Abstract: A physical condition in a well bore is sampled and information taken from the sample is recorded by a method of conserving electrical energy in performing such sampling and recording. The method sequentially energizes and de-energizes a plurality of different electrical circuits within the downhole apparatus with which the physical condition is detected and in which the information is recorded. The method determines when the next sample is to be taken and, depending upon how much time remains until the next sample, de-energizes the apparatus to conserve energy.

Abstract: A downhole tool such as a tester valve originally constructed to operate with a compressible gas spring may be modified to operate with a compressible liquid spring. The volume of a spring chamber is increased. A differential area of a power piston is decreased. A flow restriction in a metering cartridge associated with the spring chamber is increased. Also, a relief valve is provided to allow fluid to be relieved from the tool into the well annulus upon expansion of the compressible liquid due to heating as the tool is lowered into a well if the expansion of liquid exceeds the available volume in the tool.

Abstract: A tieback packer apparatus and method for packing a well annulus above a gravel packed liner screen. The packer includes a body with a mandrel slidingly disposed therein. Originally, the mandrel is shearably pinned to the body. The body includes a lower packer support for a packer element annularly disposed around the mandrel. An upper packer support is also shearably pinned to the mandrel and includes a wedge. A plurality of slips are positioned above the wedge. Downward motion of the mandrel shears the shear pins and transfers force through a spring, thus forcing the slips toward the wedge and outwardly into gripping engagement with the well bore. The spring keeps the slips engaged while preventing excessive slip drag. Further downward movement of the mandrel sets the packer element into sealing engagement with the well bore. The packer may be retrieved by reengaging the releasing mechanism. Lifting sequentially unsets the slips, as well as unsetting the packer element.

Abstract: A liner seal for use in a tool string for sealing above a gravel pack around a liner screen. The liner seal is originally positioned in the tool string between the liner screen and a release mechanism. The release mechanism is a pressure actuated, non-rotational type having collets engaged with a portion of the liner seal. Gravel is packed around the liner screen, and the release mechanism is actuated. Setting weight on an outer sleeve of the liner seal downwardly moves the outer sleeve with respect to an inner sleeve attached to the liner screen. This relatively converging movement of the outer and inner sleeves radially outwardly displaces a seal member into sealing engagement with the well bore. A shear pin is included so that a predetermined load is required for downwardly moving the outer sleeve. A slip is provided to prevent upward movement of the outer sleeve, thus preventing disengagement of the seal member with the well bore.

Abstract: A method of gravel packing a well formation and an apparatus usable therefor. The method of gravel packing includes mixing a slurry formed by solids suspended in a gelled carrier fluid with a breaker fluid at a subterranean position above the well formation to be packed, whereby the gel is broken into a low viscosity fluid which is pumped along with the solids to the formation for packing thereof. The apparatus includes a mixing valve positioned in a tool string above a packer, crossover tool and liner screen. When the tool string is run into the well, the mixing valve defines said subterranean position. The breaker fluid is spotted in an annulus between the tool string and well bore, above the packer. The gelled slurry is pumped down the tool string to the mixing valve, and the breaker fluid is introduced through the mixing valve into the tool string for mixing with the gel.

Abstract: The method for controlling the rate at which a downhole logging tool samples and records a detected condition obtains three samples of the condition at three consecutive sample times and computes a prediction value for the n-th sample from the first three samples. The method compares the actual n-th sample with the predicted value and records the (n- 1)-th sample if the variance between the predicted and actual values is outside a predetermined threshold or difference. The sample rate is changed if the actual values of the samples remain within the predicted value's preselected range for more than a preselected number of samples. The sample rate interval is also increased if the battery life or memory capacity decrease below predetermined thresholds. The sample rate interval is decreased to its shortest interval if a pressure change above a predetermined threshold is detected.

Abstract: The ply overlap arrangement of the present invention comprises alternating the orientation or overlap direction of each ply of fabric strips with respect to a section of the peripheral reinforcing member so that each successive overlap end of strip is wrapped in the opposite direction from and falls on the opposite side of the reinforcing member from the preceding ply overlap end. Each overlap end is of sufficient length to extend back toward the center of the primary load carrying portion of the strips of the preceding ply. This arrangement, by extending the overlap ends back over the preceding ply of primary load carrying strips, ensures not only that an overlap of a strip will never be bonded to another ply overlap, but that each overlap will be bonded over a large area on one or both sides to a preceding ply of primary load carrying strips extending across the face of the closure or diaphragm.

Abstract: An apparatus and a method are disclosed wherein simultaneous electrical well logs can be made with a plurality of focused currents emitted from a plurality of electrodes located along a single equipotential surface of a housing. The focused currents are generated in response to a single voltage signal from a single power supply connected between the housing and a single current return electrode. A voltage reference is located on a cable which suspends the housing and the current return electrode in a well borehole, and a voltage detection circuit detects a voltage offset between the voltage reference and the housing.

Abstract: A gravel pack safety sub selectively positionable in rotational or a non-rotational mode. The safety sub includes an adapter having lugs thereon and a mandrel having lugs thereon adjacent the adapter. A retainer attached to the adapter receives an end of the mandrel. The mandrel and retainer define an annular cavity therebetween, and a sleeve is positioned in the cavity. The sleeve has a hole therein which is nearer a first end thereof than a second end. The hole is alignable with an exterior recess in the mandrel and a shear pin positioned therethrough. The safety sub may be placed in a first position wherein the second end of the sleeve is adjacent the adapter and the lugs on the mandrel and adapter are separated. A bearing ring is positioned between the adapter and the mandrel for maintaining the separation of the lugs and providing a bearing surface therebetween.

Abstract: Pressure operated circulation valve with releasable safety and method for operating the same. A valve mandrel slidably received within a housing is frangibly restrained in a lower position blocking a circulation port through the housing. An upper power mandrel is frangibly restrained in a lower position beneath the valve mandrel for moving the valve mandrel upwardly responsive to an increase in internal housing pressure. A safety mandrel is frangibly restrained beneath the upper power mandrel and blocks communication of internal housing pressure to the lower end of the upper power mandrel until the safety mandrel is moved upwardly responsive to an increase in annulus pressure. Thus, the circulation valve is opened by first raising the annulus pressure by a pre-determined amount and thereafter increasing internal housing pressure.

Abstract: Pressure operated circulation valve and method for using the same. A cylindrical housing has an open longitudinal passageway therethrough and a circulation port disposed through a wall thereof. A valve mandrel is slidably received in the housing and is moveable between a position in which fluid may be circulated only between the passageway and the exterior of the housing, a position in which fluid may be circulated only between the exterior of the housing and the passageway, and a position in which fluid may not be circulated in either direction. An annular piston is operatively connected to the valve mandrel and has a first side exposed to pressure exterior of the housing and a second side expose to pressure interior of the housing to permit movement of the valve mandrel to its various positions by application of pressure to the interior and exterior of the housing.

Abstract: A shaped charge carrier assembly is provided for use in a perforating gun of the type used to perforate oil or gas wells. The assembly includes at least one shaped charge including an outer case having an outer surface and a first shoulder extending radially outward from the outer surface. The assembly also includes a carrier having an opening therethrough large enough to receive the outer surface of the case, and having a resilient tab extending into the opening for frictionally engaging at least a first portion of the outer surface of the case, and for thereby holding the shaped charge in place relative to the carrier with the shoulder of the shaped charge abutting the carrier.

Abstract: A lost-motion valve actuator which provides the ability to run a tool bore closure valve in a testing string into a well in an open mode, apply pressure to the well annulus surrounding the string without cycling the valve, thereafter reduce pressure, closing the valve subsequent to the initial pressure increase, and subsequently opening the valve with pressure increases and closing it with pressure decreases, thus permitting the tool bore closure valve to subsequently respond in a normal manner (open on pressure increase, close on pressure decrease) to pressure changes in the annulus subsequent to the first pressure increase/decrease cycle.

Abstract: A full opening subsurface control valve for use in subsurface closure of a well annulus. The valve includes a body with a sleeve reciprocably disposed in the valve body. The body is releasably attached to an upper tool string portion, and the sleeve is attached to a lower tool string portion. An actuator arm, mounted on the body and stationary with respect thereto, engages a ball valve element. When the body and sleeve are in a relatively converged position, the ball valve element is in a closed position. When the body and sleeve are in a relatively extended position, the ball valve is in an open position, such that the ball valve element, body and sleeve define a substantially unobstructed flow passage through the valve. A spring is utilized for relatively biasing the body and sleeve toward the converged position. The weight of the lower tool string portion overcomes the spring force such that the valve is maintained in an open position as it is longitudinally positioned in the well bore.

Abstract: Assembly for reducing the force applied to a guide lug received in a slot. An outer telescoping member includes a guide lug extending from the radially inner surface thereof which is received in a groove formed on the radially outer surface of an inner tubular member with the lug and groove controlling relative axial movement between the inner and outer tubular members. The inner tubular member includes a load lug on the radially outer surface thereof for abutting against an annular shoulder disposed about the radially inner circumference of the outer tubular member to prevent the guide lug from exerting significant axial forces on the groove.

Abstract: A retrieving mechanism for subsurface releasing and retrieving of a downhole tool. The apparatus includes an overshot defining a central opening therethrough and an annular cavity therein and a mandrel positionable in the overshot central opening. A slotted C-ring with an internally threaded surface is annularly positioned in the cavity in the overshot. The mandrel includes an externally threaded portion. Longitudinal insertion of the mandrel in the overshot results in ratcheting expansion and contraction of the ring for threaded engagement with the mandrel. The threaded surfaces define a thread profile having a first surface, angled with respect to a central axis of the apparatus, which facilitates the longitudinal insertion of the mandrel in the ring, and a second surface, extending normally to the apparatus central axis, which prevents longitudinal disengagement. A seal is located above the ring for sealing engagement with a mandrel sealing surface.

Abstract: A weak point element for a cable head comprising a tubular ring having a circumferentially extending zone of reduced tensile strength between the ends thereof. Novel cable head assemblies which substantially isolate the weak point element from other than tensile stress are also disclosed.

Abstract: The present invention comprises a retrievable gravel packer for circulation and squeeze type gravel packing. The gravel packer includes a compression-set packer element, a J-slot assembly to releasably maintain the gravel packer in an unset mode, a ratchet assembly to releasably lock the gravel packer in a set mode, an intake passage to receive fluid from a tubing string, a return passage to receive fluid from a gravel screen below the gravel packer, a circulation passage extending from the exterior of the gravel packer to intake passage, a closeable crossover assembly to receive fluid from the return passage; a first check valve to prevent back flow back to the intake passage from the interior of the interior of a gravel screen therebelow, a second check valve adapted to selectively open the intake passage to the circulation passage, and a check valve release for removing said second check valve means from the junction of the intake and circulation passages.

Abstract: Method and apparatus by which a gun firing head is maintained free of debris. An upper tubing string runs downhole in a cased borehole to a packer device. A jet gun, having a firing head located at the upper end thereof, is connected to a lower tubing string. A vent assembly is connected in series relationship within the lower string, and underlies the packer device. A barrier is contained within the lower tubing in underlying relationship to the vent and isolates the tubing interior immediately above the gun from contact with well fluids. A gun firing device is run from the surface, downhole through the packer device, and penetrates the barrier to gain access to the gun firing head, whereupon the gun is detonated, thereby perforating the casing and penetrating the payzone.

Abstract: The present invention comprises a weight-set single-zone gravel packer which may be retrieved from a gravel screen after gravel packing or, alternatively, left in place attached to the screen as a production packer. The gravel packer includes a compression-set packer element, a first J-slot assembly to releasably maintain the gravel packer in an unset mode, a ratchet assembly to releasably lock the gravel packer in a set mode, an intake passage to receive fluid from a tubing string, a return passage to receive fluid from the interior of a gravel screen below the gravel packer, a closeable crossover assembly to receive fluid from the return passage to the wellbore annulus above the gravel packer, a first check valve to prevent flow down to the gravel screen through the return passage, a second check valve adapted to selectively connect the intake passage with the gravel packer, and a second J-slot assembly for selectively disconnecting the tubing string from the gravel packer.