Use of Foam Cement to Prevent Shallow Water Flow on Three Wells in Norwegian Waters

Abstract

In certain areas of the Norwegian waters, shallow pressurized sands containing either gas or water occasionally create problems during drilling and surface casing installation. In 2018, an operator drilled three wells in the Norwegian waters with such special challenges. In this case the challenge was water flow but not gas. The NORSOK D010 shallow gas flow potential was classified as zero. Each of the wells had a shallow water flow challenge in an over-pressured sand that normally would require setting a shallow 20-in. surface casing and a riser installation before passing the zone to enable controlling the pressure on the sands using weighted drilling fluid; also requiring a 17-in. liner installation to cover the sand before further drilling. If the surface casing could be set deep enough to cover the over-pressurized sands, substantial savings could be obtained on each well by eliminating the need for an additional section and installation of an extra liner or casing. Furthermore, a deeper-set surface casing would reduce the risk of not obtaining an adequate leak-off test below the shoe. A deep-set surface casing would also allow for down-scaling the well from 20-in. to 13-3/8-in. surface casing. A riserless drilling fluid return system allows for controlling the pressure while drilling, but this has to be turned off during cementing as cement is expected in returns. The use of conventional cement systems would potentially put the well in under-balance for a substantial period of time and consequently potentially result in a water-flow situation requiring a re-spud, as has been the case for a reference well in the area in which substantial downtime was experienced due to water flow after cementing the surface casing. The solution was a riserless drilling fluid return system during drilling, followed by a tailored cement solution. A tailored spacer and foam cement system were deployed; the short transition time of the cement and the inherent compressibility of foams both reduced the exposure time in under-balance. The solution was successfully deployed on all three wells with no flow observed post placement. This paper will detail this successful case study.

Foamed Cement Applications in Oil Industry Based on Field Experience: A Comprehensive Review

“…There was also no water flow observed after the treatment, which is attributed to the decrease in the transition time for the foam cement system and its high compressibility, which shorten the exposure time in underbalance. 74 6.5. Foam Cementing Cyclic-Steam and HPHT Producing Wells.…”

“…The job was successful in all the three wells with full cement return to the seabed. There was also no water flow observed after the treatment, which is attributed to the decrease in the transition time for the foam cement system and its high compressibility, which shorten the exposure time in underbalance …”

Quantitative Analysis of the Stability of a Mud-Return Circulation System in a Riserless Mud-Recovery Drilling System

“…In Norway, RMR was utilized in three wells with shallow water flow issues. It led to complete subsea mud recovery and prevented the shallow flow [24].…”

Displacement Flow of Compressible Non-Newtonian Fluids in Annular Geometries for Well Cementing Applications

“…, 𝜑) = { 𝜏 𝑦 (𝜑) |𝛾̇| + 𝐾(𝜑). |𝛾| 𝑛−1 , 𝑖𝑓 𝜏 > 𝜏 𝑦 (𝜑) ∞, 𝑖𝑓 𝜏 < 𝜏 𝑦 (𝜑)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) Where the parameters K and 𝜏 𝑦 relate to the 3-parameter base fluid Herschel-Bulkley model (𝐾 0 , 𝜏 𝑦,0 , n) according to Eq. 3-20(Ducloué, 201), where 𝜑 is the gas volumetric fraction as Eq.…”