A New Technique for Cementing Liners During Total Losses and Gas Influx Using a Foamed Cementing System

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDrilling through weak formations with total losses, while concurrently controlling gas influx by pumping water down the annulus, is a situation often encountered in the main Northern Oman carbonate oilfields. Consequently cementing the intermediate liner and aiming to achieve total annular coverage for zonal isolation becomes a challenge.This paper describes a technique that has permitted the intermediate liner to be set and fully cemented while experiencing drilling fluid losses and formation flows. Using this technique, the liner packer is set before cementing, thus isolating the gas influx and removing the need to pump in the annulus during the cementation. Then by cementing using a foamed spacer and foamed cement in stages, the fluids can be effectively diverted up the annulus across the loss zones resulting in zonal isolation. For better control of the volumes, and to be able to react to a possible early increase in pressure, the inner-string liner method is used. This cement procedure has been employed on several wells and the cement bond log (CBL) results are very encouraging. Prior to employing this method, cement was only evident around the liner shoe joint. With this new method the total liner length has shown cement coverage from 80-100% with the top of cement (TOC) approaching the previous shoe. In addition this technique has resulted in economic gains by eliminating stage tools and annular packers.The drilling challenges of these fractured wells, the cementing requirements, the design notion of the foamed fluids, the operational execution, and the observed CBL results are all discussed. The value added by using this technique is also demonstrated.