Extended Abstract: Complex Offshore Well Intervention Now Possible by using Thru-Tubing Bridge Plug to Produce By-Pass zone and Isolate Lower Production Zone

Abstract

Isolating lower production zone (water shut-off) and finding new perforation intervals from another reservoir zone is a typical well intervention application in mature fields. In normal conditions, legacy permanent barriers (Through Tubing Bridge Plugs -TTBP) have been used in those applications very successfully. However, challenges are posed by, well bore restrictions (passing smaller OD restrictions), rig height, reliability and setting validations with legacy tools in harsh environments and well conditions. This paper discusses the challenges during offshore well intervention operation in Indonesia due to the limited space for rig-up, limited crane lifting capability, and un-manned well platform with only daylight operation and the solutions for these challenges with new slim-sized TTBP technology and the slim-sized Pulsed Neutron tool. Critical success factors of this operation included providing valid gas saturation data by using a 1 11/16" Pulsed Neutron tool (TMD3D) to determine the remaining gas in producing interval and any bypassed opportunities; establishing enough force by using a slim size electromechanical setting tool (DPU) to set the 1 11/16" TTBP at the desired depth and establishing a mechanical barrier which can hold up to 1200 psi differential pressure until a cement cap can be established; and running a perforation simulation to select the right gun to create an effective perforation tunnel between the wellbore and the formation for optimized gas production from the bypass zone. Despite all the challenges, a good mechanical barrier was established to isolate the lower water production zone and successfully determine gas saturation in bypassed reservoirs by using the Pulsed Neutron data. Perforation intervals were selected with the pulsed neutron analysis. After perforation, significant gas production was established which was 50% higher than predicted. New slim-sized technology tools resulted in flawless job execution with their high reliability and cost-effective solutions without any service quality issues. In addition to increased gas production, efficient operation resulted by completing the job one week earlier than scheduled, which provided extra cost savings. This case study identified the challenges in complex well intervention operations and provides a valuable water shut off solution by using new 1 11/16" TTBP and 1 11/16" DPU technology. The solution has proven to provide tremendous cost saving for production enhancement activity.