One of the challenges in producing a well is formation damage. Stimulation treatment is known can improve production by removing the formation damage. Matrix acidizing is the most known and proven effective for stimulation treatment. Three matrix acidizing models for sandstone are commonly used, i.e., Dowell, McLeod, and Kalfayan. Matrix acidizing study is conducted in geothermal sandstone formation well with quartz and silica dominated. Five acid fluid models will be injected to compare and evaluate the result of skin factor and productivity index during acidizing. Five types of acid will be used 12% HCl - 3% HF (Dowell model), 6% HCl – 1.5% HF (McLeod model), 10% HCl – 5% HF (Kalfayan model), 5% HF main acid, and using 9% HF main acid. This study uses well performance calculation and analysis to determine whether this well is a good candidate for acidizing. This study presents the sensitivity of the acid fluid model, volume and concentration injected to determine the optimum result of matrix acidizing design in this well. The result consists of the skin factor value after acidizing and the productivity index ratio before acidizing and after acidizing (FOI).

Binary cycle using organic working fluid or ORC system has been applied in geothermal and some other industrial processes to recover low grade and waste energy to generate electricity. The conventional system to utilize geothermal energy is a condensing system or back pressure system which depend on a turbine used in the system. Two units of the power plant in Flores, Indonesia are using back pressure turbine, which means that there is still a chance to increase the electrical power of the steam which is released through the turbine. The amount of exhaust steam available from these two units power plant is more than 62,000 kg per hour with 99°C of temperature and around 2,430 kJ/kg enthalpy. This research is trying to get the optimum power that can be generated by the ORC regarding other consideration parameters such as ambient temperature, thermodynamics condition of resource steam, and energy conversion of each apparatus. It is the aim of this paper to present a thermodynamic study on the utilization of ORC as the bottoming cycle with various types of working fluids to produce additional electricity. Several working fluids are chosen to find the optimum ORC system to utilize this exhaust steam such as isobutane, butane, isobutene, isopentane, propane, propyne, neopentane, R245fa, R236fa, and R134a. ORC system used in this research is simple ORC with basic components such as Pre-Heater, Evaporator, Expander, Condenser, and Pump. The properties of working fluids are calculated by REFPROP. The results show that this binary cycle can generate up to 2.25 MW with the thermal efficiency around 10% depend on the working fluid used. Two working fluids in this scenario that provide the best power generated are Propyne and Isopentane. The type of working fluid must also be considered, propyne is a wet type while isopentane is a dry type working fluid.

Well casing and cement temperature can change during geothermal production operation. The change of temperature occurs because of the heat transfer from the geothermal fluid to the formation. The heat transfer occurs because of the temperature difference in geothermal fluid and formation. The heat of fluid moves to the casing, cement, and formation through convection and conduction. This research aims to develop the heat transfer model in the steam production well, predict the steam heat loss and its effect on every 100 m well increment, and predict the well casing and cement temperature distribution and their effect on every well segment. The heat transfer model is an analytical calculation model developed to be the base of the calculation of heat loss and a temperature drop of well casing and cement. This model was developed for the calculation of heat loss in steam production well. The model was compared with a simulator to test the suitability. The fluid flow pressure drop and well lithology were considered in this model. The heat loss was very low during the steam production. The heat loss could be higher, along with the formation temperature drop. The material thermal conductivity and the well segment’s layer thickness could affect the steam heat transfer in the production well.

Reservoir monitoring of a geothermal field has an important role in determining the direction of company policies in managing a geothermal field, one of which needs to be monitored is by looking at changes in the pattern of the deliverability curve so that it can determine changes in the characteristics and performance of production wells. In order to update the deliverability curve, it is necessary to conduct periodic production tests. However, this cannot be done due to limited steam reserves. This research was conducted to determine the performance of production wells using the Flow Performance Test (FPT) method. This method is an alternative solution that can update the production well deliverability curve without leaving the gathering system. The FPT is applied to UBL-DL5 and JL2, UBL-JL3 is shown to validate the equations used. The data obtained were validated with TFT data and production test data where the deviation of the data obtained for UBL-DL5 was 1.42%, UBL-JL2 was 2.7%, and UBL-JL3 was 2.74%. The comparison of the UBL-DL5 and JL3 models based on time shows a significant production decline, and this is possible because the wells have only been operating within a period of 4 months – 1 year where the condition of production wells are still looking for stable condition, while the UBL-JL2 have not been seen there is a change in characteristic. The FPT is reliable enough to be used as an alternative method in monitoring production wells compared to the TFT method and the horizontal lip pressure production test. The FPT program should be conducted periodically and synchronized with the company’s operational activities plan. The delivery curve modeling as FPT result is used to monitor production wells’ condition as the basis for the company to develop a dynamic five-year work plan.