RU2755101C1 - Method for evaluating effectiveness of downhole filters used in sagd-wells during operation of fields with high-viscosity oil, and stand for its implementation - Google Patents

Abstract

FIELD: comparative thermohydraulic testing.

SUBSTANCE: inventions group relates to means for comparative thermohydraulic testing of the throughput of downhole filters. A method is proposed, in which the tested downhole filters are installed in compartments separated by vertical partitions in the lower zone of a housing with heat-insulated walls, equipped with a hermetically closing hatch with a safety valve, the compartments are filled with sand, a liquid medium is introduced into the housing, simulating the formation fluid, so that the heat supply unit is completely immersed in a liquid medium, with a hermetically closed housing hatch, a heat carrier is supplied - steam, followed by the direction of this heat carrier through a connecting pipeline to a steam supply unit in the upper area of the housing, in the form of a perforated pipe and equipped with a steam outlet line with a pressure gauge and shut-off valves installed on it; of the case, and filtering the liquid medium through sand and the tested filters with the filtrate discharge through the outlet pipe with shut-off valves, which is equipped with each compartment. A stand is also proposed, containing a housing with heat-insulated walls, with a hermetically closing hatch with a safety valve, with the execution inside the housing in its lower zone, two compartments for filters, separated by partitions, and equipped with shut-off valves and a temperature sensor, inside the housing above the compartments are arranged in series the height of the heat supply and steam supply units, connected by a pipeline, the heat supply unit in the form of a tubular element is equipped with a coolant inlet line, and the steam supply unit - with a steam outlet line with a pressure gauge and shutoff valves, while the heat supply and steam supply units are equipped with temperature sensors, and the stand body is equipped with a pressure control sensor. The invention is developed in the dependent claims.

EFFECT: providing an assessment of the throughput of downhole filters with a wide range of exposure parameters, while ensuring the reliability of test results by approaching test conditions to full-scale ones, by exposure to high pressure, temperature and formation fluid.

6 cl, 1 dwg, 2 tbl

Description

The group of inventions relates to the oil industry and can be used for comparative thermo-hydraulic tests of the throughput of downhole filters, as well as assessing the ability of filters to retain mechanical impurities, with simulating well conditions for various values of temperature and pressure.

To understand the essence of the problem, we explain the following. SAGD wells are wells that develop high-viscosity oil fields using steam gravity drainage. The process of gravitational steam stimulation begins with the preheating stage, during which (several months) steam is circulated. The injected steam, due to the density difference, makes its way to the top of the reservoir, creating an expanding steam chamber. At the interface between the steam chamber and cold oil-saturated strata, the process of heat exchange constantly occurs, as a result of which the steam condenses into water and, together with the heated oil, flows down to the production well under the influence of gravity. The upward growth of the vapor chamber continues until it reaches the top of the formation, after which it begins to expand to the sides. In this case, the oil is always in contact with the high-temperature steam chamber. These wells are associated with the development of deposits of heavy oils and natural bitumen (https://vseonefti.ru/upstream/sagd.html).

As an example of such wells, one can cite, for example, the Yaregskoye field, where a significant number of incidents of submersible equipment failures were noted, due to the high content of mechanical impurities - sand of various fractions.

The analysis of the well operation showed that 89% of the removed mechanical impurities have a fractional composition of up to 250 microns, of which 47% have a size of up to 100 microns. 11% of the wells with intense sand production showed the presence of sand with a particle size of more than 250 microns.

The filter slot size is 180 µm. In this case, it is assumed that some part of the holes can have a size of up to 250 microns, since the filters are manufactured by means of laser cutting.

In wells equipped with screen-type filters (wire-slotted) - up to 24%, with a slot size of 250 microns, and in wells equipped with an additional filter 73 mm × 30 m at the pump inlet (up to 13%, with a slot size of 100 microns).

Based on the experience of production companies, the sand production problem in SAGD production wells is temporary - until a natural gravel pack forms on the outside of the casing.

All filter designs used in the field did not prevent sand production at the initial stage of well operation. In this case, the active phase of sand production can occur for a rather long time, depending on the possibility of the well reaching the regime, and the formation of a natural gravel pack.

The formation of a natural filter can be accelerated only by ensuring continuous withdrawal of fluid from the well. It is not feasible to carry out gravel reclamation into the annulus with a uniform distribution along the entire length of the horizontal end - it is not feasible, given the constant premature failure of submersible pumping equipment.

It became necessary to use downhole filters, the design of which provides an imitation of the operation of a natural gravel filter, with bench tests.

Testing of downhole filters for SAGD-wells using the proposed stand allows evaluating the efficiency of operation of downhole filters of various designs in conditions close to the operating conditions of SAGD-wells, namely, the speed and quality of filtration. Additionally, the proposed stand can allow to determine the rate of formation of a natural gravel pack by reducing the solids content in the filtrate, as well as reducing the size of sand particles.

These parameters are critical in the development of high-viscosity oil fields using steam-assisted gravity drainage (SAGD). So the quality of downhole filters will affect the efficiency of horizontal wells operation, namely, the duration of trouble-free operation of submersible pumping equipment, ensure the absence of sand plugs in the horizontal wellbore, etc. Thus, the choice of the optimal design of the filter element will ensure high performance of the well and downhole submersible equipment.

A well-known stand for testing downhole devices for purifying fluid, including filters of downhole pumping units, which contains a pump, a control station, a storage tank, pipelines with valves, a pressure gauge on the pump discharge pipeline, a mechanical impurity dispenser, a vertical casing in which is located a device for fluid purification, a sludge collector attached to the bottom of the vertical casing, a filter element in the flow line, a measuring tank, a free gas supply unit for the device under study, which includes a compressor, a control throttle, a diaphragm, a gas meter and a gas check valve ( RF patent №124497). The supply of liquid through the filter in the known stand is carried out by means of a pump that creates an overpressure at the inlet to the filter. The specified mode of operation is not typical for filters of downhole pumping units, since through these filters the liquid is pumped out, and not pumped into them. Therefore, this stand is unacceptable due to the fact that during its operation the operating conditions of downhole pumping units are not fully reproduced.

Known stand for testing filters of downhole pumping units (RF Patent No. 2687690). The design of the specified known stand consists of a sealed housing, a filter located in it, a pressure and temperature source, and a pressure sensor.

Thus, all known devices do not allow:

- work with high-viscosity oil by displacing it from the rock matrix using steam at a given temperature and pressure;

- to conduct simultaneous tests of several full-size well screens of various designs under the same conditions, there is also no possibility of testing when simulating the horizontal orientation of wellbores - up to 4 at a time;

- Place full-size downhole filters in the rock mass or its imitation (by granulometry), as well as use crude oil directly from the field;

- to determine the comparative rate of filtration of the formation fluid of all samples at the same stages of the stand simulating well conditions;

- to take samples from each filter at the same time for the purpose of further analysis of the fluid (oil / water content, amount of filtrate and its granulometric composition);

- to assess the rate of formation of a natural filter, as well as to make a qualitative comparison of well filters of various designs for this parameter.

At the same time, the prior art did not reveal the known stands for assessing the effectiveness of downhole filters used in SAGD-wells during the operation of high-viscosity oil fields, therefore, it is not possible to choose the closest analogue to the claimed invention.

A single technical result achieved by the proposed inventions consists in providing the possibility of assessing the throughput of various downhole filters with a wide range of impact parameters, such as pressure and temperature, while ensuring the reliability of the test results obtained by approaching test conditions to full-scale ones, through the use of technical means for modeling by exposure to high pressure, temperature and formation fluid.

The specified technical result is achieved using the proposed method for assessing the effectiveness of downhole filters used in SAGD-wells during the operation of fields with high-viscosity oil and a stand for its implementation, and is characterized by the fact that the tested downhole filters are installed in compartments separated by vertical partitions and made in the lower zone the body of the stand with heat-insulated walls, equipped with a hermetically closing hatch with a safety valve, fill the indicated compartments with sand imitating the sand reservoir of the SAGD-well, inject a liquid medium that environment and installed in the middle zone inside the housing above the indicated compartments, was completely immersed in the specified liquid medium, with a hermetically closed housing hatch, the coolant-steam is supplied to the heat-supply unit with the subsequent direction of this coolant through the connecting pipeline to the steam supply unit in the upper area of the body, made in the form of a perforated pipe and equipped with a steam outlet line with a pressure gauge and shut-off valves installed on it, the pressure inside the body is raised by the flow of steam from the specified perforated pipe with its shut-off valves closed, the value of which is controlled using a pressure sensor installed in the housing, by means of the created pressure, the liquid medium is filtered through sand and the tested filters with the filtrate discharge through the outlet pipe with shut-off valves, which is equipped with each compartment, and the quantity, speed and quality of the discharged filtrate are judged about the effectiveness of the tested downhole filters.

The stand for evaluating the efficiency of downhole filters used in SAGD-wells during the operation of fields with high-viscosity oil contains a body with heat-insulated walls, equipped with a hermetically closing hatch with a safety valve, with at least two inside the body in its lower zone, separated by vertical partitions , compartments for placing the tested filters in them, and equipped with each of them with an outlet pipe with shut-off valves and a temperature sensor, inside the body of the above mentioned compartments are placed in series in height in the middle and upper zones of the body, respectively, a heat supply and a steam supply unit, interconnected by a pipeline, a heat supply the unit, made in the form of a tubular element, is equipped with a coolant inlet line, and the steam supply unit, made in the form of a perforated branch pipe, with a steam outlet line with a pressure gauge and shut-off valves installed on it, while the heat supply and steam supply units with are equipped with temperature sensors, and the stand body is equipped with a pressure control sensor.

Lower housing area occupies _^half the volume of the housing.

In this case, the outlet pipes of each of the compartments are equipped with a container for collecting the filtrate that has passed through the tested filter.

The pressure control sensor in the housing is located in its upper part above the steam supply unit.

The optimal number of compartments in the case is four.

The specified technical result is achieved due to the following.

Due to the fact that the walls of the case have thermal insulation (for example, mineral insulation) over the entire surface, it is possible to reduce heat loss and ensure a uniform temperature throughout the test volume.

Separating the filters from each other by partitions made it possible to simultaneously test up to four filters under the same thermobaric conditions, which ensures the objectivity of the comparative assessment of the results obtained.

In view of the fact that the stand additionally contains sensors for the temperature of the medium inside the case, it became possible to continuously monitor the temperature of the medium during the testing of filters and set the temperature of the medium based on the variety of operating conditions of the downhole filters.

Due to the fact that the manhole is equipped with a safety valve, it is possible to maintain a constant - safe pressure during the test.

Equipping each compartment of the well filter with an individual temperature sensor allows you to control the entire testing process, as well as to compare the recorded parameters with the filtration rate for the tested filter samples.

The presence of a branch pipe with shut-off valves for draining the filtrate at each compartment makes it possible to take samples of the filtrate and evaluate the filtration rate.

Equipping the stand with a pressure and temperature source in the proposed version allows you to accurately simulate the operation of a SAGD well when displacing a high-viscosity fluid from a rock matrix.

Placement of heat supply and steam supply units, respectively, connected to each other by a pipeline, inside the casing above the compartments, in succession in height in the middle and upper zones of the casing, also makes it possible to simulate well conditions of SAGD wells, since the heat supply unit provides heating of the liquid medium inside the stand body, and the steam supply unit ensures the creation of the required pressure inside the stand body and the effect of steam on the specified liquid.

Due to the fact that the heat supply unit is completely immersed in a liquid medium inside the body, protection against overheating of this unit is provided, as well as complete heating of the entire volume of the liquid medium in order to ensure that liquid with the same temperature enters the compartments with filters, because the accuracy of the research will depend on this.

Due to the design features of the proposed stand, as well as the operations and modes of the proposed method of testing on it, an increase in the accuracy and reliability of the results obtained is ensured.

The inventive method for assessing the effectiveness of downhole filters by implementing the proposed method using the inventive stand is described below in an example of execution.

The proposed stand is illustrated by drawing FIG. 1, which shows a general view of a test bench for four filters.

The stand is a sealed body 1 in the form of a cube or parallelepiped, made of sheet steel corresponding to the expected pressures of thickness and steel grade. The walls of the housing 1 are thermally insulated along the entire outer surface. In the inner lower zone 18 of the body 1, vertical partitions 8 are installed, which divide the lower zone 18 of the stand body into separate compartments 22. The choice of the number of compartments can correspond to the number of tested samples of downhole filters 2 (I, II, III, IV ...). The optimal number is four compartments for four types of filters (shown in Fig. 1). Each compartment 22 is equipped with an outlet 6 with shut-off valves 23 for draining the filtrate and a temperature sensor 7. The upper part of the stand is equipped with a hatch 3 with a safety valve 4 located on it 4. In the middle zone 19 of the housing 1 there is a heat supply unit made in the form of a tubular element 8, equipped with a line 11 of the input of the heat carrier - steam. In the upper area 20 of the body there is a steam supply unit made in the form of a perforated pipe 9 for creating excess steam pressure in the body 1, equipped with a steam outlet line 12 with a pressure gauge 13 and shut-off valves installed on it 14. The tubular element 8 and the perforated pipe 9 are interconnected pipeline 10. Tubular element 8 and perforated pipe 9 are equipped with temperature sensors 21 and 15, respectively. The body 1 of the stand is equipped with a pressure control sensor 16 located in the upper zone 20.

The proposed method, which is implemented through the work of the inventive stand, is carried out as follows.

Immediately before starting work, the stand is pressed into a pressure that is approximately 10% higher than the pressure at which the tests will be carried out. Shut-off valves 14 on the steam outlet line 12, shut-off valves 23 on the outlet pipes 6 of the compartments 22 are closed. In the lower zone 18, the cavity of the compartments separated by partitions 5, after installing the well filters 2 in them, through the hatch 3 are covered with sand 24 of the corresponding granulometric composition. The most optimal use of the reservoir sand of high-viscosity oil deposits, obtained, for example, in the process of flushing horizontal wells. Next, a liquid medium is poured into the body, consisting of formation water and high-viscosity oil (fluid), approximately in a ratio of 1: 2 (you can use an artificially prepared modeling fluid instead of a fluid) with the condition that the heat supply unit 8, made with the possibility of heating the specified liquid medium and installed in the middle zone inside the housing, was completely immersed in the specified liquid medium 25.

After the stand is prepared for operation, the upper opening of the body is hermetically closed by a hatch 3 equipped with a safety valve 4. The safety valve 4 prevents the operating pressure from being exceeded during the experiment. Steam is supplied through the line 11 of the heat carrier, which passes through the tubular element 8, heating the liquid medium 25, then through the pipeline 10, steam is supplied to the perforated branch pipe 9 and then the steam enters the steam outlet line 12. A pressure gauge 13 is located on the steam outlet line 12 for monitoring pressure and shutoff valves 14 to regulate the pressure during testing.

When the required temperature of the liquid medium 25, which is monitored by the temperature sensor 21, is reached, the viscosity of the liquid medium 25 decreases, and it begins to filter through the sand 24 under the influence of excess pressure in the upper zone 20. In this case, the shut-off valve 23 on the branch pipes 6 of the compartments 22 opens. Depending on the throughput of the filter, filtration in different compartments will take place at different speeds. The filtration rate of the liquid medium 25 through each downhole filter 2 (I-IV) is determined in the process of sampling into special measuring tanks 17. For each filter 2, the filling rate of the tank 17 is measured. The filtrate samples in each tank are numbered in the appropriate order for each type of downhole filter separately. If, due to the high filtration rate, any of the compartments has filtered out the entire formation fluid, and steam is released, then in order to continue testing other downhole filters, the outlet 6 is shut off by means of stop valves 23.

During the entire test, the temperature and pressure parameters are monitored by the corresponding sensors 7, 15, 16, 21, installed in certain places in the cavity of the test bench. This allows you to control the entire testing process and evaluate the temperature distribution over the compartments, as well as compare them with the filtration rate through the tested samples of well filters. The information from the sensors is continuously recorded on an electronic medium for further analysis.

Filtrate samples, marked accordingly, after bench tests are sent to the laboratory for the analysis of both the formation fluid itself (water-to-oil ratio), and for quantitative and granulometric analysis of sand in the filtrate samples.

In the course of testing the performance of the proposed stand, work was carried out to test the throughput and filtration capacity of four samples of borehole filters on reservoir fluid and reservoir conditions close to borehole ones of the Yarega oil field.

Loading of sand 24 and liquid medium 25 (1/3 water, 2/3 viscous oil) is carried out through the hatch, which is hermetically closed before testing. It is preferable to use sand from the deposit, directly from the exploited horizon, and if it is not possible, it is necessary to use an analogue of the corresponding granulometric composition. Before loading the sand imitating the sand reservoir and the liquid medium, samples of filters are installed into the sections of the stand body. Before starting work, the shut-off valves on the branch pipes of the compartments with the filter samples are closed, the liquid medium inside the housing is heated to the operating temperature and the stand is pressurized to a pressure that is 10% higher than the test pressure. Pressure and temperature in different areas of the housing are measured in real time by means of sensors with appropriate placement. All test parameters are recorded for later analysis. The opening of the drain shut-off valves of the compartments is carried out simultaneously, while the presence of a liquid outflow is visually recorded. If there is an outflow of filtrate, samples are taken in a container of a fixed volume with measurement of the filling time, for subsequent assessment of the filtration rate on each sample. After that, the containers with samples are marked (No. of filter sample, No. of sample, date and time of sampling). All samples are then transferred to the chemical analysis laboratory to assess, first of all, the presence of mechanical impurities in the filtrate - the amount and granulometric composition, and the ratio of water to oil in the filtrate. After that, a comparative analysis of the filtration rate and quality of filter samples is carried out, on the basis of which the selection of the most effective downhole filter for a particular well is made.

All work was carried out in accordance with the terms of reference for bench testing of downhole filters for the conditions of the Lyaelskaya area of the Yaregskoye oil field.

Four filters of different designs were used as samples:

- a sample of a wire-slotted borehole filter with gravel packing FSPSCH-GN 168 × 150D × 1560 × 1000 × 0.1 × 250 × 250 (slot size 0.1 mm), hereinafter referred to as No. I;

sample of downhole wire-slotted filter FSPSCH 178 × 160D × 1560 × 1000 × 0.1 × 250 × 250 (slot size 0.1 mm), hereinafter referred to as No. II;

sample of downhole wire-slotted filter FSPSCH 178 × 160D × 1560 × 1000 × 0.18 × 250 × 250 (slot size 0.18 mm), hereinafter - No. III

- a sample of a downhole filter (pipe with laser perforation with a slot size of 0.18 mm)), hereinafter referred to as No. IV.

The tests were carried out on the territory of the Test Site using the following consumables:

- sand of various fractional composition from the Yarega oil field (Table 1);

- reservoir fluid from the Yarega oil field (Table 2).

All preparatory work and tests took place in the following order:

1. According to the terms of reference, a stand was manufactured and assembled, in which four samples of downhole filters were installed.

2. Sand from the deposit was evenly poured into each of the four compartments, into the cavity above and below the filter. Provided full filter coverage.

3. Poured about 1000 liters of fluid into the test chamber. The injected fluid consisted of 30% of formation water, the rest was oil.

4. We made the final assembly of the stand, installation of sensors, piping with a mobile unit PPU (mobile steam installation) A 1600/100 based on a KAMAZ vehicle.

5. By pumping steam through line 11 and tubular element 8, the injected fluid and the area of the filters were heated.

6. When the temperature of the fluid reaches 60 ° C, steam is injected into the cavity above the fluid at a temperature of 160-170 ° C through the perforated branch pipe 9 of the stand. With the safety valve 4 on the hatch 3, the pressure in the body cavity was adjusted in the range of 6-7 kg / cm ² . The temperature and pressure parameters were monitored in real time from the monitor on the stand control panel. The above parameters were recorded to a USB drive in automatic mode.

7. In the intervals between filtration stages, 5 batches of filtrate samples from each type of filter were taken. The samples taken are marked with time, date and filter sample #. The received samples are packed in bags and sealed. In the process of pumping fluid through the filters, the following indications were revealed:

The largest flow was observed on sample No. I, then in decreasing order of flow from filter No. IV, No. III, No. II.

8. After pushing through the entire contents of the container (test stand), the stand was left to cool.

9. Then the test samples of the well screens were removed and then sawed to examine the contents inside the screens. No sand was found in the filters.

10. The gap gap of each sample was measured. As a result of measurements, the following data were obtained:

- Sample No. I = 0.1 mm;

- Sample No. II = 0.1 mm;

- Sample No. III = 0.18 mm;

- Sample No. IV = 0.2 mm.

The testing and sampling process was carried out in full and in accordance with the terms of reference for bench testing of downhole filters for the conditions of the Lyayelskaya area of the Yaregskoye oil field. Samples were transferred to the chemical analysis laboratory for further analysis of the filtrate.

The test data of filters on the stand of the proposed design showed that the efficiency of downhole filters varies greatly depending on their design features. Tests have identified the most optimal design, especially for a gravel pack well screen sample. The features of the operation currently used in the field were confirmed, as well as the fact that the effectiveness of the filters increases with the formation of a natural gravel pack. These tests made it possible to clearly show how important the design of filter elements is in terms of the effective operation of SAGD wells, as well as the use of this bench made it possible to exclude the risk of testing well screens on real wells. Since in the case of using an ineffective design of an experimental filter, the operation of an expensive well will be difficult or impossible at all.

In addition, this stand allows you to objectively evaluate the effectiveness of a particular well screen, since the test is carried out at a time in a common environment. It is also worth noting the possibility of using natural materials from the field - the rock composing the productive horizon, formation fluid (oil / water), which naturally increases the quality (accuracy and reliability) of the results obtained.

Thus, due to the fact that the proposed bench simulates the conditions that simulate borehole on SAGD-wells during the operation of high-viscosity oil fields, the reliability of tests is ensured, which will make it possible to issue accurate recommendations to oilmen on the use of specific well screens in specific wells. This will reduce, or even eliminate, the costs of testing experimental designs of downhole filters, incl. taking into account the loss of effective production at pilot wells, increase the resource of submersible pumping equipment, by reducing the flow of mechanical impurities, assess the rate and presence of the formation of a natural gravel filter, and increase the flow rate of the produced fluid.

Claims (6)

1. A method for assessing the effectiveness of downhole filters used in SAGD-wells during the operation of fields with high-viscosity oil, characterized by the fact that the tested downhole filters are installed in compartments separated by vertical partitions and made in the lower zone of the stand body with heat-insulated walls, equipped with a hermetically closing hatch with with a safety valve, fill the indicated sections with sand imitating the sand reservoir of the SAGD-well, inject a liquid medium simulating the formation fluid into the casing in such a volume that a heat supply unit capable of heating said fluid medium and installed in the middle zone inside the casing above the indicated compartments , was completely immersed in the specified liquid medium, with a hermetically closed housing hatch, the heat carrier is supplied - steam, to the heat supply unit, followed by the direction of this coolant through the connecting pipeline to the steam supply unit in the upper area of the housing, made in the form of a perforated branch pipe and equipped with a steam outlet line with a pressure gauge and shut-off valves installed on it, the pressure is raised inside the body by means of the flow of steam from the specified perforated pipe with its shut-off valves closed, the value of which is monitored using a pressure sensor installed in the body, by means of of the created pressure, the liquid medium is filtered through sand and the tested filters with the filtrate discharge through the outlet pipe with stop valves, which is equipped with each compartment, and the efficiency of the tested downhole filters is judged by the quantity, speed and quality of the discharged filtrate. 2. A stand for evaluating the efficiency of well screens used in SAGD-wells during the operation of fields with high-viscosity oil, characterized in that it contains a body with heat-insulated walls, equipped with a hermetically closing hatch with a safety valve, with execution inside the body in its lower zone, according to of at least two, separated by vertical partitions, compartments for placing the tested filters in them, and equipped with each of them with an outlet pipe with shut-off valves and a temperature sensor, inside the body above these compartments are placed sequentially in height in the middle and upper zones of the body, respectively, a heat supply and a steam supply nodes interconnected by a pipeline, the heat supply unit, made in the form of a tubular element, is equipped with a coolant inlet line, and the steam supply unit, made in the form of a perforated pipe, with a steam outlet line with a pressure gauge and shut-off valves installed on it, while the heat The supply and steam supply units are equipped with temperature sensors, and the stand body is equipped with a pressure control sensor. 3. The method of claim. 1, characterized in that the lower housing area occupies _^half the volume of the housing. 4. The stand according to claim 2, characterized in that the outlet pipes of each of the compartments are equipped with a container for collecting the filtrate that has passed through the filter under test. 5. The stand according to claim 2, characterized in that the pressure control sensor in the housing is located in its upper part above the steam supply unit. 6. The stand according to claim 2, characterized in that the optimal number of compartments in the body is four.

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