Application Of Stimulation Design To A Geothermal Project: The Draškovec Geothermal Pilot, Croatia

Abstract

The successful development and exploitation of geothermal reservoir may have to rely on the enhancement of the natural permeability. This is typically achieved by stimulating the reservoir with the injection of high-pressure fluids. The oil and gas industry has used stimulation treatments to improve the production of petroleum reservoirs for decades. The techniques to develop specific stimulation fluids, to identify the stimulation targets, the design of the stimulation jobs and the operating procedures and tools have already been applied in several geothermal projects in Europe. We will present here an application of the use of reservoir modelling to design and optimize a stimulation treatment in a sandstone formation, as well as the forecast of the resulting production. This study demonstrates the successful use in a geothermal context of a software developed for the stimulation of unconventional hydrocarbons. A hydraulic fracturing (HF) design and optimization study was carried out for one well in the Draškovec geothermal field in Croatia. The option of a “classical” hydraulic fracturing uncertainty study, disregarding geomechanics and using standard reservoir engineering software, was discarded in favour of a two-step approach: hydraulic fracturing design and optimization using a dedicated software, followed by production forecasting with a compositional reservoir simulator. Firstly, the stimulation intervals were selected based on the porosity observed in the wells. The propagation of hydraulic fractures was modelled based on the stress profile in the wells, so to maximize the lateral extent. Subsequently, the forecast of the production of water and natural gas and of the reinjection of water and CO2 was simulated for a period of 25 years, comparing scenarios with or without stimulation treatment.

AAPG Datapages/Search and Discovery Article #90346 ©2019 AAPG European Region, 3rd Hydrocarbon Geothermal Cross Over Technology Workshop, Geneva, Switzerland, April 9-10, 2019