EA044688B1 - SYSTEM AND METHOD FOR CONTROLLING THE CONDITION OF THE CRUSH OF THE BORE-THE-BORE-THE-ZONE IN THE HOLE OF A SUBSURFACE WELL - Google Patents

Description

Links to related applications

This application claims the priority of European patent application EP 19187146, filed on July 18, 2019, entitled Systems and methods for controlling the condition of the bottom-hole zone cake in a subsurface wellbore, and European patent application EP 19187148, filed on July 18, 2019, entitled Systems and methods controlling the condition of the near-wellbore zone crust in a subsurface wellbore, the entire contents of which are incorporated herein by reference.

Field of technology

The invention generally relates to systems and methods for producing hydrocarbons from a subsurface reservoir. In particular, the present disclosure relates to systems and methods for regulating or controlling the condition of a near-wellbore cake in a gravel pack wellbore extending within a subsurface reservoir.

State of the art

To obtain hydrocarbons from subsurface reservoirs, a wellbore is drilled into the oil and gas reservoir (also called the pay zone herein) to access it. After drilling the wellbore to the required depth, a pumping (lift) string is installed into it to extract hydrocarbons from the productive zone to the surface. To prevent the free migration of fine solids, generally referred to herein as fines, from the production zone, along with any produced hydrocarbons, into the well completion and production equipment, a filter (or several filters). In addition, a proppant of the desired size, such as sand or other solids, generally referred to herein as gravel pack, is placed in the well. In particular, the gravel pack is located within the reservoir as well as in an annulus located radially outside the screen (eg, an annulus located radially between the screen and the perforated casing or wellbore wall). When placed in this manner, the gravel pack forms a barrier that filters fine particles from the produced fluids so that these particles are prevented from passing through the filters and escaping to the surface. This type of well completion is commonly referred to as a gravel pack completion. When a gravel pack completion is performed inside an open hole, it may be referred to as an open hole gravel pack completion, and when a gravel pack completion is performed in a cased or cased hole, the completion may be referred to as a gravel pack completion. cased bottom filters.

The essence of the invention

Some embodiments disclosed herein relate to a method for controlling the condition of a near-wellbore cake in a subsurface wellbore. In an embodiment of the method, oscillatory changes in the bottomhole pressure drop are created in the wellbore of the subsurface zone with a given law (pattern), including a plurality of alternating increases in the bottomhole pressure drop and decreases in the bottomhole pressure drop. An increase in the bottomhole pressure difference according to a given law includes an increase in the bottom hole pressure difference with the first speed, and a decrease in the bottom hole pressure difference according to a given law includes a decrease in the bottom hole pressure difference with a second speed that differs from the first speed.

Other embodiments disclosed herein relate to a system for producing hydrocarbons from a wellbore in a subsurface zone. In an embodiment, the system includes a tubing string installed inside a wellbore. In addition, the system includes a production (choke) valve in fluid communication with the tubing string so that formation fluids passing into the wellbore enter through the tubing string into the production valve. In addition, the system has a controller connected to the service valve. The controller is configured to selectively actuate the production valve to: create oscillations of the bottomhole pressure drop in the wellbore according to a given law, including a plurality of alternating increases in bottomhole pressure drops and decreases in bottomhole pressure drops. Increases in bottomhole pressure drops according to a given law include increases in bottomhole pressure drops at the first speed, and decreases in bottomhole pressure drops according to a given law include decreases in bottomhole pressure drops at a second speed different from the first speed.

Other disclosed embodiments are associated with non-transitory computer readable media. In an embodiment, a non-volatile computer-readable medium (environment) contains programs that, when executed by a processor, cause the processor to activate a production valve to create oscillations of the bottomhole pressure differential in the wellbore in the subsurface zone in accordance with a given law, including a plurality of alternating increases in bottomhole pressure differentials and reducing bottomhole pressure drops. Increasing differences

- 1 044688 bottomhole pressure according to a given law include increases in bottomhole pressure differences with the first speed, and decreases in bottomhole pressure differences according to a given law include decreases in bottomhole pressure differences with a second speed different from the first speed.

The programs, when executed by the processor, may also cause the processor to actuate the production valve to create a patterned oscillation of the bottomhole pressure differential around a first specified target value; and further, to actuating the production valve to create oscillations of the bottom hole pressure drop according to a second predetermined law around a second predetermined target value different from the first predetermined target value.

The embodiments described in the present disclosure contain a combination of features and characteristics designed to overcome various disadvantages associated with certain devices, systems and methods known in the art. The features and technical characteristics of the disclosed embodiments described above will provide a better understanding of the detailed description that follows. The various technical characteristics and features described above, as well as others, will be apparent to one skilled in the art upon reading the following detailed description and the accompanying drawings for reference. It should be understood that the concept and specific embodiments disclosed can readily be used as a basis for modifying or developing other designs to accomplish the same objectives as the disclosed embodiments. It should also be understood that such equivalent interpretations do not go beyond the substance and scope of the principles disclosed here.

Brief description of drawings

For a detailed description of various particular embodiments, reference will be made to the accompanying drawings, in which:

in fig. 1 is a schematic cross-sectional view of a system for producing formation fluids from a subsurface reservoir, in accordance with the described embodiments;

in fig. 2 is an enlarged cross-sectional view of the gravel pack from the image in FIG. 1;

in fig. 3 is a graph illustrating the variation of bottomhole pressure drop for a subsurface wellbore in accordance with the described embodiments;

in fig. 4 is a graph illustrating another variation of bottom hole pressure drop for a subsurface wellbore;

in fig. 5 is a graph illustrating another variation of bottom hole pressure drop for a subsurface wellbore;

in fig. 6 and 7 are block diagrams illustrating embodiments of methods for controlling the state of the bottomhole zone in a subsurface wellbore in accordance with the described principles;

in fig. Figure 8 shows a graph of the bottomhole pressure drop as a function of time, in accordance with the example discussed below;

in fig. 9 is a combined plot of mass flow and hydrostatic pressure as a function of time for the experiment described in Example 2 discussed below; and in fig. 10(a)-10(m) show photographs of a cone cell containing gravel pack and fine particles during the experiment described in Example 2 below.

Detailed Description of the Invention

The following discussion relates to various particular embodiments. One skilled in the art will, however, appreciate that the examples disclosed herein are broad in application and that the discussion of any embodiment is illustrative of an example embodiment only and should not be intended to limit the scope of the disclosure, including the claims, to that embodiment.

Drawings in the figures are not necessarily to scale. Some features and components may be shown in exaggerated or somewhat diagrammatic form, and some details of common features may not be shown in the interests of clarity and brevity.

In the discussion and formula below, the use of the terms including and containing is not intended to be limiting, and should therefore be taken to be inclusive, but not reducible to.... Moreover, the term connect or connect implies the inclusion of an indirect or direct connection between the elements described. That is, if a first device is connected to a second device, the connection may be through a direct connection of the two devices, or through an indirect connection through other devices, components or connections. Additionally, as used herein, the terms axial and axial generally mean a direction along or parallel to a given axis (eg, the central axis of a housing or opening), while the terms radial and radial generally mean a direction perpendicular to a central axis. For example, axial distance means a distance measured along or parallel to an axis, and radial distance means a distance measured perpendicular to a central axis. As used herein, the term formation fluids refers to liquids and gases produced from

- 2 044688 subsurface productive formations into a well or other connecting channel. For example, the term may include oil, hydrocarbon gases, water, condensate, etc. As used herein, the terms approximately, approximately, substantially, generally, etc. mean that the value is within the range of plus or minus 20% of the stated value unless specifically stated otherwise.

As mentioned above, gravel pack completions (including both open hole and casing) involve introducing a gravel pack into the annulus adjacent to one or more screens (eg, tubular screens) within the wellbore. The injected gravel pack provides filtration of fines that may be produced from the subsurface reservoir along with other formation fluids (e.g. oil, gas, condensate, water, etc.) and therefore limits and/or prevents the passage of fines to the surface . However, during production, fines can collect within the gravel pack and form a crust in the near-wellbore zone, which restricts the flow of formation fluids through the gravel pack. In some cases, formation of a near-wellbore crust may ultimately prevent the recovery of a significant portion of the formation fluids. To reduce the crust in the near-wellbore zone, some remedial measures can be taken. One such remedial measure may be so-called acidizing, which involves injecting a stream of acid into the subsurface well to dissolve the particles that form the bottom-hole crust. However, the use of acidizing is typically costly and can result in increased corrosion and wear of components inside the well. Moreover, the benefits gained from acidizing may be short-lived as new fines will continue to flow from the formation after the acidizing is completed.

Accordingly, embodiments disclosed herein include systems and methods for controlling the condition of a near-wellbore cake within a subsurface wellbore by controlling and selectively adjusting the bottomhole pressure differential over time to inhibit formation of a near-wellbore cake. In particular, embodiments disclosed herein include causing controlled oscillations (eg, alternating increases and decreases) of a bottomhole pressure differential within a subsurface well to inhibit formation of cake and possibly remove or reduce cake already formed within the gravel pack. Thus, through the use of the systems and methods described herein, an operator can reduce or possibly eliminate the need for relatively expensive and potentially harmful acid treatment within a subsurface well.

While the specific embodiments described herein provide for the controlled and selective generation of oscillations of bottomhole pressure differentials within the wellbore of a gravel pack well (i.e., an open hole or cased hole completed using gravel packs as described above), It should be kept in mind that these systems and methods (eg, bottom hole pressure drop variations described below) may be used with other types of well completions (ie, other than gravel pack completions). For example, in some embodiments, the pressure fluctuations described below can be used during a completion using a so-called stand-alone sand screen, where fluids flow from the reservoir directly into the well screen (or multiple screens) without an intermediate layer of gravel pack (as occurs in in case of completion using gravel packs). In such a completion, a near-wellbore crust (for example, from fine particles of the reservoir) can form inside the formation or along the filter itself. Without being bound by any particular theory, it is believed that the application of the bottomhole pressure differential variations described below can prevent or reduce cake formation in a self-contained filter completion in generally the same manner as in the particular case of a gravel pack completion described below.

In the present disclosure, the term bottomhole pressure drop refers to the difference between the pressure of a subsurface reservoir and the pressure of the wellbore passing through the formation (sometimes also called drawdown). In order for produced fluids to enter the well to be brought to the surface, the bottomhole pressure differential is set so that the pressure inside the well is generally less than the formation pressure. In this case, the difference in bottomhole pressure causes formation fluids to move from the subsurface productive formation into the well during the production process, and it would be natural to assume that the difference in bottomhole pressure is directly proportional to the flow rate of well products in the well. Accordingly, with an increase in the bottomhole pressure drop (i.e., with an increase in the difference between the pressure of the formation and the well), the flow of well production into the well from the productive formation should also increase. As shown in the present disclosure, bottom hole pressure differential can control the operation of production valves or other surface pressure control devices.

In fig. 1 shows a system 10 for producing formation fluids from a subsurface reservoir 6. The system 10 generally includes equipment 12 located at the surface

- 3 044688 (therefore equipment 12 may be referred to as surface equipment), and a wellbore 20 extending from surface 4 into the subsurface reservoir 6 along a central or longitudinal axis 15. FIG. 1, axis 15 is shown as a generally straight line, however, it should be borne in mind that in other embodiments, axis 15 may be non-linear (for example, subsurface well 20 is rarely strictly straight and may deviate under the influence of various factors). In addition, while the wellbore is shown vertical, it should be understood that in other embodiments it may include one or more horizontal or substantially horizontal sections or portions. Thus, the depiction of the linear, vertical axis 15 of the wellbore 20 in the drawings is used to simplify the present description and should not be taken as limiting possible deviations or variations of the wellbore 20 in other embodiments.

Typically, surface equipment 12 may include any suitable equipment to enable production of formation fluids from reservoir 6 through well 20, such as a production valve assembly (eg, a Christmas tree assembly). Surface equipment 12 includes, or is connected to, a production valve 14 configured to control the flow of formation fluids from the well 20 to the flow line or pipe 16. The pipe 16 delivers the well product to a destination 18, which may be a pipeline, a reservoir, or a reservoir. storage, processing facility, or other suitable destination for formation fluids exiting well 20. In addition, surface equipment 12 may include electronic control equipment (e.g., controller 400, described in more detail below) to regulate or control the operation of various components and functions in the system 10. Electronic control equipment (eg, controller 400) may be located within a local control room (not shown) of the system 10 or at any suitable location (including, for example, a position remote from the wellbore 20).

The casing 22 or its internal workover pipe extends axially from or near the surface 4 (eg, surface equipment 12) into the wellbore 20. The casing 22 is the support structure of the well 20 and prevents the passage of formation fluids into the wellbore 20 at uncontrolled locations or depths. The casing 22 is secured within the wellbore 20 by cement or any other mechanism or material. Specifically, the casing 22 has a first or upper end 22a located on or near surface 4 and a second or lower end 22b located in the wellbore 20.

A tubing string (tubing) 26 is also inserted into the wellbore 20 inside the casing 22. The tubing 26 transfers formation fluids coming from the productive formation 6 to the surface 4, from where they are further transmitted through the production valve 14 and the flow valve pipe 16 to destination 18, as shown above. The tubing 26 has a first or upper end 26a located on or near surface 4 and a second or lower end 26b located in the wellbore 20. The lower end 26b of the tubing string 26 may be positioned above or below the lower end 22b of the casing 22 and, in some embodiments, the lower end 26b of the tubing 26 may be positioned coaxially (or substantially coaxially) with the lower end 22b of the casing 22. Towards the lower end 26b of tubing 26 is connected to a collecting filter 30 extending from it along the axis. The collection filter 30 includes one or more filters (not specifically shown in FIG. 1) for filtering formation fluids emanating from the reservoir 6 during the production process.

In fig. 1 also shows an annulus or annular space 31 between the collection screen 30 and the sidewall 8 of the wellbore below the lower end 22b of the casing 22, filled with gravel pack 36. In the annulus 24 between the tubing 26 and the casing 22 at or near the lower ends 22b, 26b A packer or end seal 28 is installed therein to create a fluid seal between the annulus 31 and the annulus 24 and thereby prevent fluid or gravel from flowing axially upward toward the surface 4 through the annulus 24 during operation. Thus, as formation fluids pass from the sidewall 8 of the wellbore, they are directed through the gravel pack 36 and the collecting screen 30 so that the formation fluids can then move up the tubing 26 to the surface 4.

In fig. 2 shows how, as formation fluids flow through gravel pack 36 and collection filter 30 as described above, fines particles 32 carried by formation fluids from reservoir 6 can become trapped between particles 34 forming gravel pack 36. Over time. , trapped fines particles 32 accumulate within the gravel pack 36 and can form a cake that limits the possible passage paths 33 for formation fluid flow between the particles 34 of the gravel pack 36 and through the perforations 38 in the collection filter 30. Accordingly, as the number of fines particles increases fractions 32 retained or settled within the gravel filter 36, the flow of formation fluids into the collecting filter 30 and further into the tubing 26 drops. Eventually, the flow of formation fluids may become so low that restoration work is required, or stops well operation.

- 4 044688

Returning to FIG. 1, it may be noted that to prevent or retard the formation of bottomhole crust in the gravel pack 36, controlled adjustment of the bottomhole pressure differential may be periodically performed according to the method described herein. In the present embodiment, a pressure sensor 13 (or multiple sensors) is installed or inserted to monitor the pressure inside the wellbore 20. Additional pressure sensors may be used to measure the pressure within the reservoir 6 (and/or this value may be determined using other factors, parameters or measurements). In this way, monitoring of the difference in bottomhole pressure during operation can be carried out by the pressure sensor 13 and/or additional data or measurements. The pressure sensor 13 is connected with the ability to transmit signals with the surface 4 (in particular, with the controller 400) via a communication line 17. In general, communication line 17 can be any wired or wireless communication line. For example, in some cases, communication line 17 may include a conductive wire (eg, electrical wire, fiber optic cable, etc.). In other cases, communication link 17 may be a wireless communication link (eg, acoustic communication, radio frequency (RF) communication, infrared communication, etc.).

During operation, the production valve 14 is controlled to be activated (for example, by the controller 400 in some embodiments) to regulate the flow of formation fluids into the flow pipe 16, and, as a result, the bottomhole pressure drop within the wellbore 20. In other embodiments, other pressure control mechanisms in addition to, or instead of, the production valve 14 may be used to control or regulate the bottomhole pressure differential within the wellbore 20. For example, in some embodiments, a backpressure pump may be included in the system 10 to apply backpressure to the wellbore 20 to thereby regulate the bottomhole pressure differential within the wellbore 20 during operation.

Because the gravel pack 36 is located within an area or zone of the wellbore 20 that does not have casing or internal pipe (eg, casing 22), the gravel pack 36 will be an open gravel pack. It should be noted that the techniques discussed here may be applicable to other types of gravel pack completions, such as the cased gravel pack completion described above.

The following discussion will focus on various methods for controlling the bottomhole pressure drop within a subsurface wellbore (eg, wellbore 20). As described above, these methods are designed to control the condition of a near-wellbore cake within a wellbore (eg, within a gravel pack 36) so that the recovery of formation fluids from the subsurface wellbore is improved and maintained. In the following description, reference is always made to the system 10 in FIG. 1; It should be understood, however, that the following methods may be used in wellbore systems other than system 10. Thus, continued reference to system 10 should not be interpreted as limiting the use of the embodiments disclosed herein.

Let us now consider FIG. 3, which shows a graph 100 of the controlled change in bottomhole pressure differential AP versus time for a subsurface wellbore (for example, bore 20 in FIG. 1). On graph 100, the X axis represents time, and the Y axis represents the change in bottomhole pressure differential AP. As shown in graph 100, in some embodiments, the bottomhole pressure differential AP varies cyclically around a predetermined target value 118 between an upper limit 116 and a lower limit 120. Accordingly, the bottomhole pressure differential AP fluctuates in FIG. 3 around target value 118 between limits 116 and 120. Referring to FIG. 1-3, it can be seen that when the previously described system 10 is affected by changes in the bottomhole pressure differential according to schedule 100, the production valve 14 and/or other pressure control mechanism(s) (for example, the previously mentioned back pressure pump) can be activated to achieve the required fluctuations bottomhole pressure difference on graph 100 described above.

As shown in FIG. 3, in this embodiment, the bottomhole pressure differential fluctuation plot 100 is characterized by alternating increases 112 in the bottomhole pressure differential and decreases 114 in the bottomhole pressure differential. Specifically, bottomhole pressure differential increases 112 include increasing the bottomhole pressure differential AP from about a lower limit 120 to about an upper limit 116, and bottomhole pressure drop decreases 114 include decreasing the bottomhole pressure differential from about an upper limit 116 to about a lower limit 120. An upper limit 116 there may be an upper limit for the bottomhole pressure drop AP in the wellbore 20, depending on various factors, for example, pressure and flow restrictions of equipment located inside the wellbore 20 or associated with the fluid (for example, casing 22, tubing 26, collecting filter 30, ground equipment 12, etc.). The lower limit 120 may be determined based on the minimum well production flow rate required from the well 20 during operation. In some embodiments, the lower limit 120 may be sufficient to lift or remove the fines stream (e.g., fines 32 in FIG. 2)

- 5 044688 to the surface 4. In addition, the lower limit 120 may also still be sufficient to lift the produced fluid to the surface and thereby prevent it from accumulating at the bottom of the wellbore 20. In some particular embodiments, the amplitude (i.e., the difference between the upper limit 116 and the lower limit 120) of the bottomhole pressure differential fluctuations (e.g., increases 112 and decreases 114) is about less than or equal to 30% of the target value 118, e.g., less than or equal to 20% of target value 118.

In this embodiment, the target target value 118 may be the average of the upper limit 116 and the lower limit 120, with the BHP increases 112 and BHP decreases 114 equally spaced relative to the target value 118. As a result, in these embodiments, the target value 118 may be referred to as the average value 118. In other embodiments, the target value 118 may be a value between the upper limit 116 and the lower limit 120, which is biased more toward the upper limit 116 or the lower limit 120 (so, that the target value 118 is not the arithmetic mean or average of the upper limit 116 and the lower limit 120. Moreover, in this embodiment, the target value 118 may be relatively constant over a period of time T. It should be noted, however, that changes within the wellbore (e.g., wellbore 20) and/or production system (e.g., system 10) may cause some variation in the target value 118 such that the value is not strictly constant over time. Thus, it should be understood that a relatively constant value 118 corresponds to the value , maintained within a relatively narrow interval around the target value. For example, in some embodiments, the relatively constant target value 118 may be a value in the range of about ±10-15% of the target value. However, in other embodiments, percentage intervals greater than 15% or less than 10% may be considered. In some particular embodiments, the average value 118 may typically be from about 50 to 1500 psi. inch (psi).

In other embodiments, the target value 118 may gradually decrease over time due, for example, to a gradual drop in pressure in the reservoir 6 as a result of formation fluids being produced therefrom. In some of these embodiments, the upper limit 116 and the lower limit 120 may be characterized as percentages above or below, respectively, the target value 118. The target value 118 may gradually fall over time due to a drop in said formation pressure, and may be determined or calculated to provide an optimal level of production from the reservoir 6 during operation.

According to FIG. 3, in this embodiment, the rate or slope of each BHP increase 112 and BHP decrease 114 may be relatively the same. Specifically, the rate of increase 112 of the bottomhole pressure differential from the lower limit 120 to the upper limit 116 may be generally the same as the rate of decrease 114 of the bottomhole pressure differential from the upper limit 116 to the lower limit 120. In some embodiments, the rate of increase 112 of the differential bottomhole pressure and bottomhole pressure drop reductions 114 may depend on various factors, such as the materials forming the reservoir 6, the amount of bottomhole cake already present within the gravel pack 36, the stage of production, the number of pay zones within the reservoir 6, etc. . Without being limited by one theory or another, it is believed that increasing the bottomhole pressure drop AP too quickly can result in large amounts of fines being recovered (eg, due to increased reservoir fluid flow, formation rock decoupling, etc.), which leads to clogging and, as a result, crust buildup in the gravel pack (for example, in gravel filter 36). In addition, a too rapid decrease in bottomhole pressure drop may also cause so-called interlayer flow between different producing zones or depths within the producing formation 6 (for example, due to different rates of pressure increase between separated zones of the producing formation 6). In some particular embodiments, the rate of BHP increases 112 and BHP decreases 114 may typically vary from about 5 to 330 psig. in/hour, or approximately 5 to 50 psi. in/hour, or about 10 to 20 psi. inch/h

The selected values for the upper limit 116 and the lower limit 120, as well as the selected rates of increases 112 of the bottomhole pressure drop and decreases 114 of the bottomhole pressure drop ultimately affect the time interval T ₁₁₂ for each increase 112 of the bottomhole pressure drop and the time interval Tt4 for each decrease 114 of the bottomhole pressure bottomhole pressure, and the total period Chuo of each successive increase 112 in the bottomhole pressure drop and decrease 114 in the bottomhole pressure drop. Specifically, each time period T ₁₁₂ is a period of time or duration of each increase 112 in the bottomhole pressure differential from about the lower limit 120 to about the upper limit 116, and each time period T114 is the period of time or duration of each decrease 114 in the bottom hole pressure differential from approximately the upper limit. 116 to approximately the lower limit of 120. In addition, the total period T _{is 100}

- 6 044688 is the total time period or duration of each successive increase 112 of the bottomhole pressure differential and decrease 114 of the bottomhole pressure differential, or each successive decrease 114 of the bottomhole pressure differential and increase 112 of the bottomhole pressure differential. As previously shown, since the rates of pressure increases 112 and pressure decreases 114 may be the same in this embodiment, the periods T ₁₁₂ , T4 may also be the same.

In the operation illustrated in FIG. 1-3, when the bottomhole pressure differential AP in the system 10 experiences controlled fluctuations through increases 112 and decreases 114 in the bottomhole pressure differentials shown by graph 100, the rate of cake growth within the gravel pack 36 may be reduced or reduced to zero (e.g., the appearance of the cake may be mostly averted). Additionally, in some circumstances, the cake that has already formed within the gravel pack 36 may also be reduced (eg, by erosion) by creating fluctuations in the bottomhole pressure differential AP shown in graph 100. Without being limited by any theory, the fluctuations in the differential bottomhole pressure, expressed by increases 112 and decreases 114 in the bottomhole pressure drop, can lead to the redistribution and movement of fine particles located inside the gravel filter 36, so that there will remain in the aggregate a smaller number of fine particles 32, which will limit and clog the paths 33 movement of fluid flow. In particular, during periods of increasing bottomhole pressure differential AP (eg, through increases in bottomhole pressure differential 112), the flow rate or flow of fluids (eg, formation fluids) from the reservoir 6 into the wellbore 20 may also be increased. This increase in flow rate may cause erosion of fines clumps 32, which will help clean formation fluid passages within the gravel pack 36. Conversely, during periods of decreasing bottomhole pressure differentials AP (for example, decreases 114 in bottomhole pressure differentials), the flow rate or flow of fluids media (eg, formation fluids) from the productive formation 6 into the wellbore 20 may decrease. As the bottomhole pressure drop decreases, the pore pressure increases, and it is believed that this increase in pore pressure reduces the effective pressures within the gravel pack 36 (specifically, the pressures on the particles within the gravel pack 36, including gravel 34 and fines), so may occur destressing the particles within the gravel pack 36. Without being limited by any particular theory, it is believed that this destressing of the particles within the gravel pack 36 may contribute to continued erosion of the fines when the bottomhole pressure differential rises again, causing the inside of the gravel pack to 36, flow passages (eg, for formation fluids) may open.

In some embodiments, the bottomhole pressure differential AP may be maintained within a relatively small range during pressure increases 112 and decreases 114 . For example, without being limited by one theory or another, it is believed that large values of bottomhole pressure differential AP may be associated with more so-called compaction within the gravel pack 36. As a result, lower values of bottomhole pressure differential AP may be associated with larger pore spaces within the gravel pack. filter 36 than the relatively high values of the bottomhole pressure drop AP.

In addition, a higher overall bottomhole pressure differential AP may also result in a reduced size (e.g., diameter) of bubbles within the gravel pack 36 due to the relatively high pressure in the wellbore 20 relative to the reservoir 6 (e.g., if the pressures within the wellbore 20 and/or or productive formation 6 are below the boiling point of the formation fluid). In general, bubbles may block or restrict flow within the pores and passageways of the gravel pack 36, so reducing the size of any bubbles along the gravel pack 36 may promote the formation of any bubbles within the gravel pack 36 and/or may increase the available volumetric flow rate of formation fluids within the gravel pack 36 .

During the described operations, the applied fluctuations in the bottomhole pressure differential may allow some of the fines 32 to pass through the openings 38 in the collection screen 30, causing them to be further recovered to the surface 4. Generally speaking, recovery of the fines 32 is undesirable (and is the main reason for installing a gravel filter 36); however, the relatively low flow rate of fines 32 in tubing string 26 is acceptable, especially if it also provides continued high flow rates of formation fluids by reducing cake. Thus, fluctuations in the bottomhole pressure drop according to schedule 100 can improve the production rate of formation fluids from the well 20 during operation by preventing the formation or even possibly reducing the formation of a bottom-hole crust present there.

In fig. 4 shows another plot 200 of controlled variations in bottomhole pressure differential AP over time T for a subsurface wellbore (eg, wellbore 20 in FIG. 1). Graph 200 is basically similar to graph 100 and therefore the general features and attributes of graphs 100,

- 7 044688

200 are designated by the same reference numerals, and the following discussion will focus on features of graph 200 that are different from those of graph 100. As shown in the previously described FIGS. 1, 2 and 4, if the changes in the bottomhole pressure drop on the graph 200 are applied to the system 10, the production valve 14 and/or other control mechanism(s) (for example, the aforementioned back pressure pump) can be activated to obtain the desired variations in the bottom hole pressure drop on the graph 200 ), as described above.

Just like graph 100, graph 200 includes a repeating sequence of alternating increases 212 and decreases 214 in the bottomhole pressure differential around a predetermined target value 118 between upper and lower limits 116, 120. In this embodiment, however, the increases 212 in the bottomhole pressure differential have an overall smaller speed (or smoother slope) than reducing 214 bottomhole pressure drop. For example, in some embodiments, bottomhole pressure drop decreases 214 may occur at a rate of about 1 to 20 times, or about 10 to 20 times, the rate of bottom hole pressure drop increases 212. In some particular embodiments, the rate of each increase in bottomhole pressure differential 212 may be in the range of from about 5 to 50 psig. in/hour, or about 10 to 20 psi. in/hour, and the rate of each decrease 214 of the bottomhole pressure differential can be from about 5 to 300 psi. inch/h

Accordingly, the time interval T ₂₁₂ for each increase 212 of the bottomhole pressure differential may typically be greater than the time interval T ₂₁₄ for each decrease 214 of the bottomhole pressure differential. For example, in some embodiments, the time interval T ₂₁₂ for each increase in bottomhole pressure differential can be from about 3 to 15 hours, and the time interval T ₂₁₄ for each decrease in bottomhole pressure differential 214 can be from about 1 to 10 hours.

As shown in FIG. 1, 2 and 4, when the bottomhole pressure differential AP within the system 10 experiences controlled fluctuations involving increases 212 and decreases 214 in the bottomhole pressure differential represented by graph 200, the rate of cake growth within the gravel pack 36 can be reduced or growth prevented, and the existing cake also can be shortened as described above. However, by using a reduced rate, and therefore a longer duration of BHP increases 212 compared to BHP decreases 214, in some circumstances the rate of cake growth can be reduced more effectively or growth established. Without being limited by one theory or another, it can be believed that an increase in bottomhole pressure drop is associated with an increase in the flow rate or flow of fluids from the reservoir into the wellbore 20, which may promote the formation of clean channels for formation fluids through the gravel pack 36, as was the case described above. At the same time, due to the reduction in the rate of increase 212 of the bottomhole pressure drop compared to the rate of decrease 214 of the bottomhole pressure drop, more time is allocated for operating in the high flow mode, and accordingly, its inherent benefits give a better result over time. Thus, fluctuations in bottomhole pressure differential in accordance with schedule 200 can improve the production rate of formation fluids from wellbore 20 during operation by preventing cake buildup or even possibly reducing existing cake.

While the BHP changes described above were centered around a substantially or relatively constant target value (e.g., the values shown in plots 100, 200 of FIGS. 3 and 4, respectively), it should be understood that other embodiments may include fluctuations in the bottomhole pressure drop around a target value that changes in a controlled manner over time. For example, in FIG. 5 shows another graph 300 of controlled oscillations of bottomhole pressure differential AP versus time T for a subsurface well (eg, wellbore 20 in FIG. 1). Previously, with reference to FIG. 1, 2, and 5, it was shown that if changes in the bottomhole pressure drop according to schedule 300 are applied to the system 10, the production valve 14 and/or other pressure control mechanism(s) (e.g. , the said backpressure pump), as described above.

In fig. 5, in particular, shows that for this embodiment, the graph 300 illustrates the oscillation of the bottomhole pressure differential AP around a target value varied in a predetermined manner. In particular, plot 300 includes oscillations alternating between phase 330 and phase 332.

During the first phase 330, fluctuations in the bottomhole pressure differential AP include a series of increases 312 in the bottomhole pressure differential and a series of decreases 314 in the bottomhole pressure relative to a predetermined target value 306. Increases 312 and decreases 314 in the bottomhole pressure differential may occur between an upper limit 302 and a lower limit 310, which may be similar to the upper and lower limits described above with respect to schedules 100, 200 (eg, upper and lower limits 116 and 120, respectively). In addition, the predetermined target value 306 may be the average of the limits 302, 310, or may be offset to one of the limits 302, 310, as described above for the target value 118 for the previously described schedules 100, 200.

- 8 044688 Moreover, increases 312 and decreases 314 of bottomhole pressure differential within the first phase may have generally the same rates or slopes (for example, as shown in graph 100 for increases 112 and decreases 114 of bottomhole pressure drop) or different speeds or slopes (for example , as shown in graph 200 for increases 212 and decreases 214 of bottomhole pressure drop). Thus, the above descriptions relating to the fluctuations of the bottom hole pressure drop in FIG. 3 and 4 can be applied to describe the increases and decreases 312, 314 in the bottom hole pressure drop within the first phase 330.

Next in FIG. 5 shows that during the second phase 332, the bottomhole pressure differential AP oscillates around a target value, which increases in a controlled manner in several stages. In this embodiment, the target value is increased in two steps between three different values, however, the number of steps may be different in other embodiments. Specifically, in this embodiment, the bottomhole pressure differential AP varies within a first series of oscillations 332a, including increases 316 and decreases 318 in the bottomhole pressure differential around a predetermined target value 308. The bottomhole pressure differential AP then varies within a second series of oscillations 332b, including increases 320 and decreasing 322 the bottomhole pressure differential around a given target value 306. And finally, the bottomhole pressure differential AP varies within the third series of oscillations 332c, which includes increases 324 and decreases 326 in the bottomhole pressure differential around a given target value 304.

Target value 304 is greater than target value 306, and target value 306 is greater than target value 308. Moreover, in this embodiment, target value 306 associated with increases and decreases 320 and 322, respectively, is substantially equal to target value 306 associated with increases and decreases 312, 314 in the first phase 330.

As shown in FIG. 5, it can also be seen that increases 316 and decreases 318 of bottomhole pressure differentials AP within the first set of fluctuations 332a can occur approximately between the lower limit 310 and the upper limit 306. Thus, in this embodiment, the lower limit 310 of the first range of bottomhole pressure fluctuations 332a may be substantially equal to the lower limit of the BHP fluctuations (e.g., increases 312 and decreases 314) during the first phase 330, and the upper limit 306 of the first series of BHP fluctuations 332a may be substantially equal to the target value of the BHP fluctuations during first phase 330.

Within the second set of oscillations 332b, the increase 320 and decrease 322 of the bottomhole pressure differential AP are approximately between the lower limit 308 and the upper limit 304. Thus, in this embodiment, the upper limit 304 of the second set of oscillations 332b is substantially equal to the target value of the third set of oscillations. 332c, and the lower limit 308 of the second waveform 332b is substantially equal to the target value of the first waveform 332a.

In the third set of oscillations 332c, the increase 324 and decrease 326 of the bottomhole pressure differential AP are approximately between the upper limit 302 and the lower limit 306. Thus, in this embodiment, the lower limit 306 of the third set of oscillations 332c is substantially equal to the upper limit of the first set of oscillations 332a and the target value of the BHP differential fluctuation in the first phase 330. In addition, the upper limit 302 of the third row of fluctuations 332c is generally equal to the upper limit of the BHP differential fluctuation in the first phase 330.

It should be understood that the various previously described equalities of target values, upper limits and lower limits of the first phase 330 and second phase 332 are features of only some embodiments, such as the embodiment shown in FIG. 5. Thus, in other embodiments, there is no such equality (or approximate equality) between all or some of the target values, upper limits, and lower limits of the bottomhole pressure drop fluctuations in each of the first phase 330 and the second phase 332. Moreover, even in the embodiment shown in FIG. 5, changes in bottomhole pressure differential AP during operation may mean that the actual target values, upper limits, and lower limits used may not exhibit the same equations as described for the idealized case presented in FIG. 5. Therefore, the equations described above should not be perceived as limiting the scope of the general provisions disclosed here in relation to fluctuations in bottomhole pressure drop.

Shown in FIG. 5, fluctuations 332a, 332b, 332c of the bottomhole pressure drop in the second phase 332 may vary around the respective target values 308, 306, 304, respectively, as described above for the graphs 100, 200. For example, the target values 308, 306, 304 may be the average values of the respective upper and lower limits 306 and 310, 304 and 308, and 302 and 306, respectively, or may be values shifted closer to one of the respective upper and lower limits 306 and 310, 304 and 308, and 302 and 306, respectively. In addition, the various increases 316, 320, 324 and decreases 318, 322, 326 of the bottomhole pressure differential oscillations 332a, 332b, 332c, respectively, may have substantially the same speeds or slopes (e.g., as shown in graph 100 for increases 112 and decreases 114 bottom hole pressure drop, or different speeds

- 9 044688 or slopes (for example, as shown by graph 200 for increases 212 and decreases 214 of bottomhole pressure drop).

As shown in FIG. 1, 2 and 5, as the bottomhole pressure differential AP system 10 is subject to controlled oscillations in accordance with schedule 300, the rate of cake growth within the gravel pack 36 can also be reduced or growth stopped, and the existing cake can also be reduced as it has been described above. However, in some circumstances, cake formation can be more effectively prevented or mitigated by changing the target value and fluctuation limits for alternating fluctuations in the bottomhole pressure differential between the first and second phases 330, 332, respectively, as described above.

In particular, without being limited by any theory, the first phase 330 may be considered to include relatively greater fluctuations in the bottomhole pressure differential increases 312 and decreases 314 than the bottomhole pressure differential fluctuations 332a, 332b, 332c in the second phase 332. In other words, fluctuations in the bottomhole pressure drop within the first phase 330 may have a greater amplitude than the fluctuations in the bottomhole pressure drop in the second phase 332 (eg, fluctuations 332a, 332b, 332c). For example, in some particular embodiments, fluctuations in the bottom hole pressure drop within the first phase 330 may have an amplitude of approximately 200 psig. inch, each of the first, second and third rows 332a, 332b, 332c, respectively, in the second phase may have an amplitude of approximately 40 psi. inch. Higher amplitude pressure fluctuations within the first phase 330 may provide a greater, or more aggressive change in the flow rate or flow of fluid within the gravel pack 36 so that compacted fines 32 in the gravel pack 36 can be eroded to open up channels within the gravel pack. 36 (in particular, inside the crust formed there), and can provide increased flow rate of the formation fluid flow passing through the filter. To further enhance the erosive effect, in some embodiments, the duration of the BHP increases 312 may be increased compared to the duration of the BHP decreases 314 in accordance with what was described above with respect to the increases 212 and decreases 214 in the graph 200.

Additionally, without being limited to any theory, it is believed that progressively increasing target values associated with oscillations 332a, 332b, 332c within the second phase 322 may contribute to the initial release of particles (eg, during the first set of oscillations 332a) followed by increasing changes in fluid flow rate or flow (e.g., during the second and third sets of oscillations 332c, 332d thereafter. In particular, the bottomhole pressure differential AP typically decreases as the transition occurs from the oscillations of the bottomhole pressure drop within the first phase 330 to the first set of oscillations 332a bottomhole pressure differentials that may create a weakened or reduced effect on the particles within the gravel pack 36 (including gravel pack 34 and fines 32).As a result, the particles within the gravel pack 36 may be redistributed, opening or widening channels in the filter. Subsequently, As the bottomhole pressure differentials AP change within the second set of oscillations 332b and then within the third oscillation set 332c, the changes in the bottomhole pressure differentials AP are generally increased relative to the first set of oscillations 332a so that fluid flow is primarily increased on the particles within the gravel pack 36 and Erosion of these new or enlarged canals may occur. Thus, the reduction in applied pressure and subsequent particle erosion as the fluid flow within the gravel pack 36 gradually increases during the first, second, and third sets of vibrations 332a, 332b, and 332c, respectively, may further increase the flow of well production from reservoir 6 into borehole 20

In addition, overall increases in changes in bottomhole pressure differentials AP in the second and third oscillation rows 332b and 332c, respectively, may also contribute to the progression of erosive effects further out from the collection filter 30. In particular, the overall gradual increase in changes in bottomhole pressure differentials AP as a result The first row oscillations 332b and the second row oscillations 332c are also associated with a generally progressively increasing flow rate or flow of fluid, as described above. As the flow rate or flow of fluid through the gravel pack 36 generally progressively increases during the second set of oscillations 332b and the third set of oscillations 332d, erosion of the channels within the gravel pack 36 progressively extends further and further outward from the collection filter 30 to productive formation 6 and deeper into it. Beginning with the series of oscillations 332a within the second phase 332, free channels are formed in the gravel pack 36, providing space for the release of new fines to be extracted to the surface (eg, surface 4) during the action of the series of oscillations 332b and 332c. After a third series of oscillations 332c during the second phase 332, the bottomhole pressure differential AP again oscillates between greater increases 312 and decreases 314 in the bottomhole pressure differential in the first phase 330 to further enhance channel erosion within the gravel pack 36, as described above.

In addition, fluctuations in the level of generally reduced bottomhole pressure AP drops during

The first set of second phase oscillations 332a may also reduce the size of gas bubbles trapped within the gravel pack 36 (eg, in situations where the pressure within the gravel pack 36 is below the boiling point of the hydrocarbons released from the reservoir 6). In particular, as shown above, a relatively high bottomhole pressure differential AP is associated with a relatively low wellbore pressure (since the bottomhole pressure differential AP is the difference between the reservoir pressure and the wellbore pressure, as shown above). Thus, at elevated values of bottomhole pressure differential AP (for example, associated with increases 312 in bottomhole pressure differential and decreases 314 in bottomhole pressure differential during the first phase 330), large gas bubbles can form (for example, bubbles of hydrocarbon gas extracted from the reservoir 6 ), which are retained within the gravel filter 36 and thereby clog or restrict the fluid flow channels present therein. However, when performing bottomhole pressure differential AP swings with relatively low first row 332a swing values, the overall increased pressure within the wellbore 20 (associated with lower bottomhole pressure differential AP) reduces the size of any bubbles trapped within the gravel pack 36. By reducing the size of those trapped bubbles, additional space is formed for the opening of free channels, which facilitates the extraction of small particles forming a crust onto the surface (for example, surface 4). As a result, during subsequent oscillations of the bottomhole pressure differential AP during the second and third series of oscillations 332b and 332c, respectively, these newly cleaned channels allow a flow of produced fluids to flow into the collection filter 30.

Returning to FIG. 5, note that in some embodiments, the decision to switch between first phase 330 and second phase 332 (or even when to switch between different oscillations 332a, 332b, 332c within second phase 332 may be based on a predetermined timing schedule For example, in some embodiments, the first phase 330 may be conducted over a period of time ranging from about 1 to 10 days, and the second phase 332 may be conducted over a period of time ranging from about 1 to 30 days. of the first phase 330 may be increased relative to the duration of the second phase 332 so as to maximize the time during which the greater fluctuations in the bottomhole pressure differential AP during the first phase 330 (e.g., increases 312 and decreases 314 in the bottomhole pressure differential) act internally wellbore (eg, wellbore 20) to make fuller use of the erosion results described above.

Additionally, during every second phase 332, each subsequent oscillation 332a, 332b, 332c of the bottomhole pressure differential may occur over a period of time ranging from about 1 to 10 days. In some embodiments, the duration of exposure to each of the bottomhole pressure differential oscillations 332a, 332b, 332c is generally the same. However, in other embodiments, the duration of one or more (including all) BHP fluctuations 332a, 332b, 332c may be different from other BHP fluctuations during the second phase 332.

Additionally, in other embodiments, decisions about when to switch between the first phase 330 and the second phase 332 (or even switch between different vibrations 332a, 332b. 332c within the second phase 332) can be made based on monitoring one or more parameters wellbore 20 or system 10. For example, in some embodiments, formation fluid flow and/or pressure in the wellbore (e.g., wellbore 20) may be an indicator that the effectiveness of the current control law for bottomhole pressure differential fluctuations has decreased, and therefore It's time for personnel (or the controller described below) to adjust the control law for bottomhole pressure differential fluctuations (for example, make adjustments associated with changes from the first phase 330 to the second phase 332, or changes between different fluctuations 332a, 332b, 332c within the second phase 332) . In particular, if the current oscillation law is effective in reducing the bottom-hole crust within the wellbore 20, the flow of fluid from the reservoir into the wellbore 20 may increase, which is also accompanied by an increase in pressure in the wellbore 20. However, if the flow rate of the formation fluid or the pressure in the wellbore 20 increases, a decision may be made (by personnel and/or controller) to maintain the current oscillation law. However, if the formation fluid flow rate and/or the pressure in the wellbore 20 remains unchanged or decreases, a decision may be made to change from the current vibration law to a new vibration law involving a change between the first phase 330 and the second phase 332, or between vibrations 332a , 332b, 332c of the second phase 332, as shown above.

Next in FIG. 6 shows a method 500 for controlling the condition of a near-wellbore zone cake in a subsurface wellbore. The method 500 may be implemented in any subsurface well, such as, in particular, a wellbore that is undergoing a gravel pack completion (e.g., wellbore 20), during a self-contained filter completion, etc. In the following description, method 500 will be discussed in relation to previously described systems

- 11 044688 and graphs 100, 200 pressure. However, this specific example should not be taken as limiting the use of method 500. Moreover, in some embodiments, method 500 may be implemented in whole or in part using a controller (eg, controller 400 described below).

Initially, method 500 begins at step 505 by oscillating the bottomhole pressure drop in a subsurface wellbore (eg, wellbore 20) around a predetermined target bottomhole pressure drop value according to a given oscillation law. In particular, the specified oscillation law at step 505 may be similar to the oscillations described above and illustrated by graphs 100, 200 (see FIGS. 3 and 4). Thus, the oscillations at step 505 may include an increase in the bottomhole pressure differential from the lower limit to the upper limit followed by a decrease in the bottomhole pressure differential from the upper limit to the lower limit (for example, the lower limit 120 and the upper limit 116 shown in FIGS. 3 and 4). . In some embodiments, the oscillations at step 505 may include an increase in the bottomhole pressure drop at a first rate followed by a decrease in the bottomhole pressure drop at a second rate different from the first rate. Specifically, in some embodiments, the second speed may be greater than the first speed (eg, as shown in FIG. 3 for graph 100). In other embodiments, the oscillations at step 505 may include an increase in the first velocity BHP differential followed by a decrease in the first velocity BHP differential (eg, as shown in FIG. 4 for graph 200).

Next, method 500 includes, at step 510, maintaining a target bottomhole pressure drop value at a generally constant level during the fluctuations at step 505. In particular, maintaining a substantially constant level of target bottom hole pressure drop value may include maintaining a target bottom hole pressure drop value at a given interval, for example, as described above in relation to the target value of 118 on chart 100.

In fig. 7 shows another method 600 for controlling the condition of the near-wellbore zone cake in a subsurface wellbore. The method 600 can be implemented in any subsurface well, such as, in particular, a wellbore that is completed using gravel packs (eg, wellbore 20). In the following description, method 600 will be discussed in relation to the previously described system 10 and pressure graph 300. However, this specific example should not be taken as limiting the use of method 600. Moreover, in some embodiments, method 600 may be implemented in whole or in part using a controller (eg, controller 400 described below).

Initially, method 600 begins at step 605 by causing the bottomhole pressure drop in a subsurface wellbore (eg, wellbore 20) to oscillate around a first predetermined target bottomhole pressure drop value according to a first predetermined oscillation law. Next, in a second step 610, the method 600 includes causing the bottomhole pressure drop in the subsurface wellbore to oscillate at a second predetermined target value different from the first target bottomhole pressure drop value, according to a second predetermined oscillation law.

The second target bottomhole pressure drop value may be greater or less than the first target bottom hole pressure drop value. In particular, steps 605, 610 of method 600 may correspond to a change or offset from the first phase 330 to the second phase 332, or a change or offset between different vibrations 332a, 332b, 332c of the second phase 332 in the plot 300 of FIG. 5. Additionally, in some embodiments, method 600 may also include causing the bottomhole pressure differential to oscillate around a second target value at step 610 after a predetermined time interval has elapsed since the bottomhole pressure differential oscillated around the first target value at step 605. Further, in some In embodiments, method 600 may also include generating oscillations of the bottomhole pressure differential around a second target value at step 610 after generating oscillations of the bottomhole pressure differential around the first target value based on changes in pressure within the wellbore and/or flow rate of formation fluids within the wellbore.

In addition, the first and second predetermined oscillation laws at steps 605 and 610, respectively, may be similar to the oscillation laws described above and shown in graphs 100, 200, 300 (see FIGS. 3-5). The oscillations at steps 605, 610 may include an increase in the bottomhole pressure differential from a corresponding lower limit to a corresponding upper limit, followed by a decrease in the bottomhole pressure differential from a corresponding upper limit to a corresponding lower limit (for example, lower limit 120 and upper limit 116 shown in 3 and 4, or limits 302, 304, 306, 308, 310, etc. shown in Fig. 5), In some embodiments, the first and/or second oscillation laws are specified at steps 605 and 610, respectively , may include increasing the bottomhole pressure drop at a first speed and then decreasing the bottomhole pressure drop at a second speed different from the first speed. In particular, in some embodiments, the second speed may be greater than the first speed (eg, as shown in FIG. 3 by graph 100). In other embodiments, the first and/or second oscillation laws at steps 605 and 610, respectively, may include an increase in the first velocity BHP differential followed by a decrease in the first velocity BHP differential (for example, as shown in FIG. 4 schedule 200).

In fig. 1 also illustrates that the system 10 may also include a controller 400 coupled to the production valve 14 (and/or other pressure control mechanisms that the system 10 includes) and configured to adjust the position of the production valve 14 to control the downhole pressure differential in the wellbore as described above (eg, as described above with reference to schedules 100, 200, 300, etc.). The controller 400 may be part of a larger device or control unit, such as a device that controls the operation of the system 10 as a whole, or it may be a stand-alone control unit to perform the functions described. Additionally, as discussed above, controller 400 may be located on surface 4 near or on ground equipment 12, or may be located remotely from system 10 (eg, in a central office or control room connected to system 10 by communications). In general, the controller 400 includes a processor 402 and a storage device 404 (memory).

A processor 402 (e.g., a microprocessor, a central processing unit, or a group of such processing devices, etc.) executes computer-readable instructions (e.g., programs) stored in a storage device 404, and upon executing the computer-readable instructions stored in a storage device 404, provides the controller 400 with the ability perform all the functions described here. Storage device 404 may include volatile memory (eg, random access memory), non-volatile device (eg, flash memory, read only memory, etc.), or combinations of both volatile and non-volatile memory. Data consumed or generated by processor 402 when executing computer-readable instructions may also be stored in memory 404. Memory 404 may comprise non-volatile computer-readable media.

In operation, the controller 400 (via computer-readable instructions executed by the processor 402) can controllably activate the production valve 14 (and/or a backpressure pump or other pressure control mechanism in the system 10) to control the bottom hole pressure drop in the wellbore 20. Specifically, controller 400 may selectively vary the bottomhole pressure differential within the wellbore 20 according to any of the embodiments and methods described above (e.g., as shown in graphs 100, 200, 300 or described above in methods 500, 600, etc.) . In other embodiments, controller 400 may signal to personnel (e.g., via a display device or otherwise) that certain activation of the service valve 14 (and/or some other pressure control mechanism) is required to, for example, provide a change in differential bottomhole pressure in the wellbore 20 in the manner described above (for example, shown in graphs 100, 200, 300). The controller 400 may selectively adjust the bottom hole pressure drop (or signal to personnel about necessary changes in the bottom hole pressure drop) based on a predetermined time schedule or on one or more measured or derived or calculated parameters as previously described above (for example, downhole pressure 20 wells, flow rate of formation fluids, etc.). As a result, processor 402 may periodically take pressure readings from sensor 13 (or one or more other sensors located at various locations in system 10) while performing the functions described above or thereafter.

The various previously described fluctuations in bottomhole pressure drop can be carried out throughout the life of the well, or can be applied during certain periods of the well's operation. For example, the BHP fluctuations described above (e.g., shown by graphs 100, 200, 300, etc.) can be used immediately or shortly after completion of gravel pack completions to provide so-called fines removal. fractions (eg, fines 32) that may be deposited within the gravel pack 36 as a result of the well completion activities themselves. In addition, the above-described fluctuations in bottomhole pressure drops can be used during normal fluid production operations after a cleanup period. Further, in some embodiments, one embodiment or type of oscillation (e.g., one of the oscillation laws illustrated by graphs 100, 200, 300, etc.) may be used while performing the above-mentioned cleaning, while another The embodiment or type of oscillation can be further used during subsequent production operations after cleaning. Additionally, in some embodiments, a number of different vibration laws (eg, the vibration laws illustrated by graphs 100, 200, 300) may be used to create a bottomhole pressure differential during cleaning and/or fluid production operations.

Thus, by selectively oscillating the bottomhole pressure drop in a subsurface gravel pack wellbore 36 (e.g., wellbore 20), bottom hole crusts that form within the gravel pack (e.g., fines cakes) can be prevented, reduced, or eliminated. 32 inside the gravel filter 36). As a result, through the use of the methods described herein for generating oscillations in the bottomhole pressure differential, the flow rate of formation fluids from a subsurface wellbore can be increased so that the overall production rate of the well can be increased.

The graphs of changes in the bottomhole pressure difference discussed above include essentially linear changes in the bottomhole pressure difference AP (for example, graphs 100, 200, 300, etc.). It should, however, be borne in mind that in other embodiments, the bottomhole pressure drop AP may vary significantly according to a nonlinear law. For example, in some embodiments, the bottomhole pressure differential AP may oscillate around a target value in a sinusoidal (or approximately sinusoidal) pattern or relationship. In addition, in some embodiments, changes in the bottomhole pressure differential AR may contain the superposition of two wave processes, for example, two oscillations according to a sinusoidal law.

While particular embodiments have been shown and described, modifications thereof may be made by one skilled in the art within the spirit or principles of the disclosure. The described embodiments are illustrative only and do not limit the invention. Many changes and modifications to the systems, apparatus, and processes described herein are possible without departing from the spirit of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but only to the following claims, the scope of which is to include all equivalents of the subject matter of the claims. Unless specifically stated otherwise, the steps of a method formula may be performed in any order. Listing the notation, for example, (a), (b), (c) or (1), (2), (3) before the steps in the formula for a method does not imply or determine a specific order of steps, but rather is used to simplify further links to these steps.

To further illustrate various embodiments, the following examples are provided. It should be understood, however, that the embodiments disclosed herein are not limited to the examples below.

Example 1.

Inside the wellbore, bottomhole pressure differential oscillations were created according to the pattern shown in FIG. 8, involving repeated pressure fluctuations between approximately 1250 psig. and approximately 1000 psi. inch g. over a time interval of approximately 50 hours. As a result of these fluctuations, oil production productivity increased by approximately 250 barrels per day (bbld/d - from the English barrel per day), which corresponds to an increase in total production of approximately 4.5%.

Example 2.

A transparent conical chamber was made, into which a layer of transparent gravel particles was placed. In addition, a layer of dark fines with an average diameter of 1/20th the diameter of the clear gravel particles was placed on top of the clear gravel particles, which would represent the trapped fines that formed the crust that formed. Next, under the influence of hydrostatic pressure applied to the layer of fine particles and transparent gravel, the fine particles were pressed into the gravel. In fig. 9 is a composite graph 601 of the mass flow rate 602, in gallons per second (gps), flowing out of the clear chamber and the magnitude of the applied hydrostatic pressure 604, in centimeters (cm), inside the clear chamber as a function of time in seconds (s). Similarly, in FIG. 10(a)-10(m) show images of gravel and particles inside the conical chamber at different times during the experiment.

As shown in FIG. 9, in the initial phase of the experiment from time 2000 s to about 3250 s, the applied hydrostatic pressure was kept constant at about 45 cm. During this phase, there was little or no particle movement through the gravel, and the fluid flow through the transparent chamber was 0. 12 gps. Then, at about 3250 s, hydrostatic pressure oscillations were excited, the hydrostatic pressure oscillating according to the first law between about 45 cm and about 30 cm, then according to the second law between about 30 cm and about 17.5 cm, and finally according to the third law between approximately 17.5 cm and approximately 5 cm. This general vibration pattern was repeated a total of three times. During the experiment, small dark particles were extracted through the transparent gravel and the crust was reduced. As a result, the fines flow rate quadrupled from an initial rate of approximately 0.12 g/s at 2000 s to a measured rate of approximately 0.48 g/s at approximately 7500-8500 s. Moreover, as can be understood from FIG. 10(a)-10(m), the erosion of fine particles and their extraction through the transparent gravel mainly occurred during exposure to the cyclic vibrations shown in FIG. 9.

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Claims (14)

CLAIM 1. A method for controlling the condition of the bottom-hole zone crust inside a subsurface wellbore, during which: (a) create oscillations of the bottomhole pressure drop in the subsurface wellbore in accordance with a given law, including a plurality of alternating increases in the bottomhole pressure drop and decreases in the bottomhole pressure drop, and increases in the bottomhole pressure drop according to a given law include an increase in the bottomhole pressure drop at the first rate, and decreases differences in bottomhole pressure according to a given law include a decrease in the difference in bottomhole pressure at a second speed that differs from the first speed. 2. The method according to claim 1, wherein the second speed is greater than the first speed. 3. The method according to claim 2, in which the second speed is approximately 10-20 times greater than the first speed. 4. The method of claim 2 or 3, wherein the first speed is about 10 to 20 psi. inch per hour. 5. The method according to any of the previous paragraphs, in which at step (a) oscillations of bottomhole pressure differences are created around the first specified target value; and then in step (b), after step (a), they create oscillations of the bottomhole pressure drop in accordance with the second specified law around the second specified target value, which differs from the first specified target value. 6. The method according to claim 5, in which: keeping the first predetermined target value substantially constant in step (a); and keeping the second predetermined target value substantially constant in step (b). 7. The method as claimed in any one of the preceding claims, wherein step (a) causes the bottomhole pressure differential between the upper and lower limits to oscillate around a first predetermined target value and, optionally, the first predetermined target value is the average value of the upper limit and the lower limit. 8. The method according to any of claims 5, or 6, or 7, depending on claim 5 or 6, in which additionally: (c) create oscillations of the bottomhole pressure drop around the third specified target value, after step (b); and (d) causing the bottomhole pressure differential to oscillate around a fourth predetermined target value, following step (c), wherein the fourth predetermined target value exceeds the third predetermined target value, and the third predetermined target value exceeds the second predetermined target value. 9. The method according to claim 8, in which: oscillations in step (a) have a first amplitude, oscillations in step (b) have a second amplitude, oscillations in step (c) have a third amplitude, and oscillations in step (d) have a fourth amplitude, the first amplitude being greater than the second amplitude, the third amplitude and fourth amplitude. 10. The method according to claim 9, in which steps (a), (b), (c) and (d) are additionally repeated. 11. A system for producing hydrocarbons from a subsurface wellbore, including: a tubing string installed inside the wellbore; a production valve in fluid communication with the tubing string so that formation fluids passing into the wellbore flow through the tubing string to the production valve; and a controller connected to the production valve and configured to selectively actuate the production valve to: (a) creating oscillations of the bottomhole pressure drop in the wellbore according to a given law, including a plurality of alternating increases in bottomhole pressure drops and decreases in bottomhole pressure drops, and increases in bottomhole pressure drops according to a given law include increases in bottomhole pressure drops at the first rate, and decreases in bottomhole pressure drops according to a given law, they include a decrease in bottomhole pressure drops at a second speed, different from the first speed. 12. The system according to claim 11, wherein the second speed is greater than the first speed. 13. The system of claim 12, wherein the second speed is about 10 to 20 times the first speed. 14. The system according to any one of paragraphs 11-13, in which: the controller is configured to create, in step (a), oscillations of the bottomhole pressure differential around a first target value, and the controller is configured to create, in step (b) after step (a), oscillations of the bottomhole pressure differential in accordance with a second predetermined law around a second predetermined target value different from the first target value. -