Transient cuttings transport laws through all sections of extended reach well

Key words:  extended reach well  cuttings transport  transient model  actual drilling simulation

Abstract:

Based on the theory of solidliquid flow, a threelayer transient cuttings transport model for all sections of extended well was developed, and the mechanisms of suspension, rolling and sliding of cuttings, the relative velocity between solid and liquid in suspension layer and the effect of drill pipe rotation were all taken into account. The model was used for calculating and stimulating all sections and processes on actual drilling and circulating conditions. The model was solved numerically by SETS method on the basis of the finite volume method theory, and some simulation cases using actual field data were made. The results show that it takes a long time to reach steady state for cutting bed transport because of long inclined wellbore of extended reach well, which leads to a big error by using steady models to calculate cuttings height and annular pressure. Pump rate has a great effect on the speed of cuttings bed formation, that is, the smaller pump rate, the higher steady cuttings bed height and the longer time to reach steady state is. Pump rate also has a deep effect on the speed of cuttings bed erosion, while the original cuttings bed height has little effect on the time of cleaning hole entirely. Finally the calculated results by this model agree well with the results of models obtained by experimental data, which indicates the validity and applicability of this model.