Prediction and Analysis of Extreme Extension Length of Horizontal Well Based on Hole Cleaning Degree

Horizontal well is of great significance to the development of unconventional oil and gas resources. Considering the wellbore cleaning and pressure system safety, a model is established based on the influence of cuttings on the hydrostatic column pressure, horizontal annular pressure drop and annular geometrical shape to provide a specific extreme horizontal extension length (EHEL). This model is controlled by minimum cutting-carry pump rate, bottomhole pressure, circulation pressure loss and drilling pump pressure. The solving process and method is also given to realize the prediction of any horizontal well. The analysis shows that there is a limit to EHEL in order to maintain the wellbore cleaning degree and effective cutting transport. The limiting factors to EHEL change from formation fracture pressure and bottomhole pressure to total circulation pressure loss and pump pressure as minimum cutting-carry pump rate increases. The EHEL increases and then keeps constant as acceptable cutting bed height increases. Higher drilling fluid density is adverse to EHEL although it can reduces minimum cutting-carry pump rate. Lower consistency index and flow behavior can increase EHEL because it can reduce minimum cutting-carry pump rate and circulation pressure drop. The carve of EHEL with rate of penetration is divided into three sections, and the rate of penetration should remain in slowdown section to balance drilling cost and EHEL.