best Practice for Cementing and Zonal Isolation Using the Jet-TypePerforate, Wash and Cement Technique

摘要

In 2014 ConocoPhillips (CoP) decided to focus on the Jet-type perforate, wash and cement (P/W/C)technique as its primary permanent well abandonment method for setting a full cross-sectional cement/steelbarrier. Following this decision, a quality improvement project was launched to prepare for a transitionfrom Cup-type to Jet-type P/W/C to improve barrier plug quality. The initiative was presented during theStavanger P&A Forum (PAF) conference October 2014 for information and to indicate for specific vendorsthat there were opportunities for participation. The perforate, wash and cement method is complex and as with any cementing operation there isoperational risk involved. This paper is written to share ConocoPhillips experience and learning from theimprovement project which is still ongoing. It is specifically written for drilling engineers planning Jet-typeP/W/C operation to help identifying key parameters to achieve a top-quality operation as well as managingthe operational risk inherent to the operation. Quality requirement in P&A operations? It can be a hard sell to argue for costly fluids, BHAs (bottomhole assembly) and TCP (tubing conveyed perforation) guns to plug off a depleted reservoir where the testof time is hundreds of years from now as the reservoir gets pressurized again. The latter is not the case in theGreater Ekofisk Area (GEA) where active water injection increases the average reservoir pressure quicklyand the established production strategy is dependent on good isolation of abandoned wellbores. To get a ‘’good’’ P&A plug you need to understand how to prioritize and control the variables such ascement properties, drilling fluid properties, drill pipe and BHA design, hole cleaning, ECD, displacement,TCP performance, operational sequence and many more. ConocoPhillips have made a structured approachto build a process which captures the basics of getting a high quality well abandonment plug. Thedisplacement process itself has been modelled with computational fluids dynamics (CFD) software tounderstand key drivers for the placement of a cross-sectional P&A plug.