Abstract: The invention concerns an apparatus for investigating the wall of a borehole tilled with non-conductive mud, said apparatus comprising: a pad having an inside face and an outside face for pressing against the wall of the borehole; a set of measurement electrodes mounted on the outside face of the pad, potentials differences being measured between said measurement electrodes in order to provide measured points representative of the resistivity of the formation; both a source electrode and a return electrode adapted to inject current into the formation, the set of measurement electrodes being situated between the source electrode and the return electrode.

Abstract: A resistivity tool for investigating a wall of a borehole drilled with a non-conductive mud includes a tool body adapted to be incorporated in a logging-while-drilling tool assembly; a resistivity sensor disposed on the tool body, wherein the resistivity sensor comprises a sensor pad supporting a current injector electrode, a current return electrode, and an array of measurement electrodes, and a circuitry for controlling current injection from the current injector electrode and for measuring voltage difference between electrodes in the array of measurement electrodes, wherein the current injector electrode and the current return electrode are disposed near opposite ends of the sensor pad and the array of measurement electrodes is disposed between the current injector electrode and the current return electrode, wherein the sensor pad is constructed of an insulating material and includes a conductive shielding member, or wherein the sensor pad is constructed of a conducting material and includes insulating sec

Abstract: An apparatus for determining fluid-pressure diffusivity in a borehole (12) in a formation (10) includes an electrode (16) and a strain measuring device (18),(20) (or a particle velocity measuring device (18),(20) or a particle acceleration measuring device (18),(20)) disposed a fixed distance from the electrode (16). The electrode (16) injects an electrical current into a point on a wall of the borehole (12). The strain measuring device (18),(20) measures strain (or the particle velocity measuring device (18),(20) measuresd particle velocity or the particle acceleration measuring device (18),(20) measures particle acceleration) at the fixed distance from the point of injection of the electrical current over time. The fluid-pressure diffusivity is determined based on the measured strain (or measured particle velocity or measured particle acceleration) over time.

Abstract: A method for electrically investigating a wall of a borehole in a geologic formation including injecting a current into the formation at a first position along the wall and returning the current at a second position along the wall, the formation current having a frequency below about 100 kHz, measuring a voltage in the formation between a third position and a fourth position along the wall, the third and fourth positions being located between the first and second positions, and determining an amplitude of a component of the voltage in phase with the current.

Abstract: An azimuthal resistivity logging tool includes one or more pads for making azimuthal resistivity measurements of earth formation. Current from the pads, guard electrodes and a measure electrode are measured while monitoring the voltage difference between pairs of monitor electrodes. The pads and an adjacent portion of the tool body form a guard electrode. In addition, microelectrodes are provided on the pads for obtaining high resolution resistivity measurements.

Abstract: A multi-mode oil base mud imager for use in non-conductive drilling fluid includes at least one current source—a current return pair, and one or more monitor electrodes not located between the current source and the current return of the current source-current return pair. Where more than one current source-current return pair is included, the tool is capable of multiple depths of investigation into surrounding formation. This data can be used as a gauge to establish the reliability of the data and to determine the resistance of the invaded zone around the borehole, as well as standoff distance of the tool from the borehole wall.

Abstract: A multi-mode resistivity tool measures at multiple depths into the near-borehole formation. By use of a four mode tool, measuring to four depths at the formation, a more accurate invasion zone resistivity measurement may be made than previously known. The tool itself is shown as including six concentric electrodes, although not every electrode is necessary for every mode.

Abstract: A unique means in interpreting anisotropic reservoirs in thinly laminated earth formations regardless of the hole deviation is provided. A high-resolution micro-resistivity formation measurement is used to estimate in real time at the well site the formation anisotropic electrical parameters oriented around the borehole drilled with a conductive fluid. Estimations of the formation anisotropy or hydrocarbon profile are compared and combined with indicators associated with the formation to provide improved evaluations of hydrocarbon content over conventional methods.

Abstract: The present invention relates to apparatus for a tool for investigating the wall of a borehole in a geological formation, the apparatus comprising: a non-conductive pad having an inside face and an outside face for pressing against the wall; a set of measurement electrodes mounted on the outside face of the pad and means for measuring the potential difference between two measurement electrodes; and both a source electrode adapted to inject current into the geological formation and a return electrode, the set of measurement electrodes being situated between the source electrode and the return electrode for the current; the apparatus being characterized in that the pad comprises an electrically conductive portion covering the entire measurement electrode zone and electrically insulated from the measurement electrodes.

Abstract: Using micro-resistivity techniques, an image of the wall of a borehole can be obtained. A downhole tool stack is provided with plural imaging tools, wherein each imaging tool has a set of pads that deploy radially outward to contact the borehole wall to obtain the image thereof. As the pads deploy outwardly, gaps are formed between the pads. The pads of one tool are circumferentially offset relative to the pads of the other tool so that more complete circumferential coverage of the borehole wall is obtained during the imaging process. Furthermore, an adaptive polling technique is utilized to telemeter the large amounts of data generated by the two imaging tools to the surface. Data is obtained from the imaging tools by polling at a particular rate, which rate is modified depending upon the amount of data generated by the imaging tools.

Abstract: A centralizer (1) for position a casing (3) in a conduit (4) passing through underground formations includes measurement means (7) such as an electrode for deriving at least one representative parameter of the formations.

Abstract: A logging tool is disclosed for measuring the resistive anisotropy of formations around a borehole. The logging tool includes a set of electrodes that contact a wall of the borehole. The set of electrodes includes a first pair of current electrodes spaced apart vertically, and a second pair of current electrodes spaced apart horizontally. Between the first and second pair of current electrodes are two or more measurement electrodes that measure a vertical axis voltage difference and a horizontal axis voltage difference caused by currents flowing between the pairs of current electrodes. A resistive anisotropy can be calculated from the measured voltage differences. A third pair of current electrodes oriented perpendicularly with respect to the first and second pair of current electrodes may be provided with corresponding measurement electrodes if it is desired to measure the biaxial resistive anisotropy of the formation.

Abstract: A method and apparatus for a downhole antenna comprising a housing having an outer surface and a longitudinally bored inner cavity, the outer surface having a first slot and a corresponding second slot extending from the outer surface to the longitudinally bored inner cavity; a first removable downhole antenna segment disposed in the first slot in a first transverse cross section of the housing, the first removable downhole antenna segment comprising at least one coil to inductively couple a signal from the longitudinally bored inner cavity to the earth formation. A second removable downhole antenna segment, interchangeable with the first removable downhole antenna segment, disposed in the corresponding second slot, the second slot in a second transverse cross section of the housing, the second removable downhole antenna segment comprising at least one coil to inductively couple a signal from the earth formation to the longitudinally bored inner cavity.

Abstract: A resistivity logging apparatus has an array of electrodes projecting from imaging pads. The electrodes penetrate nonconductive mud lining the borehole wall. Some of the electrodes are moveable in and out of the pad while others of the electrodes can be fixed. The electrodes, which are arranged in an array along a circumferential portion of the borehole wall, are able to make contact with the borehole wall. Sequencing electronics causes one electrode to be a source, another to be a measuring electrode, with the measurements of source electrode and measuring electrode moving along the array in order to log a circumferential portion of the borehole wall.

Abstract: In an apparatus and method for actuating arms used on a borehole data-logging tool to deploy measuring instruments against a borehole wall, a mandrel is provided. At least one arm carried by the mandrel is mounted to the mandrel to move between an expanded position, in which a part of the arm projects from the mandrel, and a retracted position. A resilient biassing compression spring provides a resilient biassing force on each arm for biassing the arm towards its expanded position. A hydraulic piston and cylinder assembly associated with each arm restrains the arm against movement towards its expanded position. A drive piston and cylinder assembly acts upon the resilient biassing compression springs for adjusting the resilient biassing force acting upon each arm.

Abstract: A unique means in interpreting anisotropic reservoirs in thinly laminated earth formations regardless of the hole deviation is provided. A high-resolution micro-resistivity formation measurement is used to estimate in real time at the well site the formation anisotropic electrical parameters oriented around the borehole drilled with a conductive fluid. Estimations of the formation anisotropy or hydrocarbon profile are compared and combined with indicators associated with the formation to provide improved evaluations of hydrocarbon content over conventional methods.

Abstract: A logging tool is disclosed for measuring the resistive anisotropy of formations around a borehole. The logging tool includes a set of electrodes that contact a wall of the borehole. The set of electrodes includes a first pair of current electrodes spaced apart vertically, and a second pair of current electrodes spaced apart horizontally. Between the first and second pair of current electrodes are two or more measurement electrodes that measure a vertical axis voltage difference and a horizontal axis voltage difference caused by currents flowing between the pairs of current electrodes. A resistive anisotropy can be calculated from the measured voltage differences. A third pair of current electrodes oriented perpendicularly with respect to the first and second pair of current electrodes may be provided with corresponding measurement electrodes if it is desired to measure the biaxial resistive anisotropy of the formation.

Abstract: The present invention relates to a method of investigating the wall (2) of a borehole in a geological formation by means of two injectors (4, 5) with a potential V being applied between them and in measuring the potential difference &dgr;V between two electrically isolated measurement electrodes (6) situated between the two injectors (4, 5) and spaced apart from the formation by an insulating layer (1), in which the resistivity of the formation is obtained from the measured values of &dgr;V, V and I, with corrections being made for the effects due to the nature and the thickness of the insulating layer (1). In a first variant these corrections are based on a correction factor obtained from curves of K=Rt.I/&dgr;V as a function of the impedance V/I of the injector. In a second variant these corrections are obtained by estimating the current IF actually injected into the formation while taking account of leakage current IL, and calculating the resistivity of the formation from the equation (I).

Abstract: The present invention relates to apparatus for a tool for investigating the wall of a borehole in a geological formation, the apparatus comprising: a non-conductive pad having an inside face and an outside face for pressing against the wall; a set of measurement electrodes mounted on the outside face of the pad and means for measuring the potential difference between two measurement electrodes; and both a source electrode adapted to inject current into the geological formation and a return electrode, the set of measurement electrodes being situated between the source electrode and the return electrode for the current; the apparatus being characterized in that the pad comprises an electrically conductive portion covering the entire measurement electrode zone and electrically insulated from the measurement electrodes.

Abstract: Using micro-resistivity techniques, an image of the wall of a borehole can be obtained. A downhole tool stack is provided with plural imaging tools, wherein each imaging tool has a set of pads that deploy radially outward to contact the borehole wall to obtain the image thereof. As the pads deploy outwardly, gaps are formed between the pads. The pads of one tool are circumferentially offset relative to the pads of the other tool so that more complete circumferential coverage of the borehole wall is obtained during the imaging process. Furthermore, an adaptive polling technique is utilized to telemeter the large amounts of data generated by the two imaging tools to the surface. Data is obtained from the imaging tools by polling at a particular rate, which rate is modified depending upon the amount of data generated by the imaging tools.

Abstract: An apparatus for obtaining resistivity images of a borehole includes an array of measure electrodes separated from a pad or the body of the instrument by a guard electrode. The guard electrode is maintained at a slightly lower potential than the pad and the measure electrode is at an intermediate potential thereto. With this arrangement, the current from the guard electrode defocuses the measure current from the measure electrode as it enters the formation, and at greater distances, the current from the measure electrode is refocused by the effect of the current from the pad. This defocusing and refocusing defines a region of investigation away from the borehole wall that is relatively insensitive to borehole rugosity. Circumferential and vertical overlap may be obtained either by the arrangement of the measure electrodes, or by relying on the broadening of the measure beam as it enters the formation.

Abstract: The borehole imaging apparatus of the present invention includes a tool having an array of voltage electrode buttons mounted on a non-conductive pad. A current source and a current return are preferably located on the non-conductive pads at opposite ends thereof. The locations of the current source and return are designed to force a current to flow in the formation parallel to the pad face and non-parallel to the formation boundary layers. According to a method of the invention, the voltage difference between a pair of buttons in the array is proportional to the resistivity of the formation bed adjacent to the buttons. The ratio of voltage differences between two nearby pairs of electrode buttons provides a quantitative measurement of the ratio of shallow resistivity. The resolution of the image produced by the new tool is determined only by the spacing of the buttons. The tool according to the invention produces much better images than the prior art tools when used in OBM wells.

Abstract: An improved formation testing method increases the accuracy of in-situ formation pressure measurements by characterizing the mudcake properties. Specifically, after a formation tester is lowered to a desired depth within a wellbore, a pad is extended to gently abut and seal against the mudcake without disturbing the mudcake. When pressed against the mudcake, the pad experiences momentarily higher pressures, which are measured by a probe housed by the pad. These pressures may be enhanced by briefly rejecting fluids through the probe, so as to avoid disturbing the mudcake. The probe continues to measure pressure, which eventually decreases relative to hydrostatic pressure in the wellbore, due to the flow of high-pressure wellbore fluids through the mudcake.

Abstract: A well logging apparatus adapted to be moved inside a borehole includes an elongate body, a measuring pad adapted to contact the wall of the borehole, a support device for the pad mounted pivotally on one side of the body, and a counter arm which causes the pad to be applied against the wall of the borehole. The support device includes an arm which carries the weight of the pad and is connected to the pad substantially in the central part thereof.

Abstract: A sidewall contact parameter tool, adapted to be disposed in a mud-filled wellbore, includes a pad assembly, in accordance with the present invention, which is adapted to cut through mudcake and measure a parameter of a formation disposed under the mudcake. The wellbore wall includes a mudcake and an earth formation disposed under the mudcake. The pad assembly includes at least one formation parameter sensor, and the formation parameter sensor includes a base portion and a knife edge portion integrally connected to the base portion. The base portion of each formation parameter sensor is adapted to contact a surface of the mudcake but the knife edge portion is adapted to cut into the mudcake and contact or penetrate a surface of the earth formation disposed under the mudcake. The knife edge portion of each sensor includes an internal space or pinhole aperture, and a parameter sensing apparatus disposed within the internal space or aperture.

Abstract: The apparatus includes a pad (20) pressed against the wall of a borehole (12), the pad comprising a plurality of detecting devices (42, 43, 44, 45) disposed in alignment along the longitudinal direction of the borehole. Each detecting device includes a housing (112, 113) having complementary ends fitted with electrical connectors. The end of one housing (112) is extended by first skirts (117, 118) suitable for interfitting between second skirts (121) of the complementary end of the housing (113) of an adjacent detecting device. An annular element (111) and screws (120, 122) fixed to complementary ends together thus constituting a rigid pad (20) which can be disassembled.

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 seismic array system for receiving seismic signals at spaced-apart points in a wellbore is deployable on coiled tubing from the surface through an isolator apparatus mounted on the wellhead. The array includes spaced-apart geophone sondes which have hydraulic actuators for extension of sonde support pads into engagement with the wellbore wall. Each sonde has a hydraulic control unit for controlling operation of the hydraulic actuator to extend or retract the pads and for preliminary processing of signals received through the geophones of each sonde. Hydraulic fluid and electrical control signals are communicated through the coiled tubing from the surface. A signal processing unit is deployed at the upper end of the array string for final or intermediate processing of the geophoen signals from each sonde.

Abstract: A microelectric method and apparatus for recording and differentiating between open and closed fractures along the walls of boreholes is disclosed. A main current and a controlled opposing or bucking current are fed into a hard rock formation in a measurement area of a borehole wall insulated from the drilling mud in the borehole. Within this measurement area absolute potential and potential differences are measured and dimensionless ratios based on the measurements of current and potential are ascertained. The ratios indicate the presence of fractures and allow differentiation between open and closed fractures allowing determination of an open fracture network. The apparatus is made up of at least one measuring pad (6) made of insulating material forced onto the wall of borehole.

Abstract: Method and apparatus for obtaining fine detail of spontaneous potential (SP) along a bore-hole wall in the earth, in connection with exploration for petrochemical deposits. A laterally-extending array of SP-sensing electrodes is mounted on an insulating pad, each slightly below the pad surface, and the pad is moved along and against the bore-hole wall while the SP's at the electronics are sampled and sent to up-hole electrodes for processing. The processed electrode samples are used to form a two-dimensional visually-observable image of the segment of the bore-hole wall swept over by the electrodes on the pad.

Abstract: The method of measuring local rock inhomogeneities on the wall of a borehole is disclosed. The method of measurement includes the step of generating microelectric fields in a conductive way on an area of the wall of the borehole insulated from the drilling mud by an insulating pad which carries electrodes and excludes direct electrical contact between the electrodes and the conductive borehole liquid. The local current intentities are measured at, at least two, different places perpendicularly to the wall of the borehole and the measured current intensities are compared to each other. Alternatively, a local voltage difference created by current flowing first parallel to the wall of the borehole and then an absolute voltage created by the same current in another section of flow where the current is perpendicular to the wall of the borehole may be measured and the measured voltages compared to each other.

Abstract: In order to increase the angular field of observation of a logging sonde usable, in particular for dip metering, the sonde is equipped with measuring pads each comprising two independent flaps. The flaps of the same pad are hinged to a central element which is held permanently parallel to the axis of the sonde body, and they are applied against the wall of a borehole by blade springs. Each of the flaps carries an array of electrodes. The flaps of each of the measuring pads are circumferentially offset relative to each other so that the angular field of observation is increased without increasing the diameter of the sonde, once the pads have been retracted.

Abstract: Method and apparatus for transmitting data uphole in a well to the top of the well. A string of electrically conductive tubing and a tool connected to the tubing are lowered down the well along the inside of tubular shaped electrically conductive casing for the well. The inside of the casing is electrically contacted with an electrical contact carried by the tool. A switch in the tool is operated for alternately electrically connecting and disconnecting the contact and thereby the casing and with respect to the conductive tubing for changing the electrical conductance between the tubing and the casing representative of data. The changing conductance is interrogated with an alternating current, formed at the top of the well, to recover the data.

Abstract: Apparatus for positioning a detector at a plurality of depth locations within a large diameter borehole includes an elongated body member having a pair of diametrically opposed hydraulic pad displacement members mounted thereon. A pad mounting member is pivotally attached to each pad displacement member and a pair of borehole wall contacting members are pivotally attached to each pad mounting member. A signal detector is mounted behind one or more of the pad members. At each test depth a hydraulic power system deploys the pad displacement members from the body member to an extended position and extends the wall engaging pad members into contact with the borehole wall.

Abstract: An acoustic method and apparatus for investigating an earth formation penetrated by a borehole are described. Acoustic transducers are mounted on a tool to accurately determine the distance between a segment of the tool and the wall of the borehole. The acoustic transducers are positioned in such manner that the stand-off distance between individual resistivity measuring electrodes in an array, which is also mounted on the tool segment, and the borehole wall can be measured. The stand-off measurement is recorded and may be used to correct the electrode resistivity measurements. In one embodiment a calibration of acoustic transducers as a function of depth is obtained by employing acoustic calibrating transducers to compensate for borehole environment effects on the performance of the acoustic transducers as well as determine the acoustic velocity of the borehole fluid, such as mud. Several embodiments are described.

Abstract: Statistical variations in nuclear borehole logs are reduced using digital moving average data processing while maintaining responsiveness to formation changes, by transitioning through a combination of long and short filtered data as a function of the statistical variation of the differences of the long and short derived averages.

Abstract: Dip measurements and investigation of geological formations traversed by a deviated borehole is carried out by means of an apparatus comprising a measuring sonde and a cartridge connected to a cable. The sonde carries four measuring pads regularly distributed by means of articulated arms which keep the pads parallel to the axis of the sonde. The opposite arms are forced to stay symmetrical in relation to the sonde.The sonde is connected to the cartridge so that its axis can depart angularly from the axis of the cartridge, enabling the latter to rest on the borehole wall. The pads have a length smaller than twice the transverse dimension D of the sonde.

Abstract: An apparatus is described for urging the measuring pad of a well logging sonde into engagement with the wall of a borehole. A relatively long primary arm on which the pad is mounted includes an actuator, and is pivotally connected to the body of the well logging sonde by a member extending therefrom. A backup arm is pivotally mounted on the extension member and biased outward from the logging sonde by suitable resilient means. The backup arm also is positively connected to a displacement member associated with the actuator. The primary and backup arms are cooperatively withdrawn into the body of the logging sonde by operation of the actuator. Moreover, the logging sonde is made eccentric in the borehole by suitable resilient means connected between the extension member and the sonde body.

Abstract: The present invention relates to the acquisition of seismic signals at different levels in a borehole, in response to the generation of seismic waves by a source placed on the surface or in the vicinity of the surface. The acquisition is carried out by means of a sonde suspended in the borehole from a cable and equipped with an anchoring pad. At each acquisition level, the pad is anchored in the borehole wall to couple the sonde to the formation, and then the pad is released from the wall once the acquisition is over. The signals acquired are then sent to the surface by means of the cable. The force with which the pad is anchored in the wall is controlled by means of a feedback arrangement which includes a sensor arranged in the pad itself. During the sonde movements from one level to another, the pad is kept in contact with the wall.

Abstract: The present invention relates to the acquisition of seismic signals at different levels in a borehole, in response to the generation of seismic waves by a source placed on the surface or in the vicinity of the surface. The acquisition is carried out by means of a sonde suspended in the borehole from a cable and equipped with an anchoring pad. At each acquisition level, the pad is anchored in the borehole wall to couple the sonde to the formation, and then the pad is released from the wall once the acquisition is over. The signals acquired are then sent to the surface by means of the cable. The force with which the pad is anchored in the wall is controlled by means of a feedback arrangement which includes a sensor arranged in the pad itself. During the sonde movements from one level to another, the pad is kept in contact with the wall.

Abstract: A plurality of formation resistivity logging data sets are generated along a borehole. From the data formation dip values are preliminarily determined at different elevations along the borehole. The dip values are combined for each borehole elevation of interest in a functional relationship utilizing a variable scatter parameter related to dip direction and magnitude variations whereby the resulting dip value at each elevation is taken as the corrected value. The variable scatter parameter may be selectively varied to produce variable representations as desired of formation dip, including visual representations. These variable representations may range from those excluding dip data points inconsistent with prevailing geological interpretation patterns and thereby exhibiting progressively less scatter to those representations including more available and possible dip values with scatter to be interpreted.

Abstract: Methods and apparatuses for electrically investigating a borehole are described. Tool mounted pads are provided, each with a plurality of small measure electrodes from which individually measurable survey currents are injected toward the wall of the borehole. The measure electrodes are arranged in an array in which the measure electrodes are so placed at intervals along at least a circumferential direction (about the borehole axis) as to inject survey currents into the borehole wall segments which overlap with each other to a predetermined extent as the tool is moved along the borehole. The measure electrodes are made small to enable a detailed electrical investigation over a circumferentially contiguous segment of the borehole so as to obtain indications of the stratigraphy of the formation near the borehole wall as well as fractures and their orientations.

Abstract: Method and apparatus are disclosed for investigating lateral characteristics of an earth formation penetrated by a borehole. Substantially identical measurement transducers are mounted in a fixed separation, side-by-side relationship on a pad adapted for sidewall application. As a pad traverses the borehole, measurement signals are produced corresponding to the same formation investigation conducted along two side-by-side paths on the borehole wall. The signals are recorded and provide an indication of lateral changes between the side-by-side paths. By comparing the signals with varying depth displacements, the best likeness and corresponding displacement are determined and provided as an indication of lateral inclination of the formation. The best likeness indicates a lateral formation homogeneity characteristic and the displacement the inclination of the lateral characteristic between the side-by-side paths.

Abstract: An electrical well logging system is disclosed wherein the well logging tool is enclosed at least in part by an expandable sleeve having a band of electrodes located in the outer surface thereof. The band of electrodes is located in a plane which is perpendicular to the vertical axis of the well logging tool. When the well logging tool is in a desired position in the borehole, the expandable sleeve is expanded to place the electrodes located therein in contact with the adjacent sidewall surface of the borehole. Current is injected into the formation surrounding the borehole and the voltage induced by the current is measured. A phase comparison of the current injected into the formation and the voltage sensed in response to the injected current can be utilized to determine if clay is present in the formation.

Abstract: A borehole investigating apparatus includes, an elongated support member, a first pair of wall-engaging pad members individually disposed on opposite sides of the support member along a given line and a second pair of wall-engaging pad members individually disposed on opposite sides of the support member along a given line at right angles to the given line for the first pair. The apparatus further includes first and second pad extending means for respectively moving the pad members of the first and second pairs away from the support member and against the borehole wall. The apparatus further includes primary driving means and a force dividing mechanism coupling this primary driving means to the first and second pad extending means for enabling unequal lateral extension of the pad members of the different pairs..Iaddend.