EP2644822B1

EP2644822B1 - Method for electromagnetic stimulation of downhole area during hydrocarbon production

Info

Publication number: EP2644822B1
Application number: EP13003802.9A
Authority: EP
Inventors: Robert Ibragimovich Alimbekov; Sofia Robertovna Alimbekova; Valeriy Georgievich Akshentsev; Vladimir Anatolievich Dokichev; Shakirjanovich Sharipov Salikhjan; Sergeevich Shulakov Aleksey
Original assignee: OBSCHESTVO S OGRANICHENNOY OTVETSTVENNOSTYU "INNOVATSIONNO-PRIOZVODSTVENNIY TSENTR "PILOT"; OBSCHESTVO S OGRANICHENNOY OTVETSTVENNOSTYU INNOVATSIONNO PRIOZVODSTVENNIY TS PILOT
Current assignee: OBSCHESTVO S OGRANICHENNOY OTVETSTVENNOSTYU "INNOVATSIONNO-PRIOZVODSTVENNIY TSENTR "PILOT"; OBSCHESTVO S OGRANICHENNOY OTVETSTVENNOSTYU INNOVATSIONNO PRIOZVODSTVENNIY TS PILOT
Priority date: 2012-08-01
Filing date: 2013-07-30
Publication date: 2016-04-06
Anticipated expiration: 2033-07-30
Also published as: RU2012133097A; WO2014021736A1; FI20135802L; RU2529689C2; EP2644822A3; EP2644822A2

Description

Technical Field

The present invention relates to the oil industry and can be used to increase the volume of pumped-out fluid, oil recovery efficiency and oil production rate, to improve oil quality and rheological (kinetic) properties, as well as to reduce natural salt (calcium, magnesium, sodium and potassium), hydrated and hydrated hydrocarbonaceous deposits harmfull to downhole ECPP operations on downhole area elements (DAE), including the electric centrifugal pumping plant (ECPP), flow column and casing pipe.

Background

Various methods for stimulation of the downhole area and the productive formation which use mechanical, thermal, physical, chemical and electromagnetic techniques and combinations thereof in order to increase hydrocarbon production efficiency are known.
In the case of mechanical stimulation of formations, permeability is increased due to the appearance of new channels and fractures connecting the formations with the bottom hole zone. Mechanical treatment techniques (hydraulic fracturing of the formation, shot-firing operations) are applied to dense rock formations.
Thermal stimulation is used to remove paraffin and resins settled on pore channel walls, and for reinforcing chemical bottom hole zone treatment techniques.
Physical techniques are based on stimulation using vibration, ultrasound, etc. They are primarily used to remove residual water and solid fine particles from the bottom hole zone in order to increase oil rock permeability.
Mechanical, thermal and physical techniques are known to be, in some cases, rather effective, although the use of these techniques involves considerable financial expense and power consumption.
The use of chemical productive formation stimulation techniques is based on interaction reactions between injected chemical agents, primarily various acids, and certain rocks which dissolve to expand pore channels and increase the permeability of formations. The use of chemical agents is effective in some cases but expensive. It can also be environmentally hazardous.
Electromagnetic stimulation techniques enable a significant reduction in power consumption along with high efficiency. An important advantage of such techniques is that the stimulation is applied simultaneously with the main production process and does not hinder it.
A significant factor affecting production efficiency is protection from unwanted hard deposits for the equipment and downhole area. The build-up of unwanted hard deposits in oil and gas wells and production equipment is an acute problem in the oil industry. Salt, paraffin, and wax deposits, as well as asphaltene deposits, create major problems for the oil industry worldwide. The formation of deposits often causes falls in production and increased operating expenses in hydrocarbon production.
The typical process resulting in the formation of deposits during hydrocarbon production is the depositing of low-solubility salts from mineralized water in the oil field. Some oil field water contains a sufficient quantity of sulfated ions with barium, calcium and/or strontium ions to enable the formation of barium sulfate (BaS04) and/or strontium sulfate (SrS04) in the form of scale. Deposits are generally formed from such compound classes, which include: calcium carbonate (CaC03), calcium sulfate (CaS04), barium sulfate (BaS04), barium sulfide (BaS), barium tiosulfate (BaS203), strontium sulfate (SrS04), sodium carbonate (Na2C03), sodium sulfate (Na 2SO4), sodium sulfide (Na2S), potassium carbonate (K2C03), potassium sulfate (K2 S04), magnesium sulfate (MgS04), magnesium chloride (MgCl2), sodium chloride (NaCl), zinc sulfide (ZnS), zinc sulfite (ZnS03), zinc sulfate (ZnS04), lead sulphite (PbS), lead sulfite (PbS03), lead sulfate (PbS04), etc. as well as combinations of the above listed.
Chemical treatment methods to remove unwanted deposits such as salts, paraffin, asphaltenes and hydrates, include acid treatment or treatment using various other chemicals in order to remove unwanted deposits. The type of chemical treatment process often depends on the type of precipitate or deposit. Chemicals such as polyelectrolytes, phosphonates, poly-phosphino carboxylic acids, organophosphonic acids (such as diethylentriamine penta methyl phosphonic acid) and polymers such as polyacrylate, polyvinyl sulfonate, sulfonated polyacrylates, phosphomethylated polyamines, etc., are often used to reduce or prevent the build-up of unwanted hydrocarbonaceous deposits, such as salt crystals, on the inner surfaces of the production string. Typically, such chemicals are effective only for specific types of deposits and limited to such use. Despite certain advantages, chemical treatment is usually expensive, in many cases harmful for the environment and often rather sensitive and effective only with a specific type of crude oil or specific types of unwanted deposits. Chemical treatments often require special equipment for injecting chemicals into the deepest sections of the well bore.
Methods for electrophysical and electromagnetic stimulation of well production are currently becoming relevant. This stimulation is based on the following factors. When minerals such as calcium carbonate, acid salt of carbonic acid, magnesium carbonate and magnesium bicarbonate, are dissolved in water, positive and negative ions can be observed. When the maximum volume of the material, which can be dissolved for the specified temperature and pressure values, is obtained, the solution should be saturated and in case of modification of the conditions at which saturation concentration of the substance has increased, the solution becomes supersaturated. If the solution contains the required seed crystals, the dissolved substances are crystallized out of the solution and can result in the deposit of sediment in the downhole area.
Seed crystals are formed by clustering positive and negative ions of the material. Due to such distribution of charges, ions which include more than one atom can be considered as dipoles, and when affected by an electric field, such ions become oriented towards this field. This process significantly increases the possibility of collisions between opposite-charged particles as they will move in opposite directions to each other (particularly, in case of alternating electric field), and also increases the growth of clusters of opposite-charged ions of the dissolved material.
Additionally, the electric field reduces the attracting forces which cause attraction of water molecules to ions with the result that the charged particles aggregate to form a seed crystal. These seed crystals have a surface charge that attracts a large number of ions and clusters thereof (which can be obtained in the supersaturated solution), and the seed crystals grow quickly and trigger the growth of other crystals (i.e. sedimentation of the dissolved material) if the solution is not supersaturated. If the pressure is reduced (many substances forming the precipitable material are characterized by decreasing water solubility with decreasing pressure), the crystals continue growing until the volume of the dissolved material is reduced again.
Homogeneous seed crystals grow in a solution in this manner, the crystals can also be formed on any foreign substance or flat surface with jagged steps. Electrical charges will be concentrated on such jagged edges, which will attract charged particles to initiate the process of crystallization. If there are no available homogeneous seed crystals in this part of the solution, the dissolved material will be crystallized, in a similar way, on the heterogeneous seed crystals which should similarly be present on DAE. This results in increase of sediment on their surfaces.
Homogeneous seed crystals initiate the process of crystallization at a higher pressure than crystallization on heterogeneous seed crystals on the surface. As a result, all material susceptible to precipitation from the solution should be deposited in this way prior to the process of heterogeneous depositing on the surface.
Asphaltene and paraffin wax deposits made from the oil content of a water-and-oil mixture are reduced similarly on DAE surfaces. Both asphaltenes and paraffin waxes can use seed crystals, as it is described above, as a crystal nucleus on which suspended particles settle (the latter visually resemble granules) up to the solidification point.
There is a known method of electromagnetic stimulation of oil field fluid (patent No. RU 2208141 , IPC E21B43/24 dated July 10, 2003) used for increasing the extraction ratio of oil or other vaporable fluids from oil springs on the ground or in the sea. According to this method, an electromagnetic wave radiator is positioned in the well, and a high-frequency electric field electrode is placed with it or separately. Oil formations are initially stimulated by super-high frequency electromagnetic waves, then 15 to 30 kHz waves, and, finally, 0.01 to 15 Hz waves, until the formation is partially heated. The oil formation is then stimulated by a high-frequency electric field which is brought into phase with the electromagnetic field and the natural electric field, providing thereby mutual induction of the electromagnetic field and the electric field, resonance and modification of the physical and mechanical properties of the oil formation. Water evaporation caused by heating produces additional vapor pressure on the formation.
However, this method requires considerable power consumption and sophisticated designs for the equipment installed in the well.
There is a known method for stimulation of oil formation fluid during oil production which includes the creation of an oscillating process directly in the treated oil fluid by carrier electromagnetic waves in the 3*10-5 to 3*1014 Hz frequency range, which modulate information signals resonant to hydrocarbons of the treated oil fluid and form standing waves (patent No. RU2281387 C2 , E21B 43/16, dated April 20, 2006). Directional standing waves are formed using a resonant wave device (generator) submerged in the well, and the control of resonant standing waves is carried out by an antenna field positioned at the surface which includes movable resonant modules, waveguides, etc.
The use of the known method for resonance and wave stimulation of the well oil fluid enables the reanimation of wells with a low flow rate, flooded areas, low-gravity oil, etc., by increasing oil recovery efficiency, oil quality and rheological properties, as well as reducing the water content in the pumped-out fluid.
However, the known method has a considerable disadvantage in that the two subsystems, the ground level and the submerged systems, must be closely coordinated, which requires a complex algorithm for adjustment of the subsystems and, accordingly, provision of an appropriate and reliable well-to-surface communications channel.
The method closest to the one in the invention, is a method for stimulation of oil field downhole area using the electromagnetic protector of the well electric centrifugal pumping plant; the protector forms an electromagnetic field in the downhole area using an electromagnetic signal radiator connected to the generator output (patent No. RU2444612 , IPC E21B 37/00 dated March 10, 2012). The radiator winding's outputs are connected to a variable capacitance diode with its control input connected to the output of the control unit controlling the generator operation according to the signal from the wave analyzer. The device has a channel for communication with the surface. The generator forms short pulses at the frequency determined by the control device in order to provide free resonant oscillations in the radiator circuit, the wave analyzer unit estimates the dominant frequency expected value and dispersion of free oscillations occurred in the emitter circuit and generates a feedback signal to the control device in order to adjust the frequency using the variable capacitance diode In this case, wave stimulation of the downhole area is formed by the radiator circuit and based on settings decided in advance allowing for the particular composition of the deposits according to empirical laboratory and production data.
However, this method does not provide an adequate level of resonant wave stimulation of the fluid and the productive formation taking into account the entire range of downhole area parameters. Accordingly, it is not efficient enough to increase oil production and is only a specific means of protecting wells and production equipment against hydrated and hydrocarbonaceous deposits of a certain type.
The objective of this invention is to reduce fluid viscosity, separate the fluid into light hydrocarbons and energized water, increase the drainage function of fractures, capillaries and pores in the productive formation, and to reduce natural hydrated and hydratocarbonaceous deposits on the downhole area elements, that is the electric centrifugal pumping plant, flow column, and casing pipe, through resonant stimulation of fluid hydrocarbons and energized aqueous salt solutions, with low power consumption and using comparatively simple equipment.

Summary

The formulated problem is solved by a method for stimulating the downhole area during hydrocarbon production in which a device with a radiator and a controlled generator is positioned on the base of the electric submersible element of the electric centrifugal pumping plant in order to create an electromagnetic wave field in the downhole area, in which, unlike the prototype, the electromagnetic wave field is radiated at a frequency that is resonant for the downhole area and determined on the basis of practical experience, modelled results, or testing, which testing is carried out at specified intervals, and during intervals between two tests the generator is operated in the resonant frequency mode, at the resonant frequency being determined during testing, with the radiator forming standing electromagnetic waves which disperse the wave energy throughout the whole downhole area.
The essence of the method according to the invention consists in the creation of a high-frequency axial electromotive force (emf) of conductivity in the downhole area due to electric charge carriers in this area, namely, electrons in metal, ions in solution, charged solid particles and emf polarization of dielectric molecules, which, in turn, causes a coaxial electromagnetic field in the downhole area; the coaxial electromagnetic field is dispersed in the form of standing waves, being constantly stimulated by the electromagnetic oscillation radiator at the resonant frequency which is determined by available practical experience, modelled results, or testing. For example, the length of the standing wave equals 2,498 m at a frequency of approximately 120 kHz. The standing waves formed in the electromagnetic field disperse wave energy through the downhole area which facilitates the formation of homogeneous seed crystals in the oil well fluid and, consequently, crystals formed in the fluid are transported by the fluid without being deposited on the DAE surfaces, as homogeneous seed crystals attract material from the solution ten times more strongly than heterogeneous seed crystals on the surface and in consequence crystals are formed as suspended solids in the fluid.
Additionally, the resonance and wave stimulation results in the excitation and separation of hydrocarbons in the fluid into lighter fractions, which leads to reduced hydrocarbon viscosity and consequently, increased hydrocarbon mobility both in the well and in the productive formation zone around the well. The resonance and wave stimulation also contributes to the increased drainage function of fractures, capillaries and pores in the oil field due to the removal of:

settled and accreted heavy hydrocarbons and asphaltene-resin-paraffin deposits;
clays, colloid dispersed formations, microparticles of rock, etc., dissolved and/or washed out of the fluid by energized water;
absorbed and strongly bound water on the surface of mineral particles.

Detailed Description

The claimed method is implemented in the following way. Before the well assembly is lowered, a sealed container with the generator and the radiator is fixed and connected to the electric submersible motor (ESM) base of the ECPP. The assembly is lowered into the well. When the ESM is started, the generator is switched on, as the device is supplied from the stator winding of the ESM, similar to the prototype. If the resonant excitation frequency is known in advance through available practical experience or modelled results, the generator is started at this frequency. Otherwise, testing is carried out. For example, the testing mode is enabled and the generator excites the radiator to emit very short power pulses at intervals. The shorter the pulse is, the wider the spectrum is. Thus, resonant damped harmonic oscillations with the frequency and the damping period depending on the environmental parameters are set up in the radiator. Once the frequency and the damping period are determined, the generator is switched to the resonant frequency radiation mode with the power determined according to the damping period which corresponds to the operating mode. Resonant standing electromagnetic waves form along the axis in the downhole area both in test mode and in operating mode.
It should be noted that in the claimed method fluid is conventionally moved from the formation reservoir to the production well due to the differential pressure drawdown in the productive formation caused by reducing the dynamic level of the oil well fluid in the casing string of the well, which is consistent with well-proven the hydrocarbon production technology.
Low power consumption is a not insignificant advantage of the claimed method, the generator power consumption for radiation is approximately 100 W. The device is concentrated in the submersed part, and additional surface equipment, a communication channel, etc., are not needed.
Thus, the use of the claimed method for resonant wave stimulation of the fluid and the downhole area allows wells to be revived and significantly extends the life of oil fields with low flow rate, flooded areas, low-gravity oil etc, due to the increase in oil recovery efficiency, oil quality and rheological properties. Moreover, the method provides protection of the downhole area elements from harmful deposits.

Claims

A method for stimulation of a downhole area during hydrocarbon production comprising
positioning of a device with a radiator and a controlled generator at a base of an electric immersible electric motor of an electric centrifugal pumping plant to create an electromagnetic wave field in the downhole area,
characterized in that
the electromagnetic wave field radiation is provided at a resonant frequency for the downhole area, which is predetermined based on test results,
where in test mode the generator excites the radiator to emit very short power pulses at intervals to set up resonant damping harmonic oscillations with the frequency and the damping period depending on the environmental parameters in the radiator,^[1] and
where in operating mode the generator is switched to the resonant frequency radiation mode with the power determined according to the damping period,^[2] wherein resonant standing electromagnetic waves form along the axis in the downhole area both in test mode and in operating mode,^[3] the standing electromagnetic waves disperse wave energy throughout the downhole area.