Study of Cleaning the Horizontal Drains during the Under Balanced Drilling Well in the South Algeria Fields

Many difficulties can occur during the well is being drilled directionally, as cuttings may accumulate either in a bed at hole high angles. It is to highlight that the speed of the cuttings depends on the geometry of the drilling and the amplitude of the ROP. Hole cleaning is still among the most important problems to solve during the drilling operations. The difficulty in removing cuttings bed during drilling appears due to the interaction between drilling mud and the cuttings in cuttings bed leading to the formation of a cuttings bed gel. Inefficient cleaning of the wellbore can cause decrement in the stuck pipe, lost circulation, wellbore instability, high torque and drag, loose control on density, bad quality cement jobs, etc. These problems have a major impact on the economics of the drilling process. Optimization of the hole cleaning during the drilling operations is very important to enhance the drilling rate. In this study, the Rubiandini and Zhou models have been applied to the well for the prediction of the flow rate required to the ascent of cuttings to the day and to prevent the formation of the beds. The results show the critical flow rate value calculated by the Zhou model (544 l/min) to be lower than the in-situ applied flow rate (720 l/min), while for the Rubiandini model, the critical flow is higher (843.16 l/min for the rotary and 783.01 l/min for the sliding). The model of Rubiandini was chosen to make the sensitivity study because the flow rate calculated by this model is close to reality. We highlighted the effect of major drilling parameters, such as ROP, mud rheology, specific gravity of fluid, density of cuttings, dimension of cuttings, flow rate, flow regime, androtating speed of the drill stringon cuttings transport efficiency are analysed.