Portable and transportable instrumentation complexes based on pulsed x-ray generators with more stringent requirements for the spatio-temporal structure of the radiation field are needed for effective fast analysis of the state of the components of main pipelines. Specifically, aside from having small dimensions (maximum linear size ≤0.5 m), the radiation source must provide at distance 0.5 m from the target an exposure dose rate of at least ~0.1 mSv/sec with minimal area of the emitting surface of the target (source which is nearly a point source). These parameters can be attained with x-ray generators based on accelerator tubes operating in a pulsed regime with accelerated-electron current amplitude in the tube I m~ 1 kA, nanosecond pulse duration, and maximum electron energy of several hundreds of keV [1].To improve the sharpness of the x-ray image, the effective area of the emitting surface of the target must be reduced to a minimum. This is achieved by using diode systems with spherical coaxial acceleration geometry and an internal anodetarget with a small radius or in combined systems which incorporate the properties of spherical and coaxial diodes. The most interesting system is a system with an internal conical configuration [2, 3], which makes it possible to form effectively an explosive-emission cathode plasma which propagates toward the anode and is an intense source of electrons. In this case, the intensity of the electric field near the anode can reach ~10 8 V/m. A variant of such a diode system is displayed in Fig. 1. It was used as a basis for creating an accelerating tube where ceramic insulators were used to increase the mechanical and electrical strength. An exterior view of one variant of a part with a fluted insulator is shown in Fig. 2.The accelerator tube operates from a pulsed high-voltage source, which is placed together with it into an airtight pressure-stable vessel filled with an insulating gas under pressure 15-20 Pa. It is based on sulfur hexafluoride (SF 6 ). A well-known scheme with a discharger-peaker for starting the pulsed tube [4], shown in Fig. 3, is used in the source. The storage capacitor C 1 is charged through the resistor R from a dc voltage source U 0 , which is an integral part of the interface of the x-ray radiator (Fig. 4) Periodic-pulse start up of the accelerator tube can be accomplished in a self-generation regime, which corresponds to the scheme shown in Fig. 4, as well as by forced startup with a prescribed frequency. In the latter case, a controllable vacuum or gas-filled apparatus, equipped with a special high-voltage electrode to which a high-voltage pulse that ignites a discharge in vacuum or gas between the working electrodes of the discharger is applied, can be used instead of an uncontrollable gas-filled dual-electrode discharge P 1 .The self-generation regime is obtained as follows. After the storage capacitor C 1 is charged to the breakdown voltage U bd of the discharge P 1 , commutation of the first circuit occurs. The working frequency of the discharger...
The decrease in petroleum output from a well due to degradation of the permeability in the extraction zone of the productive fluid is a frequent negative phenomenon which occurs when a deposit is being developed. This effect is inevitable, since the extraction zone of the productive fluid operates as a filter, retaining and accumulating during well operation all possible impurities in the pores of the formation.One of the most effective methods for cleaning the extraction zone is to expose it to a longitudinal ultrasonic pressure wave. In so doing, nonstationary oscillating microflows appear in the fluid-filled pores in the formation. If the acoustic field is strong enough, these microflows can promote the removal of these impurities from the fluid extraction zone. In this case, the petroleum output from the well should increase [1]. In addition, ultrasonic action on the formation and the space around the well is very likely to cause water to flow into the well from behind the main shaft of the well, resulting in the displacement of the water-petroleum contact and other undesirable and difficult-to-control effects.Thus, there are conditionally three states of the porous medium subjected to acoustic action: 1 -pores are filled with impurities (initial state), 2 -pores are filled with products of hydrocarbon fluid, and 3 -pores are filled with water. These states and the processes resulting in a transition of one state into another must be followed by remote-controlled means through a casing pipe using transparent monitoring methods. Neutron methods are most effective [2]. Examples of such methods are the integral and pulsed neutron-neutron methods with thermal-neutron detection, integral and pulsed neutron γ-logging with detection of radiative-capture γ-rays, and neutron activation of oxygen. These methods can be implemented using large in-well neutron generators based on sealed accelerator tubes with flux exceeding 10 8 sec -1 in a full solid angle [3]. Such generators make monitoring much safer, because a generator in the switched-off state does not create radiation fields and, consequently, serious ecological problems do arise in an accident, which cannot be completely prevented.A block diagram of a neutron monitoring system is presented in Fig. 1. SNM-Type 3 He-filled detectors are used to detect thermal neutrons. The nuclear reaction 3 He(n, p)T occurs in the interior volume of these detectors. γ Rays are detected with a NaI(Tl) or CsI(Na) single crystal scintillation detector with a combined filter for the direct neutron and γ radiation of the in-well generator.The integral neutron-neutron and neutron γ-logging are based on changing the spatial distribution of thermal neutrons and radiative-capture γ rays depending on the moderating, diffusion, and absorbing properties of the medium being studied. They make it posssible to record the change in the count rate of thermal neutrons or γ rays as a result of a transition from state 1 into state 2 or 3, which are characterized by a substantial concentration of hydr...
The examples of experimental studies of oil stratum debit restoring by method of ultrasound influence to stratum are given. The method of control of such unprocessed oil stratum restoring is proposed. It uses well neutron generator with vacuum accelerating tube and neutron reagent method with pumping of neutron absorbing salt solution to stratum. The results of its successful testing are presented.
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