Realtime Open Hole Modeling of Equivalent Circulating Density Using High Frequency Pressure Sensors Across the Drillstring to Maximize Horizontal Drilling Capability

Abstract

Abstract Wired drill pipe (WDP) telemetry that transmits downhole data at 57,600 bits per second has been successful in various applications throughout the world. This paper discusses how monitoring annular pressures at multiple locations along the drillstring helped manage wellbore stability, mitigate risks observed on offset wells, and allow the well to be drilled to total depth (TD). Annular pressure is a direct function of the sum of the frictional forces within a circulating system. These forces primarily depend on external factors including mud density, flow pattern, mud rheology, rate of penetration (ROP) (and resultant cuttings load), hole cleaning, and effective circulating area. Hole overloading often causes excessive equivalent circulation densities (ECD) in horizontal sections due to poor cuttings transport and/or penetration rates at which flow rates cannot remove the drilled cuttings effectively. With traditional methods, ECD is only available from the logging while drilling (LWD) tool in the bottomhole assembly (BHA). Along-string measurement (ASM) tools that provide three-axis vibrations, rotation, temperature, and bore/annular pressure measurements, coupled with the WDP's high-speed real-time network, allows to deliver an accurate understanding of actual annular pressure at different locations in the wellbore. Multiple annular pressure measurements enabled a clearer understanding of hole loading at different locations along the wellbore and the effective cuttings transport and wellbore geometry. Bottoms up circulations in the intermediate section could have reduced circulation times when ECDs stayed low and little ECD reduction was observed. However, additional circulations were carried out when high ECDs were observed to ensure optimal hole cleaning and prevent loss circulation. In the horizontal sections of offset wells, drilling to planned section TD was not achieved due to loss circulation caused by higher ECDs, or hole instability that caused drilling troubles such as stuck pipe. WDP enabled the view of ECDs in an intuitive manner throughout the horizontal section and at the shoe to ensure ECD limits were not exceeded. A scalable equivalent fluid density (EFD) heat map viewer that shows the ECDs throughout the entire drillstring was deployed. True static densities can also be observed because pumping is not required to pulse sensor information to the surface. The viewer greatly enhances the intuitive understanding of the pressures and provides insight into how high weight sweeps affect the wellbore as they travel down the pipe ID and up the annulus.