Cleanup of Filter Cake Formed by Drilling and Completion Fluids: Removal of internal and external filter cake formed on rock formations during well production

The flow initiation pressure (FIP) is used as an estimate of the differential pressure (between the reservoir and the well) required to initiate production of oil or gas. The standard practice to measure FIP uses a constant flowback rate. This method is shown to be inadequate to measure the FIP. An improved flowback method, which uses a series of constant differential pressures, is used instead to measure the FIP. This method closely represents the constant drawdown between the reservoir and the wellbore. In addition the permeability during flowback is measured at increasing differential pressures. Two types of drilling fluids (sized calcium carbonate and bentonite) are used for the filtration experiments on porous media ranging in permeability from 4 to 1500 md. Both single-phase and two-phase experiments are conducted in lab- simulated open-hole and perforated completions. Small values are found for the FIP in all the experiments (considerably smaller than those measured using the constant flowback method). A Bingham fluid in a network of pores is used to model the cleanup of the internal filter cake during flowback.

Has (13) 505mm diameter horizontal filter elements with (2) 505mm diameter horizontal scavenge filter elements on 30mm spacing. Has 2.5sqmt filtration area and 70 litre cake volume. Vertical tank 600mm diameter with 220 litre volume. Has clamped dished bottom and welded dished top heads. Internal full vacuum/6 bar design pressure at -20/+180degC. External 304 stainless steel jacket 20 litre capacity rated full vacuum/6 bar design pressure at -20/+180degC. Bottom direct driven by 5.5kW 41v 3/50 1,440rpm motor via Jahnel-Kestermann type VW 150-2 gearbox rated 1,500rpm input and 300rpm output. Mounted on (3) stainless steel legs.

The aquarium survived the move rather well. Although I only had wet gravel, water in the external filter and 2G to seed the new tank water, everything recovered and my water changes are down to once every 10 days again after only 6 weeks.