There are more than 100 accumulations in the southern North Sea that are flagged as stranded fields. Tight reservoirs, distant infrastructure, small volumes, and anomalous gas qualities are amongst the main reasons why these resources have not yet been developed. One of these stranded tight gas fields has been successfully developed with the use of a subsea well, horizontal drilling, and hydraulic fracturing.
The Kew structure is a northwest/southeast trending horst straddling licenses 49/4c, 49/4a, 49/5a, and 49/5b of the UK sector approximately 2 km east of the Chiswick field. The primary reservoir objectives are the Carboniferous sandstones of the Caister formation (Westphalian A). This gas field has now been developed with a singlewell that employs a combination of horizontal drilling and multistage hydraulic fracturing to achieve maximum reservoir contact in this low-permeability and interbedded structure.
The absence of data and analogue wells for the design and execution of the fracturing treatments necessitated extended injection tests prior to the execution of the stimulation treatments. To maximize the data acquired from this well, chemical tracers were injected during the stimulation treatments and returns evaluated to assess the flowback of each individual hydraulic fracture. As this was a subsea development well, all the hydraulic fracturing operations had to be performed with the rig in place. Hence, the utmost efficiency of the operations was paramount; otherwise, the economics of the project would be negatively impacted. Innovative techniques of isolation between each fracturing stage were developed to minimize the risk and decrease completion time.
The time of massive gas field discoveries has passed, and smaller developments are proving to be the future, through tying them to existing assets, to boost gas production in the North Sea and extend the life of the existing infrastructure. This challenge was successfully addressed for the Kew field by combining existing technologies and developing new techniques.