Experimental Evaluation of a Novel and a Conventional LCM Pill using a Total Loss Simulating Test Bed

Abstract

Lost circulation is one of major drilling challenges encountered while drilling. The industry uses many LCM products, loss control slurries, specially designed LCM blends, engineered LCM pills and squeezes, etc., to prevent or mitigate lost circulation encountered while drilling. However, the success rate of moderate and severe loss zone treatment using conventional LCM products, loss control slurries and pills is not encouraging, especially for severe and total loss control due to the technical limitations of conventional products, pills and slurries. Hence, there is a continuous need for identification and development of novel products, improved composition of loss control slurries, superior LCM pills, high performance LCM blends, effective and representative test methods, etc., for effective sealing and blocking of loss zones for trouble free and economic drilling operations. This paper provides a comparative evaluation of the sealing and blocking efficiency of a novel LCM pill and a conventional LCM pill used by the industry to combat total loss of circulation. Based on the compositional analyses of the conventional LCM pill used for total loss control, an improved LCM blend was designed by replacing some of the conventional additives by locally developed, better, LCM products to enhance the sealing and blocking efficiency of a poorly consolidated sand bed representing a total loss zone. Typical bentonite mud showed instantaneous loss of all mud within a very short time under 100 psi overbalance pressure and thus indicates that the test beds represented total loss zones. The conventional and the newly engineered LCM pills were tested using the test beds under 100 psi overbalance pressure for comparative evaluation of their sealing and blocking performance. Experimental data, visual observation and images taken while testing clearly demonstrated superior performance for the newly designed novel pill compared to the traditional LCM pill used in controlling total losses. Fluid level drop, deposited cake thickness, invasion depth and the slurry volume lost under 100 psi overbalance pressure indicate better performance for the newly designed LCM pill in sealing and blocking the 20/40 frac compared to the traditionally used pill. The conventional LCM pill contains predominantly imported LCM products. However, the newly designed LCM pill contains predominantly local products. Hence, the superior performance of the re-engineered LCM pill is directly related to the superior performance of the locally developed LCM products.