Abstract
According to the formation and handling situation of hydrate in ultra-deep high-pressure sulfurcontaining gas wells in northwest Sichuan, the formation conditions of natural gas hydrate was studied based on previous studies on hydrate, the molecular dynamics of natural gas hydrate and the multiphase flow law of high-temperature high-pressure high-sulfur-containing gas wellbore were combined, and the pressure prediction model with high-temperature high-pressure sulfur-containing gas wells as the target was built. The chemical and physical control methods of wellbore hydrate plugging were discussed to provide the scientific theoretical basis for the prediction and control of hydrate in high-temperature high-pressure high-sulfurcontaining gas wells.
Highlights
There are many oil and gas-containing reservoirs in the northwest Sichuan, at present, exploration and development targets are mainly the Qixia, Maokou, Changxing and Feixianguan group, gas wells show ultradeep, high-pressure and sulfur-containing characteristics, stratum pressure ranges from 91.13 to 131.09 MPa, stratum temperature ranges from 121.70 to 164.11°C, hydrogen sulfide content range from 0.02 to 88 g/m3, and total depth of four stratums all exceed 5500m, at present, the total depth in the Shuangyushi block is average 7746m, which is the record of the deepest wells of land average total depth of CNPC
The wellbore hydrate blockage was formed during the production process, and after the measures of pumping glycol and wellhead insulation were ineffective, the self-heating unblocking process was adopted to remove the blockage, the operation from start to finish is a total of 5 months, affecting the output 1812×104m3; it is easy to form hydrate and freeze plugging in the production process; wellbore hydrate blockage is formed in the process of oil test, which affects the project progress; after opening the safety valve in the pit and preparing to pump ethylene glycol, hydrate blockage was rapidly formed in the wellbore, affecting the normal production
On the basis of CPA equation of state and vdW-P model, predicting the formation conditions of sour gas hydrates has a good application in sour gas fields, modifying binary interaction parameters or association parameters in polar molecules such as H2S, this is expected to solve the difficult problem of predicting gas hydrate formation conditions in ultra-deep high-pressure sulfur-containing gas wells in northwest Sichuan [4]
Summary
There are many oil and gas-containing reservoirs in the northwest Sichuan, at present, exploration and development targets are mainly the Qixia, Maokou, Changxing and Feixianguan group, gas wells show ultradeep, high-pressure and sulfur-containing characteristics, stratum pressure ranges from 91.13 to 131.09 MPa, stratum temperature ranges from 121.70 to 164.11°C, hydrogen sulfide content range from 0.02 to 88 g/m3, and total depth of four stratums all exceed 5500m, at present, the total depth in the Shuangyushi block is average 7746m, which is the record of the deepest wells of land average total depth of CNPC. The hydrate formation temperature at the wellhead of ultra-deep high-pressure sulfur-containing gas wells in northern Sichuan is as high as about 35°C, which is much higher than that of normal-pressure gas wells without hydrogen sulfide, and it seriously affects safe production. In addition to the existing self-heating unblocking process that needs further optimization; exploration and research on other ultra-deep high-pressure sulfur-containing gas wellbore unblocking processes need to be carried out
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