Abstract: A multi-cylinder pulseless pump mechanism is provided which incorporates a plurality of positive displacement pumps having their respective outlets coupled for sequentially delivering a continuous pulseless supply of fluid to an outlet line. To achieve pulseless fluid flow from the synchronously operating piston pumps and to achieve sensitive operation even under high pressure conditions a differential pressure sensor is provided having a pair of bridge type strain gauge transducers which render finite voltages above zero at all pressure conditions and thus provide transducer output signals that are free from electrical noise typically associated with zero voltage. One of the transducer signals is buffered to drive a recording device to show system pressure level.

Abstract: A precision gas metering apparatus is disclosed and comprises facing duplicate cylinders each having a piston therein, wherein the two cylinders are aligned with one another so that a common non-rotating shaft moves pistons in each. The shaft is driven by a stepping motor having a traveling nut connected to said shaft to impart rotation from the motor which is converted into linear movement of the shaft. With suitable valves and a pressure transducer, gas to be measured is delivered first to one volume and then to the other, the pistons being driven to equalize in flowing gas pressure to atmospheric pressure level, and thereafter summing the total volumetric filling by summing each filling of each chamber, and also summing any partial fillings. A pressure transducer assures that the filled chambers are held to a specified volume.

Abstract: A back pressure regulator system is set forth. In the preferred embodiment, a pressure to be regulated is input to a pressure transducer. The transducer forms a signal indicative of pressure applied through a regulator system which forms an output driving differential signal suitable for a motor. An electric motor is driven thereby and operates a gear box which in turn connects through a slip clutch and a linear motion clutch to advance or retract a needle valve stem. The stem is threadedly engaged with the body. It rotates to advance or retract a needle valve in a valve seat, and a connection is made from the pressure to be regulated through the needle valve to thereby control back presssure on the system.

Abstract: Additional amounts of crude oil are recovered from a subterranean formation by flooding with a translucent emulsion comprising an upper- or middle-phase microemulsion as an external phase and a polymer-containing brine solution as an internal phase. The translucent emulsion tends to coalesce into its component phases under conditions of no shear, but is stabilized by low shears such as those imposed on fluids flowing through a subterranean formation.

Abstract: Pumping apparatus which incorporates connected piston type positive displacement, slip free pumps is disclosed. They provide pumped outputs at a common displacement rate. They run out of phase to one another so that while one is pumping, the other is able to refill. A three way valve under control of a pressure responsive switch delivers pumped fluid to the down stream outlet when a pressure match is achieved. The apparatus finds application as a constant rate continuous fluid injection pump.

Abstract: A water-external microemulsion and a method of recovering crude oil therewith, the water-external microemulsion being one which comprises at least 90% by weight of an aqueous medium, an oil component and a surfactant comprising a C.sub.8-16 orthoxylene sulfonate in an amount greater than the critical micelle concentration to form the microemulsion. The water-external microemulsion allows for effective and efficient crude oil recovery by providing minimum adsorption and low oil-water interfacial tension.