Tunisian geothermal data from oil wells

Geophysics ◽  
1988 ◽  
Vol 53 (11) ◽  
pp. 1479-1487 ◽  
Author(s):  
Hamed Ben Dhia
Keyword(s):  
Steady State ◽  
Statistical Method ◽  
Empirical Relation ◽  
Geothermal Gradient ◽  
Petroleum Exploration ◽  
Formation Temperature ◽  
Geothermal Gradients ◽  
Drill Stem ◽  
Bottom Hole ◽  
Direct Measurements

Since direct measurements of steady‐state temperatures are not readily available in Tunisia, a geothermal investigation has been made using 1319 values of bottom‐hole temperatures (BHTs) obtained from 217 petroleum exploration wells. An empirical relation based on the differences between BHT and DST (drill stem tests) was used to correct BHTs and estimate geothermal gradients. The estimated geothermal gradient of the country varies between 21 and 52 °C/km. A few regions with similar gradients have been identified, and similarities between gradient contours and the main structural directions are noted. Furthermore, for 25 points from 12 wells, it was possible to apply the Horner‐plot method to determine the equilibrium formation temperature (Tf). Comparison of Tf values with those calculated by the estimated gradients reveals a good correlation (r = 97 percent) between the two estimates. This agreement permits greater confidence in the statistical method used and consequently in the estimated gradients for the whole country.

VITRINITE PALAEOTHERMOMETRY OF OFFSHORE EXPLORATION WELLS, TASMANIA

1989 ◽  
Vol 29 (1) ◽  
pp. 130
Author(s):  
P.W. Baillie ◽  
N.J. Russell
Keyword(s):  
Sedimentary Basins ◽  
Computer Programs ◽  
Petroleum Exploration ◽  
Geothermal Gradients ◽  
Bottom Hole ◽  
History Of ◽  
Reflectivity Data ◽  
Temperature Time ◽  
Heating Duration ◽  
Offshore Petroleum

Over the last three decades organic metamorphism (coalification), as indicated by changes in vitrinite reflectivity, has been regarded as a function of both temperature and heating duration. This temperature- time concept of coalification has been developed into sophisticated computer programs to model the palaeo- geothermal history of sedimentary basins. However, several papers, published over the last six years, have presented evidence to support the view that, for heating times in excess of 0.001- 1 Ma, vitrinite reflectivity constitutes an absolute palaeogeothermometer. This proposition is broadly supported by a comparison between corrected bottom- hole temperature (BHT) and vitrinite reflectivity data from offshore petroleum exploration wells drilled in Tasmanian waters. Most of the corrected BHT/vitrinite reflectivity data pairs plot on, adjacent to or between two of the published vitrinite temperature/reflectance trends. Although these data indicate that some formations are at, or near, maximum palaeotemperature, there is clear evidence to suggest that many samples, in particular those from formations in the deeper well sections, have cooled significantly below maximum palaeotemperature. It appears that present- day geothermal gradients for some of the wells, based on corrected BHT data, are much less than maximum palaeogeothermal gradients inferred from the vitrinite depth/reflectance relationship.

Calculation of organic maturation levels for offshore eastern Canada—implications for general application of Lopatin's method

1984 ◽  
Vol 21 (4) ◽  
pp. 477-488 ◽  
Author(s):  
D. R. Issler
Keyword(s):  
Heat Flow ◽  
Correlation Coefficient ◽  
Drilling Fluid ◽  
Vitrinite Reflectance ◽  
Geothermal Gradient ◽  
Scotian Shelf ◽  
Geothermal Gradients ◽  
Temperature Conditions ◽  
Bottom Hole ◽  
Correction Technique

Recorded maximum bottom-hole temperatures may vary significantly from true formation temperatures because of the effects of drilling fluid circulation. A theoretical temperature correction technique was applied to log-heading data to compute 191 static temperatures for 64 wells on the Scotian Shelf. A linear regression, performed on 140 computed temperatures, produced an average geothermal gradient of 2.66 °C/100 m; correlation coefficient 0.97. A geothermal gradient map constructed from the corrected data shows that areas of thicker sediment accumulation are marked by high geothermal gradients (e.g., Abenaki, Sable subbasins), whereas areas of shallow basement coincide with low gradients (e.g., LaHave Platform, Canso Ridge).It is proposed that the major control on the distribution of Scotian Shelf geothermal gradients is the thermal conductivity of the sediments. Radiogenic heat production within the sediments and subsurface fluid movement probably contribute to a lesser extent. Within the basins, higher heat flow due to thick salt accumulations at depth and the overall low conductivity of sediments above the salt lead to higher geothermal gradients. Low geothermal gradients in shallow basement areas are caused by the lack of salt and the relatively high conductivity of overlying sediments.A technique for calculating maturation levels of organic matter based on Lopatin's method and corrected bottom-hole temperatures was developed for the Scotian Shelf. A geologic model is constructed by considering the burial history of sediment for time invariant heat flow. From this, TTI (time–temperature index) values are derived to give the maturity level for specific sedimentary horizons. A comparison of 106 calculated TTI values with vitrinite reflectance measurements for 15 wells established a calibration of this technique for the Scotian Shelf. A correlation coefficient of 0.95 was obtained for the relation log TTI = 6.1841 log R0 + 2.6557.Maps showing the depth to calculated vitrinite reflectance values of 0.60 and 0.70% were constructed for the Scotian Shelf. It appears that burial rate, in addition to temperature, controls the location of various maturation levels. As one moves seaward, younger sediments increase in maturity and the oil window thickens. At equivalent depths, sediments at the basin margins are more mature than those farther seaward in the deeper parts of the basin. Sediments of the Canso Ridge area and over much of the LaHave Platform, excluding local downfaulted basins, have not attained sufficient maturity to have generated significant quantities of oil.TTI calibrations were established for the Labrador Shelf, the Grand Banks of Newfoundland, and the Canning Basin of Western Australia as above. Results indicate that tectonic history plays an important role in the calibration and that the slope of calibration lines may represent the departure from true time–temperature conditions in the modeling. Changes in heat flow with time lead to incorrect estimates of maturity when present-day geothermal gradients are used to approximate past temperature conditions. Also, uncertainties in the amount of erosion produce error in maturity estimates. The Scotian Shelf TTI calibration may be applicable to much of offshore eastern North America and parts of offshore western Europe and Africa.

Geothermal energy potential in the Hinton–Edson area of west-central Alberta

1985 ◽  
Vol 22 (3) ◽  
pp. 369-383 ◽  
Author(s):  
H.-L. Lam ◽  
F. W. Jones
Keyword(s):  
Geothermal Energy ◽  
Water Movement ◽  
Geothermal Gradient ◽  
Hot Water ◽  
Petroleum Exploration ◽  
Low Grade ◽  
Energy Potential ◽  
Bottom Hole ◽  
Geothermal Potential ◽  
Water Analyses

The Hinton–Edson area, located about 200 km west of Edmonton in Alberta, coincides with a geothermal anomaly of relatively high average geothermal gradient (~36 °C/km). The anomaly was discovered by Lam et al. during a study of a large number of bottom-hole temperatures. The high gradient and the thick sedimentary section in the area (4–6 km) provide a possible low-grade geothermal energy source for the growing population centres and industry. A survey of petroleum exploration data in the area has been made to determine if aquifers exist from which hot water may be recovered with reasonable flow rates and salinities for low-grade geothermal use. The results show that aquifers with prospective geothermal potential exist in the porous carbonate rocks of the Mississippian and Upper Devonian. Also, water movement is inferred from formation-water analyses, and this supports the suggestion that the geothermal anomaly is caused by the movement along fault planes of water that has been heated at depth.

scholarly journals Evaluation of geothermal energy resources in parts of southeastern sedimentary basin, Nigeria

2021 ◽  
Vol 23 (1) ◽  
pp. 195-211
Author(s):  
I.M. Okiyi ◽  
S.I. Ibeneme ◽  
E.Y. Obiora ◽  
S.O. Onyekuru ◽  
A.I. Selemo ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Heat Flow ◽  
Curie Point ◽  
Geothermal Energy ◽  
Sedimentary Basin ◽  
Geothermal Gradient ◽  
Geothermal System ◽  
Magnetic Vector ◽  
Geothermal Gradients ◽  
Vector Inversion

Residual aeromagnetic data of parts of Southeastern Nigerian sedimentary basin were reduced to the equator and subjected to magnetic vector inversion and spectral analysis. Average depths of source ensembles from spectral analysis were used to compute depth to magnetic tops (Z), base of the magnetic layer (Curie Point t Depth (CPD)), and estimate geothermal gradient and heat flow required for the evaluation of the geothermal resources of the study area. Results from spectral analysis showed depths to the top of the magnetic source ranging between 0.45 km and 1.90 km; centroid depths of 4 km - 7.87 km and CPD of between 6.15 km and 14.19 km. The CPD were used to estimate geothermal gradients which ranged from 20.3°C/km to 50.0°C/km 2 2 and corresponding heat flow values of 34.9 mW/m to 105 mW/m , utilizing an average thermal conductivity -1 -1 of 2.15 Wm k . Ezzagu (Ogboji), Amanator-Isu, Azuinyaba, Nkalagu, Amagunze, Nta-Nselle, Nnam, Akorfornor environs are situated within regions of high geothermal gradients (>38°C/Km) with models delineated beneath these regions using 3D Magnetic Vector Inversion, having dominant NW-SE and NE-SW trends at shallow and greater depths of <1km to >7 km bsl. Based on VES and 2D imaging models the geothermal system in Alok can be classified as Hot Dry Rock (HDR) type, which may likely have emanated from fracture systems. There is prospect for the development of geothermal energy in the study area. Keywords: Airborne Magnetics, Magnetic Vector Inversion, Geothermal Gradient, Heat Flow, Curie Point Depth, Geothermal Energy.

scholarly journals Contribution of human melanopsin retinal ganglion cells to steady-state pupil responses

2010 ◽  
Vol 277 (1693) ◽  
pp. 2485-2492 ◽  
Author(s):  
Sei-ichi Tsujimura ◽  
Kazuhiko Ukai ◽  
Daisuke Ohama ◽  
Atsuo Nuruki ◽  
Kazutomo Yunokuchi
Keyword(s):  
Steady State ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Pupil Diameter ◽  
Retinal Ganglion ◽  
Silent Substitution ◽  
Conventional View ◽  
Rods And Cones ◽  
Direct Measurements ◽  
Stimulation System

The recent discovery of melanopsin-containing retinal ganglion cells (mRGCs) has led to a fundamental reassessment of non-image forming processing, such as circadian photoentrainment and the pupillary light reflex. In the conventional view of retinal physiology, rods and cones were assumed to be the only photoreceptors in the eye and were, therefore, considered responsible for non-image processing. However, signals from mRGCs contribute to this non-image forming processing along with cone-mediated luminance signals; although both signals contribute, it is unclear how these signals are summed. We designed and built a novel multi-primary stimulation system to stimulate mRGCs independently of other photoreceptors using a silent-substitution technique within a bright steady background. The system allows direct measurements of pupillary functions for mRGCs and cones. We observed a significant change in steady-state pupil diameter when we varied the excitation of mRGC alone, with no change in luminance and colour. Furthermore, the change in pupil diameter induced by mRGCs was larger than that induced by a variation in luminance alone: that is, for a bright steady background, the mRGC signals contribute to the pupillary pathway by a factor of three times more than the L- and M-cone signals.

Estimation of formation temperature from bottom‐hole temperature measurements: COST ♯1 well, Norton Sound, Alaska

Geophysics ◽  
1988 ◽  
Vol 53 (12) ◽  
pp. 1619-1621 ◽  
Author(s):  
S. Cao ◽  
C. Hermanrud ◽  
I. Lerche
Keyword(s):  
Thermal Conductivity ◽  
Numerical Method ◽  
Time Scale ◽  
Efficiency Factor ◽  
Diffusion Time ◽  
Formation Temperature ◽  
Temperature Estimation ◽  
Bottom Hole ◽  
Free Parameters ◽  
Borehole Temperature

We recently developed a numerical method, the Formation Temperature Estimation (FTE) model, to determine formation temperatures by inversion of borehole temperature (BHT) measurements (Cao et al., 1988a). For more than two BHT measurements, the FTE model can estimate (1) true formation temperature [Formula: see text], (2) mud temperature [Formula: see text] at the time the mud circulation stops, (3) thermal invasion distance R into the formation before the formation is at the true formation temperature, (4) formation thermal conductivity K perpendicular to the borehole, and (5) efficiency factor F for mud heating in the borehole after mud circulation has stopped. The method optimizes three free parameters: τ (diffusion time‐scale), ε (scaling parameter related to the thermal invasion distance R), and [Formula: see text] (normalized efficiency factor for mud heating.

scholarly journals Relation between Sub-grain Size and Dislocation Density During Steady-State Dislocation Creep of Polycrystalline Cubic Metals

2018 ◽  
Vol 7 (4) ◽  
pp. 26 ◽  
Author(s):  
Manabu Tamura
Keyword(s):  
Grain Size ◽  
Steady State ◽  
Dislocation Density ◽  
Martensitic Steel ◽  
Empirical Relation ◽  
Dislocation Creep ◽  
Theoretical Relation ◽  
Cross Sectional ◽  
Cubic Metals ◽  
Polycrystalline Metals

The sub-grain size, d, during steady-state dislocation creep of polycrystalline metals is theoretically formulated to be inversely proportional to the dislocation density, ρ, which is defined as the number of dislocations swept out of a sub-grain divided by the cross-sectional area of the sub-grain. This dislocation density differs from the typically observed dislocation density inside a sub-grain after unloading, ρ_ob. In the current work, the ρ_ob values inside sub-grains in steadily crept specimens of Al, Cu, Fe, Fe–Mo alloy, austenitic stainless steel, and high-Cr martensitic steel reported in the literature were used to evaluate the relation ρ_ob=ηρ. It was confirmed that η≈1 for pure metals (regardless of the type of metal) crept at high temperatures and low stresses or for long durations and η&gt;1 for Mo-containing alloys and martensitic steel crept at low temperatures and/or high stresses. Moreover, it is suggested that the condition η&gt;1 corresponds to a state of excess immobile dislocations inside the sub-grain. The theoretical relation d_ob (≈d)∝η∙〖ρ_ob〗^(-1), where d_ob is the observed sub-grain size, essentially differs from the well-known empirical relation d_ob∝〖ρ_ob〗^(-0.5).

Inversion of bottom‐hole temperature data: The Pineview field, Utah‐Wyoming thrust belt

Geophysics ◽  
1988 ◽  
Vol 53 (5) ◽  
pp. 707-720 ◽  
Author(s):  
Dave Deming ◽  
David S. Chapman
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Heat Flow ◽  
Random Noise ◽  
Synthetic Data ◽  
Element Model ◽  
Geothermal Gradient ◽  
Oil Field ◽  
Conductive Heat ◽  
Bottom Hole

The present day temperature field in a sedimentary basin is a constraint on the maturation of hydro‐carbons; this temperature field may be estimated by inverting corrected bottom‐hole temperature (BHT) data. Thirty‐two BHTs from the Pineview oil field are corrected for drilling disturbances by a Horner plot and inverted for the geothermal gradient in nine formations. Both least‐squares [Formula: see text] norm and uniform [Formula: see text] norm inversions are used; the [Formula: see text] norm is found to be more robust for the Pineview data. The inversion removes random error from the corrected BHT data by partitioning scatter between noise associated with the BHT measurement and correction processes and local variations in the geothermal gradient. Three‐hundred thermal‐conductivity and density measurements on drill cuttings are used, together with formation density logs, to estimate the in situ thermal conductivity of six of the nine formations. The thermal‐conductivity estimates are used in a finite‐element model to evaluate 2-D conductive heat refraction and, for a series of inversions of synthetic data, to assess the influence of systematic and random noise on the inversion results. A temperature‐anomaly map illustrates that a temperature field calculated by a forward application of the inversion results has less error than any single corrected BHT. Mean background heat flow at Pineview is found to be [Formula: see text] (±13 percent), but is locally higher [Formula: see text] due to heat refraction. The BHT inversion (1) is limited by systematic noise or model error, (2) achieves excellent resolution of a temperature field although resolution of individual formation gradients may be poor, and (3) generally cannot detect lateral variations in heat flow unless thermal‐conductivity structure is constrained.

PETROLEUM EXPLORATION IN THE PROTEROZOIC BEETALOO SUB-BASIN, NORTHERN TERRITORY

1994 ◽  
Vol 34 (1) ◽  
pp. 674 ◽  
Author(s):  
Kevin Lanigan ◽  
Shane Hibbird ◽  
Sandy Menpes ◽  
John Torkington
Keyword(s):  
Oil And Gas ◽  
Northern Territory ◽  
Petroleum Exploration ◽  
Hydrocarbon Potential ◽  
Petroleum Potential ◽  
Drill Stem ◽  
Gas Potential ◽  
Unknown Sequence

Exploration over Roper Group outcrop in the McArthur Basin prompted Pacific Oil & Gas to investigate the petroleum potential of the Beetaloo Sub-basin, a 15 000 km2 Proterozoic depression concealed beneath Phanerozoic cover. Since 1989 drilling and seismic has identified a broadly flat-lying sequence with uplifted, eroded margins. A 3 500 m composite Proterozoic section consisting of three sandstone-to-mudstone sequences has been drilled. The lower two sequences comprise conformable units of the Mesoproterozoic upper Roper Group and unconformably overlying them is a previously unknown sequence comprising the informally labelled 'Jamison Sandstone' and 'Hayfield Mudstone', probably of Neoproterozoic age.Organic-rich intervals in the Roper Group mudstones range one to three per cent TOC in the Kyalla Member, and two to seven per cent TOC in the 'Middle' Velkerri Formation. Across most of the sub-basin the oil window lies within the Kyalla Member around 900–1350 m, while the 'Middle' Velkerri Formation is around 2 500 m and well into overmaturity, but may still have potential for gas. Potential reservoirs in the Bessie Creek, Moroak and 'Jamison' Sandstones, and in sandy units within the mudstones, are compromised by diagenesis, but porosities of up to 20 per cent and permeabilities of tens and rarely hundreds of millidarcies have been measured. Encouraging shows were observed in many of these intervals, and small quantities of oil and gas have been recovered in drill stem tests. With only a few targets drilled to date, this frontier area requires more exploration before its hydrocarbon potential can be adequately assessed.

Geothermal gradients in the Hinton area of west-central Alberta

1982 ◽  
Vol 19 (4) ◽  
pp. 755-766 ◽  
Author(s):  
H. L. Lam ◽  
F. W. Jones ◽  
C. Lambert
Keyword(s):  
Hot Springs ◽  
Rocky Mountain ◽  
Geothermal Gradient ◽  
Temperature Data ◽  
Petroleum Exploration ◽  
Well Logs ◽  
Thermal Gradients ◽  
Disturbed Region ◽  
West Central ◽  
Exploration Well

Temperature data from petroleum exploration well logs of 3360 wells in a region of west-central Alberta are used to estimate thermal gradients. A relatively high geothermal gradient (~36 °C/km) of oblong shape located near Hinton is observed. The axis of the anomaly strikes approximately southwest–northeast and passes through the Miette Hot Springs area. It appears that water is heated at depth in the Rocky Mountain disturbed region and travels eastward and toward the surface along fault planes.

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