Improving Operation Safety of Multi Zone Single Trip Gravel Pack : Holistic Approach to Minimize Well Control Risk in Mahakam

Abstract

Abstract Multi Zone Single Trip Gravel Pack (MZ-STGP) system has been the main solution for developing shallow reservoirs in the Mahakam Delta, Indonesia. Despite providing cost effective solutions, the system poses safety challenges related to well control. These challenges (i.e long non-shearable period (NSP), heavy completion fluids losses, severe cross flow and trapped gas) must be overcome in design and operational stages. Robust operating procedures and new equipment have been developed to assure safe and efficient operation. Three main steps of completion (perforation, concentric completion make up and service tool manipulation) were identified as critical and may generate a major well control situation. The completion design phase shall address the issue by carefully targeting appropriate reservoir characteristics, selecting perforation length and total gross net pay. Specific procedures for perforating and making up and manipulating service tools were generated and continuously improved. The continuous improvement process was able to avoid classic challenges such as heavy completion fluid losses after perforating long heterogeneous reservoirs or heavy losses following reservoir stimulation. Specific tools and equipment such as screens with closing sleeves were designed and deployed to assure the whole process was undertaken safely. One of the important innovations was first worldwide use of a dropping table system to handle multiple concentric pipes. This was developed for two different systems through careful engineering design. It allows securing the well in less than 30 seconds. To date, more than 200 wells have been safely completed without any major well control issue. Most importantly, the robust safety approach did not hinder operational performance as very low Non­Productive Time (NPT) has been maintained since 2008.