The effect of testing conditions on the performance of lost circulation materials: understandable sealing mechanism

Abstract

Lost circulation materials (LCMs) are added to drilling fluids to mitigate lost circulation (LOC) problems. Designing the fluid requires a good understanding of sealing mechanisms and all the parameters affecting the sealing performance. Laboratory testing apparatus is the key concept for LCM evaluation ensuring successful treatment. The high-pressure test cell containing fracture discs is an effective tool among the broadly designed apparatus. A variety of formulations has been developed from the LCM physical properties. Recently, the testing conditions such as the slot wall angles and the fracture disc thickness were found to have significant effects on the evaluation results. However, the effect of the base fluids, fluid density, types of weighting materials and aging conditions has not been addressed. In this study, two different base fluids, water-based fluids and oil-based fluids, were used to compare the base-fluid effect. Drilling fluid density was raised up using barite and/or hematite to investigate the effect of the weight agents. Barite was sieved to study the effect of fine particles on the sealing. Finally, the dynamic aging tests were conducted in LCM-treated WBF using two temperature levels (200 °F and 400 °F) and two aging periods (24 and 72 h). The results showed that the base fluids affected the sealing performance depending on the complex interaction between the solid particles and the fluids. Adding weighting agents tended to improve the seal integrity. Adding proper size of fine particles improved the LCM sealing performance. Aging conditions affected LCM properties depending on the thermal stability of the materials.

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Application of Silicomanganese Fume as a Novel Bridging Material for Water-Based Drilling Fluids

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“…The primary method for testing the clogging effectiveness of lost circulation material is through the use of fracture or slot tests to evaluate LCM bridging in a drilling fluid passing through a fracture [11,23]. Our first test used a modified version of the API standard bridging materials tester.…”

“…This method is ideal under the assumption that LC primarily occurs through pre-existing or drilling-induced fractures. However, research has shown that the specifics of the fracture test setup can drastically affect LCM performance results, and so results depend highly on the chosen conditions [23]. An additional issue with using fracture or slot tests for LCM experiments is that loss zones in geothermal drilling can include fault/shear zones, porous formations, and vugs or cavernous zones [1].…”