New Casing Valve in a Deep-Well Sour Environment
Authors: Carpenter Chris 
Published: February 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 16936, ’New 10¾-in. High-Pressure/High-Temperature Casing Valve Successfully Applied in a Deep-Well Sour Environment,’ by Paolo Ferrara and Claudio Molaschi, Eni E&P; Bill Menard, Weatherford; and Francesca Rinaldi, Eni E&P, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed. Copyright 2013 International Petroleum Technology Conference. Reproduced by permission.

To complement managed-pressure-drilling systems, the possibility of introducing new safety barriers directly into the well has been considered. Among these barriers, a new casing valve (CV) with surface control lines, rated for high-pressure/high-temperature and sour environments, has been developed. This paper describes the first application of the 10¾-in. CV in a deep-well sour environment.

Background

In 2011, a new 10¾-in. 97.1-lbm/ft CV was installed successfully in a well at a measured depth (MD) of 3675 m and a 50° inclination in a hydrogen sulfide (H2S) environment of up to 18%. The well profile was implemented with an S-shaped trajectory featuring a pseudocatenary approach. The CV was set as a permanent installation in 10¾-in. production casing approximately 400 m inside the preceding 13?-in.-casing shoe

(Fig. 1). CV position details are as follows:

CV setting depth: 3675-m MD [2899-m total vertical depth (TVD)]

13?-in.-casing shoe: 4075-m MD (3155-m TVD)

10¾-in.-casing shoe: 4947-m MD (3837-m TVD)

CV Construction and Operation

The CV is a full-bore and surface-controllable flapper-type valve that can be installed as an integral part of a casing string and can serve as an additional downhole barrier to seal the wellbore pressure/fluid below it. A CV can be used to avoid the need for snubbing operations, or the need to kill the well in order to trip the drillstring and install completion assemblies during near-balanced and underbalanced operations. It represents an additional downhole mechanical barrier because it can be inflow tested, for instance with a lubricator valve installed with the casing. The valve surface control is achieved by a two-way armored control line that runs from the valve to the surface control panel and hydraulicpower unit. To open the valve, pressure is applied one way, and to close the valve, it is applied the other way. The presence of the control lines requires modification and penetration of wellheads.

The design of the CV allows the passage of the bottomhole assembly (BHA) and all downhole equipment when in the open position. When tripping out of the hole, the string is tripped out until the bit is above the CV, which is then closed and the casing annulus pressure above the CV is eventually bled off. The drillstring can then be tripped out of the well without the use of a snubbing unit and at conventional tripping speeds, thus reducing rig-time requirements and providing improved personnel safety.

The CV can also be used to trip in the hole. The drillstring is tripped back into the well until the bit is immediately above the CV; the annulus pressure can be equalized, the CV is opened, and the drillstring is run in to continue drilling operations.