Wellbore enlargement technique such as hydraulic fracturing or frac packing (or extension pack using linear gel) treatment is very much required in the brown field reservoirs with unconsolidated sands, poor sorting, and uniformity coefficient as well as very high fine content. The cost escalates when this requirement happens for multiple zones which needs longer rig time. This paper will discuss on the execution part of 7" ESTMZ system deployment, extension pack design, lessons learnt and required mitigation on the system itself. Conventionally, most of the operator will perform extension pack operation using stack-pack technique which required longer rig time, due to repetition of perforation, deburring and installation of gravel pack assembly which followed by gravel placement operation based on number of zones. Further optimization is the Single Trip Multi Zone (STMZ) system developed to enable multi zones gravel placement treatment and installation done in single trip in order to reduce the rig time. However, the 7" STMZ system is still have some limitation on its pumping capability due to system design and high friction pressure hence unable to be used for any frac-pack or extension pack treatment.
The next generation of 7" ESTMZ system was introduced to overcome all the limitation of its predecessor and enables the frac-pack operation to be performed in a single trip manner which assuredly reduced considerable rig days. Furthermore, this system can eliminate deployment of inner string inside lower completion assemblies for zonal isolation and reservoir selectivity which can be risky especially in highly deviated wells. This system comes with modular screen design with integrated sliding sleeve with proprietary shifting profile. Like the conventional stack pack system, a sump packer will be run in hole via wireline and tractor as a base for sump area and depth reference. Then, the well is perforated with oriented gun and selected perforation technique for all zones in a single trip followed by debur run using wellbore clean out BHA. ESTMZ assembly is deployed to cover all zones with single concentric wash pipe system for the treatment. The zone interval length and zonal spacing are fully independent and may come with various length as oppose to the STMZ system. Hence, no dummy zone is required.
The gravel placement design for this particular field was designed precisely to contain the growth to avoid fracturing into the nearby coal, shale, and water contact region. As a result, the reservoirs were successfully treated with extension pack of 220lb/ft packing factor at highest proppant concentration of 4.8ppg and 10bpm pumping rate.
The technology discussed in this paper is a first in the world application in highly deviated well category where the author is intended to register the pain points as well as best practices to be replicated.