Reservoir protection technology in the Changbei gas field, Ordos basin

In order to estimate the reservoir damage made by drilling fluids in Changbei gas field and choose low-damage completion fluids, the advanced AC-FDS-800-10000 formation damage system was successfully applied to evaluate the damage made by three drilling completion fluid systems under simulated normal drilling conditions and reservoir conditions. The experimental results show that damage ratio of invert oil emulsion drilling fluid to the pay-zone is up to 73.91%, and the damage is not easy to remove due to its filtration into the whole core. Oil based drilling fluid caused nearly 100% damage to the core, but not so deep filtration into wellbore due to low filtration of OBM, the damage can be removed by perforating or fracturing reservoirs after completion. While the average damage ratio of a kind of clay-free low-damage drilling completion fluid is only 11.11%, and it has good temporary plugging effects. Open-hole completion can be adopted after drilling to TD with the fluid, the temporary plugging cake formed on the well bore can be removed by reservoir pressure. And then the well can be put into production directly by gaslift. The completion and production procedure is thus largely simplified.