Plugging technologies used in the late production period of high-permeability layers with large pore paths

The reservoirs in the Lamadian Block of Daqing Oilfield are mostly high-permeability oil layers, and they successively change into high-permeability layers with large pore paths as injection and production go on. In this type of oil reservoirs, mud loss and reservoir damage caused by drilling fluid filtrate tend to happen in the process of drilling and low-efficiency or inefficient circulation tends to occur in the process of oil production. In order to solve mud loss and reservoir damage caused by drilling fluid, this paper researched and developed the pore locking and film forming based plugging agent which is mainly composed of film forming polymer, degradable particle and natural fiber. Then, laboratory dosage optimization experiment and property compatibility experiment were carried out on the pore locking and film forming based plugging agent. It is shown that its dosage in drilling fluid is 2%-3%. The formula of drilling fluid is determined to be 2% bentonite+0.5% HX-D cationic polymer inhibitor+1% cationic clay stabilizer NW-1+1.5% borehole stabilizer FRJ-II+0.5% HPAN+1% modified bitumen+0.2% potassium hydrate+2%-3% pore locking and film forming based plugging agent. The pore locking and film forming based plugging and mud loss prevention technology used in the process of drilling is formed. Its field application increases the success rate of mud loss prevention by 9.3%, decreases the average thickness of drilling fluid invaded belt from 29 mm to 5 mm and protects the reservoirs effectively. In order to solve the low-efficiency or inefficient circulation in the process of oil production, a kind of water plugging and profile control agent with oily sludge as the main composition was researched and developed. Strengthening time and final strength experiment was conducted on the plugging materials for water plugging and profile control. And it is accordingly determined that the ratio of oily sludge to cementing agent in the suspended liquid of water plugging and profile control agent is 20∶1 and the mass fraction of cementing agent is 5%. In addition, the technological scheme of field water plugging and profile control and its application highlights and considerations were designed. Among four field test wells, the maximum decline amplitude of water cut is 7.0% and the cumulative oil increment is 837 t. In conclusion, this plugging technology effectively solves above-mentioned problems which occur in the drilling and production stage of high-permeability layers with large pore paths in the late production period and provides the technical support for the smooth drilling and production of high-permeability layers with large pore paths in the late period.