A formation pressure monitoring method based on the effective stress method

Abstract

The present invention discloses a formation pressure monitoring method based on the effective stress method, comprising: Step 1, collecting various drilling engineering parameters and formation pressure data of adjacent wells; Step 2, calculating the corrected modified bit weight index of the adjacent wells and the vertical effective stress of the effective pressure measurement points; Step 3, substituting the corrected modified bit weight index and the vertical effective stress into the effective stress model to obtain a correction formula; Step 4, obtaining the formation pressure of the well being drilled according to the correction formula. The present invention uses the engineering parameters collected in real time during the drilling process, can calculate the formation pressure in real time, and the effective stress method is applicable to the calculation of abnormal formation pressure caused by reasons other than undercompaction, and can improve the monitoring accuracy of abnormal formation pressure caused by non-undercompaction reasons.

Description

Technical Field

[0001] The present invention relates to the technical field of formation pressure monitoring. More specifically, the present invention relates to a formation pressure monitoring method based on the effective stress method. Background Art

[0002] Formation pressure is one of the hot issues in the petroleum industry. Accurately calculating formation pressure is an important prerequisite for ensuring drilling safety. Since there is usually no acoustic data during the drilling process, the main means of current formation pressure monitoring is: by means of correcting the drilling pressure index, establishing a trend line in the normally compacted section, and calculating the formation pressure coefficient through the Eaton method. In the current application of formation pressure monitoring, this technical means mainly has the following problems:

[0003] 1. Using the Eaton method to calculate formation pressure requires first establishing a trend line in the normally compacted section. In actual application, the trend line often needs to be adjusted with the change of the drill string assembly. This frequent adjustment process seriously reduces the accuracy of the Eaton method calculation and is also complex in operation.

[0004] 2. The aforementioned monitoring means is only applicable to the monitoring of abnormal formation pressure caused by undercompaction, and its application effect is not good in the monitoring of abnormal formation pressure caused by other reasons. Summary of the Invention

[0005] The object of the present invention is to design and develop a formation pressure monitoring method based on the effective stress method, which calculates the formation pressure through the effective stress method using drilling engineering parameters. The engineering parameters collected in real time during the drilling process are used, and the formation pressure can be calculated in real time. The effective stress method is applicable to the calculation of abnormal formation pressure caused by reasons other than undercompaction.

[0006] The technical solution provided by the present invention is as follows:

[0007] A formation pressure monitoring method based on the effective stress method, comprising the following steps:

[0008] Step 1: Collect various drilling engineering parameters and formation pressure data of adjacent wells;

[0009] Step 2: Calculate the corrected drilling pressure index and vertical effective stress of the adjacent well:

[0010]

[0011] σ = P0 - P p ;

[0012] In the formula, d cc is the corrected drilling pressure index, R is the drilling speed, N is the rotational speed, F is the mechanical efficiency, W is the drilling pressure, D b is the bit diameter, ρ nis the formation water density, ρ m is the mud density, σ is the vertical effective stress, P0 is the overburden pressure coefficient, P p is the formation pressure coefficient;

[0013] Step 3: Obtain a correction formula based on the corrected modified weight-on-bit index and the vertical effective stress:

[0014]

[0015] In the formula, a is the first constant and b is the second constant;

[0016] Step 4: Obtain the formation pressure of the well being drilled based on the correction formula.

[0017] Preferably, the multiple drilling engineering parameters include the weight on bit, the penetration rate, the mud density, the bit diameter, the rotary speed, and the torque of the bit.

[0018] Preferably, the formation pressure data includes the wireline formation testing data and the overburden pressure.

[0019] Preferably, Step 3 specifically includes the following steps:

[0020] Step 1: Substitute the corrected modified weight-on-bit index and the vertical effective stress into the effective stress model to obtain the first constant and the second constant;

[0021] Among them, the effective stress model is:

[0022]

[0023] Step 2: Establish a correction formula based on the effective stress model.

[0024] Preferably, the mechanical efficiency satisfies:

[0025] F = MSE / CCS;

[0026] In the formula, MSE is the mechanical specific energy and CCS is the baseline value of the rock compressive strength.

[0027] Preferably, the mechanical specific energy satisfies:

[0028]

[0029] In the formula, T is the torque of the bit.

[0030] Preferably, the establishment of the baseline value of the rock compressive strength specifically includes the following steps:

[0031] Step a: Calculate the mechanical specific energy of the drilled section and obtain the mechanical specific energy curve of the normal pressure section;

[0032] Step b: Establish a semi-logarithmic coordinate system with well depth and mechanical specific energy as the horizontal and vertical coordinates;

[0033] Step c: Select two normal pressure points on the mechanical specific energy curve. Taking the projection points of the two normal pressure points on the semi-logarithmic coordinate system as control points, establish a trend line passing through the control points as the rock compressive strength baseline.

[0034] Preferably, the selection of the two normal pressure points satisfies:

[0035] The distance between the two normal pressure points is greater than 300 m, the fluctuations of the drilling time values and mechanical specific energy values within 5 m before and after the two normal pressure points do not exceed 10%, and both of the two normal pressure points are in the middle-upper formation or normal pressure section.

[0036] The beneficial effects of the present invention are as follows:

[0037] (1) A formation pressure monitoring method based on the effective stress method designed and developed by the present invention does not rely on a trend line in the calculation process and does not require adjustment of calculation parameters with the change of drilling conditions.

[0038] (2) The formation pressure monitoring method based on the effective stress method designed and developed by the present invention is not only applicable to the monitoring of abnormal formation pressure caused by undercompaction in sandstone-shale formations, but also applicable to the monitoring of abnormal formation pressure in non-sandstone-shale formations or other causes. Description of the Drawings

[0039] Figure 1 It is a schematic flow chart of the formation pressure monitoring method based on the effective stress method of the present invention.

[0040] Figure 2 It is an effect diagram of formula regression according to the engineering parameters of Well A and the cable pressure measurement data of the present invention.

[0041] Figure 3 It is a comparison diagram of the monitoring results while drilling using the formula of adjacent wells and the cable pressure measurement data of Well B of the present invention. Detailed Embodiments

[0042] The following further detailed description of the present invention is made to enable those skilled in the art to implement it with reference to the text of the specification.

[0043] As Figure 1 shown, a formation pressure monitoring method based on the effective stress method provided by the present invention specifically includes the following steps:

[0044] Step 1: Collect various drilling engineering parameters of adjacent wells and formation pressure-related data of adjacent wells;

[0045] Among them, the multiple drilling engineering parameters include drilling time, drilling pressure, rotational speed, mud density, bit diameter, and torque;

[0046] The formation pressure-related data includes pressure measurement data (unit: g / cm 3 ) and overburden pressure calculation data;

[0047] The pressure measurement data is obtained by a modular dynamic formation tester;

[0048] Under common conditions, the overburden pressure calculation data (overburden pressure coefficient) is the same as the equivalent density of the overburden pressure, and the equivalent density of the overburden pressure satisfies:

[0049]

[0050]

[0051] In the formula, ρ0 is the equivalent density of the overburden pressure, unit: g / cm 3 ; ρ b is the density of the rock mass, unit: g / cm 3 ; ρ f is the fluid density, unit: g / cm 3 ; is the porosity, unit: %; is the porosity value at the mud line, unit: %; pde is the porosity decay index, a constant; depth is the well depth, unit: m.

[0052] Step 2: Calculate the corrected modified drilling pressure index of the adjacent well and the vertical effective stress of the effective pressure measurement point of the adjacent well;

[0053] Among them, calculating the corrected modified drilling pressure index of the adjacent well specifically includes the following steps:

[0054] a) Calculate the mechanical specific energy of the drilled section and obtain the mechanical specific energy curve of the normal pressure section;

[0055] Among them, the mechanical specific energy satisfies:

[0056]

[0057] In the formula, MSE is the mechanical specific energy, unit: MPa; T is the torque of the bit, unit: kN / m;

[0058] b) Establish a semi-logarithmic coordinate system with well depth and mechanical specific energy as the horizontal and vertical coordinates;

[0059] c), Select two normal pressure points on the mechanical specific energy curve, use the projection points of the two normal pressure points on the semi-logarithmic coordinate system as control points, and establish a trend line passing through the control points as the rock compressive strength baseline;

[0060] Among them, the selection of the two normal pressure points satisfies:

[0061] The distance between the two normal pressure points is greater than 300m, the fluctuations of the drilling time values and mechanical specific energy values within 5m before and after the two normal pressure points do not exceed 10%, and both of the two normal pressure points are in the middle-upper formation or normal pressure section.

[0062] d), Obtain the mechanical efficiency based on the mechanical specific energy and the rock compressive strength baseline, and obtain the corrected modified bit weight index:

[0063]

[0064] In the formula, d cc is the corrected modified bit weight index, dimensionless; R is the drilling rate, unit: m / h; N is the rotary table speed, unit: r / min; F is the mechanical efficiency, dimensionless; W is the bit weight, unit: kN; D b is the bit diameter, unit: mm, ρ n is the formation water density, unit: g / cm 3 ; ρ m is the drilling fluid density, unit: g / cm 3 ;

[0065] Among them, the mechanical efficiency satisfies:

[0066] F = MSE / CCS;

[0067] In the formula, the CCS is the rock compressive strength baseline value, unit: MPa;

[0068] The vertical effective stress satisfies:

[0069] σ = P0 - P p ;

[0070] In the formula, σ is the vertical effective stress, dimensionless, P0 is the overburden pressure coefficient, dimensionless, P p is the formation pressure coefficient, dimensionless.

[0071] Step three, Substitute the corrected modified bit weight index and vertical effective stress of the adjacent well into the effective stress model to obtain the first constant and the second constant;

[0072] Among them, the effective stress model is:

[0073]

[0074] A correction formula is established according to the effective stress model:

[0075]

[0076] In the formula, a is the first constant and b is the second constant;

[0077] Step 4: Collect the drilling engineering parameters of the well being drilled, including drilling time, weight on bit, rotary speed, mud density, bit diameter, and torque;

[0078] Step 5: Calculate the corrected modified weight-on-bit index of the well being drilled;

[0079] Step 6: Calculate the formation pressure of the well being drilled according to the correction formula.

[0080] Example 1

[0081] The present invention is applied to the monitoring of formation pressure while drilling in the Pearl River Mouth Basin. Under the condition of lacking logging-while-drilling acoustic logging data, the drilling engineering parameters of adjacent wells are collected, and the relevant correction method of the modified weight-on-bit index is used to correct the modified weight-on-bit index; the wireline pressure measurement data of adjacent wells are collected to calculate the vertical effective stress; the corrected modified weight-on-bit index and the vertical effective stress are combined, and the relevant constants of the calculation model of the effective stress method are obtained by regression; according to the calculation model of the effective stress method, the drilling engineering parameters of the well being drilled are used to calculate the formation pressure while drilling, and the monitoring accuracy reaches 95%. Compared with the commonly used Eaton method in the current formation pressure monitoring work, it is not necessary to establish a normal compaction trend line and the accuracy is relatively high.

[0082] Example 2

[0083] Taking Well A as an example, during the drilling of Well A, abnormal high pressures were encountered in the Zhujiang Formation, Zhuhai Formation and Enping Formation respectively. The d cc index of the whole well was calculated with the engineering parameters of Well A, and at the same time the vertical effective stress of the pressure measurement points was calculated with the wireline pressure measurement data. The two sets of parameters were substituted into the effective stress model for regression. As Figure 2 shown, the calculation formula of the vertical effective stress of different formations in this area was obtained; during the drilling of Well B, the actual drilling engineering parameters were extracted and the d cc index was calculated, and the effective stress was calculated by substituting it into the aforementioned formula. The formation pressure was calculated by using the correction formula; as Figure 3 shown, after the well was completed, the pressure measurement data was compared with the pressure monitoring data while drilling, and the matching degree between the two was good.

[0084] A formation pressure monitoring method based on the effective stress method designed and developed by the present invention uses the model of calculating formation pressure by the effective stress method and the related models for correcting the drilling pressure index to obtain a formation pressure calculation model with the corrected drilling pressure index as a variable. After substituting the data of adjacent wells, a calculation formula is obtained. According to the calculation formula and combined with the engineering parameters collected in real time during the drilling of the well being drilled, the real-time formation pressure is calculated, which can improve the monitoring accuracy of abnormal formation pressure caused by non-undercompaction. The calculation process of the present invention does not depend on the trend line and does not require adjusting the calculation parameters with the change of drilling conditions. It is applicable not only to the monitoring of abnormal formation pressure caused by undercompaction in sandstone and mudstone formations, but also to the monitoring of abnormal formation pressure in non-sandstone and mudstone formations or other causes.

[0085] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the embodiments shown and described here.

Claims

1. A formation pressure monitoring method based on the effective stress method, characterized in that, It includes the following steps: Step 1: Collect various drilling engineering parameters and formation pressure data of adjacent wells; Step 2: Calculate the corrected modified bit weight index and vertical effective stress of adjacent wells; σ = P0 - P p ; where d cc is the corrected modified weight-on-bit index, R is the penetration rate, N is the rotary speed, F is the mechanical efficiency, W is the weight on bit, D b is the bit diameter, ρ n is the density of formation water, ρ m is the mud density, σ is the vertical effective stress, P0 is the overburden pressure coefficient, P p is the formation pressure coefficient; Step 3: Substitute the corrected modified bit weight index and vertical effective stress of adjacent wells into the effective stress model to obtain the first constant and the second constant; Among them, the effective stress model is: Establish a correction formula according to the effective stress model: In the formula, a is the first constant and b is the second constant; Step 4: Collect the drilling engineering parameters of the well being drilled, including drilling time, bit weight, rotary speed, mud density, bit diameter, torque; Step 5: Calculate the corrected modified bit weight index of the well being drilled; Step 6: Calculate the formation pressure of the well being drilled according to the correction formula.

2. The formation pressure monitoring method based on the effective stress method according to claim 1, characterized in that The various drilling engineering parameters include bit weight, drilling time, mud density, bit diameter, rotary speed and torque of the bit.

3. The formation pressure monitoring method based on the effective stress method according to claim 2, characterized in that The formation pressure data includes wireline pressure measurement data and overburden pressure.

4. The formation pressure monitoring method based on the effective stress method according to claim 3, characterized in that The mechanical efficiency satisfies: F = MSE / CCS; In the formula, MSE is the mechanical specific energy and CCS is the baseline value of rock compressive strength.

5. The formation pressure monitoring method based on the effective stress method according to claim 4, characterized in that The mechanical specific energy satisfies: In the formula, T is the torque of the bit.

6. The formation pressure monitoring method based on the effective stress method according to claim 5, characterized in that, The establishment of the baseline of rock compressive strength specifically includes the following steps: Step a: Calculate the mechanical specific energy of the drilled section and obtain the mechanical specific energy curve of the normal pressure section; Step b: Establish a semi-logarithmic coordinate system with well depth and mechanical specific energy as the horizontal and vertical coordinates; Step c: Select two normal pressure points on the mechanical specific energy curve, take the projections of the two normal pressure points on the semi-logarithmic coordinate system as control points, and establish a trend line passing through the control points as the baseline of rock compressive strength.

7. The formation pressure monitoring method based on the effective stress method according to claim 6, wherein, The selection of the two normal pressure points satisfies: The distance between the two normal pressure points is greater than 300m, the fluctuations of the drilling time values and mechanical specific energy values within 5m before and after the two normal pressure points do not exceed 10%, and both of the two normal pressure points are in the middle-upper formation or normal pressure section.

Images