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Overview

The main obstacle for the development of high enthalpy geothermal energy is directly related to the importance of geological risk in the exploration phase but also, to a lower extent, during the development phase.

At the exploration phase, this potential risk is associated with additional costs, which are difficult to assess and poorly understood by the investors, thus preventing financial implementation from banks or credit agencies.

Currently, geoscientific studies based on traditional geophysical approaches (magnetotellurics (MT), gravity and magnetics), can address the geothermal exploration drilling strategy, but the probability of success remains low, though higher than in the O&G exploration (Oil & Gas). In this context, where the objective of achieving much higher level of success would secure more investors towards geothermal projects, TERANOV is currently developing a high-end geothermal exploration approach combining standard methods with methods and software tools at the cutting edge of the O&G exploration in order to build advanced 3D geological and flow models of naturally or hydraulically fractured geothermal reservoirs.

Various sources of information are exploited all together to generate more accurate reservoir models and to improve reservoir forecasting. These include well log, imaging and testing data which provide information at or in the vicinity of well locations, and jointly inverted microseismic, HR seismic and MT- seismic data, from which spatial trend information and enhanced full field images of the geothermal reservoir or the networks of fractures and faults can be obtained. The combined use of forefront methods and data yields a higher probability of success during the drilling exploration phase, increasing de facto attractiveness among investors.

During the development phase, the geological risk is partly epitomized during the drilling of production or reinjection wells (field development), but even more acutely at the geothermal reservoir characterization and appraisal level. Indeed, how could we garantee the level of resource availability from a field on the expected duration of plant operation? Again, this new TERANOV’s approach allows to characterize the resource much more accurately (structural and geological modeling, reservoir forecasting, quantification of uncertainty).

This new approach is cost-effective by reducing the risk of making inappropriate drilling or steam field development decisions. The initial investments are higher but justified to better know and understand the reservoir at the earliest stage of a project and to perform reliable reservoir performance forecasting.
As a matter of facts, the r&d activity of TERANOV focuses on geophysical exploration tools in order to drastically reduce field development costs in two ways:

• reducing the number of wells by locating and sizing the most promising areas where the productivity or injectivity of wells is expected to be higher;

• reducing the number of unproductive wells at all exploration and development stages of the project.

During the exploration stage, provided the appraisal of geological risk is properly mastered, full size exploration wells can be considered instead of slimholes. Despite the cost, full size wells in geothermal exploration have many advantages compare to slimholes. On the one hand, the well control is safer. On the other hand, enhanced and more accurate reservoir testing can be performed (e.g. productivity testing, well interference testing).

It is then possible to monitor reliable well production parameters, as provided in real field development conditions, and their impact on the reservoir (pressure drop ...).