# A Nodal Analysis Based Monitoring of an Electric Submersible Pump Operation in Multiphase Flow
## 5 Results  
### Results of Nodal Analysis Simulation  
The effects of an increasing GVF on ESP performance were evaluated at both the intake node (nodal point A, Figure 1) and the discharge node (nodal point B, Figure 1). The intake node evaluation yielded the operating PIP given by the intersection of the TPR-ESP and IPR curves. Similarly, evaluation at the discharge node yielded the operating Pd given by the intersection of the TPR and IPR + ESP curves.  
Case one shows the nodal analysis of GVF variation when an ESP is deployed in a dead well. Thus, the IPR and TPR-ESP curves do not intersect when GVF = 0.99 (the ESP is not operating). Figure 8a shows that the TPR-ESP curve moves upward when the GVF increases; Figure 8b shows that the operating intake nodal point is shifted to the left of the IPR curve, thereby increasing PIP and reducing Q\({}_{0}\). Similarly, Figure 8c shows that the IPR + ESP curve moves downward when the GVF increases; Figure 8d shows that the discharge nodal point shifts to the left of the minimum point on the TPR curve. Because of these changes, both P\({}_{\text{d}}\) and Q\({}_{0}\) decrease. The pressure difference (\(\Delta\)P\({}_{\text{pump}}\)) between _PIP_ and _P\({}_{d}\)_ gradually decreases as GVF increases. Thus, ESP performance and oil production both decrease.  
Case two shows the nodal analysis of GVF changes when an ESP is deployed in a naturally flowing well; the TPR-ESP and IPR curves intersect when the GVF is 0.99, although the ESP is not operating. Similar to case one, an increase in the GVF degrades ESP performance, thereby increasing the TPR curve (Figure 9a,b) and decreasing the IPR curve (Figure 9a,c). Q\({}_{\text{min}}\) develops at GVF = 0.69 for a multiphase well (Figure 9b,d). Thus, the ESP operation is abnormal when GVF exceeds 0.69. However, for a single-phase well, ESP operation is normal despite a GVF of 0.99 (Figure 9a,c) because all intersection points of the TPR and IPR curves are within the reference threshold normal ranges.  
The changes in the TPR and IPR curves when the GVF increases can be interpreted over three phases:  
Phase I: Stable ESP operation. In this phase, the TPR and IPR curves intersect within the normal operating ranges, irrespective of the ESP operating point. The intersections (TPR-ESP and IPR curves or IPR + ESP and TPR curves) are stabilized within the threshold, normal operating ranges. For example, at a fixed GOR = 100 SCF/STB and W\({}_{\text{cut}}\) = 0, the intersection points remain in the normal ranges until GVF attains 0.79 (dead well, Figure 8a,c). When GOR = 2218 SCF/STB and W\({}_{\text{cut}}\) = 92.9%, the intersection points remain in the normal ranges until GVF exceeds 0.37 (dead well, Figure 8b,d).  
Phase II: Abnormal operation. The TPR and IPR curves intersect outside the normal threshold ranges during this phase. Despite the abnormality, ESP operation continues; the differential pressure becomes low. At a fixed GOR = 100 SCF/STB and a W\({}_{\text{cut}}\) = 0, operation becomes abnormal when the GVF exceeds 0.79 (dead well, Figure 8a,c). When GOR = 2218 SCF/STB and W\({}_{\text{cut}}\) = 92.9%, abnormal operation is observed when the GVF exceeds 0.37 (dead well, Figure 8b,d) or 0.69 (naturally flowing well, Figure 9b,d).  
Phase III: The ESP is shut down, and the well operates under natural flow conditions. This phase comprises two parts, depending on the condition of the well prior to ESP installation. For a dead well, Phase III is associated with zero production. Conversely, when the well previously flowed naturally, it shifts to its natural operating point when this phase initiates. The measured PIP and P\({}_{\text{d}}\) are very similar to the operating bottomhole pressure of the (formerly) naturally flowing well; this is the ESP shutdown condition. When the ESP shuts down, the TPR-ESP and IPR + ESP curves coincide with the curves of the natural well (at a GVF = 0.99, Figures 8 and 9).