RU1144448C - Method of exploitation of gas-condensate and oil seams - Google Patents

Description

 The invention relates to the oil and gas industry and can be used to intensify the production of fluids during the operation of gas condensate and oil fields when exposed to reservoirs by elastic vibrations.

 There is a known method of developing oil fields, in which the process of stimulation of reservoir recovery is carried out due to the impact from the cavity of the wells on the bottomhole (borehole) zone of the reservoir by high-frequency ultrasonic vibrations.

 The disadvantage of this method is that the waves transmitted to the formation have a limited radius of action due to the attenuation of these oscillations directly in the near-wellbore zone of the formation, the generation of such oscillations requires significant energy costs. In addition, this method requires the placement of generators of UKZ sources of ultrasonic vibrations in the cavity of the wells, while the production of fluid stops during processing.

 There is also known a method of developing gas condensate and oil fields, including the impact of low-frequency elastic vibrations on the formation rock to enhance fluid recovery. In this method, the oscillations are carried out using an electromagnetic vibrator located at the level of the formation in the well.

 The disadvantage of this method is the locality of the impact, in which the radius of propagation of the oscillations and the thermal influence propagated by these oscillations is extremely limited due to the strong absorption of waves and heat in the near-well zone of the formation. And this leads to the need to place generators in many wells, which, in turn, necessitates periodic treatments, increasing the cost of operating the wells. In practice, this leads to a decrease in the profitability of the field operation process.

 The closest technical solution to the proposed one is a method of developing gas condensate and oil reservoirs, including exposure to elastic vibrations with simultaneous thermal exposure.

 The specified method involves the excitation of elastic vibrations in the developed deposits by passing between the wells of a pulsed electric current of high voltage, and the pulse duration is small. In this case, the thermal effect is carried out in the same way, only the pulse duration is sufficiently long, which leads to the conversion of electric current energy into thermal energy. The specified method also provides for the injection of displacing fluid.

 The main disadvantage of this method is the low impact efficiency in the development of deposits having areas or zones of high reservoir pressure.

 The aim of the invention is to increase the effectiveness of the impact by increasing the mobility of the reservoir fluid.

 This goal is achieved by the fact that in the method of developing gas condensate and oil reservoirs, including the action of elastic vibrations with simultaneous thermal exposure, pre-identified zones of increased pressure in the developed reservoir, and the effect is carried out on the identified zones, and the elastic vibrations excite the infrasonic frequency range.

 In FIG. Figure 1 shows the experimental dependence of the change in oil viscosity on temperature at various pressures and various effects on oil, where curve I is without vibration at P = 10 MPa; curve II - the same, at P = 60 MPa; curve III - after vibration exposure at P = 60 MPa; curve IV - after simultaneous heat and vibration exposure at P = 60 MPa; in FIG. 2 - layout of equipment during processing; in FIG. 3 - dependence of processing efficiency on the type of exposure.

 The method is as follows.

 Generators 2 of infrasound vibrations 3 are placed on the earth’s surface 1 of the field being developed for impacting the productive formation 4 of the field, wells 5 are used to supply hot or displacing fluid through them, and wells 6 are used for producing fluid from the formation 4, and for this, zones of increased formation pressure (which are recorded by known acoustic methods, these zones at each field are known). Such an impact technology leads to a sharp increase in the efficiency of formation recovery and a reduction in energy costs due to the fact that in the zone of increased pressure of the formation, the fluid has significantly less mobility and penetration due to increased viscosity. So, the Ferghana oil and Astrakhan gas fields are shown (Fig. 3) as indicators of increasing the efficiency of field operations: curve V shows the increase in well production when exposed to electromagnetic waves in combination with heating of the borehole zones of the formation; curve VI shows the operating efficiency — increment of well production from the total impact on the reservoir by seismic vibrations directed over the entire area of the reservoir in combination with the injection of hot fluid (oil, water); curve VII shows the increase in the flow rate of the wells during the implementation of the proposed method of field development, when the impact is conducted in the pressure zones and the fluid is fed into the half-wave of the rarefaction wave during this action.

 These and other advantages of the proposed method are disclosed further on the example of a specific implementation of it on Ferghana oils and Astrakhan gas condensate.

 An example of a specific implementation of this method.

 The pressure zone of the formation 4 is affected by directed infrasonic vibrations 3 from the generator 2. The range of vibration frequencies is selected experimentally and is in the range of 1-60 Hz, mainly 6-18 Hz, at which the largest inter-grain bond breaks are observed in the formation rock and an irreversible decrease in fluid viscosity leading to a significant increase in its mobility and penetration. At the same time, a displacement fluid, for example, heated water or oil, is supplied through the wells 5 during the development of an oil field, moreover, this fluid is supplied predominantly in the half-period of the rarefaction wave in order to reduce the energy consumption for its pushing into the formation. For this, the pumps supplying the hot fluid to the wells 5 are equipped with bypass valves connected to a switching relay configured for a half-wave of the wave acting on the formation (in the absence of such control units, the method is carried out with a constant supply of fluid).

 When exposed to zones of increased pressure of the reservoir 4, according to the readings of the instruments, they observe the increase in the flow rate of wells 6, bringing it to the maximum possible for a given field (Fig. 3, curve VII) and operate this zone of increased pressure until it is depleted when the oil production process gas becomes unprofitable, after which other areas of increased pressure in the region are subjected to this effect. The exposure time is chosen depending on the increase in flow rate, but it is more effective to act in periods of 5-15 minutes with breaks between these periods of 20-30 minutes. In this mode, the zones of high pressure do not have time to "rest" from the impact and are in a constant state of artificial excitation, giving the maximum amount of fluid.

 These zones of increased fluid pressure in the "lens" formations are pinched in separate zones of the reservoir and do not flow freely into areas with lower fluid pressure due to the localization of these lenses by impermeable or low permeability rocks, for example, dense moist clays.

 These pinched fluid lenses are detected by preliminary research of the field site by exposure to the studied area by acoustic vibrations, with such exposure, these areas of increased pressure are detected by reflected acoustic signals (by signal propagation time, delay time and reflection), and also by the amplitude and frequency of the reflected signals, which most intensively reflect acoustic signals due to their high density due to local increased fluid pressure.

In this method, having preliminary data on the nature of the field in which maps of the zones of high pressure are built, they influence these identified zones of high pressure, and it is precisely in the zones of high pressure that the heated fluid is pumped, the heating temperature of which is determined depending on the fluid itself . Thus, when pumping an aqueous polyacrylamide solution it is advantageous to maintain a temperature equal to 120-160 ^{° C,} when pumping oil its temperature is kept below the ignition temperature of oil in conventional terrestrial conditions.

 With this effect on the reservoir, the most effective mode is the process in which the fluid is pumped into the half-wave of rarefaction waves, which facilitates the penetration of fluid into the pores and formed cracks from transmitted artificial seismic vibrations (as reflected in Fig. 3, curve VII).

 Thus, the technical advantages of the proposed method for the development of gas condensate and oil fields in comparison with the base object containing the operations of stimulating reservoirs and intensifying their fluid recovery using underground explosions are that when the proposed method is implemented, a significant increase in the efficiency of fluid production is achieved, which is reflected on the graph (Fig. 3, curve VII; and curve V shows the effectiveness of the base object). In addition, when implementing the proposed method, there are no negative effects on field wells, while when implementing the base facility, underground explosions lead to the destruction of wells and the need to restore them, and also have a harmful effect, polluting the environment with explosion products. Moreover, the implementation of the proposed method can be easily controlled and choose the optimal and effective modes, while blasting is of little control.

 Fluid supply during the rarefaction wave period facilitates its most efficient penetration into pores and intergranular discontinuities due to the fact that these pores are freest in the half-wave of the rarefaction wave, and the subsequent half-wave of the compression wave additionally contributes to the forced flow of fluid into the pores of the low-permeability reservoir .

 These technological advantages of the proposed method allow to obtain a significant economic effect due to a significant increase in the level of production. (56) U.S. Patent No. 4,049,053, cl. 166-249, 1977.

 USSR copyright certificate N 832072, cl. E 21 B 43/24, 1963.

 U.S. Patent No. 4084638, cl. 166-248, 1978.

Claims (1)

 METHOD FOR DEVELOPING GAS-CONDENSATE AND OIL LAYERS, including exposure to elastic vibrations with simultaneous heat exposure, characterized in that, in order to increase the impact efficiency by increasing the mobility of the formation fluid, pressure zones in the developed reservoir are preliminarily identified, and the effect is carried out on the identified zones, and elastic vibrations excite the infrasonic frequency range.

Images