Case Study: Design, Execution and Results of Retrieving Challenged Gravel Packs, the Future in Workovers

Abstract

Workover is the process of performing major maintenance or remedial treatments on an oil or gas well to restore, prolong or enhance its production. The complexity of workover operations is increasing due to the well conditions faced, such as age, environment, mechanical restrictions, completion design, number of completed zones, downhole equipment installed, etc. Well workover can represent up to 49% cost reduction over its sidetrack option, making it economical; but it may require good sand control understanding, and comprehensive procedures, to retrieve existing gravel pack (GP) assemblies, an operation that possess the risk of getting stuck and/or being unable to retrieve the assembly and eventually abandoning the well. For many years the Oil Industry has rejected workover candidates because of risk aversion overriding cost and value added; the actual workover opportunities include new challenges such as retrieving Alternate Path screens. This paper discusses the design, risk management approach and the challenges faced during execution, as well as the lessons learnt, of two workover wells in a brown field; both candidates had several challenges such as: Old completion,Lack of reference data,Length of screens (500 ft of screens)Sand productionDifferences to retrieve Wire Wrap and Alternate Path screens The two successful retrieval of the sandface completion in both wells were the first and second operation of its kind performed by the operator and provide field experience and best practices for future similar operations. Furthermore; the study of the retrieved assembly, after over 20 years of production, helped to understand the sand management system failure mode and the reasons for the sand production issue; knowledge that will impact future well designs in the field.