Abstract:
An apparatus and method for evaluating a formation is presented. The apparatus comprises a tubular string deployed into a wellbore penetrating the formation, where the tubular string has a longitudinal flow passage therethrough. A flow sub in the tubular string provides fluid communication between the longitudinal flow passage in the tubular string and an annulus between the tubular string and a wall of the wellbore. A wireline tool is attached proximate a bottom end of the flow sub. A telemetry module proximate the flow sub provides communication between the wireline tool and a surface system, without the use of a wireline to the surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     This invention relates generally to logging of subsurface reservoirs and more particularly to pipe conveyed logging.  
         [0005]     2. Description of the Related Art  
         [0006]     Ordinarily, gravity is used to pull logging tools along and into a well borehole for conducting logging operations. When a well is highly deviated from vertical, the force exerted by gravity may not be sufficient to draw the logging tool through a deviated portion of the well. Many oil wells are deviated. For example, an offshore platform commonly has many wells drilled from the platform into various portions of a targeted formation that surrounds the location of the platform. While some of the wells might be approximately vertical, most of the wells extending from the platform will deviate at various angles into the formations of interest and some may involve deviations up to, or above, horizontal. Gravity conveyed logging tools supported on wirelines lose the effect of gravity for forcing the tool through the hole and simply do not have sufficient motive force to traverse the deviated hole to the zone to be logged. In many instances, the logging tool must be pushed through the deviated well to the zone of interest to ensure that the logging tool is located at the requisite location in the deviated hole. It is desirable therefore that the logging tool be fixed to the end of a string of sufficiently stiff pipe to log along the deviated well at the zone of interest. In many cases, this requires using large pipe, such as drill pipe, to have the stiffness required for logging these sections.  
         [0007]     A known method for logging highly deviated wells, disclosed in U.S. Pat. No. 4,457,370, to Wittrisch, consists of the following steps. A well logging tool is secured to the bottom of a section of drill pipe, inside a protective sleeve, and the tool is lowered into the well as additional sections of pipe are assembled. An electrical connector attached to the end of a wireline cable is then inserted into the drill pipe, the cable is passed through a side entry sub mounted on top of the drill string and the connector is pumped down through the drill pipe into engagement with a mating connector attached to the logging tool to effect connection of the tool to the cable and therefore the surface control equipment. Then other sections of drill pipe are added, the portion of the cable above the side entry sub running outside the drill pipe, until the tool reaches the bottom of the section to be logged. Then the logging operation is performed as the drill pipe is moved through the desired section.  
         [0008]     The running of the cable and the additional care and complexity required to protect the cable during pipe movement increase the time required to obtain a log. In addition the making of a wet connect is commonly prone to failure requiring additional time and effort to correct.  
         [0009]     There is a demonstrated need for providing an apparatus and method for logging a highly deviated wellbore that does not require the running of a wireline cable or the making of a wet connect.  
       SUMMARY OF THE INVENTION  
       [0010]     In one aspect of the present invention, an apparatus for evaluating a formation comprises a tubular string deployed into a wellbore penetrating the formation, where the tubular string has a longitudinal flow passage therethrough. A flow sub in the tubular string provides fluid communication between the longitudinal flow passage in the tubular string and an annulus between the tubular string and a wall of the wellbore. A wireline tool is attached proximate a bottom end of the flow sub. A telemetry module proximate the flow sub provides communication between the wireline tool and a surface system, without the use of a wireline to the surface.  
         [0011]     In another aspect, a method for evaluating a formation comprises deploying a tubular string into a wellbore penetrating the formation. Fluid communication is provided between a longitudinal flow passage in the tubular string and an annulus between the tubular string and a wall of the wellbore using a flow sub attached to the tubular string. A parameter of interest is measured with a wireline tool attached to the tubular string below the flow sub. Communication between the wireline tool and a surface system is accomplished without the use of a wireline.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     For detailed understanding of the present invention, references should be made to the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein:  
         [0013]      FIG. 1  is a drawing of a logging system according to at least one embodiment of the present invention;  
         [0014]      FIG. 2  is a blown up portion of bottom assembly  30  of  FIG. 1 ;  
         [0015]      FIG. 3  is a drawing showing an example of multiple sample tanks in a formation test tool; and  
         [0016]      FIG. 4  is a block diagram of the interrelationship of several components of the present invention.  
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0017]      FIGS. 1 and 2  show an exemplary embodiment of the present invention. Rig  5  supports a string  13  of jointed pipe in borehole  15 , also called a wellbore, that extends through formation  20 . As shown, borehole  15  is highly deviated and may include substantially horizontal sections. As used herein, highly deviated refers to wellbores that are deviated from vertical by about 70 degrees, or more. String  13  is made up of pipe sections  10  joined together at threaded connections  12 . The pipe may be drill pipe of the type known in the art. String  13  extends in borehole  13  into a subterranean formation  20 . Bottom assembly  30  is attached to the bottom of string  15  and comprises telemetry module  35 , and flow sub  31 . Attached below flow sub  31  are wireline logging tools  32 A and  32 B. As one skilled in the art will appreciate, and as used herein, a wireline tool is intended to be a tool designed to be commonly deployed into and out of the wellbore on an electrical wireline cable, and is distinguished from tools designed for use during measurement while drilling (MWD) operations. Commonly, wireline tools are not designed to survive the shock, vibration, and torsion of the drilling operation, as required by MWD tools. It is understood, in the context of the present invention, that minor mechanical modifications to a wireline tool to mechanically interface the tool for the present invention, do not alter the nature of the tool as a wireline tool.  
         [0018]     As shown, tool  32 A is a formation test tool. Logging tool  32 B comprises a logging tool that may include, but is not limited to, at least one of: a nuclear magnetic resonance logging tool (NMR); a resistivity tool; and a nuclear density tool. Such tools are used to determine various parameters of interest of the formation including, but not limited to: formation resistivity, formation porosity, and formation permeability. Multiple wireline logging tools may be connected together in a logging string below flow sub  31 . It should be noted that there is no significance to the specific location of particular logging tools in the logging string. For example, if multiple wireline tools are connected below flow sub  31 , formation test tool  32 A may be located at any location in the logging string.  
         [0019]     Surface pump  3  pumps fluid  38  through string  13  and down through bottom assembly  30 . Fluid  38  exits through flow port  50  in flow sub  31  into the annulus between the string  13  and the wall  14  of borehole  15  where it returns to the surface. While only one flow port  50  is shown, additional ports are located around the circumference of flow sub  31 . Energy conductor  51  is disposed within the body of flow sub  31  and enables power and information to be communicated between wireline logging tools  32 A and  32 B and pulser  53 , described below. Alternatively, multiple conductors may be routed in similar fashion.  
         [0020]     Fluid  38  provides flow energy to power turbine/alternator  52  (shown in cutaway inside telemetry module  35 , and in  FIG. 2 ) to generate sufficient electrical power to operate the downhole logging tools and other downhole devices described herein. Such turbine/alternators are known in the art and are not discussed, in detail, here.  
         [0021]     Telemetry module  35  also contains oscillating shear valve pulser  53 , see  FIG. 2 , wherein rotor  60  oscillates proximate stator  61  to restrict a portion of flow of fluid  38  thereby generating pressure signals  41  that propagate to the surface through fluid  38 . Pressure signals  38  are detected by transducer  7  that is in fluid communication with the output flow line of pump  3 . Transducer  7  is commonly a pressure transducer of a kind known in the art. Alternatively, transducer  7  may be a flow transducer in line with the pump output detecting changes in flow related to pressure signals  41 . For additional details of the operation of oscillating shear valve pulser  53 , see U.S. Pat. No. 6,626,252, assigned to the assignee of this application and which is incorporated herein by reference. While described herein as used with a shear valve pulser, any suitable downhole mud pulser is intended to be within the scope of the present invention. Such pulsers include, but are not limited to: positive pulsers, negative pulsers, and continuous, also called siren, pulsers. In addition, surface located downlink pulser  4  transmits pulses  42  from the surface controller  8  to the downhole system. Pulses  42  contain instructions and status information used for operating the downhole system.  
         [0022]     Alternatively, other types of transmission schemes known in the art, that do not employ a wireline connection between the surface and the wireline tool, are intended to be within the scope of the present invention. These include, but are not limited to: acoustic transmission through the pipe wall and electromagnetic telemetry.  
         [0023]     In one embodiment, wireline tool  32 A is a formation test tool such as those described in U.S. Pat. Nos. 5,303,775; 5,377,755; 5,549,159; 5,587,525; 6,420,869; 6,683,681; 6,798,518; and published application US 2004/0035199 A1, each of which is assigned to the assignee of this application, and each of which is incorporated herein by reference. Anchors  36  and sample probe  34  are extendable from the body of tool  32 A to force sample probe  34  into contact with wellbore wall  14  and hence into fluid communication with formation  20 . In one embodiment, as illustrated in  FIG. 3 , the tool  32 A of  FIG. 1  is shown to incorporate a bi-directional piston pump mechanism shown generally at  124  which is illustrated schematically. Within the tool  32 A is also provided at least one and preferably a plurality of sample tanks such as exemplary tanks  126  and  128 , which may be of identical construction if desired. The piston pump mechanism  124  defines a pair of opposed pumping chambers  162  and  164  which are disposed in fluid communication with the respective sample tanks via supply conduits  134  and  136 . Discharge from the respective pump chambers to the supply conduit of a selected sample tank  126  or  128  is controlled by electrically energized three-way valves  127  and  129  or by any other suitable control valve arrangement enabling selective filling of the sample tanks. The respective pumping chambers are also shown to have the capability of fluid communication with the subsurface formation of interest via pump chamber supply passages  138  and  140  which are defined by the sample probe  34  of  FIG. 1  and which are controlled by appropriate valving. The supply passages  138  and  140  may be provided with check valves  139  and  141  to permit overpressure of the fluid being pumped from the chambers  162  and  164  if desired. While described with two sample tanks, additional sample tanks may be added as desired. Additional details of the operation and design of tool  32 A are contained in the incorporated references. Parameters of interest of the sampled fluid and the formation may be determined with sensors such as, for example, optical sensors, density sensors, pressure sensors, and temperature sensors incorporated in tool  32 A. The parameters include, but are not limited to, formation pressure, sample fluid refractive index, sample fluid bubble-point, sample fluid density, sample fluid resistivity, and sample fluid composition.  
         [0024]     In one embodiment, see block diagram in  FIG. 4 , wireline tools  32 A-D are substantially unmodified for use in the present invention. As such, the power, commands, and data transmission to and from wireline tools  32 A-D are substantially the same as if the tools were connected by a conventional wireline to the surface. This capability allows use of a variety of off-the-shelf logging tools in the present invention. Downhole controller  405  contains suitable circuitry in interface module  406  to emulate the appropriate functions necessary to operate and control wireline tools  32 A-D. Controller  405  also comprises a processor  407  and memory  408 . At least a portion of memory  408  contains programmed instructions for use by interface module  406  in the control of the operation of wireline tools  32 A-D. Additional circuitry (not separately shown) is adapted to receive power form turbine-alternator  52  and appropriately distribute the power to the downhole components. Additional circuitry and instructions stored in downhole controller  405  are used to process the measurement data received form wireline tools  32 A-D and to format this information for transmission by the mud pulse system to the surface. In addition, because the volume of data collected by the wireline tools  32 A-D is commonly orders of magnitude greater than the capacity of the telemetry channel  401 , when using mud pulse, the measurement data or suitable subsets thereof may be stored in memory  408  for later retrieval when the tools are returned to the surface. Programmed instructions resident in controller  405  are used to determine the appropriate transmission and storage protocols.  
         [0025]     In one embodiment, surface system  400  contains surface controller  8  that sends commands via downlink pulser  4  to command initiation of various downhole functions, such as, for example performing a formation test. The commands, encoded as pulses  42  are received by a suitable sensor in telemetry module  35 , such as for example, a pressure sensor (not separately shown). Once the commands are received and interpreted, downhole controller  405  assumes substantially autonomous control of the formation test. This may include data acquisition and interpretation to determine that a suitable result is obtained. Instructions and decision rules programmed into controller  405  are used to control this operation. Other downlink commands may, for example, cause changes in the encoding and pulsing format to enhance detection at the surface.  
         [0026]     While described herein as a system used in a highly deviated wellbore, it is intended that the invention described herein is also to be used for deploying heavy wireline tools, or heavy strings of tools, that may be too heavy to be safely conveyed into and out of wellbores that are not highly deviated, including vertical wellbores.  
         [0027]     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. It is intended that the following claims be interpreted to embrace all such modifications and changes.