A major operator in onshore Middle East was planning to conduct a water shutoff intervention in an oil producer with very high water cut and a naturally fractured carbonate reservoir. The well was completed horizontal with 18 inflow control device (ICD) elements and 16 swell packers along the production liner and openhole section. The production tubing had an electrical submersible pump (ESP) and Y-tool to allow access to the horizontal section. Due to the complexity of the completion and limited access to the reservoir, an engineered approach combining a precise placement method with a reliable water conformance chemistry was necessary.
The engineered approach relied on the use of coiled tubing (CT) equipped with real-time downhole measurements, high-pressure rotary jetting tool, backpressure valve, and through-tubing inflatable packer. Downhole readings included CT internal pressure, annulus pressure, annulus temperature, and casing collar locator (CCL). They were used both to achieve optimum use of the rest of the bottomhole assembly during the intervention, and to evaluate treatment effectiveness. The selected water conformance fluid system combined a medium-molecular-weight polyacrylamide crosslinked gel for fissure plugging with a nanoparticulate leak off control additive to keep most of the polyacrylamide gel within the fissure network.
In horizontal wells, critical steps for water shutoff, such as proper wellbore conditioning, accurate placement technique and controlled fluid penetration, cannot be accomplished through conventional methods, especially in completions with flow control components, and innovative methodologies are required for efficient intervention. An evolved approach for water shutoff intervention relying on real-time downhole data was implemented for the first time in this field, reducing water production from 1300 B/D to 400 B/D, while increasing oil production from 180 B/D to 350 B/D. In the first run, high-pressure rotary jetting tool was used to condition the wellbore tubulars across the inflatable packer planned anchoring depth. In the second run, the through-tubing inflatable packer was set at the target depth, and the water shutoff treatment was pumped into the formation across the target ICDs. CT real-time downhole measurements were instrumental for accurate depth correlation, ensure optimum differential pressure across the high-pressure jetting tool, to control inflation and anchoring of the through-tubing inflatable packer, and to monitor the water shutoff treatment.
This engineered approach, which leverages the use of real-time downhole data to accurately control the positioning and actuation of high-pressure jetting tools and through-tubing inflatable packers, enables critical interactions with formation and completion. This level of control is critical in water shutoff operations, for it enables the customization of original designs based on the changing downhole conditions to achieve maximum effectiveness of the sealing fluids.