Equivalent Circulation Density Optimization: Can Flow RegimesSignificantly Affect the Relationship Between Equivalent Circulation Densityand Flow Rate?

摘要

Flow rate(Q)affects many drilling operations and parameters such as equivalent circulation density(ECD),hoisting and lowering the drillstring,and breaking gel strength during circulation.The aim of this work isto understand the relationship between ECD and Q based on flow regimes(e.g.laminar,transitional,andturbulent)to avoid or at least minimize the unwanted consequence during drilling practice.Field data from over 2000 wells drilled in Iraq were collected and analyzed to identify the physicalrelationship between flow regimes and ECD to enhance the drilling rates.After visualizing the wholedataset,a decision was made to break down the data into three parts based on flow regimes(e.g.laminar,transitional,and turbulent).Descriptive data mining techniques were utilized to establish the relationshipbetween flow regimes and ECD.By achieving better control of ECD in the well,not only faster and cheaperoperations are possible,but also safety will be improved.Previous studies and literature showed that flow regimes can tremendously affect ECD.Many studieshave been conducted to understand the relationship between Q and ECD.Nevertheless,the considerationof flow regimes was not implemented in these studies.Inconsistency in the literature results was identified,some concluded the relationship between Q and ECD to be direct,and others showed it to be inverse.Thus,this paper will eliminate this discrepancy in the literature,and it will show that the flow regimes have apivotal role in the relationship between Q and ECD.The results of this paper showed that if the flow regime is laminar,the relationship between ECD andQ is inverse.However,in transitional and turbulent flow regimes,the relationship between ECD and Q isdirect.That is because,in the laminar flow regime,the cutting will fall out of suspension due to low Q,which will cause a cutting bed to be built and decreases ECD.As Q increases(entering the transitionaland turbulent flows)the cutting bed will be eroded,and most of the cuttings will be suspended in the fluidwhich will increase ECD.This study examines and expands the understanding between how the characteristics of flow regimesaffect ECD.Additionally,this paper will eliminate the discrepancy in the literature about this relationshipbetween ECD and Q.