The present invention comprises an improved method and apparatus for taking core samples, wherein a core drilling assembly driven by a downhole fluid motor is retrievably housed within a drilling tool of larger diameter, and wherein a plurality of cores may be cut and retrieved to the surface by withdrawal of the core drilling assembly by including an extender in the core drilling assembly each time it is brought to the surface and returned to the drilling tool, and sequentially cutting another core without postdrilling the previously cored formation section. The extenders may be included either above or below the motor used to drive the core drilling assembly, and are preferably of tubular configuration with screw-threaded connectors at their ends for rapid insertion in and removal from the core drilling assembly.
A tool for removing a drill core is formed of a tubular tool member (1) having an axially extending receptacle region (A) and an axially extending gripping region (B), wherein the receptacle region (A) extends partially around half of the circular annular circumference. In a first end of the receptacle region (A) spaced from the gripping region (B) two mutually opposed swivel arms (4) are arranged. The swivel arms (4) project into the inside diameter of the tool member (1) and extend in the direction of the gripping region (G) and are elastic in the radial direction. These swivel arms (4) serve in axially securing a drill core received in the receptacle region (A) of the tool member (1).
The present invention comprises a novel method and apparatus for sinking drill holes in underground rock formations while generating drill cores as rock samples. More particularly, the present invention discloses a method and apparatus which allows for an expanded analysis of ground formations over a larger area through the extraction of drill cores as rock samples. The method and apparatus herein disclosed allows one to drill a number of core shaft sections from the base of a main shaft section in various directions in order to obtain a number of sample cores.
The invention relates to a downhole rotary coring device placeable in a drill string and comprising a head section, a motor, and a core barrel having an outer motor comprising a rotor connected to the outer barrel and a stator to the head section, whereby the rotor and the stator are movable with respect to each other in the longitudinal direction of the drill string.
A drilling unit containing a combined pilot bit and reamer. The drilling unit includes a housing containing a mud motor and a pilot bit extending from its distal end. A reamer is mounted to the housing. The mud motor turns the pilot bit while the reamer is turned either by the mud motor or as the drill string is rotated from the surface. The well bore is drilled and reamed in one pass.By positioning the reamer between the pilot bit and the mud motor, the mud motor must only pass through the larger reamer bore rather than the smaller pilot hole. This will allow larger mud motors to be used than would otherwise be possible.In one embodiment, the pilot bit is offset relative to the center of the end of the drill housing, providing increased tangential speed at the point of impact between the pilot bit and formation.
A core sample retaining sleeve is provided for preventing loss of a cut core sample from the distal end of a coring bit, particularly during retraction of the coring bit to within the coring tool. Preferably, the core sample retaining sleeve is disposed concentrically within the coring bit to fit around the received core sample. The core sample retaining sleeve has one or more retaining fingers formed on the distal end of the coring bit. The retaining fingers are selectively closeable, preferably by urging the one or more retaining fingers against one or more guide members. A guide member is preferably provided as a stationary ridge on the inner, distal surface of the coring bit. The core sample is contained and protected within the closed retaining sleeve.
