Determination of Safe Mud Density for Soft Mudstone Formation in KI11-2 Structure

Abstract:

Well KL11-2-1 is a wildcat well that located in KL11-2 structure, where sticking happened in position Ⅳ of Shahejie group, the accident happened again in the same position while drilling the sidetracked well KL11-2-1S on the base of Well KL11-2-1, Analysis reveals that the lithology in the place of the two sticking accidents is rufous mudstone. This kind of mudstone has the character of strong plasticity, swelling with water and very soft, the main reason of sticking is that the mud column pressure can not balance the soft mudstone creep pressure and the creep lead to borehole shrinkage. For solve the problem during drilling in this structure, this paper according to the characteristics of mudstone in this structure builted proper creep equation and creep mechanical computation module of soft mudstone, applied FLAC3D software to compute and analyze the creep characteristics, obtain borehole shrinkage rate plate with different depth and mud density, and the safe mud density that can inhibit the creep which lead to borehole shrinkage is given, the results show that for prevent the sticking accident occurred the safe mud density of the two sticking points of the well KL11-2-1/1S is 1.73 g/cm3 and 1.75 g/cm3.the results make significant sense in guiding the subsequent drill of the structure.

• Periodical: Advanced Materials Research (Volumes 455-456)
• Pages: 1601-1605
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.455-456.1601
• Online since: January 2012
• Authors: Zhong Hui Li, Yi Shan Lou, Liang Zhu, Chun Yang Zhang
• Keywords: Creep, KL11-2 Structure, Safe Mud Density, Soft Mudstone, Sticking

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