Abstract: A borehole gravimetry system employs a pair of pressure transducers for lowering into a borehole along with a borehole gravity meter. The pressure transducers are spaced apart vertically within a pressure sonde for producing a pressure differential measurement of the wellbore fluid. A first of the transducers is hydraulically isolated from borehole fluid pressure while the second of the transducers is in hydraulic contact with the borehole fluid so as to be exposed to the borehole fluid pressure. The second transducer is thermally insulated from borehole temperature to achieve thermal time constant equalization between the pair of transducers. A pressure differential measurement and a gravity reading is taken for each of a plurality of vertical locations within the borehole as the borehole gravimetry system is advanced through the borehole and from these measurements bulk density is determined.

Abstract: A borehole logging system includes a borehole gravity meter and a resistivity logging tool. A borehole gravity log and a resistivity log are produced over a select depth interval in a borehole. The bulk density of the subsurface formation surrounding the borehole over the select depth interval is measured from the gravity log. The bulk resistivity of the formation surrounding the borehole over the select depth interval is measured from the resistivity log. The bulk density and bulk resistivity measurements are combined to derive a measurement of the residual oil saturation of the subsurface formation surrounding the borehole for the select depth interval.

Abstract: A method of identifying potential low water cut hydrocarbon producing zones in a sand or sandstone formation by logging the formation to determine its permeability and porosity values and generating from said two sets of values a log of specific surface areas of the formation. The aforesaid zones may be identified directly from the specific surface area log as being those regions in which the specific surface areas are about 500 m.sup.2 /cm.sup.3 bulk volume or more. Alternatively or additionally, the specific surface area log may be used to determine irreducible water saturation values of the formation which can then be compared with fractional water saturation values. The aforesaid zones are those in which the irreducible water saturation values approximate or exceed the fractional water saturation values.

Abstract: In drilling a borehole, true basement is distinguished from a dike or sill by logging the borehole with a gravimetric logging tool and with a formation density compensated logging tool. The difference between the density and the gravity, as determined by these logs is plotted as a function of depth over the interval extending above the point at which the drilling encountered the dense rock formation. The difference log so obtained distinguishes whether rock formation is true basement or a dense intrusion.

Abstract: A method for borehole gravimetric determination of residual oil saturation of a formation is described. In a preferred embodiment plural measurements of the local gravity are taken at each of spaced locations within a well and those departing more than a statistically determined distance from the mean of the measurements taken at a given location are deemed to be in error and are not used in calculation of the density of the formation at a given point.

Abstract: A radar transmitter directs a beam of microwve energy at a first frequency through the atmosphere. A gas seep in the atmosphere irradiated by the beam of microwave energy is excited to emit microwave energy at a second frequency characteristic of the particular species of gas. A radar receiver is tuned to produce video signals representative of the microwave energy at the second frequency. An amplitude discriminator measures the amplitudes of the video signals during each radar sweep as an indication of gas concentration in the seeps and counts the number of video signals during each radar seep as an indication of the size of the seeps.

Abstract: In the exploration for hydrocarbon gas, microwave energy is radiated from an antenna transported along a traverse above the surface of the earth. Microwave energy re-radiated from gas seeps is detected. Microwave energy reflected from hard targets along the traverse is also detected. Video monitors simultaneously display the detected re-radiated and reflected microwave energy. In this way, hydrocarbon gas seeps are displayed in relation to topographical features along the traverse.