During well drilling operations, the invasion of the porous media around the wellbore by a certain quantity of drilling fluid components is likely to happen to build a stable mudcake. For a horizontal open hole well, the mud cake is kept during drilling and completion operations giving stability to the borehole. Because the drilling fluid is heavier than the formation fluids, solid particles and fluid components are pushed into the formation establishing a filtration process. At some point, the mud cake must be removed and a clean up procedure is done. For production wells, the majority of the mud cake and invaded components are removed with the well production and the resulting skins are usually acceptable without any secondary treatment. However, for injection wells, such removal is always a problem and special treatments are needed. The success of such treatments is based on the knowledge of the invasion profile and their composition. Therefore, a better characterization of the invasion profile could improve substantially the clean up procedures and the treatment selection.
In this first result the aim of study is to address this problem an experimental procedure was developed to identify and characterize the profile of drilling fluid invasion. This technique used the X-Ray Fluorescence Beam line (XRF) from the Synchrotron Light at the Brazilian Synchrotron Light National Laboratory (LNLS) in Campinas, São Paulo State, Brazil figure 1. This methodology allowed the determination of the invasion profile in synthetic unconsolidated sandstones similar in composition to the reservoir rocks.
Along with the invasion profile, μ-SRXRF analysis was used to map and identify drilling fluid components that may have invaded the core. The identification of these components provided information to differentiate and identify carbonates and polymers in terms of concentration and penetration.