Gimballess inertial navigation system IGMC - 73 «AZIMUTH»         Quality inclinometry (attestation) of wells without limitations as to the inclination angle and directional readings when performing geological and research and drilling works as well as the evaluation of the state of operating wells is possible only with the application of the gimballess inertial navigation system with the full set of sensory elements.        Today gimballess gyroscopic inclinometric systems are designed in the USA, Germany, France, Russia. In Russia the mentioned systems are designed by V.I.Kuznetsov R&D Institute of Applied Mechanics, Perm Research and Development Device Making Company, R&D Institute of Drilling Equipment et al.       The latest research in well inclinometry development has shown a tendency of magnetometric tools being replaced by tools the work of which is based on the application of methods of gyroscopic positioning.      1. Navigation system IGMC - 73 «AZIMUTH» design and performance       The navigation system IGMC - 73 «AZIMUTH» consists of three precision angular rate gyroscopes, three linear acceleration meters, a special computer, precision centralizers.      The task of positioning precision angular rate gyroscope sensitive axes along orthographic tetrahedrons with significant structural limitations, the latter caused by the size of the diameter, has been resolved [1].       A modular construction was used in the design of the navigation system structure.  The well tool of the navigation system consists of an outer casing 1, elements of casing positioning in the well 2,3, a sensors unit and an electronics unit (drawing 1).  The sensors unit has three precision angular rate gyroscopes, 4 and three acceleration meters, 5 constructed in accordance with the compensative principle of measurement, using the elastic hinge of the sensory element.  The measurement axes of precision angular rate gyroscopes and acceleration meters form mutually otrhogonal tetrahedrons, the axis of one of the precision angular rate gyroscopes is collinear to the longitudinal axis of the inclinometer and the measurement axes of acceleration meters are collinear to the corresponding measurement axes of precision angular rate gyroscopes.  The electronics unit consists of a control, data retrieval and a primary data processing panel, 6 and a power unit, 7.  The mechanical joining of separate units is realized with the help of dismountable parts and electrical joining with the help of connectors. The power unit supplies the energy required for the operation of the descending part of the navigation system including for the work of gyromotors. Analogue outputs of six sensors are connected to the control, data retrieval and a primary data processing panel. Using the principle of frequency modulation the signals measured through the logging cable are transferred to the ground part of the inclinometer.        The ground part of the navigation system consists of a PC, a modem and a power unit.  The navigation system is powered from an ac power source with 50 hertz frequency and 220 V voltage.   2. Work modes of IGMC-73 «AZIMUTH»      Before descending into the well an automatic computer control-test of system operation and an accuracy control-test of system performance with the purpose of achieving maximum accuracy by means of clearing the tool’s static errors are made.   2.1. Point mode       Measuring directional readings in the earth referenced coordinate system with the help of IGMC-73 «AZIMUTH» puts additional requirements to linear acceleration meter and precision angular rate gyroscope sensitive axes position stability when taking measurements.  Failure to fulfill these requirements brings to poor accuracy of system parameters or increases the time of measuring directional readings.        There are methods of improving the accuracy of measurements by means of rotating the sensory package (SP) inside the well tool.  This method requires a sophisticated system structure, strict colinearity of SP rotational axes and well axes (see description of SlimPulse system of Schlumberge).       During bench tests and inclinometry trials performed together with the experts from Closed Joint-Stock Company “Pomorneftegazgeofizika” a number of wells a D/A filter for rejecting the response of the well tool on precision angular rate gyroscopes within the frequency of 0,01 hertz and above, with the level of response rejection not worse than 20 dB was designed. In order to reject the response of the well tool with the frequency of 0,01 hertz and lower and reduce various drifts of precision angular rate gyroscopes (thermal drift, decentration drift etc.), a method of reversing the gyroscope angular momentum was applied [2].  The implementation of the measures mentioned above allowed us to measure directional readings with poor well tool stability, the latter caused by the system being located in the well (attachment 1, 2).       With reference to the works on the inclinometry of a number of wells performed together with Closed JSC “Pomorneftegazgeofizika” a method of improving the accuracy of directional readings measured in point mode, using the recommendations [3] and a directional symmetric array of the well tool on directional readings in the well section by controlling the whipstock angle variation was applied for the very first time.        The application of the mentioned method allowed us to perform the inclinometry of a  slightly inclined (inclination angel from 0 to 5 degrees) well in the region of Poltava in Ukraine. In order to confirm the accuracy of measurements a method of two well tools (Attachment №3) was applied.  The interpretation of point measurements was realized by means of applying the method of heuristic self-organization. As a result, we received a regressive model which is a better equivalent to the actual well path (the so-called “physical analogue”).     3. Continuous mode.       Measuring special coordinates using the point mode requires a great number of measured points and as a result a lot of time to measure the inclinometric parameters accurately.       Simple in drilling wells or in operation as a result of well logging brings to financial loss.  That is why today navigation systems (see, for example, the description of TARGET system), designed especially for continuous logging at high speed, allowing you to reduce the time of inclinometric works have appeared.        We should note that, as a rule, there is no description of the initial directional alignment of these tools both on the surface of the Earth and in the well in the description of the inclinometric navigation systems.  The only well-known system in the CIS is the gyroscopic inclinometer IGC-73-100/80, designed by LLC “Aras-Plus”, allowing you to perform directional alignment only on the well top [4]. This is a major limitation as it doesn’t allow you to correct the indicators during continuous work mode in the well by applying a point mode.      Navigational system IGMC - 73 «AZIMUTH» allows you to perform continuous inclinometry without well tool speed limitations, sustaining high accuracy (see attachment 4).  This is achieved by implementing a number of innovations [5] of the latest data processing methods, heuristic methods of decision making.        According to the results of full-scale tests directional readings were measured with a 0,5 degree deviation in 600 seconds of continuous measurement. The alignment of the navigation system was made in point mode.       Test samples of gimballess inertial navigation system IGMC-44-M «Azimuth» have been designed and manufactured.         A test sample of the gyroscopic inertial sensors unit IGMC-56-DV «Azimuth» that can be installed in any telemetric bottom-hole system, resolve positioning tasks during magnetic disturbances  without telemetry angle or time limitations is undergoing bench tests.   Literature  1.      Patent: “Angular rate sensor”. (11) 2109 (UA), (51) 7 G01P9/00. Shervashydze V.V., Leonenko K.N., Murzahanov A.V.   2.      Patent: “Method and device for measuring angular rate”. (11) 61044 (UA), (51) 7 G01P9/00. Shervashydze V.V., Leonenko K.N., Murzahanov A.V.   3.      Guidance. A technical instruction on performing geophysical inspections and works using devices fixed on cables in oil and gas wells RD 153-39.0-072-01. М. 2001.  4.      Gyroscopic inclinometer IGC-73-100/80 // Karotazhnik. 2003. №107. P. 142-147.  5.      Patent: “Method of measuring topogeodetic indicators and gyroscopic inclinometer for its implementation”. (11) 60288 А (UA), (51) 7 G01P9/00. Shervashydze V.V., Leonenko K.N., Murzahanov A.V.        Attachment №1-1  The results of bench tests at Closed JSC “Pomorneftegazgeofizika”       Attachment №1-2  The results of bench tests at Closed JSC “Pomorneftegazgeofizika”     Attachment 2-1   The results of tests in the well in the region of Tedynskiy deposit   Tool IGMC 73-100/100 №14/1         Attachment 2-2   The results of tests in the well in the region of Tedynskiy deposit   Tool IGMC 73-100/100 №14/2         Attachment 2-3   The results of tests in the well in the region of Tedynskiy deposit  Tool IGMC 73-100/100 №14/2         Attachment 2-3  The results of tests in the well in the region of Tedynskiy deposit   Graph showing directional readings depth dependence for two tools ---  IGMC 73-100/100 №14/1 ---  IGMC 73-100/100 №14/2 --- Averaging over two tools   . Attachment №3   The results of inclinometry of a slightly inclined well in Poltava region     IGMC 73-100/100 №14/4 IGMC 73-100/100 №14/6 Depth   Inclination angle,deg. Directional readings,deg.   Inclination angle,deg. Directional readings, deg. 1800 4,18 47,1 4,18 47,7 1850 3,0 98,9 3,15 101,2 1900 2,73 134,1 2,86 136,8 1950 3,19 156,7 3,38 158,3 2000 4,08 167,2 4,15 167,4 2050 4,95 169,8 5,05 168,9 2100 5,62 167,8 5,42 166,4 2150 5,26 164,6 5,06 163,7 2200 5,36 162,8 5,35 164,6     Inclination angle,deg. Directional readings,deg. Average error 0,058 0,69 Root-mean-square error 0,0047 0,62   The maximum deviation of two tools is: directional readings 2,7°(depth 1900 m) and inclination angle 0,2° (depth 2100 m).