Line integral method of magneto-electric exploration

A method of locating oil, gas, minerals, or geothermal energy deposits comprising the steps of:

• a. selecting a plurality of adjacent or over-lapping closed traverses enclosing areas to be investigated, preferably all substantially of the same area-magnitude
• b. measuring the total earth magnetic field intensity H.sub.t at a plurality of stations numbered from 1 to n along each closed traverse
• c. evaluating the line integral LI defined by ##EQU7## around each of the closed traverse, wherein ds is an elementary length of the profile, .alpha. is the angle between H.sub.t and ds, and ##EQU8## denotes the algebraic summation of n terms of the form H.sub.t.ds:cosine .alpha. evaluated in the series of intervals 1-2, 2-3, . . . . . (n-1)-n, n-1,
• d. plotting the values of LI so obtained at the center of each of the areas surveyed for the purpose of evaluating the presence and the areal extent of the deposits sought, positive values of LI evaluated along the closed traverses in a clockwise direction are indicative of mineral deposits giving rise to upward electrotelluric currents such as are generated by geothermal energy, the aforesaid relationship between the polarity of LI and the electrotelluric current flow direction being reversed when the line integration is performed counterclockwise.

A method of locating oil, gas, minerals, or geothermal energy deposits comprising the steps of:

• a. selecting a plurality of long and substantially parallel traverses all oriented in the same direction and another plurality of such traverses intersecting the first set of traverses substantially at right angle and covering an area under investigation
• b. recording continuously along such traverses the total intensity H.sub.t of the earth magnetic field
• c. evaluating the line integral segment
• LI = .intg. H.sub.t .sup.. ds .sup.. cosine .alpha.
• along each intercept between the two groups of traverses, wherein ds is an elementary length of the traverse, .alpha. is the angle between H.sub.t and ds and ds and ##EQU9## denotes the algebraic summation of n terms of the form H.sub.t .ds.cosine .alpha. evaluated in series of intervals 1-2, 2-3, . . . . (n-1)-n, n-1
• d. evaluating the closed line integrals LI.sub.c around each mesh grid formed by the two groups of traverses by adding algebraically the four LI's values around each grid
• e. plotting the values of LI.sub.c so obtained at the centers of each of the mesh grid for the purpose of evaluating the presence and the areal extent of the deposits sought, positive values of LI evaluated along the closed traverses in a clockwise direction are indicative of mineral deposits giving rise to downward flow of electrotelluric currents such as are generated by hydrocarbon accumulations, whereas negative values of LI are upward electrotelluric currents such as are generated by geothermal energy, the aforesaid relationship between the polarity of LI and the electrotelluric current flow direction being reversed when the line integration is performed counterclockwise.

A method of locating oil, gas, minerals, or geothermal energy deposits by intepreting maps of the total earth magnetic field intensity comprising the steps of:

• a. gridding the area of interest on such maps and reading the magnetic field values A at each grid apex
• b. transferring said values to computer cards or to magnetic tape for computer processing
• c. evaluating the line integrals LI (I, J) around each four mesh grid by
• LI (I, J) = A (I, J+1) + A (I, J+2) + A (I, J+3) + A (I, J+4) + A (I+2,2, 4) + A (I+3, J+4) - A (I+4, J+3) - A (I+4, J+2) - A (I+4, J+1) - A (I+3, J) - A (I+2, J) - A (I+1, J) - 3.0 * [ A (I, J+4) - A (I+4, J)]
• wherein A is the total earth magnetic field intensity at points of row number values I to I + 4 and of column number values J to J + 4.
• d. plotting the values of LI so obtained at the center of each of the mesh grid for the purpose of evaluating the presence and the areal extent of the deposits sought.