A blockage removal technology for natural gas hydrates in the wellbore of an ultra-high pressure sour gas well

Abstract

In order to safely, efficiently and economically remove the blockages of natural gas hydrate (NGH) in the wellbores of ultra-high pressure gas wells, this paper utilized the heat released from an independently developed autogenetic heat based solid blockage remover through chemical reaction in the wellbore to dissolve NGH and prevent it from forming again. In addition, adjustable heat generation time and heat generation amount was realized by regulating the dosage of the blockage remover. Finally, the chemically autogenetic heat based blockage removal technology was applied to remove the blockages in ultra-high pressure sour gas wells in the Sichuan Basin. And the following research results were obtained. First, when the independently developed chemically autogenetic heat based solid blockage remover is adopted, the peak temperature (34.2–88.5 °C) and time (24.2–884.0 min) of heat generation can be adjusted by its dosage. What's more, there is NGH inhibitor in the reaction product, which can inhibit the regeneration of NGH. Second, as the concentration of the blockage remover increases, the heat transfer speed increases, leading to an increase of NGH dissociation rate around the blockage remover. Third, blockage removal time increases with the increase of wellbore ID. In addition, the increasing rate of the blockage removal time as the wellbore ID increases from 64 mm to 76 mm is lower than that from 76 mm to 102 mm. Fourth, the coincidence rate between the simulation calculation result of heat diffusion and the on-site actual consumption is more than 85%, which indicates that the proposed model for the heat diffusion of chemically autogenetic heat based blockage remover is reliable and can be used to calculate the dosage of blockage remover. Fifth, solid reagent adding device with resistance to sulfur and pressure of 140 MPa is used to add autogenetic heat based solid blockage remover. This blockage remover has been applied in the ultra-high pressure sour gas wells in the Sichuan Basin three well times. Thanks to its application, NGH blockages in these wells are removed successfully and their production is resumed smoothly. In conclusion, this blockage removal technology has such advantages as effective blockage removal, safe and simple on-site operation and low cost, and a promising application prospect.