The drive to recover hydrocarbons from difficult to reach reservoirs and optimize production is taking center stage in the Exploration and Production industry. Complex wells are being planned which push the existing technology to limits. The success and longevity of such wells depends upon providing good zonal isolation and sound well integrity for the complete life cycle of the projects. Cementing the wells in a narrow pressure regime without losses and overcoming challenges for optimum zonal isolation presents a unique test to the industry.
The Extended-Reach-Drilling (ERD) wells drilled in the Caspian Sea prior to 2011 have historically seen inadequate zonal isolation in the long intermediate section due to channeling of cement during placement; consistent with directional profile of the wells. Remedial cementing was needed in some cases before the next phase of the well.
As the acceptance criteria for well integrity becomes more stringent, the onus lies on achieving zonal isolation during primary cementing through a combination of optimized cement placement and mechanical barriers. This paper presents the investigative approach towards earlier jobs and the recommended suggestions which led to improvement that was confirmed by cement evaluation logs. The authors present case histories with lessons learnt during the course of implementing the new approach to cementing design and the success of achieving adequate cement coverage across potential flow zones.