The natural gases in the Upper Paleozoic strata of the Ordos basin are characterized by relatively heavy C isotope of gaseous alkanes with δ^13C1 and δ^13C2 values ranging mainly from -35‰ to -30‰ and -27‰ to -22...The natural gases in the Upper Paleozoic strata of the Ordos basin are characterized by relatively heavy C isotope of gaseous alkanes with δ^13C1 and δ^13C2 values ranging mainly from -35‰ to -30‰ and -27‰ to -22‰, respectively, high δ^13C excursions （round 10） between ethane and methane and predominant methane in hydrocarbon gases with most C1/（C1-C5） ratios in excess of 0.95, suggesting an origin of coal-derived gas. The gases exhibit different carbon isotopic profiles for C1-C4 alkanes with those of the natural gases found in the Lower Paleozoic of this basin, and believed to be originated from Carboniferous-Permian coal measures. The occurrence of regionally pervasive gas accumulation is distinct in the gently southward-dipping Shanbei slope of the central basin. It is noted that molecular and isotopic composition changes of the gases in various gas reservoirs are associated with the thermal maturities of gas source rocks. The abundances and j13C values of methane generally decline northwards and from the basin center to its margins, and the effects of hydrocarbon migration on compositional modification seem insignificant. However, C isotopes of autogenetic calcites in the vertical and lateral section of reservoirs show a regular variation, and are as a whole depleted upwards and towards basin margins. Combination with gas maturity gradient, the analysis could be considered to be a useful tool for gas migration.展开更多
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 a...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(34.2e88.5℃)and time(24.2e884.0 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.展开更多
基金supported by the Research Foundation for the Doctoral Program of Higher Education of China (No.20050335095).
文摘The natural gases in the Upper Paleozoic strata of the Ordos basin are characterized by relatively heavy C isotope of gaseous alkanes with δ^13C1 and δ^13C2 values ranging mainly from -35‰ to -30‰ and -27‰ to -22‰, respectively, high δ^13C excursions （round 10） between ethane and methane and predominant methane in hydrocarbon gases with most C1/（C1-C5） ratios in excess of 0.95, suggesting an origin of coal-derived gas. The gases exhibit different carbon isotopic profiles for C1-C4 alkanes with those of the natural gases found in the Lower Paleozoic of this basin, and believed to be originated from Carboniferous-Permian coal measures. The occurrence of regionally pervasive gas accumulation is distinct in the gently southward-dipping Shanbei slope of the central basin. It is noted that molecular and isotopic composition changes of the gases in various gas reservoirs are associated with the thermal maturities of gas source rocks. The abundances and j13C values of methane generally decline northwards and from the basin center to its margins, and the effects of hydrocarbon migration on compositional modification seem insignificant. However, C isotopes of autogenetic calcites in the vertical and lateral section of reservoirs show a regular variation, and are as a whole depleted upwards and towards basin margins. Combination with gas maturity gradient, the analysis could be considered to be a useful tool for gas migration.
基金Project supported by the Scientific Research and Technology Development Project of PetroChina Southwest Oil and Gas Field Company“Research on Hydrate plugging removal Technology for Ultra-high pressure Gas Wells”(No.20180303-03).
文摘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(34.2e88.5℃)and time(24.2e884.0 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.
