A method for monitoring and controlling pressure limit value in fracturing and packing construction

Abstract

The application discloses a kind of fracturing filling construction pressure limiting value monitoring control methods, solve the technical problem that whether wellhead pump injection pressure is safe cannot be judged.The method includes monitoring the pump injection pressure P d Of drill pipe at wellhead;Monitoring the pressure P a Of annular wellhead;Blind pipe outside liquid column pressure P hs It is calculated;Blind pipe inside liquid column pressure P hc It is calculated;According to formula: P d +P hs <P b +(P a +P hc ) whether wellhead pump injection pressure is in the safe range of pressure limiting value, if it meets pressure limiting value safe range, then keep constant voltage and continue production, if it exceeds pressure limiting value safe range, then pump pressure relief;Wherein, P b It is the limit value of blind pipe resistance to external pressure.The application can judge whether wellhead pump injection pressure is safe, ensure that wellhead pump injection pressure is less than pressure limit, to ensure that downhole tool pressure is in safe range, to ensure construction safety.

Description

Technical Field

[0001] This invention belongs to the field of oilfield well completion technology, specifically relating to a method for monitoring and controlling the pressure limit value during fracturing and filling construction. Background Technology

[0002] Currently, fracturing and backfilling sand control technology has been widely used as a new type of mechanical sand control method that integrates production increase and sand control.

[0003] Chinese patent CN110847874B discloses a fracturing, filling, and sand-removing tubing string, comprising a casing, a completion and sand control tubing string, and a service tubing string. After perforation of the oil well, a perforated section is formed on the casing. The completion and sand control tubing string is located inside the casing, with its outer diameter smaller than the inner diameter of the casing. A packer is installed on the outer surface of the completion and sand control tubing string, dividing the space inside the casing into two closed upper and lower spaces. The perforated section is located below the packer. Above the packer, the completion and sand control tubing string has an upper through-hole connecting the inside and outside of the tubing. The tubing string has a lower through-hole below the packer, connecting the inside and outside of the completion sand control tubing string; a screen pipe is connected to the lower end of the completion sand control tubing string below the lower through-hole via a blind pipe; a flushing pipe is installed inside the screen pipe, forming a space with the screen pipe and the screen pipe with an open lower end; the service tubing string is located inside the completion sand control tubing string, and the outer diameter of the lower end of the service tubing string is smaller than the inner diameter of the completion sand control tubing string; the space formed by the outer wall of the lower end of the service tubing string and the inner walls of the completion sand control tubing string and the flushing pipe allows the upper through-hole of the completion sand control tubing string to connect with the space with the lower opening formed by the flushing pipe and the screen pipe.

[0004] Currently, safety is paramount during the aforementioned tubing string installation process, with pressure safety being a key concern. In related technologies, the safety of the wellhead pumping pressure cannot be determined during tubing string installation, making it difficult to ensure that downhole tools are under pressure within safe limits, thus posing a safety hazard that needs improvement. Summary of the Invention

[0005] To address all or part of the aforementioned problems, the present invention aims to provide a method for monitoring and controlling the pressure limit during fracturing and filling operations. This method can determine whether the wellhead pumping pressure is safe and ensure that the wellhead pumping pressure is less than the pressure limit, thereby ensuring that the pressure of downhole tools is within a safe range and thus guaranteeing construction safety.

[0006] This invention provides a method for monitoring and controlling the pressure limit value during fracturing and filling operations, comprising:

[0007] Monitor the pumping pressure P of the drill pipe at the wellhead d ;

[0008] Monitor the pressure P at the annular wellhead a ;

[0009] Calculate the pressure P of the liquid column outside the blind tube.hs ;

[0010] Calculate the liquid column pressure P inside the blind tube. hc ;

[0011] According to the formula:

[0012] P d +P hs <P b +(P a +P hc )

[0013] Determine the wellhead pumping pressure P d If the pressure is within the safe range of the pressure limit, then maintain constant pressure and continue production; if the pressure exceeds the safe range of the pressure limit, then stop the pump and release the pressure.

[0014] Among them, P b This is the limit value of the blind tube's resistance to external pressure.

[0015] Optionally, when the pump stops during fracturing and filling operations, the fluid stops flowing, there is no friction in the tubing string, and the pressure on the outside of the blind pipe is the same as the pumping pressure P of the drill pipe at the wellhead. d The pressure P of the liquid column outside the blind tube hs sum;

[0016] The pressure P of the liquid column outside the blind tube hs The hydrostatic pressure is the sum of the hydrostatic pressure at the filling hole of the service tubing from the drill pipe and the hydrostatic pressure at the connection between the filling hole of the sand control tubing outside the blind pipe and the blind pipe / screen pipe. Both the fluid at the filling hole of the drill pipe and the fluid at the connection between the filling hole of the sand control tubing outside the blind pipe and the blind pipe / screen pipe are pumped sand-carrying fluids. Therefore, the hydrostatic pressure P outside the blind pipe is... hs This refers to the hydrostatic pressure formed at the depth of the sand-carrying fluid at the connection point between the blind tube and the screen tube.

[0017] Alternatively, via the formula:

[0018] P hs =ρ1gh

[0019] Calculate the liquid column pressure P outside the blind tube. hs ρ1 is the density of the sand-carrying liquid, g is the gravitational acceleration, and h is the vertical depth of the construction layer.

[0020] Alternatively, via the formula:

[0021]

[0022] Calculate the proppant carrying fluid density ρ1, where ρ0 is the density of the fracturing fluid base, C is the mass of proppant per unit volume of fracturing fluid base, and AVF is the volume corresponding to a unit mass of proppant.

[0023] Optionally, at the instant the pump is stopped during fracturing and filling operations, the pressure on the inside of the blind pipe is the same as the pressure P at the annular wellhead. a The pressure P of the liquid column inside the blind tube hc sum;

[0024] The pressure P of the liquid column inside the blind tube hc The hydrostatic pressure is the sum of the hydrostatic pressure at the circulation port from the casing annulus to the service tubing and the hydrostatic pressure in the inner annulus from the circulation port of the service tubing to the connection between the blind pipe and the screen pipe. Since the valve at the annulus wellhead is closed, the fluid in the inner annulus and the casing annulus above the packer is not flowing, and all fluid is completion fluid injected before construction. Therefore, the hydrostatic pressure P inside the blind pipe is... hc This refers to the hydrostatic pressure of the completion fluid at the depth of the connection between the blind pipe and the screen pipe.

[0025] Alternatively, according to the formula:

[0026] P hc =ρ2gh

[0027] Calculate the liquid column pressure P inside the blind tube. hc ρ2 is the density of the completion fluid, g is the gravitational acceleration, and h is the vertical depth of the construction layer.

[0028] Optionally, the pumping pressure P of the drill pipe at the wellhead can be monitored and read using a pressure monitoring system at the wellhead. d Pressure P at the annular wellhead a .

[0029] Optionally, meeting the pressure limit safety range means that the difference between the pressure borne by the outer side of the blind tube and the pressure borne by the inner side of the blind tube is less than the external pressure resistance value P of the blind tube. b .

[0030] As can be seen from the above technical solution, the method for monitoring and controlling the pressure limit value during fracturing and filling construction provided by the present invention has the following advantages:

[0031] This method can convert the pressure resistance limit of the weak pressure-bearing point in the well into the wellhead pumping pressure. By monitoring the wellhead pumping pressure in real time, it can determine whether the wellhead pumping pressure is safe and take corresponding control strategies to ensure that the pressure of the downhole tools is within a safe range. This not only ensures construction safety but also provides a basis for selecting the external pressure resistance value of the tubing string.

[0032] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0033] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0034] Figure 1 This is a schematic diagram of the structure of a fracturing and desanding tubing string in the prior art;

[0035] Figure 2 This is a flowchart of an embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Service tubing; 2. Sand control tubing; 3. Packer; 4. Casing; 6. Blind tube; 7. Screen tube; 8. Circulation hole of service tubing; 9. Filling hole of sand control tubing; 10. Filling hole of service tubing; 11. Outer annulus; 12. Inner annulus; 13. Casing annulus. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be arbitrarily combined with each other.

[0039] like Figure 2 The illustration shows an embodiment of the present invention, which discloses a method for monitoring and controlling the pressure limit value during fracturing and filling operations, comprising: monitoring and reading the pumping pressure P of the drill pipe at the wellhead through a pressure monitoring system at the wellhead. d and the pressure P at the annular wellhead a ; Calculate the pressure P of the liquid column outside the blind tube. hs and the liquid column pressure P inside the blind tube hc .

[0040] According to the formula: P d +P hs <P b +(P a +P hc Determine the wellhead pumping pressure P d If the pressure is within the safe range of the pressure limit, then maintain constant pressure and continue production. If the pressure exceeds the safe range, then stop the pump and release the pressure. The P in the formula... b This is the limit value of the blind pipe's resistance to external pressure; this data is a known value.

[0041] like Figure 1 The diagram shows a fracturing and filling desanding tubing string in the prior art. When fracturing and filling are carried out normally, the valve at the annular wellhead is closed, and the sand-carrying fluid and proppant enter the formation. At this time, the pressure of the casing 4 and the drill pipe is connected through the filling hole 10 of the service tubing string and the filling hole 9 of the sand control tubing string. The sand control tubing string 2 and the service tubing string 1 do not bear the internal and external pressure difference.

[0042] When the proppant fills the formation fractures, it begins to fill the annulus between the screen pipe 7 and the casing 4. As the proppant rises higher within this annulus, reaching the top of the screen pipe 7, the fluid flow channel returning to the wellhead is blocked, causing a sharp increase in pumping pressure, triggering desanding pressure, and resulting in pump shutdown at the surface. Instantly, the blind pipe 6 becomes disconnected from the outside. At this point, the pressure difference experienced by the blind pipe 6 is considered to be the greatest, and the pressure difference between the outer annulus 11 and the inner annulus 12 of the blind pipe 6 is the pressure difference borne by the blind pipe 6.

[0043] When the pump stops during fracturing and filling operations, the pumped fluid ceases to flow, there is no friction in the tubing string, and the pressure on the outside of blind pipe 6 is the same as the pumping pressure P of the drill pipe at the wellhead. d The pressure P of the liquid column outside the blind tube 6 hs The sum of the pressures. However, the hydrostatic pressure outside the blind pipe 6 is the sum of the hydrostatic pressure inside the drill pipe to the filling hole 10 of the service pipe and the hydrostatic pressure from the filling hole 9 of the sand control pipe outside the blind pipe 6 to the connection between the blind pipe 6 and the screen pipe 7.

[0044] Since the liquid inside the drill pipe to the filling hole 10 of the service tubing and the liquid outside the blind pipe 6 from the filling hole 9 of the sand control tubing to the connection between the blind pipe 6 and the screen pipe 7 are both pumped sand-carrying fluids, the liquid column pressure outside the blind pipe 6 is the static liquid column pressure Phs formed by the sand-carrying fluid at the depth of the connection between the blind pipe 6 and the screen pipe 7.

[0045] Therefore, by formula: P hs =ρ1gh calculates the pressure P of the liquid column outside the blind tube. hs ρ1 is the density of the sand-carrying liquid, g is the gravitational acceleration, and h is the vertical depth of the construction layer.

[0046] At the same time, through the formula:

[0047]

[0048] Calculate the proppant carrying fluid density ρ1, where ρ0 is the density of the fracturing fluid base, C is the proppant concentration, i.e., the mass of proppant per unit volume of fracturing fluid base, and AVF is the absolute volume factor of the proppant, i.e., the volume corresponding to a unit mass of proppant.

[0049] At the instant the pump is stopped during fracturing and filling operations, the pressure on the inside of blind pipe 6 is the same as the pressure P at the annular wellhead. a The pressure P of the liquid column inside the blind tube 6 hc The sum. However, the liquid column pressure P inside blind tube 6 hc It is the sum of the hydrostatic pressure at the circulation hole 8 of the service tubing from the annulus 13 to the circulation hole 8 of the service tubing and the hydrostatic pressure in the annulus 12 at the connection between the circulation hole 8 of the service tubing and the blind tube 6 and the screen tube 7.

[0050] Because the valve at the annular wellhead is closed, the fluid within the inner annulus 12 and the casing annulus 13 above the packer 3 is not flowing, and it is all completion fluid injected before construction. Therefore, the fluid column pressure P inside the blind pipe 6 is... hc This refers to the hydrostatic pressure of the completion fluid at the depth of the connection between blind pipe 6 and screen pipe 7.

[0051] Therefore, according to the formula: P hc =ρ2gh Calculate the liquid column pressure P inside the blind tube hc ρ2 is the density of the completion fluid, g is the gravitational acceleration, and h is the vertical depth of the construction layer.

[0052] In this embodiment, meeting the pressure limit safety range means that the difference between the pressure on the outside of the blind tube and the pressure on the inside of the blind tube is less than the external pressure resistance value P of the blind tube. b That is, satisfying (P) d +P hs )-(P a +P hc ) < P b .

[0053] To explain this embodiment more clearly, specific examples are as follows:

[0054] The oil well underwent fracturing and filling operations at a vertical depth h of 1543m. The pumping pressure P at the wellhead was monitored. d The pressure P at the annular wellhead is 3445 psi. a The pressure is 1120 psi, the external pressure resistance of the blind tube is 7500 psi, the proppant concentration in the wellbore is 5 ppg, the absolute volume factor (AVF) of the proppant is 0.0442 gal / lb, the density of the fracturing fluid base is 8.5 lb / gal, and the density of the completion fluid is 8.5 lb / gal.

[0055]

[0056] P hs =ρ1gh=2893psi

[0057] P hc =ρ2gh=2235psi

[0058] P d <P b -P hs +(P a +P hc )

[0059] P d <7962psi

[0060] Based on the above, the construction pressure limit should be set below 7962 psi. At this point, the pumping pressure of the drill pipe at the wellhead is 3445 psi. Therefore, the pressure limit is within a safe range, and constant pressure production can be maintained.

[0061] As can be seen from the above process, the pressure limit monitoring and control method for fracturing and filling construction in this embodiment can convert the pressure resistance limit of the downhole pressure-bearing weak point into the wellhead pump injection pressure. By monitoring the wellhead pump injection pressure in real time, it can determine whether the wellhead pump injection pressure is safe and take corresponding control strategies to ensure that the pressure of the downhole tools is within a safe range. This not only ensures construction safety but also provides a basis for selecting the external pressure resistance value of the tubing string.

[0062] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0063] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for monitoring and controlling the pressure limit value during fracturing and filling construction, characterized in that, include: Monitor the pumping pressure P of the drill pipe at the wellhead d ; Monitor the pressure P at the annular wellhead a ; Calculate the pressure P of the liquid column outside the blind tube. hs ; Calculate the liquid column pressure P inside the blind tube. hc ; According to the formula: P d +P hs <P b +(P a +P hc ) Determine the wellhead pumping pressure P d If the pressure is within the safe range of the pressure limit, then maintain constant pressure and continue production; if the pressure exceeds the safe range of the pressure limit, then stop the pump and release the pressure. Among them, P b The pressure P of the liquid column outside the blind tube is the limit value of the blind tube's resistance to external pressure. hs The hydrostatic pressure of the sand-carrying fluid at the depth of the connection between the blind tube and the screen tube is P, and the fluid column pressure inside the blind tube is P. hc The static pressure of the completion fluid at the depth of the blind pipe / screen pipe connection is considered to meet the safety limit value, meaning the difference between the pressure on the outside and inside of the blind pipe is less than the external pressure resistance value P of the blind pipe. b .

2. The method for monitoring and controlling the pressure limit value during fracturing and filling construction according to claim 1, characterized in that, When the pump stops during fracturing and filling operations, the fluid stops flowing, there is no friction in the tubing string, and the pressure on the outside of the blind pipe is the same as the pumping pressure P of the drill pipe at the wellhead. d The pressure P of the liquid column outside the blind tube hs sum; The pressure P of the liquid column outside the blind tube hs The pressure is the sum of the hydrostatic pressure from the drill pipe to the filling hole of the service tubing and the hydrostatic pressure from the filling hole of the sand control tubing outside the blind pipe to the connection of the blind pipe and the screen pipe. Both the liquid from the drill pipe to the filling hole of the service tubing and the liquid from the filling hole of the sand control tubing outside the blind pipe to the connection of the blind pipe and the screen pipe are pumped sand-carrying fluids.

3. The method for monitoring and controlling the pressure limit value during fracturing and filling construction according to claim 2, characterized in that, By formula: P hs =ρ1gh Calculate the liquid column pressure P outside the blind tube. hs ρ1 is the density of the sand-carrying liquid, g is the gravitational acceleration, and h is the vertical depth of the construction layer.

4. The method for monitoring and controlling the pressure limit value during fracturing and filling construction according to claim 3, characterized in that, By formula: Calculate the proppant carrying fluid density ρ1, where ρ0 is the density of the fracturing fluid base, C is the mass of proppant per unit volume of fracturing fluid base, and AVF is the volume corresponding to a unit mass of proppant.

5. The method for monitoring and controlling the pressure limit value during fracturing and filling construction according to claim 1, characterized in that, At the instant the pump is stopped during fracturing and filling operations, the pressure on the inside of the blind pipe is the same as the pressure P at the annular wellhead. a The pressure P of the liquid column inside the blind tube hc sum; The pressure P of the liquid column inside the blind tube hc It is the sum of the hydrostatic pressure at the circulation port of the service tubing from the casing annulus to the service tubing and the hydrostatic pressure in the inner annulus at the connection between the service tubing circulation port and the blind pipe / screen pipe. Since the valve at the annulus wellhead is closed, the fluid in the inner annulus and the casing annulus above the packer is not flowing, and all of them are completion fluids injected before construction.

6. The method for monitoring and controlling the pressure limit value during fracturing and filling construction according to claim 5, characterized in that, According to the formula: P hc =ρ2gh Calculate the liquid column pressure P inside the blind tube. hc ρ2 is the density of the completion fluid, g is the gravitational acceleration, and h is the vertical depth of the construction layer.

7. The method for monitoring and controlling the pressure limit value during fracturing and filling construction according to claim 1, characterized in that, The pumping pressure P of the drill pipe at the wellhead is monitored and read through the pressure monitoring system at the wellhead. d Pressure P at the annular wellhead a .

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