Most outburst mines in China adopt the measures of pre drainage by drilling along the seam for gas control in the mining area, that is, drilling along the seam from the air roadway of the mining machine to the mining ...Most outburst mines in China adopt the measures of pre drainage by drilling along the seam for gas control in the mining area, that is, drilling along the seam from the air roadway of the mining machine to the mining area. The drainage effect of drilling along the seam is directly related to the gas control effect of the mining area. For many years, we have carried out the measures according to the provisions of the detailed rules for the prevention and control of coal and gas outburst. The sealing length of the bedding hole is consistently kept at 8m, and the depth of the sealing section is kept at about 10m, and the extraction concentration and pure amount have been maintained at a low level, resulting in relatively large gas emission during mining. We break the Convention and calculate the sealing depth of the hole according to the pre drainage equivalent width of the coal roadway. At the same time, the extended version of high-pressure grouting is used for two plugs and one injection seal, so that the hole sealing depth of the borehole is within the equivalent width of the roadway pre drainage gas, and the length of the hole sealing section is longer. At the same time, combined with the whole process casing running technology of bedding drilling, the contact area between the screen pipe and the coal wall is likely to be increased, and good results have been achieved in preventing the impact of hole collapse and other phenomena on the drainage effect. The concentration of single hole drainage and the net amount of main pipe drainage have been greatly improved, and the gas content and gas pressure of coal have decreased significantly.展开更多
Large-scale hydraulic fracturing combined with horizontal well drilling is the key technology in shale gas development.But poor cementing quality is a crucial bottleneck restricting well completion and reservoir stimu...Large-scale hydraulic fracturing combined with horizontal well drilling is the key technology in shale gas development.But poor cementing quality is a crucial bottleneck restricting well completion and reservoir stimulation.In this paper,the shale gas development blocks in the Sichuan Basin were taken as the examples to explore the process and support measures that can be used to keep the mechanical integrity of cement sheath under the effect of hydraulic fracturing.It is indicated that the near-bit three-centralizer drifting BHA used for casing stiffness simulation can decrease the casing running difficulty in the long horizontal section of a shale gas well and increase the time efficiency and safety of casing running;that the flushing efficiency of high-efficiency oil flushing spacer fluid system is higher than 90%from room temperature to 120℃,so it can guarantee the displacement efficiency of cement slurry to the oil-based drilling fluid and the effective cementing of borehole wall;that the performance of anti-channeling ductile cement slurry used in the cementing of long horizontal sections in this area after it is set is confirmed,with the elastic modulus of set cement being lower than 7 GPa and triaxial strength being higher than 40 MPa,so as to alleviate or avoid the damage to cement sheath in the process of fracturing;and that cementing quality is improved by applying the support technologies,e.g.drilling fluid adjustment,pre-stress cementing and ground high-pressure pumping.During 2015e2016,these cementing technologies were applied in 85 wells in the Sichuan Basin.The average well depth of these wells is 4832 m,the average length of horizontal sections is 1560 m and the quality rate of well cementing is 89.58%.During the waiting-on-cement(WOC)time after well cementing,there is no sustained casing pressure.And gas channeling in the annulus during well drilling,completion and test is improved remarkably.It is concluded that this suite of technologies can guarantee and improve the cementing quality of long horizontal sections in shale gas wells and provides good cementing conditions for shale gas development.展开更多
文摘Most outburst mines in China adopt the measures of pre drainage by drilling along the seam for gas control in the mining area, that is, drilling along the seam from the air roadway of the mining machine to the mining area. The drainage effect of drilling along the seam is directly related to the gas control effect of the mining area. For many years, we have carried out the measures according to the provisions of the detailed rules for the prevention and control of coal and gas outburst. The sealing length of the bedding hole is consistently kept at 8m, and the depth of the sealing section is kept at about 10m, and the extraction concentration and pure amount have been maintained at a low level, resulting in relatively large gas emission during mining. We break the Convention and calculate the sealing depth of the hole according to the pre drainage equivalent width of the coal roadway. At the same time, the extended version of high-pressure grouting is used for two plugs and one injection seal, so that the hole sealing depth of the borehole is within the equivalent width of the roadway pre drainage gas, and the length of the hole sealing section is longer. At the same time, combined with the whole process casing running technology of bedding drilling, the contact area between the screen pipe and the coal wall is likely to be increased, and good results have been achieved in preventing the impact of hole collapse and other phenomena on the drainage effect. The concentration of single hole drainage and the net amount of main pipe drainage have been greatly improved, and the gas content and gas pressure of coal have decreased significantly.
基金Project supported by the National Major Science and Technology Project“Development of large-scale oil/gas fields and CBM”0“New technologies for improving the cementing quality and wellbore integrity under the condition of large-scale volume fracturing”(No.2016ZX05022-005).
文摘Large-scale hydraulic fracturing combined with horizontal well drilling is the key technology in shale gas development.But poor cementing quality is a crucial bottleneck restricting well completion and reservoir stimulation.In this paper,the shale gas development blocks in the Sichuan Basin were taken as the examples to explore the process and support measures that can be used to keep the mechanical integrity of cement sheath under the effect of hydraulic fracturing.It is indicated that the near-bit three-centralizer drifting BHA used for casing stiffness simulation can decrease the casing running difficulty in the long horizontal section of a shale gas well and increase the time efficiency and safety of casing running;that the flushing efficiency of high-efficiency oil flushing spacer fluid system is higher than 90%from room temperature to 120℃,so it can guarantee the displacement efficiency of cement slurry to the oil-based drilling fluid and the effective cementing of borehole wall;that the performance of anti-channeling ductile cement slurry used in the cementing of long horizontal sections in this area after it is set is confirmed,with the elastic modulus of set cement being lower than 7 GPa and triaxial strength being higher than 40 MPa,so as to alleviate or avoid the damage to cement sheath in the process of fracturing;and that cementing quality is improved by applying the support technologies,e.g.drilling fluid adjustment,pre-stress cementing and ground high-pressure pumping.During 2015e2016,these cementing technologies were applied in 85 wells in the Sichuan Basin.The average well depth of these wells is 4832 m,the average length of horizontal sections is 1560 m and the quality rate of well cementing is 89.58%.During the waiting-on-cement(WOC)time after well cementing,there is no sustained casing pressure.And gas channeling in the annulus during well drilling,completion and test is improved remarkably.It is concluded that this suite of technologies can guarantee and improve the cementing quality of long horizontal sections in shale gas wells and provides good cementing conditions for shale gas development.
