RU2840848C1 - Method for production of hard-to-recover liquid minerals prone to temperature phase transition - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to a method of extracting a liquid mineral prone to temperature phase transition. Inclusion of the packer element into the composition of the straight tubing string, above which the tubing string represents a double pipe. Further, method includes setting a packer cutting off interval of geological section with low (below 35 °C) temperatures. Then, heated to 50-60 °C the heat carrier is supplied in the inter-pipe space of the double tubing string with its output to the inter-tube space between the double tubing string and the production casing string with subsequent cycling in the heat carrier pumping system. Thus effective heating of tubing string and formation fluid is performed above packer seal. Then, influx is caused from the formation with fluid supply to already heated tubing string. Wellhead connections also shall be equal to diameter equal to tubing string diameter, be able to be connected via at least two parallel independent from each other choke batteries and be under conditions of constant heating not lower than 40 °C, wherein heat carrier temperature is instrumentally controlled at annular space outlet.

EFFECT: improving efficiency of well development and possibility of well production of strong brines without risks of salting of tubing string and wellhead.

1 cl, 1 dwg

Description

The invention relates to borehole methods for extracting hard-to-recover (HTR) liquid minerals prone to temperature phase transitions, in particular concentrated brines, in the rare metal lithium and bromine mining industry. It ensures the prevention of salt crystallization from supersaturated natural brines during their extraction from a borehole.

Concentrated natural brines, which contain industrial concentrations of lithium, rubidium, bromine, saturating deep productive strata and moving during production from the bottomhole to the wellhead, opening intervals of permafrost or low-temperature rocks in the geological section, are supercooled and undergo a temperature phase transition, the consequence of which is contamination of the well equipment with solid formations, partial or complete blockage of the column space with precipitated salts and a decrease or complete cessation of the output of natural brine from the well. Precipitation of salts in the column and the resulting salt plugs do not allow for borehole extraction of brines in a continuous mode of well operation from the productive strata.

A method is known for extracting a liquid mineral prone to a temperature phase transition (RU Patent No. 2229587, E21B 43/00 (2000.01), published: 27.05.2004), according to which, in order to protect the production casing from solid formations settling on it from the extracted liquid mineral during its movement from the productive formation to the wellhead, an absorption zone is formed in the well by means of hydraulic fracturing before lowering the production casing, the productive formation is opened and, during development, thermostatting is carried out by pumping a coolant through the annular space into the absorption zone. The method ensures maintaining the temperature of industrial lithium-bearing brines transported through elevator pipes from the bottomhole to the surface, above the temperature of the onset of salt crystallization. The critical temperature of the onset of salt crystallization from the brine is 25°C.

The disadvantage of this method is the possible decrease in the absorption zone intake capacity during operation, and in this case - the impossibility of providing circulation through the annular space through which the flow of industrial lithium-bearing brines (brine) rises to the surface, as well as the impossibility of simultaneous extraction of gas, gas condensate and industrial lithium-bearing brines - brine. As a consequence, the impossibility of heating the elevator column

A method is known for reducing heat exchange in a well during the development of a multi-layer field (RU Patent No. 2591325, E21 B 36/00 (2006.01), E21 B 37/00 (2006.01), F04D 13/10 (2006.01), F04F 5/14 (2006.01), published on 20.07.2016), consisting of a thermostatting effect due to the creation of a vacuum behind the production casing by including a jet pump in the wellhead piping, operating due to the formation fluid.

The disadvantages of this method include the necessary periodic replacement of the jet pump due to its erosive wear, as well as a large pressure drop on the pump itself, which can lead to cooling of the formation fluid directly in the wellhead equipment and the precipitation of solid sediment.

The closest technical solution in terms of the set of essential features is the method of borehole extraction of liquid minerals prone to temperature phase transition (see Russian Federation Patent No. 2361067, E21B 43/00 (2006.01), E21B 37/00 (2006.01), published on 10.07.2009), which involves pumping hot coolant through a closed circulation system formed by placing an additional suspended process column between the conductor and the production column, connecting the annular and internal space of the suspended process column and the surface tank and pumping equipment through the wellhead piping, according to the principle of communicating vessels.

The disadvantage of this method is the complication of the well design and wellhead piping due to the additional large-diameter casing (significantly affects the cost of well construction), and the low efficiency of the elevator column heating, since there is a sufficient number of "heat screens" and the heating of the production column with the heat carrier is carried out first by the production column, which in turn heats up a fairly large volume of liquid between the production column and the elevator column, and only then the elevator column itself and the fluid in it are heated. As practice has shown, insufficient heating of the fluid can lead to the crystallization of salts from natural brines, which leads to the salting of the elevator column and wellhead piping.

The objective of the proposed invention is to develop a method (sequence of operations) in the well development cycle by increasing the efficiency of heating the lift column in order to increase the efficiency of production of formation fluids from high-pressure formations saturated with strong brines, without the formation of salt crystals in the lift column and wellhead piping.

The technical result is an increase in the efficiency of well development and the possibility of borehole production of strong brines without the risk of “salting of the lift column” and wellhead piping.

The technical result is achieved by the proposed method for extracting a hard-to-recover (HTR) liquid mineral resource prone to a temperature phase transition, including protecting the lift column of the production well from solid formations settling on the walls of the column from the extracted mineral resource during its movement from the productive formation to the wellhead by thermostatting the column in the interval of the geological section with low (below 35°C) temperatures, in the interval of the probable phase transition by continuous or periodic pumping of a hot coolant - a solution of sodium chloride or calcium and magnesium chlorides, and removal of the liquid mineral resource from the productive formation, wherein the pumping of the hot coolant is carried out through a closed circulation system with subsequent cycling of the coolant. This method is distinguished by the fact that in the well development cycle, a closed circulation system is formed by including a packer element in the equal-passage elevator column, above which the elevator column is a double pipe. Then, the packer is seated at a given point and the coolant heated to 50-60 degrees Celsius is supplied to the intertube of the double elevator column and its outlet to the annular space - the intercolumn space between the double elevator column and the production casing, with subsequent cycling in the coolant injection system at the wellhead. This effectively heats the elevator column and the formation fluid above the packer seal. Then, the inflow from the formation is called up with the fluid supplied to the elevator column already heated in the upper part above the packer. The wellhead piping must also be of equal diameter, equal to the diameter of the elevator column and must have the ability to choke through at least two parallel choke batteries independent of each other, and must be in conditions of constant heating of not lower than 40 degrees Celsius, while the temperature of the coolant is instrumentally controlled at the outlet of the annular space (the inter-annular space between the double elevator column and the production casing), while the inflow is called up without replacing the entire well with a lighter flushing fluid, but only by pumping a lighter, light liquid heated to 40-50 degrees Celsius - brine (coolant), after its stabilization, i.e. discharge of a certain amount of salts in the pit during cooling) from the brine accumulator into the tubular space of the elevator column for absorption into the formation, with subsequent discharge of excess pressure, creation of a depression on the formation and obtaining formation fluid through the tubular space.

In turn, well killing is performed by pumping a light liquid - brine from a brine accumulator, preheated to 40-50 degrees Celsius into the pipe space for absorption into the formation, followed by squeezing with a buffer liquid and heavy drilling mud, followed by breaking the packer and direct circulation with heavy drilling mud.

The brine from the brine accumulator loses some of its natural salts due to salting out due to changes in the thermobaric conditions at the wellhead relative to the reservoir conditions.

The main advantage of the claimed method is more efficient energy consumption and direct heat supply directly to the lift column, and not through the screen of the production column and liquid in the annular space. Also, in the prototype method, it is possible to heat the lift column only to the depth of the conductor lowering. In the method we propose, the heating depth is determined based on the depth of the packer installation, which is calculated from the temperature gradient of the well section. All operations in the bottomhole formation zone and well operations (replacing brine heated to 40-50 degrees Celsius with heavy drilling mud - killing a well with abnormally high formation pressure (AHRP), switching the well to drilling mud with a lower density) are carried out with the mandatory placement of hot (not lower than 40°C) light liquid - natural brine - in the bottomhole formation zone (BFZ) and the lower (100 m) part of the wellbore after its stabilization, i.e., dumping a certain amount of salts into the pit during cooling.

The formations with abnormally high formation pressure (AHFP) selected for development, saturated with strong brines, are super reservoirs with formation pressure gradients of 2.42 MPa per 10 m and more and permeability in Darcy units (1000 mD and more). At the same time, these formations are distinguished by high values of injectivity at repression from 1 kgf/ ^cm2 above the formation pressure. This effect allows performing manipulations to cause an inflow in the lift column equipped with a packer, without replacing the entire well with a lighter flushing fluid, but only pumping a lighter liquid heated to 40-50 degrees Celsius into the tubular space for absorption into the formation, with subsequent release of excess pressure, creation of a depression on the formation and obtaining formation fluid through the tubular space. This is an extremely important point, since leaving formation fluid in the annular space (behind the elevator column) can lead to serious consequences in terms of salt crystallization and loss of elevator column mobility. At the same time, by adjusting the location of the packer installation according to the calculation (based on the temperature of the wellbore at a certain depth and laboratory tests for the temperature of the onset of salt crystallization from strong brines of a specific field and formation) and causing an influx by pumping a lighter heated liquid (brine from which salts have already partially precipitated) for absorption, the above effect can be eliminated.

Example of implementation of the invention

As an example, typical conditions are shown when drilling into local layers saturated with strong brines, which are classified as hard-to-recover (HTR) liquid minerals, with abnormally high formation pressure (AHRP) and high filtration-capacity properties at one of the oil and gas condensate fields of the Lena-Tunguska hydromineral-oil and gas province.

The depth of lowering the production casing string is 178 mm - 1890 m.

Next is an open shaft 1890-1920 m with a diameter of 152.4 mm.

The depth of the high-pressure brine-saturated formation is 1900-1920 m.

The pressure in the high-pressure gas-saturated formation is 47.7 MPa (formation pressure gradient is 2.511 MPa per 10 m).

The flow rate of a highly permeable brine-saturated formation with abnormally high pressure is up to 7000 ^m3 /day with a depression of up to 12 MPa.

The density of strong brine is up to 1470 kg/ ^m3 .

Fig. 1 shows the well structure:

1 - well;

2 - double lifting column above the packer;

3 - conductor;

4 - production casing;

5 - brine-bearing layer;

6 - the lifting column of pump and compressor pipes below the packer;

7 - wellhead piping;

8 - capacity for heating the coolant;

9 - ground pumping equipment;

10 - packer.

Also shown in Fig. 1 are the depth of occurrence of the AHPP formation containing brine (brine) and the depths of lowering the equipment according to an example of implementing the invention. The arrows indicate the direction of movement of the heat-transfer fluid.

A tubing string of 6 tubing pipes (TU) with a diameter of 73 mm (hereinafter referred to as TU 73) with a wall thickness of 5.5 mm (coupling outer diameter of 89 mm) is lowered into the well to a depth of 1870 m with a packer 10. Packer 10 for a production casing string with a diameter of 178 mm (PRO-YADZH-O-152-62-350, 3PMS-YAM-151-62-350 or an analogue) is installed at a depth of 1700 m. Above packer 10, the tubing string is lowered as a double string in the factory double string options (for example, for core hydraulic transport systems (CHS) a double light-alloy drill pipe TBDL-75), or in the absence of double pipes, TU with a diameter of 114 mm with a wall thickness of 5.5 mm. The internal space of the tubing 73 is tied to the wellhead piping for the production of strong brines. The intertube space of the double tubing string 2 and the annular space between the double tubing string 2 and the production casing string 4 with a diameter of 178 mm are tied with a wellhead sealer (for example, a sealing unit of the well flushing equipment kit (WFC)) with a branch with flexible hoses through an extended cable entry of the Christmas tree faceplate to a closed circulation system for heating and pumping in the coolant. The packer is seated and pressure tested at 300 kgf/ ^cm2 (adjusted taking into account formation pressures). Next, the heat carrier heated to 50-60 degrees is fed into the intertube of the double elevator column 2 and exits into the inter-annulus space between the double elevator column 2 and the production casing column 4 with a diameter of 178 mm, followed by cycling in the heat carrier injection system, then an inflow from the formation is called up (by pumping a CaCl ₂ brine heated to 50-60 degrees Celsius with a density of 1.25 g / cm ³ for absorption into the AHPP formation with subsequent relief of excess pressure and opening of the pipe space with the creation of a natural depression on the formation) with the exit of fluid from the formation into the elevator column already heated above the packer 10, while the wellhead piping 7 must also be of an equal diameter equal to the diameter of the elevator column, and must be in conditions of constant heating of at least 40 degrees Celsius.

In this case, the inflow is called up without replacing the entire well with a lighter flushing fluid, but only by pumping a lighter in density liquid (brine) heated to 40-50 degrees Celsius into the tubular space of the lift column for absorption into the formation, followed by a release of excess pressure, creation of a depression on the formation and obtaining formation fluid (hard-to-recover (TRIZ) liquid mineral) through the tubular space. In turn, the well is killed by pumping a light liquid (brine) from the brine accumulator, heated to 40-50 degrees Celsius into the tubular space for absorption into the formation, followed by squeezing with a spacer liquid and heavy drilling mud, followed by breaking the packer and direct circulation of the heavy drilling mud.

Claims (1)

A method for extracting a liquid mineral prone to a temperature phase transition, including protecting the wellbore lift string from solid formations settling on the walls of the column from the mineral being extracted during its movement from the productive formation to the wellhead by thermostatting the column in the interval of the geological section with temperatures below 35°C, in the interval of the probable phase transition by continuously or periodically pumping a hot coolant - a solution of sodium chloride or calcium and magnesium chlorides, and removing the liquid mineral from the productive formation, wherein the hot coolant is pumped through a closed circulation system with subsequent cycling of the coolant at the wellhead, characterized in that in the well development cycle the closed circulation system is formed by including a packer element in the composition of the equal-passage lift string, above which the lift string is a double pipe, then the packer is seated at a given point and the heat carrier heated to 50-60°C is supplied into the intertube of the double lift column with its outlet into the annular space, namely the intertube space between the double lift column and the production casing, then the inflow from the formation is caused by supplying fluid into the lift column already heated above the packer, while using a wellhead piping also of an equal-bore diameter equal to the diameter of the lift column and having the ability to be choked through at least two parallel choke batteries independent of each other, the wellhead piping is maintained under conditions of constant heating of at least 40°C, while the temperature of the heat carrier is instrumentally monitored at the outlet from the annular space, and the inflow is caused by pumping a lighter in density, heated to 40-50°C heat carrier fluid into the tube space for absorption into the formation, followed by a release of excess pressure, creating a depression on the formation and obtaining a formation fluid through the tubular space of the lift column, and the well is killed by pumping fluid from the brine accumulator, heated to 40-50°C, into the tubular space of the lift column for absorption into the formation, followed by squeezing with a spacer fluid and heavy drilling mud, followed by breaking the packer and direct circulation with heavy drilling mud.