Evaluation of filter cake mineralogy in a horizontal well

Filter cake occurs intentionally during the drilling operations to prevent fluid losses to the formation and to allow good circulation for drilling fluids to the surface and is known to depend on a well-designed drilling mud fluids and additives. The filter cake must allow for minimum filtration and solid invasions to the formation and must also withstand high differential overbalance pressures. This work evaluated the filter cake properties such as filter cake thickness and mineralogy in the horizontal section of well during drilling sandstone formation.;This study focuses on the chemical composition of filter cake formed in the horizontal section, from its tip to its toe. High pressure fluid loss test were performed using real drilling fluid samples from the field which were collected during drilling of a horizontal section in a sandstone formation. The mineralogy of the external filter cake formed by fluid loss test is described in detail using both Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). CT scan also was used to evaluate the internal solids invasion.;The results show that for long horizontal sections in sandstone formations, the composition of the filter cake is not constant from its toe to heal and the sand percentage increases up to 50%. Since the small drilled solids, those are not properly removed, will be mixed with the drilling fluid during circulation and degrade the performance of the drilling fluid as well as become an integral part of the fabric of the filter cake. Moreover, this study investigates that as more feet of horizontal section of sandstone formation is drilled the sand percentage increases as well as the cake thickness increases. This internal invasion becomes critical when the sand percentage reaches higher than 40%, because the solids will invade into deeper zones.