Review and Analysis of Cuttings Transport in Complex Structural Wells

Complex structural wells are widely used in the development of marine oilfields, old oilfield sand low permeable oilfields. However, poor hole cleaning often occurred in the highly-deviated sections and horizontal sections of the complex structural wells, which affects rate of penetration, cementing quality and downhole safety. It is advisable to study the behavior of cuttings transport under different conditions. In general, experimental observations and CFD simulations are main methods to analyze the effects of cutting parameters, fluid parameters and operational parameters on hole cleaning. The correlations and models are applied to predict the number of cuttings and the critical velocity in the annulus. In this paper, an analysis of key parameters is conducted on cuttings transport, the existing problems and characteristics of these correlations and models are summarized,, and different removal methods of annular cuttings and future research needs are discussed. Although major improvements have been achieved in the past several decades, how to accurately predict the cuttings bed height, critical velocity and other key parameters, and to effectively solve the poor hole cleaning still is a difficulty challenge. Therefore, more research will be conducted to further understand cuttings transport mechanism in multi-factors coupling and complex wellbore conditions.