Reinjection To Sandstone Reservoirs Technology Showcase D5.3 – Draft Version
Creators: name: University Of Szeged
Publisher: name: Zenodo
Year: 2013
Subjects: geothermal energy
production
reinjection
non technical
environmental
sandstone reservoir

description: Reinjection is a complex multi-parameter procedure used during the utilization of geothermal energy. Reinjection means the replacing of used geothermal fluids into geological formations.

The reinjection of water into Upper Pannonian sandstone layers at a pressure above 100 bars has a long history in the Hungarian oil industry. Therefore, this technology is uneconomical and unsustainable on the long term for thermal waters! The operation of the first economically sustainable thermal water reinjection well in Hungary began in 1998 in the geothermal system of H.dmezőv.s.rhely. Since then, more than 2.8 million m3 of water has been reinjected at a pressure of 2-5 bars.

Currently, there are a high number of geothermal fields with operating reinjection systems all over the world. However, due to its complexity, it cannot be considered a routine procedure since it requires serious expertise and continuous research. At the same time, a number of international and Hungarian examples show that reinjection can be realized by adequate operation and construction.

The objective of the current sub-programme is the collection of experiences related to the operation of thermal water production and reinjection systems, and the elaboration of dimensioning, construction and filtration methods of pairs and triplets of wells.

The purpose and favourable features of reinjection from the aspect of reservoir operation:

- The maintenance of reservoir energy, prevention of pressure draw-down

- Disposal of used geothermal fluids, prevention of surface heat and chemical pollution

- Ensuring the economical long-term use of the geothermal reservoir.

The production had to be reduced significantly in geothermal fields with no reinjection. Reinjection facilitates the maintenance of reservoir pressures and the extension of the lifetime of geothermal systems. Therefore, the reinjection of the recovered thermal water is a fundamental task.

The increase of the production potential was observed after the beginning of reinjection in case of several high-enthalpy vapour-dominated systems (Geysers, Larderello, Matsukawa etc.) (Stefansson, 1997)

In the geothermal fields of Tianjin and Beijing in the P.R. of China, the use of geothermal energy and the production of thermal water increased significantly since the 1980s. As a result, the water levels of reservoirs decreased drastically, and therefore, a significant part of recovered thermal waters has been reinjected in the past 10 years. Due to the reinjections, the water levels have become stable, and in some areas, they began to rise slowly (Kun et al, 2008).

Without reinjection, only a small part of the thermal energy in place in geothermal reservoirs can be recovered. Accordingly, the current objective is to use as much reinjected fluid in production as possible. The geological features of the reservoir, the location of and the distance between the wells play a major role in this. We can state that around 85% on the reinjected fluid can be recovered by a favourable geometric configuration. In the case of peripheral reinjection, we can calculate with a return rate of 30%. During reinjection, we increase the natural refilling of the system, thus we contribute to the better recovery of the reservoir’s energy. (Stefansson, 1997)
description: FP7