F. W. Jones

Geothermics of the Williston Basin in Canada in relation to hydrodynamics and hydrocarbon occurrences

Over 8 400 bottom‐hole temperature (BHT) values from the Canadian part of the Williston Basin were analyzed and a temperature high was discovered in the Weyburn area of southeastern Saskatchewan. Geothermal gradients, thermal conductivities, and heat flow have been investigated for most of the Mesozoic‐Cenozoic clastic unit as well as the Upper Paleozoic carbonate‐evaporite unit. Regional heat flow variations with depth occur which are closely related to the hydrodynamics governed by the topography and geology. The blanketing effect of low‐conductivity shaly formations may cause a temperature anomaly in the south where the thickest Phanerozoic cover exists. However, the Weyburn high can be explained only partially in this way. Hydrodynamics has also contributed to formation of the temperature anomaly there. The process of forming the anomaly by the blanketing effect and hydrodynamics also contributed to oil deposition. There is a correlation between Mississippian oil occurrences in the southeastern part o...

The variability of heat flow both regional and with depth in southern Alberta, Canada: Effect of groundwater flow?☆

Abstract Detailed studies of terrestrial heat flow in southern and central Alberta estimated on the basis of an order of magnitude larger data base than ever used before (33653 bottom-hole temperature data from 18711 wells) and thermal conductivity values based on detailed rock studies and measured rock conductivities show significant regional and local variations and variations with depth. Heat flow values were estimated for each 3 × 3 township/range area (28.8 × 28.8 km). A difference in heat flow exists between Paleozoic and Mesozoic strata. Generally lower heat flow values are observed in the strata above the Paleozoic erosional surface (20–75 mW m−2). Much higher values are estimated for the Younger Paleozoic formations, with large local and regional variations between 40 and 100 mW m−2. Average heat flow values based on heat flow determinations below and above the Paleozoic surface that agree within 20% show an increase from values less than 40 mW m−2 in southern and southwestern Alberta to values as high as 70 mW m−2 in central Alberta. The predominance of regional downward groundwater flows in Mesozoic strata seem to be responsible for the generally observed heat flow increase with depth. The results show that the basin heat flow pattern is influenced by water movement and even careful detailed heat flow measurements will not give correct values of background steady-state heat flow within the sedimentary strata.

Terrestrial heat flow and geothermal gradients in relation to hydrodynamics in the Alberta basin, Canada

Abstract Geothermal gradients in the Alberta part of the Western Canadian sedimentary basin have been studied on the basis of 55,244 bottom-hole temperature values from 28,260 petroleum exploration wells. Gradient estimates for different depth and stratigraphic intervals together with a study of the heat conductivity distribution indicate both regional heat flow variations and variations with depth. The regional hydrodynamics of the basin strongl influences both grad ifT gradient and heat flow increase with depth in water recharge areas to the west and decrease with depth in discharge areas to the north and east. The results indicate that heat flow in the central part of the basin should be approximately equal to the deep crustal heat flow.

Heat flow and heat generation estimates for the churchill basement of the western canadian basin in Alberta, Canada

Abstract Heat flow through the sediments and temperatures of the Churchill province basement under the sedimentary cover are determined for 24 locations in the central part of the Prairies basin in Alberta where the vertical heat flux is approximately constant from the base of the sediments to the surface. The contribution to heat flow from heat generation in the sediments is also considered. The average heat flow through the sediments is found to be 71 mWm −2 ± 12 mWm −2 which is about 30 mWm −2 higher than in the neighbouring shield area of the Churchill province, and the contribution from heat generation in the sediments to the surface heat flow is only approximately 2.5 mWm −2 . The relationship between basement heat generation and heat flow is investigated, and it is found that the platform heat flow/heat generation values are in general higher than those from the Churchill province of the shield found by Drury 1985. Although for the platform and shield data, the reduced heat flow is about 40 mWm −2 and the slope is about 8 km, it is apparent that the platform data alone are not good enough to establish a precise relationship.

The temperature stabilization of a borehole

Analytic solutions for the temperature stabilization of both square and circular boreholes are considered. It is found that a previously published solution for a square borehole is incorrect in that it does not reproduce the initially assumed conditions. The correct analytic solution for a square well, as well as that for a circular well, indicates a much more rapid approach to the formation temperature. The temperature stabilization curves for a range of thermal diffusivity values are given.

Deep subpermafrost thermal regime in the Mackenzie Delta basin, northern Canada; analysis from petroleum bottom-hole temperature data

In our studies of the thermal regime of sediments of the young Mackenzie Delta in the southeastern part of the Beaufort-Mackenzie basin of northern Canada, we used thermal data from the base of the permafrost layer, together with temperature data from petroleum wells. By analyzing bottom-hole temperature (BHT) data, we found that the percentage correction, i.e., the percentage difference between BHT and equilibrium temperature, is less than 10% ((with 67% probability) for times exceeding 10 hours after circulation ended, regardless of circulation time. No correlation exists between the percentage correction and depths for the BHT data. Theoretical temperature-depth profiles were constructed from the individual heat flow Q, Q +δQ, and Q-δQ values (δQ is error of estimate of Q), the interval thermal conductivities, and a permafrost base temperature of 0°C. Estimates of Q were based on the maximum BHTs from depths >2.7 km. The measured and corrected BHT values for depths less than 1.5 km lie outside the rang...

The variation of heat flow density with depth in the prairies basin of western Canada

Bottom-hole temperature values from approximately 36,000 wells in Alberta. Saskatchewan and Manitoba, Canada, have been used to study thermal gradients and heat flow density there. It is found that variations of heat flow density with depth occur throughout the Prairies basin. Differences in heat flow density exist between the Mesozoic + Cenozoic and Paleozoic sediments and are related to the hydrodynamics which is controlled by the topography. The heat flow density through the Mesozoic + Cenozoic of the upper part of the section is less than that in the Paleozoic formations of the lower part of the section in recharge areas, but greater in discharge areas. A zone in which heat flow is approximately constant with depth extends down the central part of the basin between the recharge and discharge areas. Heat flowdensity in this zone lies between 60 mW m−2 and 80 mW m−2 and is thought to be representative of the deep crustal heat flow density. It is suggested that temperature variations on the Precambrian basement that are not depth related may be associated with anomalous heat flow regimes in the lower crust.

Terrestrial heat-flow density estimates for the Jeanne D'Arc Basin, offshore Eastern Canada

Corrected bottom‐hole temperatures from 35 wells, together with measured and assumed rock thermal conductivities, are used to estimate linear geothermal gradients and effective thermal conductivities in the Jeanne d’Arc Basin in offshore eastern Canada. Heat‐flow density values calculated for each well location indicate that heat‐flow density is slightly higher in the deeper northern part of the basin than in the southern part. It appears that the heat‐flow density distribution is affected by fluid motion within the sediments and not by heat generation or basement topography. Dehydration is suggested as the mechanism that produces the fluid flow pattern that influences the heat‐flow density distribution in the basin, and a simple fluid flow model of the Jeanne d’Arc Basin is presented.

A statistical analysis of bottom-hole temperature data in southern Alberta

When bottom‐hole temperatures (BHT) are plotted as functions of depth for different areas, the plots exhibit differences in the spread of the data. The regional variations in spread in southern Alberta were mapped in detail on the basis of 33 653 BHT data from 18 711 wells. There are local areas with anomalously high spread values, and the spread generally increases westward toward the Disturbed Belt. Also, the spread values for data below the Paleozoic erosional surface are greater than those above. Greater spread in the data appears to be associated with the occurrence of faults, steeply dipping strata of different thermal conductivity, and rough topography. The increased spread associated with faults and steeply dipping strata is probably due to water movement. This suggests that bottom‐hole temperatures may provide information about subsurface structure and phenomena as well as information on temperature.

The response of perturbation and induction arrows to a three-dimensional buried anomaly

A numerical model is employed to calculate theoretical perturbation and induction arrows for a spatially confined three‐dimensional (3-D) conductivity anomaly located at various depths below the surface of the earth for two source periods. The results indicate that the magnitudes of the induction arrow decrease as the anomaly depth increases and the arrows point toward the conductive anomaly even at great depth below the surface. It is found that the extent of the anomalous induced currents depends upon the depth of the inhomogeneity and on the source field period. The (p+q) perturbation arrow can be used to outline the spatial extent of the anomaly, and the (p+q) quadrature‐phase arrows better indicate the spatial extent than the in‐phase arrows if the source period is not an optimum one.