Abstract
The subject well is an onshore oil producer located in Cairn Energy India’s Rajasthan block. The well had stratified sand sections completed with 4-inch inflow control device (ICD) screens and isolated by swellable packer assemblies. The well was put into production at a rate of approximately 1,000 bopd; however, due to formation damage – notably paraffin and scale - the well could not sustain production and eventually ceased.
Our objective was to selectively stimulate 15 ICDs using coiled tubing. The well had a minimum restriction and a larger setting diameter which warranted the usage of coiled tubing deployed inflatable straddle packer system. This enabled passage through the restriction and setting in the larger outer diameter to selectively treat each zone by mechanically diverting the stimulation fluid.
The challenge was significant. Multiple zones required treatment in a single run by performing 15 multi-settings, maintaining seal integrity following each set, and returning the tool to its original outer diameter for retrieval. The well was deviated at 74 degree which challenged accessibility.
The assembly was run successfully and managed to selectively stimulate all required zones in one trip. Using this application, we confirmed that all treatment fluid was effectively sealed and treated by diverting the treatment fluid directly into the required zone, preventing more permeable sections absorbing most of the fluid, and ensuring the treatment chemicals were used in a cost effective manner. The single coiled tubing run avoided multiple runs to isolate sections using plugs. The well subsequently began to flow once lifted with nitrogen, positively indicating that the ICDs were effectively cleaned and the zones successfully treated.
This case demonstrates the innovative use of thru-tubing wellbore isolation techniques to effectively enhance production in wells with challenging configurations and operating parameters. This study further paves the way for similar interventions in wells with similar characteristics.
