RU2459942C2 - Method of wave processing of productive formations of oil deposits with manifold of fracture type - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method of wave processing of productive formations of oil deposits with manifold of fracture type involves determination of resonant characteristic of formation, use of wave generator and formation processing by means of waves with resonant frequency, which are created with generator. Besides, in order to determine resonant characteristic of formation, linear dimensions of pillars are measured, peculiar size of rock pillar is determined and row of resonant frequencies is calculated for wave processing as per the specified mathematical expression. Then, oil formation is processed by performing a series of in-series processings by radiation of waves of mechanical nature of the calculated row of resonant frequencies in frequency decreasing order. Mechanical-nature wave generator located in the well in the area of processed formation zone is used as wave generator.

EFFECT: increasing oil recovery of formations.

2 cl, 1 ex

Description

The invention relates to the oil industry, in particular to wave methods for enhancing oil recovery.

There are many varieties of wave methods for influencing productive oil reservoirs.

The well-known "Method of wave action on a hydrocarbon reservoir", in which it is proposed to treat the reservoir simultaneously with several sources of longitudinal and transverse wave vibrations located on the surface due to wave interference in the formations (patent RU No. 2361070, published on July 10, 2009). In this case, the wave action is focused on the region of the reservoir with fixed and inactive hydrocarbon reserves and realize a synchronized multipoint wave action.

The disadvantage of this method is the need to place sources of wave oscillations on the surface, which contributes to the scattering of elastic waves in the overlying layers and low energy efficiency of the processing.

The well-known "Method of intensifying oil production and resuscitation of idle oil wells by means of electromagnetic resonance effects on the reservoir" (RU patent No. 2379489, published January 20, 2010), in which it is proposed to process deposits by borehole electromagnetic oscillation generators by placing wave generators in neighboring wells. Generators create modulated electromagnetic oscillations of the same frequency, directed from the producing well, and also counter. Omnidirectional electromagnetic oscillations impose on the natural frequency of vibrations of the hydrocarbon fluid, causing resonant vibrations of atoms and molecules of oil.

The disadvantage of this method is the use of electromagnetic waves, which are largely absorbed by the rocks directly near the bottom of the wells, due to which the effect of the superposition of waves from two neighboring wells in the formation is negligible. Another disadvantage is the tuning of the waves to the resonant frequency of the reservoir oil, the determination of which is practically difficult.

Of the known methods closest to the claimed one is the "Method of impact on the reservoir" (patent RU No. 2351755, publ. 10.04.2009), which consists in determining the period of the fundamental harmonic - resonant frequency - the system "well - reservoir" by creating a generator in the borehole liquid waves with a specific frequency and measuring the frequency of oscillations caused. Next, the frequency of the hydroacoustic waves generated by the generator is set equal to the frequency of the fundamental harmonic of the resonant frequency “well - reservoir”.

The disadvantages of the method are the need to conduct tests to determine the frequencies of induced vibrations for each individual well, as well as conducting treatment of the formation with waves of a single frequency, which does not allow affecting blocks of different scales of the formation system.

The technical result of the proposed method is to increase oil recovery from oil fields.

где L_i - i-й характерный размер блока породы, c - скорость распространения механических волн в горной породе пласта, затем обрабатывают нефтяной пласт, проводя серию последовательных обработок путем излучения волн механической природы рассчитанного ряда резонансных частот в порядке убывания частот, при этом в качестве генератора волн используют генератор волн механической природы, располагаемый в скважине в области обрабатываемой зоны пласта.The technical result is achieved by the fact that in the method of wave treatments of productive formations of oil fields with a fractured reservoir type, including determining the resonance characteristics of the formation, using a wave generator, treating the formation by creating a wave generator with a resonant frequency, to determine the resonance characteristics of the formation, measure the linear dimensions of the blocks, determine the characteristic rock block size and calculate a number of resonant frequencies for wave treatments according to the formula

where L _i is the i-th characteristic size of the rock block, c is the propagation velocity of mechanical waves in the rock of the formation, then the oil formation is processed by conducting a series of sequential treatments by emitting waves of a mechanical nature of a calculated series of resonant frequencies in decreasing order of frequency, while as wave generator use a wave generator of mechanical nature, located in the well in the field of the treated zone of the reservoir.

, где L_i - i-ый характерный размер блока породы, a L_max и L_min - максимальные и минимальные линейные размеры отдельных блоков, а в качестве волн механической природы могут быть использованы ультразвуковые, акустические, ударные и гидравлические волны.The characteristic rock block size can be calculated by the formula

, where L _i is the i-th characteristic rock block size, a L _max and L _min are the maximum and minimum linear sizes of individual blocks, and ultrasonic, acoustic, shock and hydraulic waves can be used as waves of a mechanical nature.

As oil fields are developed, a significant amount of information is accumulated on fracturing of productive formations obtained by studying core samples, the preferred direction of filtration of formation fluids, mutual influence of wells, well drilling data, geophysical data, etc. The most complete data on reservoir fracture are accumulated by visual examination of the linear dimensions of the rock blocks of the formation, separated by fractures, during the development of deposits by the mine method, as is the case at the Yaregskoye field of high-viscosity oil (Komi Republic). Using these data, it is possible to determine the characteristic sizes of the blocks of the oil reservoir of various sizes.

A fractured oil reservoir is a system of blocks of various sizes. The most effective wave processing will be when the sizes of the characteristic blocks L coincide with the wavelength of the emitted oscillations λ, since in this case there will be a resonant increase in the amplitude of the oscillations of the rock-collector (M.A.Sadovsky, L.G. Bolkhovitinov, V.F. Pisarenko, Deformation of the geophysical environment and the geophysical process, Moscow: Nauka, 1987). Given the fact that the scales of the individual blocks of the oil reservoir differ significantly, it is necessary to determine the individual characteristic (predominant) sizes of the blocks from micro to macro scale, i.e. from grain sizes of particles and particles separated by microcracks to sizes of large rock formations. Studying the data on the linear sizes of individual blocks, the obtained information can be presented in the form of a histogram of the sizes of blocks of the reservoir, from which local maxima can be distinguished, which will make up a discrete series of characteristic linear sizes of blocks of the reservoir. For each value of a number of linear sizes of blocks L _{i, the} resonant frequency of oscillations v _{i is} calculated from the equation:

where c is the propagation velocity of elastic waves in the rock of the oil reservoir. This equation is obtained from the relationship between the wavelength λ and its frequency, by definition, by replacing the wavelength in the equation with the value of the individual characteristic block size L _i . Thus, we obtain a series of frequencies. It is proposed to carry out wave processing of the oil reservoir through a separate well in several stages, sequentially, by frequency waves, the values of which are equal to the values of the calculated values from the obtained series of values. The total number of treatments in a single well should be taken equal to 4-5. The duration of the treatments depends on the power and type of generator selected. Processing should be carried out in the order of decreasing frequencies, thus they will be covered by an intense wave action amplified due to resonance, in order: rock grains, small blocks, large blocks of the formation, which will allow full involvement of all components of the fractured oil-saturated formation in the oscillatory process, which is favorable affect the mobility of oil, saturating the rocks of the reservoir. It is proposed to conduct formation treatment through wells with calculated frequencies directly one after another until the entire series of frequencies is covered. The frequency of the treatments (repeated) should be determined by the change in the flow rate of the wells, the effect of the treatment should be considered completed when the flow rate of the well decreases to the average value for the last month preceding the treatment. The increase in oil recovery with the proposed method of processing occurs due to the reduction of anomalies in the viscosity of oil, the destruction of the internal thixotropic structure of oil and increase the phase permeability of formation rocks by oil.

It is proposed to define the characteristic sizes of the individual differences L _{i of the} reservoir as the geometric mean of the maximum L _max and minimum L _{min of} its visible linear dimensions (M.A.Sadovsky, L.G. Bolkhovitinov, V.F. Pisarenko. Deformation of the geophysical environment and geophysical process. M .: Nauka, 1987):

This method of determining a number of frequencies for a series of sequential wave treatments can be widely used in the conditions of the Yaregskoye oil field, the only one in Russia developed by a mine method, the use of which made it possible to study quantitatively the crack system and the linear dimensions of individual blocks with high accuracy, mainly visually.

Improving the efficiency of wave treatments of oil reservoirs is achieved by conducting not a single impact, but a series of treatments of the reservoir from an individual well with waves of a discrete series of frequencies, calculated taking into account the block structure of fractured oil reservoirs. To complete the coverage of the reservoir, it is advisable to carry out treatments of several wells located in different parts of the reservoir. Waves can be created by any generator of waves of a mechanical nature - ultrasonic, acoustic, shock and hydraulic. The wave generator should be located in the well, the mouth of which is located on the surface or in a mine working underground (in the mine) in the area of the treated section of the formation, thereby achieving the least energy loss from wave scattering by rocks.

. Мелкие трещины, которые определяются по результатам исследования шлифов кернов, не обнаружены. Трещины, разделяющие породу нефтяного пласта на отдельные блоки, имеют субширотное и субмеридианальное простирание с густотой 10,6 1/м. Величина густоты трещин имеет небольшие вариации, близкие к указанному среднему значению, которое одинаково для трещин обоих направлений простирания. Таким образом, второй характерный размер блоков - 1000/10,6=94,3 мм = L₂. Имеют место более выраженные крупные трещины, которые разделяют блоки на блоки видимых размеров 0,5 на 0,8 м. Отсюда третий характерный размер блоков

. Отдельные крупные тектонические трещины имеют крайне неравномерное распространение и разделяют нефтенасыщенные пласты на отдельности крайне нерегулярной формы. Таким образом, для рассматриваемого объекта выделен ряд из трех значений характерных размеров блоков: 0,6; 94,3; 632 мм, для которых с учетом скорости распространения упругих продольных волн в песчаниках Ярегского месторождения, равной 1800 м/с, полученной применением сейсмических генераторов волн ударного типа, получаем ряд рекомендуемых частот для волновой обработки залежи скважинными генераторами: 3,00·10⁶, 19100, 2850 Гц.Example. The main developed object of the Yarega oil field is the layer III of the Yarega area. Known data on fracturing of slope 102 of oil mine No. 3 (A.V. Petukhov. Theory and methodology for studying the structural and spatial zonality of fractured oil and gas reservoirs. Ukhta, 2002. - 276 pp.). The prevailing grain size of the sandstone of the formation rock, determined from the particle size analysis of the formation rock, is 0.6 mm. The grains have a rolled shape, close to spherical. In this way,

. Small cracks, which are determined by the results of the study of core sections, were not detected. Fractures dividing the rock of the oil reservoir into separate blocks have a sub-latitudinal and submeridian strike with a density of 10.6 1 / m. The crack density has small variations, close to the indicated average value, which is the same for cracks in both directions of strike. Thus, the second characteristic block size is 1000 / 10.6 = 94.3 mm = L ₂ . There are more pronounced large cracks that divide the blocks into blocks of visible sizes of 0.5 by 0.8 m. Hence the third characteristic block size

. Individual large tectonic cracks have extremely uneven distribution and separate oil-saturated formations into separate extremely irregular shapes. Thus, for the object under consideration, a number of three values of the characteristic sizes of the blocks are distinguished: 0.6; 94.3; 632 mm, for which, taking into account the velocity of propagation of elastic longitudinal waves in the sandstones of the Yaregskoye field, equal to 1800 m / s, obtained using seismic shock wave generators, we obtain a number of recommended frequencies for wave processing of the reservoir by borehole generators: 3.00 · 10 ⁶ , 19100 , 2850 Hz.

The use of sequential wave processing obtained by a number of frequencies allows to increase oil recovery in the considered area.

Claims (2)

1. The method of wave treatments of productive formations of oil fields with a fractured type of reservoir, including determining the resonance characteristics of the formation, using a wave generator, processing the formation by creating a wave generator with a resonant frequency, characterized in that the linear dimensions of the blocks are measured to determine the resonant characteristics of the formation, and the characteristic size is determined rock block and calculate a number of resonant frequencies for wave treatments according to the formula

where L _i is the i-th characteristic size of the rock block, c is the propagation velocity of mechanical waves in the rock of the formation, then the oil formation is processed by conducting a series of sequential treatments by emitting waves of a mechanical nature of a calculated series of resonant frequencies in decreasing order of frequency, while as wave generator use a wave generator of mechanical nature, located in the well in the field of the treated zone of the reservoir. 2. The method according to claim 1, characterized in that the characteristic size of the rock blocks is determined by the formula

L _i is the i-th characteristic size of the rock block, and L _max and L _min are the maximum and minimum linear dimensions of the individual rock blocks, and ultrasonic, acoustic, shock and hydraulic waves are used as waves of a mechanical nature.