Geothermal Energy for Southern Thailand: Opportunities and Realities

Electrical energy demand for Southern Thailand is continuously increasing, with new coal/gas-fired power plants planned. However, coal/gas-fired power plants are not only large CO2 emitters, thus intensifying the on-going climate change crisis, but also their technology costs remain stagnant at comparable high levels. Solar and wind energy can be produced at far lower costs; however, their shares on the renewable energy mix are comparably small in Thailand, but with steady increase. A disadvantage of solar and wind energy is that the production is not constant due to day/night and weather, respectively. Such can be compensated by adding geothermal energy, which can act as a backbone of the renewable energy mix, although absolute amounts might be relatively low. In Southern Thailand, hot springs are the surface expressions of active geothermal systems at depth. Surface exit temperatures can reach up to 80°C and reservoir temperatures up to 143 °C, thus being considered as low enthalpy resources, which can be utilized applying binary power plant technology. In the current renewable power plant, geothermal energy is not considered, but Southern Thailand holds promising quantities of geothermal resources. The only current geothermal power plant in Thailand located in Fang can act as a positive example

Rainfall variations in central Indo-Pacific over the past 2,700 y

Tropical rainfall variability is closely linked to meridional shifts of the Intertropical Convergence Zone (ITCZ) and zonal movements of the Walker circulation. The characteristics and mechanisms of tropical rainfall variations on centennial to decadal scales are, however, still unclear. Here, we reconstruct a replicated stalagmite-based 2,700-y-long, continuous record of rainfall for the deeply convective northern central Indo-Pacific (NCIP) region. Our record reveals decreasing rainfall in the NCIP over the past 2,700 y, similar to other records from the northern tropics. Notable centennial- to decadal-scale dry climate episodes occurred in both the NCIP and the southern central Indo-Pacific (SCIP) during the 20th century [Current Warm Period (CWP)] and the Medieval Warm Period (MWP), resembling enhanced El Niño-like conditions. Further, we developed a 2,000-y-long ITCZ shift index record that supports an overall southward ITCZ shift in the central Indo-Pacific and indicates southward mean ITCZ positions during the early MWP and the CWP. As a result, the drying trend since the 20th century in the northern tropics is similar to that observed during the past warm period, suggesting that a possible anthropogenic forcing of rainfall remains indistinguishable from natural variability

Intraplate earthquake occurrence and distribution in Peninsular Malaysia over the past 100 years

Abstract Peninsular Malaysia is tectonically situated on a stable craton (intraplate) and so far experiences relatively little earthquake activities, thus considered as a region with low seismicity. This study uses earthquake data from 59 events obtained from various sources in the period 1922 to 2020. The overall seismicity in the study area is low as expected due to the general intraplate setting. Earthquakes occurred onshore and offshore of Peninsular Malaysia between latitudes 1° and 7° N and longitudes 99° and 105° E. The seismicity pattern shows that the epicenters are distributed spatially in some parts of the peninsula and in the Malacca Strait with several epicenter zones. Most of earthquakes are associated with several preexisting faults and fault zones indicating that they are the major contributor to the local seismicity. Meanwhile, some further earthquakes were caused by activities related to reservoirs. Magnitudes are ranging from Mw 0.7 to 5.4 with the majority is Mw 1.0 + and 2.0 +. Hypocenters are located in between 1 and 167 km deep (shallow to intermediate earthquakes) with the majority being shallow earthquakes (1–70 km). The deepest earthquake located in the Straits of Malacca can be associated with a slab detachment broken off from the Sumatran Subduction Zone. Finally, this study contributes to the understanding of the intraplate seismicity of Peninsular Malaysia as a basis for seismic hazard and risk assessment. Article Highlights Earthquake assessment over the last 100 year reveals low but clear seismicity with an associated seismic hazard and risk for certain areas. Shallow, low-magnitude earthquakes associated with reservoir activities and preexisting faults reactivated by the nearby subduction zone. A deeper, low-magnitude earthquake can be related to slab detachment from the Sumatran subduction zone toward the east

3D resistivity survey for shallow subsurface fault investigations

The shallow subsurface is subject to various human activities, and the place of occurrence of geohazards, e.g. shallow active faults. The identification of the location and orientation of such faults can be vital for infrastructure development. The aim of this study was to develop a low-cost 3D resistivity survey system, with reasonable survey time for shallow fault investigations. The study area in Songkhla Province, Thailand is located in an old quarry where faults could be identified in outcrops. The study area was designed to cover the expected fault with 100 electrodes arranged in a 10×10 square grid with an electrode spacing of 3 meters in x and y axis. Each electrode in turn was used as a current and potential electrode using a dipole-dipole array. Field data have been processed and interpreted using 3DResINV. Results, presented in horizontal depth slices and vertical xz- and yz-cross sections, revealed through differences in resistivity down to 8 m depths a complex structural setting with two shallow faults and dipping sedimentary rock layers. In conclusion, this study has shown that a 3D resistivity survey can imagine complex tectonic structures, thus providing a far more insight into the shallow subsurface

Relationship between electrical and hydraulic properties of sedimentary rocks

This study is looking closer to the relationship between hydraulic and electrical transport properties of porous water saturated sedimentary rocks. Transport of fluids through a network of open pores and/or cracks/fractures (permeability) and the transport of electrical charges in pore electrolytes both depend on three dominant factors: pore volume, degree of interconnection of the pores through pore throats, and the distribution and orientation of open cracks/fractures. Thus, petrophysical properties were measured on carbonates and sandstone samples from various drillings and different extraction depths. The directional (X, Y, Z) and pressure dependence (up to 200 MPa) of permeability (10(-15)-10(-21)m(2)) and electrical conductivity (< 10(-4)-> 0.1 S/m) were studied on identical samples that were cut in three orthogonal directions in regard to macroscopic visible sedimentary layering (X-Y-plane parallel to sedimentary layering, Z-direction perpendicular). Additionally, the petrophysical properties porosity (2.3-14.9 %), density (2.38-2.87 g/cm(3)), BET surface (0.111-0.384 m(2)/g) and mineralogical composition were determined, together with rock fabric elements. For each step in pressure, the frequency dependence of the complex electrical conductivity was recorded in the frequency range 800 Hz up to 1 MHz and interpreted using the Cole-Cole equivalent circuit model. The variations of electrical model parameters were correlated with the pressure dependence of the permeability. A correlation between the pressure dependencies of the electrical conductivity and permeability could be detected for each sample and direction X, Y, Z, but a general relation was not found

Quality-assurance of heat-flow data: The new structure and evaluation scheme of the IHFC Global Heat Flow Database

Since 1963, the International Heat Flow Commission has been fostering the compilation of the Global Heat Flow Database to provide reliable heat-flow data. Over time, techniques and methodologies evolved, calling for a reorganization of the database structure and for a reassessment of stored heat-flow data. Here, we provide the results of a collaborative, community-driven approach to set-up a new, quality-approved global heat-flow database. We present background information on how heat-flow is determined and how this important thermal parameter could be systematically evaluated. The latter requires appropriate documentation of metadata to allow the application of a consistent evaluation scheme. The knowledge of basic data (name and coordinates of the site, depth range of temperature measurements, etc.), details on temperature and thermal-conductivity data and possible perturbing effects need to be given. The proposed heat-flow quality evaluation scheme can discriminate between different quality aspects affecting heat flow: numerical uncertainties, methodological uncertainties, and environmental effects. The resulting quality codes allow the evaluation of every stored heat-flow data entry. If mandatory basic data are missing, the entry is marked accordingly. In cases where more than one heat-flow determination is presented for one specific site, and all of them are considered for the site, the poorest evaluation score is inherited to the site level. The required data and the proposed scheme are presented in this paper. Due to the requirements of the newly developed evaluation scheme, the database structure as presented in 2021 has been updated and is available in the appendix of this paper. The new quality scheme will allow a comprehensible evaluation of the stored heat-flow data for the first time