[0022] 2) Before the natural gas comes out from the
wellhead and enters the buried gathering pipeline, if the natural gas is not heated, throttled and pressure-reduced at the wellsite, the natural gas will not stop after entering the gathering pipeline and fittings on the wellsite from the
wellhead. The temperature of the natural gas continues to drop due to heat dissipation outward, and the temperature inside the above-ground gathering pipelines and pipe fittings may have been lower than the critical temperature of natural gas
hydrate formation, resulting in the formation of hydrates that block the above-ground gathering and transportation pipelines and pipe fittings, resulting in the failure of normal production of gas wells
[0027] 3) When the natural gas leaves the surface pipeline at the well site, enters the buried gathering and transportation pipeline, and enters the
heating furnace of the gas gathering
station, if the natural gas is not heated, throttled and lowered, the natural gas will It will continue to dissipate heat to the ground through underground gathering and transportation pipelines and pipe fittings, and the temperature of natural gas will continue to drop, which may make the temperature of natural gas in the gathering and transportation pipeline lower than the critical temperature of
hydrate formation, thereby forming hydrates to block the gathering and transportation pipeline, resulting in the failure of normal production of gas wells
[0033] According to the calculations of the known knowledge in the field, it can be known that the temperature of the natural gas gathered and transported by the gas field gathering pipeline in winter is lower than the critical temperature of hydrate formation before entering the gas gathering
station, and the temperature of some gathering pipelines entering the station is already lower than the
freezing point of water. If
methanol is not added through the
wellbore or wellsite gathering and transportation pipeline, the gathering and transportation pipelines of all gas wells from the
wellhead to the gas gathering station will have the problem of hydrate blockage, and some gathering and transportation pipelines will also have the problem of freezing and freezing
[0034] 4) If the natural gas
coming out of the wellhead is firstly heated, throttled and depressurized at the well site, and then transported to the gas gathering station through the gathering and transportation pipeline, it is not only necessary to install a special heating furnace or other heating equipment at the well site, but also consume a large amount of natural gas or other energy sources, and it is often necessary to insulate the above-ground and underground gathering and transportation systems before entering the gas-gathering station, resulting in a substantial increase in natural gas production costs, fixed investment, and management
workloadHeating requires a large amount of natural gas
[0063] 7) Although the surface throttling tubing method can be combined with the existing wellhead surface insulation method, since the existing wellhead surface insulation method cannot increase or increase the temperature of the natural gas that has reached the wellhead, the existing wellhead surface insulation method is used to protect the wellhead. Insulation of ground gathering and transportation pipelines at well sites, buried gathering and transportation pipelines, gas gathering station pipelines, etc., although it can slow down the heat dissipation and
temperature drop of natural gas at the wellhead and gathering and transportation pipelines, it cannot effectively solve the The natural gas hydrate or ice blockage problem cannot solve the problem of long-term low-temperature operation of gathering and transportation pipeline fittings that inevitably exist when natural gas is not heated and throttled, and cannot solve the problem of
heating energy consumption of natural gas before throttling and depressurization
However, there are many serious defects in the application of this process: first, because the block is located in a desert, it is difficult to patrol wells, and it is difficult to find and solve the problem of heating furnace
flameout in time, which makes it difficult for the gas well to produce normally; Although the
gas pipeline has heat tracing and insulation, a large amount of
liquid water will condense and freeze to block the
gas pipeline when the temperature is lower than -20°C, which will cause the
gas heating furnace to go out; The
wellbore part is not insulated, and the problem of hydrate blockage is still common when the temperature is lower than -20°C, which leads to the failure of normal production of the gas well, and further causes the operation failure of the heating furnace. Fourth, the heating furnace is adjacent to the gas well. When the gas well, When the
gas pipeline is accidentally vented or leaked for some reason, there will be a serious safety
hazard of coexistence of gas and fire; fifth, the water produced by the gas well contains acid gases such as
carbon dioxide,
hydrogen sulfide, and
calcium and
magnesium ions, which seriously corrode the high-pressure coil in the heating furnace , will lead to serious
fouling of high-pressure coils, which can easily lead to major safety accidents; sixth, the
gas consumption of heating furnaces is huge; seventh, the cost of gathering pipelines, equipment insulation and fixed investment costs of heating furnaces is huge, resulting in a substantial increase in natural gas production costs; eight It is due to the increased operation of heating furnaces at the well site, resulting in a sharp increase in management
workload[0083] 2) When using the winter production mode, in order to keep the temperature of the natural gas rising to the wellhead and entering the surface gathering pipeline not lower than the critical formation temperature of hydrates, the high-pressure natural gas must be throttled down to a very low pressure in the wellbore tubing first , and then use a compressor on the ground to increase the pressure of natural gas to the pressure required for the gas gathering station to be exported, which will lead to a substantial increase in natural gas production costs and
energy consumption; and the
gas consumption is huge
[0095] 3) When the winter production mode is adopted, if the gas
production rate of the natural gas well is very low, and the temperature of the natural gas rising to the wellhead after throttling downhole is also very low, hydrates will still be formed to block the wellbore, wellhead, gathering and transportation pipelines and pipe fittings, thereby severe
impact on natural gas production
[0104] 4) When the summer production mode is adopted, although the compressor is not running, it still requires high maintenance and management costs, resulting in an increase in natural gas production costs
[0114] Therefore, if the well does not use
methanol as a hydrate suppression measure, it will not be able to produce normally
[0115] 6) Similarly, when the summer production mode is adopted, since the heat dissipation and
temperature drop of the natural gas in the buried gathering pipeline have nothing to do with throttling and
pressure reduction, the natural gas that has been throttled and depressurized in the downhole oil pipe enters the buried gathering pipeline , there is also the problem of
temperature drop[0116] 7) Although using the existing heat preservation method to insulate the wellhead and gathering pipeline fittings can effectively prevent the natural gas from
cooling down at the wellhead and gathering pipeline, but it will greatly increase the fixed investment of the gathering pipeline
[0133] 2) This method also requires throttling and depressurization on the ground, and the natural gas must be heated before throttling and depressurization, so there are similar defects to the "ground throttling oil pipe method"
[0135] 1) This method is a theoretically feasible method, and there is no precedent for the practical application of this method in China
[0136] 2) Since it is much more difficult to set up a special throttling device (such as a downhole
nozzle) in the casing or in the annular space of the oil casing than it is to set up in the tubing, and it is used in the casing or in the annular space of the oil casing ( Such as the downhole
nozzle) is much more difficult to manufacture than the special throttling device (such as the downhole
nozzle) used in the tubing. At present, there is no special throttling device (such as the downhole nozzle) that can be used in the annular space of the casing or the oil casing.
[0137] 3), this method also throttles and reduces pressure downhole, so there is a defect similar to the downhole
throttle tubing method
The
disadvantage of this method is that there are similar defects to the "surface oil pipeline method"
[0140] 1) There are defects similar to the "downhole choke tubing method"
[0141] 2) Since it is much more difficult to install special throttling devices (such as downhole nozzles) in coiled tubing than in tubing, and the manufacturing difficulty of special throttling devices (such as downhole nozzles) used in coiled tubing is much higher than that of tubing The special throttling device (such as downhole nozzle) used in the country has not yet produced a special throttling device (such as downhole nozzle) that can be used for coiled tubing.
However, the method disclosed in this invention does not involve the minimum
operating temperature of gathering pipeline fittings, and cannot solve the problem of long-term low-temperature operation of gathering pipeline fittings that inevitably exists when natural gas is not heated and throttled down, and cannot solve the heating consumption of natural gas before throttling and depressurization. performance problems, did not specify how to solve such problems, and did not provide specific technical solutions to solve such problems
[0143] In a word, the above natural gas production methods all have different defects
Login to View More