Ultrahigh-pressure/high temperature (UHP/HT) wells are very challenging because of the narrow drilling margins, which can cause either losses or an influx. In a field in Malaysia, the pore pressure and fracture gradient were too close to allow conventional drilling, so the managed pressure drilling (MPD) technique was used to drill these wells.Cementing under MPD is a new technique in this area. A technical assessment revealed that there is limitation in the currently used cementing placement simulator in that it cannot simulate the real-time MPD cementing placement. The current hydraulic simulator does not account for automated real-time annulus choking to apply the backpressure and safely place the cement in the annulus. In addition, it does not take into account the downhole viscosity change due to pressure and temperature effects and which is not imposed by the testing protocols from API. To check the effect of the downhole conditions on the fluid viscosities, which will have an effect on the friction pressure in the annulus during the placement, and to reduce the risk during the cementing job, two in-house hydraulic simulators were identified and used to benchmark the currently used simulator results; the design workflow was changed to account for the additional simulations, and the new technique was implemented successfully to cement under MPD conditions.
In Deepwater environment, cementing the surface casing properly is critical to ensure support of the BOP stack, and allow drilling subsequent hole sections. The tophole sections are prone to loss circulation while drilling through the unconsolidated formation and geological fault zones. After switching the well fluid from seawater to heavier pad mud, no drilling fluid returns or very little is observed at sea bed. This scenario makes the cementing operations challenging, as any fluid heavier than seawater may cause lost circulation and compromise the well structural support. Failure to cement the riserless casing properly has been the root cause of many NPT events and one of the top contributors to incidents where the well has been re-spudded. This paper will present the solution to the lost circulation encountered in deepwater wells in Malaysia. The solution uses an engineered dual fibers technology to regain circulation through the thief zones and achieve structural integrity of the riserless casing. The dual fiber technology with optimized solids package and high solid-content cement has been effectively applied to overcome losses in the deepwater riserless section. This technology can also be used on any cementing operation where loss circulation is expected, as a pill or spacer ahead of the cement slurry, given that proper assessment of the well geometry and thorough engineered design have been performed. It was absolutely critical for the operator to get cement returns to sea bed. The dual fibers technology and high solid-content cement were synergically utilized, helping to achieve circulation through the unconsolidated and faulty zones and achieve proper cementation of the surface casing. Circulation of fluids to the sea bed was verified by ROV. The job pressure profile shows that the final displacement pressure was as expected and the top of cement calculated to be at planned depth, despite the loss circulation scenario prior to the cementing operation. The technology presented in this paper provides solution to effectively cement the tophole in deepwater, overcoming lost circulation, helping to achieve structural integrity of the casing that will support the BOP stack and to minimize potential NPT events associated with loss circulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.