| Title | Numerical Analysis of MCY01 Production Well Mechanism: Understanding of Well “Coughing” Phenomenon and Irregular Productivity |
|---|---|
| Authors | Hyungsul MOON, Jantiur SITUMORANG, Lutfhie AZWAR, Peter FRANZ |
| Year | 2018 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Coughing phenomenon, numerical model, wellbore simulator, productivity, production well |
| Abstract | Production well optimization is one of the key elements to the success of geothermal power plant operation. The MCY01 production well has been in operation since 2013 to supply steam to one of the Mercury-operated geothermal plants. Since 2015, MCY01 has been experiencing an irregular cycle or coughing phenomenon in which well head pressure (WHP) and productivity vary while flow control valves (FCV) are set constant. In order to optimize its production, an evaluation has been carried out to understand the production coughing mechanism. The most likely hypothesis of MCY01 irregular performance is thought to be due to competing feed zones (FZ) and the fluid connectivity of each feedzone to neighbouring wells. Flowing PTS (pressure, temperature, and spinner) analysis from 2013 to 2015 indicates the flow rate contribution of the bottom two feed zones have changed significantly over time. In order to validate the hypothesis of the competing feed zones, the numerical model, coupled with wellbore simulator, has been developed. Mercury’s internal wellbore simulator (Paiwera) is designed to model single phase, two-phase and steam flow in geothermal wells. It identifies the adjustments to perform at its best in simulating the diverse characteristics found in the reservoir during production. When the production time is updated, the wellbore simulator delivers the updated flow rate change at each feedzone with the time from the reservoir into the wellbore. The numerical model is well processed and MCY01 mechanism is explained by the competing feed zone numerical model. The summary of MCY01 numerical model analysis are: • The MCY01 reservoir pressure trend is determined by the total produced mass of nearby production wells (MCY02/03). • The long-term WHP increment is not due to reservoir pressure recovery. The mobility change due to saturation causes deliverablity curve changes at specific WHP pressure. • The numerical model suggests the irregular coughing phenomenon could be minimized when MCY01 is operated at the non-coughing zone. • Decline rate analysis at the normalized WHP of 24 barg is conducted based on generated deliverability curve from simulation during calibration and scenario periods. The process of MCY01 competing feed zone model and analyzed simulation results discussed in this paper demonstrates how the numerical model evaluation addresses the better understanding of the geothermal reservoir and practical recommendations on reservoir field survey. |