Successful Gas Shutoff Operation Using a Coiled Tubing Telemetry System: A Case History

Abstract

Summary In a deviated well in the Caspian Sea, the gas/oil ratio (GOR) increased rapidly in 2017. The result was an oil rate decline with several choke backs to manage GOR buildup. After performing two production-logging jobs, it was confirmed that 76% of the gas production was coming from four upper perforations. The main objective was to perform a gas shutoff (GSO) treatment in two stages to reduce gas production by squeezing polymer into the formation and setting packers at a 59° deviation inside a 9⅝-in. casing for temporary isolation of the middle and lower production sands. Fifteen runs were performed with a tube wire-enabled coiled tubing (CT) telemetry (CTT) system that consists of a customized bottomhole assembly (BHA) that instantaneously transmits differential pressure (DP), temperature, and depth data to the surface through a nonintrusive tube wire installed inside the CT. For the first time in the region, a tension, compression, and torque (TCT) subassembly was deployed to control the entire setting/retrieval process with accurate downhole upward/downward forces. CTT technology was a key element to successfully set two through-tubing inflatable retrievable packers (TTIRPs) by performing casing collar locator correlations at the tubing end, which was 133 and 228 m [measured depth (MD)] shallower from the setting depths. In addition, during the second GSO operation, the GSO gel system crosslink time was modified on the basis of the actual bottomhole temperature (BHT) recorded with the CTT system. Finally, during the third GSO operation, treatment placement was improved, spotting more GSO gel system inside the casing section and avoiding further treatments. After successful placement of the GSO gel system, a drop from 15.5 to 4.5 MMscf/D in gas production was observed (GOR reduction from 11,000 to 750 MMscf/bbl) with an oil rate increment from 1.4 to 6.04 Mbbl/D. Furthermore, after the gas reduction, the operator was able to produce between 1.5 and 2.0 Mbbl/D from other wells that were choked back on the basis of gas handling capabilities limitations. In the short term, GOR reduction sustained at 3,000 MMscf/bbl and 3.0 Mbb/D oil rate. The novelty of using the CTT system and TCT subassembly for real-time monitoring of BHA data proved to be beneficial for positioning two TTIRP, modifying GSO gel system design, placing it precisely across target intervals, and retrieving two TTIRPs that in the end provided direct and positive financial impact for the operator.