Accurate and frequent mud checking is critical to optimum well construction. Proper assessment and management of drilling fluid properties such as density and rheology maintain the primary well control barrier and optimize fluid hydraulics and hole cleaning ability. However, a full mud check while drilling is typically done only once or twice a day. Moreover, the measurements are performed using antiquated equipment, with data quality and reliability that are highly dependent on the practicing mud engineer. Automated, continuous and practical drilling fluid monitoring is therefore needed.

In this paper, we introduce an automated mud skid unit (MSU) which performs continuous drilling fluid sampling and measurements at variable temperatures. The unit is able to provide the non-Newtonian rheological constants characterizing a Yield-Power Law (YPL) fluid as well as the real-time friction factor and critical Reynolds number using a pipe-viscometer measurement approach. Other important fluid properties such as pressurized-density, oil/water ratio and temperature are provided using high-quality in-line sensors. The unit is controlled by a programmable logic controller (PLC) coupled with a Linux operating system for data analysis. The system is able to send real-time data to WITSML data servers and provide detailed mud reports to engineers working either on-site or remotely.

The MSU was deployed in the Permian basin by an independent operator for automated mud monitoring during unconventional shale drilling operations. Rheology, density and phase content measurements were compared with conventional mud reports provided by the on-site mud engineer. Excellent accuracy was observed in mud rheology tests. The pressurized mud-density measurements provided by the MSU proved to be more accurate than non-pressurized mud balance measurements which were affected by mud aeration. Moreover, the MSU provided mud check data 25 times more frequent than those generated by the mud engineer at temperatures of 50°C and 65.5°C. Drilling fluid related issues such as chemical over-treatment as well as sudden changes in mud density, rheology and oil/water ratio were reported immediately to the drilling crew. This paper provides details about the measurement technology as well as the results from the field deployment of the MSU.

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