Wellbore instability is often encountered while drilling Kuwait. Formations consisting of shales and vugular limestone frequently result in total lost circulation leading to hole collapse and differential sticking. In particular, the Ahmadi and Wara shales are notorious for shale sloughing and hole collapse. In one well, the 16-in. upper hole section exposed a range of problematic formations with destabilizing effects such as stuck pipe. On the first attempt to drill the well, the team experienced stuck pipe, leading to several fishing attempts and ultimately requiring a sidetrack.
In the sidetrack hole, the operator elected to use a low-invasion drilling fluid formulated with FLC 2000 technology to control the pressure differential between the formation fluids and the drilling fluid in the wellbore. The drilling fluid design ensured no significant rheological changes would acerbate the equivalent circulating density (ECD) challenges in the narrow drilling window.
For the operator, using a low-invasion drilling fluid formulated with FLC 2000 was the key to successfully drilling the upper hole section through the troublesome formations. The low invasion drilling fluid completely mitigated fluid losses and related hole problems previously experienced in this section, thus delivering value to the operation. The upper hole section was drilled to total depth (TD) without losses or drilling issues.