Abstract: A blowout preventer (10; 110) adapted to be included in a drill string (11; 111) to isolate a downhole portion of an annulus (14; 114) between the drill string and a borehole wall (12; 112). The blowout preventer has a tubular body (16; 116) and an expandable packer means (22; 122) having an inactive or unset position permitting fluidflow through the annulus (14; 114), and a released, active or set position closing the annulus (14; 114). The tubular body (16; 116) has a through-bore (18; 118) aligned with a bore of the drill string and passageways (30; 130) parallel to the through-bore (18; 118) with fluid inlet ports (32; 132) arranged in a manner to be sealingly covered by the packer means (22; 122) in its unset position, and uncovered upon release of the packer means (22; 122) to permit it to expand into its sealing position closing the annulus (14; 114).

Abstract: A device for drilling holes (1) in the crust of the earth, especially for drilling oil wells, wherein a rotary bit (2) is fitted in a drill string (4), within which drilling fluid is pumped downwardly and, upon return, conveys cuttings to the surface. A piston (5) is mounted on the drill string (4) above the bit (2) and adapted to form a sliding seal against the wall of the hole (1). A seal (8) is mounted above the piston (5) within the hole (1) and adapted to seal against the wall of the hole (1), against the drill string (4), against a return line (6) adapted to conduct drilling fluid with cuttings from the under side of the piston (5) to the top of the seal (8), as well as against a pipe (9) communicating with a pump (10) adapted to pump liquid in between the seal (8) and the piston (5), whereby liquid pressure acting against the upper face of the piston (5) urges the bit (2) against the bottom of the hole (1).

Abstract: A reservoir-engineering method wherein horizontal barriers against flow of undesired reservoir fluids into an oil well are formed by density-controlled injection of a barrier-forming fluid mixture having a large penetration depth into the reservoir. A barrier-forming injection fluid may be placed at the fluid contacts in the reservoir independent on whether it is injected at these, in that it has an intermediate density in relation to the reservoir fluids between which it is desired to be placed. Particularly suitable barrier-forming injection fluids are foam-forming chemicals which in several ways may be converted into mobility reducing barriers in situ.