Abstract: In accordance with illustrative embodiments of the present invention, methods for processing well logging data comprises deriving measurements of a plurality of earth formations parameters and combining these measurements in a new manner to enable interpretation of shales and shaly sand type formations. More particularly, measurements of a plurality of the hydrogen index, bulk density, radially deep and shallow resistivity, spontaneous potential, acoustic travel time and natural formation radioactivity content are made and combined in a manner to produce data useful in evaluating shales and shaly sand type formations.

Abstract: In accordance with illustrative embodiments of the present invention, methods for processing well logging data comprises deriving measurements of a plurality of earth formations parameters and combining these measurements in a new manner to enable interpretation of shales and shaly sand type formations. More particularly, measurements of a plurality of the hydrogen index, bulk density, radially deep and shallow resistivity, spontaneous potential, acoustic travel time and natural formation radioactivity content are made and combined in a manner to produce data useful in evaluating shales and shaly sand type formations.

Abstract: In order to determine dips of subsurface formations more reliably, a dipmeter tool with three or more transducers, spaced circumferentially around the borehole wall, is used and the transducer outputs are correlated in a novel way to provide redundant indications of displacements between the depths at which respective transducers intercept a given layer. These redundant displacements are processed to single out at each given level only those displacement pairs which result in the most consistent dips over several mutually overlapping depth intervals called zones. Consistency is established in each zone without regard to a neighboring zone, to avoid any long range bias.

Abstract: In accordance with illustrative embodiments of the present invention, techniques are shown for processing well logging data to provide improved results. More particularly, a technique is disclosed for determining the reliability of well logging computations. Another technique is disclosed for making a preliminary pass of the well logging data to automatically select certain input parameters. Still another technique is disclosed for automatically determining the minimum possible hydrocarbon density for each formation level. This last technique is contrasted with the prior art technique which set one minimum value for the entire length of a borehole.

Abstract: The disclosed technique finds and shows the attitude of one or more bedding surfaces of an underground earth formation which intersect a borehole in that formation. It starts with a log for each respective path along which a multipath investigating tool takes well logging measurements while being passed through the borehole. A set of a dip and an azimuth signal is produced for each of a number of assumed bedding surfaces which intersect, at a respective number of different attitudes, the same point at the centerline of the tool for a given depth of the tool in the borehole. Portions of the logs for the respective paths chosen by reference to their intersection with each assumed bedding surface are combined so as to get a measure of the mutual degree of fit between the combined log portions. A two-dimensional map is then produced, made up of such measures of fit for the different assumed bedding surfaces at a given depth in the borehole.

Abstract: In accordance with an illustrative embodiment of the present invention, a technique is disclosed for determining a characteristic of an earth formation by irradiating the formation with a source of neutrons and measuring the resulting neutron population at two different spacings from the source. Each neutron population measurement is converted into a signal which is related to the formation porosity corrected for environmental effects. The two converted signals are then compared with the porosity derived from the ratio of the two neutron population measurements in order to obtain an indication of the presence of gas in the formation.

Abstract: In accordance with an illustrative embodiment of the present invention, a technique is disclosed for determining the porosity of an earth formation by irradiating the formation with a source of neutrons and measuring the resulting neutron population at a given spacing from the source. The neutron population measurement is converted into a signal which is related to the formation porosity in accordance with the relationship:N = A[P+.alpha.(1-P)].sup.-.sup.x,where N is the measured neutron population; A is the neutron population measured in fresh water; P is the porosity; .alpha. is an empirically derived coefficient for which the variation of log N as a function of log [P+.alpha.(1-P)] is represented by a substantially straight line; and x is a coefficient representing the slope of this straight line.

Abstract: In accordance with an illustrative embodiment of the present invention, a method and apparatus for logging an earth formation of interest is disclosed that provides an indication of the presence of permeable and impermeable zones in the earth formation.