Publications

Pressure window analysis can be used for aerated drilling applications in the field during drilling in order to improve performance. Geothermal wells naturally consist of fractures that will tend to affect circulation process and drilling success. Aerated drilling is utilized for circulation performance enhancement which will carry cuttings up to the surface as well as new surface or cutting pocket. The volume of injection of aerated mud should be appropriate, therefore pressure window analysis is needed. Other strategies such as backside pumping, cutting pocket, pressure while drilling utilization and lag time calculation will have a significant impact on the success of application and as important learning notes for the next drilling process. The observation of case studies from several fields showed a positive trend. In the first field, two sections had better borehole cleaning indicated by a high transport ratio. The next field has utilized pressure window corrected by Pressure While Drilling tool reading to get an optimal number of aerated mud injection in penetrating the first feed zone and used backside pumping in the annulus column to control undesirable kick thus following feed zone can be achieved as well. The result of pressure window analysis and aerated drilling strategies are considered to have a significant effect for reducing geothermal drilling risk, both in terms of cost and productivity. Keywords: Aerated Drilling, Fracture Reservoir, Pressure Window. INTRODUCTION Optimization of drilling costs has a significant impact in geothermal field development (Figure 1) because 50% of total development cost is allocated for drilling (Teodoriu, 2001). The challenges of geothermal drilling implementation iclude loss of circulation in high temperature zones and stuck pipe especially in the reservoir (Hole, 2006) and these problems will also interfere with mud circulation system as well. In addition, loss circulation is recorded to absorb 20% of the total drilling cost (Lin, 1982) which means it is equal to 5-10% of total field development cost. In addition, there is data that shows that 17.9% of non-productive time (NPT) is caused by stuck pipe (Figure 2) which the writers can predict will result in additional high costs. Nowadays, the solution to these problems may lie in aerated drilling utilization because the main purpose of this method is enhancement of mud circulation. However, the question is how much is the appropriate injection rate that can make it flow to the surface. Therefore, a pressure window graph will give a span line to be used as a reference for this injection rate. The success of this operation will also make an impact to other engineering subject such as geoscience and reservoir engineering diciplines (Ashadi and Dumrongthai, 2015).