26 research outputs found
Real-time Mud Gas Monitoring: A Technique to Obtain Information on the Composition and Distribution of Gases at Depth While Drilling
Review of Recent Drilling Projects in Unconventional Geothermal Resources at Campi Flegrei Caldera, Cornubian Batholith, and Williston Sedimentary Basin
Unconventional geothermal resource development can contribute to increase power generation from renewable energy sources in countries without conventional hydrothermal reservoirs, which are usually associated with magmatic activity and extensional faulting, as well as to expand the generation in those regions where conventional resources are already used. Three recent drilling experiences focused on the characterization of unconventional resources are described and compared: the Campi Flegrei Deep Drilling Project (CFDDP) in Italy, the United Downs Deep Geothermal Power (UDDGP) project in the United Kingdom, and the DEEP Earth Energy Production in Canada. The main aspects of each project are described (geology, drilling, data collection, communication strategies) and compared to discuss challenges encountered at the tree sites considered, including a scientific drilling project (CFDDP) and two industrial ones (UDDGP and DEEP). The first project, at the first stage of pilot hole, although not reaching deep supercritical targets, showed extremely high, very rare thermal gradients even at shallow depths. Although each project has its own history, as well as social and economic context, the lessons learned at each drilling site can be used to further facilitate geothermal energy development.This research was co-funded by ICDP consortium and INGV for the CFDDP. Grant number CFDDP 05-2008.Peer reviewe
Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand
<p>During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5â893.2â
m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200â400â
m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartzâ+âfeldspar, most markedly below c. 700â
m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled.</p
Petrophysical, Geochemical, and Hydrological Evidence for Extensive Fracture-Mediated Fluid and Heat Transport in the Alpine Fault's Hanging-Wall Damage Zone
International audienceFault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hangingâwall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDPâ2). We present observational evidence for extensive fracturing and high hangingâwall hydraulic conductivity (âŒ10â9 to 10â7 m/s, corresponding to permeability of âŒ10â16 to 10â14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDPâ2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hangingâwall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and offâfault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation
Edelgase als Tracer fĂŒr Wechselwirkungen von Krusten- und Mantelfluiden mit diamantfĂŒhrenden Gesteinen des östlichen Baltischen Schildes
thesi
Stable Isotope Evaluation of Geothermal Gases from the Kızıldere and Tekke Hamam Geothermal Fields, Western Anatolia, Turkey
Volatiles transported from the Earthâs interior to the surface through permeable faults provide insights on the gas composition of deep reservoirs, mixing and migration processes, and can also be applied as gas-geothermometer. Here, we present carbon (ÎŽ13C), hydrogen (ÎŽ2H) and nitrogen (ÎŽ15N) isotopic data of CO2, CH4, and N2 from gas samples collected from the Kızıldere and Tekke Hamam geothermal fields, located along the eastern segment of the BĂŒyĂŒk Menderes Graben, Turkey. The stable isotopic composition of carbon (ÎŽ13C) ranges from +0.30 to +0.99â° (PDB) for CO2 from Kızıldere and is slightly more variable (â0.95 to +1.3â°) in samples from Tekke Hamam. Carbon isotope data in combination with CO2/3He data reveal that ~97% (Tekke Hamam) to ~99% (Kızıldere) of CO2 derives from limestone sources, with the residual CO2 being magmatic in origin with no evidence for CO2 from organic sources. The slightly higher contribution of limestone-derived CO2 in Kızıldere, compared to Tekke Hamam can be attributed to the higher temperatures of the Kızıldere reservoir and resulting amplified fluidâlimestone interaction, as well as helium depletion during phase separation for Kızıldere samples. In contrast to the carbon isotopic composition of CO2, the ÎŽ13C values of methane from Kızıldere and Tekke Hamam are clearly distinct and vary between â23.6 and â20.8â° for Kızıldere and â34.4 and â31.7â° for Tekke Hamam, respectively. The ÎŽ2H-CH4 composition is also distinct, measured as â126.7â° for Kızıldere and â143.3â° for Tekke Hamam. CO2-CH4 carbon isotope geothermometry calculations based on the isotopic fractionation of ÎŽ13C between the dominant component CO2 and the minor component CH4 reveals temperatures 20â40 °C and 100â160 °C higher than the bottomâhole temperatures measured for Tekke Hamam and Kızıldere, respectively. Based on the CO2-CH4 carbon isotope disequilibrium, unusual high methane concentrations of ~0.3 to 0.4 vol.-% and CH4/3He-ÎŽ13C-CH4 relationships we suggest thermal decomposition of late (Tekke Hamam) to over-mature (Kızıldere) organic matter and, to some extent, also abiogenic processes as principal source of methane. The N2/36Ar ratios of most samples reveal the existence of a nonâatmospheric nitrogen component within the gas mixture issuing from both fields, in addition to a constant contribution of atmospheric derived nitrogen accompanied into the system via the meteoric recharge of the geothermal system. Based on the ÎŽ15N isotopic ratios (varying between â4.44â° and 4.54â°), the nonâatmospheric component seems to be a mixture of both sedimentary (crustal organic) and mantle nitrogen. The thick Pliocene sedimentary sequence covering the metamorphic basement is the likely major source for the thermogenic content of CH4 and crustal N2 gas content in the samples
Scientific drilling workshop on the Weihe Basin Drilling Project (WBDP): Cenozoic tectonicâmonsoon interactions
The Weihe Basin, enclosed by the Chinese Loess Plateau to the north and the Qinling Mountains to the south, is an outstanding, world-class continental site for obtaining high-resolution multi-proxy records that reflect environmental changes spanning most of the Cenozoic. Previous geophysical and sedimentary studies indicate that the basin hosts 6000â8000âm thick fluvialâlacustrine sedimentary successions spanning the Eocene to Holocene. This sedimentary record provides an excellent and unique archive to decipher long-term tectonicâclimate interactions related to the uplift of the Tibetan Plateau, the onset/evolution of the Asian monsoon, and the development of the biogeography of East Asia. Owing to its location at the interface of the opposing westerly and Asian monsoon circulation systems, the Weihe Basin also holds enormous promise for providing a record of changes in these circulation systems in response to very different boundary conditions since the Eocene. To develop an international scientific drilling programme in the Weihe Basin, the Institute of Earth Environment, Chinese Academy of Sciences, organized a dedicated workshop with 55 participants from eight countries. The workshop was held in Xi'an, China, from 15 to 18 October 2019. Workshop participants conceived the key scientific objectives of the envisaged Weihe Basin Drilling Project (WBDP) and discussed technical and logistical aspects as well as the scope of the scientific collaboration in preparation for a full drilling proposal for submission to the International Continental Scientific Drilling Program (ICDP). Workshop participants mutually agreed to design a two-phase scientific drilling programme that will in a first phase target the upper 3000âm and in a second phase the entire up to 7500âm thick sedimentary infill of the basin. For the purpose of the 7500âm deep borehole, the world's only drill rig for ultra-deep scientific drilling on land, Crust 1, which previously recovered the entire continental Cretaceous sediments in the Songliao Basin, will be deployed in the WBDP
Real-time gas monitoring at the Tekke Hamam geothermal field (Western Anatolia, Turkey): an assessment in relation to local seismicity
This study presents the results of a real-time gas monitoring experiment conducted, via the use of a quadrupole mass spectrometer, in a mofette field within the Tekke Hamam geothermal site in western Anatolia (Turkey), a tectonically active region hosting several east-west trending grabens. The study is aimed to establish a baseline gas profile of the region. Within the framework of the experiment, gas compositions (CO2, N-2, O-2, H-2, H2S, CH4, He, and Ar) and flow rate of a mofette were monitored during two observation periods: November 2007-January 2008 and April-July 2008. During the course of monitoring, the major gas component was CO(2)with concentration changing around 96 volume percent. Other gases, from the most abundant to the least, were N-2, CH4, O-2, H2S, Ar, H-2, and He. The study produced a short-term, baseline gas profile of the region with daily/diurnal variations and temporal gas fluctuations appearing as instant signals. Although the temporal gas fluctuations did not reach the anomaly level (variations staying within the mean +/- 2 sigma), some of the variations in more than one parameter in the gas compositions (exceeding the mean +/- 1 sigma), accompanied by changes in the diurnal gas pulses lasting for long durations, were correlated with the seismic events selected according to the adopted seismic event elimination criteria. The variations were mainly attributed to changing gas mixing ratios in relation to porosity/permeability modifications possibly related to seismicity. Studies involving the continuous monitoring of meteorological parameters are necessary to assign these variations to geogenic events