RU2244106C1 - Method for intensifying oil extraction - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes electro-hydraulic treatment of bed at resonance frequency and extraction of oil from bed. According to invention bed is excited by resilient pulses at broad frequency range from 0 to 10 kHz. Frequencies are set, at which bed is treated. Resonance frequency is kept by singular, periodical, radially focused electro-hydraulic pulses with generation frequency, divisible by bed resonance frequency. Concurrently in adjacent well bed excitation frequency is controlled by resilient pulses and corrected according to measurements results.

EFFECT: higher efficiency.

2 dwg

Description

The invention relates to geotechnological methods for the extraction of minerals by acting on the formation with physical fields and can be used, in particular, in the production of liquid hydrocarbons.

A known method of wave processing of the formation (RF patent No. 2001254, M.cl. E 21 V 43/25, Bull. No. 37-38, 1993) using a ground vibration source, which involves the use of resonant frequencies for exciting the formation according to the formula:

W.spl. = πV / Kh,

where K is the repeatability coefficient of the transmission of generated seismic waves, K = 1,2,3,4 ...,

V is the velocity of propagation of elastic waves in the reservoir,

H is the thickness of the reservoir.

Having determined the geological and physical characteristics of the productive reservoir, they achieve that the resonant frequency of the vibration source Wp. was equal to the resonant frequency of the reservoir W = Wrespl.pl.

This method requires cumbersome ground equipment, effective only in harsh environments for the transfer of elastic energy. As sources of elastic waves, ground-based seismic sources with a capacity of 70-120 kilojoules (GSK-10 or SV-5-150, etc.) are used. Most of the vibration source is spent on the buildup of the near-surface near zone of the elastic medium. Calculations show that only 1-2% of all radiated energy reaches a productive formation at a depth of 2-2.5 km. The resonant frequency of the excited formation depends on many parameters of the medium, and the calculation proposed by the authors is simplified and requires experimental refinement of the resonant (dominant) frequency for each formation, field.

A known method of intensifying oil production, adopted as a prototype according to the patent of the Russian Federation No. 2055171, M.cl. E 21 B 43/25, 1996, which consists in exposure to the formation by electro-hydraulic pulses in the frequency range 4-10 Hz for 5-15 minutes with a number of cycles of at least 3.

The disadvantage of this method is the limited impact zone - only on the bottomhole formation zone and, accordingly, the insignificant penetration of elastic vibrations into the formation.

The objective of the proposed method is to eliminate these disadvantages, i.e. increasing the depth of penetration of the elastic wave into the formation, due to this an increase in the permeability of the formation and the mobility of the fluid saturating the formation.

The problem is solved in that in a method of intensifying oil production, based on the elastic action of the reservoir by elastic vibrations at the resonant frequency and the selection of oil from the reservoir, the reservoir is excited in a wide frequency range by single, periodic, radially focused pulses with a repetition rate that is a multiple of the resonant frequency of the reservoir, while at the same time in a neighboring well control the frequency of excitation and adjust it according to the measurement results.

The method can be implemented using the equipment depicted in figure 1, and figure 2 shows the frequency spectrum of the resonant (dominant) frequencies for oil and gas reservoirs with different physical parameters.

The apparatus includes a logging elevator 1, a downhole tool 2, lowered into the well 3 on a geophysical cable 4. In the downhole tool 2 there are electric energy storage devices and devices for controlling their charge and discharge, there are electrodes 5 and a wire 6 inserted into the gap between the electrodes 5 using devices 7 automatic wire feed. Downhole equipment 9 for monitoring resonant vibrations in the formation is lowered into the neighboring well 8 using a separate logging winch in the interval of impact on the formation, according to which the pulse repetition rate is adjusted.

The method is as follows. Using ground equipment located on a logging elevator, AC is supplied with current to the downhole tool 2, lowered into the well 3 on the geophysical cable 4. The capacitors of the device 2 are charged with increased and rectified voltage, the charge of which is made between two electrodes 5 by signals from the control device. Electro-hydraulic discharge occurs. The stability of such a discharge in liquids of different mineralization in the well (oil, oil with water, saline water) is ensured by the initiation of an explosion by a wire conducting electric current, introduced into the gap between the electrodes after the next explosion using the automatic wire feeding device 7.

The frequency spectrum of the emitted elastic pulse in the range from 0 to 10 kHz depends on many factors: voltage and charge speed, discharge time, distance between electrodes, discharge resistance, etc., and it can be adjusted by tuning to the required frequency range, among which there are frequencies on which the reservoir resonates. By registering elastic vibrations in the neighboring well 8 by apparatus 9, it is possible to determine with high accuracy at what frequencies the formation resonates and maintain the resonance frequency in the formation by choosing the repetition rate of single, periodic emitting pulses. The design of electrodes of the electro-hydraulic spark gap is chosen in such a way as to create focusing of the elastic wave in the radial direction. Elastic impulses at a resonant frequency penetrate deep into the formation, forming microcracks in the formation, increasing fluid mobility in pores and in oil, first of all. Each subsequent single pulse creates an elastic wave, which, weakly attenuating at the resonant frequency of the formation, spreads over hundreds of meters (up to 1.0-1.5 km).

Knowing the geological and technical conditions of the field being developed, the development mode and parameters of the reservoir, we determine the resonant (dominant) frequencies in the reservoir. They are different for terrigenous and carbonate reservoirs and depend on pore sizes, type of fluid saturating the reservoir, thickness and extent of the reservoir. Calculations and experimental studies show that if the excited elastic pulse has a wide range of emitted frequencies, then high-frequency resonances are observed in the formation in the near zone of the formation, low-frequency oscillations penetrate deep into the formation with the least losses only at the resonant frequency (Fig. 2).

Radiated radially directed elastic impulses penetrate deep into the formation, creating a buildup of fluid in the formation at resonant frequencies. Due to this, the composition of the fluid entering the well is redistributed, the oil-water ratio improves, and the permeability of the formation increases. It should be noted that concentrated water hammer can cause the formation of additional cracks in the formation, which also improves the permeability of the formation. Well experiments showed that the integrity of the cement stone in the annulus is not violated due to the high radial direction of the elastic impact on the productive part of the formation exposed by perforation.

Claims (1)

A method of intensifying oil production, based on the elastic action on the reservoir, which consists in electro-hydraulic action on the reservoir at a resonant frequency and the selection of oil from the reservoir, characterized in that the reservoir is excited by elastic pulses in a wide frequency range from 0 to 10 kHz, the frequencies at which resonate the formation, and maintain the resonance frequency in the formation by single periodic radially focused electro-hydraulic pulses with a repetition rate that is a multiple of the resonance frequency of the formation, at m simultaneously in neighboring downhole control the formation of excitation pulses and the frequency of elastic corrected based on the results of its measurements.

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