Zonal Isolation in the North Sea
19 June 2022
Ever since the early 1970s, when production from the first gas and oil fields in the North Sea started, the Norwegian Shelf and the UK Continental Shelf have been some of the world's most important hydrocarbon producing areas. As the wells in this region are getting older, operators are faced with the challenge that these wells are starting to produce more and more water.
Furthermore, as fewer exploration and drilling permits are being given out, operators are looking for ways to maximize production from current wells. Combined with current geopolitical situation and the subsequent rising oil and gas prices, there is a strong drive among operators to produce as much as possible from the current infrastructure.
Zonal isolation is vital in meeting these ambitions. Properly isolating different production zones within a well significantly reduces water production, which in turn increases oil and gas production. A significant added benefit is that reduced water production also greatly reduces the environmental footprint for operators, as there is less water to treat and dispose of.
An alternative to well recompletions
During a recompletion, a separate wellbore is drilled from an existing casing in order to reach the same reservoir, which typically is a costly endeavour. Especially in the North Sea region, where employing a rig is expensive, and weather conditions can form a challenge during the winter months, operators will avoid a recompletion where possible.
With our ZonalSeal technology, we follow a different approach. By precisely injecting a high viscous sealant into the space between the wellbore and the formation, we are able to isolate the annulus. After our custom injection tool is retrieved to the surface, a conventional bridge plug is run and placed inside the tubing to isolate production from the water reservoir below.
Precision is Key
For optimum results, it's key that the epoxy seal is placed at precisely the correct location. That's why our specialists work closely together with reservoir engineers and geophysicists to study and evaluate the well in great detail. After extensive well logging has been performed to determine the fluid levels within the well's individual zones, we study the layout of the well completion and the geology of the surrounding formations. Based on these findings, we select the optimal location(s) to place our epoxy seal(s).
After the location is selected, we customize our epoxy's viscosity, rheology, and density according to the relevant well conditions. Consequently, we run our downhole delivery tool to the selected location in the well. During placement of the plug, the tool is fully controlled and monitored through our customized Graphical User Interface (GUI) by CannSeal specialists. At the surface, the operator has full, real-time control over tool positioning, perforation functionality and ensures that the pumping pressure, injection rate and volume of sealant are managed. This guarantees that the epoxy plug is delivered precisely into the annulus.
Our downhole delivery tool, which incorporates the epoxy sealant, can be run on electric wireline or electric coiled tubing as a single, standalone operation, with no need for rig-assist. This ensures that the delivery of our sealant is a low-cost intervention option. Especially for subsea wells, which are quite common in the North Sea, the ability to operate from a Light Well Intervention (LWI) vessel is a significant advantage compared to traditional interventions.
To date, CannSeal has completed over 70 runs in petroleum wells. Of these runs, roughly 25% were performed from an LWI vessel, underlining our technique's cost-effective and agile character.