1. Field of the Invention
The present invention relates to methods for compensating measured earth surface temperatures for the effect of skyward conditions upon such temperatures. More particularly, the present invention relates to methods for using temperatures measured in a skyward direction for compensating measured temperatures of the earth's surface. The earth surface temperatures compensated according to the method of the present invention are useful for determining subsurface features, such as the presence or absence of oil, gas, or mineral deposits.
2. Description of Pertinent Art
It has been known since at least the Middle Ages that the earth's surface at locations above mineral deposits, such as metal ores, is warmer than the earth's surface above locations where such mineral deposits do not occur. Early reports describe the selective melting of frost at locations above mineral deposits, while the frost at other locations, where no mineral deposits were found, remained unmelted.
In U.S. Pat. No. 4,476,716 (Fons), incorporated by reference into this application in its entirety, I disclosed methods for predicting the likelihood that oil or gas deposits are present at unexplored depths below selected locations on the earths surface. These methods were based upon the discovery that the temperature of the earth at a given depth below a location above an oil or gas deposit tends to be lower than temperatures at the same depth at other locations in the same geographic area where oil or gas deposits do not exist.
One method taught in U.S. Pat. No. 4,476,716 for predicting the likelihood of an oil or gas deposit below a location comprises: determining a first temperature (Tq) at a first known depth beneath a selected location; determining a second temperature, (Tr.), representative of the average temperature for the first known depth within a geographic area within which the location is situated; and determining a temperature difference, .DELTA.T=Tq-Tr., where, for a negative value of .DELTA.T, it is likely that an oil or gas deposit is present beneath the location. As exemplified by claims 11 and 12 of U.S. Pat. No. 4,476,716, the method may be applied where the first known depth is about the surface of the earth. The accuracy of predictions made using these methods are dependent upon the accuracy of temperature data at the locations under study. At Col. 5, lines 14-18, of U.S. Pat. No. 4,476,716 I stated, "Where surface and ambient temperatures are very accurately determined, temperature differences in the range of 1.degree. F. may be used to predict the presence of oil or gas deposits at selected locations." In U.S. Pat. No. 4,476,716 I disclose that accurate surface temperature data and atmospheric temperature may be obtained for some locations in the form of annual average temperatures from Geological and Meteorological surveys.
In U.S. Pat. No. 5,524,483 (Fons), incorporated herein in its entirety by reference, I disclose methods for predicting the likelihood of the presence of oil or gas deposits beneath locations within a geographic area on the earth's surface employing earth surface temperatures at the locations. The methods disclosed in U.S. Pat. No. 5,524,483 comprise measuring earth surface temperatures at a plurality of points, (each having similar surface features), during a time period during which ambient conditions, (for example: ambient temperatures, incident radiation, degree of cloud cover, precipitation, wind and atmospheric humidity and clarity), are similar for minimizing the variability of earth surface temperatures from point to point due to changes in such ambient conditions. Points having lower than average earth surface temperatures were identified as being more likely to have oil or gas deposits beneath them than were other points having higher than average earth surface temperatures.
In U.S. Pat. No. 5,281,024 (Fons), incorporated herein in its entirety, I disclose methods for locating deposits of soil having high percolation rates in areas having both permeable and impermeable soils employing earth surface temperature measurements. According to the methods of U.S. Pat. No. 5,281,024, locations having higher earth surface temperatures are more likely to have permeable soils present than are locations in the same area having higher earth surface temperatures.
Earth surface temperatures are affected not only by seasonal changes in temperature, but also by more immediate factors, such as diurnal effects, variation in topographical features, including soil type, soil moisture, reflectance/emissivity of the earth's surface, vegetative cover, elevation above/below sea level, grade and other surface features as well as changes in ambient conditions such as incident radiation (sunlight), ambient temperatures, atmospheric humidity, wind desiccation, cloud cover, atmospheric clarity, and precipitation,. These factors tend to create variations in measured earth surface temperatures which mask any temperature differences between two or more locations arising from the presence or absence of oil or gas deposits, or of other subsurface features beneath the locations. While time averages, such as average annual earth surface temperatures as disclosed in U.S. Pat. No. 4,476,716, tend to eliminate the masking effect of these factors such that earth surface temperatures differences due to the presence or absence of oil or gas deposits or other subsurface features can be observed, obtaining such time average temperature data is not economically or functionally practical. Selecting a time period during which these factors change little, as disclosed in U.S. Pat. No. 5,524,483, allows collection of earth surface temperature data which is useful for determining subsurface features. However, as will be seen below, ambient conditions tend to change, and thus corrupt the earth surface temperature data collected, even during short time periods.
A practical method for acquiring earth surface temperature data relatively unaffected by the above factors, especially changes in ambient conditions, and which is useful for determining the presence or absence of subsurface features, such as oil, gas or mineral deposits, is desirable