Prospects of Using Hydrocarbon Deposits from the Autochthonous Miocene Formation (Eastern Carpathian Foredeep, Poland) for Geothermal Purposes

Abstract

There are many oil and gas fields around the world where the vast number of wells have been abandoned or suspended, mainly due to the depletion of reserves. Those abandoned oil and gas wells (AOGWs) are often located in areas with a prospective geothermal potential and might be retrofitted to a geothermal system without high-cost drilling. In Poland, there are thousands of wells, either operating, abandoned or negative, that might be used for different geothermal applications. Thus, the aim of this paper is not only to review geothermal and petroleum facts about the Eastern Carpathian Foredeep, but also to find out the areas, geological structures or just AOGWs, which are the most prospective in case of geothermal utilization. Due to the inseparability of geological settings with both oil and gas, as well as geothermal conditionings, firstly, the geological background of the analyzed region was performed, considering mainly the autochthonous Miocene formation. Then, geothermal and petroleum detailed characteristics were made. In the case of geothermal parameters, such as formation’s thickness, temperatures, water-bearing horizons, wells’ capacities, mineralization and others were extensively examined. Considering oil and gas settings, insights into reservoir rocks, hydrocarbon traps and migration paths issues were created. Then, for evaluating geothermal parameters for specific hydrocarbon reservoirs, their depths were established based on publicly available wells data. Thereafter, the average temperatures for selected reservoirs were set. As the effect, it turned out that most of the deposits have average temperatures of 40/50 °C, nonetheless, there are a few characterized by higher (even around 80 °C) temperatures at reasonable depths.

Oilfield Brine as a Source of Water and Valuable Raw Materials—Proof of Concept on a Laboratory Scale

“…The depleted hydrocarbon reservoirs with high potential for producing reservoir water in Poland are located in the south of the country, in the Carpathian Foredeep. The Carpathian Foredeep is asymmetric and filled mainly with clastic Miocene sediments up to 3 km thick [52]. Based on available data and our own measurements as part of the CompLithium project [53], the authors sampled about 50 L of brine from a selected reservoir located in the eastern part of the Carpathian Foredeep.…”

A New Strategy for Pre-Selecting Gas Wells for the Water Shut-Off Treatment Based on Geological Integrated Data

“…Intervals saturated with natural gas selected for the analysis in six of the abovementioned wells (C-2, J-5K, J-8K, J-7, P-6, Z-74) were associated with multi-horizon gas fields, located within the profile of clastic formations of the autochthonous Miocene of the Carpathian Foredeep [16][17][18][19][20][21][22][23]. The gas-bearing horizons in the two remaining wells (T-3, Z-1K) represent massive gas formations, associated with a complex of Devonian carbonate rocks sealed with clay formations of the autochthonous Miocene or (locally) Carboniferous [24][25][26].…”

“…Generally, in the area of research, five main structural levels can be distinguished: (1) the series of Neoproterozoic anchimetamorphic rocks of the Ediacaran age, (2) the Meso-Paleozoic rock complex, characterised by strongly diversified thicknesses and lithology, (3) the autochthonous Miocene formations which were initially deposited in the Carpathian Foredeep Basin, (4) the Miocene-age deformed sediments located in front of the Carpathian orogen, (5) the allochthonous formations traditionally included within several tectonic units of the Outer Carpathians. Intervals saturated with natural gas selected for the analysis in six of the above-mentioned wells (C-2, J-5K, J-8K, J-7, P-6, Z-74) were associated with multi-horizon gas fields, located within the profile of clastic formations of the autochthonous Miocene of the Carpathian Foredeep [16][17][18][19][20][21][22][23]. The gas-bearing horizons in the two remaining wells (T-3, Z-1K) represent massive gas formations, associated with a complex of Devonian carbonate rocks sealed with clay formations of the autochthonous Miocene or (locally) Carboniferous [24][25][26].…”