Abstract
Extended Reach Drilling (ERD) wells drilled nowadays can reach a step-out of 10 km (33,000 ft) and thus present many drilling challenges, including torque and drag, hole cleaning, wellbore stability, equivalent circulating density (ECD) management, lost circulation management, just to name a few. These challenges can severely limit the desired well depth or increase the operation time, particularly in deepwater environment. A new synthetic-based flat rheology drilling fluid (SBM) with new emulsifier and rheology modifier package has been designed for narrow margin ERD wells.
This newly developed flat-rheology SBM utilizes a novel, single emulsifier to simplify fluid formulation, improve emulsion stability, enhance thermal stability, and provide surface wetting and fluid lubricity. This allows the system to be formulated for any ERD applications with mud weights up to 18.0 lb/gal and temperatures up to 350°F. In addition, the system uses a new rheology modifier that provides temperature-independent rheology profile for better hole cleaning, barite suspension, ECD management and lost circulation control.
A recent field trial conducted in deepwater GoM indicated that the new system is easy to handle and provides good fluid performance in terms of drilling rate, ECD management, lost circulation control and hole cleaning. The SBM at one time was severely contaminated due to salt water flow but the fluid held together without any problems. Similar results on drilling performance were observed with another onshore field trial that used a non-synthetic-based fluid.
This article describes the new flat-rheology SBM system with examples showing typical mud formulations, fluid properties, barite sag performance data, field test data and computer hydraulics simulation of ECD impacts.
