ECD Management Toolbox for Floating Drilling Units

Abstract

This paper presents ongoing work as well as plans and ideas for future development of a toolbox of managed pressure drilling systems that solves major challenges when drilling in both mid-and deep waters. The toolbox contains three applications based on field proven Controlled Mud Level (CML) technology. Additional benefits can be achieved by combining controlled mud level technology with other technology elements such as a fast closing annular or a sealing element in the riser, usually referred to as a rotating control device (RCD).The first application is called CML. A subsea pump module (SPM) is used to pump the mud returns to surface in a separate mud return line (MRL). The SPM is used to regulate and manage the bottomhole pressure by adjusting the mud level in the riser. High bottomhole pressure or Equivalent Circulating Density (ECD) due to friction and other effects can be avoided by reducing the mud level in the riser accordingly. One of the objectives with this technology is to avoid or reduce losses both during drilling and other operations such as cementing.In the second application called ECD-Management, CML is combined with a fast closing annular installed in the riser just above the SPM. This enables extending the operating envelope of the technology to a point where loss of circulating capability could potentially cause an underbalance scenario in the well. The hydrostatic pressure from the drill string or MRL can be trapped within a few seconds by closing the fast closing annular element, e.g. on unplanned rig pump stops or formation pack off situations. A second annular will also be installed to be used during connections in order to save time filling up the riser to compensate for the ECD effect (friction losses in the annulus).The third application in the toolbox is called ECD-Control. Here a subsea RCD or a sealing element is installed in the riser and the SPM can then be used to manipulate the pressure below the RCD to compensate for ECD variations. The riser is always topped up with mud and hydrostatic overbalance is maintained.The paper will present simulation results comparing the different technologies and address benefits and challenges with the different methods.

Analysis of Field Trial Well Control Results with a Dual Gradient Drilling System

“…The tail of the gas was easier to handle and did not require much manipulation of the choke. 1 Proportional Integral controllers (PI-controllers) have two tuning parameters, a proportional constant and an integral time constant, which can be altered to obtain a desired performance. The process of finding these parameters is referred to as tuning, and the resulting parameters are referred to as the tuning of the controller.…”

“…When circulating out a gas kick, the BOP is closed, BV is open and RIV 1 is closed. More details on CML and other managed pressure drilling technologies for floaters are presented in [1]. When applying DGD, heavier than conventional mud weights may be used and consequently hole depth / casing points maybe extended beyond what would be possible with a single gradient back to surface mud system.…”

Real-Time Detection of Karstification Hazards While Drilling in Carbonates

“…However, for PMCD there is an operational necessity for additional equipment installation on the rig site such as the Rotational Controlled Device (RCD) [15]. Additionally, a significant volume of sacrificial fluid is required for drilling, which makes this technique inapplicable in some regions.…”

Automated Pattern Recognition in Real-Time Drilling Data for Early Karst Detection

“…The use of Pressurized Mud Cap Drilling (PMCD), when a sacrificial fluid is pumped through the bit nozzles to fill karsts, is today the most common solution to dealing with total losses in carbonates [13][14][15]. However, rigs are not always equipped with a Rotational Control De-vice (RCD) [16] required for PMCD and a significant volume of sacrificial drilling fluid may not be readily available.…”