Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Direction Of Principal Stresses In Sabalan Geothermal Region
Aftani, M.H. (Department of Engineering and Structural Geology, College of Science) | Eliassi, M. (Department of Engineering and Structural Geology, College of Science) | Bohloli, B. (Department of Engineering and Structural Geology, College of Science) | Talebi, B. (SUNA Renewable Energy Organization of Iran)
ABSTRACT Exploration in trachyandesitic Mount Sabalan, near the town of Meshkin-Shahr in north western Iran, indicated that this area hosts geothermal reservoir. In this study, we determine the direction of principal stresses using structural geology features exposed on the surface. These features include slickensides and fault steps. Analysis of the recorded slickenside traces in six districts was carried out using multiple inverse method. Results of the analyses indicated that the direction of the three principal stresses in every district is independent of the others. However, in all districts, maximum principal stress is vertical, minimum and intermediate principal stresses are horizontal. One of the applications of stress direction is in the design of hydraulic fracturing. Since the permeability of this reservoir is rather low, this stimulation technique could be a solution for enhancing productivity. Direction of the minimum stress dictates the geometry of created fracture. In this case the fracture would propagate vertically. 1. Introduction 1.1. History of Project In 1974, for assessment of geothermal resources potential in Iran some primarily studies including aeromagnetic and gravimetric operation have been done in area more than 8300 km2. After a long standby, in 1990 previous documents were reviewed and resistivity operations were conducted. According to the resistivity anomalies and geochemical alteration Meskin- Shahr (Northwestern Sabalan) introduced as the first geothermal potential in Iran. So, three exploration (production) wells up to 3200, 3176 and 2260 m and two injection wells up to 650 m have been drilled. Completion investigations such as logging and flow tests indicated that temperature of reservoir is about 240°C and permeability of reservoir is medium to low. Permeability is one of the important factors in using captured heat. Base on some calculations and estimations, it is essential to increase permeability by artificial methods. To increase permeability, we suggest hydraulic fracturing. During the hydraulic fracturing, artificial fractures are created in reservoir. Created fractures extend perpendicular to minimum horizontal stress. So, by knowledge of principal stress directions, we can determine artificially fractured geometry and drill the injection wells in the best direction. In this study, we try to determine direction of the in-situ stresses in Meskin-Shahr geothermal field using multiple inverse method. 1.2. Regional Geology Study area is located around the Sabalan Mountain in Ardabil province, northwestern Iran (Fig. 1). Geological setting of this area such as lithology and tectonics is controlled by Sabalan volcano activities. Volcanic structure is spot and stratovolcan like Stromboli volcano in Italy. Central volcano erupted on the main conjugated fracture over the paleohorst with E-W trend. According to published studies, volcanic activity in Sabalan started Eocene and resumed in Pliocene by eruption of trachyandesitic to andesitic lava flow through the main caldera. After caldera collapsing in Early Pleistocene, central caldera partially filled by trachyandesit–trachydacite 1394 lava flows [1]. The study area is located in complex compressional zone between Iran, Arabia and Eurasia plates in Alborz- Azerbaijan structural zone.
- Geology > Geological Subdiscipline > Volcanology (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Renewable > Geothermal > Geothermal Resource (0.54)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Non-Traditional Resources > Geothermal resources (1.00)
Magnitude Of In-Situ Stresses In Sabalan Geothermal Reservoir
Haftani, M. (Department of Engineering and Structural Geology, College of Science) | Bohloli, B. (Department of Engineering and Structural Geology, College of Science) | Eliassi, M. (Department of Engineering and Structural Geology, College of Science) | Talebi, B. (SUNA Renewable Energy Organization of Iran)
ABSTRACT The first geothermal energy plant in Iran has been developed in northwestern Sabalan for direct heat extraction and indirect electricity generation. For these reasons three geothermal wells have been drilled up to 3000 m depth. The temperature of the reservoir determined by well log is about 240°C. Geological investigation as well as production tests showed that the permeability of reservoir is medium to low. One of the practical solutions for increasing permeability of reservoir is hydraulic fracturing. To design a successful fracturing job, we have to characterize material constants and in-situ conditions. In this study, we have used the drilling and geomechanical data to constrain the in-situ stresses in one of the geothermal wells, NWS3. The magnitude of vertical stress (óV) was calculated from lithology log, the gradient of which is 0.031 MPa/m. Data of Leak-Off test and poroelastic theory were used to calculate minimum horizontal stress (óh) which is 0.011 MPa/m. The magnitude of maximum horizontal stress (óH) was constrained using frictional limit to stress that yield a gradient of 0.014 MPa/m. 1. Introduction 1.1. Geothermal Project Since 1975 some studies have been carried out to indicate potential of geothermal resources in Iran. Primarily studies were included aeromagnetic and gravimetry operation and preparing geological and geochemical maps of probable area over more than 8300 km2. After these studies, some regions were introduced as main geothermal resources: Sabalan, Damavand, Khoy-Maku and five other small parts in Sahand. After a long standby, in 1990 previous documents were reviewed and resistivity operations were conducted by KML (Kingston Morison Ltd.). Then, resistivity anomalies, geological evidences and hydrothermal alteration compared and finally Meskin-shahr introduced as the first geothermal potential. According to completion investigations in wells indicated that temperature of reservoir is about 240°C. Three exploration (production) wells up to 3200, 3176 and 2260 m and two injection wells up to 650 m have been drilled and tested. Permeability controlling factors and results of flow tests in production wells showed that permeability of reservoir is medium to low [1]. Presence of permeability is one of the important factors in using captured heat. Generally, the higher the permeability, the higher hot water can be extracted. Base on some calculations and estimations, it is essential to increase permeability by artificial methods. To increase permeability, we suggest hydraulic fracturing to create fracture in reservoir. During hydraulic fracturing, high pressure fluid injects into desired packed depth and the surrounding rocks are cracked. To carry out successful fracturing jobs, we have to determine in-situ stresses and geomechanical constants such as: Poisson's ratio. In-situ stresses play very important role in fracture geometry and fracture initiation, propagation and closure of created fractures. In this study, we try to determine in-situ stresses in Meshkin-Shahr geothermal field using both geomechanical and well drilling data.
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Renewable > Geothermal > Geothermal Resource (0.89)
- Oceania > Australia > South Australia > Cooper Eromanga Basin (0.98)
- Oceania > Australia > Queensland > Cooper Eromanga Basin (0.98)