DRILLING-IN METHOD Russian patent published in 2009 - IPC E21B43/27 C09K8/514 

FIELD: oil and gas industry.

SUBSTANCE: invention is applicable to the oil producing industry and be of use for well completion. The drilling-in method includes penetrating a well using polymer mud, building an acid-decomposable protective screen in the reservoir bottomhole zone (RBHZ) by injecting the said mud, running casing, cementing casing annulus, perforating the RBHZ through the casing under a bed of the said mud, and destructing the said screen through acid treatment. During penetration it uses polymer solution at a density of 1040 to 1080 kg/m³ composed of, wt %: sodium carbonate 3-5, carboxymethyl cellulose (CMC) 3.5-5, polyacryl amide 2-3, marble powder 48-55, and water as balance for Early and Late Carboniferous formations; and polymer solution at a density of 1140 to 1300 kg/m³ composed of, wt %: sodium carbonate 3-5, CMC 4-5, xanthan gum 2-3, marble powder 60-80, and water as balance for Devonian terrigenous formations with high water salinity. During building it uses a mud-pulse system including pressurising, holding pressure for 5 to 10 minutes, and depressurising in the bottomhole zone, repeating this 10 to 15 times.

EFFECT: reduced negative effect drilling muds have on productive reservoirs during penetration, retained drilling mud parameters at various reservoir compositions, and a simplified process for artificial clogging of a bottomhole zone within a production interval.

4 tbl, 1 ex