A major North Sea operator was looking to improve production from low permeable reservoirs in mature assets. Under-displaced, high proppant concentration fracs must be pumped in an efficient manner to unlock the value potential. A new single-trip, multistage stage proppant fracturing system was developed to tackle these operational constraints and reliably perform in challenging offshore environments. This paper presents the evolution of this system from a concept to field implementation on the Norwegian Continental Shelf.
The developed solution, a frac sleeve (FS) system operated by a service tool assembly (STA) which can be run on drillpipe or coiled tubing. The unique feature of this system is that it allows multistage stimulation in a single trip without utilizing slips or packers, which could pose the risk of a stuck STA. Suited for both open-hole and cemented applications, the system is particularly beneficial for wells with limited slack-off capabilities. Key considerations of the design included operability in proppant-packed environments, erosion resistance, and multiple contingencies built into the STA to allow operational flexibility.
An extensive qualification program was successfully executed to validate the system's functionality, particularly in hostile, proppant-packed environments, including an erosion test wherein 2,000 tons of proppant was pumped through the STA at 30 bbl/min. In preparation for field deployment, drillpipe and liner simulations were run, and operational planning and risk assessments were held. Following these assessments, the system was deployed for the North Sea operator in a trial well in summer 2021. During the stimulation program, an under-displaced, high rate, and high proppant concentration frac was pumped in each stage, followed by immediate closing of the sleeves prior to reversing out the remaining under displaced proppant. This paper captures the wins, challenges, and key learnings from the initial trial well, and how these learnings were used to optimize the second well.
Also detailed is the lifecycle of a novel, patented proppant-stimulation technology starting from initial concept to downhole deployment. Enabling optimized, proppant fracturing in an operationally efficient manner plays a crucial role in improving the productivity and economic viability of a well, and allows for improved oil recovery (IOR) from existing offshore infrastructure. The findings and lessons learned in this paper will contribute to the state of knowledge regarding proppant fracturing on the Norwegian Continental Shelf.