RU2826393C1 - Downhole sand filter testing device - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to sand control equipment. Device includes a main pump for pumping the mixture and creating pressure, connected to the oil-sand mixture preparation unit, a test cell connected to the sand-oil mixture preparation unit with a sand filter sample installed in it for the sand unit sedimentation, pressure and crimping pressure lines connected to the test cell, pressure sensors and pressure gauges, shut-off and control valves, tank for collection of oil-sand mixture passed through sand filter, electronic scales, data collection and control unit, configured to receive data from pressure sensors, electronic scales, control unit of the main pump. Test cell is made with possibility to create squeezing pressure in it by means of piston transmitting pressure to sand unit from hydraulic pump, connected to pneumatic hydraulic accumulator.

EFFECT: higher information content of the test, multi-parameter evaluation of the sand filter.

3 cl, 2 dwg, 3 tbl

Description

The invention relates to equipment for the oil producing industry, namely to equipment for combating sand production.

State of the art

Sand retention filters are widely used in oil and gas production operations in formations where sand may be carried into the well (sand well). Sand removal from the formation into the well reduces the service life of well equipment, since sand (small particles) clogs flow channels and contributes to equipment erosion. Sand filters (or anti-sand filters) of various configurations are used to retain sand. These can be slot filters, wire filters, perforated filters, multi-layer filters, filters with proppant packing. The performance of well filters is determined by the proportion of sand that the filters retain and the duration of the filters' operation (before it becomes clogged with filtrate). Usually, a compromise is reached on these key characteristics - small-sized filters retain sand better, but clog faster and must be replaced or cleaned. Therefore, well filters (or filter samples in the form of a typical fragment) are tested before operation on special test stands with pumping of sand suspension through samples (fragments) of the filter.

Various methods and appropriate testing devices are used to test borehole sand (or “anti-sand”) filters.

A common testing method is the Constant Flow Rate Brine Flow Test Method, where a sand filter sample (also referred to in the literature as a "coupon") is placed in an open sand pumping system and the formation of the sand pack is monitored using pressure sensors. As the sand settles on the filter, a predetermined pressure difference is achieved across the working cell and different filter types are compared for this parameter.

The patent document US 2023129272 describes a procedure for selecting a suitable sand filter based on modeling and estimating the time of such a phenomenon as "auto-packing time", i.e. the phenomenon of destruction of the bottomhole rock with filling the annular space with large particles (with the formation of a sand plug in the annular space). Such self-packing helps to trap small particles in the wellbore fluid and this extends the service life of the sand filter. The device for testing filter samples is a conical test cell with a pressure sensor. The device also allows you to evaluate the erosion of the sand filter.

A Novel Approach to Constant Flow-Rate Sand Retention Testing (SPE-189515-MS) describes a method for testing filters using sand in oil under a constant pressure difference (Constant Drawdown Oil-Flow Test, CDOF). The test device maintains a constant pressure difference in the working cell and varies the pumping rate of the suspension through the filter sample. At the end of the test, the mass of sand passed through is weighed on an electronic scale, and the initial and final permeabilities of the original filter and the filter with the settled sand pack are calculated.

At the same time, the known devices for testing sand filters do not have the ability to conduct tests under conditions close to wellbore conditions. The known devices do not have the ability to apply confining pressure (overburden stress - eng.) to the test object. In the proposed technical solution, this drawback is overcome by creating a confining pressure in the test cell, and the tests are carried out at several levels of confining pressure (simulating different depths/conditions for placing the filter in the well).

The main objective of the proposed device is to increase the information content of testing and multiparametric evaluation of a sand filter (key parameters include the permeability of a filter sample with a sand pack, the residual permeability of the filter, the Hodge criterion and the skin factor of a filter with a deposited sand pack), and the quality of the sample evaluation is increased by creating a clamping pressure in the filter test cell.

The device includes a block for preparing an oil-sand mixture, which is fed to the tested sample of the sand filter using a pump. The sand suspension enters the filter sample in the test cell and this causes a layer of sand to settle on the filter. Pressure sensors transmit data on the pressure in the cell to the collection and control block. The amount of sand that has passed and is captured is determined by weighing the samples after the testing device has stopped.

The specified technical result is achieved by creating additional clamping pressure close to the well pressure in a real situation during operation of a sand filter during the formation of a sand pack in a test cell. For this purpose, the sample is loaded using a piston that transmits pressure to the sand pack from a hydraulic pump and a pneumatic hydraulic accumulator (pressure pulsation damper).

Description of figures

Fig. 1 shows a diagram of a device for testing a sand filter sample.

Pump 3, taking the working fluid (for example, technical oil) from the reservoir 1, pumps it along the main pressure line through the tested sample (coupon), installed in the test cell 10. Damper 6 reduces pressure pulsations in the pressure line. In order to maintain a given pressure at the inlet to the test cell 10, pump 3 is capable of automatically changing the speed (flow rate) by switching on via a frequency converter. The system is equipped with pressure sensors 9, 11, 19, transmitting information via the data collection and control unit 26 and has pressure gauges 7 and 20 for monitoring the flows in the device. Shut-off valve 12, located under the test cell 10, allows to shut off the flow of the working fluid, to change the containers on the electronic scales 13, intended for determining the accumulated volume and flow rate of the fluid. To feed the oil-sand mixture (hereinafter referred to as OSM) to the test sample, the mixture components (sand and viscous liquid) are pre-loaded into the OSM preparation tank 14, and when the valve 16 is opened, the mixture (sand suspension in viscous fluid) is fed into the test cell 10, eventually forming a sand pack on the filter sample. Cell 10 is a hollow tube with a conical narrowing at the bottom, no protrusions or steps inside, for the complete exit of the mixture. The viewing window 17 allows visual observation of the movement of OSM particles until complete sedimentation.

After the sand pack is formed, it must be axially compressed (simulating compression/rock pressure), which is done by means of a piston (not shown) of the test cell 10, which transmits the hydraulic fluid pressure from the hydraulic pump 21 through the pneumatic hydraulic accumulator 22, which protects the sand pack from excess pressure during its formation, and also compensates for the pressure drop during the shrinkage of the sand pack. The pressure in the pneumatic hydraulic accumulator 22 is pumped by a pneumatic pump 25 and the pressure is controlled by a pressure gauge 23.

The device is also equipped with pressure sensors 9, 11, 19 and has a data collection and control unit 26, which uses special software for calculating and storing key parameters of the tested sand filter. The transmission of data and control signals is shown in the figure as dotted lines, solid lines show the movement of fluids along the device. The device is also equipped with shut-off and control valves 2, 5, 8, 15, 16, 24, a safety valve 4 and a relief valve 12 for organizing the supply of liquid in the hydraulic system. The set of valves, pressure gauges is further designated for brevity as shut-off and control valves.

Fig. 2 shows a test cell 10, which is a cylinder 30 , inside which a hollow rod 27 moves vertically, having a piston with through channels in the lower part for the outlet of the working fluid and the oil-sand mixture. To hold the rod, as well as to supply the crimping pressure to the above-piston space, an upper nut 28 with a set of seals is used. In the lower part of the cell, hermetically to its body, the tested sample (in a special shell) 32 is installed, which is held in the desired position by the lower nut 31. From above the cell through the hollow rod 27, a pressure line is introduced, and through the side opening of the upper nut 28, a crimping line 29 is introduced (creates crimping pressure). The crimping line 29 is fed from the pump 21 and the hydraulic accumulator 22 through the pressure gauge 20 and the shut-off valve 18 (see Fig. 1).

All data received from pressure sensors, readings from electronic scales when weighing the sand that has passed through, and the pump control unit are collected by the controller of the data collection and control unit 26 to calculate several evaluation parameters using special software.

Operating procedure of the sand filter testing device.

The sand filter testing device includes a unit for preparing an oil-sand mixture, which is fed via a pump through a damper to the sand filter sample being tested.

In the context of this invention, the oil fluid is selected for the purpose of improved dispersion of sand particles in the fluid. Instead of technical oil, it is possible to use mixtures of organic solvents, water-polymer solutions and other fluids that create a dispersion of sand particles during testing.

When the main pump 3 is switched on, the working fluid enters the test cell 10. The pressure difference in the test cell creates a suspension flow and causes sedimentation of a layer of a larger sand fraction on the filter (formation of a sand pack on the filter). In this case, through the crimping line 29 through the upper nut 28, a crimping pressure is created, which imitates the real total pressure of the overlying rocks. When testing a sample in the test cell 10, the pressure history is recorded and the history is saved in the control unit 26. The passed sand-oil mixture (SOM) is collected in a container and after filtration, the mass of the passed particles is calculated (Hodge criterion). Also, using optical methods (for example, laser granulometric analysis), the maximum size of the produced sand particles (particle fraction d10) is subsequently measured.

After a specified period of time, a sand pack accumulates on the sand filter sample, the filter permeability decreases, and the pumping of the working fluid (sand-oil mixture) stops. After depressurization of cell 10, a sand filter sample is removed from the test cell through the discharge valve 12 and the contaminated filter is weighed to determine the mass of particles deposited on the filter.

The obtained data are entered into the data collection and control unit 26 and the parameters for the multifactorial assessment of the sand filter are calculated: this is the Hodge criterion, the permeability of the filter with a sand pack, the residual permeability of the filter, the maximum size of the produced particles, the skin factor of the filter with a sand pack.

This procedure is then repeated for other sand filter samples and those filters with parameters that satisfy the restrictive criteria from Table 1 are selected.

Example

The testing device with the described configuration allows for a comprehensive assessment of the filter's applicability to a specific well with an existing rock core (sand source) and at a given value of the confining pressure. The set of evaluation parameters is given in Table 1.

Table 1.

Parameter Parameter Description Recommended parameter value Hodge criterion The total mass of sand particles that passed through the filter Not more than 0.41 g from a sample with a diameter of 30 mm (or 0.12 lb/ft2) Permeability of a filter with a sand pack Permeability of the sample after the formation of the sand pack - Residual permeability of the filter Permeability of the sample after removal of the sand pack Not less than 50% Maximum size of particles produced Particle size passing through the filter (fraction d10) Not more than 50 microns Skin factor of a filter with a sand pack Evaluation of the ratio of the permeability of the colmatated filter to the permeability in the formation Less than 1 (<+1)

In this case, the skin factor of the filter + sand pack system is described by the formula

where k _r is the formation permeability, k _g is the filter permeability, r _w is the radius of the open wellbore, H is the filter height, r _is = r _w - H. The skin factor S _g according to the criteria for selecting filter samples should be less than + 1.

The filter permeability is calculated using Darcy's formula:

where K is the permeability (mD), μ is the viscosity (cP), L is the height of the filter part (cm), Q is the volumetric flow rate ( ^cm3 /sec), ΔP is the pressure drop (atm), A is the sample area ( ^cm2 ).

Table 2 shows the evaluation parameters for testing the multilayer filter. The tests were carried out at four levels of confining pressure.

Table 2.

Crimping pressure, atm Permeability of the original filter, mD Permeability of dirty filter, mD Permeability of filter with pack, mD Skin factor 0 200750 141151 11000 0.03 27.6 200750 141151 9043 0.037 55.2 200750 141151 5113 0.063 82.7 200750 141151 2081 0.148

As can be seen from the table data provided, the absence of a clamping pressure in the cell (i.e., as in known filter testing devices) leads to a distortion of the estimated parameters (in particular, the skin factor and permeability of the filter with a pack), which can lead to an erroneous choice of the type of sand filter, and this will negatively affect the well flow rate and the serviceability of the equipment (especially pumps).

Table 3.

Parameter Test results
filters 1 Test results
filters 2 Hodge criterion 0.01 g 0.017 g Permeability of a filter with a sand pack 26.2 mD 19.1 mD Residual permeability of the filter 49% 80% Maximum size of particles produced 150 microns 35 microns Skin factor of a filter with a sand pack 0.154 0.195

As can be seen from Table 3 (evaluation of two types of sand filter by several parameters), the described device allows to evaluate the suitability of a sand filter under specific well conditions. In this case, filter 2 successfully passed the tests by all the specified criteria, while filter 1 failed the tests: an unsatisfactory result was obtained by two parameters (residual permeability of the filter and the maximum size of the produced particles).

The foregoing description has been presented in the form of embodiments. Those skilled in the art to which the present invention pertains will appreciate that modifications and changes in the described structures may be practiced without substantially departing from the principle and scope of the present invention. Accordingly, the above description should not be considered as referring only to the specific structures described and shown in the accompanying drawings, but should be considered in accordance with the appended claims.

Claims (3)

1. A device for testing a borehole sand filter for several parameters, including a main pump for pumping a mixture and creating pressure, connected to a unit for preparing an oil-sand mixture, a test cell connected to the unit for preparing the sand-oil mixture with a sample of the sand filter installed in it for settling a sand pack, pressure and crimping lines connected to the test cell, pressure sensors and pressure gauges, shut-off and control valves, a container for collecting the oil-sand mixture that has passed through the sand filter, electronic scales, a data collection and control unit configured to receive data from the pressure sensors, the electronic scales, the main pump control unit, wherein the test cell is configured to create a crimping pressure in it using a piston that transmits pressure to the sand pack from a hydraulic pump connected to a pneumatic hydraulic accumulator. 2. The device according to item 1, characterized in that the test cell includes a cell body in the form of a pipe with a conical narrowing in the lower part, a lower nut for placing a sample of the sand filter, and an upper nut for supplying injection and clamping pressure. 3. The device according to item 1, characterized in that the data collection and control unit is designed with the possibility of calculating the permeability of a filter sample with a sand pack, the residual permeability of the filter, the Hodge criterion, and the skin factor of the filter with a deposited sand pack.