The Critical Role of Real-Time Downhole Telemetry for the Success of Conformance Control Operations with Extreme Permeability Contrast
Authors: Aglyamov Mansur , Molero Nestor , Nabki Felix , Mhiri Adnene , Djanaka Pramudya 
Published: November 2020

Achieving efficient reservoir sweep is a challenging task in formations with extreme heterogeneity. For instance, the presence of natural fractures in carbonate injector wells often prevents obtaining uniform injection profiles. This represents a major challenge for field development, not only due to poor reservoir sweep efficiency, but also due to early water breakthrough in producer wells. To treat both problems, a new approach to executing conformance treatments in water injectors was implemented in the Middle East.

The proposed methodology yields a uniform injection profile by combining two contrasting treatments in the same operation: mechanical isolation and chemical suppression of the high-intake zone and stimulation of the low-intake zone. Isolating target zones with a coiled tubing (CT) deployed inflatable packer enabled combining the suppression and stimulation treatments in a single intervention. Each treatment can then be tailored by leveraging real-time CT downhole measurements, and injection profiles can be balanced by adjusting the degree of suppression and stimulation based on the target injectivity index for each zone.

This new approach was successfully implemented in more than 10 injector wells. The CT-deployed inflatable packer allowed dividing the operations in two separate treatments, above and below the packer, on the same run. The stimulation treatment was performed on tight zones, immediately followed by a suppression treatment on the dominant section. That suppression helped reduce injectivity across the main interval by pumping suppressant material—calcium carbonate—in varying concentration and batch size. Treatment progress was evaluated and controlled in real time thanks to CT downhole sensors, which monitored the response of the formation as each batch hit target intervals, until the desired injectivity index reduction was achieved. The ability to make fast, informed decisions based on those downhole measurements was the cornerstone of this new conformance methodology, which allowed full control of treatment execution by monitoring changes in injectivity on the spot. After each treatment, an injection logging tool (ILT) was run to assess the final injectivity profile. ILTs showed an average improvement above 60% on well conformance even several months after the treatment, indicating a balanced injection distribution between the zones. In certain cases, injected water distribution was found completely equalized between weak and dominant zones. This allowed maintaining equal pressure support across all zones and balancing the production profile in the adjacent producer wells.

Improving the injection profile by performing selective stimulation treatments had been already proven successful in the subject field. The new approach further developed selective stimulation to achieve an unprecedented level of conformance in this highly heterogeneous formation while bringing an estimated gain of 75,000 BOPD from the first 10 intervened wells, which represents a 50% improvement with respect to the previous methodology.