scholarly journals Subsurface temperature from seismic reflection data: application to the post break up sequence offshore Namibia

2021 ◽  
Author(s):  
Arka Dyuti Sarkar ◽  
Mads Huuse
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Seismic Reflection ◽  
Surface Heat ◽  
Passive Margin ◽  
Petroleum Exploration ◽  
Subsurface Temperature ◽  
Seismic Reflection Data ◽  
Surface Heat Flow ◽  
Subsurface Temperatures

Accurate estimations of present-day subsurface temperatures are of critical importance to the energy industry, in particular with regards to geothermal energy and petroleum exploration. This paper uses seismic reflection observations of bottom-simulating reflections and subsurface velocities coupled with an empirical velocity to thermal conductivity transform to estimate subsurface temperature in a process dubbed reflection seismic thermometry. The case study is a frontier passive margin extending from the shelf edge to deep water in the central Lüderitz Basin, offshore Namibia. The bottom simulating reflector is used to derive surface heat flow. The thermal conductivity model was applied to seismic processing velocities to determine the subsurface thermal conductivity. Knowledge of surface heat flow and thermal conductivity structure allowed us to estimate subsurface temperatures across the study area. The results suggest the Lüderitz Basin has a working hydrocarbon system with the inferred Aptian Kudu source interval within the gas generation window.

Heat flow in the Uinta Basin determined from bottom hole temperature (BHT) data

Geophysics ◽  
1984 ◽  
Vol 49 (4) ◽  
pp. 453-466 ◽  
Author(s):  
David S. Chapman ◽  
T. H. Keho ◽  
Michael S. Bauer ◽  
M. Dane Picard
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Resistance ◽  
Geothermal Gradient ◽  
Surface Heat ◽  
Subsurface Temperature ◽  
The South ◽  
Uinta Basin ◽  
Surface Heat Flow ◽  
Bottom Hole

The thermal resistance (or Bullard) method is used to judge the utility of petroleum well bottom‐hole temperature data in determining surface heat flow and subsurface temperature patterns in a sedimentary basin. Thermal resistance, defined as the quotient of a depth parameter Δz and thermal conductivity k, governs subsurface temperatures as follows: [Formula: see text] where [Formula: see text] is the temperature at depth z=B, [Formula: see text] is the surface temperature, [Formula: see text] is surface heat flow, and the thermal resistance (Δz/k) is summed for all rock units between the surface and depth B. In practice, bottom‐hole and surface temperatures are combined with a measured or estimated thermal conductivity profile to determine the surface heat flow [Formula: see text] which, in turn, is used for all consequent subsurface temperature computations. The method has been applied to the Tertiary Uinta Basin, northeastern Utah, a basin of intermediate geologic complexity—simple structure but complex facies relationships—where considerable well data are available. Bottom‐hole temperatures were obtained for 97 selected wells where multiple well logs permitted correction of temperatures for drilling effects. Thermal conductivity values, determined for 852 samples from 5 representative wells varying in depth from 670 to 5180 m, together with available geologic data were used to produce conductivity maps for each formation. These maps show intraformational variations across the basin that are associated with lateral facies changes. Formation thicknesses needed for the thermal resistance summation were obtained by utilizing approximately 2000 wells in the WEXPRO Petroleum Information file. Computations were facilitated by describing all formation contacts as fourth‐order polynomial surfaces. Average geothermal gradient and heat flow for the Uinta Basin are [Formula: see text] and [Formula: see text], respectively. Heat flow appears to decrease systematically from 65 to [Formula: see text] from the Duchesne River northward toward the south flank of the Uinta Mountains. This decrease may be the result of refraction of heat into the highly conductive quartzose Precambrian Uinta Mountain Group. More likely, however, it is related to groundwater recharge in late Paleozoic and Mesozoic sandstone and limestone beds that flank the south side of the Uintas. Heat flow values determined for the southeast portion of the basin show some scatter about a mean value of [Formula: see text] but no systematic variation.

Heat production and thermal conductivity of rocks from the Pikwitonei–Sachigo continental cross section, central Manitoba: implications for the thermal structure of Archean crust

1987 ◽  
Vol 24 (8) ◽  
pp. 1583-1594 ◽  
Author(s):  
David M. Fountain ◽  
Matthew H. Salisbury ◽  
Kevin P. Furlong
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Cross Section ◽  
Heat Production ◽  
Thermal Structure ◽  
Granulite Facies ◽  
Surface Heat ◽  
Gamma Ray Spectrometry ◽  
Surface Heat Flow ◽  
Greenstone Belts

The Pikwitonei and Sachigo subprovinces of central Manitoba provide a cross-sectional view of the Superior Province crust. In cross section, the upper to mid-level crust is composed of synformal greenstone belts surrounded by tonalitic gneisses, both of which are intruded by granitoid plutons. This crustal structure persists downward into the granulite facies, where keels of the greenstone belts can be found. To constrain thermal models of the crust, we measured heat production and thermal conductivity in 60 rocks from this terrain using standard gamma-ray spectrometry and divided bar techniques. Large vertical and lateral heterogeneities in heat production in the upper crust are evident; heat production is high in granites and metasedimentary rocks, intermediate in tonalite gneisses, and low in the portions of greenstone belts dominated by mafic meta-igneous rocks. In the deeper granulite facies rocks, heat production decreases by a factor of two in the tonalitic gneisses and remains low in the high-grade mafic rocks. When applied to the Pikwitonei–Sachigo crust cross section, the laboratory data here do not support step function or exponential models of the variation of heat production with depth. However, estimates of surface heat flow and surface heat production for various sites in the crustal model yield the well-known linear relationship between surface heat production and surface heat flow observed for heat-flow provinces for both one- and two-dimensional models. This demonstrates that determinations of heat production with depth based on inversion of the linear heat-production–heat-flow relationship are nonunique.

scholarly journals Reflection Seismic Thermometry

2021 ◽  
Author(s):  
Arka Dyuti Sarkar
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Regime ◽  
Temperature Data ◽  
Subsurface Temperature ◽  
Reflection Seismic ◽  
The North ◽  
Blake Ridge ◽  
The North Sea ◽  
Subsurface Temperatures

An understanding of the subsurface thermal regime is beneficial to many disciplines, including petroleum and geothermal exploration, carbon capture and storage (CCS) and nuclear waste sequestration. This project developed and tested a new methodology for determining subsurface temperature using a non-invasive approach based on the velocity information derived from seismic reflection data. By solving a one-dimensional steady state approximation of Fourier’s Law, it is possible to determine a bulk thermal gradient as a function of depth, enabling the determination of temperatures across an entire volume using this methodology, termed reflection seismic thermometry. There are two principal components to this methodology, requiring 1) a bulk thermal conductivity structure and 2) heat flow and/or temperature data to condition the model. The first component uses an empirical velocity to thermal conductivity transform whilst the second uses sparse temperature data from boreholes or a bottom simulating reflector (BSR) to derive the shallow thermal regime and heat flow. The thermometry workflow has been applied to three case studies; in the Lüderitz Basin, offshore Namibia; the Blake Ridge, offshore USA; and the North Viking Graben (NVG) in the North Sea. In the frontier Lüderitz Basin, a BSR was identified and used to derive heat flow of 60-70 mW m-2. The Aptian source rock interval here was shown to presently be in the gas generative window. On Blake Ridge borehole velocities and a BSR were used to determine heat flow (43-56 mW m-2) and subsurface temperatures. Finally, methodology validation was conducted in the North Sea Basin using a high-resolution 3D full waveform inversion (FWI) velocity dataset calibrated with 141 wells. Forward models of subsurface temperatures were calibrated against the borehole temperatures, with inverse modelling used to derive heat flow at km scale lateral resolution. The availability of a fast track velocity volume for this area allowed comparison with the FWI derived thermal model results. It was found that stacking velocities were lower than well and FWI velocities, leading to overprediction of subsurface temperature. Modelling the temperature profile for CCS well 31/5-7 showed bottom hole temperature (BHT) within 6 °C of recorded BHT. With application and verification of the method in different basins, the versatility of the work conducted is demonstrated. It is envisioned that this technique opens avenues for the seismic characterisation of thermal regime in disparate settings and varied disciplines.

Thermal regime of the lithosphere in the Canadian ShieldThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.

2010 ◽  
Vol 47 (4) ◽  
pp. 389-408 ◽  
Author(s):  
Claire Perry ◽  
Carmen Rosieanu ◽  
Jean-Claude Mareschal ◽  
Claude Jaupart
Keyword(s):  
Heat Flow ◽  
Heat Generation ◽  
Seismic Refraction ◽  
Surface Heat ◽  
Canadian Shield ◽  
P Wave ◽  
Seismic Velocities ◽  
Flow Measurements ◽  
Surface Heat Flow ◽  
Mantle Heat Flow

Geothermal studies were conducted within the framework of Lithoprobe to systematically document variations of heat flow and surface heat production in the major geological provinces of the Canadian Shield. One of the main conclusions is that in the Shield the variations in surface heat flow are dominated by the crustal heat generation. Horizontal variations in mantle heat flow are too small to be resolved by heat flow measurements. Different methods constrain the mantle heat flow to be in the range of 12–18 mW·m–2. Most of the heat flow anomalies (high and low) are due to variations in crustal composition and structure. The vertical distribution of radioelements is characterized by a differentiation index (DI) that measures the ratio of the surface to the average crustal heat generation in a province. Determination of mantle temperatures requires the knowledge of both the surface heat flow and DI. Mantle temperatures increase with an increase in surface heat flow but decrease with an increase in DI. Stabilization of the crust is achieved by crustal differentiation that results in decreasing temperatures in the lower crust. Present mantle temperatures inferred from xenolith studies and variations in mantle seismic P-wave velocity (Pn) from seismic refraction surveys are consistent with geotherms calculated from heat flow. These results emphasize that deep lithospheric temperatures do not always increase with an increase in the surface heat flow. The dense data coverage that has been achieved in the Canadian Shield allows some discrimination between temperature and composition effects on seismic velocities in the lithospheric mantle.

scholarly journals Estimation of Curie-point depths, geothermal gradients and near-surface heat flow from spectral analysis of aeromagnetic data in the Loum – Minta area (Centre-East Cameroon)

2018 ◽  
Vol 27 (4) ◽  
pp. 1291-1299
Author(s):  
Jean Aimé Mono ◽  
Théophile Ndougsa-Mbarga ◽  
Yara Tarek ◽  
Jean Daniel Ngoh ◽  
Olivier Ulrich Igor Owono Amougou
Keyword(s):  
Spectral Analysis ◽  
Heat Flow ◽  
Curie Point ◽  
Surface Heat ◽  
Aeromagnetic Data ◽  
Near Surface ◽  
Geothermal Gradients ◽  
Surface Heat Flow
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