Drilling fluid severe losses through highly fractured or highly permeable formations is considered as one of the most critical problems while drilling through these problematic zones, which can result in a costly non-productive time (NPT), and might lead to catastrophic well control issue in worst-case scenarios. The effectiveness of LCM treatments is often evaluated in the lab prior to field application. The main objective of this paper is to present the development of an in-house testing apparatus that simulates and evaluate the effectiveness of a proprietary LCM pill in curing losses through highly permeable formation.
A testing apparatus was developed in-house to simulate and evaluate the effectiveness of a proprietary LCM pill in curing losses through highly permeable formation. The apparatus consists of a transparent testing cell, which simulates the filtration medium, to visualize the losses profile through a gravel bed with porosity up to 40%. Four different blends at different concentrations (between 9 – 17 lb/bbl) were mixed in a 7% bentonite mud and evaluated at 100 psi using the newly developed apparatus. The depths of fluid invasion, the fluid loss, and the filter cake thickness were measured accordingly to evaluate the effectiveness of the developed LCM pill.
The testing apparatus was successfully built, pressure tested up to 150 psi, and used to evaluate the developed LCM pills. The results showed that the developed blends were able to plug and seal the highly permeable filtration medium effectively. The evaluated LCM pills resulted in a depth of invasion ranging between 44 – 96 % of the total length of the filtration medium and a filtrate volume of less than 5 ml/30 min depending on the concentration of the additives used. The filter cake thicknesses ranged between 0.16 – 1.37 inches, where the best blend resulted in the thickest filter cake.
Based on the results, the blends showed a superior performance in terms of curing the losses in a short period of time, which in turns will contribute towards reducing the associated NPT and further unwanted consequences.