Key Factors to Consider for Sidetrack Success in Deepwater Operations using Synthetic Based Muds

摘要

The industry is routinely tasked with setting plugs to redirect the drill bit away from the pilot hole to intersect reservoir targets through deviatedrnto horizontal well paths. Well-bore data such as actual bore-hole size throughout length of plug to be set, accurate bottom-hole circulatingrntemperature (BHCT), and drilling fluid properties must be modeled within a short turn-around along with correct bottom-hole assembly (BHA)rnfor successful sidetrack operations. Formation characteristics also play an important role in the cement slurry makeup for placement stability,rnanchoring, and compressive strength development. Detrimental slippage effects or downward plug movement resulting from inclination angle,rnmud and cement density differential and rat-hole volume can lead to cement slurry contamination. These key factors are many timesrnoverlooked and lead to major slurry contamination of plug placement along with many hours of repetitive operations and costly rig time. Settingrnsuccessful sidetrack plugs in Synthetic Based Mud (SBM) environments has also traditionally been more challenging. Special considerationsrnfor spacer/surfactant/mud testing are required to effectively "water-wet" the formation to provide a bondable surface. Technologicalrnimprovements in the testing of spacer and surfactant package formulations provide a more qualitative method for optimum surfactant design tornmaximize mud removal and provide a bonding surface to formation. Shale sensitivity to fresh water fluids must also be considered in bothrnspacer and cement designs to mitigate well-bore instability after drilling operations resume. Deepwater drilling with synthetic based mudrnprojects are increasing globally along with associated rig costs. An unsuccessful "first attempt" to sidetrack can result in significant nonproductiverntime. Specific deepwater case histories will be presented to provide a qualitative feedback on these recognized key processes andrnhow they are performing in deepwater GOM operations.