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Loss of circulation is a major source of non-productive time (NPT) in the drilling operations worldwide. Different types of loss circulation materials (LCM) have been developed and used to minimize mud losses and mitigate the associated problems. Before a new type of LCM is deployed in the field, it needs to go under extensive laboratory testing with simulated downhole conditions to measure its performance. Therefore, a number of LCM testing methods have been introduced to test the effectiveness of those materials with the ability to have a high-temperature high-pressure (HTHP) environment. Review of published information indicates different research studies with emphasis on various critical factors to come up with different testing methods and apparatus to evaluate the performance of LCM's under a set of experimental conditions. Some testing methods have the capability of doing the testing at high temperature and/or high pressure while others are built of transparent materials and have the advantage of allowing the researcher to monitor and visualize the invasion depth, fluid level drop, deposited thickness, plugging mechanism…etc. In addition, depending on the size of the apparatus and simulated openings, which frequently are slotted disks, each apparatus has a maximum limit in terms of the particle size of LCM it can handle. Practical considerations should be taken into account when designing a testing cell such as the size of the cell, simplicity and portability, data acquisition system, etc. Large testing cells require large quantities of LCM pills mixed with drilling fluids and, therefore, requiring to mix large quantities of drilling fluids for each test run. Hence, this test should be conducted for selective studies of LCM performance. Cleaning of the test apparatus after each test is an important factor as well to be considered in the design to make it more user-friendly and avoid any detrimental impact on subsequent test results. |
