Formation collapse pressure prediction method for salt-containing stratum
By combining density data, lithology data and stratigraphic temperature, specific calculation methods are used to calculate the stratigraphic collapse pressure of different types of rock layers separately, and merge them, the problem of inaccurate prediction of the collapse pressure of salt-containing formations in the existing technology is solved, achieving higher prediction accuracy and better engineering guidance.
Patent Information
- Application Number
- CN202410291944.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-14
- Publication Date
- 2025-03-04
AI Technical Summary
The prior art is difficult to accurately predict the formation collapse pressure of salt-containing formations, which may lead to drilling safety hazards.
By collecting the density data, lithology data, formation pressure prediction results and formation temperature of drilled wells, the formation collapse pressure of clastic rocks, dirty salt and pure salt rocks were calculated respectively by using the Coulun-moor strength criterion and Norton analytical method, and combined to obtain the formation collapse pressure of the salt-containing formation.
Accurate prediction of the formation collapse pressure of the salt-containing formation is achieved, the prediction accuracy is improved, the drilling safety hazards are reduced, and the engineering drilling mud design is better guided.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of formation collapse pressure prediction in oil and natural gas exploration, and in particular to a formation collapse pressure prediction method for a salt-containing formation. Background Art
[0002] Formation collapse pressure refers to the fluid pressure in the well at which the wellbore collapses when the pressure generated by the drilling fluid column in the well at the observation point is lower than a certain value. The study of formation collapse pressure is crucial to ensure the wellbore stability of drilling operations. It guides the design of drilling fluid to ensure that the wellbore wall does not collapse due to improper pressure. In addition, it helps to optimize drilling plans, reduce operational risks, and ensure the safety and economic benefits of the operation process. The method for predicting formation collapse pressure in saline formations is different from the conventional method for predicting collapse pressure in clastic rock formations. If the conventional method for predicting collapse pressure in clastic rock formations is used to predict the formation collapse pressure in saline formations, it will cause a large error and may cause drilling safety hazards.
[0003] Therefore, a method for predicting formation collapse pressure in saline formations is urgently needed. Summary of the invention
[0004] The present invention provides a method for predicting the formation collapse pressure of a saline formation, which realizes the accurate prediction of the formation collapse pressure of the saline formation.
[0005] The present invention provides a method for predicting formation collapse pressure of a saline formation, comprising the following steps:
[0006] Collect the density data, lithology data, formation pressure prediction results and formation temperature of the drilled wells;
[0007] The overburden pressure P is calculated using the density data of the drilled well. o ;
[0008] Using lithology data, the drilled formations are divided into pure salt formations, dirty salt formations and clastic rock formations;
[0009] For the clastic rock formation and the dirty salt formation, the formation collapse pressure P of the clastic rock formation is calculated by using the Coulomb-Moore strength criterion method. c碎屑岩 and the formation collapse pressure P of the dirty salt formation c脏盐 ;
[0010] For the pure salt rock formation, the formation collapse pressure P of the pure salt rock formation is calculated using the Norton analytical method. c纯盐岩 ;
[0011] The formation collapse pressure P of the clastic rock formation c碎屑岩 , the formation collapse pressure P of pure salt rock formation c纯盐岩and the formation collapse pressure P of dirty salt formation c脏盐 Combine and add to get the formation collapse pressure P of the salt-bearing formation c含盐地层 .
[0012] The method for predicting the formation collapse pressure of a salt-containing formation preferably calculates the overburden formation pressure P o The expression is:
[0013]
[0014] in,
[0015] H is the depth of the overlying rock layer;
[0016] g is the acceleration due to gravity;
[0017] dH is the differential element of depth H;
[0018] ρ(H) is the density of the overburden at depth H.
[0019] The formation collapse pressure prediction method of the salt-containing formation preferably calculates the formation collapse pressure P of the clastic rock formation. c碎屑岩 , the formation collapse pressure P of the salt formation c脏盐 The expression of the method based on the Coulomb-Moore intensity criterion is:
[0020] P c =(η(3σ h1 -σ h2 )-2CK+αP p (K 2 -1)) / (K 2 +η) (2)
[0021] K=cot(π / 4-θ / 2) (3)
[0022] In the formula,
[0023] P c is the formation collapse pressure P of the clastic rock formation c碎屑岩 Or the formation collapse pressure P of the salt formation c脏盐 ;
[0024] C is cohesion;
[0025] P p The formation pressure prediction result for saline formations;
[0026] σ h1 , σ h2 are the maximum and minimum horizontal principal stresses respectively;
[0027] η is the stress nonlinear correction coefficient;
[0028] α is the effective stress coefficient;
[0029] θ is the angle between the radius vector of a point on the wellbore wall and the direction of the maximum horizontal ground stress.
[0030] The method for predicting the formation collapse pressure of a salt-containing formation preferably calculates the formation collapse pressure P of a pure salt rock formation. c纯盐岩 The Norton analytical expression is:
[0031]
[0032] Where:
[0033] P c纯盐岩 is the formation collapse pressure of pure salt rock formation;
[0034] H is the depth;
[0035] m is the wellbore shrinkage rate per unit hour;
[0036] P o is the overburden pressure;
[0037] n is the stress index;
[0038] A is the creep coefficient;
[0039] B is the creep constant of salt rock;
[0040] T is the absolute formation temperature.
[0041] The formation collapse pressure prediction method of the saline formation, preferably, the formation collapse pressure P of the saline formation c含盐地层 The expression is:
[0042] P c含盐地层 =P c碎屑岩 +P c纯盐岩 +P c脏盐 (5).
[0043] The method for predicting formation collapse pressure of a saline formation, preferably, the method for predicting formation pressure prediction results of a saline formation comprises the following steps:
[0044] Collect P-wave time difference data of the drilled wells;
[0045] Converting the longitudinal wave time difference data into longitudinal wave velocity data;
[0046] Using lithology data, the drilled formations are divided into pure salt formations, dirty salt formations and clastic rock formations;
[0047] For the clastic rock formation and the dirty salt formation, the formation pressure P of the clastic rock formation is calculated by using the P-wave velocity data and the Eaton method.碎屑岩 and the formation pressure P of the dirty salt formation 脏盐 ;
[0048] For the pure salt rock formation, the formation pressure P of the pure salt rock formation is 纯盐岩 Set as hydrostatic pressure P 静水 , calculate the hydrostatic pressure P 静水 ;
[0049] The formation pressure P of the clastic rock formation 碎屑岩 , the formation pressure P of pure salt rock formation 纯盐岩 and the formation pressure P of dirty salt formation 脏盐 Combine and add the calculations to obtain the formation pressure P of the salt-bearing formation. 含盐地层 .
[0050] In the method for predicting formation collapse pressure of saline formations, preferably, the expression for converting the P-wave time difference data into P-wave velocity data is:
[0051] Velocity=1 / DT (6)
[0052] in,
[0053] Velocity is the longitudinal wave velocity;
[0054] DT is the longitudinal wave time difference.
[0055] The method for predicting formation collapse pressure of a salt-containing formation, preferably, the hydrostatic pressure P 静水 The expression is:
[0056]
[0057] in,
[0058] ρ 水 (H) is the formation water density at depth H.
[0059] The method for predicting the formation collapse pressure of a salt-containing formation preferably calculates the formation pressure P of the clastic rock formation. 碎屑岩 and the formation pressure P of the dirty salt formation 脏盐 The Eaton law expression is:
[0060]
[0061] in,
[0062] P is the formation pressure of clastic rock formation 碎屑岩 Or the formation pressure P of dirty salt formation 脏盐 ;
[0063] trend is the normal compaction trend line;
[0064] n 指 is the Eaton index.
[0065] The method for predicting the formation collapse pressure of a saline formation preferably calculates the formation pressure P of the saline formation. p The expression is:
[0066] P p =P 碎屑岩 +P 纯盐岩 +P 脏盐 (9).
[0067] The beneficial effects are:
[0068] The invention discloses a method for predicting the formation collapse pressure of a saline formation. Compared with conventional methods, this method can more accurately predict the formation collapse pressure of the saline formation.
[0069] The invention discloses a method for predicting formation collapse pressure of a salt-containing formation, which can improve the prediction accuracy of formation collapse pressure and better guide the design of engineering drilling mud. DETAILED DESCRIPTION
[0070] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0071] The present invention provides a method for predicting formation collapse pressure of a saline formation, comprising the following steps: collecting density data, lithology data, formation pressure prediction results and formation temperature of a well that has been drilled; calculating the overburden formation pressure P using the density data of the well that has been drilled o ; Using lithology data, the drilled formations are divided into pure salt formations, dirty salt formations and clastic formations; for the clastic formations and the dirty salt formations, the formation collapse pressure P of the clastic formations is calculated using the Coulomb-Moore strength criterion method c碎屑岩 and the formation collapse pressure P of the dirty salt formation c脏盐 For the pure salt rock formation, the formation collapse pressure P of the pure salt rock formation is calculated using the Norton analytical method. c纯盐岩 ; The formation collapse pressure P of the clastic rock formation c碎屑岩 , the formation collapse pressure P of pure salt rock formation c纯盐岩 and the formation collapse pressure P of dirty salt formation c脏盐 Combine and add to get the formation collapse pressure P of the salt-bearing formationc含盐地层 The present invention discloses a method for predicting formation collapse pressure of a salt-containing formation, which can improve the prediction accuracy of formation collapse pressure and better guide the design of engineering drilling mud.
[0072] The entire technical process is described in detail below using a method for predicting formation collapse pressure in saline formations as an example.
[0073] A method for predicting formation collapse pressure of a saline formation comprises the following steps:
[0074] Step S1: Collecting density data, lithology data, formation pressure prediction results of saline formations and formation temperature of the drilled wells.
[0075] Step S2: Calculate the overburden pressure P using the density data of the drilled well o .
[0076] Calculate the overburden pressure P o The expression is:
[0077]
[0078] in,
[0079] H is the depth of the overlying rock layer;
[0080] g is the acceleration due to gravity;
[0081] dH is the differential element of depth H;
[0082] ρ(H) is the density of the overburden at depth H.
[0083] Step S3: using the lithology data, the drilled strata are divided into pure salt rock strata, dirty salt strata and clastic rock strata.
[0084] Among them, pure salt rock formations and dirty salt formations constitute salt rock formations, and dirty salt formations are mixed lithologies of pure salt rock and clastic rock.
[0085] Step S4: For the clastic rock formation and the dirty salt formation, the formation collapse pressure P of the clastic rock formation is calculated respectively by using the Coulomb-Moore strength criterion method. c碎屑岩 and the formation collapse pressure P of the dirty salt formation c脏盐 .
[0086] Among them, the formation collapse pressure P of the clastic rock formation is calculated c碎屑岩 , the formation collapse pressure P of the salt formation c脏盐 The expression of the method based on the Coulomb-Moore intensity criterion is:
[0087] P c =(η(3σ h1 -σh2 )-2CK+αP p (K 2 -1)) / (K 2 +η) (2)
[0088] K=cot(π / 4-θ / 2) (3)
[0089] In the formula,
[0090] P c is the formation collapse pressure P of the clastic rock formation c碎屑岩 Or the formation collapse pressure P of dirty salt formation c脏盐 ;
[0091] C is cohesion;
[0092] P p The formation pressure prediction result for saline formations;
[0093] σ h1 , σ h2 are the maximum and minimum horizontal principal stresses respectively;
[0094] η is the stress nonlinear correction coefficient;
[0095] α is the effective stress coefficient;
[0096] θ is the angle between the radius vector of a point on the wellbore wall and the direction of the maximum horizontal ground stress.
[0097] Step S5: For the pure salt rock formation, the formation collapse pressure P of the pure salt rock formation is calculated using the Norton analytical method. c纯盐岩 .
[0098] Among them, the formation collapse pressure P of pure salt rock formation is calculated c纯盐岩 The Norton analytical expression is:
[0099]
[0100] Where:
[0101] P c纯盐岩 is the formation collapse pressure of pure salt rock formation;
[0102] H is the depth;
[0103] m is the wellbore shrinkage rate per unit hour;
[0104] P o is the overburden pressure;
[0105] n is the stress index;
[0106] A is the creep coefficient;
[0107] B is the creep constant of salt rock;
[0108] T is the absolute formation temperature.
[0109] Step S6: The formation collapse pressure P of the clastic rock formation c碎屑岩 , the formation collapse pressure P of pure salt rock formation c纯盐岩 and the formation collapse pressure P of dirty salt formation c脏盐 Combine and add to get the formation collapse pressure P of the salt-bearing formation c含盐地层 .
[0110] The formation collapse pressure result P of saline formation c含盐地层 The expression is:
[0111] P c含盐地层 =P c碎屑岩 +P c纯盐岩 +P c脏盐 (5).
[0112] The method for predicting the formation pressure prediction result of the salt-containing formation in steps S1 to S6 comprises the following steps:
[0113] S11: Collect the P-wave time difference data of the drilled well.
[0114] Step S11 also includes step S111, and step S111 specifically includes: checking the quality of the density data and acoustic time difference data collected in the well, and if problems are found, performing logging curve editing and correction work such as depth correction, splicing, consistency processing, singular value correction, etc.
[0115] S12: Convert the longitudinal wave time difference data into longitudinal wave velocity data.
[0116] The formula for converting the longitudinal wave time difference data into longitudinal wave velocity data is:
[0117] Velocity=1 / DT (6)
[0118] in,
[0119] Velocity is the longitudinal wave velocity;
[0120] DT is the longitudinal wave time difference.
[0121] S13: Using lithology data, the drilled formations are divided into pure salt formations, dirty salt formations and clastic rock formations.
[0122] Among them, pure salt rock formations and dirty salt formations constitute salt rock formations, and dirty salt formations are mixed lithologies of pure salt rock and clastic rock.
[0123] S14: For the clastic rock formation and the dirty salt formation, using the P-wave velocity data, the Eaton method is used to calculate the formation pressure P of the clastic rock formation respectively. 碎屑岩 and the formation pressure P of the dirty salt formation 脏盐 .
[0124] S15: For the pure salt rock formation, the formation pressure P of the pure salt rock formation is 纯盐岩 Set as hydrostatic pressure P 静水 , calculate the hydrostatic pressure P 静水 .
[0125] Calculate the hydrostatic pressure P 静水 The expression is:
[0126]
[0127] in,
[0128] H is the depth;
[0129] g is the acceleration due to gravity;
[0130] dH is the differential element of depth H;
[0131] ρ 水 (H) is the formation water density at depth H.
[0132] Wherein, the formation pressure P of the clastic rock formation is calculated in step S14. 碎屑岩 and the formation pressure P of the dirty salt formation 脏盐 The expression of is formula (8):
[0133]
[0134] in,
[0135] P for P 碎屑岩 or P 脏盐 ;
[0136] Velocity is the longitudinal wave velocity;
[0137] trend is the normal compaction trend line;
[0138] n 指 is the Eaton index.
[0139] S17: The formation pressure P of the clastic rock formation 碎屑岩 , the formation pressure P of pure salt rock formation 纯盐岩 and the formation pressure P of dirty salt formation 脏盐 Combine and add the calculations to obtain the formation pressure P of the salt-bearing formation. p .
[0140] The formation pressure P of the clastic rock formation 碎屑岩 , the formation pressure P of pure salt rock formation 纯盐岩 and the formation pressure P of dirty salt formation 脏盐 Combine and add to get the formation pressure P of the salt-bearing formation p .
[0141] Calculate the formation pressure P of the salt-bearing formation p The expression is:
[0142] P p =P 碎屑岩 +P 纯盐岩 +P 脏盐 (9).
[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for predicting formation collapse pressure of a saline formation, characterized in that: The following steps are involved: Collect the density data, lithology data, formation pressure prediction results and formation temperature of the drilled wells; The overburden pressure P is calculated using the density data of the drilled well. o ; Using lithology data, the drilled formations are divided into pure salt formations, dirty salt formations and clastic rock formations; For the clastic rock formation and the dirty salt formation, the formation collapse pressure P of the clastic rock formation is calculated by using the Coulomb-Moore strength criterion method. c碎屑岩 and the formation collapse pressure P of the dirty salt formation c脏盐 ; For the pure salt rock formation, the formation collapse pressure P of the pure salt rock formation is calculated using the Norton analytical method. c纯盐岩 ; The formation collapse pressure P of the clastic rock formation c碎屑岩 , the formation collapse pressure P of pure salt rock formation c纯盐岩 and the formation collapse pressure P of dirty salt formation c脏盐 Combine and add to get the formation collapse pressure P of the salt-bearing formation c含盐地层 .
2. The method for predicting formation collapse pressure of a saline formation according to claim 1, characterized in that: Calculate the overburden pressure P o The expression is: in, H is the depth of the overlying rock layer; g is the acceleration due to gravity; dH is the differential element of depth H; ρ(H) is the density of the overburden at depth H.
3. The method for predicting formation collapse pressure of a saline formation according to claim 2, characterized in that: Calculation of formation collapse pressure P of clastic rock formation c碎屑岩 , the formation collapse pressure P of the salt formation c脏盐 The expression of the method based on the Coulomb-Moore intensity criterion is: P c =(η(3σ h1 -s h2 )-2CK+αP p (K 2 -1)) / (K 2 +h) (2) K=cot(π / 4-θ / 2) (3) In the formula, P c is the formation collapse pressure P of the clastic rock formation c碎屑岩 Or the formation collapse pressure P of the salt formation c脏盐 ; C is cohesion; P p The formation pressure prediction result for saline formations; σ h1 , σ h2 are the maximum and minimum horizontal principal stresses respectively; η is the stress nonlinear correction coefficient; α is the effective stress coefficient; θ is the angle between the radius vector of a point on the wellbore wall and the direction of the maximum horizontal ground stress.
4. The method for predicting formation collapse pressure of a saline formation according to claim 3, characterized in that: Calculation of the formation collapse pressure P of pure salt rock formation c纯盐岩 The Norton analytical expression is: Where: P c纯盐岩 is the formation collapse pressure of pure salt rock formation; H is the depth; m is the wellbore shrinkage rate per unit hour; P o is the overburden pressure; n is the stress index; A is the creep coefficient; B is the creep constant of salt rock; T is the absolute formation temperature.
5. The method for predicting formation collapse pressure of a saline formation according to claim 4, characterized in that: The formation collapse pressure P of saline formation c含盐地层 The expression is: P c含盐地层 =P c碎屑岩 +P c纯盐岩 +P c脏盐 (5)。 6. The method for predicting formation collapse pressure of a saline formation according to any one of claims 1 to 5, characterized in that: The method for predicting the formation pressure prediction result of the saline formation comprises the following steps: Collect P-wave time difference data of the drilled wells; Converting the longitudinal wave time difference data into longitudinal wave velocity data; Using lithology data, the drilled formations are divided into pure salt formations, dirty salt formations and clastic rock formations; For the clastic rock formation and the dirty salt formation, the formation pressure P of the clastic rock formation is calculated by using the P-wave velocity data and the Eaton method. 碎屑岩 and the formation pressure P of the dirty salt formation 脏盐 ; For the pure salt rock formation, the formation pressure P of the pure salt rock formation is 纯盐岩 Set as hydrostatic pressure P 静水 , calculate the hydrostatic pressure P 静水 ; The formation pressure P of the clastic rock formation 碎屑岩 , the formation pressure P of pure salt rock formation 纯盐岩 and the formation pressure P of dirty salt formation 脏盐 Combine and add the calculations to obtain the formation pressure P of the salt-bearing formation. 含盐地层 .
7. The method for predicting formation collapse pressure of a saline formation according to claim 6, characterized in that: The expression for converting the longitudinal wave time difference data into longitudinal wave velocity data is: Velocity=1 / DT (6) in, Velocity is the longitudinal wave velocity; DT is the longitudinal wave time difference.
8. The method for predicting formation collapse pressure of a saline formation according to claim 7, characterized in that: The hydrostatic pressure P 静水 The expression is: in, ρ 水 (H) is the formation water density at depth H.
9. The method for predicting formation collapse pressure of a saline formation according to claim 8, characterized in that: Calculate the formation pressure P of the clastic rock formation 碎屑岩 and the formation pressure P of the dirty salt formation 脏盐 The Eaton law expression is: in, P is the formation pressure of clastic rock formation 碎屑岩 Or the formation pressure P of dirty salt formation 脏盐 ; trend is the normal compaction trend line; n 指 is the Eaton index.
10. The method for predicting formation collapse pressure of a saline formation according to claim 9, characterized in that: Calculate the formation pressure P of the salt-bearing formation p The expression is: P p =P 碎屑岩 +P 纯盐岩 +P 脏盐 (9)。