WELL CLUSTER CONSTRUCTION METHOD Russian patent published in 2012 - IPC E21B7/00 

FIELD: gas and oil production.

SUBSTANCE: construction of well cluster involves location of production and injection well mouths in the form of cluster or battery, drilling in solid rock and reinforcement of vertical, sloping and/or curved wellbores, exposure of production bed in specified points. Construction of the first well of a cluster involves drilling of mine by bit of 630 mm diameter to 10-20 m depth, lowering of casing pipe of 500-540 mm diameter, cementing of annular space, further directional drilling in laminar mode using drilling mud not eroding well walls, with maximum water loss under 6 cm³ in 30 minutes, viscosity of 50 s or higher, specific weight of ca. 1.35 g/cm³, using rotor drilling method with rotor torque up to 100 rpm. Rock samples are taken over each metre of direction tunnelling and analysed for crumbling. Sampling continues until solid hard rock is reached. After directional drilling, casing string is lowered, and annular space is cemented. Well construction is continued to the design mark. Next wells of the cluster or battery are drilled in the same way, but rock sampling and analysis is performed when directional drilling approaches solid hard rock.

EFFECT: safe drilling of well cluster in karst gap conditions in immediate vicinity of the ground surface at drilling start.