Through-Tubing Snake Tool Installation Enables Remedial Intervention in a Niger Delta Condensate Gas Well

Single string-single interval completion design has been traditionally adopted for high-rate Niger Delta condensate gas wells because of ease of the large-size tubing installation and integrity of the bottom production packer assembly. Following the incident of leaking packer and the loss of safety barrier above the bottom completion interval, wells were re-entered with workover rig for integrity repair. A pragmatic approach taken was to install a new production string and packer after tubing cut and retrieval with the old packer stump assembly remaining in hole. The resulting gap between the top and bottom completion configuration has hampered through-tubing tool conveyance into the sump during subsequent rigless remedial intervention. To overcome this challenge, a tubing conduit (snake tool) with maximum possible internal diameter was configured to be stabbed into the lower completion tubing stump and hung-off at the landing nipple profile within the top completion. The snake tool was made of conformable material for the corrosion risk environment due to presence of corrosive CO2 gas in the produced condensate gas and existing downhole completion string made of 13Cr tubing plus accessories. Reliability and robustness of the tool was evaluated based on the expected well operating envelope including analysis of the mechanical strength, stresses, and erosional risks at expected downhole conditions. The 3.78-inch snake tool was able to restore seamless wellbore access to the lower tubing break, approximately 25ft below. This tool will facilitate planned through-tubing remedial activities such as perforations, mechanical water-shut off, zonal isolation and chemical stimulation interventions. The wireline snake tool deployment which took only 6 days has proven to be highly cost efficient given the elimination of a rig workover. This paper enumerates the investigation and preparation of the snake tool application from the design stage to the field execution in the 10,700-foot-deep gas well. It is expected that this low-cost repair technique will be extended to many other similar gas wells in the region.