A design method of a cementing annular slurry column

Abstract

The present application relates to a kind of design methods of cementing annular slurry column, comprising the following steps: 1) collecting the leakage parameter of the weakest formation in the formation to be cemented, the leakage parameter of the second weakest formation, the bottom hole leakage parameter and the maximum formation pressure parameter;2) calculate the maximum pressure bearing parameter at the weakest formation when cementing operation is bumped, the maximum pressure bearing parameter at the second weakest formation when cementing operation is bumped, the maximum pressure parameter that bottom hole bears when cementing operation is bumped and the bottom hole pressure parameter when tail slurry gelatinization loses weight during cementing operation;3) according to the leakage parameter of the weakest formation, the leakage parameter of the second weakest formation, the bottom hole leakage parameter and the maximum formation pressure parameter, the maximum pressure bearing parameter at the weakest formation when cementing operation is bumped, the maximum pressure bearing parameter at the second weakest formation when cementing operation is bumped, the maximum pressure parameter that bottom hole bears when cementing operation is bumped and the bottom hole pressure parameter when tail slurry gelatinization loses weight during cementing operation, it is judged whether annular slurry column is designed reasonably.

Description

TECHNICAL FIELD

[0001] The application relates to a design method of a well cementing annular slurry column, and belongs to the field of well cementing for oil and gas development. BACKGROUND

[0002] In a well cementing process, slurry such as preflush and cement slurry in an annular space between a casing and a well wall forms a well cementing annular slurry column structure, and the design of the annular slurry column structure is a key link of well cementing design. The static liquid column pressure of the annular slurry column is different due to the different densities and heights of various slurry in the annular slurry column. In the well cementing construction process, the annular friction will cause a pressure on the formation. In the cement slurry setting process, the cement slurry will lose weight due to the hydration process, resulting in a decrease in the static liquid column pressure, and thus a decrease in the pressure on the formation. When the pressure of the annular slurry column on the formation is greater than the fracture pressure, cement slurry loss will occur, resulting in insufficient cement slurry return or pollution of the oil layer. When the pressure of the annular slurry column on the oil and gas layer is less than the formation pressure of the oil and gas layer, oil and gas channeling will occur, resulting in poor well cementing quality. Therefore, the structure of the annular slurry column, i.e. the number, density, height and vertical depth of the annular slurry column, should be reasonably designed.

[0003] With the advancement of oil and gas resource exploration and development process, the wellbore conditions of oil and gas wells are becoming more and more complex, especially the number of low-pressure and easy-leakage wells is increasing. Cement slurry return is insufficient, the formation is leaked, and the production layer is not pressure-stabilized due to well leakage, and other well cementing complex situations occur frequently. The well cementing of low-pressure and easy-leakage wells puts forward higher requirements for the rationality of the design of the well cementing annular slurry column structure, and the design of the well cementing annular slurry column of oil and gas wells involving multiple low-pressure and easy-leakage formations is more stringent. Therefore, for the well cementing of oil and gas wells involving multiple low-pressure and easy-leakage formations, it is of great significance to design a reasonable well cementing annular slurry column structure to ensure the cement return, pressure-stabilize the oil and gas layer and improve the well cementing quality.

[0004] The existing published design methods of the well cementing annular slurry column structure mainly consider the influence of well leakage and cement slurry gelation weight loss on the slurry column structure, but ignore the influence of low-pressure and easy-leakage formations and annular friction on the well cementing quality. The patent with the application number 201510708655.9 discloses a design method of the well cementing annular slurry column structure considering the maximum and minimum pressures of the annular slurry column on the target layer, and the minimum leakage pressure of the formation is considered in the design process. The patent with the application number 201710114315.2 discloses a design method of the slurry column structure considering the density and length of each slurry in the annulus, and the slurry column structure is determined in combination with the pore pressure and the minimum leakage pressure. However, the above methods only consider a single leakage layer in the well cementing operation, and do not involve the well cementing leakage prevention problem of multiple low-pressure and easy-leakage formations. SUMMARY

[0005] The application aims to provide a design method of a cementing annular slurry column to solve the lost circulation problem in cementing of multiple low-pressure and easy-to-lose formations.

[0006] To achieve the above-mentioned purpose, the application provides a design method of a cementing annular slurry column.

[0007] The design method of the cementing annular slurry column comprises the following steps.

[0008] 1) collecting lost circulation parameters of the weakest formation, lost circulation parameters of the second weakest formation, bottom hole lost circulation parameters and maximum formation pressure parameters of the formations to be cemented;

[0009] 2) calculating maximum pressure bearing parameters of the weakest formation at the time of pressure bumping in cementing operation, maximum pressure bearing parameters of the second weakest formation at the time of pressure bumping in cementing operation, maximum pressure parameters of the bottom hole at the time of pressure bumping in cementing operation and bottom hole pressure parameters at the time of cement slurry gelation weight loss in cementing operation;

[0010] 3) judging whether the annular slurry column is designed reasonably according to the lost circulation parameters of the weakest formation, the lost circulation parameters of the second weakest formation, the bottom hole lost circulation parameters and the maximum formation pressure parameters, the maximum pressure bearing parameters of the weakest formation at the time of pressure bumping in cementing operation, the maximum pressure bearing parameters of the second weakest formation at the time of pressure bumping in cementing operation, the maximum pressure parameters of the bottom hole at the time of pressure bumping in cementing operation and the bottom hole pressure parameters at the time of cement slurry gelation weight loss in cementing operation.

[0011] The beneficial effects of the method are as follows: the parameters of the formations to be cemented are collected, the length and density of the working fluid in the cementing are determined, the calculated results are compared with the known formation parameters, and it is determined that the annular slurry column structure design is reasonable. The annular fluid column involved in the cementing operation is quantitatively calculated, the cementing cement return height is ensured, the oil and gas layers are stabilized, the lost circulation of multiple low-pressure and easy-to-lose formations is avoided, and the effective formation cementing is achieved.

[0012] Further, in step 3), the method for judging whether the annular slurry column is designed reasonably is as follows:

[0013] When the following four conditions are met at the same time, it is determined that the annular slurry column is designed reasonably:

[0014] The maximum pressure bearing parameter of the weakest formation at the time of pressure bumping in cementing operation is less than the lost circulation parameter of the weakest formation;

[0015] The maximum pressure bearing parameter of the second weakest formation at the time of pressure bumping in cementing operation is less than the lost circulation parameter of the second weakest formation;

[0016] The maximum pressure parameter of the bottom hole at the time of pressure bumping in cementing operation is less than the bottom hole lost circulation parameter;

[0017] The well bottom pressure parameter when the tail slurry gels and loses weight during the cementing operation is greater than the maximum formation pressure parameter.

[0018] The beneficial effect of this is that the weakest formation and the sub-weakest formation leakage pressures and corresponding equivalent densities are considered, and the maximum pressures of the weakest formation and the sub-weakest formation when pressure bumping during the cementing operation and corresponding equivalent densities are considered, the cementing process improves the leakage prevention effect of multiple low-pressure leaky formations, and is beneficial to improving the cementing quality.

[0019] Further, the formation leakage parameters of the weakest formation, the leakage parameters of the sub-weakest formation, the well bottom leakage parameters, the maximum formation pressure parameters, the maximum pressure bearing parameters of the weakest formation when pressure bumping during the cementing operation, the maximum pressure bearing parameters of the sub-weakest formation when pressure bumping during the cementing operation, the maximum pressure parameters of the well bottom when pressure bumping during the cementing operation, and the well bottom pressure parameters when the tail slurry gels and loses weight during the cementing operation are expressed by corresponding equivalent densities.

[0020] Further, the calculation method of the maximum pressure bearing parameter of the weakest formation when pressure bumping during the cementing operation is:

[0021] ρ 地1承压 =ρ 地1环空 +ρ 摩阻地1

[0022] ρ 地1承压 is the equivalent density corresponding to the maximum pressure bearing parameter of the weakest formation when pressure bumping during the cementing operation, ρ 地1环空 is the equivalent density corresponding to the maximum annulus fluid column pressure parameter of the weakest formation when pressure bumping during the cementing operation, and ρ 摩阻地1 is the equivalent density corresponding to the friction parameter of the weakest formation during the cementing operation.

[0023] Further, the calculation method of the maximum pressure bearing parameter of the sub-weakest formation when pressure bumping during the cementing operation is:

[0024] ρ 地2承压 =ρ 地2环空 +ρ 摩阻地2

[0025] ρ 地2承压 is the equivalent density corresponding to the maximum pressure bearing parameter of the sub-weakest formation when pressure bumping during the cementing operation, ρ 地2环空 is the equivalent density corresponding to the maximum annulus fluid column pressure parameter of the sub-weakest formation when pressure bumping during the cementing operation, and ρ 摩阻地2 is the equivalent density corresponding to the friction parameter of the sub-weakest formation during the cementing operation.

[0026] Further, the calculation method of the maximum pressure parameter of the well bottom when pressure bumping during the cementing operation is:

[0027] ρ 井底 =ρ 环空 +ρ摩阻

[0028] p 井底 ρ 环空 ρ 摩阻 ρ

[0029] Further, ρ 地1环空 The calculation method of ρ

[0030]

[0031] m is the number of different density fluids in the annulus above the weakest formation, ρ j ρ j h is the vertical depth of the jth section of annulus fluid, h is the vertical depth of the weakest formation, and g is the gravitational acceleration constant, j ∈ (1, m) ;

[0032] ρ 摩阻地1 The calculation method of ρ

[0033]

[0034] m is the number of different density fluids in the annulus above the weakest formation, ρ j ρ j h is the vertical height of the jth section of annulus fluid, V is the return velocity of the annulus fluid, D D D T is the casing outer diameter, h is the vertical depth of the weakest formation, and g is the gravitational acceleration constant, j ∈ (1, m) ;

[0035] ρ 地2环空 The calculation method of ρ

[0036]

[0037] m' is the number of different density fluids in the annulus above the second weakest formation, ρ k ρ k h' is the vertical height of the kth section of annulus fluid, h' is the vertical depth of the second weakest formation, and g is the gravitational acceleration constant, k ∈ (1, m') ;

[0038] ρ 摩阻地2 The calculation method of ρ

[0039]

[0040] m' is the number of different density fluids in the annulus above the second weakest formation, ρk Let h' be the density of the annular fluid in the k-th segment. k Let V be the vertical height of the annular fluid in the k-th segment, V be the return velocity of the annular fluid, and D be the vertical height of the annular fluid. D D is the wellbore diameter. T Where is the outer diameter of the casing, h' is the vertical depth at the weakest stratum, g is the gravitational acceleration constant, and k∈(1,m');

[0041] ρ 环空 The calculation method is as follows:

[0042]

[0043] n is the number of fluids of different densities in the annulus, ρ i Let L be the density of the fluid in the i-th segment of the annulus. i Let L be the vertical height of the i-th segment of the annulus fluid, L be the vertical depth of the construction well, g be the gravitational acceleration constant, and i∈(1,n).

[0044] ρ 摩阻 The calculation method is as follows:

[0045]

[0046] n is the quantity of fluids of different densities in the annulus, f is the friction coefficient, and ρ i Let L be the density of the fluid in the i-th segment of the annulus. i Let V be the length of the i-th segment of the annulus, V be the return velocity of the annulus, and D be the length of the i-th segment of the annulus. D D is the wellbore diameter. T Let L be the outer diameter of the casing, L be the vertical depth of the construction well, g be the gravitational acceleration constant, and i ∈ (1, n).

[0047] Furthermore, the calculation method for the bottom hole pressure parameters during tailings gelation and weight loss in cementing operations is as follows:

[0048]

[0049] ρ 终了 P is the equivalent density at the bottom hole pressure corresponding to the gelation and weight loss of the tailings during cementing operations. 环空 ΔP represents the annular fluid column pressure parameter during cementing operations, and ΔP represents the pressure loss parameter caused by the gelation and weight loss of the tailings slurry.

[0050] Furthermore, the calculation method for ΔP is as follows:

[0051] ΔP = max(ΔP1, ΔP2)

[0052]

[0053] P SGS L represents the static cementitious strength of the cement paste. Cis the vertical length of the tail slurry section; D D is the well diameter; D T is the outer diameter of the casing;

[0054] ΔP2 = ρgL C

[0055] ρ is the density of clear water, 1.0 g / cm 3 ; g is the gravitational acceleration constant; L C is the vertical length of the tail slurry section.

[0056] The beneficial effect of doing so is that the cementing annular slurry column design method considers not only the annular friction, the formation pore pressure, the leak-off prevention of the weakest formation and the pressure loss of the cement slurry during the gelation weight loss process, but also the leak-off prevention of the less weak formation, and is especially suitable for cementing pressure stabilization leak-off prevention design in the presence of multiple low-pressure leak-off formations, so that the design method is more scientific and reasonable. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 is the implementation step of the cementing annular slurry column design method. DETAILED DESCRIPTION

[0058] The present application will be further described in detail below with reference to the accompanying drawings.

[0059] Example:

[0060] The present application provides a cementing annular slurry column design method, which solves the problem of difficult annular slurry column structure design caused by multiple leak-off formations, avoids cementing leak-off caused by unreasonable slurry column structure design, and further ensures that cementing construction meets design requirements.

[0061] As Figure 1 shown, the method comprises the following steps:

[0062] 1) Collecting formation parameters of key formations:

[0063] According to the actual situation, collect formation parameters in the formation that needs to be cemented, and the formation parameters to be cemented include: the leak-off parameters of the weakest formation, the leak-off parameters of the less weak formation, the leak-off parameters of the bottom of the well, and the maximum formation pressure parameters:

[0064] The leak-off pressure P 地1漏失 of the weakest formation and the corresponding equivalent density ρ 地1漏失 ;

[0065] The leak-off pressure P 地2漏失 of the less weak formation and the corresponding equivalent density ρ 地2漏失 ;

[0066] The maximum formation pressure P 孔隙 of the sealed reservoir and the corresponding equivalent density ρ 孔隙 ;

[0067] bottom hole pressure of the sealed formation 漏失 and the corresponding equivalent density p 漏失 .

[0068] Formation leakage pressure refers to the pressure at which drilling fluid leaks at a certain depth. Formation leakage pressure is usually used as the basis for determining well control operation cementing pressure, which is more secure. In determining the formation leakage pressure, the prediction method and verification method are usually used to obtain the formation leakage pressure value.

[0069] Formation pressure, also known as formation pore pressure, refers to the pressure acting on the fluid (oil, gas, water) in the formation pore. The formation pressure is usually represented by the formation pressure gradient. The formation pressure is proportional to the formation pressure gradient, and the ratio of the formation pressure to the formation pressure gradient is constant. For a certain area, the formation pressure gradient of the area is a fixed value because the formation water density is constant.

[0070] 2) Determine the annular length and density of each cementing working fluid:

[0071] Determine the cementing section of the leading slurry, intermediate slurry, and tail slurry and the density of the cement slurry during cementing. The densities of the leading slurry, intermediate slurry, and tail slurry generally follow p 领浆 <p 中间浆 <p 尾浆 Determine the working fluid density and section length of each section above the thinnest formation 1 and the thinnest formation 1, and the working fluid density and section length of each section above the thinnest formation 2 and the thinnest formation 2. The cementing cement slurry density of the annular slurry column designed by the present application can be adjusted.

[0072] 3) Calculate the pressure and equivalent density under different conditions during cementing operation:

[0073] The method for calculating the maximum pressure parameter at the thinnest formation during cementing operation, the maximum pressure parameter at the second thinnest formation during cementing operation, the maximum pressure parameter at the bottom hole during cementing operation, and the bottom hole pressure parameter when the tail slurry gels during cementing operation is as follows:

[0074] ① Calculate the maximum pressure parameter at the bottom hole during cementing operation, i.e. the equivalent density p 井底 (equivalent density: the density of the fluid in the well required to balance the pressure value at a certain depth in the well):

[0075] p 井底 = p 环空 + p 摩阻

[0076] The equivalent density ρ of the annular fluid column pressure parameter during cementing operations 环空 The calculation method is as follows:

[0077]

[0078] Where n is the number of fluids of different densities in the annulus; ρ i L represents the density of the fluid in the i-th segment of the annulus; i denoted as , where is the vertical height of the annular fluid in the i-th segment; L is the vertical depth of the construction well; g is the gravitational acceleration constant; i∈(1,n).

[0079] Equivalent density ρ corresponding to friction parameters during cementing operations 摩阻 The calculation method is as follows:

[0080]

[0081] Where f is the friction coefficient; ρ i L represents the density of the fluid in the i-th segment of the annulus. i Let be the length of the i-th segment of the annular fluid; V be the return velocity of the annular fluid; D be the length of the i-th segment of the annular fluid. D D is the wellbore diameter; T denoted as the outer diameter of the casing; L as the vertical depth of the construction well; g as the gravitational acceleration constant; i∈(1,n).

[0082] ρ 摩阻 It can also be determined by combining on-site experience and formulas.

[0083] ② Calculate the maximum bearing capacity parameter at the weakest formation during cementing operations, i.e., the equivalent density ρ corresponding to the maximum bearing capacity at the weakest formation during cementing operations. 地1承压 :

[0084] ρ 地1承压 =ρ 地1环空 +ρ 摩阻地1

[0085] The equivalent density ρ corresponding to the maximum annular fluid column pressure parameter at the weakest formation during cementing operations. 地1环空 Calculation method:

[0086]

[0087] Where m represents the amount of fluids of different densities in the annulus above the weakest stratum; ρ j h is the density of the annular fluid in the j-th segment; j denoted as , where is the vertical height of the annular fluid in the j-th segment; h is the vertical depth at the weakest stratum; g is the gravitational acceleration constant; j∈(1,m).

[0088] Equivalent density ρ corresponding to the friction parameter in the weakest formation during cementing operations 摩阻地1The calculation method of the equivalent density ρ

[0089]

[0090] wherein f is the friction coefficient; m is the number of different density fluids in the annulus above the thinnest formation; ρ j is the density of the jth section of annulus fluid; h j is the vertical height of the jth section of annulus fluid; V is the return velocity of the annulus fluid; D D is the borehole diameter; D T is the casing outer diameter; h is the vertical depth of the thinnest formation; g is the gravitational acceleration constant; j ∈ (1, m).

[0091] ρ 摩阻地1 may also be determined by combining the field experience formula calculation.

[0092] 3. Calculate the maximum pressure-bearing parameter at the second thinnest formation when the cementing operation encounters pressure, i.e. the equivalent density ρ 地2承压 corresponding to the maximum pressure-bearing parameter at the second thinnest formation when the cementing operation encounters pressure.

[0093] ρ 地2承压 = ρ 地2环空 + ρ 摩阻地2

[0094] The calculation method of the equivalent density ρ 地2环空 corresponding to the maximum annulus fluid column pressure parameter at the second thinnest formation when the cementing operation encounters pressure is as follows:

[0095]

[0096] wherein m ’ is the number of different density fluids in the annulus above the second thinnest formation; ρ k is the density of the kth section of annulus fluid; h’ k is the vertical height of the kth section of annulus fluid; h’ is the vertical depth of the second thinnest formation; g is the gravitational acceleration constant; k ∈ (1, m’).

[0097] The calculation method of the equivalent density ρ 摩阻地2 corresponding to the friction value at the second thinnest formation when the cementing operation is performed is as follows:

[0098]

[0099] wherein f is the friction coefficient; m’ is the number of different density fluids in the annulus above the second thinnest formation; ρ k is the density of the kth section of annulus fluid; h’ k is the vertical height of the kth section of annulus fluid; V is the return velocity of the annulus fluid; D D is the borehole diameter; D TD is the casing outer diameter; h' is the vertical depth at the second weak formation; g is the gravity acceleration constant; k ∈ (1, m').

[0100] ρ 摩阻地2 The field experience formula can also be used for calculation and determination.

[0101] ④ Calculate the bottom hole pressure parameter when the tail slurry gel loses weight during cementing operation, that is, the equivalent density ρ 终了 of the bottom hole pressure corresponding to the tail slurry gel loss weight during cementing operation.

[0102]

[0103] Where g is the gravity acceleration constant; L is the vertical depth of the well.

[0104] The calculation method of the pressure loss parameter ΔP caused by the tail slurry gel loss weight is:

[0105] ΔP = max(ΔP1, ΔP2)

[0106]

[0107] Where P SGS is the static gel strength of the cement slurry; L C is the vertical length of the tail slurry section; D D is the well diameter; D T is the casing outer diameter.

[0108] ΔP2 = ρgL C

[0109] Where ρ takes the density of water, 1.0 g / cm 3 ; g is the gravity acceleration constant; L C is the vertical length of the tail slurry section.

[0110] 4) Determine whether the annular slurry column is designed reasonably:

[0111] According to ρ 井底 , ρ 漏失 , ρ 地1承压 , ρ 地1漏失 , ρ 地2承压 , ρ 地2漏失 , ρ 终了 and ρ 孔隙 , determine whether the cementing design meets the requirements of cementing pressure stabilization and leak protection, and further determine whether the cementing design method conforms to the design specification. Specifically, it includes:

[0112] ρ 井底 <ρ 漏失

[0113] ρ 地1承压 <ρ 地1漏失

[0114] p 地2承压 <ρ 地2漏失

[0115] p 终了 >ρ 孔隙

[0116] When the designed annular slurry column meets the above four conditions at the same time, it is judged that the annular slurry column structure design is reasonable.

[0117] The present application can quantitatively calculate, compare and optimize the working fluid structure involved in the annulus of the cementing operation, not only can determine the pressure stabilization of the reservoir, but also can avoid the loss of multiple low-pressure and easy-to-lose formations, and realize the effective cementing of the formation. Not only the annular friction, the formation pore pressure, the leak-off prevention of the thinnest formation and the pressure loss of the cement slurry in the gelatinization and weight loss process are considered, but also the leak-off prevention of the second thinnest formation is considered, especially suitable for the cementing pressure stabilization and leak-off prevention design of multiple low-pressure and easy-to-lose formations, the design method is more scientific and reasonable. The present application is also applicable to the cementing design of conventional pressure wells, high-pressure wells and various pressure systems coexisting oil and gas wells.

[0118] The following examples illustrate the method:

[0119] Example 1:

[0120] Well A, straight well, the completion depth is 3200m, the drilling fluid density before cementing is 1.22g / cm 3 , the formation pressure-bearing capacity in the development area of the well is weak and easy to lose, the equivalent density of the loss pressure of the thinnest formation is 1.32g / cm 3 , located at the well depth of 2500m, the equivalent density of the loss pressure of the second thinnest formation is 1.35g / cm 3 , located at the well depth of 1200m, the equivalent density of the loss pressure of the bottom hole is 1.60g / cm 3 , the oil and gas layer well section is 2800-3200m, the maximum pore pressure equivalent density of the oil and gas layer is 1.07g / cm 3 , it is required to be cemented to 200m above the producing layer, and a reasonable cementing annular slurry column structure is designed to realize one-time up-return full-well cementing.

[0121] Step 1: Determine the equivalent density of the key point.

[0122] 1.1 The equivalent density of the loss pressure of the thinnest formation is 1.32g / cm 3 ; the vertical depth is 2500m;

[0123] 1.2 The equivalent density of the loss pressure of the second thinnest formation is 1.35g / cm 3 ; the vertical depth is 1200m;

[0124] 1.3 The maximum formation pressure equivalent density of the reservoir 1.07 g / cm 3 ;

[0125] 1.4 The equivalent density of the bottom hole leakage pressure 1.60 g / cm 3 .

[0126] Step 2: Determine the length of the annular section of each cementing working fluid.

[0127] 2.1 Determine the tail slurry to seal 2600-3200 m, section length 600 m, tail slurry density 1.90 g / cm 3 ;

[0128] 2.2 Determine the intermediate slurry to seal 2400-2600 m, section length 200 m, intermediate slurry density 1.70 g / cm 3 ;

[0129] 2.3 Determine the lead slurry to seal 0-2400 m, section length 2400 m, lead slurry density 1.25 g / cm 3 ;

[0130] 2.4 Intermediate slurry to seal in the weakest formation;

[0131] 2.5 Lead slurry to seal in the second weakest formation.

[0132] Step 3: Determine whether the annular slurry column structure design is reasonable.

[0133] 3.1 Calculate the equivalent density of friction ρ 摩阻 = 0.11 g / cm 3 ;

[0134] 3.2 Calculate ρ 环空 = 1.40 g / cm 3 ;

[0135] 3.3 Calculate ρ 井底 = ρ 环空 + ρ 摩阻 = 1.40 + 0.11 = 1.51 g / cm 3 ; ρ 井底 is less than the equivalent density of the bottom hole leakage pressure 1.60 g / cm 3 ; the first condition of slurry column structure design is met;

[0136] 3.4 Calculate ρ 摩阻地1 = 0.02 g / cm 3 ; Calculate ρ 摩阻地2 = 0.02 g / cm 3 ;

[0137] 3.5 Calculate ρ 地1承压 = ρ 地1环空 + ρ 摩阻= 1.27 + 0.02 = 1.29 g / cm 3 ; p 地1承压 less than the equivalent density of the lost circulation pressure at the weakest formation 1.32 g / cm 3 ; the second condition for the design of the slurry column structure is met;

[0138] 3.6 Calculate p 地2承压 = p 地2环空 + p 摩阻 = 1.25 + 0.02 = 1.27 g / cm 3 ; p 地2承压 less than the equivalent density of the lost circulation pressure at the second weakest formation 1.35 g / cm 3 ; the third condition for the design of the slurry column structure is met;

[0139] 3.7 Calculate p 终了 = 1.14 g / cm 3 ; p 终了 greater than the equivalent density of the maximum pore pressure of the oil and gas formation 1.07 g / cm 3 ; the fourth condition for the design of the slurry column structure is met.

[0140] Conclusion:

[0141] Based on the above calculations, the slurry column structure design meets the first, second, third, and fourth conditions for reasonable slurry column structure design, and the slurry column structure design is reasonable.

[0142] Example 2

[0143] Well B, vertical well, total drilling depth 2900 m, drilling fluid density before cementing 1.22 g / cm 3 , the development area where the well is located has weak formation pressure capacity and is prone to lost circulation, with the equivalent density of the lost circulation pressure of the weakest formation being 1.42 g / cm 3 , located at a well depth of 2000 m, the equivalent density of the lost circulation pressure of the second weakest formation being 1.46 g / cm 3 , located at a well depth of 2200 m, the equivalent density of the lost circulation pressure of the formation being 1.65 g / cm 3 , the oil and gas formation interval is 2500-2900 m, the equivalent density of the maximum pore pressure of the oil and gas formation is 1.15 g / cm 3 , it is required to cement up to 200 m above the producing formation, and a reasonable cementing annular slurry column structure is designed, with the cement slurry returning to cement up to 1000 m.

[0144] Step 1: Determine the equivalent density of the key points

[0145] 1.1 The equivalent density of the lost circulation pressure of the weakest formation is 1.42 g / cm 3 ; the vertical depth is 2000 m;

[0146] 1.2 The equivalent density of the lost circulation pressure of the second weak formation 1.46 g / cm 3 ; vertical depth 2400 m;

[0147] 1.3 The equivalent density of the maximum pore pressure of the oil and gas formation 1.15 g / cm 3 ;

[0148] 1.4 The equivalent density of the bottom hole lost circulation pressure 1.65 g / cm 3 .

[0149] Step 2: Determine the length of the annular section of each cementing working fluid

[0150] 2.1 Determine the tail slurry to seal 2300-2900 m, section length 600 m, tail slurry density 1.90 g / cm 3 ;

[0151] 2.2 Determine the intermediate slurry to seal 2100-2300 m, section length 200 m, intermediate slurry density 1.75 g / cm 3 ;

[0152] 2.3 Determine the lead slurry to seal 1000-2100 m, section length 1100 m, lead slurry density 1.50 g / cm 3 ;

[0153] 2.4 Lead slurry to seal the thinnest weak formation

[0154] 2.5 Tail slurry to seal the second weak formation

[0155] 2.6 Isolation fluid section length 300 m; density 1.34 g / cm 3 ;

[0156] 2.7 Flushing fluid section length 300 m, density 1.03 g / cm 3 ;

[0157] 2.8 Drilling fluid annular height 400 m, density 1.22 g / cm 3 .

[0158] Step 3: Determine whether the annular slurry column structure design is reasonable

[0159] 3.1 Calculate the equivalent density of friction ρ 摩阻 = 0.11 g / cm 3 ;

[0160] 3.2 Calculate ρ 环空 = 1.49 g / cm 3 ;

[0161] 3.3 Calculate ρ 井底 = ρ 环空 + ρ 摩阻= 1.49 + 0.11 = 1.60 g / cm 3 ; p 井底 < 1.65 g / cm 3 ; the first condition of slurry column structure design is met;

[0162] 3.4 Calculate p 摩阻地1 = 0.03 g / cm 3 ; calculate p 摩阻地2 = 0.03 g / cm 3 ;

[0163] 3.5 Calculate p 地1环空 = 1.35 g / cm 3 ; calculate p 地2环空 = 1.41 g / cm 3 ;

[0164] 3.6 Calculate p 地1承压 = p 地1环空 + p 摩阻 = 1.35 + 0.03 = 1.38 g / cm 3 ; p 地1承压 < 1.42 g / cm 3 ; the second condition of slurry column structure design is met; calculate p 地2承压 = p 地2环空 + p 摩阻 = 1.41 + 0.03 = 1.44 g / cm 3 ; p 地2承压 < 1.46 g / cm 3 ; the third condition of slurry column structure design is met;

[0165] 3.7 Calculate p 终了 = 1.13 g / cm 3 ; p 终了 > 1.12 g / cm 3 ; the fourth condition of slurry column structure design is met.

[0166] Conclusion:

[0167] As can be seen from the above calculation, the slurry column structure design meets the first, second, third and fourth conditions of reasonable slurry column structure design, and the slurry column structure design is reasonable.

Claims

1. A method of designing a cementing annular slurry column, characterized in that, The method comprises the following steps: 1) collecting the leakage parameter of the weakest formation, the leakage parameter of the second weakest formation, the leakage parameter of the bottom hole, and the maximum formation pressure parameter of the formation to be cemented; 2) calculating the maximum pressure bearing parameter of the weakest formation when the cementing operation is bumped, the maximum pressure bearing parameter of the second weakest formation when the cementing operation is bumped, the maximum pressure parameter of the bottom hole when the cementing operation is bumped, and the bottom hole pressure parameter when the tail slurry gels and loses weight during the cementing operation; 3) when the following four conditions are met simultaneously, it is determined that the annular slurry column design is reasonable: the maximum pressure bearing pressure of the weakest formation when the cementing operation is bumped is less than the leakage parameter of the weakest formation; the maximum pressure bearing pressure of the second weakest formation when the cementing operation is bumped is less than the leakage parameter of the second weakest formation; the maximum pressure of the bottom hole when the cementing operation is bumped is less than the leakage parameter of the bottom hole; the bottom hole pressure when the tail slurry gels and loses weight during the cementing operation is greater than the maximum formation pressure parameter.

2. The method of designing a cementing annular slurry column of claim 1, wherein, The leakage parameter of the weakest formation, the leakage parameter of the second weakest formation, the leakage parameter of the bottom hole, the maximum formation pressure parameter, the maximum pressure bearing parameter of the weakest formation when the cementing operation is bumped, the maximum pressure bearing parameter of the second weakest formation when the cementing operation is bumped, the maximum pressure parameter of the bottom hole when the cementing operation is bumped, and the bottom hole pressure parameter when the tail slurry gels and loses weight during the cementing operation are represented by corresponding equivalent densities.

3. The method of designing a cementing annular slurry column of claim 2, wherein, The calculation method of the equivalent density corresponding to the maximum pressure bearing parameter of the weakest formation when the cementing operation is bumped is: p 地1承压 = p 地1环空 + p 摩阻地1 ρ 地1承压 ρ 地1环空 ρ 摩阻地1 ρ 4. The method of designing a cementing annular slurry column of claim 3, wherein, The calculation method of the equivalent density corresponding to the maximum pressure bearing parameter of the second weakest formation when the cementing operation is bumped is: p 地2承压 = p 地2环空 + p 摩阻地2 ρ 地2承压 ρ is the equivalent density corresponding to the maximum pressure parameter of the annulus fluid column at the weak formation during the pressure bumping of the cementing operation, 地2环空 ρ is the equivalent density corresponding to the maximum pressure parameter of the annulus fluid column at the weak formation during the pressure bumping of the cementing operation, 摩阻地2 ρ is the equivalent density corresponding to the friction parameter at the weak formation during the cementing operation.

5. The method of designing a cementing annular slurry column of claim 4, wherein, The calculation method of the equivalent density corresponding to the maximum pressure parameter of the bottom hole when the cementing operation is bumped is: p 井底 = p 环空 + p 摩阻 ρ 井底 ρ 环空 ρ 摩阻 ρ 6. The design method of the cementing annular slurry column according to claim 5, characterized in that The ρ 地1环空 The calculation method is: m is the number of different density fluids above the annulus at the weakest formation, p j is the density of the jth segment of annulus fluid, h j is the vertical height of the jth segment of annulus fluid, h is the vertical depth at the weakest formation, g is the gravitational acceleration constant, j e (1, m); The p 摩阻地1 The calculation method is: m is the number of different density fluids above the annulus at the weakest formation, f is the friction factor, p j is the density of the jth segment of annulus fluid, h j is the vertical height of the jth segment of annulus fluid, V is the return velocity of the annulus fluid, D D is the borehole diameter, D T is the casing outside diameter, h is the depth of the weakest formation, g is the gravitational acceleration constant, j ∈ (1, m); The ρ 地2环空 The calculation method is: m' is the number of different density fluids above the annulus at the second weak formation, p k is the density of the kth segment of annulus fluid, h' k is the vertical height of the kth segment of annulus fluid, h' is the vertical depth at the second weak formation, g is the gravitational acceleration constant, k ∈ (1, m'); The p 摩阻地2 The calculation method is: m' is the number of different density fluids above the annulus at the second weak formation, p k is the density of the kth segment of annulus fluid, h' k is the vertical height of the kth segment of annulus fluid, V is the return velocity of the annulus fluid, D D is the borehole diameter, D T is the casing outside diameter, h' is the vertical depth of the second weak formation, g is the gravitational acceleration constant, k ∈ (1, m'); The p 环空 The calculation method is: n is the number of different density fluids in the annulus, p i is the density of the i-th segment of fluid in the annulus, L i is the vertical height of the i-th segment of fluid in the annulus, L is the vertical depth of the well being constructed, g is the acceleration due to gravity, and i ∈ (1, n). The p 摩阻 The calculation method is: n is the number of different density fluids in the annulus, f is the friction factor, p i is the density of the i-th segment of fluid in the annulus, L i is the length of the i-th segment of fluid in the annulus, V is the return velocity of the fluid in the annulus, D D is the borehole diameter, D T is the casing outside diameter, L is the vertical depth of the well being constructed, g is the gravitational acceleration constant, i ∈ (1, n).

7. The method of designing a well cementing annular slurry column of claim 6, wherein, The calculation method of the equivalent density corresponding to the bottom hole pressure parameter when the tail slurry gels and loses weight during the cementing operation is: ρ 终了 ρ is the equivalent density corresponding to the bottom hole pressure when the tail slurry loses weight during cementing operations, P 环空 is the annular fluid column pressure parameter during cementing operations, and ΔP is the pressure loss value due to the tail slurry losing weight.

8. The method of designing a well cementing annular slurry column of claim 7, wherein, The calculation method of ΔP is: ΔP = max(ΔP1, ΔP2) P SGS is the static gel strength of the cement slurry; L C is the vertical length of the tail slurry section; D D is the hole diameter; D T is the casing outside diameter; ΔP2= pgL C p is the density of fresh water, 1.0 g / cm 3 ; g is the acceleration due to gravity constant; L C is the length of the tailings section.

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