Research On Drilling Fluid, Completion Fluid And Reservoir Protection Technology In HZ25-7Oil Well Block

HZ25-7oilfield reservoirs are low permeability reservoirs, which the per meability is between0.6to20X10-3μm2,porosity11%.The well HZ25-7-2h as a good oil gas show.oil gas test and fracturing operation are provided to im prove the oil production, Compared with the expected production after fracturin g operation,the effect of the operation is very limited and the production decr sase quickly after second section.The result of interpretation software is much better than the actual test results. the formation damage is obvious.In order to minimize the pollution of drilling and completion fluid to oil r eservoir, increase oil production, reduce oil field development costs and improv e the effectiveness of the oilfield comprehensive development, we carried out drilli ng and completion fluids and reservoir protection technology of Huizhou25-7blo ck research.Through the analysis of exploratory well reservoir sensitivity and p erformance evaluation of potential application of water-based and oil-based drill ing fluid, we evaluate the reservoir protection of the selected drilling fluid syst em and get the following results:1) Reservoir sensitivity tests show that the reservoir has no phenomenon of speed-sensitive and acid-sensitive, has a weak sensitivit and medium-weak salt sensitive.2) PEM drilling fluid system, invert emulsion oil-based drilling fluids and oil-based drilling fluid have a good performance in site under the formation temperature and pressure conditions in HZ25-7oil well.3) No matter it is oil-based drilling fluid system, or water-based drilling fluid system, we can significantly increased permeability recovery performance by adding acid-soluble temporay plugging agent with a certain particle size distribution.The permeability recovery performance of oil-based drilling fluid in reservoir with a permeability of10×10-3μm2is relatively stable, and the permeability recovery in reservoir with a permeability of3×10-3μm2is also improved by adding temporay plugging agent.No matter in reservoir with a permeability of10×10-3μm2or reservoir with a permeability of3×10-3μm2, the PEM drilling system has a good performance of reservoir protection by using acid soluble temporay plugging agent.It show a broad prospects of the PEM drilling fluid in low permeability reservoirs.