Proceedings 41st New Zealand Geothermal Workshop 25-27 November 2019 Auckland, New Zealand MANAGING THE CYCLING EFFECT ON WELL EPT-L/1 Erwandi Yanto 1 , Kristina Emeralda Cici 1 , Gamal Hastriansyah 2 , Fernando Pasaribu 2 , Marihot S.P. Silaban 2 PT. Pertamina Geothermal Energy Skyline Building, 19th Floor, Jakarta Pusat, Daerah Khusus Ibukota Jakarta 10340 erwandi.yanto@pertamina.com ; kristinaecici@pertamina.com Keywords: Cycling, multiple feed zone, throttling, well head pressure drop. ABSTRACT The cycling effect is an impact that shows that the minimum pressure required by a well to remain stable in production is not achieved. The root cause of the cycling effect in a well is the presence of multiple feed zones which have difference pressure, enthalpy and permeability. This root cause can be concluded from data acquisition such as a PTS Shut-In survey and down-hole sampling. In the case of Well EPT-L/1, the cycling effect causes the well to not produce. It will always experience a pressure drop if produced with a minimum pressure of 8 barg in conditions of up to 60% throttling and when the pressure is less than 8 barg, the pressure in Well EPT-L/1 will slowly reduce. Thus, the operational pressure to produce the well should be a minimum of 8 barg. 1. PRINCIPAL THEORY 1.1 Cycling Effect The cycling effect in geothermal wells is a condition when the well suddenly stops flowing after discharging for a time and the mass flow, enthalpy and WHP dynamically change with constant settings at wellhead and the control valve. 1.2 Root Causes The cycling effect is caused by the presence of two significant feeds of different enthalpy and permeability. One of the feeds has poor permeability such that it cannot sustain continuous flow. Cycling is also possible without the presence of a steam zone due to a deep, high enthalpy, low permeability feed that discharges intermittently (Grant, et al, 2011). Fig 1. Pressure profiles in a cycling well (Grant, et al., 2011). In this case, cycling effect occurs when the well is discharging which affects the steam supply to the power plant for a few days. 2. WELL INFORMATION 2.1 Well Profile Well Name : EPT-L/1 Formation Type : Volcanic Max Deviation : Vertical (max 7.99 deg deviation) Wellhead Connection : 3-1/8” 3000K (R-31) Fig 2. Profile EPT-L/1 2.2 Reservoir Information Reservoir information is acquired by a PTS survey during production of the well. Pressure, temperature and feed zone contribution are essential for characterizing the reservoir. Pressure, temperature, and feed contribution are shown in Table 1 below. Table 1. Reservoir Well EPT-L/1 Based On PTS Flowing