A rolling cutter drill bit comprises a bit body (12) adapted for rotation about a longitudinal axis (8), a plurality of extending legs (14), and a cantilevered bearing spindle (16) formed on each leg (14), a plurality of rolling cone cutters (17, 18, 19) being rotatably mounted upon the bearing spindles (16) with the cone apices (15) adjacent to the longitudinal axis (8) of the bit, a plurality of cutting inserts (20) being secured in the rolling cone cutters (17, 18, 19), and being arranged in a plurality of rows (50, 52, 54), at least two of the rolling cone cutters (17, 18, 19) being intermeshing cutters, arranged such that they have intermeshing rows of cutting inserts (20), wherein at least one of the intermeshing cutters (17, 18, 19) has a groove (72, 74, 76, 78) arranged to register with one of the rows (54) of cutting inserts (20) of another of the intermeshing cutters (17, 18, 19), and wherein the groove (72, 74, 76, 78) contains a plurality of generally flat top bearing inserts (88).

The present invention is directed to an improved method and apparatus for monitoring and recording of operating conditions of a downhole drill bit during drilling operations. The invention may be alternatively characterized as either (1) an improved downhole drill bit, or (2) a method of monitoring at least one operating condition of a downhole drill bit during drilling operations in a wellbore, or (3) a method of manufacturing an improved downhole drill bit. When characterized as an improved downhole drill bit, the present invention includes (1) an assembly including at least one bit body, (2) a coupling member formed at an upper portion of the assembly, (3) at least one operating conditioning sensor carried by the improved downhole drill bit for monitoring at least one operating condition during drilling operations, and (4) at least one memory means, located in and carried by the drill bit body, for recording in memory data pertaining to the at least one operating condition. Optionally, the improved downhole drill bit of the present invention may cooperate with a communication system for communicating information away from the improved downhole drill bit during drilling operations, preferably ultimately to a surface location. The improved downhole drill bit of the present invention may further include a processor member, which is located in and carried by the drill bit body, for performing at least one predefined analysis of the data pertaining to the at least one operating condition, which has been recorded by the at least one memory means.

The present invention is directed to an improved method and apparatus for monitoring and recording of operating conditions of a downhole drill bit during drilling operations. The invention may be alternatively characterized as either (1) an improved downhole drill bit, or (2) a method of monitoring at least one operating condition of a downhole drill bit during drilling operations in a wellbore, or (3) a method of manufacturing an improved downhole drill bit. When characterized as an improved downhole drill bit, the present invention includes (1) an assembly including at least one bit body, (2) a coupling member formed at an upper portion of the assembly, (3) at least one operating conditioning sensor carried by the improved downhole drill bit for monitoring at least one operating condition during drilling operations, and (4) at least one memory means, located in and carried by the drill bit body, for recording in memory data pertaining to the at least one operating condition. Optionally, the improved downhole drill bit of the present invention may cooperate with a communication system for communicating information away from the improved downhole drill bit during drilling operations, preferably ultimately to a surface location. The improved downhole drill bit of the present invention may further include a processor member, which is located in and carried by the drill bit body, for performing at least one predefined analysis of the data pertaining to the at least one operating condition, which has been recorded by the at least one memory means.

A method for evaluating formations and bit conditions is presented. The present invention processes signals indicative of downhole weight on bit (WOB), downhole torque (TOR), rate of penetration (ROP) and bit rotations (RPM), while taking into account bit geometry to provide a plurality of well logs and to optimize the drilling process. Drilling operations are monitored and adjusted in response to these processed signals and logs. The processed signals may include the following signals: drilling response, differential pressure, pore pressure, porosity, porosity compensated for formation effects, drilling alert, bit wear factor, abnormal torque, and bearing wear. The logs may include a drilling response log, a differential pressure log, a porosity log, a porosity log compensated for formation effects, a drilling alert log, a wear factor log, a torque analysis log and a bearing wear log.

The present invention is an improved wellbore tool for coupling to a drill string at a threaded junction and adapted for use in a wellbore during drilling. A sensor is disposed in the wellbore tool for sensing a condition and producing a data signal corresponding to the condition. A self-contained power supply is disposed in the wellbore tool and coupled to the sensor for providing power to the sensor as required. The Hall Effect coupling transmitter means is carried by the sensor and for transmitting data from the Hall Effect coupling transmitter means to a Hall Effect coupling receiver carried by the drill string and disposed across the threaded junction from the wellbore tool, wherein data is transmitted across the threaded junction without requiring an electrical connection at the threaded junction.

A method is provided for determining the state of wear of a multicone drill bit. Vibrations generated by the working drill bit are detected and converted into a time oscillatory signal from which a frequency spectrum is derived. The periodicity of the frequency spectrum is extracted. The rate of rotation of at least on cone is determined from said periodicity and the state of wear of the drill bit is derived from said rate of cone rotation. The oscillatory signal represents the variation in amplitude of the vertical or torsional force applied to the drill bit.

To extract periodicity, a set of harmonics in the frequency spectrum is given prominence by computing the cepstrum of the frequency spectrum or by obtaining an harmonic-enhanced spectrum. The fundamental frequency in the set of harmonics is determined and the rate of cone rotation is derived from said fundamental frequency.

Information on tooth wear is obtained from the frequency distribution spectrum of a vibrational quantity influenced by the impact of cutter teeth on the bottom of a bore. In the illustrated example spectra are obtained from the product of torque and torsional acceleration and tooth wear is indicated by the shift upwardly in frequency of a pronounced peak occurring at T1 for a one eighth worn bit and at T5 for a five eighths worn bit. Other quantities which may be used, singly or together to enhance spectral information, are weight on bit, vertical acceleration, transverse acceleration, standpipe pressure. Abrupt changes in frequency distribution curves indicate abrupt occurrences such as broken teeth or stuck cones. A stuck cone is also indicated by unidirectional peaks in a plot of torsional acceleration against time.

A roller cone bit may (10) be used as a rotating drag bit by treating the roller cones as carriers (12) for a plurality of distinguishable types of drag cutters (14,16). The roller cones (12) are each coupled to a mechanism (32,46,56) which selectively allows rotation of the roller cones (12). The roller cones (12) are otherwise fixed and as the bit (10) is rotated, the drag cutters (14) are brought into operative engagement with the rock formation. However, where the roller cones are selectively allowed to rotate, rotation of the drag bit (10) rotates the roller cones (12) to thereby bring a second set of drag cutters (16) into an operative configuration for cutting the rock formation. A mechanism (58,64) then selectively locks the roller cones (12), to prevent further rotation, thereby keeping the second set of drag cutters (16) fixed in place. By selectively permitting rotation and preventing rotation of the roller cones (12), a plurality of sets of drag cutters (14,16) can be brought into an operative configuration for cutting the rock formation. Therefore, such a drag bit (10) may be employed to bring drag cutters (14,16) selectively into play to cut different types of rock formation, or to present renewed cutters (16) after an initial set of cutters (14) have been worn by a predetermined degree. Furthermore, rotation of the roller connes (12) may be slowed from that normally expected by application of a drag to each roller cone (12). The drag cutters (14,16) on each roller cone (12) will thereby be sequentially brought into an operative cutting configuration with respect to the rock formation and where will be evenly distributed among all the drag cutters (14,16) diposed on each roller cone (12).

In a method of assessing drilling conditions during a drilling operation measurements of torque applied (TOR), weight on bit (WOB), rate of penetration (ROP), and rotation speed (ROT) are gathered. Computed therefrom is a history (60, 61) of points (x, y) where y = (TOR/WOB) and y = (ROP/ROT) : y being a derived constant indicative of down hole geometry. Trends in this history are monitored to assess drilling conditions. For example in soft plastic rock migration 62 towards the origin and in hard plastic rock migration 63 towards the abcissa, is indicative of drill bit wear.