One Trip 7" Multi Zone Gravel Pack System: Success Case and Learning Points from the First Installation in Malaysia
Abstract Main reservoirs in this brown field are designed with Cased Hole Gravel Pack (CHGP), which is a proven sand control technique in the area. Most multi-stack reservoirs in these wells require individual sand control treatment on each zone as the formation properties varies from one to another. One of the most recent success case was the installation of One Trip 7" Multi Zone System that enabled implementation of an optimized High Rate Water Pack sand control operation in the casing size. This new technique helps to make more multi zone CHGP in infill or sidetracked wells feasible and more economical. Previously, CHGP design in 7" casing was limited to stack pack design which means the steps of sump packer installation, perforation, deburr run, GP assembly installation and GP pumping have to be repeated for every zone. The repeated process was laborious and incurred a lot of cost due to the extensive rig time. With the new 7" one-trip design that evolved from the existing 9-5/8" system, the multiple zone GP treatment can be done in single trip and contributes to significantly reduced well cost. One of the design consideration that need to be focused on is selection of carrier fluid to ensure optimum carrying capability during proppant placement while reducing the pumping friction through the one trip system. Full coverage of screens and blanks was achieved for both zones that were completed with the One Trip 7" Multi Zone completion. Both zones were treated with hybrid pack that is combination of circulating and HRWP. The primary objectives on optimizing rig time were achieved in eliminating multiple runs for different zones, as well as reducing risks of multiple disengagement with lower assembly that adds difficulty during reverse-out operation. One of the key limitations of this system is the high friction pressure when pumping through long concentric wash pipes and this can affect the effectiveness during proppant reverse out, especially considering the burst rating of the casing as well. Due to this known restriction, cement have been designed and tested up to the anticipated annular pressure during reversing out operation. Another design factor that could also pose a challenge during operation is the limit of sand concentration that is 1 ppa and this again is due to concentric wash pipe design.