Filter Cake Porosity and Permeability Profile Along the Horizontal Well and Their Impact on Filter Cake Removal

Abstract

Abstract The filter cake evaluation involves many comprehensive testing and procedures to determine the filter cake properties such as thickness, mineralogy, porosity, permeability, and filtration to design the optimal mud program. For the maximum reservoir contact (MRC) and extended reach (ER) wells where the horizontal section could be 3000 ft or more in those wells, the filter cake formed by the drilling fluid varied from one section to another in the long horizontal section. Therefore, the process of filter cake removal in maximum reservoir contact and extended reach wells should consider the variation in the filter cake properties to achieve an efficient removal process. This research focuses on evaluating the filter cake porosity and permeability profile through the horizontal wells. Moreover, the impact of the filter cake porosity and permeability on the removal process is presented in this work. To achieve the objective of this work, high pressure high temperature (HPHT) fluid loss test was conducted to form the filter cake using actual drilling fluid samples. The compositional and structural analysis of filter cake was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-Ray Fluorescence (XRF). The drilling fluid studied samples were collected from real field rig while drilling the horizontal section. The results showed that the drilling operation was initiated with drilling fluid that was capable of forming a filter cake with low porosity (5 %) and permeability (0.01 md) to minimize the filtration volume. In the first part of the horizontal section the filter cake porosity and permeability increased sharply as more feet of horizontal section drilled. The porosity increased to about 35% and permeability to 0.25 md. After that it remains stable with slight decrease. This growth in the filter cake porosity from 5 to 35% reduced the liquid to solid ratio in the removal process from 28 gm per 500 ml up to 18 gm per ml. The result of this work linked the filter cake properties (thickness, porosity, and mineralogy) in the maximum reservoir contact and extended reach wells with solid to liquid ratio needed to be used in the filter cake removal process. This work will help to reevaluate the filter cake removal and stimulation recipes that were designed based on constant filter cake properties.