Abstract:
An integrated, single collar measurement while-while-drilling tool is presented that comprises formation sensors, directional sensors, pressure sensors, a mud pulse telemetry device, and a turbine-generator power device configured in a single collar housing that is no longer than a standard drill collar. No electrical connections are made across drill collar tool joints. The tool provides high reliability and ease of transportation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to drilling systems and more particularly to a system of drilling boreholes having a measurement-while-drilling (“MWD”) tool wherein the MWD tool has formation sensors, directional sensors, a power source, and a telemetry device integrated in a single tool no longer than a standard drill collar.  
           [0003]    2. Description of the Related Art  
           [0004]    Those skilled in the art have long recognized the importance of obtaining various borehole measurements during the course of a drilling operation. Typically, these measurements include such data as the weight imposed on the drill bit, the torque applied to the drill string, the inclination and azimuthal direction of the borehole interval that is then being drilled, borehole pressures and temperatures, drilling mud conditions as well as formation parameters including, but not limited to, resistivity and natural gamma emission of the earth formations being penetrated. Heretofore most of these measurements were obtained either by temporarily positioning special measuring devices in the drill string or by periodically removing the drill string and employing suitable wireline logging tools.  
           [0005]    In recent years, however, the drilling technology has advanced sufficiently that these measurements can now be readily obtained by so-called measurement-while-drilling or “MWD” tools that are tandemly coupled in the drill string and operated during the drilling operation. Several MWD tools presently in commercial operation typically include a thick-walled tubular body carrying various sensors and their associated measurement-encoding circuitry which is preferably positioned in the drill string just above the drill bit for measuring the conditions near the bottom of the borehole. These commercial tools generally employ a selectively-operable acoustic signaler which is cooperatively arranged in the tool body for successively transmitting encoded measurement signals through the drilling mud within the drill string to the surface where the signals are detected and recorded by suitable surface instrumentation.  
           [0006]    The typical commercial MWD tool is arranged as a multi-sectional tool having various special-purpose cartridges that are respectively housed in separable thick-walled bodies and suitably arranged to be coupled together in various combinations for assembling an MWD tool capable of obtaining one or more selected measurements. The multiple sections require both mechanical and electrical connections, such as the prior art arrangement shown in FIG. 1. It is essential that the electrical connectors in the tool bodies be protected from damage. A common problem is that when any tool is assembled while hanging in the slips on a rotary table, the threads on these thick-walled bodies will be damaged from time to time even though every precaution is used in handling the bodies. If the damage to the threads is not severe, the tool body may be returned to service after the threads are redressed. If the damage is more serious, the tool body must be reconditioned either by cutting off the damaged threads and rethreading the damaged end portion or by replacing the entire threaded end portion. In any event, once the tool body has been reconditioned, its overall length will be changed; and, before that body can be reused, some modification must be made to the connector or to any cartridge that is to be subsequently placed in that body before other tool bodies can be utilized with the reconditioned body. Another problem stems from the making and breaking of electrical connections outside of a protected environment, such as on a rig floor. Moisture or other contaminants typically cause reduced reliability of such connections. It will be appreciated that electrical connections between multiple tool sections, at the rig site, are a major reliability issue with MWD service.  
           [0007]    The methods and apparatus of the present invention overcome the foregoing disadvantages of the prior art by providing an integrated MWD system which provides the basic downhole sensors in a single collar section. In addition, all tool electrical connections are made up in a controlled environment.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention contemplates an integrated measurement while drilling tool that comprises formation sensors, directional sensors, pressure sensors, a telemetry device, and a power device configured in a single collar housing that is no longer than a standard drill collar.  
           [0009]    In a preferred embodiment, the integrated, single collar tool comprises a collar housing that is no longer than a standard drill collar that is inserted in a downhole drilling assembly. A plurality of sensors are coupled to the collar housing. The sensors are adapted to measure downhole parameters of interest such as formation resistivity, formation gamma ray emission, bore pressure, annulus pressure, inclination, and azimuth. The sensor measurements are transmitted to a surface processor by a mud pulse telemetry device disposed in the housing. A downhole turbine-generator provides electrical power to the downhole tool.  
           [0010]    In another preferred embodiment, the integrated, single collar tool comprises a collar housing that is no longer than a standard drill collar that is inserted in a downhole drilling assembly. A sonde is installed in a bore in the housing. Multiple sensors and a housing located processor are mounted to the housing. Each sensor has its own conditioning electronics located with it. The sensors are adapted to measure formation resistivity, formation gamma ray emission, bore pressure, and annulus pressure and to transmit the sensor measurements to the housing processor. The housing processor transmits the sensor information to a sonde mounted telemetry processor. The sonde has the telemetry processor and a directional package wherein the directional package provides directional information to the telemetry processor. The telemetry processor acts cooperatively with a mud pulse telemetry device to transmit the directional information and the housing mounted sensor information to the surface processor for use by the operator. A downhole turbine-generator is mounted in the sonde to generate electrical power from the flowing drilling fluid.  
           [0011]    Examples of the more important features of the invention thus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein:  
         [0013]    [0013]FIG. 1 is a schematic of an MWD downhole tool with separate collar sections for each sensor type;  
         [0014]    [0014]FIG. 2 is a schematic of a drilling system according to one embodiment of the present invention; and,  
         [0015]    [0015]FIG. 3 is a schematic of an integrated, single collar MWD tool with all sensors in a single collar section according to one embodiment of the present invention.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0016]    [0016]FIG. 2 shows a schematic diagram of a drilling system  10  having a downhole assembly containing a downhole sensor system and the surface devices according to one embodiment of present invention. As shown, the system  10  includes a conventional derrick  11  erected on a derrick floor  12  which supports a rotary table  14  that is rotated by a prime mover (not shown) at a desired rotational speed. A drill string  20  that includes a drill pipe section  22  extends downward from the rotary table  14  into a borehole  26 . A drill bit  50  attached to the drill string downhole end disintegrates the geological formation  23  when it is rotated. The drill string  20  is coupled to a drawworks  30  via a kelly joint  21 , swivel  28  and line  29  through a system of pulleys (not shown). During the drilling operations, the drawworks  30  is operated to control the weight on bit and the rate of penetration of the drill string  20  into the borehole  26 . The operation of the drawworks is well known in the art and is thus not described in detail herein.  
         [0017]    During drilling operations a suitable drilling fluid (commonly referred to in the art as “mud”)  31  from a mud pit  32  is circulated under pressure through the drill string  20  by a mud pump  34 . The drilling fluid  31  passes from the mud pump  34  into the drill string  20  via a desurger  36 , fluid line  38  and the kelly joint  21 . The drilling fluid is discharged at the borehole bottom  51  through an opening in the drill bit  50 . The drilling fluid circulates uphole through the annular space  27  between the drill string  20  and the borehole  26  and is discharged into the mud pit  32  via a return line  35 . Preferably, a variety of sensors (not shown) are appropriately deployed on the surface according to known methods in the art to provide information about various drilling-related parameters, such as fluid flow rate, weight on bit, hook load, etc.  
         [0018]    A surface control unit  40  receives signals from the downhole sensors and devices via a sensor  43  placed in the fluid line  38  and processes such signals according to programmed instructions provided to the surface control unit. The surface control unit displays desired drilling parameters and other information on a display/monitor  42  which information is utilized by an operator to control the drilling operations. The surface control unit  40  contains a computer, memory for storing data, data recorder and other peripherals. The surface control unit  40  also includes models and processes data according to programmed instructions and responds to user commands entered through a suitable means, such as a keyboard. The control unit  40  is preferably adapted to activate alarms  44  when certain unsafe or undesirable operating conditions occur.  
         [0019]    In the preferred embodiment of the present invention, the downhole drilling assembly  59  (also referred to as the bottomhole assembly or “BHA”) which contains the various sensors and MWD devices to provide information about the formation  23  and downhole drilling parameters, is coupled between the drill bit  50  and the drill pipe  22 .  
         [0020]    Referring to FIG. 2, the BHA  59  also contains downhole sensors and devices in addition to the above-described surface sensors to measure downhole parameters of interest. Such devices include, but are not limited to, a device for measuring the formation resistivity near the drill bit, a gamma ray device for measuring the formation gamma ray intensity, devices for determining the inclination and azimuth of the drill string, and pressure sensors for measuring drilling fluid pressure downhole. The above-noted devices transmit data to the downhole pulser  134 , which in turn transmits the data uphole to the surface control unit  40 . The present invention preferably utilizes a mud pulse telemetry technique to communicate data from downhole sensors and devices during drilling operations. A transducer  43  placed in the mud supply line  38  detects the mud pulses responsive to the data transmitted by the downhole pulser  134 . Transducer  43  generates electrical signals in response to the mud pressure variations and transmits such signals via a conductor  45  to the surface control unit  40 . Alternatively, other telemetry techniques such electromagnetic and acoustic techniques or any other suitable technique may be utilized for the purposes of this invention.  
         [0021]    Referring to FIG. 3, an integrated MWD tool  150  is displayed comprising a sonde  25  mounted in the bore  132  of a drill collar housing  130 . Collar housing  130  is no longer than a standard drill collar (approx. 31 ft.). The sonde  25  comprises a pulser  134 , a turbine-generator  136 , and a directional package  138 , and a telemetry controller mounted (not shown) in a tubular housing  139 . Sonde  25  is supported in the bore  132  by centralizer  101  which rests on an internal shoulder (not shown) of housing  130 . Centralizer  101  serves to support the sonde  25  and to facilitate electrical connection between the sonde  25  and a housing controller  104 . Housing controller  104  contains circuits (not shown), a processor (not shown), and memory. Housing controller  104  interfaces with pressure detection system  140 , resistivity sensor  105 , and gamma ray sensor  110  mounted on the external portion of housing  130 . Controller  104  receives and processes signals from the collar housing  130  mounted sensors, and transmits the processed signals to a telemetry controller (not shown) in the sonde  25 . The electrical connection is made by crossover connector  102 , providing an environmentally protected electrical connection between telemetry controller in the sonde  25  and the housing controller  104  located on the collar housing  130 .  
         [0022]    The telemetry controller (not shown) in sonde  25  contains circuits and processors for receiving information from the housing controller  104  and the directional sensor package  138  mounted in sonde  25 , and for encoding this information, according to programmed instructions, into pressure pulse data for transmission to the surface via pressure pulses generated by the pulser  134 . Directional package  138  comprises sensors (not shown) and conditioning electronics located in sonde  25  for determining the azimuth and inclination of the portion of the drill string, including the collar housing  130 , near the drill bit  50 . Any suitable directional sensors such as accelerometers and magnetometers and/or gyro devices may be used. Such devices are known in the art and are, thus, not described in detail herein.  
         [0023]    The formation resistivity sensor  105  and its associated electronics are mounted in recesses in collar housing  130  and provide signals from which resistivity of the formation near the drill bit  50  is determined. Resistivity sensor  105  is deployed having one or more pairs of transmitting antennas  66   a , 66   b  spaced from one or more pairs of receiving antennas  68   a , 68   b  mounted on collar housing  130  (see FIG. 3). In operation, the transmitted electromagnetic waves are perturbed as they propagate through the formation surrounding the borehole in the vicinity of the resistivity sensor  105 . The receiving antennas  68   a  and  68   b  detect the perturbed waves. Formation resistivity is derived from the phase and amplitude of the detected signals. The detected signals are processed by circuits mounted with the sensor  105  and the output is transmitted to housing controller  104  located on collar housing  130  and then transmitted to encoding circuits in the telemetry controller in sonde  25  for transmission to the surface control unit  40  via pulses generated by pulser  134 .  
         [0024]    Gamma ray sensors  110   a,b  and their associated electronics (not shown) are mounted in recesses in the outer surface of collar housing  130 . The gamma ray sensors  110   a,b  measure the formation natural gamma ray emission using scintillation detectors (not shown). The scintillation detectors are arranged in separate banks on the housing  130  to provide an azimuthal indication of gamma ray emission. Alternatively, Geiger tube detectors may be used to detect formation gamma rays. Both Geiger tubes and scintillation detectors are known in the art. The signals from the gamma ray sensors are processed by the gamma ray electronics and transmitted to housing controller  104  and transmitted to encoding circuits in the telemetry controller in sonde  25  for transmission to the surface control unit  40  via pulses generated by pulser  134 .  
         [0025]    Pressure sensor module  140  is mounted in a recess in collar housing  130 . The recess is adapted to provide suitable fluid porting (not shown) such that both the bore fluid pressure and the annulus fluid pressure can be determined by any suitable pressure sensors and their associated electronics. Such devices are known in the art. The signals from the pressure sensors are processed by the pressure sensor electronics (not shown) and transmitted to housing controller  104  and transmitted to encoding circuits in the telemetry controller in sonde  25  for transmission to the surface control unit  40  via pulses generated by pulser  134 .  
         [0026]    In a preferred embodiment, the pulser  134  partially restricts the drilling fluid flow, thereby generating positive pulses related to the encoded data. The pulses travel to the surface and are detected by transducer  43  and decoded by processor  40  for use by the operator. Alternatively, a negative pulser can be used to transmit data pulses to the surface. Both positive and negative pulsers are known in the art and are not discussed here further. In addition, the sonde  25  contains circuits (not shown) to condition electrical power from the turbine-generator  136  and to appropriately distribute the power to the various downhole circuits and sensors. The turbine-generator  136  intercepts at least a portion of the flow with rotating turbine blades (not shown) thereby turning a generator for producing electrical power sufficient to power the downhole sensors and electronics. Turbine-generators are known in the art.  
         [0027]    This invention provides an MWD tool having directional sensors, formation evaluation sensors, and pressure sensors in a combined sonde/collar housing configuration that is no longer than a standard drill collar and requires no electrical connections to be made across threaded collar joints, a major advantage over prior art tools. In addition, the tool can be made up as a complete assembly in a controlled shop environment and transported to the rig as a finished assembly, obviating the need for unreliable rig assembly.  
         [0028]    The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention. It is intended that the following claims be interpreted to embrace all such modifications and changes.