Abstract: Samples are collected from a first wellbore and a second wellbore. Genetic material is extracted from the samples and analyzed to determine microorganisms present in subsurface geological features through which the first wellbore and the second wellbore pass. Movement of microorganisms originating in subsurface geological features at the location of the first wellbore to subsurface geological features at the location of the second wellbore can indicate movement of a carbon-based gas between the first wellbore and the second wellbore.

Abstract: A method of determining whether particular data is included in a data store. The particular data comprises a plurality of first data values and the data store comprises a plurality of second data values. The method comprises obtaining identification data associated with the particular data. The identification comprises a subset of said first data values. A portion of the data store is retrieved and it is determined whether at least a predetermined number of data values of the identification data have a predetermined relationship with corresponding second data values of the retrieved portion of the data store.

Abstract: A method of determining whether particular data is included in a data store. The particular data comprises a plurality of first data values and the data store comprises a plurality of second data values. The method comprises obtaining identification data associated with the particular data. The identification comprises a subset of said first data values. A portion of the data store is retrieved and it is determined whether at least a predetermined number of data values of the identification data have a predetermined relationship with corresponding second data values of the retrieved portion of the data store.

Abstract: A method suitable for removing settled sludge from the bottom of a storage tank uses a machine (1) including a central body (15) rotatable about which is a casing (2, 3) provided with two substantially diametric nozzles (4, 5) arranged so that liquid emerging therefrom sweeps substantially only in one plane, a turbine (12) rotating the casing about the central body (15) and half cylinder (18) ensuring that when the casing (2, 3) is continuously rotated, alternately one nozzle is closed for substantially 180.degree. rotation while the other nozzle is open. Such machines may be suspended above the floor of the tank adjacent to a wall thereof. Liquid is emitted from the nozzles in a sweep substantially parallel to the bottom plane of the storage tank, thereby resuspending the sludge which thereafter is withdrawn as a suspension.

Abstract: A machine (1) suitable for removing sludge from the bottom of a storage tank which comprises a central body (15) rotatable about which is a casing (2, 3) provided with two substantially diametric nozzles (4, 5) arranged so that liquid emerging therefrom sweeps substantially only in one plane, a turbine (12) rotating the casing about the central body (15) and means (18) ensuring that when the casing (2, 3) is continuously rotated, alternately one nozzle is closed for substantially 180.degree. rotation while the other nozzle is open. Such machines may be suspended above the floor of the tank adjacent to a wall thereof.

Abstract: A seal for an opening through which an object (e.g. hose pipe) extends which comprises a stack of flexible sheets (1, 2, 3 and 4) one on top of each other, each of at least two adjoining sheets (1, 2) having an aperture therein of dimensions smaller than those of the cross-section of that part of the object contacting the seal and a series of slits radiating from said aperture towards the perimeter of the sheet and each of at least two other adjoining sheets (3, 4) having a series of slits radiating towards the perimeter of the sheet from the center of the sheet, the series of slits in at least two adjacent sheets being offset with respect to each other.