Directional drilling makes it possible to drill multilateral wells into different parts of a reservoir from a single wellbore. Many directional wells are drilled to reach reservoirs inaccessible from a point directly above because of surface obstacles or geologic obstruction. Wellbore sidetrack drilling operations with hard cement plugs have been used for years. Placing cement plug in the borehole and allowing the cement to develop high compressive strength perform sidetracking technique. The hardened cement plug when drilled deflects the bit away from the current borehole, starting another open hole section. Conventional cement formulations for sidetrack kickoffs usually fail when the ROP (Rate of Penetration) for the cement plugs is much more than the ROP in the formation Sidetracking failures, in building up kickoff angles, results in operational delays and cost overrun. High sonic compressive strength cement system with slow ROP should be designed and developed specifically for side tracking operations. A rate of penetration device was used to optimize cement formulations to determine the ROP through cement plugs. Different chemicals for building up sonic compressive strength were evaluated. Special types of cements were designed and evaluated for possible use for sidetrack kick-off plugs. The effect of inert particles on the sonic compressive strength and ROP were investigated. The cement slurry was cured for 24 hours in the Ultrasonic cell at bottom hole static temperatures of 260-290oF and a bottom hole pressure of 4,700 psi to represent gas well conditions and 200-250oF and 2,200 psi for oil wells. The outcome of this work was cement formulations with high potential (high sonic compressive strength and slow ROP) that can be used to drill horizontal and multilateral wells.
展开▼
