Abstract: A sacrificial anode sub and method are disclosed which provide a lower voltage at the proximately located bit than at the sacrificial anode disposed on sub to thereby deter bit balling. An electromotive force (emf) dynamo is built into the sacrificial anode sub to provide a direct current voltage source for this purpose. Annular insulator electrically insulates sacrificial anode from tubular body. An electrical connection to drill bit is made through threaded lower connector with bit. Impeller rotates in response to drilling fluid flow to rotate the rotor assembly of dynamo.

Abstract: Coring apparatus and method are disclosed which provide for hydraulic latching of an inner core barrel within an outer core barrel. The apparatus includes a valve face disposed around the inner core barrel and valve seat disposed around the bore of the outer core barrel that close to form a restriction in the drilling fluid flow path. A hydraulic differential force is thereby created which holds the inner barrel in place. Axially oriented bores in a hanger assembly and in stabilizers are disposed along the inner core barrel to provide a flow path for the drilling fluid after the restriction is formed. The bores are calibrated to produce a pre-determined hydraulic force on the inner barrel. A bearing assembly is used to prevent transmission of outer barrel rotation to the inner core barrel. The outer surface of the bearing assembly forms the valve face so as to form the drilling fluid restriction and also provides an axial stop that prevents further axial movement of the inner barrel towards the core head.

Abstract: Various steel, downhole tools and components of a drill string, including, as examples, a PDC drill bit, a rotary rock bit, a cross-over sub, a stabilizer, a reamer, a hole enlarger and a coring bit, are selectively treated to cause certain of their parts to be electro-negative with respect to steel, and certain other parts to either have the same electro-negativity as steel, or to be treated to be electro-positive with respect to steel.

Abstract: A multipurpose fluid flow assisted downhole tool that is adapted for attachment to the lower end of a pipe string to be extended into a well bore and which is capable of cutting sample cores from subsurface earth formations and removing the cores for evaluation. The tool is also capable of removing ferrous metal objects from the bottom of the well bore by both mechanical and magnetic means in conjunction with object movement assistance that is provided by flowing fluid in the vicinity of the bottom of the well bore. The well servicing tool includes an internal mechanism that has the capability of achieving reverse circulation of fluid in the vicinity of the bottom of the well bore which causes fluid flow from the annulus between the tool and the well bore, upwardly into an internal object collection chamber defined by the well tool and then outwardly of the well tool and upwardly through the annulus between the pipe string and the well bore to the surface.