EFFECTS OF SAW-DUST AND CORN-COBS ADDITIVES AS LOST CIRCULATION MATERIALS IN WATER-BASED MUD
Abstract
ABSTRACT
Lost circulation is a major problem encountered in the drilling process and is defined as the unwanted loss of the whole or a portion of drilling mud into a formation. This occurrence can lead to some severe problems, including pipe sticking, formation damage, blowout, and wellbore instability, leading to an increase in time and cost of the operation. Therefore, it is a common practice in the industry to try to have the least amount of lost circulation. This issue is influenced by various parameters such as the type and weight of drilling fluid and its rheological properties, pump pressure, and formation pore pressure. Drilling fluid losses into fractured or highly permeable formations is a major challenge. Lost circulation treatments are widely applied to mitigate the losses; however, the effectiveness of these treatments is affected by different physical properties of the used lost circulation materials (LCM). This project presents an experimental investigation to study the effect of saw-dust and corn-cobs as lost circulation materials, concentration and mud cake thickness on the formed seal integrity. The overall objective of this study is to address the effectiveness of saw-dust and corn-cobs as LCM treatments in sealing fractured formations, with specific application to the Niger Delta Basin. The composite of the two materials at 850 microns was used to formulate a water base mud system and evaluate its effectiveness against calcium carbonate water base mud system. The composite produced thicker mud cake that is suitable for sealing porous or fractured formation. Examination of the formed mud cake thickness under an optical microscope revealed that this was due to the fine shape of the composite additives as well as its ability to deform under elevated pressure. Based on the results, it has been found that to effectively seal fractures using granulated saw-dust and corn-cobs treatments, A 850 microns size was required.
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