Abstract: A downhole separator sub for separating drilling mud into a more dense portion and a less dense portion. The apparatus includes a barrel having a central opening therethrough and a cyclone separator cartridge positioned in the central opening. The barrel is attachable to the drill string and the drill bit. The cyclone separator cartridge includes an upper insert, an intermediate cyclone separator housing and a lower insert. An annular flow passage is defined between the cyclone separator housing and an inner surface of the barrel. The upper insert includes an inlet passage providing communication between an upper portion of the barrel central opening and the annular flow passage. The lower insert includes a cyclone inlet providing communication between the annular flow passage and a cyclone chamber in the cyclone separator housing.

Abstract: A fluid agitating apparatus is disposed in a vessel containing a body of fluid to be agitated. The fluid agitating apparatus includes a housing having an inlet at an open lower end thereof, and an outlet at an open upper end thereof, with a flow passage disposed through the housing communicating the inlet and the outlet. The flow passage is preferably circular in cross-section and has a minimum diameter at a throat thereof. The diameter of the flow passage increases continuously from the throat toward both the inlet and the outlet. A vertically upward directed nozzle is located in the flow passage below the throat for inducing flow of fluid from the body of fluid in which the housing is submerged into the inlet and upward through the flow passage. A tangentially directed nozzle is disposed in the flow passage above the throat for inducing a swirling flow in the fluid flowing upward through the flow passage.

Abstract: Apparatus and methods are disclosed for drilling a well. A separator sub includes a cyclone separator which separates a stream of drilling mud into a less dense first portion and more dense second portion. The stream of drilling mud flows downward in an annular stream around the cyclone separator and then flows into a lower end of the cyclone separator. The less dense first portion of the stream of drilling mud is directed from the cyclone separator downward to a drill bit so that the drilling mud adjacent the drill bit has a density less than an initial density of the stream of drilling mud. The more dense second portion of the stream of drilling mud is directed upward from the cyclone separator and is ejected into a well annulus with an upward component of velocity and thereby reduces a hydrostatic drilling mud pressure adjacent the drill bit.

Abstract: Apparatus and methods are disclosed for drilling a well. A separator sub is used to separate a stream of drilling mud into a less dense first portion and more dense second portion. The less dense first portion of the stream of drilling mud is directed downward to a drill bit so that the drilling mud adjacent the drill bit has a density less than an initial density of the stream of drilling mud. The more dense second portion of the stream of drilling mud is ejected into a well annulus with an upward component of velocity and thereby reduces a hydrostatic drilling mud pressure adjacent the drill bit.