Production and Reinjection Evaluation on The Basis of 3D Time-lapse Microgravity Inversion

An equilibrium in the geothermal is important especially in terms of reservoir sustainability. Fluid in the reservoir will continue to decrease if the reinjection activity unable to compensate the steam production. Field "US" is one of the geothermal field that has more than 5 Megaton production rate. The fluid depletion should be controlled so the reservoir is able to continue to supply the steam. Re-injection strategy plays an important role to keep up with the amount of fluid that comes out. Preparation of this strategy requires 4D microgravity or time lapse microgravity method to know which area has the most fluid depletion. The use of microgravity for monitoring has become the ultimate method in geothermal. In this paper, we will discussed on how advanced microgravity processing able to be a consideration in the production and re-injection strategy. The data used in this paper is microgravity survey which conducted every year from 2015 - 2017. Further processing such as inverse modelling is also used in this paper to estimate the mass changes inside the area of interest. In the modelling, we used staggered grids as an initial model to produce more suitable final model. Initial models are made based on geophysical research data such as Magnetotelluric resistivity data and hypocenter from Micro-earthquake so the position of the top reservoir can be determined. The Gauss's Flux method also used in this paper to be compared with the result from inversion. The result of this research is to maintain the sustainability of reservoir in geothermal energy by make re-injection plans more effective and precise. (paper)