Record-Breaking Reservoir Drilling and Openhole Gravel Packing With Cesium Formate Fluids in a High-Pressure, Marginal Mud Window Environment at Martin Linge

Abstract

This paper describes how high-density cesium/potassium (Cs/K) formate fluids were successfully utilised from reservoir drilling to upper completion installation in five productive Martin Linge high-rate gas wells. Four wells were completed with openhole gravel pack and one with standalone sand screens. The gravel packing operation marks what is considered to be the highest density carrier fluid openhole gravel pack successfully completed worldwide, with SG 2.06. A complex operation under near-high-pressure/high-temperature (HP/HT) conditions, including managed pressure drilling (MPD), overbalanced screen running and openhole gravel packing, was simplified by utilising the same fluid throughout the operation. Cs/K formate reservoir drilling fluid and screen-running fluid were designed with biopolymeric additives and minimal calcium carbonate bridging particles. Clear Cs/K formate brine (i.e., without biopolymeric additives and particles) was chosen as gravel pack carrier fluid. The use of Cs/K formate fluids for all stages of the operation reduced the complexity of transitioning between the operational stages. In addition, the reservoir was only exposed to one filtrate without application of damaging weighting solids. The drilling fluid contributed to successful MPD and delivered wells with very good hole quality in the reservoir, which consisted of interbedded sandstone, coal stringers and shale. The shale stabilising properties of concentrated formate brine–based fluids provided acceptable conditions for extended openhole time and allowed additional logging runs, including pore pressure measurements, under near-HP/HT conditions before running the screens. One bottom-up cleanout was conducted before the screen-running fluid was circulated in and the screens installed. The spurt and seepage losses were low throughout the drilling and screen running phases. No breaker treatment was required in any of the wells. All wells have proven to have good initial productivity and high well productive efficiency as expected. The record-breaking openhole gravel pack operations performed with the high fluid densities required in Equinor's Martin Linge field have set a new standard for completing in challenging high-pressure environments.