RU2203410C1 - Thermal-dynamic method of bottom hole zone stimulation of well - Google Patents

Abstract

FIELD: mining industry, completion of operating holes and restoration of output dropped due to mud grouting of bed. SUBSTANCE: electric motor , heater positioned beneath and packers are sunk into well on tubing string. Packers insulate heated interval of well located opposite to productive pool and electric motor from heated interval of well. Cold fluid is pumped, follows lines of electric motor and then is fed into heater. Heated fluid is driven into insulated heated interval of well and further into pool. In this case electric motor is separated additionally by packer from part of well lying above to form cooled interval of well. Cold fluid is pumped from surface into tubing string, follows lines of electric motor in cooled interval of well and is directed through holes in end sections of length of tubing string before feeding into heater. Electric motor and heater are mechanically joined by above-mentioned length of tubing string. Electric motor is employed in drive of heater converting mechanical energy to thermal energy by means of transmission of rotation from electric motor to shaft passing inside length of tubing string. EFFECT: increased heating temperature of fluid in insulated interval of well, raised reliability of method. 1 dwg

Description

 The invention relates to mining and can be used to develop and restore the production rate of production wells, which decreased as a result of plugging (mudding) of the formation by asphalt-resinous and paraffin formations.

 A known method of hydraulic fracturing (Gatiev S.M. et al. Interaction on the bottom-hole zone of oil and gas wells. - M .: Nedra, 1966), which isolate the interval of the formation with packers and increase the pressure to fracture it.

 The disadvantages of this method include its low efficiency, the need to use a string of tubing and bulky pumping units to supply fluid to the under-packer space, which requires significant material and labor costs.

 A well-known throttle heater (Degtyarev B.V., Accountant E. B. The fight against hydrates in the operation of gas wells in the Northern regions. -M.: Nedra, 1976), based on the conversion of the energy of liquid pressure into heat.

 However, the use of a throttle heater is associated with high costs due to the use of at least three tubing columns, as well as low efficiency due to hydraulic resistance and pressure losses in the threaded tubing joints.

 A known method of hydraulic fracturing (Solovyov G.N. et al. Patent 2046184, "Method for hydraulic fracturing, class E 21 B 43/26, 1995), taken as a prototype, in which the pressure is increased in an isolated section of the reservoir by heating the fluid by installing an electric heater.

 The disadvantage is the small amount of energy transmitted to the bottomhole zone.

 A known method of influencing the bottom-hole zone of an oil well (Shipulin A.V., Zagrivny E.A., Kudryashov B.B. et al. Patent 2164597, "Thermodynamic method of influencing the bottom-hole zone"), in which the fluid is heated by turbulent fluid movement during its mechanical stirring.

 However, the electric motor of the device is not cooled, the permissible heating of the bottomhole zone of the well is limited by the temperature characteristics of the insulation of the electric motor.

 A device is known for processing the prefilter part of the formation (L.A. Livshits. Patent 1537798, Е 21 В 43/25), the method of application of which is adopted as a prototype and includes the descent into the well of an electric motor, a downstream heater, packers, isolation by packers of a heated interval of the well and an electric motor from the heated interval of the well, the injection of cold fluid, which flows around the electric motor, and its supply to the heater, followed by the displacement of the heated fluid.

 However, the device for implementing the method has a complex structure, a tubular heater is used, unreliable in high pressure environments, two power cables for the electric motor and a variable-length heater are required to process the filter zone and pump out the well fluid at different depths, pump out the fluid without tubing, the proposed packer design not designed for high pressures.

 The objective of the invention is to increase the temperature of the heating fluid in the isolated interval of the well, increasing reliability.

 The problem is solved in that, using the thermodynamic method of influencing the bottom-hole zone of the well, including the descent into the well of an electric motor, a downstream heater, packers, isolating the packers of the heated well interval against the reservoir and the electric motor from the heated well interval, injecting cold fluid that flows around the electric motor, and supplying it to the heater, followed by displacement of the heated fluid into an isolated heated interval of the well and then into the formation, descent into the well Well, the electric motor, the downstream heater and packers are carried out on the tubing string, the motor is additionally separated by the packer from the overlying part of the well to form a cooled interval of the well, cold fluid is pumped from the surface into the tubing, followed by its flow over the electric motor in the cooled interval of the well and direction before feeding into the heater through openings at the end sections of the tubing segment, which connects the mechanically electric motor and the heater, with how to isolate the well interval heated using packer designed for high pressures, and the motor used to drive the heater, which converts mechanical energy into heat by transmitting rotation from the motor to the heater shaft extending inside the tubing segment.

 An example of a device for implementing the proposed method is illustrated in the drawing, in which: 1 - well, 2 - tubing string; 3 - electric motor; 4 - heater; 5 - tubing section; 6 - shaft; 7 - packers; 8 - holes; 9 - perforation holes of the casing string; thin arrows - supply of cold liquid from the surface; bold arrows - circulation of the heated fluid.

 The method is implemented as follows. A tubing string 2 is lowered into the well 1 to the depth of the reservoir, at the lower end of which the electric motor 3 is directed downward. The heater 4 is placed below the electric motor and connected to the electric motor by a tubing segment 5, inside of which is placed a shaft 6 connecting the rotors of electric motor 3 and heater 4. The electric motor 3 is separated by packers 7 from the heater 4 and from the overlying part of the well. The tubing string 2, as well as the tubing segment 5, have openings 8 at the end sections not covered by the packer 7. When lowering the tubing string 2, the heater 4 is located opposite the perforation holes of the casing string 9.

 The tubing string 2, which is lowered into the well 1, is used for placement on its lower end of the electric motor 3 and heater 4, as well as for supplying liquid from the surface. The electric motor 3 is designed to drive the heater 4. The length of the tubing 5 is necessary for the mechanical connection of the electric motor 3 and the heater 4. The shaft 6 passing inside the length of the tubing 5 is designed to transmit rotation from the electric motor 3 to the heater 4. The packers 7 are used to isolate the electric motor 3 from the heated well interval and from annulus. Holes 8 at the end sections of the tubing string and the tubing segment are necessary for supplying fluid to the isolated interval of the well. Through the perforations of the casing 9, the heated fluid is delivered to the reservoir.

 As an electric motor 3, a typical engine from a serial submersible electric pump (ESP) is used, which is suitable for operation in borehole conditions by technical characteristics.

 The principle of operation of the heater 4 is based on the dissipation of mechanical energy into heat. The fluid is heated due to the turbulent movement of the fluid with its mechanical stirring (patent 2046184) or by pumping it along the circuit: the output of the submersible borehole electric pump - hydraulic resistance - the interval of the borehole isolated by the packers - the entrance of the submersible borehole electric pump.

 To carry out heating from the surface through the tubing string 2, a fluid is pumped into the isolated interval of the well and power is supplied to the electric motor 3. The electric motor 3 drives the heater 4, the fluid is heated in the isolated interval of the well. When injected from the surface of a cold fluid, the heated fluid is forced into the reservoir. Cold liquid before entering the isolated heated interval of the well flows around the electric motor 3, cooling it.

 The initial heating of the liquid during cooling of the electric motor is due to its losses (electrical and magnetic resistance of the stator and rotor, friction and ventilation), as well as due to heat from the heated interval through the packer, tubing section and casing.

 A packer at the lower end of the tubing string separates the isolated interval of the well from the annulus and must be designed for high pressure. The packer on the tubing section between the electric motor 3 and the heater 4 serves only to separate the heated and cooled isolated intervals of the well and does not experience a pressure difference, therefore, it can have a simplified design.

 Two technological options are possible.

 1. The fluid is pumped from the surface into the isolated interval of the well, heated to create pressure and implement decolmation and hydraulic fracturing, then a new portion of the fluid is pumped.

 2. A continuous supply of fluid from the surface is carried out, it is heated in an isolated interval of the well, delivered to the reservoir to maintain reservoir pressure and warm the reservoir fluid.

 The advantages of the proposed heater are that it is possible to heat the fluid in the isolated interval of the formation to high temperatures without fear of damage to the electric motor, which has limited thermal characteristics of the insulation. Increasing the temperature of the fluid promotes decolmation, increases the heating of the formation.

Claims (1)

 Thermodynamic method of influencing the bottom-hole zone of a well, including lowering an electric motor, a downstream heater, packers into the well, isolating packers of the heated well interval against the reservoir and the electric motor from the heated well interval, injecting cold fluid that flows around the electric motor, and supplying it to the heater, followed by displacement heated fluid in an isolated heated interval of the well and further into the reservoir, characterized in that the descent into the well of electric motors a gatel, a downstream heater and packers are carried out on a tubing string (tubing), an electric motor is further separated by a packer from the overlying part of the well to form a cooled interval of the well, cold fluid is pumped from the surface into the tubing, followed by its flow over the electric motor in the cooled interval of the well and the direction before feeding into the heater through the holes in the end sections of the tubing section connecting the electric motor and the heater mechanically, while for zolirovaniya heated wellbore using a packer designed for high pressures, and the motor used to drive the heater, which converts mechanical energy into heat by transmitting rotation from the motor to the heater shaft extending inside the tubing segment.