A device and method for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling

Abstract

The present invention relates to a device and method for quickly regulating the bottom hole pressure after overflow in deep-water shallow open-circuit drilling, which belongs to the technical field of marine oil and gas resource drilling, and includes a real-time monitoring device and a real-time regulating device. In view of the characteristics of deep-water shallow open-circuit drilling, the present invention proposes to monitor the return of the seabed drilling fluid through a seabed ROV, and analyze in real time whether gas invasion occurs at the bottom of the well, as well as the changes in the gas invasion rate, formation pressure, etc. after the gas invasion occurs, so as to guide the design of key parameters such as the displacement and density of the well-killing fluid in real time, and adjust the displacement and density parameters of the well-killing fluid in real time, so as to realize the rapid regulation of the bottom hole pressure after the deep-water shallow open-circuit gas invasion. At the same time, in the process of regulating the bottom hole pressure by injecting the well-killing fluid, the ROV monitors the return of the seabed drilling fluid in real time, and then analyzes the bottom hole pressure regulation state, so as to realize the safe and rapid regulation of the bottom hole pressure after the deep-water shallow open-circuit drilling gas invasion, thereby ensuring the safe and efficient drilling of deep-water oil and gas.

Description

Technical Field

[0001] The invention relates to a device and method for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling, belonging to the technical field of marine oil and gas resource drilling. Background Art

[0002] my country is rich in deepwater oil and gas resources. According to statistics, the deepwater oil and gas reserves in the South China Sea exceed 70 billion tons. Therefore, in order to meet the needs of rapid economic and social development, the safe and efficient development of deepwater oil and gas resources is an important way to solve the contradiction between oil and gas supply and demand and build a strong maritime nation. Drilling is the basis of deepwater oil and gas development and a key step in building a flow channel between deepwater oil and gas reservoirs and drilling / production platforms. The safety of drilling determines the success and efficiency of later oil and gas resource development. Due to the characteristics of shallow burial, high mud content, poor diagenesis, and low formation strength in deepwater shallow formations, in order to improve the drilling efficiency of deepwater shallow formations, open-circuit drilling technology is often used in deepwater shallow formation drilling. That is, when drilling deepwater shallow formations, no riser and blowout preventer are put in. The drilling fluid in the annulus below the mud line carries the cuttings directly back to the seabed, which can improve the drilling efficiency of deepwater shallow formations and shorten the drilling cycle.

[0003] However, shallow gas, shallow flow, shallow hydrate and other geological disasters are easy to be encountered in the process of deep-water shallow drilling. Since no watertight pipe and blowout preventer are installed in the process of deep-water shallow open-circuit drilling, it is very easy to have complicated gas invasion during drilling. In this case, once gas invasion occurs, it will be impossible to shut down the well, which may lead to the evolution of gas invasion into well kick or even blowout. The existing well-killing methods such as engineer method and driller method are mainly aimed at the overflow situation in the closed-circuit drilling process. During the well-killing process, the bottom hole situation needs to be inverted through the wellhead parameters such as mud pool increment, casing pressure, gas content, etc. that are monitored in real time. Since the drilling fluid does not return to the platform wellhead during deep-water open-circuit drilling, the multiphase flow parameters in the wellbore cannot be monitored, which may lead to greater blindness and uncertainty in the bottom hole pressure control during open-circuit drilling. The gas invasion process is very fast. Once the treatment measures are improperly taken, it is very easy to miss the best treatment time, which will make the gas invasion difficult to control. Therefore, there is currently a lack of a safe and fast method for regulating the bottom hole pressure after overflow in deep-water shallow open-circuit drilling. This problem is the key to restricting the safety of deep-water shallow open-circuit drilling and is also an important factor affecting the safe and efficient drilling of deep-water oil and gas. Therefore, there is an urgent need for a method for quickly controlling the bottom hole pressure after overflow in deep-water shallow open-circuit drilling. For this reason, the present invention is proposed. Summary of the invention

[0004] In view of the shortcomings of the prior art, especially the problem that the existing treatment methods cannot quickly and reasonably determine the bottom hole pressure control parameters after overflow in deep-water shallow open-circuit drilling, the present invention proposes a device and method for quickly controlling the bottom hole pressure after overflow in deep-water shallow open-circuit drilling. By combining real-time observation of an underwater remote-controlled robot (Remote Operated Vehicle, referred to as ROV), real-time inversion of formation pressure and real-time control of well killing parameters, rapid and reasonable deep-water shallow open-circuit drilling overflow disposal measures are guaranteed. The present invention can quickly discover and control the overflow problem of deep-water shallow open-circuit drilling, avoid the overflow from evolving into a well kick or even a blowout accident, and provide theoretical and technical support for safe and efficient open-circuit drilling in deep-water shallow layers.

[0005] The present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a device for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling, comprising a real-time monitoring device and a real-time regulating device, wherein the real-time monitoring device comprises a submarine ROV, a data transmission optical cable and a computer processing center, wherein the submarine ROV is placed at a submarine wellhead through a towing rope, and is used to take real-time images of the return of drilling fluid from the submarine wellhead; the towing rope connects the submarine ROV to a platform, and the submarine ROV is connected to the computer processing center through a data transmission optical cable, and the data transmission optical cable is tied to the towing rope; the computer processing center receives the return images of drilling fluid taken by the submarine ROV in real time, and analyzes the shape and height of the returned drilling fluid in real time;

[0007] The real-time control device comprises a signal receiving and executing mechanism, a drilling fluid injection pump, a mud pool and a drilling fluid injection pipeline. One end of the signal receiving and executing mechanism is connected to a computer processing center, and the other end is connected to the drilling fluid injection pump; the drilling fluid injection pump is connected to the mud pool and connected to the seabed wellhead through the drilling fluid injection pipeline;

[0008] The drilling fluid injection pipeline is provided with a valve, a pressure sensor and a temperature sensor A, the mud pool is connected with a temperature sensor B, and the pressure sensor, the temperature sensor A and the temperature sensor B are all connected with a computer processing center.

[0009] On the other hand, the present invention provides a method for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling, which is implemented by the above-mentioned device for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling, and comprises the following steps:

[0010] (1) Subsea ROV monitors the return of drilling fluid from the subsea wellhead in real time

[0011] The ROV installed on the seabed monitors the return of drilling fluid from the seabed wellhead in real time, and transmits the captured images of the return of drilling fluid to the computer processing center of the platform in real time. The computer processing center combines the existing database and uses image processing technology to analyze the return flow morphology parameters of the drilling fluid in real time;

[0012] (2) Real-time calculation of bottom hole gas invasion rate and formation pressure

[0013] Combined with the drilling fluid return conditions photographed by the seabed ROV, the bottom hole gas invasion rate and formation pressure are calculated based on the obtained drilling fluid return flow morphology parameters and basic parameters, laying the foundation for the design of the well killing fluid parameters required for bottom hole pressure control;

[0014] (3) Rapid response and control of bottom hole pressure

[0015] According to the calculated bottom hole gas invasion rate and formation pressure, key parameters such as the density and displacement of the well-killing fluid required to handle overflow and regulate the bottom hole pressure are designed to control the start and stop and injection power of the drilling fluid injection pump. At the same time, the required well-killing fluid is quickly configured on the platform, and the well-killing fluid is injected into the bottom hole in time to regulate the bottom hole pressure to control gas invasion. The gas invasion control situation is analyzed in real time through seabed ROV monitoring.

[0016] Preferably, in step (1), the drilling fluid return flow morphology parameters include the distance x between the return drilling fluid position and the drilling fluid return center and the drilling fluid return height H(x);

[0017] The computer processing center obtains the distance x between the return drilling fluid position and the return drilling fluid center through image processing technology. The flow pattern of the return drilling fluid in deepwater open circuit drilling conforms to the normal distribution function:

[0018]

[0019] Where H(x) is the drilling fluid return height, m; x is the distance between the return drilling fluid position and the drilling fluid return center, m; a is the square root of the variance of x, m; b is the expected distance value, m;

[0020] The maximum height of drilling fluid return under no gas invasion conditions can be calculated by the following formula:

[0021]

[0022] In the formula, H max is the maximum height of drilling fluid return, m; d is the equivalent diameter of the return outlet, m; g is the gravitational acceleration, m / s 2 ; ρ is the drilling fluid density, / cm 3 ρ a is the density of seawater, g / cm 3 ;v mis the flow rate of the return drilling fluid, m / s;

[0023] The maximum height of drilling fluid return under gas invasion conditions can be calculated by the following formula:

[0024]

[0025] Preferably, in step (2), before the gas invades the wellbore, the wellbore is a single-phase flow of drilling fluid, so the initial bottom hole annular pressure can be calculated by the following formula:

[0026] P wf =P c +ρgh+ΔP fa (4)

[0027] Where P wf is the annular pressure at the bottom of the well, MPa; P c is the seabed wellhead pressure, MPa; P fa is the annular friction of single-phase flow, MPa; ρ is the drilling fluid density, kg / m 3 ; h is the vertical depth of the well below the mud line, m;

[0028] According to the Reynolds number, the flow state in the wellbore is divided into laminar flow and turbulent flow. In drilling engineering, it is believed that when Re<2100, the flow state of the drilling fluid is laminar flow; when Re≥2100, the flow state of the drilling fluid is turbulent. Under different drilling fluid flow states, the rock carrying performance of the drilling fluid is different, and the annular friction pressure loss ΔP fa Also different;

[0029] The Reynolds number is calculated as follows:

[0030]

[0031] In the formula, v l is the annular drilling fluid velocity, m / s; d is the annular equivalent diameter, m; μ p is the plastic viscosity, Pa·s;

[0032] Under laminar flow conditions, the calculation formula for annular friction pressure loss is as follows:

[0033]

[0034] In the formula, τ 0 is the dynamic shear force, MPa; d a is the inner diameter of the annulus, m; d po is the outer diameter of the drill string, m;

[0035] Under turbulent conditions, the calculation formula for annular friction pressure loss is as follows:

[0036]

[0037] Where f is the friction coefficient, dimensionless, and is calculated by formula (8):

[0038]

[0039] When the annular pressure P is obtained, wf After that, the bottom hole gas invasion rate can be calculated by the formation productivity equation:

[0040]

[0041] In the formula, Q gd is the bottom hole gas invasion rate, m 3 / s; K g is the gas permeability in the formation, μm 2 ;P e ′ is the assumed formation pressure, MPa; h r is the thickness of the open reservoir, m; μ g is the gas dynamic viscosity, Pa·s; S is the skin coefficient, dimensionless; t is the gas invasion occurrence time, s; is the porosity of the reservoir, dimensionless; c is the reservoir gas compressibility coefficient, dimensionless; r w is the borehole radius, m; γ is the Euler-Mascheroni constant (γ≈0.577);

[0042] After gas invasion occurs in deepwater open-circuit drilling, the wellbore is a gas-liquid multiphase flow process. The wellbore multiphase flow model is shown as follows:

[0043] Liquid mass conservation equation:

[0044]

[0045] Gas phase mass conservation equation:

[0046]

[0047] Gas-liquid two-phase momentum equation:

[0048]

[0049] In the formula, ρ l , g are respectively the liquid phase density and the gas phase density, kg / m 3 ; E l 、E g are the cross-sectional liquid content and cross-sectional gas content, dimensionless; A a is the cross-sectional area of ​​the annulus, m 2 ;v l 、v gare the annular liquid velocity and annular gas velocity, m / s; t is the time of gas invasion, s; z is the axial distance from the wellhead, m; P a is the wellbore annulus pressure, MPa; P fa is the annular friction, MPa; q g is the gas flow rate in the annulus, m 3 / s, at the bottom boundary of the wellbore, q g Equal to Q calculated by formula (9) gd , that is, Q gd is the bottom hole input boundary condition of the gas phase mass conservation equation;

[0050] Formulas (10), (11), and (12) are solved together to obtain the key instantaneous flow parameters in the wellbore, including the wellbore annulus pressure P a , cross-sectional air content E g , annular air phase velocity v g ;

[0051] The gas invasion rate at the mud line calculated by the model is:

[0052]

[0053] In the formula, Q ca is the gas invasion rate at the mudline calculated by the model, m 3 / s; N ml is the well depth node at the mudline, dimensionless; Δh is the spatial step length, m;

[0054] At the same time, according to the drilling fluid return height H(x), distance x and formulas (1) to (3) obtained by seabed ROV observation, the flow rate v of the return drilling fluid can be obtained: m ;

[0055] Then, according to formula (14), the annular air phase velocity v in the return drilling fluid can be obtained g :

[0056] ν m =v g E g +ν l (1-E g ) (14)

[0057] Then, according to formula (15), the gas invasion rate of deepwater shallow open-circuit drilling calculated by seabed ROV measured data can be obtained:

[0058] Q g =v g A a E g (15)

[0059] Among them, Qg is the drilling gas invasion rate calculated from the actual data measured by the seabed ROV, m 3 / s; A a is the cross-sectional area of ​​the annulus, m 2 ;

[0060] Combining formulas (1) to (3), (14), and (15), the gas intrusion rate is derived as:

[0061]

[0062] Preferably, in step (2), Q ca With Q g , and the calculation error ε is obtained:

[0063] ε=|Q ca -Q g | (17)

[0064] Then, the bisection method is used to converge the model to calculate the results: If the calculated value of the mudline gas invasion rate Q ca Less than the calculated value Q from seabed ROV observation g , which indicates that the assumed formation pressure P e ′ is too small, at this time, e ′ plus ΔP to obtain the new assumed formation pressure P e1 ', and then repeat the above steps until Q ca Equal to Q g ;

[0065] If the calculated value of mud line gas invasion rate is Q ca Greater than the calculated value Q from seabed ROV observation g , which indicates that the assumed formation pressure P e If ′ is too large, the new formation pressure can be directly assumed by equation (18):

[0066] The next assumed formation pressure P en 'for:

[0067]

[0068] Until Q ca With Q g If the error condition is met, the formation pressure P is obtained. e .

[0069] Preferably, ΔP is between 0.1 and 3 MPa.

[0070] Preferably, in step (3), since it takes a certain amount of time to configure the well-killing fluid with the required density for well killing, the displacement of the drilling fluid / well-killing fluid should be increased first to increase the bottom hole pressure to reduce the bottom hole gas invasion, which is achieved by controlling the power of the drilling fluid injection pump; when the well-killing fluid with the required density is configured, the bottom hole pressure is controlled by combining the injection of new well-killing fluid and displacement regulation.

[0071] Preferably, after gas invasion occurs in deepwater shallow open-circuit drilling, the flow friction of the annulus can be increased by increasing the displacement of the drilling / killing fluid, thereby increasing the bottom hole pressure, thereby achieving the purpose of reducing gas invasion and balancing the formation pressure. The required killing fluid displacement calculation method is:

[0072]

[0073] Where, d h is the diameter of the annular flow section, m; P e is the formation pressure of the deep water shallow layer, Pa; P wh is the hydrostatic pressure of seawater, Pa; ρ l is the mixed density of drilling fluid during well drilling, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; h is the vertical depth of the mud line from the bottom of the well, m; f is the friction coefficient, dimensionless; L is the depth of the well below the mud line, m; Q L is the drilling fluid displacement, m 3 / min; Q s is the maximum displacement allowed by the drilling equipment, m 3 / min; P c is the minimum value of bottom hole fracture pressure and leakage pressure, Pa;

[0074] At the same time, the density of the injected killing fluid is increased to increase the gravity of the liquid column in the annulus. As the higher density killing fluid is injected from the drill pipe into the bottom of the well, the bottom hole pressure gradually increases with the friction effect exerted by the increased displacement, and the gas invasion volume at the bottom of the well will gradually decrease. In order to achieve successful well killing, according to the formation pressure obtained above, the required mixing density of the killing fluid is calculated by the following relationship:

[0075]

[0076] In the formula, ρ a is the density of seawater, kg / m 3 ;h sw is the water depth at the seabed mudline, m; h is the vertical depth of the mudline from the bottom of the well, m; ρ l is the mixed density of drilling fluid during well drilling, kg / m 3 ;P p is the bottom hole fracture pressure, Pa;

[0077] When the required killing fluid is configured, the bottom hole pressure is jointly regulated by injecting the killing fluid and controlling the killing fluid displacement to control the bottom hole gas invasion and balance the formation pressure. At the same time, during the well killing process, the seabed ROV is used to monitor the return of the seabed drilling fluid to analyze the gas invasion control situation in real time until the bottom hole gas invasion is completely controlled.

[0078] For any details not provided in the present invention, please refer to the prior art.

[0079] The beneficial effects of the present invention are:

[0080] Aiming at the characteristics of deep-water shallow open-circuit drilling, the present invention proposes to monitor the return of seabed drilling fluid through seabed ROV, and analyze in real time whether gas invasion occurs at the bottom of the well, as well as the changes in gas invasion rate, formation pressure, etc. after gas invasion occurs, so as to guide the design of key parameters such as well-killing fluid displacement and density in real time, and adjust the well-killing fluid displacement and density parameters in real time to achieve rapid regulation of bottom hole pressure after deep-water shallow open-circuit gas invasion. At the same time, in the process of regulating the bottom hole pressure by injecting well-killing fluid, ROV monitors the return of seabed drilling fluid in real time, and then analyzes the bottom hole pressure regulation state, so as to achieve safe and rapid regulation of bottom hole pressure after gas invasion in deep-water shallow open-circuit drilling, thereby ensuring safe and efficient drilling of deep-water oil and gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0082] Figure 1 It is a schematic diagram of a device for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling in a certain embodiment of the present invention;

[0083] In the figure, 1-seawater, 2-shallow seabed, 3-cementing cement ring, 4-drill bit, 5-drill pipe, 6-returned drilling fluid, 7-seabed ROV, 8-traction rope, 9-seabed wellhead, 10-drilling fluid injection pipeline, 11-pressure sensor, 12-temperature sensor A, 13-valve, 14-drilling fluid injection pump, 15-mud pool, 16-temperature sensor B, 17-signal receiving and actuator, 18-computer processing center. DETAILED DESCRIPTION

[0084] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in the art.

[0085] Example 1

[0086] A device for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling, such as Figure 1 As shown, it includes a real-time monitoring device and a real-time control device. The real-time monitoring device includes a submarine ROV 7, a data transmission optical cable and a computer processing center 18. The submarine ROV 7 is placed at a submarine wellhead 9 through a towing rope 8, and is used to take real-time images of the return of drilling fluid from the submarine wellhead 9, and transmit the images of the return of drilling fluid taken by the submarine ROV to the computer processing center in real time; the towing rope 8 connects the submarine ROV 7 to the platform, and the submarine ROV 7 is connected to the computer processing center 18 through a data transmission optical cable, and the data transmission optical cable is tied to the towing rope 8; the computer processing center 18 receives the images of the return of drilling fluid taken by the submarine ROV 7 in real time, and analyzes the shape and height of the returned drilling fluid in real time;

[0087] The real-time control device includes a signal receiving and executing mechanism 17, a drilling fluid injection pump 14, a mud pool 15 and a drilling fluid injection pipeline 10. One end of the signal receiving and executing mechanism 17 is connected to a computer processing center 18, and the other end is connected to the drilling fluid injection pump 14; the drilling fluid injection pump 14 is connected to the mud pool 15, and is connected to a seabed wellhead 9 through the drilling fluid injection pipeline 10;

[0088] The drilling fluid injection pipeline 10 is provided with a valve 13 , a pressure sensor 11 and a temperature sensor A12 , the mud pool 15 is connected with a temperature sensor B16 , and the pressure sensor 11 , the temperature sensor A12 and the temperature sensor B16 are all connected with a computer processing center 18 .

[0089] Figure 1 The apparatus also includes a drill bit 4, a shallow seabed 2, a cementing cement ring 3 and a drill pipe 5. The drill pipe 5 is immersed in the seawater 1. A seabed ROV 7 is placed at a seabed wellhead through a towing rope to capture images of drilling fluid 6 returning from the seabed wellhead in real time.

[0090] In the present invention, the computer processing center 14 determines whether overflow occurs at the bottom of the well and the degree of overflow by analyzing the shape and height of the returned drilling fluid, and obtains the parameters such as the drilling fluid displacement and density required to control the bottom hole pressure, and then sends instructions to the signal receiving and executing mechanism; after receiving the instructions from the computer processing center, the signal receiving and executing mechanism controls the start and stop and injection power of the drilling fluid injection pump; the drilling fluid injection pump is connected to the signal receiving and executing mechanism and the mud pool, and when receiving the drilling fluid injection instruction, the drilling fluid is drawn from the mud pool and injected into the drill pipe through the drilling fluid injection pipeline; the temperature sensor A monitors the temperature of the drilling fluid injected into the drill pipe in real time, the pressure sensor monitors the injection pressure at the wellhead in real time, and the temperature sensor B monitors the temperature of the drilling fluid in the mud pool in real time; the valve is installed between the wellhead and the drilling fluid injection pump, and is opened when drilling fluid needs to be injected.

[0091] Example 2

[0092] A method for quickly regulating bottom hole pressure after overflow in deepwater shallow open-circuit drilling comprises the following steps:

[0093] (1) Subsea ROV monitors the return of drilling fluid from the subsea wellhead in real time

[0094] The ROV installed on the seabed monitors the return of drilling fluid from the seabed wellhead in real time, and transmits the captured images of the return of drilling fluid to the computer processing center of the platform in real time. The computer processing center combines the existing database and uses image processing technology to analyze the return flow morphology parameters of the drilling fluid in real time;

[0095] (2) Real-time calculation of bottom hole gas invasion rate and formation pressure

[0096] Combined with the drilling fluid return conditions photographed by the seabed ROV, the bottom hole gas invasion rate and formation pressure are calculated based on the obtained drilling fluid return flow morphology parameters and basic parameters, laying the foundation for the design of the well killing fluid parameters required for bottom hole pressure control;

[0097] (3) Rapid response and control of bottom hole pressure

[0098] According to the calculated bottom hole gas invasion rate and formation pressure, key parameters such as the density and displacement of the well-killing fluid required to handle overflow and regulate the bottom hole pressure are designed to control the start and stop and injection power of the drilling fluid injection pump. At the same time, the required well-killing fluid is quickly configured on the platform, and the well-killing fluid is injected into the bottom hole in time to regulate the bottom hole pressure to control gas invasion. The gas invasion control situation is analyzed in real time through seabed ROV monitoring.

[0099] Example 3

[0100] A method for quickly controlling the bottom hole pressure after overflow in deep-water shallow open-circuit drilling is as described in Example 2, except that in step (1), the submarine ROV 7 is lowered to the submarine wellhead 9 by a towing rope 8, and the image of the drilling fluid return from the submarine wellhead can be photographed in real time, and the photographed drilling fluid return image is transmitted to the computer processing center on the drilling platform in real time through a signal transmission optical cable. The computer processing center stores a database of drilling fluid return images of deep-water shallow open-circuit drilling. Through image processing technology, combined with the existing database and the analysis and processing of the field drilling fluid return images photographed, the drilling fluid return flow morphology parameters in the deep-water shallow open-circuit drilling process can be obtained. The drilling fluid return flow morphology parameters include the distance x between the position of the returned drilling fluid and the center of the drilling fluid return and the drilling fluid return height H(x), which can lay a foundation for the calculation of the bottom hole gas invasion.

[0101] The computer processing center obtains the distance x between the return drilling fluid position and the return drilling fluid center through image processing technology. The flow pattern of the return drilling fluid in deepwater open circuit drilling conforms to the normal distribution function:

[0102]

[0103] Where H(x) is the drilling fluid return height, m; x is the distance between the return drilling fluid position and the drilling fluid return center, m; a is the square root of the variance of x, m; b is the expected distance value, m. If there are all data values ​​of x, the b value is the arithmetic mean of all data values. If there is only a probability density function, the value can be calculated by integration.

[0104] The maximum height of drilling fluid return under no gas invasion conditions can be calculated by the following formula:

[0105]

[0106] In the formula, H max is the maximum height of drilling fluid return, m; d is the equivalent diameter of the return outlet, m; g is the gravitational acceleration, m / s 2 ; ρ is the drilling fluid density, / cm 3 ρ a is the density of seawater, g / cm 3 ;v m is the flow rate of the return drilling fluid, m / s;

[0107] The maximum height of drilling fluid return under gas invasion conditions can be calculated by the following formula:

[0108]

[0109] When judging whether there is gas invasion, on the one hand, the seabed ROV observation can be used to determine whether gas invasion has occurred. If gas invasion has occurred, the return drilling fluid will contain gas. In addition, according to the above calculation, the flow rate v of the return drilling fluid can be obtained. m size, which can also be calculated by comparing v m and the annular liquid velocity v l (This value can be obtained by the ratio of drilling fluid displacement and annular cross-sectional area) to determine whether gas invasion has occurred. m Greater than v l , indicating that gas invasion has occurred, otherwise, gas invasion has not occurred.

[0110] Example 4

[0111] A method for quickly regulating the bottom hole pressure after overflow in deep-water shallow-layer open-circuit drilling is as described in Example 3, except that in step (2), the return of drilling fluid during deep-water shallow-layer open-circuit drilling is directly affected by whether gas invasion occurs at the bottom of the well, the gas invasion rate, and the formation pressure. Based on the shooting of the drilling fluid return by the seabed ROV and the analysis of the flow parameters, combined with the wellbore multiphase flow theory, the bottom hole gas invasion rate and the formation pressure at the gas invasion location can be calculated.

[0112] Before the gas invades the wellbore, the drilling fluid flows in a single phase in the wellbore, so the initial bottom hole annulus pressure can be calculated by the following formula:

[0113] P wf =P c +ρgh+ΔP fa (4)

[0114] Where P wf is the annular pressure at the bottom of the well, MPa; P c is the seabed wellhead pressure, MPa; P fa is the annular friction of single-phase flow, MPa; ρ is the drilling fluid density, kg / m 3 ; h is the vertical depth of the well below the mud line, m;

[0115] According to the Reynolds number, the flow state in the wellbore is divided into laminar flow and turbulent flow. In drilling engineering, it is believed that when Re<2100, the flow state of the drilling fluid is laminar flow; when Re≥2100, the flow state of the drilling fluid is turbulent. Under different drilling fluid flow states, the rock carrying performance of the drilling fluid is different, and the annular friction pressure loss ΔP fa Also different;

[0116] The Reynolds number is calculated as follows:

[0117]

[0118] In the formula, v l is the annular drilling fluid velocity, m / s; d is the annular equivalent diameter, m; μ p is the plastic viscosity, Pa·s;

[0119] Under laminar flow conditions, the calculation formula for annular friction pressure loss is as follows:

[0120]

[0121] In the formula, τ 0 is the dynamic shear force, MPa; d a is the inner diameter of the annulus, m; d po is the outer diameter of the drill string, m;

[0122] Under turbulent conditions, the calculation formula for annular friction pressure loss is as follows:

[0123]

[0124] Where f is the friction coefficient, dimensionless, and is calculated by formula (8):

[0125]

[0126] When the annular pressure P is obtained, wfAfter that, the bottom hole gas invasion rate can be calculated by the formation productivity equation:

[0127]

[0128] In the formula, Q gd is the bottom hole gas invasion rate, m 3 / s; K g is the gas permeability in the formation, μm 2 ;P e ′ is the assumed formation pressure, MPa; h r is the thickness of the open reservoir, m; μ g is the gas dynamic viscosity, Pa·s; S is the skin coefficient, dimensionless; t is the gas invasion occurrence time, s; is the porosity of the reservoir, dimensionless; c is the reservoir gas compressibility coefficient, dimensionless; r w is the borehole radius, m; γ is the Euler-Mascheroni constant (γ≈0.577);

[0129] After gas invasion occurs in deepwater open-circuit drilling, the wellbore is a gas-liquid multiphase flow process. The wellbore multiphase flow model is shown as follows:

[0130] Liquid mass conservation equation:

[0131]

[0132] Gas phase mass conservation equation:

[0133]

[0134] Gas-liquid two-phase momentum equation:

[0135]

[0136] In the formula, ρ l , g are respectively the liquid phase density and the gas phase density, kg / m 3 ; E l 、E g are the cross-sectional liquid content and cross-sectional gas content, dimensionless; A a is the cross-sectional area of ​​the annulus, m 2 ;v l 、v g are the annular liquid velocity and annular gas velocity, m / s; t is the time of gas invasion, s; z is the axial distance from the wellhead, m; P a is the wellbore annulus pressure, MPa; P fa is the annular friction, MPa; q g is the gas flow rate in the annulus, m 3 / s, at the bottom boundary of the wellbore, q g Equal to Q calculated by formula (9) gd , that is, Q gd is the bottom hole input boundary condition of the gas phase mass conservation equation;

[0137] Formulas (10), (11), and (12) are solved together to obtain the key instantaneous flow parameters in the wellbore, including the wellbore annulus pressure P a , cross-sectional air content E g , annular air phase velocity v g ;

[0138] The gas invasion rate at the mud line calculated by the model is:

[0139]

[0140] In the formula, Q ca is the gas invasion rate at the mudline calculated by the model, m 3 / s; N ml is the well depth node at the mudline, dimensionless; Δh is the spatial step length, m;

[0141] At the same time, according to the drilling fluid return height H(x), distance x and formulas (1) to (3) obtained by seabed ROV observation, the flow rate v of the return drilling fluid can be obtained: m ;

[0142] Then, according to formula (14), the annular air phase velocity v in the return drilling fluid can be obtained g :

[0143] ν m =v g E g +ν l (1-E g ) (14)

[0144] Then, according to formula (15), the gas invasion rate of deepwater shallow open-circuit drilling calculated by seabed ROV measured data can be obtained:

[0145] Q g =v g A a E g (15)

[0146] Among them, Q g is the drilling gas invasion rate calculated from the actual data measured by the seabed ROV, m 3 / s; A a is the cross-sectional area of ​​the annulus, m 2 ;

[0147] Combining formulas (1) to (3), (14), and (15), the gas intrusion rate is derived as:

[0148]

[0149] Preferably, in step (2), Q ca With Q g , and the calculation error ε is obtained:

[0150] ε=|Q ca -Q g | (17)

[0151] Then, the bisection method is used to converge the model to calculate the results: If the calculated value of the mudline gas invasion rate Q ca Less than the calculated value Q from seabed ROV observation g , which indicates that the assumed formation pressure P e ′ is too small, at this time, e ′Add ΔP processing, ΔP is between 0.1 and 3 MPa, and the new assumed formation pressure P is obtained e1 ', and then repeat the above steps until Q ca Equal to Q g ;

[0152] If the calculated value of mud line gas invasion rate is Q ca Greater than the calculated value Q from seabed ROV observation g , which indicates that the assumed formation pressure P e If ′ is too large, the new formation pressure can be directly assumed by equation (18):

[0153] The next assumed formation pressure P en 'for:

[0154]

[0155] Until Q ca With Q g If the error condition is met, the formation pressure P is obtained. e .

[0156] Through the above calculation and analysis, the gas invasion rate and formation pressure at the bottom of the well during deep-water shallow drilling can be obtained, thereby laying the foundation for the design of the well-killing fluid parameters required for bottom hole pressure control in step (3).

[0157] Example 5

[0158] A method for quickly regulating bottom hole pressure after overflow in deep-water shallow open-circuit drilling is as described in Example 4, except that, in step (3), once gas invasion occurs during deep-water shallow open-circuit drilling, bottom hole pressure control measures should be taken immediately to prevent the gas invasion from further deteriorating and evolving into a serious well kick or even a blowout accident. In the process of bottom hole pressure control, the density and displacement of the well killing fluid are the two most critical parameters for controlling gas invasion and regulating bottom hole pressure. Since it takes a certain amount of time to configure the well killing fluid with the required density for well killing, the displacement of the drilling fluid / well killing fluid should be increased first to increase the bottom hole pressure to reduce the amount of bottom hole gas invasion, which is achieved by controlling the power of the drilling fluid injection pump; when the well killing fluid with the required density is configured, the bottom hole pressure is controlled in combination with the injection of new well killing fluid and displacement control.

[0159] When gas invasion occurs in deepwater shallow open-circuit drilling, the annular flow friction can be increased by increasing the drilling / killing fluid displacement, thereby increasing the bottom hole pressure, thereby reducing gas invasion and balancing the formation pressure. The required killing fluid displacement calculation method is:

[0160]

[0161] Where, d h is the diameter of the annular flow section, m; P e is the formation pressure of the deep water shallow layer, Pa; P wh is the hydrostatic pressure of seawater, Pa; ρ l is the mixed density of drilling fluid during well drilling, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; h is the vertical depth of the mud line from the bottom of the well, m; f is the friction coefficient, dimensionless; L is the depth of the well below the mud line, m; Q L is the drilling fluid displacement, m 3 / min; Q s is the maximum displacement allowed by the drilling equipment, m 3 / min; P c is the minimum value of bottom hole fracture pressure and leakage pressure, Pa;

[0162] At the same time, the density of the injected killing fluid is increased to increase the gravity of the liquid column in the annulus. As the higher density killing fluid is injected from the drill pipe into the bottom of the well, the bottom hole pressure gradually increases with the friction effect exerted by the increased displacement, and the gas invasion volume at the bottom of the well will gradually decrease. In order to achieve successful well killing, according to the formation pressure obtained above, the required mixing density of the killing fluid is calculated by the following relationship:

[0163]

[0164] In the formula, ρ a is the density of seawater, kg / m 3 ;h swis the water depth at the seabed mudline, m; h is the vertical depth of the mudline from the bottom of the well, m; ρ l is the mixed density of drilling fluid during well drilling, kg / m 3 ;P p is the bottom hole fracture pressure, Pa;

[0165] When the required killing fluid is configured, the bottom hole pressure is jointly regulated by injecting killing fluid and controlling the killing fluid displacement to control the bottom hole gas invasion and balance the formation pressure. At the same time, during the well killing process, the return of the seabed drilling fluid is monitored by the seabed ROV to analyze the gas invasion control situation in real time until the bottom hole gas invasion is completely controlled. The seabed ROV can be used to observe whether there is gas in the returned drilling fluid to judge whether there is gas. The absence of gas means that the gas invasion has been effectively controlled.

[0166] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for quickly regulating bottom hole pressure after overflow in deepwater shallow open-circuit drilling, characterized in that: The method is realized by a rapid control device for bottom hole pressure after overflow of deep-water shallow open-circuit drilling, which includes a real-time monitoring device and a real-time control device. The real-time monitoring device includes a submarine ROV, a data transmission optical cable and a computer processing center. The submarine ROV is placed at the submarine wellhead through a traction rope, and is used to take real-time images of the return of drilling fluid from the submarine wellhead; the traction rope connects the submarine ROV to the platform, and the submarine ROV is connected to the computer processing center through a data transmission optical cable, and the data transmission optical cable is tied to the traction rope; the computer processing center receives the return images of drilling fluid taken by the submarine ROV in real time, and analyzes the shape and height of the returned drilling fluid in real time; The real-time control device comprises a signal receiving and executing mechanism, a drilling fluid injection pump, a mud pool and a drilling fluid injection pipeline. One end of the signal receiving and executing mechanism is connected to a computer processing center, and the other end is connected to the drilling fluid injection pump; the drilling fluid injection pump is connected to the mud pool and connected to the seabed wellhead through the drilling fluid injection pipeline; The drilling fluid injection pipeline is provided with a valve, a pressure sensor and a temperature sensor A, the mud pool is connected to a temperature sensor B, and the pressure sensor, the temperature sensor A and the temperature sensor B are all connected to a computer processing center; A method for quickly regulating bottom hole pressure after overflow in deepwater shallow open-circuit drilling comprises the following steps: (1) Subsea ROV monitors the return of drilling fluid from the subsea wellhead in real time The ROV installed on the seabed monitors the return of drilling fluid from the seabed wellhead in real time, and transmits the captured images of the return of drilling fluid to the computer processing center of the platform in real time. The computer processing center uses image processing technology to analyze the return flow morphology parameters of the drilling fluid in real time. (2) Real-time calculation of bottom hole gas invasion rate and formation pressure Combined with the drilling fluid return conditions photographed by the seabed ROV, the bottom hole gas invasion rate and formation pressure are calculated based on the obtained drilling fluid return flow morphology parameters; (3) Rapid response and control of bottom hole pressure According to the calculated bottom hole gas invasion rate and formation pressure, the key parameters of the killing fluid density and displacement required to handle overflow and regulate the bottom hole pressure are designed, and the start and stop and injection power of the drilling fluid injection pump are controlled. At the same time, the required killing fluid is configured on the platform, and the killing fluid is injected into the bottom hole in time to regulate the bottom hole pressure to control gas invasion, and the gas invasion control situation is analyzed in real time through seabed ROV monitoring; In step (1), the drilling fluid return flow morphology parameters include the distance x between the return drilling fluid position and the drilling fluid return center and the drilling fluid return height H(x); The computer processing center obtains the distance x between the return drilling fluid position and the return drilling fluid center through image processing technology. The flow pattern of the return drilling fluid in deepwater open circuit drilling conforms to the normal distribution function: Where H(x) is the drilling fluid return height, m; x is the distance between the return drilling fluid position and the drilling fluid return center, m; a is the square root of the variance of x, m; b is the expected distance value, m; The maximum height of drilling fluid return under no gas invasion conditions is calculated by the following formula: In the formula, H max is the maximum height of drilling fluid return, m; d is the equivalent diameter of the return outlet, m; g is the gravitational acceleration, m / s 2 ; ρ is the drilling fluid density, / cm 3 ρ a is the density of seawater, g / cm 3 ;v m is the flow rate of the return drilling fluid, m / s; The maximum height of drilling fluid return under gas invasion conditions is calculated by the following formula:

2. The method for rapid regulation of bottom hole pressure after overflow in deepwater shallow open-circuit drilling according to claim 1 is characterized in that: In step (2), before the gas invades the wellbore, the wellbore is a single-phase flow of drilling fluid, so the initial bottom hole annular pressure is calculated by the following formula: P wf =P c +ρgh+ΔP fa (4) Where P wf is the annular pressure at the bottom of the well, MPa; P c is the seabed wellhead pressure, MPa; P fa is the annular friction of single-phase flow, MPa; ρ is the drilling fluid density, kg / m 3 ; h is the vertical depth of the well below the mud line, m; According to the Reynolds number, the flow state in the wellbore is divided into laminar flow and turbulent flow. When Re<2100, the flow state of the drilling fluid is laminar flow; when Re≥2100, the flow state of the drilling fluid is turbulent flow. Under different drilling fluid flow states, the rock carrying performance of the drilling fluid is different, and the annular friction pressure loss ΔP fa Also different; The Reynolds number is calculated as follows: In the formula, v l is the annular drilling fluid velocity, m / s; d is the annular equivalent diameter, m; μ p is the plastic viscosity, Pa·s; Under laminar flow conditions, the calculation formula for annular friction pressure loss is as follows: Where, τ0 is the dynamic shear force, MPa; d a is the inner diameter of the annulus, m; d po is the outer diameter of the drill string, m; Under turbulent conditions, the calculation formula for annular friction pressure loss is as follows: Where f is the friction coefficient, dimensionless, and is calculated by formula (8): When the annular pressure P is obtained, wf Then, the bottom well gas invasion rate is calculated by the formation productivity equation: In the formula, Q gd is the bottom hole gas invasion rate, m 3 / s; K g is the gas permeability in the formation, μm 2 ;P e ′ is the assumed formation pressure, MPa; h r is the thickness of the open reservoir, m; μ g is the gas dynamic viscosity, Pa·s; S is the skin coefficient, dimensionless; t is the gas invasion occurrence time, s; is the porosity of the reservoir, dimensionless; c is the reservoir gas compressibility coefficient, dimensionless; r w is the borehole radius, m; γ is the Euler-Mascheroni constant; After gas invasion occurs in deepwater open-circuit drilling, the wellbore is a gas-liquid multiphase flow process. The wellbore multiphase flow model is shown as follows: Liquid mass conservation equation: Gas phase mass conservation equation: Gas-liquid two-phase momentum equation: In the formula, ρ l , g are respectively the liquid phase density and the gas phase density, kg / m 3 ; E l 、E g are the cross-sectional liquid content and cross-sectional gas content, dimensionless; A a is the cross-sectional area of ​​the annulus, m 2 ;v l 、v g are the annular liquid velocity and annular gas velocity, m / s; t is the time of gas invasion, s; z is the axial distance from the wellhead, m; P a is the wellbore annulus pressure, MPa; P fa is the annular friction, MPa; q g is the gas flow rate in the annulus, m 3 / s, at the bottom boundary of the wellbore, q g Equal to Q calculated by formula (9) gd ; Formulas (10), (11), and (12) are solved together to obtain the key instantaneous flow parameters in the wellbore, including the wellbore annulus pressure P a , cross-sectional air content E g , annular air phase velocity v g ; The gas invasion rate at the mud line calculated by the model is: In the formula, Q ca is the gas invasion rate at the mudline calculated by the model, m 3 / s; N ml is the well depth node at the mudline, dimensionless; Δh is the spatial step length, m; At the same time, according to the drilling fluid return height H(x) obtained by seabed ROV observation, distance x and formulas (1) to (3), the return drilling fluid velocity v is obtained: m ; Then, according to formula (14), the annular air phase velocity v in the return drilling fluid is obtained: g : n m =n g E g +n l (1-E g ) (14) Then, according to formula (15), the gas invasion rate of deep-water shallow open-circuit drilling calculated by seabed ROV measured data is obtained: Q g =v g A a E g (15) Among them, Q g is the drilling gas invasion rate calculated from the actual data measured by the seabed ROV, m 3 / s; A a is the cross-sectional area of ​​the annulus, m 2 ; Combining formulas (1) to (3), (14), and (15), the gas intrusion rate is derived as:

3. The method for rapid regulation of bottom hole pressure after overflow in deepwater shallow open-circuit drilling according to claim 2 is characterized in that: In step (2), compare Q ca With Q g , and the calculation error ε is obtained: ε=|Q ca -Q g |(17) If the calculated value of mud line gas invasion rate is Q ca Less than the calculated value Q from seabed ROV observation g , which indicates that the assumed formation pressure P e ′ is too small, at this time, e ′ plus ΔP to obtain the new assumed formation pressure P e1 ', and then repeat the above steps until Q ca Equal to Q g ; If the calculated value of mud line gas invasion rate is Q ca Greater than the calculated value Q from seabed ROV observation g , which indicates that the assumed formation pressure P e If ′ is too large, the new formation pressure can be directly assumed by equation (18): The next assumed formation pressure P en 'for: Until Q ca With Q g If the error condition is met, the formation pressure P is obtained. e .

4. The method for rapid regulation of bottom hole pressure after overflow in deep-water shallow open-circuit drilling according to claim 3 is characterized in that: ΔP is between 0.1 and 3 MPa.

5. The method for rapid regulation of bottom hole pressure after overflow in deepwater shallow open-circuit drilling according to claim 4 is characterized in that: In step (3), since it takes time to prepare the well-killing fluid with the required density for well killing, the displacement of the drilling fluid / well-killing fluid should be increased first to increase the bottom hole pressure to reduce the amount of bottom hole gas invasion, which can be achieved by controlling the power of the drilling fluid injection pump; When the required density of well-killing fluid is prepared, the bottom hole pressure is controlled by combining the injection of new well-killing fluid and displacement regulation.

6. The method for rapid regulation of bottom hole pressure after overflow in deepwater shallow open-circuit drilling according to claim 5 is characterized in that: When gas invasion occurs in deepwater shallow open-circuit drilling, the annular flow friction can be increased by increasing the drilling / killing fluid displacement, thereby increasing the bottom hole pressure, thereby reducing gas invasion and balancing the formation pressure. The required killing fluid displacement calculation method is: Where, d h is the diameter of the annular flow section, m; P e is the formation pressure of the shallow layer in deep water, Pa; P wh is the hydrostatic pressure of seawater, Pa; ρ l is the mixed density of drilling fluid during well drilling, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; h is the vertical depth of the mud line from the bottom of the well, m; f is the friction coefficient, dimensionless; L is the depth of the well below the mud line, m; Q L is the drilling fluid displacement, m 3 / min; Q s is the maximum displacement allowed by the drilling equipment, m 3 / min; P c is the minimum value of bottom hole fracture pressure and leakage pressure, Pa; At the same time, the density of the injected killing fluid is increased to increase the gravity of the liquid column in the annulus. As the higher density killing fluid is injected from the drill pipe into the bottom of the well, the bottom hole pressure gradually increases with the friction effect exerted by the increased displacement, and the gas invasion volume at the bottom of the well will gradually decrease. In order to achieve successful well killing, the required mixing density of the killing fluid is calculated by the following relationship: In the formula, ρ a is the density of seawater, kg / m 3 ;h sw is the water depth at the seabed mud line, m; h is the vertical depth of the mud line from the bottom of the well, m;ρ l is the mixed density of drilling fluid during well drilling, kg / m 3 ;P p is the bottom hole fracture pressure, Pa; When the required killing fluid is configured, the bottom hole pressure is jointly regulated by injecting the killing fluid and controlling the killing fluid displacement to control the bottom hole gas invasion and balance the formation pressure. At the same time, during the well killing process, the seabed ROV is used to monitor the return of the seabed drilling fluid to analyze the gas invasion control situation in real time until the bottom hole gas invasion is completely controlled.

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