Evaluation of Abandoned Hydrocarbon Wells in the Pannonian Basin a Case Study

Transcription

1 Proceedings World Geothermal Congress 2015 Melbourne, Australia, April 2015 Evaluation of Abandoned Hydrocarbon Wells in the Pannonian Basin a Case Study Attila Kujbus and Attila Zoltán Kujbus Hant Str 16/B, Budapest, H-1223 Hungary akujbus@geoex.hu Keywords: Pannonian Basin, abandoned hydrocarbon wells, evaluation of wells ABSTRACT There are more than 8000 deep hydrocarbon wells in Hungary; however, the majority of them are out of utilization. The Hungarian State owns 3000 wells, none of which is in operation. The State intends to sell them to geothermal project developers for utilization. The geothermal potential is fairly high in the Pannonian Basin and a lot of geothermal project developers tend to save financial resources through the recompletion of abandoned hydrocarbon wells. This case study deals with an investigation process, when the State recommended 18 wells to utilize in Eastern Hungary. Five municipalities were concerned, and they showed interest in developing geothermal projects. Geothermal Express Ltd. was asked to carry out a professional evaluation of the utilization of the 18 wells. The methodology of the evaluation included Technical review of the well design and history by analyzing the well file Regional geological review Hydrogeological analysis of the well sites as well as the area of the related municipalities Energy audit in the related five municipalities Setting up geothermal concept including all technical and also financial issues A complex Team was set up by Geothermal Express Ltd. to implement a professional evaluation. The GeoEx Team focused on five professional directions: geothermal technology, deep drilling, hydrocarbon geology, hydrogeology and energetics. The Team collected the well files, visited the wells and investigated the well sites. The Team also prepared energy audits in the related municipalities and reviewed the expected industrial or agricultural development. In the results of their evaluation the Team distinguished three different cases of the 18 wells. The well is technologically inappropriate for any kind of utilization The recompletion of the well is very expensive The location is far from the optimum site; the well does not serve profitable geothermal purposes None of the wells were appropriate to utilize for profitable geothermal purposes. The Team recommended an optimal geothermal utilization for every municipality, but the abandoned hydrocarbon wells were excluded. The result was rather frustrating. The Team reviewed the methodology of this evaluation in order to define if the methodology of evaluation is inappropriate, only the concerned area and these wells were inappropriate or the concept of geothermal utilization of abandoned hydrocarbon wells is generally inadequate. The complex approach and the professional methodology were appropriate, but a few lessons are to be drawn. No illusions concerning the well conditions and recompletion costs A complete well file is essential At least minor maintenance of the abandoned wells is needed The site of the well should be saved. As a general conclusion, the Team recommended the continuation of the hydrocarbon well evaluation process, but without illusions and by taking into consideration the experience from former evaluation processes. 1. INTRODUCTION The Hungarian hydrocarbon industry is over 80 years old. The large majority of the hydrocarbon wells in Hungary are out of utilization. The State owns 3000 wells, none of which is in operation. The State intends to sell them to geothermal project developers for utilization. Moreover the leading Central-Eastern European oil company, MOL Plc. also has thousands of abandoned wells. 1

2 The geothermal potential is fairly high in the Pannonian Basin and a lot of geothermal project developers tend to save financial resources through the recompletion of abandoned hydrocarbon wells. Therefore the evaluation of the old hydrocarbon wells is a key question in the Hungarian geothermal sector. This case study deals with an investigation process, when the State recommended 18 wells to utilize in Eastern Hungary. Five municipalities were included, and all of them showed interest in developing geothermal projects. Geothermal Express Ltd. was asked to carry out a professional evaluation of the utilization of the 18 wells. Figure 1 describes the area, where the wells were drilled. The evaluated area is located in the Pannonian Basin, which has one of the best geothermal potential in the European Continent. The area is in the Hungarian Plain, near the Romanian border. The area covers five municipalities. These municipalities wish to develop their energy sources, therefore they are interested in their geothermal potential and the technical condition of the abandoned hydrocarbon wells in their territory. Evaluated Area Pannonian Basin Figure 1: Location of the evaluated area Figure 2 presents the map of the 18 wells and also the 5 municipalities with WGS coordinates. The former exploratory wells are situated not far from the towns and villages; therefore the idea of their utilization is rational. Figure 2: Map of the 18 wells and 5 municipalities 2

3 The general geothermal potential in the Pannonian Basin is perfect for direct heat production and there are numerous good examples in the Hungarian Plain of geothermal district heating, city center heating and also agricultural thermal heat consumption. The existing hydrocarbon wells can make a new geothermal project cheaper and less risky. 2. METHODOLOGY OF THE EVALUATION 2.1 Evaluation steps The main task was to create a geothermal project concept in all the five towns and villages. The utilization of hydrocarbon well or wells was included into the concept. The complex work consisted of three different parts; technical, financial and project focused evaluations were performed. The complex investigation process included Technical review of the wells design and history by analyzing the well files Regional geological overview Hydrogeological analysis of the wells sites as well as the area of the related municipalities Energy audit in the related five municipalities, focusing on the natural gas consumption of municipality owned buildings (City Hall, schools, nurseries, library, cultural center, etc.) Setting up geothermal project concept including all technical and also financial issues. 2.2 The evaluation team A complex team was set up by Geothermal Express Ltd. to implement a professional evaluation. The GeoEx Team focused on five professional directions: deep drilling, hydrocarbon geology, hydrogeology, energetics and geothermal technology. The Team collected and analyzed the well files, visited the wells and investigated the well sites. The Team also prepared energy audits in the related municipalities and reviewed the expected industrial or agricultural development. 2.3 Data processing The general geological regional evaluation was based on the public Hungarian databases and maps. The hydrocarbon geology concept was set up on the data of water and thermal water wells of the East-Hungarian region. In order to ensure the uniform evaluation related to all wells, an Evaluation Report template has been prepared. The report contained the following chapters: Basic data of the well (name, coordinates, deepening date, time, actual status) Surface access (road, well area, wellhead and equipment) Subsurface conditions (well construction, well completion, open section, actual technical status, data of former well tests) Technical opportunities and challenges Necessary work-over and well completion Recommendation Costs of the whole well activity The Team members visited the wells and reviewed the well sites. The majority of the wells were hardly reachable. One well was destroyed, and a few of them lost their well-head during a well liquidation. The others are also located in the middle of agricultural plantations. 3

4 Figure 3: A saved well site Figure 4: An old well-head with a good condition 4

5 Team members reviewed the sites, took photos and by involving the well documentation, the technical evaluation could be performed. 3. RESULTS OF THE WELLS EVALUATION 3.1 Analysis of the evaluation reports The depth range of the evaluated wells extended from 1300 to 2700 meters. An Evaluation Report (its structure was presented in 2.3) has been prepared for each well. The list and main observations were collected in Table 1. Table 1: List and main observations of the wells Name Related municipality General condition Necessary cost of works, HUF million Opportunity Ár-1. Ártánd inappropriate high technical risks of well recompletion - - Ár-2. Ártánd inappropriate, poor well structure - - Bike-7. Biharkeresztes recompletion opportunity 173,7 far from consumption site Bike-30. Biharkeresztes recompletion opportunity 157,7 far from consumption site Bike-31. Biharkeresztes recompletion opportunity 129,5 does not penetrate prospective formations Bike-32. Biharkeresztes recompletion opportunity 219,9 too expensive Bojt-1. Bojt recompletion opportunity 192,5 + surface works too expensive Kö-1. Körösszegapáti inappropriate, destroyed during a gas explosion - - Kö-2. Körösszegapáti inappropriate, no pressure - - Kö-10. Körösszegapáti inappropriate, poor well structure - - Kö-11. Körösszegapáti inappropriate, poor well structure - - Kö-12. Körösszegapáti inappropriate, poor well structure - - Kö-16. Körösszegapáti inappropriate, poor well structure - - Kism-1. Kismarja inappropriate, poor well structure - - Kism-2. Kismarja inappropriate, poor well structure - - Kism-30. Kismarja inappropriate, poor well structure - - Kism-31. Kismarja recompletion opportunity 137,2 Natura 2000 environment protection area Mp-2. Mezőpeterd recompletion opportunity 259,1 too expensive This table helped the technical and financial analysis. Several causes were identified that obstruct the utilization of the wells in a geothermal project. They were sorted into three main categories: The well is inappropriate because of technical/geological causes The well is far from the heat consumption site The recompletion of the well would be too expensive 5

6 3.2 Classification of the 18 wells Technologically/geologically inappropriate wells Table 2: List of technical inappropriateness Type of inappropriateness Cause of inappropriateness Classification Destroyed Gas explosion destroyed the well, only a crater exists Well does not exist Liquidated Well structure is poor, recompletion is risky Missing prospective geological formations The well exists but well-head is removed, the site is recultivated for agricultural production Cementing, casing or tubing damaged. Technical content of recompletion includes operations with uncertain success. The well did not penetrate the two main prospective geological formations of the region Well utilization is not impossible, cost is to be analyzed Drilling a new well is more advisable Thermal water productivity or injectivity is not feasible. The majority of the wells belong to these categories. If the well is destroyed or prospective geological formations are missing, the well is to be thrown. Eleven wells from the eighteen were qualified technically inappropriate. However, if the well suffers only some technical trouble that has a chance to be repaired, recompletion costs or market existence are to be analyzed. Figure 5: Old well with road nearby Figure 5 presents the most interesting inappropriateness. Since the well is abandoned, an important road with heavy traffic has been constructed near the site. The distance between the well and road is smaller than the safety distance of a rig which should operate on the well Wells with expensive recompletion Only seven wells from the eighteen were qualified technically to be in good condition and appropriate for cost analysis. The key intention of utilizing these old wells was cost saving and the Hungarian geothermal sector was under the illusion that hundreds or even thousands of abandoned hydrocarbon wells could be utilized for geothermal energy production purposes. 6

7 Unfortunately, during the conceptual technical planning of the seven wells in good condition, significant extra costs emerged. Rig mobilization and demobilization costs are equal to mob - demob costs of a new well. Some tests are needed in order to finalize the recompletion technical content. Technical risks of the old wells have to be eliminated. These wells did not show significant thermal water productivity during their deepening therefore some kind of layer stimulation is needed for each well. Table 1 presents that the range of recompletion costs extend from HUF130 million to HUF260 million (~ 0.43 million 0.86 million). Cost calculations show that new well drilling with the same technical parameters (depth, structure, technical services) would need the same level of costs in case of every well. The saving of pipe cost and drilling time is equal or higher to the necessary services of well recompletion in the case of these seven old wells. Therefore recompletion of the old wells is not advisable concerning these seven wells Wells far from heat consumption site There is an important point in the general evaluation of the remaining seven wells. Their location is not optimal in a geothermal project. The Evaluation Team examined the geothermal resource opportunities with a regional geological overview and a hydrogeological analysis of the area of the related municipalities. The Team also performed an energy audit in the related five municipalities, focusing on the natural gas consumption of municipality owned buildings. All important buildings were involved, City Halls, schools, nurseries, libraries, sports and cultural centers, etc. The heating and cooling demand was assessed and it was covered by the geothermal resource opportunities. A greenfield geothermal project concept was set up in every municipality area. The remaining seven wells unfortunately did not fit into the project concepts. They were far from the conceptual project area. 3.3 General evaluation of the 18 wells None of the wells were appropriate to utilize for profitable geothermal purposes. The Team recommended an optimal geothermal utilization for every municipality, but the abandoned hydrocarbon wells were excluded. The result was rather frustrating. 4. UTILIZATION OPPORTUNITIES OF ABANDONED HYDROCARBON WELLS 4.1 Agricultural utilization The hydrocarbon wells can be utilized not only in a district heating project, but also in an agricultural direct heat supply system. An existing well can be installed as a production or injection well of a greenhouse system. There are a lot of good examples in the Hungarian Plain, where the former hydrocarbon well produces thermal water and can heat greenhouses for decades. The Evaluation Team analyzed this opportunity. Unfortunately, the areas of the wells are not appropriate for establishing profitable greenhouses. 4.2 Hybrid utilization The next well utilization opportunity is a renewable energy hybrid system. Figure 6 Hybrid utilization opportunity (after Björn, 2013) 7

8 Figure 6 presents an opportunity of complex renewable energy utilization, as a similar project is already operating in Denmark (Björn, 2013). The produced geothermal energy can be combined with solar, biomass/biogas, electric or waste heat to supply the consumers. The inter-seasonal heat management can be solved by means of underground heat storages (Homuth et. al., 2013). The Evaluation Team reviewed all types of hybrid opportunities, but did not find solution for utilization of the hydrocarbon wells. 5. CONCLUSIONS, RECOMMENDATION 5.1 Review of the well evaluation approach According to the proposal of the Evaluation Team none of the 18 wells can be utilized in a profitable geothermal project. This result is not what the municipalities had expected. A question has emerged whether the technical/financial reality or the approach of the Evaluation Team was inappropriate. The Team reviewed the methodology of this evaluation in order to define if the methodology of evaluation is inappropriate, only the concerned area and these wells were inappropriate or the concept of geothermal utilization of abandoned hydrocarbon wells is generally inadequate. The Team set up an optimal geothermal concept for all municipalities. The technical solutions covered geothermal based district heating (Biharkeresztes-Ártánd), thermal water production for heat pumps (Kismarja) and direct geothermal heat supply for greenhouses (Berekböszörmény and Körösszegapáti). The concepts are consistent both from technical and financial considerations, and the projects can be profitable. The utilization of the abandoned hydrocarbon wells was recalculated, but their utilization in the projects is not profitable or feasible. 5.2 Recommendation for future well evaluations The complex approach and the professional methodology were appropriate in this project, but a few lessons are to be drawn. No illusions concerning the well conditions and recompletion costs A complete well file is essential The owner has to know the basic technical conditions of the wells; destroyed or liquidated wells are not to be recommended for purchase At least minor maintenance of the abandoned wells is needed The site of every old well should be saved A regional approach is important; evaluation of a single well is risky. As a general conclusion, the Team recommended the continuation of the hydrocarbon well evaluation process, but without illusions and too optimistic expectations, and by taking into consideration the experience from former evaluation processes. The Team confirmed the list of disadvantages and advantages of the abandoned hydrocarbon wells in a geothermal program as below: Disadvantages Not optimal location for geothermal purposes and small diameter piping Old wells often have incomplete documentation Cement column sometimes is not appropriate for long-term hot thermal water production Regularly no temperature insulation Prospective wells are often far from heat market Advantages Lower well costs, which is, however, to be proved in case of every existing well Often existing infrastructure Existing core samples Well files contain technological and geological information. The significant information that can be gained from the documentation of the 8000 Hungarian hydrocarbon wells establishes a stable scientific background for the deep geothermal exploration sector. Every well that is utilized in a geothermal project is a surplus, an extra profit for the geothermal energy business. Therefore evaluation of abandoned hydrocarbon wells is an opportunity that is to be continued. 8

9 REFERENCES Björn, H.: Borehole Thermal Energy Storage in Combination with District Heating, European Geothermal Energy Congress, Pisa, Italy, 2013 Homuth, S. et al.: Medium Deep High Temperature Heat Storage (MDHTS), European Geothermal Energy Congress, Pisa, Italy,