Application of a Real Time Mud Density and Rheology Monitoring System to Enhance Drilling in High Pressure High Temperature Gas Wells with MPD Systems
Authors: Ombe Ebikebena M. , Elyas Odai A. , Abdul Qader Tamer , Mehdi Mohammed 
Published: January 2020

The monitoring and management of drilling fluid properties while drilling oil and gas wells is very important, especially when drilling in oil and gas fields where highly pressurized formations with narrow pore pressure/ fracture gradient windows are encountered. The most critical of these properties include the drilling fluid density or mud weight (MW) and the rheological properties i.e., plastic viscosity (PV) and yield point (YP). Changes in these properties are usually the first indication of downhole problems and thus the need to constantly monitor them cannot be overemphasized. While drilling, much effort is put into having a tight control on these drilling fluid properties. The conventional approach to monitoring drilling fluid properties in drilling operations involves the drilling fluid engineer carrying out routine tests on mud samples, taken from the active mud system. These tests include MW checks and funnel viscosity tests to check for any changes in MW and/or rheological properties. If any changes or deviations are detected in these tests, more detailed tests are subsequently carried out on the mud samples to identify which of the other properties have changed and the possible causes. This is a time-consuming process and by the time the causes are identified, the resulting downhole problems would have deteriorated to cause major challenges like stuck-pipe, lost circulation or well control. This issue requires an automated & continuous system to measure the drilling fluid density and rheological properties and monitor their trends. The Density Rheology Monitoring System (DRMS) is an innovative real-time solution that has been developed to gives real time values for the MW and rheological properties of the drilling fluid in the active system, thus allowing for the quick detection any changes in these properties and the timely response to them. This is a far more effective approach than the conventional mud checks, since it reduces the lag time between the actual changes in drilling fluid properties and the identification for these changes.

The DRMS consists of the Density Rheology Unit (DRU) linked to a Monitoring System (MS). The DRU measures laboratory-grade density and six-speed rheology via rapid sampling at the collection point, usually located at the flow line after the shakers and in the active mud tank. The density measurements are taken once every 90 seconds, while the rheology measurements are taken once every 20 minutes. The MS presents these values digitally and plots the trends graphically so that changes can be quickly and easily identified. This allows for the early detection and mitigation of the causative downhole problems, as well as proper management of the drilling fluid properties and overall quality.

This paper discusses how the DRMS is used for real-time monitoring of the drilling fluid MW and the rheological properties, while drilling with a Managed Pressure Drilling (MPD) system through high-pressured formations. It will highlight how the DRMS allowed for early detection of the drilling fluid deterioration and prevalent downhole problems e.g. lost circulation and well control. This application allowed for quick and effective actions to be taken to restore the drilling fluid quality, thus preventing any downhole problems and allowing for the successful drilling of these high-pressure formations. The paper will also highlight how data from the DRMS can be used for real time optimization of downhole equivalent circulating density (ECD) while drilling with the MPD system.