Abstract:
A device for the quantitative analysis of debris preferably produced while drilling, comprising means for the progressive collection of debris, means for the progressive weighing of collected debris, means for unloading the same preferably in a discharge channel, and a support structure for the device wherein said means for the collection of the debris comprise a collection tray which is capable of performing two types of movement: a rotation movement around an axis which allows alternate loading and unloading of debris and a backward movement which is simultaneous with the rotation movement, thereby allowing for a decisive reduction in the overall vertical dimension of the structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of the priority filing date of Italian patent application n° MI2010A000736 filed on Apr. 29, 2010 in the name of Geolog SpA. 
       FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable 
       SEQUENCE LISTING OR PROGRAM 
       [0003]    Not Applicable 
       STATEMENT REGARDING COPYRIGHTED MATERIAL 
       [0004]    Portions of the disclosure of this patent document contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office file or records, but otherwise reserves all copyright rights whatsoever. 
       BACKGROUND 
     Field of the Invention 
       [0005]    The present invention relates to a device for the quantitative analysis of debris produced while drilling a well. Said device is of the stand-alone type, i.e. able to function in an independent manner from other devices such as a data acquisition unit. 
         [0006]    At the current state of art, the drilling of soil is commonly performed with a rotary system, i.e. through the use of a rotating drill bit screwed to the end of a progressive series of drill rods. Recently, a new technique has been introduced that allows wells to be formed in a way that does not follow a trajectory perpendicular to the drilled surface, but instead a deviated trajectory. Said wells develop in excess of 35,000 feet in depth in an almost horizontal manner through the progressive curving of the rods. 
         [0007]    When the drilling reaches such depths, the augers are subjected to torsional torques far greater than those following a vertical trajectory. In these cases, it is of capital importance to adjust the work parameters of the drilling in real time, such as the speed of rotation and penetration of the auger, the dynamic of circulation of the fluids and their rheological properties. In particular, it is of vital importance to check the geometry of the well excavated and the behaviour of the rock walls that define the internal surface of the well. 
         [0008]    In order to be able to contrast the thrust force of the formations traversed and the fluids contained therein, a drilling fluid is fed into the well to contrast the pressure of the hydrocarbons. Said fluid also serves to transport debris produced during drilling outside of the well. The elimination of the debris is fundamental because an accumulation of debris in the gap between the auger and the walls of the well causes an increase in the resistance torque, creating a risk of blockage and breakage of the auger itself. 
         [0009]    The variation in volume of the well during drilling can be expressed by the following relation: 
         [0000]    
       
         
           
             
               
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         [0000]    where V(t) represents the volume of the well in the instant t, S the area of the section of the well at the instant t and the depth x and Q is a source term. 
         [0010]    It is clear therefore that the variation of the volume of the well in the unit of time (dV(t)/dt) is equal to the sum of a source term Q and of the product of the area S of the section of the well at the same depth and at the same instant and the advancement dx dt of the auger in the infinitesimal interval of time dt. 
         [0011]    At the mouth of the well, it is possible to measure the volume v of the debris transported by the drilling fluid, with a certain delay τ 2  in relation to the instant t. This delay is due to the speed of circulation of the fluid which has to transport the debris as far as the mouth of the well and to its rheological properties. 
         [0012]    It is clear that the source term Q will be equal to the difference between the variation in the volume of the well and the volume of the debris transported by the drilling fluid; said source term Q being able to supply fundamental information for monitoring the drilling. In fact, when Q is negative, it means that a dangerous accumulation of debris in the well is probably occurring and there is a risk of the auger breaking. If, instead, Q is positive, there has probably been a landslide inside the well and therefore the walls are unstable. 
         [0013]    This type of monitoring or quantitative analysis of the debris is particularly important in deviated drilling because the well is very long and the problems of stability and cleanliness of the hole are accentuated. 
         [0014]    The quantitative analysis of the debris, i.e. measurement of the weight of the debris and therefore of its volume, is carried out by means of specific machinery located at the well mouths. When the drilling fluid which carries the debris reaches the surface, said fluid traverses special vibrating screens which separate the solid debris from the liquid. Said debris is then conveyed onto apparatuses for weighing. 
         [0015]    One of the first solutions provided by the market was that described in document EP0995009 in the name of Geoservices. Said device provides for the use of means for collecting the debris and means for measuring their weight in a continuous manner. Said means for collecting debris comprise a tray rotating around an axis, means for tilting said tray so as to empty it and means of driving said means for tilting the tray. Connected to said means for tilting the tray is a measuring cell able to measure the bending moment of the tray in relation to its axis of rotation, it then being possible to calculate the weight of the debris based on the value measured from said bending moment. 
         [0016]    The measured weight of the debris based on the bending moment, as occurs in the device described in EP0995009, is, however, imprecise due to the uncertainty of the location of the centre of mass of the debris distributed on the tray in relation to the axis of rotation of the same. 
         [0017]    Because the surface of the tray must have a width equal at least to standard vibrating screens and a certain volume is required for the tray to perform its rotation, the dimensions of the entire structure of the device (described in the document in the name of Geoservices) are necessarily considerable. Consequently, in many operating situations in which there is a real lack of space, it is not possible to use an instrument such as that described in EP0995009; thereby abandoning an important supply of information derived from quantitative analysis of drilling debris. 
         [0018]    New ideas were introduced into the market, the most important of which is that described in U.S. Pat. No. 1,366,349 in the name of Geolog S.p.A. This patent relates to a device for the quantitative analysis of debris provided with means for collecting debris comprising a conveyor belt wound in a manner of a track on at least two rollers and means for measuring the weight of the debris comprising at least four extensometric cells. 
         [0019]    Said extensometric cells are arranged preferably at the four corners of a base upon which the support structure of the device is placed in order to perform a direct measurement of the weight force exerted on the conveyor belt. 
         [0020]    In this way, some of the limitations of the Geoservices device are overcome because the systematic imprecision, due to the uncertainty of the location of the centre of mass of debris distributed on the tray in relation to the axis of rotation, is eliminated. 
         [0021]    Despite the advantages of the device of U.S. Pat. No. 1,366,349 in the name of Geolog S.p.A over other devices for weighing debris by traditional systems, there are still some elements to be improved, in particular, the considerable bulk and, therefore, flexibility of use in all working environments including the most critical and restrictive conditions. 
         [0022]    Moreover, devices for the quantitative analysis of debris present in the art cannot be used in stand-alone form, i.e. independently from other services. Instead, they must be supported by a data acquisition unit. 
       BRIEF SUMMARY OF THE INVENTION 
       [0023]    The object of the present invention is to provide a device for the quantitative analysis of debris produced in the drilling of a well, which is capable of operating under restrictive conditions as in the case of the new generations of drilling plants characterised by extremely reduced and complex geometries and distribution of space, e.g., deep sea drilling plants. 
         [0024]    The abovementioned object of the present invention is achieved by reducing the vertical overall dimension of the equipment, while maintaining all functions of the system. 
         [0025]    Another object of this device is to be able to install it in a manner totally independent manner from other services, i.e. in stand-alone form, by limiting the dimensions of the equipment and control system so they are suitable for normal office space. 
         [0026]    These and other objects are achieved by a device according to the present invention for the quantitative analysis of debris, preferably produced while drilling, comprising means for the progressive collection of debris, means for the progressive weighing of collected debris, means for the periodic unloading of the debris, and a support structure for the device, characterised in that: 
         [0027]    said means for the collection of debris comprise a collection tray capable of performing two types of movement: a rotation movement around an axis which allows alternate loading and unloading of debris and a backward movement which, due to simultaneous movement with the rotation movement, permits a decisive reduction in the overall vertical dimension of the structure. Because the backward movement and rotation movement are simultaneous, the tray level is lowered during the loading phase, in fact, to a height of approximately 15 cm from the walking surface. 
         [0028]    Although this is a complex movement, this technical solution reduces to a minimum the number of moving parts (joints, hinges, bearings), thereby ensuring simultaneous protection against the entry of fluids (slurry) that could cause friction and abrasions. 
         [0029]    Said means for the weighing of the debris comprise at least four sensing elements arranged in such a way as to take a direct measurement of the weight force exerted on the surface of the plate; the plate is made from a steel sheet which varies from 2 to 3 mm in thickness, completely unrestrained from the rest of the structure, dimensioned and resting on the four sensing elements in such a way as to guarantee the total absence of parasite twisting moments. The measurement therefore takes place in a direct and homogeneous manner under the surface of the plate, nor is it influenced by external inertias or vibrations, therefore guaranteeing an electrical signal free from noise. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    Said means for the unloading of the debris comprise at least one assembly for actuation of said collection plate. These and other advantageous features of the present invention will be made clearer on reading the following detailed description of a preferred embodiment, given by way of a non-limiting example, 
           [0031]      FIG. 1  shows schematically a drilling plant wherein the position of the device for the quantitative analysis of the debris according to the present invention is highlighted; 
           [0032]      FIG. 2  is a schematic front view of the device for quantitative analysis of debris; 
           [0033]      FIG. 3  is a side view (from the side of the box which houses the pneumatic part) of the device for quantitative analysis of debris of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]      FIG. 1  shows schematically a drilling plant  1 , wherein the device for the quantitative analysis of the debris  2  according to the present invention can be positioned. The drilling fluid  3  follows the following path (indicated in the drawing with arrows): the drilling fluid  3  flows in the hollow interior of the drilling column  4 , and exits from the tool  5 . The drilling fluid  3  draws the debris of the rock as far as the surface, after having risen up in the annular space existing between the drilling column  4  and the walls of the well. Having reached the surface, the drilling fluid  3  traverses the vibrating screens  6 , consisting in general of a series of vibrating sieves aimed at the separation of the drilling fluid from the solid debris. The debris is collected by the device for the quantitative analysis  2  according to the present invention. 
         [0035]    Referring to  FIGS. 2 and 3  the device for the quantitative analysis of debris of the present invention comprises: 
         [0036]    a collection tray, preferably in steel ( 7 ), 
         [0037]    a forks surface ( 8 ). 
         [0038]    four load cells ( 9   a ,  9   b ,  9   c ,  9   d ), 
         [0039]    a rotating shaft ( 10 ), 
         [0040]    a box which houses the pneumatic part ( 11 ), 
         [0041]    a box which houses the electronic part ( 12 ). 
         [0042]    The tray ( 7 ) is advantageously dimensioned in such a way that its length coincides substantially with the transverse dimensions of the discharge channel of the vibrating screens, from which the flow of debris exits continuously, while its width allows for the accumulation of a quantity of debris sufficient for obtaining weight measurements that can be interpreted. The tray is preferably made with AISI 304 stainless steel, which does not deteriorate as a result of chemical attack produced by substances dissolved in residual drilling fluid and by the abrasive action of the debris itself. The tray has rear discharge ports (intermittent millings) which allows liquid to seep out of the slurry, retaining the solid. 
         [0043]    Said tray ( 7 ) is provided, moreover, with two lateral fins ( 13   a ) and ( 13   b ) which serve in fact to retain the debris laterally, preventing leakage thereof. The position of the tray when collecting slurry is slightly slanted in such a way as to drain the liquid part not involved in the measurement. The slant of said tray can be regulated. 
         [0044]    Referring in particular to  FIG. 3 , the actuation assembly which generates the movement of the tray ( 7 ) comprises: 
         [0045]    a pneumatic piston ( 14 ), 
         [0046]    a spherical joint ( 15 ), 
         [0047]    a connecting rod ( 16 ) connected to the spherical joint integral by means of a through pin with a rotation shaft ( 17 ). 
         [0048]    The movement of the tray ( 7 ) is essentially generated by the compressed air piston ( 14 ), which pushes or pulls the connecting rod ( 16 ) via the spherical joint ( 15 ), according to whether it is loaded or unloaded. This piston ( 14 ) is actuated by a solenoid valve Eex-i coupled to a distribution manifold, which by releasing pressurised air at the two inlets of the pneumatic piston ( 14 ) determines the actuation of the piston, and therefore the movement of the tray. 
         [0049]    The excitation of the solenoid valve is determined by the stand-alone control system which allows the following parameters to be changed: loading time, unloading time, weight limit. 
         [0050]    The tray is attached to the load cells by means of vibration dampers whose function is to insulate against external vibrations and compensate possible thermal expansions. 
         [0000]    The four cells are in turn attached to a forks surface ( 8 ), integral yet misaligned in relation to the rotating shaft ( 10 ). 
         [0051]    The device for quantitative analysis of debris according to the present invention is also equipped with a hydraulic circuit for supplying pressurised water, not shown in the drawings, which feeds the nozzles ( 18 ) for washing the tray. Said nozzles ( 18 ) are placed on a horizontal pipe with a length equal to that of the tray, said pipe being attached by means of a system having an adjustable slant. 
         [0052]    The important function of said nozzles ( 18 ) will be made clearer by reading the rest of the description. 
         [0053]    The system at the two lateral ends terminates with two distinct boxes integral with the whole structure: one of said boxes ( 11 ) houses the pneumatic part including the solenoid valve, while the other one ( 12 ) contains the electronic part. 
         [0054]    The box which houses the pneumatic part ( 11 ), hereinafter referred to, for simplicity, as pneumatic box, is provided with external inlets/outlets for the air and water. The box which houses the electronic part ( 12 ), hereinafter referred to, for simplicity, as electronic box, is designed in such a way that passage via cable glands is possible both of the cables for the transmission of the electrical signal and of the cable for supplying the solenoid valve. 
         [0055]    The pneumatic box ( 11 ) is provided with three pushbuttons which can be actuated by the external operator and are positioned on the closure door. 
         [0056]    Said pushbuttons are: an actuation pushbutton, a pushbutton for stopping working, and an emergency pushbutton for the instantaneous switching-off of the device. 
         [0057]    It is also possible to open the pneumatic box and switch the function of the solenoid valve from automatic (normal working condition) to manual. 
         [0058]    The manual operating mode (via a screw able to perform a 90° rotation) allows said device to be directly managed, making it possible to simulate movement of the tray by pressing the start and stop pushbuttons to perform tests (for faults and/or leaks). 
         [0059]    On the other hand, the automatic mode provides for the setting of work parameters via a workstation in a remote position (stand-alone system) as will be explained in greater detail below. 
         [0060]    The device for the quantitative analysis of debris produced while drilling according to the present invention is designed to incrementally measure the weight of the debris or of the ratio between the variation of the weight and the interval of time in which said variation is measured. The increment of time of collection or the maximum value of the increment of the weight is pre-selected by the user on a case by case basis. Once the solid phase has been separated from the liquid phase of the material which has exited the mouth of the well, the vibrating screens discharge said solid phase (i.e. the debris) directly onto the collection surface of the tray ( 7 ). 
         [0061]    Said tray, during the phase of collection, is immobile in a horizontal position, with a slight slant upwards, while the four extensometric cells generate a voltage signal correlated to the weight of the debris which is progressively collected. Once this weight reaches the maximum limit set, or the interval of time set has passed, the unloading phase takes place. In this phase, the pneumatic piston ( 14 ) is actuated automatically and rotates the shaft ( 10 ) which, in turn, generates the backward and rotation movements of the forks surface ( 8 ) which is integral with the four load cells and the relative tray above. The time in which the tray is maintained in a vertical position, i.e. in position of unloading, is predetermined. 
         [0062]    During the phase of unloading, the nozzles ( 18 ) spray pressurised water downwards, in the rear part of the tray ( 7 ). Said water facilitates the detachment and sliding of any residue. The elimination of the residue is of considerable importance in that the mass of said residue would continue to condition the weight signal during the subsequent phase of collection. The unloading phase foresees a span of time such as to allow adequate washing of the tray. Said span of time, which is selected by the operator, depends essentially on the quality of the debris collected. 
         [0063]    The work parameters of the device for the quantitative analysis of debris are selected by the user via a workstation in a remote location, which also receives the signal coming from the extensometric cells. Said workstation is provided with dedicated software for the acquisition, processing and storage in memory of the signals coming from the device for the quantitative analysis of debris. Said software also allows for the visualisation of the cumulative volume of debris as a function of time, the cumulative volume of debris as a function of depth and the theoretical profile of the well excavated. 
         [0064]    A further advantage of this embodiment, moreover, is that of allowing for the maintenance or replacement of the extensometric cells solely by removal of the tray, an operation which can be performed with extreme rapidity and ease and which does not entail the movement of large weights. 
         [0065]    Obviously all the known elements described above and used in the present device can be replaced by technically equivalent elements, without altering the functional principles of said device, as claimed herein. 
         [0066]    The materials with which the single components are made are known in the art and are suitable, or certified, for operating in highly aggressive site conditions. Any variations in the materials of the components do not alter in any way what is described and claimed herein.