Abstract: An improved method for determining the magnitude of the minimum principle horizontal stress within a formation is disclosed and claimed herein. In particular, the inventive method involves the use of a wireline retrievable circumferential acoustic scanning tool during an open hole microfracture test to determine the magnitude of the minimum principle horizontal stress in the formation.

Abstract: This disclosure sets forth a fluid flow line which extends at one end from a fluid source at a pressure to be measured comprised of fluids contained within a well borehole, and the fluid flow line has a "J" shaped component to trap debris and trash to prevent it from flowing the full length of the fluid flow line and contacting a pressure transducer. The flow line is further defined by the threaded connection of two structural components making up the sonde wherein the components thread together and threads are sufficiently spaced apart to form an elongate helix as part of the flow path.

Abstract: An apparatus for induction logging is disclosed. By transmitting a sequence of pulses at many frequencies, the formation invaded zone diameter can be distinguished as a result of changes in resistivity. As higher frequencies are swept, dielectric constant varies with frequency and this variation is evident in chart form. An apparatus for controlled antenna field formation is also disclosed including a sonde construction involving antenna coils on the sonde with dielectric discs to reduce parasitic radiation.

Abstract: The present disclosure is directed to a formation test tool having similar, even identical, fist and second test probes which have supported snorkels thereon. They extend from the tool into a particular formation. One serves as an inlet and the other serves an outlet so that fluid can be removed from the formation, directed through the tool body, and returned to the formation through the other of the two snorkels. The fluid flow passes a test instrument which detects changes indicative of reduced well fluid invasion in the connate formation. A test procedure is also set forth for testing this fluid.

Abstract: An adaptive transversal filter is incorporated with an SP conductor extending through a logging cable to the surface from an SP electrode supported on a sonde. This logging cable is operated in a noisy environment and there is the risk of noise on the logging cable obscuring the SP signal. The SP signal is obtained at the surface and is passed through a filter system. One input to the filter system utilizes an AC ammeter connected to the AC power source for the logging cable and that signal is input to a multi-stage adaptive transversal filter. The filter output is a recreation of the noise imposed on the SP conductor and when summed with the SP output signal, provides a signal which is substantially noise free.

Abstract: An efficient spatial smoothing algorithm for filtering data while preserving spatial detail is obtained using the system (impulse response) function of the sensor. In contrast to the normal procedure for determining the filter coefficients for an arbitrary system function, this technique avoids the use of Fourier transforms. The spatial filtering coefficients are obtained analytically for the frequently applicable Gaussian system function. The efficiency of this procedure is illustrated by filtering discrete data. For realtime smoothing of nuclear log data, a filter length of five times the vertical resolution is required.

Abstract: A perforating gun assembly is set forth. It incorporates a swivel connected with a cable head assembly and a navigation system for determining the instantaneous angle of the tool with respect to a vertical reference. There are first and second spaced cages formed of sleeves supported on bearing assemblies. The sleeves support free wheeling rollers which engage the casing when the tool is in the slant hole region of the well. There is an eccentric which falls downwardly, i.e., pointing toward gravity, and thereby defines a vertical reference and hence a horizontal reference. This eccentric mounts an elongate tubular housing for the shaped charges. Initially, the angle of firing of the shaped charges is adjusted at the time of installation with respect to the horizon and that in turn is correlated to the formation of interest in the well borehole which is then perforated with perforations which are parallel to the formation bedding plane.

Abstract: A formation test tool is set forth in the present disclosure and has a snorkel on one side and upper and lower diametrically opposite back-up pistons on the opposite side. The back-up pistons are constructed with a back-up plate on the end of the back-up piston encircling and centered around a formation punch. The formation punch has a small diameter and specified length so that, during operation, the punch contacts the sidewall of the well borehole, and pressure is increased thereafter to force the punch into the formation until fracture failure occurs evidenced by a change in hydraulic pressure and a lurching movement of the back-up piston as the punch penetrates the formation. By knowing the diameter of the punch and by observing the hydraulic pressure necessary to obtain failure of the formation at the point of contact with the punch, data can be obtained which is indicative of the compressive strength of the formation.

Abstract: Apparatus for measuring the volume of gas present in a multiphase flow regime in a cased oil or gas well borehole and the amount, if any, of stratification thereof at a particular borehole depth. The apparatus includes a low energy gamma ray source and a sodium iodide detector located a very short distance from the source and separated by shielding material. Low energy gamma rays, unable to leave the well casing and return, are emitted from the source and scattered back from the multiphase production fluid to a detector comprising a sodium iodide crystal and photomultiplier tube. Both the source and detector are surrounded by rotatable slit collimators to provide sensitivity to azimuthal variations in gas volume percentage in the flow.

Abstract: A high pressure high temperature hermetically sealed electrical connector pin construction is set forth for use in down hole logging tools. On exposure to 28,000 psi at elevated temperatures, the present apparatus is able to handle such pressure and temperature cycling. Moreover, an elongate pin having two ends for forming electrical connections is used, the pin having a shoulder, a central threaded portion on one side of the shoulder and is formed of conductive metal that joins with a plastic body which is bonded thereto either by in situ molding to the pin or by an epoxy resin and the pin further threads to the body. In a multipin construction, the body is a circular insert for a surrounding cylindrical steel housing.

Abstract: A logging apparatus for measurement of earth formation resistivity is disclosed. The apparatus includes an elongated sonde having an insulated section and an electrically isolated conductive pad mounted for lateral extension into contact with a borehole wall. The electrically isolated conductive pad includes a plurality of current electrodes disposed longitudinally along the pad and a return electrode disposed on the reverse face thereof. A focussing section is utilized to provide varying depths of investigation by electrode current to preferably permit measurement of earth formation resistivity in the mudcake, flush zone, and uninvaded formation. In a preferred embodiment of the present invention, the conductive pad includes a pair of hingeably mounted sections which permit the apparatus to accommodate varying radii of curvature of boreholes.

Abstract: The present disclosure is directed to a shock absorbing device for threading in a tubing string for running delicate instruments into a well borehole where they are in near proximity to explosives which might otherwise be detonate. This particularly is important in a well borehole which is filled with a standing column of liquid which transmits the shock waves quite readily. This is a separate assembly which can be threaded in the tubing string and has a pin and box connection for that. Moreover, it is formed of an outer mandrel surrounding connected inner upper and inner lower mandrels; the inner mandrels define annular spaces for receiving shock absorbers defined by alternating thin layers of metal and rubber; the metal and rubber washers have different shock wave impedances and tend therefore to absorb shock waves traveling either upwardly or downwardly in the well borehole.

Abstract: A downhole tool for generating pressure pulses in a drilling fluid comprising an elongated body and a plurality of blades spaced around the body. The blades are each divided into an independent front section and rear section, forming a set of front sections and a set of rear sections, at least one of the set of front sections and the set of rear sections being mounted for rotation such that the front and rear sections are angularly displaceable relative to each other between a first position in which the sections are aligned and a second position in which the rear sections obstruct fluid flow between the front sections to generate a pressure pulse. The tool includes a means for generating a torque on the blade sections, and an escapement means which is radially movable to permit stepwise rotation of the blade sections, and thus to move the blade sections between the first and second positions.

Abstract: An apparatus and method for induction logging is disclosed. By transmitting a sequence of pulses at many frequencies, the formation invaded zone diameter can be distinguished as a result of changes in resistivity. As higher frequencies are swept, dielectric constant varies with frequency and this variation is evident in chart form. An apparatus for controlled antenna field formation is also disclosed.

Abstract: A method and apparatus for stimulating fluid production in a producing well wherein a well stimulating tool comprising a sealed tool housing with an acoustic transducer in the housing. The tool is run into a producing well on an electric wireline and placed at a depth opposite perforations in a producing zone. The sealed housing of the tool contains a liquid to couple and enable pulses of acoustic energy from the acoustic transducer to be transmitted through the housing into well formation fluids surrounding the housing to reduce the viscosity of the formation fluids by agitation and thereby enhance fluid flow from the formation into the producing well.

Abstract: A pressure responsive below packer valve apparatus which allows operation of a below packer valve through application of pressure to the wellbore annulus above the packer. The valve apparatus includes a crossover located in a tool string above the packer which communicates upper annulus pressure to a conduit inside the tool string. This conduit communicates annulus pressure to a valve mechanism below the packer. A selectively releasable mechanism such as a rupture disk communicates pressure to the valve mechanism once a threshold pressure is reached, thereby facilitating operation of the valve mechanism through application of annulus pressure.

Abstract: An electrode for use in the electrical investigation of a medium such as a borehole wall, comprises a sheet (32) of electrically resistive material having opposed first (34) and second (33) surfaces, one or more elongate electrical conductors (35,36) of low resistivity, an end face of each conductor abutting the first surface of the sheet (32) and means for sensing electric current passing through each conductor. In use, the second surface (33) of the sheet (32) is exposed to the medium to be investigated.

Abstract: A method of data conversion is set forth. In this system, the amplitude of a borehole sidewall response is recorded as a data record. This includes a sinusoidal representation of an interface. Several points on the sinusoidal curve are transformed in parameter space to represent dip and strike of the interface. Multiple point transform provides quality data so that noise on the signal has reduced impact. The transform is the Hough Transform into parameter space. This can be used with BHTV to provide acoustic data representing the sidewall of the well.

Abstract: A rigid bridle for supporting a current emitting logging tool in a sonde is set forth. The rigid bridle is formed of multiple segments of tubular members, normally formed of metal. At selected locations along the length thereof, they are interrupted by electrical insulators which prevent current flow along the length thereof. Moreover, the external surface is coated with first one and then the second layer of insulative material; three such units in serial assembly support a return current electrode for use in a current emitting logging tool. In an alternate form, a short electrical isolator joint is set forth which includes concentric metal members which are spaced from one another when assembled by insulative members positioned therebetween so that current flow along the length thereof is prevented.

Abstract: A magnetic mark on a cable is subject to loss of intensity. The present disclosure provides for remarking. It utilizes a detector which responds to passage of a magnetic mark on the cable. A coil for remarking is located at a specified and measured distance from the detector. Through the use of measuring wheels in contact with the cable providing data to a computer, the cable traverses from the detector to the marking coil, and a marker control circuit is timely operated to place a new mark on the cable. The new mark is placed coincident over the prior mark and has greater intensity to renew the magnetic marks on the cable.