A method for optimizing cementing water cement displacement efficiency

Abstract

The present application belongs to the technical field of cementing of oil and gas wells, and particularly relates to a method for optimizing cementing displacement efficiency. The method comprises the following steps: according to the relevant data of a block, key factors affecting the displacement efficiency of similar wells in the block and the degree of influence are calculated and simulated by using a cementing professional displacement efficiency software; the cementing quality of previous similar wells in the block is analyzed statistically; and whether the design of cementing construction scheme of the well meets the requirement of displacement efficiency is judged by simulating and calculating the displacement efficiency by using the cementing professional software according to the conventional cementing construction design. The present application takes construction safety and improvement of displacement efficiency as the primary standard, prevents the problem of low displacement efficiency and poor cementing quality in the design of cementing construction, and recommends the reference standard of improving displacement efficiency, i.e. cement slurry filling concentration ≥ cement slurry concentration C min and residual concentration of drilling fluid ≤ drilling fluid concentration C max , which has strong practicability.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well cementing technology, and specifically relates to a method for optimizing cement displacement efficiency in cementing. Background Technology

[0002] Cement displacement efficiency directly affects the effective sealing of formations, the safety and lifespan of oil and gas wells, and has always been a key research area in cementing work, significantly impacting the oil and gas industry. However, to meet the needs of development and production, the number of irregularly shaped wells has increased dramatically, posing significant challenges to cementing. Cement flow is complex, dynamic equivalent density is high, construction pressure is high, and cement slurry displacement efficiency is low, making it difficult to form a good cement sheath seal. Cementing quality issues are quite prominent, therefore, improving cement displacement efficiency is a key aspect of cementing construction design.

[0003] Currently, a series of studies on cementing displacement efficiency have been conducted both domestically and internationally, and the results have provided guidance for cementing displacement design to some extent. For example: optimizing the slurry column structure and adopting a three-stage cement slurry density system to reduce wellbore fluid column pressure; enhancing the flushing effect of pre-cementing fluid on filter cake on the casing wall, casing annular mud cake, and residual drilling fluid to reduce slurry mixing and improve displacement efficiency; adjusting the injection and displacement rate to ensure annular return velocity of 1.2 m / s for turbulent displacement; Bensted J of University College London proposed using stable and high-quality APIG or H-grade cement for cementing; DOWELL developed a composite polymer cementing slurry system; and delayed cementing processes were adopted.

[0004] It is evident that current research findings and technologies only address one aspect or problem in cementing displacement, and no effective methods have been developed for comprehensively improving cementing displacement efficiency or optimizing cementing displacement design. The formulation of construction plans to improve cementing displacement efficiency requires identifying the key factors affecting displacement efficiency and their degree of influence based on the geology and drilling conditions of the specific block. This involves comprehensively optimizing various influencing parameters and developing feasible measures to address the problems of low displacement efficiency and poor cementing quality. Summary of the Invention

[0005] The purpose of this invention is to provide a method for optimizing cementing displacement efficiency in well cementing, thereby addressing the shortcomings of existing technologies. To achieve the above objective, this invention proposes a cementing construction scheme design method based on a combination of cementing quality statistics and cementing displacement efficiency software simulation calculations, comprising the following steps: (1) Collection of relevant data for the block; including: well structure, well inclination angle, well diameter, formation pressure, fracture pressure, completion casing structure, drilling fluid performance before cementing, performance and dosage of pre-filling fluid, performance and dosage of cement slurry, placement of centralizer, rated pressure and discharge capacity of cement pump truck.

[0006] (2) Based on relevant data of the block, statistical analysis and simulation calculation of key factors and their degree of influence on the displacement efficiency of similar wells in this block were performed using cementing displacement efficiency software, including: centralizer placement A, displacement rate B, drilling fluid rheology C, pre-flush fluid rheology D, lead slurry rheology E, cement slurry rheology F, pre-flush fluid usage G, etc., and sorted in a list from largest to smallest degree of influence. (3) Based on relevant data of the block, statistical analysis was conducted to determine the minimum filling concentration of cement slurry for sealing the annulus at the observation point, which was of medium or above, and the cement slurry concentration C was recorded as the cement slurry concentration. min The remaining maximum concentration of the drilling fluid, denoted as drilling fluid concentration C, is also considered. max ; (4) Based on the relevant data of the block and the actual design of the well, conduct conventional cement injection construction design; (5) Based on the conventional cementing construction design, the displacement efficiency is simulated and calculated using cementing software to determine whether the cementing construction scheme for the designed well meets the requirement that the cement slurry filling concentration ≥ cement slurry concentration C. min And the remaining concentration of drilling fluid ≤ the concentration of drilling fluid C max ; (6) Based on the simulation calculation results of the replacement efficiency, if the requirements are met, the original cement injection construction design can achieve the replacement efficiency requirements.

[0007] (7) Based on the simulation calculation results of the displacement efficiency, if the requirements are not met, select 3 to 4 factors in step (2) that can be adjusted to improve the displacement efficiency, adjust their parameter values ​​and perform numerical simulation calculation of the displacement efficiency of the design well. (8) Based on the simulation calculation results of the displacement efficiency after adjusting the parameters, determine whether the cement injection construction is safe; (9) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the cement injection construction is not safe, adjust the construction design parameters in step (7) until the cement injection construction safety is met; (10) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the construction is safe, determine whether the following conditions are met simultaneously: the simulated cement slurry filling concentration ≥ the cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max ; (11) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the construction is safe and the following conditions are met: the simulated cement slurry filling concentration ≥ the cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max The corresponding modification to the cement injection construction design is the design scheme for the cement injection construction of the well.

[0008] (12) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the construction is safe, but cannot simultaneously satisfy: the simulated cement slurry filling concentration ≥ cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max Repeat steps (7) to (12).

[0009] The beneficial effects of this invention are: (1) When designing the cement injection construction plan, construction safety and improving the replacement efficiency are the primary standards to prevent problems such as low replacement efficiency and poor cementing quality during the cement injection construction design.

[0010] (2) Based on the actual situation of cement injection in the block, the recommended reference standard for improving the replacement efficiency is cement slurry filling concentration ≥ cement slurry concentration C. min And the remaining concentration of drilling fluid ≤ the concentration of drilling fluid C max It has strong practicality.

[0011] (3) Existing technologies or methods only address individual problems of cement substitution, while the present invention comprehensively considers all factors and their impact on improving substitution efficiency.

[0012] (4) The present invention has a clear objective and is highly operable. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a method for optimizing cement displacement efficiency in well cementing proposed in this invention.

[0014] Figure 2 The W-well displacement efficiency cloud map and cement slurry concentration distribution map are shown in the example. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figure 1 This invention provides a technical solution: a method for optimizing cement displacement efficiency in well cementing, comprising: (1) Collection of relevant data for the block: well structure, well inclination angle, well diameter, formation pressure, rupture (loss) pressure, completion casing structure, drilling fluid performance before cementing, performance and dosage of pre-filling fluid, performance and dosage of cement slurry, placement of centralizer, rated pressure and discharge capacity of cement pump truck, and other cementing-related parameters. (2) Based on relevant data of the block, the key factors affecting cement displacement in this block and their degree of influence are simulated and calculated using cementing software, including: centralizer placement and degree of influence A, displacement volume and degree of influence B, drilling fluid rheology and degree of influence C, pre-flush fluid rheology and degree of influence D, lead slurry rheology and degree of influence E, cement slurry rheology and degree of influence F, pre-flush fluid usage and degree of influence G, etc., and sorted in a list from largest to smallest degree of influence; (3) Based on relevant data of the block, statistical analysis shows that the cement injection quality of this block reaches medium or above, and the minimum filling concentration of the cement grout in the sealing annulus at the observation point is denoted as cement grout concentration C. min The maximum remaining drilling fluid concentration is denoted as drilling fluid concentration C. max ; (4) Design a cement injection construction plan for the well based on relevant data of the block; (5) Based on the cement injection construction design parameters, through displacement efficiency simulation calculation, determine whether the cement injection construction scheme of the designed well meets the requirement that the cement slurry filling concentration ≥ cement slurry concentration C. min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max ; (6) Based on the simulation calculation results of the displacement efficiency, if the requirements are met, then the original cementing construction design in step (4) can achieve the displacement efficiency requirements. That is, the relevant technical parameters and measures to improve the displacement efficiency in the original cementing construction design are the "actual well cement injection construction plan".

[0017] (7) Based on the simulation calculation results of the displacement efficiency, if the requirements are not met, select 3 to 4 factors in step (2) that have a greater impact on the displacement efficiency and adjust their parameter values, including but not limited to changing the spacing of the centralizer, adjusting the rheological properties of the drilling fluid, rationally designing the rheological properties of the cement slurry and the isolation fluid, rationally designing the amount of pre-flush fluid and the additional amount of slurry, and performing numerical simulation calculation of the displacement efficiency of the design well. (8) Based on the displacement efficiency simulation calculation results after parameter adjustment, determine whether the cement injection construction is safe: based on the dynamic equivalent density of the wellbore, formation fracture pressure, formation collapse pressure, and maximum pump pressure. (9) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the cement injection construction is not safe, select the factors in step (7) to adjust the construction parameters until the construction safety is met; (10) Based on the displacement efficiency simulation calculation results after adjusting the parameters, if the cement injection construction is safe, determine whether the requirements in step (3) are met simultaneously, that is: the simulated cement slurry filling concentration ≥ cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max ; (11) Based on the simulation calculation results of the displacement efficiency after adjusting the parameters, if the cement injection construction is safe and meets the requirements in step (3): the simulated cement slurry concentration ≥ cement slurry concentration C min Drilling fluid concentration ≤ Drilling fluid concentration C max The original cement injection construction design was modified accordingly, resulting in a cement injection construction plan for the well.

[0018] (12) Based on the simulation calculation results of the displacement efficiency after adjusting the parameters, if the cement injection construction is safe, but cannot simultaneously meet the requirements in step (3): the simulated cement slurry concentration ≥ cement slurry concentration C min Drilling fluid concentration ≤ Drilling fluid concentration C max Repeat steps (7) to (12).

[0019] The effectiveness of this invention will be analyzed below in conjunction with practical applications.

[0020] The cementing displacement efficiency optimization method of this invention was applied in a certain location, resulting in high displacement efficiency and excellent cementing quality. A specific application example for well W is given below.

[0021] 1. Basic Information on Well W This well has a four-stage wellbore structure, with a fourth well section ranging from 4090 to 5340 meters. The drill bit is 152.4 mm, the liner is 114.3 mm, and the liner hanger is located at 4073 meters. Drilling fluid properties at completion: density r m =1.15g / cm 3 The flow index n = 0.80, and the consistency coefficient k = 0.20 Pa·s. n The dynamic shear stress YP = 7.0 Pa and the plastic viscosity PV = 40 mPa·s.

[0022] 2. The design process includes the following steps: (1) Well history data for this block; (2) Based on well history data, the key factors affecting cement injection in this block and their degree of influence are simulated and calculated as follows: centralizer placement and its degree of influence 17%, displacement rate and its degree of influence 9%, drilling fluid rheology and its degree of influence 8%, flushing fluid usage and its degree of influence 7%, slurry usage and its degree of influence 6%, isolation fluid rheology and its degree of influence 2%, and cement slurry rheology and its degree of influence 1.5%; (3) Based on well history data, statistical analysis shows that the cementing quality of this block reaches medium or above, and the minimum filling concentration of cement slurry in the annulus at the observation point is denoted as cement slurry concentration C. min =45.45%, the maximum remaining drilling fluid concentration, denoted as drilling fluid concentration C. max =1.12%; or cement slurry concentration C min =91.53%, the maximum remaining drilling fluid concentration, denoted as drilling fluid concentration C. max =8.42%; (4) Based on relevant data of the block, design the cement injection scheme for well W: the preliminary design flushing fluid is 1.00 g / cm³. 3 8.0m 3 Drilling fluid density: 1.45 g / cm³ 3 The flow index n = 0.80, and the consistency coefficient k = 0.20 Pa·s. n ; Isolation fluid 1.15g / cm 3 20m 3 ; Sterilization water 1.00g / cm 3 2.0m 3 The density of the cement slurry is 1.60 g / cm³. 3 12.0m 3 Additional 3.9m 3 Tailings density 1.88 g / cm³ 3 7.0m 3 , including an additional 4.0m 3 Replacement displacement 0.7m 3 / min; Centralizer placement: 5299m~5239m, add 1 integral elastic centralizer for every 2 sleeves; 4500m~4350m, add 1 integral elastic centralizer for every 4 sleeves; 4336m~4316m, add 1 integral elastic centralizer above and below the upper sleeve shoe; 4316m~4093m, add 1 integral elastic centralizer for every 6 sleeves; 4093m~4073m, 2 integral elastic centralizers below the hanger.

[0023] (5) Based on the parameters of the cement injection scheme design, determine whether the cement injection scheme for well W satisfies the requirement that the cement slurry filling concentration ≥ the cement slurry concentration C through numerical simulation calculation of displacement efficiency. min =45.45 and remaining drilling fluid concentration ≤ drilling fluid concentration C max =1.12; or cement slurry concentration C min =91.53%, the maximum remaining drilling fluid concentration, denoted as drilling fluid concentration C. max =8.42%; (6) Based on the displacement efficiency simulation results, it was found that the conditions in step (5) were not met. Therefore, the placement of the centralizer in step (2) was changed: 1 integral elastic centralizer was added for every 2 casings from 4500m to 4350m; 1 integral elastic centralizer was added for every 2 casings from 4316m to 4093m; and 1 integral elastic centralizer was added for every 4 casings in the remaining well sections. The drilling fluid rheology changed from the original flow index n=0.80 and consistency coefficient k=0.20Pa.s n Adjusted to n=0.85, k=0.15 Pa.s n The displacement replaced by the original 0.7m 3 / min, optimized and adjusted to 0.9m 3 / min. The additional amount of slurry added has been increased from the original 3.9m. 3 (Volume of upper cement plug) Adjusted to an additional 6.0m for the grout outlet. 3 To perform replacement efficiency simulation calculations; (7) Based on the simulation calculation results of the replacement efficiency after parameter adjustment, such as Figure 2 As shown, the dynamic equivalent density of the wellbore was found to be greater than the formation fracturing pressure, therefore cement injection was unsafe; the displacement rate in step (2) was adjusted from the original 0.9 m³ / s. 3 / min, optimized and adjusted to 0.8m 3 / min, to perform displacement efficiency simulation calculations; (8) Based on the simulation calculation results of the displacement efficiency after adjusting the parameters, it was found that the cement injection construction was safe and met the requirements in step (3), namely: the cement slurry filling concentration ≥ the cement slurry concentration C min =45.45 and remaining drilling fluid concentration ≤ drilling fluid concentration C max =1.12; (9) Based on the displacement efficiency simulation calculation results after adjusting the parameters, modify the original cement injection construction design accordingly, which is the design well cement injection construction scheme.

[0024] 3. Design results of the replacement construction scheme for Well W Preliminary design flushing fluid: 1.00 g / cm³ 3 8.0m 3 ; Isolation fluid 1.15g / cm 3 20m 3 ; Sterilization water 1.00g / cm 3 2.0m 3 The density of the cement slurry is 1.60 g / cm³. 3 12.0m 3 Additional 3.9m 3 Tailings density 1.88 g / cm³ 3 7.0m 3 , including an additional 6.0m3 Centralizer placement: 5299m~5239m, one integral elastic centralizer for every two casing sections; 4500m~4350m, one integral elastic centralizer for every two casing sections; 4336m~4316m, one integral elastic centralizer above and below the upper casing shoe; 4316m~4093m, one integral elastic centralizer for every two casing sections; 4093m~4073m, two integral elastic centralizers below the hanger; for other well sections, one integral elastic centralizer for every four casing sections; displacement rate: 0.8m³ / h. 3 / min.

[0025] 4. Numerical simulation displacement contour map of well W and CBL and VDL logging results of the design well According to CBL and VDL tests, the cementation quality of the first interface of well W is above average in 95.45% and above average in 94.49% of the second interface, indicating excellent cementing quality.

[0026] Based on the above technical solutions and implementation, it can be seen that, compared with existing technologies, the beneficial effects achieved by the method of the present invention are as follows: (1) When designing the cement injection construction plan, construction safety and improving the replacement efficiency were taken as the primary standards to prevent the problems of low replacement efficiency and poor cementing quality in cement injection construction.

[0027] (2) Based on the actual situation of cement injection in the block, the recommended reference standard for improving the replacement efficiency is cement slurry filling concentration ≥ cement slurry concentration C. min And the remaining concentration of drilling fluid ≤ the concentration of drilling fluid C max It has strong practicality.

[0028] (3) Existing technologies or methods only address individual problems of cementing displacement. This invention comprehensively considers all factors and their impact on improving the efficiency of cementing displacement.

[0029] (4) The present invention has a clear objective and is highly operable.

Claims

1. A method for optimizing cement displacement efficiency in well cementing, characterized in that, Includes the following steps: (1) Collection of relevant data on the block; (2) Based on relevant data of the block, statistical analysis and simulation calculation of key factors and their impact on the displacement efficiency of similar wells in this block were performed using cementing professional displacement efficiency software, and the results were listed in descending order of impact. (3) Based on relevant data of the block, statistical analysis shows that the cementing quality of similar wells in this block reached medium or above, and the minimum filling concentration of the cement slurry in the annulus at the test point is denoted as cement slurry concentration C. min The remaining maximum concentration of the drilling fluid, denoted as drilling fluid concentration C, is also considered. max ; (4) Based on the relevant data of the block and the actual design of the well, conduct conventional cement injection construction design; (5) Based on the conventional cementing construction design, the displacement efficiency is simulated and calculated using cementing software to determine whether the cementing construction scheme for the designed well meets the requirement that the cement slurry filling concentration ≥ cement slurry concentration C. min And the remaining concentration of drilling fluid ≤ the concentration of drilling fluid C max ; (6) Based on the simulation calculation results of the replacement efficiency, if the requirements are met, the original cement injection construction design has achieved the replacement efficiency requirements; (7) Based on the simulation calculation results of the displacement efficiency, if the requirements are not met, select 3 to 4 factors in step (2) that can be adjusted to improve the displacement efficiency, adjust their parameter values ​​and perform numerical simulation calculation of the displacement efficiency of the design well. (8) Based on the simulation calculation results of the displacement efficiency after adjusting the parameters, determine whether the cement injection construction is safe; (9) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the cement injection construction is not safe, adjust the construction design parameters in step (7) until the cement injection construction safety is met; (10) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the construction is safe, determine whether the following conditions are met simultaneously: the simulated cement slurry filling concentration ≥ the cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max ; (11) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the construction is safe and the following conditions are met: the simulated cement slurry filling concentration ≥ the cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max The corresponding modification to the cement injection construction design is the design well cement injection construction design scheme. (12) Based on the simulation calculation results of the replacement efficiency after adjusting the parameters, if the construction is safe, but cannot simultaneously satisfy: the simulated cement slurry filling concentration ≥ cement slurry concentration C min And the remaining drilling fluid concentration ≤ drilling fluid concentration C max Repeat steps (7) to (12).

2. The method for optimizing cement displacement efficiency in well cementing according to claim 1, characterized in that, The relevant data for the block includes: well structure, well inclination angle, well diameter, formation pressure, fracture pressure, completion casing structure, drilling fluid properties before cementing, pre-fill fluid properties and dosage, cement slurry properties and dosage, centralizer placement, and rated pressure and discharge capacity of the cement pump truck.

3. The method for optimizing cement displacement efficiency in well cementing according to claim 1, characterized in that, Key factors for similar well displacement efficiency in step (2) include: centralizer placement (A), displacement rate (B), drilling fluid rheology (C), pre-flush fluid rheology (D), cement slurry rheology (F), and pre-flush fluid usage (G).

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