Abstract:
A hydrocarbon production facility includes: a hydrocarbon well; a hydrocarbon production line including: in the well, a production tube, and on the surface, an evacuation tube from the production tube; on the surface, a source of pressurized gas; an injection line of pressurized gas in the hydrocarbon production line, linked to the source of pressurized gas; a pump for circulation of hydrocarbon from the well hydrocarbon circulation; a pneumatic motor for supplying power to the pump, fitted on the injection line of the pressurized gas and adapted to be rotated by expansion of the pressurized gas. A corresponding production method and an upgrade method of a facility are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a National Phase Entry of International Patent Application No. PCT/EP2014/072006, filed on Oct. 14, 2014, which claims priority to French Patent Application Serial No. 13 59 993, filed on Oct. 14, 2013, both of which are incorporated by reference herein. 
     
    
     BACKGROUND AND SUMMARY 
       [0002]    The present invention relates to a facility and a method for producing hydrocarbon. The present invention also relates to a method for upgrading a hydrocarbon production facility. 
         [0003]    In the field of hydrocarbon production, it is known to use the injection of pressurized gas into a hydrocarbon production well to improve the production of this well. Documents EP 0 756 065 A1 and FR 2 783 557 A1, for example, describe the injection of gas for activation of the hydrocarbon production of a well. Gas injection reduces the hydrostatic pressure of the well to facilitate the extraction of hydrocarbons. However, such method known by activation using gas injection (method designated as well by “gas lift”) may not allow to reduce sufficiently the hydrostatic pressure to operate the well in a satisfactory manner. 
         [0004]      FIG. 1  shows a diagram of different characteristics of the productivity in relation with the fluid pressure in the well bottom hole and the flow rate, named Q. The fluid pressure of the well bottom hole is designated in FIG.  1  by the reference sign BHFP, abbreviation of “Bottom Hole Fluid Pressure”.  FIG. 1  shows three characteristics 102, 112 and 122, of different wells. These wells are different by their gradient of natural lift, as defined by the following equation: 
         [0000]    
       
         
           
             Lg 
             = 
             
               
                 
                   BHP 
                   - 
                   THP 
                 
                 H 
               
               * 
               10.2 
             
           
         
       
     
         [0000]    wherein Lg is the gradient of the well natural lift; 
         [0005]    BHP is the bottom hole pressure in bars (abbreviation of “Bottom Hole Pressure”) 
         [0006]    THP is the wellhead pressure in bars (abbreviation of “Tubing Hanger Pressure”); 
         [0007]    H is the vertical depth of the well in m. 
         [0000]    The characteristics of curves  112  and  122  correspond thus to wells with an Lg lower than the well characteristic represented by the curve  102 , Lg related to the well of the curve  122  being itself lower than the Lg related to the well of the curve  112 . 
         [0008]    Curves  104  and  114  of  FIG. 1  correspond respectively to the performance of a gas lift called light and to the performance of a gas lift called heavy. The light gas lift has two operating points with the well of curve  102  whose point  106  allows a greater flow, Q, of well production. However, the light gas lift has no operating point with wells of lower Lg such as wells of curves  112  and  122 . The low gas lift allows then the operation of wells with a Lg included between 0.6 and 1.0. The positioning of the heavy gas lift ensures then the operation of the well of curve  112  at an operating point  112  but does not allow to operate the well of curve  122  with which it has no operating point. The strong gas lift allows to operate wells with a Lg included between 0.3 and 0.5. In other words, the gas lift, even strong, is insufficient for operating the wells with a too low Lg. 
         [0009]    There is therefore a need for a hydrocarbon production method and facility wherein activation by gas injection is insufficient to obtain a reduction of the hydrostatic pressure of the well allowing the operation of the well. 
         [0010]    Therefore, the invention proposes a hydrocarbon production facility, comprising: 
         [0011]    a well of hydrocarbons; 
         [0012]    a hydrocarbon production line comprising:
       in the well, a production tube, and   on the surface, an evacuation tube from the production tube;       
 
         [0015]    on the surface, a source of pressurized gas; 
         [0016]    an injection line of pressurized gas in the hydrocarbon production line, the injection line being connected to the source of pressurized gas; 
         [0017]    a pump for circulation of hydrocarbon from the well to the hydrocarbon production line; 
         [0018]    a pneumatic motor for supplying power to the pump, disposed on the injection line of the pressurized gas and adapted to be rotated by expansion of the pressurized gas. 
         [0019]    Alternatively, the facility comprises a mechanical transmission shaft connecting the pneumatic motor to the pump. Alternatively, the pneumatic motor is an electric generator. Alternatively, the pump in the well is an electric submersible type or a progressive cavity type. Alternatively, the pump is disposed in the well bottom hole. 
         [0020]    Alternatively, the injection line opens into the well bottom hole, preferably in the production tube of the hydrocarbon production line. Alternatively, the pneumatic motor is at the wellhead. Alternatively, the pneumatic motor is at the well bottom hole. Alternatively, the injection line opens into the evacuation tube of the production line, downstream of the circulation pump. 
         [0021]    The invention also provides a method of operating a hydrocarbon production well activated by gas injection, comprising: 
         [0022]    a) providing pressurized gas from a source of pressurized gas surface; 
         [0023]    b) recovering energy by the expansion of pressurized gas under pressure using a pneumatic motor; 
         [0024]    c) actuating a pump for circulation of hydrocarbon from the well using energy recovered in step b); 
         [0025]    d) injecting expanded pressurized gas in a hydrocarbon production line. 
         [0026]    Alternatively, pressurized gas is at a pressure higher than or equal to 70 bars prior to expansion. Alternatively, pressurized gas is expanded by the pneumatic motor at a pressure less than or equal to 30 bars. 
         [0027]    The invention also concerns an upgrade method of a hydrocarbon production facility, the facility comprising: 
         [0028]    a well of hydrocarbons; 
         [0029]    a hydrocarbon production line comprising:
       in the well, a production tube, and   on the surface, an evacuation tube from the production tube;       
 
         [0032]    on the surface, a source of pressurized gas; 
         [0033]    an injection line of pressurized gas in the hydrocarbon production line, the injection line being connected to the source of pressurized gas; 
         [0034]    the method comprising: 
         [0035]    positioning a pump for circulation of hydrocarbon from the well; and 
         [0036]    positioning, on the injection line of pressurized gas, a pneumatic motor for supplying power to the pump, adapted to be rotated by expansion of the pressurized gas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    Other characteristics and advantages of the invention will appear after reading the following detailed description of the invention exemplary embodiments and with reference to the drawings showing: 
           [0038]      FIG. 1 , a diagram of different characteristics of productivity in relation with the bottom hole fluid pressure and the flow rate; 
           [0039]      FIG. 2 , a schematic sectional view of an embodiment of hydrocarbon production facility; 
           [0040]      FIG. 3 , a schematic sectional view of an embodiment with gas lift of hydrocarbon production facility; 
           [0041]      FIG. 4 , a diagram of the course of the pressure according to the depth in a well for various well operation methods; and 
           [0042]      FIG. 5 , a schematic sectional view of another embodiment with gas lift of hydrocarbon production facility. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    The invention describes a hydrocarbon production facility. With reference to  FIG. 2 , the hydrocarbon production facility  20  comprises a well  22  of hydrocarbons. To lift the hydrocarbons  80  from the well  22 , the facility comprises a production line having a production tube  24  in the well  22  and an evacuation tube  26  on the surface from the production tube  24 . The tube  26  on the surface allows for example the evacuation to a reservoir  28  of the hydrocarbon product storage. Prior to storage, the tube  26  on the surface may also be used to evacuate the products  82 , lifted by the production tube  24  and comprising hydrocarbons  80 , to product  82  separation devices (not shown). The product  82  separation devices may in particular separate water, gas and oil. 
         [0044]    The facility  20  comprises a pump  40  for circulation of hydrocarbon from the well  22  in the production line to facilitate the lift of hydrocarbons  80  by the production tube  24 . This pump  40  may be disposed at the well bottom hole  22  and is designated later in this document by the term “bottom hole pump”. Such a bottom hole pump ( 40 ) ensures or increases hydrocarbon production by the well  22 , particularly where activation by injection of pressurized gas is insufficient to obtain a reduction of hydrostatic pressure, or a back pressure, from the well  22  to operate the well  22 . In an alternative, not shown, the pump  40  may be disposed on the surface of the evacuation tube  26 . Such an arrangement of the pump  40  allows as well to increase the production by lowering the back pressure of the well  22  while facilitating the maintenance of the pump  40  which is then more accessible. 
         [0045]    In the embodiment illustrated in  FIG. 2 , the pump  40  is driven by a turbine  30 . The positioning of the turbine  30  is embodied on one hand in the figures using dashed lines and on the other hand by the schematic representation of blades  32  of the turbine  30 . This turbine  30  is disposed in a line  36  of pressurized gas  38  to be rotated by expansion of the pressurized gas  38 . In other words, the turbine  30  supplies the pump  40  with energy, this energy is derived from the expansion of the pressurized gas  38 . The turbine  30  may be replaced by any other type of pneumatic motor, a pneumatic motor converting energy stored in compressed gas into mechanical energy. The turbine may be replaced by any other pneumatic motor of hydrodynamic type or a pneumatic motor of volumetric type, the pneumatic motor includes then an expansion chamber which volume is variable. The proposed pneumatic motor of volumetric type may thus correspond to a circumferential piston pneumatic motor. To prevent racing, the pneumatic motor, such as the turbine  30 , may be provided with a diversion, otherwise designated by the term “by-pass”. To control automatic opening of the by-pass, the proposed facility may include a speed controller integrated in the pneumatic motor. In particular, in the absence of speed controller, the speed of the turbine or the pneumatic motor may be transmitted on the surface in the form of a sound through the production tube  24  of the well  22 . The transmitted sound may have the impact frequency at each rotation of the pneumatic motor to be a characteristic of the pneumatic motor rotation speed. 
         [0046]    The kinetic energy transmission from the turbine  30  to the pump may be performed using a rotated shaft  42  (shown by dashed lines). This mechanical transmission shaft  42  connects the turbine  30  to the pump  40 . As illustrated in  FIG. 2 , the mechanical connection between the turbine  30  and the pump  40  comprises a reducer  44  for modulating the rotational speed of the shaft  42  causing the actuation of the pump  40 . The shaft  42  is then split into two portions, a portion connecting the turbine  30  to the reducer  44  and another portion connecting the reducer  44  to the pump  40 . Such a reducer may be of magnetic type for obtaining a high conversion ratio. Similarly, the mechanical connection between the turbine  30  and the pump  40  may also include a clutch (not shown). Moreover, to facilitate the kinetic energy transmission from the location of the turbine  30  to the bottom hole pump  40  without being constrained by a straight line trajectory, the shaft  42  may include various joints  46 . 
         [0047]    In the embodiment illustrated in  FIG. 2 , the transmission of energy recovered by the turbine  30  to the pump  40  is then carried out without additional energy conversion. In one alternative embodiment not illustrated, the turbine  30  may be an electric generator. Energy transmitted from the turbine  30  to the pump  40  is then electric enabling to overcome mechanical constraints associated with the use of the mechanical transmission shaft  42  in particular when the well  22  trajectory is too aggressive. According to this alternative embodiment, the bottom hole pump  40  may be of electric submersible type (a pump type also designated by “Electric Submersible Pump”, abbreviated as “ESP”). In all embodiments described above, the bottom hole pump  40  may be of progressive cavity type (a pump type also designated by the “Progressive Cavity Pump” abbreviated as “PCP”). The use of a progressive cavity pump stabilizes the well  22  by enabling direct control of the well  22  flow rate. In comparison to the power electric transmission, the mechanical transmission of the pneumatic motor, as the turbine  30 , to the pump  40  reduces the presence of electric equipment at the well bottom hole. In such case of power mechanical transmission, the lifetime of the facility is improved due to the independence of the proposed facility to such electric equipment at the well bottom hole  22 . 
         [0048]    The pressurized gas  38  driving the turbine  30  from a pressurized gas source  34 , on the surface relative to the well  22 , the source is illustrated herein as a reservoir. However, pressurized gas sources  34  are generally available on the surface in known hydrocarbon production facilities. In fact, the presence of pressurized gas sources on the surface is particularly required when facilities are activated by injection of pressurized gas into the production line (production method also referred to as “gas lift”). 
         [0049]    Eventually, such an energy source being already present on known hydrocarbon production facilities, the proposed facility  20  enables the drive of the bottom hole pump  40  facilitating the production of hydrocarbons and this, in the absence of additional power distribution network. By not using the additional power distribution network, the proposed facility  20  is particularly advantageous when the production facility  20  is remote from any power generation site location or inhabited place. 
         [0050]    A hydrocarbon production upgrade method is particularly provided. Upgrading a hydrocarbon production facility corresponds to the adaptation of existing facilities to the solution described above. The devices already present before upgrading the facility are for example the well  22 , the production line, the pressurized gas source  34  and the pressurized gas  38  injection line  36  in the production line. Such an upgrade method adds the bottom hole pump  40 , or the pump on the surface, and the turbine  30  or other pneumatic motor to these devices already present in the facility to be upgraded. In other words, the method comprises the deployment of the pump  40  in the well  22  or on the surface and the deployment of the pump power supply in the injection line  36  of the turbine  30 . The upgrade method can of course comprise the deployment of any other device described herein and in particular the deployment of one, several or all devices interacting with the pump  40  and/or with the turbine  30 , such as for example the mechanical transmission shaft  42  and the reducer  44 . 
         [0051]    Furthermore, this invention provides as well a hydrocarbon production method incorporating the operation principles of the proposed hydrocarbon production facility  20 . Such method comprises initially the provision of pressurized gas  38  from the pressurized gas source  34 , on the surface. This step allows the recovery of energy already available in production facilities by gas lift. The source  34  may for example provide the gas  38  before expansion at a pressure greater than or equal to 70 bars or about 65 bars. 
         [0052]    This energy is then recovered by the expansion of the pressurized gas  38  using the turbine  30  or any other pneumatic motor. The pressurized gas  38  may be expanded by the turbine  30  to a pressure less than or equal to 30 bars. This recovered energy in kinetic form is forwarded in this form or in another form, such as electric energy, to the pump  40  in the well  22  for its actuation. The bottom hole pump  40  contributes to the lift on the surface of hydrocarbons  80  from the production well though the hydrocarbon production line to the reservoir  28 . 
         [0053]    The gas  38  after expansion may be injected into the hydrocarbon production line. The pressurized gas  38  after expansion has an injection pressure lower than if the pressurized gas  38  is injected into the production line without pre-expansion or excessive pressure such as 70 or 65 bars. 
         [0054]    During a ramp-up phase of the well operation, at the start of the operation of the well  22 , the lower injection pressure prevents an excessive instantaneous flowrate (phenomenon also designated by “steam break through”). Such a phenomenon occurs in effect when the pressure drop provided at the well bottom hole by the gas lift is too important and affects the well productivity. The lower injection pressure also prevents racing in case of instantaneous flashing (phenomenon also referred to by “steam flashing”). 
         [0055]    During a phase of well stimulation (a phase designated also by “boosting”), implemented when the well production  22  begins to decline, the system reduces the sub-cool without risk, difference between the hydrocarbon temperature and the evaporation temperature of said hydrocarbons at the same pressure. The sub-cool may then be lower without any risk of racing, i.e. without risk of vaporization. By limiting the sub-cool, hydrocarbons to be produced are warmer, less viscous and therefore easier to extract. 
         [0056]    The remainder of this document exposes in particular the differences between the embodiments of hydrocarbon production facilities  20  operating according to the preceding method. According to the embodiment of the production facility specifically illustrated in  FIG. 2 , the gas  38  injection line  36  opens into the surface in the evacuation tube  26  of the production line. The expanded pressurized gas  38  is thus injected into the surface portion of the production line called “flow line”. The injection of expanded pressurized gas  38  in the surface portion of the production line can achieve a reduction of the hydrostatic pressure of the production line even when the pressure after expansion is low. 
         [0057]    According to another embodiment illustrated in  FIG. 3 , the pressurized gas  38  is provided to be injected in the production line at the production tube  24 , to activate the production of hydrocarbons  80 . As for the injection line  36  portion disposed in the well  22 , the injection line  36  is in the form of a ring around the production tube  24 . The gas  38  is expanded by the turbine  30  before being injected into the well  22  production line. Similarly to the embodiment illustrated in  FIG. 2 , in  FIG. 3  the production of hydrocarbons is facilitated by the bottom hole pump  40  on one hand and by gas injection on another hand. However, the gas injection in the well  22  production line as illustrated in  FIG. 3  corresponds to a gas lift technique, i.e. activation by gas injection. In particular, in the embodiment illustrated in  FIG. 3 , the injection of expanded gas  38  is carried out at the “well bottom hole” above the location of the bottom hole pump  40 , directly into the production line at the production tube  24 . In all cases, embodiments of  FIG. 2  or  FIG. 3 , the gas injection is performed downstream of the pump in the production line. 
         [0058]    The expression “well bottom hole” is used herein as to characterize close positioning of geological layers forming the hydrocarbon bearing reservoir operated by the well  22 . This expression is used in opposition with the expressions “wellhead” and “on the surface”. The expression “on the surface” characterizes herein the positioning at ground level, above ground or immediately below ground. A device disposed on the surface may thus correspond to a device buried at a negligible depth with respect to the depth of the well. The expression “wellhead” characterizes herein the positioning “on the surface”, directly above the well, i.e. vertically above the well. Thus, the distance between a “wellhead” positioning and a “bottom hole” positioning is substantially equal to the length of the well  22  trajectory. The mixed lines modelling the suspended view of the well  22  in figures separate on one hand the wellhead and the surface, above the mixed lines, from the well  22  bottom hole on another hand below the mixed lines. 
         [0059]    In the embodiment illustrated in  FIG. 3 , the turbine  30  is disposed in the wellhead of the well  22 . For this embodiment as for the embodiment illustrated in  FIG. 2 , the turbine  30  arrangement on the surface prevents that the expansion of pressurized gas  38  at the turbine  30  does not cool the hydrocarbons  80  at the well  22  bottom hole. The cooling of the hydrocarbons  80  by gas may for example result in the formation of deposition, such as the formation of paraffin deposition for the paraffinic hydrocarbons, otherwise designated by the paraffinic raw expression. The embodiments illustrated in  FIGS. 2 and 3  have the advantage of facilitating risk management of deposition which is limited at the injection of expanded gas  38  in the production line, either on the surface of the well or in the wellhead of the well, respectively. 
         [0060]    Furthermore, the embodiment illustrated in  FIG. 3  can optionally have more diameter. Such an embodiment is then particularly preferred for the production of hydrocarbons present in the form of “heavy oil”. For such application to the production of “heavy oil”, the bottom hole pump  40  is preferably of PCP type. The use of the pump  40  of PCP type for the production of “heavy oil” enables a stabilization of activation by gas injection and a better control of the flow, particularly, at the beginning of the production after the injection of pressurized gas  38  in the production line. Moreover, to further facilitate the production of hydrocarbons of “heavy oil” type, in addition to gas lift and bottom hole pump  40 , the pressurized gas  38  may be heated after being expanded by the turbine  30 . 
         [0061]    The positioning of the turbine  30  on the surface also contributes to facilitating the architecture of the facility. In fact, in the mechanical transmission variants of the energy from the turbine  30  to the pump  40 , the reducer  44  may be very bulky, especially where the reducer  44  is of magnetic type. The arrangement of the turbine  30  on the surface allows then the arrangement of the reducer  44  on the surface between the turbine  30  and the pump  40 , the surface being less subject to space constraints than the well  22  bottom hole. 
         [0062]    The proposed facility, especially as illustrated in  FIG. 3 , allows lowering the pressure in the well  22  according to the diagram of  FIG. 4 .  FIG. 4  shows a diagram of the pressure course, P, according to vertical depth, H, in the well  22 . The point BH, an abbreviation of the expression “Bottom Hole”, corresponds to the vertical depth at the well bottom hole. The facility illustrated in  FIG. 3  allows the pressure to follow the curve  140  having a decreased pressure  142  at the depth to which the pump  40  is disposed. This decrease in pressure  142  provides a low pressure of the bottom hole at the point  144 . This low pressure at the point  144  is to be compared to the pressure obtained at the point  132  which is the hydrostatic pressure of hydrocarbons at the well bottom hole. Point  132  is the point of the curve of hydrostatic pressure in dashed lines  130  in depth at the well bottom hole. In other words, the curve  130  corresponds to the pressure course in the naturally-occurring well, i.e. in the absence of particular devices in the well to facilitate the production of the well. The bottom hole pressure obtained using the proposed facility corresponds, relatively to the point  132  of the hydrostatic pressure at the well  22  bottom hole, to a pressure drop  146  (also known as the “draw down”) promoting the extraction of the hydrocarbons from the well  22 . The use of one portion of pressurized gas energy to actuate the bottom hole pump  40  and another portion of the pressurized gas energy used in gas lift allows a double acting extraction of the well  22  hydrocarbons from a single source. 
         [0063]    Upon placement of a conventional gas lift in the well  22 , i.e. using the same pressurized gas  38  but without expansion before injection, the pressure based upon the depth follows the curve in thin lines  134  to reach a bottom hole pressure at point  136 . This bottom hole  22  pressure allows a pressure drop  138  less than the pressure drop  146  permitted by the proposed facility. Double acting extraction from a single source enables then a higher production of the well  22  in comparison to the use of the total energy of the pressurized gas in gas lift. The injection of pressurized gas after expansion corresponds in fact to the use of gas lift in its effective domain, as for pressures in the range of or less than 30 bars, the excess energy is used as mechanical energy for driving the pump  40 . 
         [0064]    Moreover, the higher production may be achieved with levels of pressurized gas  38  pressure in the range of 70 bars or 65 bars. The use of pressure levels in the range of 70 bars or 65 bars limits the risk of erosion of the facility and increases the number of used technologies in comparison to the use of higher pressures in gas lift to obtain an efficiency comparable to the proposed double acting extraction. 
         [0065]    Alternatively to the positioning of the turbine  30  on the surface,  FIG. 5  shows an embodiment of the facility where the turbine  30  is disposed at the well bottom hole. This embodiment is particularly advantageous when hydrocarbons  80  to be produced are very hot. The heat of hydrocarbons  80  to be produced limits the influence on producing hydrocarbon  80  cooling by the injection of expanded pressurized gas  38 . In such case of producing hydrocarbons at a high temperature, in the proposed facility, the pump  40  may be of a high speed roto-dynamic type, preferably to a more expensive electric submersible pump high temperature (abbreviated as “ESP-HT”). The arrangement of the turbine  30  at the well bottom hole may also be considered when it is provided to preheat the pressurized gas  38  in the annular portion of the injection line  36  in order to limit the cooling of hydrocarbons to be produced. In all cases, due to the positioning of the turbine at the well bottom hole, the pressurized gas before expansion is warmer than in the aforementioned embodiments with reference to  FIGS. 2 and 3 . 
         [0066]    The embodiment illustrated in  FIG. 5  with the pneumatic motor at the well  22  bottom hole, illustrated as a turbine  30 , is preferred than the embodiment illustrated in  FIG. 3  with the well  22  wellhead motor for the said phase of stimulating the well  22  when hydrocarbons are heavy oils. In general, the embodiment illustrated in  FIG. 5  is also preferred for the well  22  of standard crudes. Conversely, the embodiment illustrated in  FIG. 3  is preferred for the aforementioned well  22  operation ramp-up when hydrocarbons are heavy oils. 
         [0067]    Of course, the present invention is not limited to the examples and the embodiments described and represented, but is capable of many variants accessible to the person skilled in the art. In particular, the injection of expanded pressurized gas can be carried out for the same hydrocarbon production facility in both the production tube  24  at the well bottom hole and in the discharge tube  26  on the surface. Such a variant corresponds to the combination of embodiments illustrated in  FIG. 2  and  FIG. 3 . 
         [0068]    Furthermore, in addition to the bottom hole pump  40  and the optional gas lift, the injection line of pressurized gas may include one or more boosters (not shown) to increase the pressure of the pressurized gas upstream of the turbine. This pressure increase allowed by the boosters allows more energy to the turbine and/or more energy after the expansion carried out on the turbine for activating the well by the injection of expanded gas. This pressure increase by the boosters allows ultimately an even greater improvement of the well production.