RU2410528C1 - Method of protection against sand phenomena in well - Google Patents

Abstract

FIELD: oil and gas industry. ^ SUBSTANCE: invention refers to oil industry and can be used during production of fluid for protection against sand phenomenon in wells drilled from the surface. Method involves lowering of casing pipe and it's cementing to the head, lowering of perforated shank or filters to the well in the effective pay section with further lowering of process string to the bottom hole. Pump equipment is lowered parallel to process string. Perforation holes are made in process string prior to lowering to the well at its location place in effective pay section throughout the length of effective pay. Plug is installed on the end of the string. Flushing fluid is pumped to process string in cycles at operating oil producing pump equipment. ^ EFFECT: reducing the time and costs for underground repair regarding prevention of sand phenomenon. ^ 2 cl, 2 dwg, 1 tbl

Description

The invention relates to the oil industry and can be used in the production of liquids for sand control in wells drilled from the surface.

Known methods of dealing with sand in the well by blocking the bottom of the producing well with filters or fixing weakly cemented rocks to the bottom of the well with plastics, resins, etc. (The book is under the general editorship of Prof. I.M. Muraviev "Development and operation of oil and gas fields", Nedra Publishing House, Moscow, 1965, pp. 158-159).

However, when producing highly viscous oil using thermal methods, as well as as a result of various methods of increasing oil recovery, for example, injecting solvents, carrying out acid treatments of the bottom-hole formation zone and other methods, the binders break down the substances, resulting in a large amount of oil entering the well the amount of sand, which leads to clogging of the filters, as well as the formation of sand plugs in the production wells that stop the flow of oil.

Also known is a method of controlling sand manifestation in a well, according to which, during oil production, the deep well pump of the producing well is equipped with a gas sand separator with a sand trap (AS USSR No. 1760099, ЕВВ 43/38 from 08/10/1989).

The disadvantage of this method is that with the active destruction of weakly cemented seams, the sand trap is quickly clogged by the products of the destruction of the reservoir, which complicates the operation of the deep pump and necessitates the raising of the sand trap to the surface for cleaning. As a rule, due to the limited size of the sand trap, its clogging occurs more often than the overhaul period of the pump, resulting in a decrease in oil production in the reservoir.

Other known methods of controlling sand in a well include shutting the well, raising the downhole pumping equipment to the surface, lowering the flushing or cleaning tool, and repairing the well.

A known method of dealing with sand in wells by cleaning sand plugs using brooms (Book "Technology and Technique for Oil and Gas Production", Muravyev IM, Bazlov MN and others, publishing house "Nedra", 1971 p. 457).

However, cleaning wells from sand plugs with the help of baulks requires considerable time for hoisting operations and, in addition, the perforation holes of the filter are rolled when the bailer passes through the borehole during hoisting operations, which leads to a decrease in the filter duty cycle. For horizontal wells, with a large length, breakage of the tool is possible.

Another well-known method of dealing with sand in a well involves the introduction of a flexible tubing into a cemented casing, ending with a perforated liner or filter, pumping washing fluid into the tubing to flush the sand plug with a jet of washing fluid through the nozzle at the end of the tubing. After liquidation of the sand plug, the production string is removed and the well is put into operation (article “Technologies for cleaning the bottom of the well from sand using a coiled tubing installation. / V.A. Vasiliev, V.E. Dubenko and others, OJSC SevKavNIPIgaz, Stavropol // Materials of the first all-Russian correspondence conference “Problems of increasing gas and oil recovery at the final stage of their development and operation”, North Caucasus State Technical University, 2005).

The disadvantage of this method is the need to extract deep pumping equipment in the case of pumping wells and, as a result, the cessation of oil production during the elimination of sand plugs, as well as the significant cost of time and money for operations to eliminate sand plugs due to the duration of the hoisting operations.

There is also a known method of dealing with sand occurrence in a well, adopted by the authors for a prototype, including lowering the casing string and cementing it to the wellhead, lowering the perforated liner or filter into the well at the section of the productive part of the formation, followed by lowering the process column into which the drilling fluid or other working agent. The method is used in horizontal wells drilled from the surface. As a technological column use a flexible tubing (tubing). The washing of the sand plug is carried out by a jet of washing liquid through a nozzle at the end of the tubing. The flexible tubing is periodically admitted to the length of the cleaned horizontal interval of the well until the sand plug is completely eliminated, then the production string is removed and the well is put into operation (RF patent No. 2156007, ЕВВ 37/00 dated 05/25/1999).

The disadvantage of this method is the need to extract deep pumping equipment in the case of pumping wells and, as a result, the cessation of oil production during the elimination of sand congestion. At the same time, the need for periodic admission of a flexible tubing lowered into the well, that is, increasing its length as the sand plug breaks along the length of the horizontal section, as well as the subsequent removal of the process column to the surface for putting the well into operation, increases the time for underground repairs and, accordingly, the time to stop oil production.

The present invention is to increase oil production by reducing the time and cost of underground repairs to prevent the formation of sand jams.

The task is achieved in that in order to combat sand formation in the well, the casing is lowered and cemented to the wellhead, lowered into the well at the site of the productive part of the formation of the perforated liner or filters, followed by the descent of the process column into which the drilling fluid is pumped.

Salient features of the claimed invention are:

- additionally parallel to the production string pumping equipment is lowered into the well;

- the casing is lowered to the bottom of the well;

- before lowering into the well in the production string at its location on the site of the reservoir, perforations are made;

- a plug is installed at the end of the process column;

- the injection of washing liquid into the process column is carried out cyclically with pumping equipment operating for oil production;

- the beginning of each cycle of pumping washing fluid into the process column is determined by reaching the amount of suspended particles in the produced product as specified in the passport data of the pumping equipment.

The specified set of essential features provides an increase in oil production due to the reduction of time and costs for underground repairs to prevent the formation of sand plugs, namely: the constant presence of the process column in the well will allow for cyclic pumping of flushing fluid during operation of the pumping equipment during the entire period of operation of the well . Lowering the production casing to the bottom of the well, making holes along the length of the casing at its location in the reservoir, installing a plug at the end of the casing, cyclic short-term supply of flushing fluid to the casing during operation of pumping equipment for oil production creates favorable conditions to prevent sanding of the well . Wash fluid, such as formation fluid, is supplied under pressure in volumes equal to one to two volumes of the well section located in the reservoir. The flushing fluid through the perforation holes enters the well, agitating the deposited sand, while the pumping equipment does not stop and the resulting emulsion (fluid and solids) is pumped to the surface. The movement of the emulsion along the perforated section of the well is provided by the depression created by the pumping equipment, and pumping to the surface is provided by the pressure created by the pumping equipment. In the proposed method, the formation energy (reservoir pressure) is not used for supplying the emulsion to the surface; therefore, the method can be used in formations with an abnormally low pressure. The pressure of the flushing fluid at the outlet from the openings along the length of the process column located in the reservoir must be higher than the reservoir pressure to ensure its entry into the well. Due to the pressure of the flushing fluid, the perforation holes of the liner or well filters and directly the bottom-hole zone of the formation are also washed, resulting in increased well productivity.

Thus, the proposed method does not require additional tripping operations and the cost of paying for human labor and equipment for underground repair of wells to eliminate sand plugs, which significantly reduces the cost of sand control and reduces its time, underground repair of wells is carried out without stopping the process oil production, the method is applicable for repairing wells in conditions of abnormally low reservoir pressure.

The claimed combination of essential features is not known to us from the prior art, therefore, the claimed invention is new. The claimed features of the invention are not obvious to the average person skilled in the art. In this regard, we believe that the claimed invention has an inventive level. The invention is industrially applicable since the available equipment and technology developed by us, allow us to fully implement the method.

Figure 1 presents the design diagram of a horizontal well for implementing the method.

Figure 2 presents a design diagram of a vertical well for implementing the method.

The method is as follows. The casing 2 is lowered into the production well 1 drilled from the surface and cemented to the wellhead to form cement stone 3. At the site of the productive formation, the well is equipped with a perforated liner or filters 4. A production casing 5 is lowered into the prepared well to stay there continuously for the entire period well operation. Then pumping equipment 6 for oil production is lowered into the well, for example, an electric centrifugal pump. As a process string, for example, a tubing string can be used. Before launching into the well in the production string 5 at its location in the area of the productive formation, where sand enters from the formation into the well, perforations 7 are made. The channels of the holes can be made perpendicular to the axis of the column, but can be made with an inclination in the direction of the pump equipment or alternate with each other in order to activate the flow of flushing fluid and moving sand in the direction of the pumping equipment. At the end of the casing, plug 8 is installed. The pressure at the outlet of the perforation holes of the casing is calculated according to the laws of hydraulics (Bernoulli equation) taking into account hydraulic friction and exit from the holes. The density of the perforations along the length of the casing is determined on the basis of hydraulic calculation, provided that the flow of flushing fluid from the casing into the well is uniform. Perforation holes in the process column are, for example, of the same size with different densities along the length of the column in proportion to the pressure of the liquid in the column, that is, the density of holes per unit length of the process column is increased from the beginning to the end of the column or of different sizes with the same density in proportion to the pressure of the liquid in the column , that is, the area of their outlet cross-section is increased towards the end of the column, which ensures uniform flow of flushing fluid from the process column into the well. An increase in the density of perforation holes in the production string at the intersection of cracks or tectonic disturbances creates the most favorable conditions in these sections of the well for agitating sand entering the well in a larger volume.

To prevent the formation of sand plugs in the well 1, washing fluid is cyclically pumped into the production column 5, which, exiting under pressure from the perforations 7, winds up the sand deposited in the well with a powerful jet, and the plug installed at the end of the production column prevents the washing liquid from leaving the column without breaking layer of settled sand. Sand in an agitated state is transferred by flushing and formation fluid to the receiving module of the working pumping equipment 6 and is pumped to the surface. As the washing fluid pumped into the process column, formation fluid and / or surfactant and / or water and / or washing foam are used. The type of flushing fluid, the frequency of its injection, and the injection parameters are determined empirically, as well as depending on both the current state of the well performance indicators and the design features of the available surface and underground equipment. The main parameter that determines the cycles and volumes of the pumped liquid is: an indicator of the amount of suspended particles (EHF) in the pumped product, the values of which should not exceed the values specified in the passport data of the pumping equipment. Flushing fluid can be injected both from a single accumulating technological capacity for the entire group of wells in the plot when tying technological columns of wells with one collector, and from an individual accumulating capacity for the technological column of one well. To ensure the same flow rate of flushing fluid along the length of the process string through the holes and, accordingly, to ensure uniform erosion of sand deposits, a program for calculating the number of holes along the length of the process string has been developed, which allows quick calculations for wells of various lengths. The calculation condition is that the fluid flow rate in the perforated section of the process column must be the same. Therefore, the density of the holes in the casing can be variable for the same size of the holes or constant for different sizes of holes. It is desirable that the maximum dimensions of the perforations do not exceed the average particle size distribution of sandstone to prevent sanding of the process column itself. If the size is exceeded, it will be necessary to increase the frequency of injection of flushing fluid. The choice of the type of perforations depends on the technical capabilities of the enterprise performing this work.

Example. The claimed method can be implemented on the Yaregskoye field of high viscosity oil at the OPU-3 site. The oil reservoir lies at a depth of 180-200 m from the surface.

Three pairs of horizontal wells with a horizontal well of 300 m were drilled on an OPU-3 area with an area of 63 thousand m ^2. The development of the section is carried out by the technology of thermogravitational drainage of the formation, in which the horizontal wells of each pair of wells are located in one vertical plane, while the upper well is injection, and the bottom is mining. The formation is terrigenous, interbedded by mudstone interlayers, which are washed out by the filtering fluid during the development process, and the fracture products are transferred to the producing well, which leads to the calcination of the bottom of the formation and lower permeability. The OPU-3 section is located in mine areas previously worked out by the mine method in natural mode with a dense grid of underground wells drilled from mine workings. This led to almost complete depletion of reservoir energy and the pressure in the roof of the reservoir decreased to 0.1 MPa. Underground repair of wells in these conditions using flushing or purging is almost impossible, since the flushing agent is absorbed by the formation. As a result, well repair is carried out using gelation, which requires a lot of time for work.

The design of the producing well is as follows:

- inner diameter before the start of the horizontal section - 227 mm;

- inner diameter of the filter-liner in the horizontal section of the well - 160 mm;

- diameter of the body of the electric centrifugal pump - 100 mm;

- the pump is placed before the beginning of the horizontal section of the well (in front of the filter-liner).

The design of the well allows you to lower the production string into it, for example, a tubing string with an outer diameter of 50 mm and an inner diameter of 40 mm.

The average particle size distribution of the sandstone is 0.6 mm. Therefore, we accept perforation holes in a round column with a diameter of 0.5 mm. The specified diameter reduces the likelihood of sand from the well into the casing. The length of the technological column section is 8 m. For example, water is used as a washing liquid. The density of the perforations along the length of the casing is determined on the basis of hydraulic calculation, provided that the flow rate of flushing fluid, such as water from the casing into the well, is uniform. The excess pressure of water flow above the pressure in the well (reservoir) at the end of the production string is 0.2 MPa. The water injection pressure at the mouth of the process column is 0.6 MPa. The results of calculating the density of the holes along the length of the horizontal part of the casing for the wells of the OPU-3 section are given below.

INITIAL DATA

Flushing fluid water Flushing fluid temperature 20 ° C Vertical well depth 200.0 m Well curvature radius 90.0 m The length of the horizontal part of the well 300.0 m Bore diameter 0.139 m The inner diameter of the process column 0.040 m The outer diameter of the process column 0.050 m Length of casing section 8.0 m The diameter of the holes of the technological column 0.500 mm Equivalent pipe roughness 0.200 mm Wash Fluid Density 998.3 kg / m ³ Wash Fluid Viscosity 1003.0 μPa · s Wellhead injection pressure 0.600 MPa Horizontal Well Pressure 0.100 MPa Maximum pressure at the end of the process string 0.300 MPa Minimum pressure at the end of the process string 0.290 MPa

CALCULATION RESULTS

Water flow through a technical column at the mouth of 18.83 m ³ / h

To flush the well, it is enough to pump water in a volume equal to one volume of the horizontal section of the well, which is

where d is the internal diameter of the well, L is the length of the horizontal section of the well.

The time for water injection in one volume of the horizontal wellbore will be

The time it takes to repair a well is hundreds of times less than when repairing in a traditional way.

With pressure drops along the length of the horizontal section for the considered example from 0.934 MPa to 0.299 MPa, the velocity of the fluid through the perforations is 10-25 m / s. A stream of water ejected from the perforations with such a speed not only easily agitates the deposited sand, but also easily flushes the perforations of the liner or well filters and directly the bottomhole formation zone, as a result of which the well productivity is significantly increased. Given that the installed electric centrifugal pump according to the passport data works with an indicator of the amount of suspended particles (EHF) in the produced products of 100 mg / l, it is advisable to establish the cyclicality of the injection of washing fluid into the process column when the EHF value is 70 mg / l.

Thus, the proposed method does not require additional tripping and costs for underground repair of wells to eliminate sand plugs, which significantly reduces the cost of sand control and reduces the time it takes, underground repair of wells is carried out without stopping the oil production process, while applicable for well repair in conditions of abnormally low reservoir pressure.

Claims (2)

1. A method of controlling sand manifestation in a well, including lowering the casing string and cementing it to the wellhead, lowering the perforated liner or filters into the well at the site of the productive part of the formation, followed by lowering the process column into which the drilling fluid is pumped, characterized in that it is in the well in addition, pumping equipment is lowered parallel to the production casing, the production casing is lowered to the bottom of the well, while before descending into the well in the production casing Once it is located in the area of the productive formation, perforations are made, and a plug is installed at the end of the column, the washing liquid is pumped into the process column cyclically with pumping equipment operating for oil production. 2. The method according to claim 1, characterized in that the beginning of each cycle of pumping the washing liquid into the process column is determined upon reaching the amount of suspended particles in the produced product as specified in the passport data of the pumping equipment.

Images