The onshore Tintea field in Romania is notorious when it comes to drilling shale intervals of Pontian and Meotian formations. Hole instability in these stressed shales poses a major problem and has resulted in several stuck pipe and lost BHAs over the years. Selection of drilling fluid, either water based mud or synthetic oil based mud, does not help to resolve the situation as similar problems have been encountered using either mud system.
Recently, a drilling mud additive, used successfully for promoting hole stability in wells drilled in the North Sea was proposed to be used in the Tintea field. This additive which is primarily a borehole stabilizing and lost circulation material consisting of micronized organic cellulose fibers also helps to stabilize the stressed shale formations where
micro-fractures exist by effectively bridging them off.
Hole remained stable without any excessive drag, over-pull, or stuck tendencies. Following this successful field trial, it is now the product of choice whenever hole stability issues are encountered in Tintea field. It was used in two subsequent wells to the trial well and delivered the same result. The Company’s drilling fluids specialists working closely with the Service Providers have perfected the combination of using these fibers together with calcium carbonate in the appropriate concentration and have delivered wells within time and budget.