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Complex structural wells are widely used in the development of marine oilfield, old oilfield and low permeable
oilfield. However, poor hole cleaning is often occurred in the highly-deviated sections and horizontal sections of the
complex structural wells, which affects rate of penetration and downhole safety.
The methods to study cuttings transport can be normally divided into four types: 1) experimental observations, 2) CFD
simulations, 3) theoretical correlations and models and 4) field tests. Experimental observations and CFD simulations are
mainly used to analyze the effects of different parameters on hole cleaning and obtain some valuable data. Theoretical
models and correlations are mainly applied to calculate cuttings bed height, critical velocity and etc to provide the
guidance for the design of hydraulic parameters. The accuracy of the first three types are checked by field tests. In this
paper, the effects of flow rate, inclination, mud rheology, drillpipe rotation and other factors on hole cleaning, and some
typical correlations and models were briefly reviewed before 2000 years, and some new research findings were detailedly
addressed. In addition, CFD simulations also were introduced.
Although major improvements have been achieved in the past several decades, building a comprehensive and proven
model requires much more experimental researches, CFD simulations, in-depth theoretic studies and field tests due to the
complexity of cuttings transport under multi-factor interactions.