Andrea Förster

3D baseline seismics at Ketzin, Germany : The CO2SINK project

A 3D 25-fold seismic survey with a bin size of 12 by 12 m and about 12 km(2) of subsurface coverage was acquired in 2005 near a former natural gas storage site west of Berlin, as part of the fiv ...

Application of optical-fiber temperature logging - An example in a sedimentary environment

Continuous‐temperature depth logs, especially when recorded in boreholes under thermal equilibrium conditions, provide detailed information of the subsurface thermal structure, which is necessary for the determination of reliable heat‐flow and rock thermal properties. In conjunction with independent thermal‐conductivity determinations, thermal logging data also allow the separation of heat conduction effects from thermal convection effects by fluid flow driven by various pressure differences such as pore fluid pressure. The Earths thermal field is related intimately to geothermal resources and hydrocarbon resources. Therefore, the characterization of temperature in the subsurface and its relationship to lithology is of critical importance.

Field comparison of conventional and new technology temperature logging systems

Abstract Field tests were conducted in the summer of 1995 on four state-of-the-art temperature logging systems: an analog, electric-line, system; two pressure and temperature recording memory tools (in-hole computer systems); and a Distributed optical fibre Temperature Sensing (DTS) system. The tools produced accurate, detailed, temperature versus depth and temperature gradient versus depth logs at depths to 2 km and temperatures to 200°C. Absolute temperature differences up to 0.4°C were noted between tools. The computer and electric-line tools have significantly better precision and resolution than the DTS, but the DTS has the advantage of being able to measure temperature instantaneously throughout the hole, and would be well suited for monitoring dynamic systems and gas-filled wells. The multiple independent logs demonstrate that most of the “noise” seen in gradient logs is due to convection cells, which may have dimensions several times the borehole diameter, and that these convection cells are currently the limiting factor in resolving wellbore temperatures in most settings.

Problems and Potential of Industrial Temperature Data from a Cratonic Basin Environment

A thin veneer of clastic and carbonate sediments 460–1,375 m (1,500–4,500 ft) thick overlies a Precambrian crystalline basement complex in southeastern Kansas (Midcontinent, USA). Well-log temperatures were analyzed and related to modeled temperatures for different-size areas in a relatively simple structural setting of the shallow, cratonic Cherokee Basin. A statistical analysis of bottom-hole temperatures (BHTs) confirmed that (1) there is no significant change of temperature with season or through the 40 years of drilling and logging the wells in the area; and (2) the distribution of values is normal indicating they were recorded correctly on the rig within the instrumental precision of about 1 K. It was obvious from the large data set of nonequilibrium BHTs analyzed by depth and stratigraphic unit that they differed from drillstem test temperatures (DSTs) and modeled temperature- depth distributions based on heat conduction. At shallow depth (less than 500 m), BHT values as read from the logs are higher than ‘true’ formation temperature; in a depth range of 500–700 m, values scatter around a ‘true’ formation temperature; and at greater depths (up to 1,100 m), the uncorrected BHTs slightly underestimate the formation temperature. Different amounts of data scatter in the composite BHT-depth plots occur in different size areas, which also impacts the calculated geothermal gradients and empirical correction methods developed on the basis of these data. Although the BHTs in the 60×75 km area of Elk and Chautauqua counties scatter ±5–9°C around some mean value, seemingly the scatter can be reduced slightly when working with smaller areas, for example 10×10 km. A mapping approach made to investigate the variability of the 60×75-km BHT cluster in more detail showed part of the BHT scatter to be related to regional geology. Temperature residuals of the trend are on the order of ±2.5°C with some values as large as ±7.5°C. This provides an indication of variability of BHTs resulting from other influences, which might be different perturbations as a result of drilling practices and different shut-in times of the wells. In addition, some of the temperature highs are shown to be related to local, subtle anticlines developed in the sedimentary cover over faulted basement blocks and therefore contain signal. The separation of different effects on BHTs has implications on the reliability of geothermal gradient and heat-flow density estimations.

Surface heat flow and lithosphere thermal structure of the Rhenohercynian Zone in the greater Luxembourg region

Comprehensive knowledge of surface heat flow and subsurface temperature distribution is indispensable for the interpretation and quantification of crustal/mantle processes as well as for the evaluation of the geothermal potential of an area. In cases where subsurface temperature data are sparse, thermal modeling may be used as a tool for inferring the geothermal resource at depth but requires profound structural, geological, and petrophysical input data. The study area encompasses the Trier–Luxembourg Basin and the western realm of the Rhenish Massif, itself subdivided into the Ardennes region in the west as well as the Eifel and Hunsruck regions in the east. For the study area, 2-D steady-state and conductive thermal models were established based on geological models of lithosphere-scale which were parameterized using thermal rock properties including thermal conductivity, radiogenic heat production, and density. The thermal models are constrained by surface heat flow (qs) and the geophysically-estimated depth of the lithosphere–asthenosphere boundary (LAB). A qs of 75 ± 7 (2σ) mW m−2 was determined in the area. A LAB depth of 100 km, as seismically derived for the Ardennes, provides the best fit with the measured qs. Modeled temperatures are in the range of 120–125 °C at 5 km depth and of 600–650 °C at the Moho, respectively. The mantle heat flow amounts to ∼40 mW m−2. Possible thermal consequences of the 10–20 Ma old Eifel plume, which caused elevation of the LAB to 50–60 km depth, were modeled in a steady-state thermal scenario resulting in a qs of 91 mW m−2 in the Eifel region. Available qs values (65–80 mW m−2) are significantly lower and do indicate that the plume-related heating has not yet reached the surface in its entirety.

Evaluation of Geo-processes

A holistic understanding of the physicochemical processes induced by CO2 injection and storage in a reservoir is based on a geoscientific characterisation of the overall geological system consisting of reservoir rocks and cap rocks. It requires in a first step a comprehensive baseline characterisation (sedimentological, mineralogical, geochemical, mechanical, etc.) of pertinent parameters and conditions. To properly handle the large amount of different geoscientific information a Data Management System (DMS) was developed, which proved indispensable to conduct such a multi-disciplinary project. The DMS provides a tool for scientific process management, data analysis, integration and visualisation, data transfer and scheduling through specialised database systems and retrieval techniques, storage technology, and efficient data access.

Pairwise Comparison of Spatial Map Data

Map comparison/integration of spatial data has become important recently with the plethora of data being generated and accumulated. In many instances it is of interest to compare/integrate these data. The simplest comparative procedure is to overlay two maps and visually compare the areas of similarity and differences. This cursory examination is quick, but important aspects of the comparison may be overlooked. The simplest integration procedure is to overlay several maps and note the areas of correspondence on a resultant map. This type of comparison/integration is visual and subjective; quantatively, the degree of similarity may be expressed either (1) as a coefficient of overall similarity or (2) as a resultant map. The similarity coefficient gives an indication as to the goodness of correspondence and the resultant map shows where. Several techniques of pairwise map comparison have been utilized recently including bivariate and multivariate statistics, probability, AI/ES (Boolean logic), algebraic, and fuzzy set theory. A geothermal data set from southeastern Kansas is used to demonstrate pairwise map comparison with other spatial geological and geophysical data and to interpret local and regional conditions.

Temperature Analysis In The Mature Hydrocarbon Province Of Kansas: Utilizing A Large Database Of Well-Completion Histories

Commercially obtained bottom-hole temperatures (BHTs) were analyzed at a regional scale in the large, mature hydrocarbon province of Kansas in the US Midcontinent to investigate their usefulness for geothermal studies. The Petroleum Information Well-History Control System database was used to access BHTs recorded in exploration wells. BHTs were retrieved for the Mississippian (Lower Carboniferous) and the Cambro-Ordovician Arbuckle Group and plotted and contoured to create a regional temperature pattern for each stratigraphic unit. BHTs were assumed to be at or near the top of the units. These patterns then were compared visually to other geological features, such as sediment thickness and structure. An empirical BHT correction factor established to a depth of 1000 m in a subarea in southeastern Kansas was applied to the large data set to correct for drilling disturbance. Because of the poor resolution of the BHT data, on the order of iA5iaC, for a given stratigraphic unit, the corrected BHTs of the Arbuckle and Mississippian measured 100-400 m apart are similar over much of the area. The application of the empirical correction factor results in temperatures that approximate formation temperatures in the eastern area but deviate slightly in central and western Kansas. Despite those differences, the general BHT pattern in the sedimentary veneer is reflected in the regional geologic structure, suggesting the BHTs are affected mainly by the depth at which they were recorded. No correlation was evident between the temperature pattern and the type of Precambrian basement rock.