Method for acquiring formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics

Abstract

The invention relates to the technical field of methods for obtaining formation pressure through oil drilling, in particular to a method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics, which comprises the following steps of: collecting and arranging logging data, logging gas logging total hydrocarbon data, drilling fluid density data and the like after three or more drilled reference wells in the same block are drilled; calculating the stratum pressure equivalent density of a reference well and the well bottom pressure difference equivalent density of mudstone sections with different burial depths according to the data, drawing a well bottom pressure difference-logging gas logging total hydrocarbon intersection trend chart, reading corresponding well bottom pressure difference equivalent density delta P coordinate data according to the trend chart, and calculating the well bottom pressure difference equivalent density delta P coordinate data according to the well bottom pressure difference-logging gas logging total hydrocarbon intersection trend chart. And finally calculating the stratum pressure equivalent density of the stratum mudstone section of the target well. According to the method, the drilled reference well and the positively-drilled target well which are located in the same block serve as processing objects, the formation pressure calculation method based on logging information and the wellbore pressure difference are combined with the gas logging total hydrocarbon response characteristics, the formation pressure of the positively-drilled target well is accurately obtained while drilling, and the method has the advantages of timeliness and accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of methods for obtaining formation pressure in oil drilling, and is a method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics. Background Art

[0002] In recent years, the field of oil exploration has gradually developed towards deep formations and complex structural areas. The means of monitoring formation pressure while drilling have been unable to meet the increasingly complex drilling situation. Due to the lack of accurate monitoring of formation pressure while drilling, drilling engineering accidents such as leakage, overflow, well kick, and blowout often occur, causing huge economic losses and endangering the personal safety of construction personnel. At present, the main methods for monitoring formation pressure while drilling include Sigma method, DC index method, logging while drilling method, etc. Sigma method and DC index method involve many engineering parameters, and the human factors have a great influence in the calculation process, resulting in poor accuracy of formation pressure monitoring while drilling. Although the logging while drilling method has a high accuracy rate in formation pressure monitoring, it cannot be widely popularized due to cost constraints. Therefore, in order to achieve accurate and rapid acquisition of formation pressure while drilling, it is a problem that must be solved in the exploration and development of deep formations and complex structural areas to study a method for monitoring formation pressure while drilling that is both economical and accurate. Summary of the invention

[0003] The present invention provides a method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of large influence of human factors and poor accuracy in the calculation process of existing while-drilling formation pressure monitoring methods.

[0004] The technical solution of the present invention is achieved by the following measures: A method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics, comprising the following steps:

[0005] Step 1: Collect and organize the logging data, logging gas logging total hydrocarbon data, and drilling fluid density data of three or more reference wells drilled in the same block after drilling, wherein the logging data includes rock density and acoustic wave time difference of mudstone sections at different burial depths, and collect the logging gas logging total hydrocarbon data and drilling fluid density data of the target well being drilled in real time;

[0006] Step 2: Based on the rock density data of one of the reference wells collected in step 1, calculate the overburden pressure of the reference well;

[0007] Based on the acoustic time difference data of mudstone sections at different burial depths of the reference well collected and sorted in step 1, a normal compaction trend line is established, and the formation pressure equivalent density of the reference well is calculated;

[0008] Step 3: Calculate the bottom hole pressure difference equivalent density of the mudstone sections at different burial depths of the reference well based on the formation pressure of the mudstone sections at different burial depths of the reference well calculated in step 2 and the drilling fluid density used at the same well depth of the reference well;

[0009] Step 4: Repeat steps 2 and 3 to calculate the formation pressure equivalent density P of the mudstone sections at different burial depths in the remaining reference wells. P The equivalent density ΔP of the bottom hole pressure difference in mudstone sections with different buried depths;

[0010] Step 5: intersect the logging gas logging total hydrocarbon data of three or more wells in the same formation mudstone section collected and sorted out in step 1 with the bottom hole pressure difference equivalent density ΔP data of the same formation mudstone section calculated based on step 4, establish a trend line according to the trend of sample landing points, and draw a bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram;

[0011] Step 6: Substitute the total hydrocarbon data of the target well in the same formation mudstone section acquired in step 1 into the bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram established in step 5 to read the corresponding bottom hole pressure difference equivalent density ΔP coordinate data;

[0012] Step 7: Based on the corresponding bottom hole pressure difference equivalent density ΔP coordinate data read in step 6 and the drilling fluid density used in the mudstone section of the same well depth of the target well acquired in step 1, the formation pressure equivalent density of the mudstone section of the formation of the target well is calculated, and then the formation pressure data can be obtained according to the conversion relationship between the formation pressure equivalent density and the formation pressure.

[0013] The pressure equivalent density is equal to the pressure at a given depth divided by the product of the depth and the acceleration of gravity, that is, pressure equivalent density = pressure at a given depth / (depth x acceleration of gravity). The pressure equivalent density data can be converted into the corresponding pressure.

[0014] The following are further optimizations and / or improvements to the above technical solutions:

[0015] In step 2 above, the overburden pressure of the reference well is calculated using the following formula:

[0016]

[0017] Among them, G ob is the pressure gradient of the overburden at a certain depth, g / ml; ρ w 、h w is water density and water depth, g / cm 3 , m; ρ0, h o is the average density and thickness of the upper formation section without density logging, g / cm 3 , m; ρ bi is the density scatter data at a certain depth, g / cm 3, Δh is the depth interval, m.

[0018] In step 2 above, the equivalent density of the formation pressure of the reference well is calculated using the following Eaton formula:

[0019]

[0020] Among them, P p is the formation pressure equivalent density, g / cm 3 ;P ob is the pressure equivalent density of the overburden, g / cm 3 ;P h is the equivalent density of the hydrostatic pressure of the formation, g / cm 3 , Δt n is the time difference when the formation is normally compacted, us / m; Δt0 is the measured acoustic time difference of the formation, us / m; N is the Eaton index, a coefficient related to the formation.

[0021] In the above step 3, the equivalent density of the bottom hole pressure difference of the mudstone sections at different burial depths of the reference well is calculated using the following formula:

[0022] ΔP=P p -ρ i

[0023] Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i Drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

[0024] In the above step 7, the formation pressure equivalent density of the mudstone section of the target well is calculated using the following formula:

[0025] P p =ΔP+ρ i

[0026] Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

[0027] The present invention takes the drilled reference wells and the target wells being drilled in the same block as the processing objects, combines the formation pressure calculation method based on logging data and the wellbore pressure difference with the gas logging total hydrocarbon response characteristics, and accurately obtains the formation pressure of the target well being drilled while drilling, which has the characteristics of timeliness and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attached Figure 1 This is a flow chart of the method for obtaining formation pressure while drilling based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to the present invention;

[0029] Attached Figure 2 This is the cross trend diagram of the bottom hole pressure difference and the total hydrocarbon of the mud logging gas logging in a certain mudstone section of the reference well;

[0030] Attached Figure 3 This is the bottom hole pressure difference reading diagram for a certain mudstone section of the target well. DETAILED DESCRIPTION

[0031] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0032] The present invention improves the formation pressure monitoring while drilling method, is applicable to the formation pressure acquisition while drilling of various gas logging total hydrocarbon display layers, and forms a method for acquiring formation pressure while drilling based on wellbore pressure difference and gas logging total hydrocarbon response characteristics. The method is easy to acquire data, and the formation pressure is acquired without affecting the drilling construction progress. The cost is low, and the accuracy is higher than that of the Sigma method and the DC index method. It is applicable to both water-based and oil-based drilling fluids, enriching the means of formation pressure monitoring while drilling. This technology, which is both economical and accurate, will have good application prospects.

[0033] The present invention will be further described below in conjunction with embodiments:

[0034] Example

[0035] As attached Figure 1 As shown, the method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics includes the following steps:

[0036] Step 1: Collect and organize the logging data, logging gas logging total hydrocarbon data, and drilling fluid density data of three or more reference wells drilled in the same block after completion of drilling. The logging data includes rock density and acoustic wave time difference of mudstone sections at different burial depths, and collect the logging gas logging total hydrocarbon data and drilling fluid density data of the target well being drilled in real time;

[0037] Step 2: Based on the rock density data of one of the reference wells collected in step 1, the overburden pressure of the reference well is calculated using the following formula:

[0038]

[0039] Among them, G ob is the pressure gradient of the overburden at a certain depth, g / ml; ρ w 、h w is water density and water depth, g / cm 3 , m; ρ0, h ois the average density and thickness of the upper formation section without density logging, g / cm 3 , m; ρ bi is the density scatter data at a certain depth, g / cm 3 , Δh is the depth interval, m;

[0040] Based on the acoustic time difference data of mudstone sections at different burial depths of the reference well collected in step 1, a normal compaction trend line is established, and the formation pressure equivalent density of the reference well is calculated using the following Eaton formula:

[0041]

[0042] Among them, P p is the formation pressure equivalent density, g / cm 3 ;P ob is the pressure equivalent density of the overburden, g / cm 3 ;P h is the equivalent density of the hydrostatic pressure of the formation, g / cm 3 , Δt n is the time difference when the formation is normally compacted, us / m; Δt0 is the measured acoustic time difference of the formation, us / m; N is the Eaton index, a coefficient related to the formation;

[0043] Step 3: Based on the formation pressure of the mudstone sections at different burial depths of the reference well calculated in step 2 and the drilling fluid density used at the same depth of the reference well, the bottom hole pressure difference equivalent density of the mudstone sections at different burial depths of the reference well is calculated using the following formula:

[0044] ΔP=P p -ρ i

[0045] Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i Drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 ;

[0046] Step 4: Repeat steps 2 and 3 to calculate the formation pressure equivalent density P of the mudstone sections at different burial depths in the remaining reference wells. P The equivalent density ΔP of the bottom hole pressure difference in mudstone sections with different buried depths;

[0047] Step 5: intersect the logging gas logging total hydrocarbon data of three or more wells in the same formation mudstone section collected and sorted out in step 1 with the bottom hole pressure difference equivalent density ΔP data of the same formation mudstone section calculated based on step 4, establish a trend line according to the trend of sample landing points, and draw a bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram;

[0048] Step 6: Substitute the total hydrocarbon data of the target well in the same formation mudstone section acquired in step 1 into the bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram established in step 5 to read the corresponding bottom hole pressure difference equivalent density ΔP coordinate data;

[0049] Step 7: Based on the corresponding bottom hole pressure difference equivalent density ΔP coordinate data read in step 6 and the drilling fluid density used in the mudstone section of the target well at the same well depth acquired in step 1, the formation pressure equivalent density of the mudstone section of the target well is calculated, and then the formation pressure data can be obtained according to the conversion relationship between the formation pressure equivalent density and the formation pressure;

[0050] The formation pressure equivalent density of the mudstone section of the target well is calculated using the following formula:

[0051] P p =ΔP+ρ i

[0052] Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

[0053] Implementation Cases

[0054] Taking Well Fu54 in the Fukang Sag of the Junggar Basin as an example, a method for obtaining formation pressure while drilling based on wellbore pressure difference and gas logging total hydrocarbon response characteristics includes the following steps:

[0055] Step 1: Collect and sort out the logging data, logging gas logging total hydrocarbon data, and drilling fluid density data of the four reference wells KT1, Fu48, Fu49, and Fu51 in the block after drilling. The logging data includes rock density and acoustic wave time difference of mudstone sections at different buried depths, and collect the logging gas logging total hydrocarbon data and drilling fluid density data of the target well Fu54 in real time (Table 1);

[0056] Step 2: Based on the rock density data of the four drilled reference wells KT1, Fu48, Fu49, and Fu51 collected in step 1, the overburden pressure of the reference wells is calculated using the following formula:

[0057]

[0058] Among them, G ob is the pressure gradient of the overburden at a certain depth, g / ml; ρ w 、h w is water density and water depth, g / cm 3 , m; ρ0, h ois the average density and thickness of the upper formation section without density logging, g / cm 3 , m; ρ bi is the density scatter data at a certain depth, g / cm 3 , Δh is the depth interval, m.

[0059] Based on the acoustic time difference data of mudstone sections at different burial depths of four reference wells collected in step 1, a normal compaction trend line is established, and the formation pressure equivalent density of the reference well is calculated using the following Eaton formula:

[0060]

[0061] Among them, P p is the formation pressure equivalent density, g / cm 3 ;P ob is the pressure equivalent density of the overburden, g / cm 3 ;P h is the equivalent density of the hydrostatic pressure of the formation, g / cm 3 , Δt n is the time difference when the formation is normally compacted, us / m; Δt0 is the measured acoustic time difference of the formation, us / m; N is the Eaton index, a coefficient related to the formation, and the value of N in the Fukang Sag of the Junggar Basin is 1.5.

[0062] Step 3: Apply the formation pressure of a certain mudstone section of the four reference wells calculated in step 2 and the drilling fluid density at the same depth of the reference well to calculate the equivalent density of the bottom hole pressure difference of a certain mudstone section of the reference well using the following formula:

[0063] ΔP=P p -ρ i

[0064] Among them, P P is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

[0065] Step 4: The collected and collated logging gas logging total hydrocarbon data of a certain formation mudstone section of the four reference wells are intersected with the calculated bottom hole pressure difference equivalent density ΔP data of a certain formation mudstone section (Table 2), and a trend line is established according to the trend of sample landing points. The correlation coefficient of the trend line is 0.968, and a bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram is drawn ( Figure 2 ).

[0066] Step 5: Substitute the real-time acquired while-drilling logging gas logging total hydrocarbon data of a certain formation mudstone section of the target well Fu54 into the reference well bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram to read the corresponding bottom hole pressure difference equivalent density ΔP coordinate data ( Figure 3 );

[0067] Step 6: Apply the bottom hole pressure difference of a certain mudstone section in the target well Fu54 and the density of the drilling fluid used at the same well depth in a certain mudstone section in the target well Fu54 to calculate the formation pressure equivalent density of a certain mudstone section in the target well Fu54. The calculation is performed using the following formula:

[0068] P p =ΔP+ρ i

[0069] Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

[0070] The total hydrocarbon value of the target well Fu54 in a certain formation mudstone section is 5066ppm. The reference well bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend chart is used to read the bottom hole pressure difference equivalent density ΔP coordinate data of a certain formation mudstone section of the target well Fu54, which is 0.11. The density of the drilling fluid used to collect the mudstone section is 1.66g / cm 3 , calculate the formation pressure equivalent density P of a mudstone section of a formation in the target well Fu54 p 1.55g / cm 3 After the target well Fu54 was drilled, the logging data was collected and the formation pressure calculation method in step 2 was applied to calculate the formation pressure equivalent density of a mudstone section of a formation in the target well Fu54, which was 1.52 g / cm 3 , the accuracy rate is 98.06%, and the conclusion is consistent with and meets the needs of drilling construction.

[0071] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

[0072] Table 1. Real-time collection of total hydrocarbon and drilling fluid density data during logging while drilling

[0073]

[0074] Table 2 Drilling fluid density and logging gas logging total hydrocarbon collection table of a certain formation mudstone section of four reference wells

[0075]

Claims

1. A method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics, characterized in that The following steps are involved: Step 1: Collect and organize the logging data, logging gas logging total hydrocarbon data, and drilling fluid density data of three or more reference wells drilled in the same block after completion of drilling. The logging data includes rock density and acoustic wave time difference of mudstone sections at different burial depths, and collect the logging gas logging total hydrocarbon data and drilling fluid density data of the target well being drilled in real time; Step 2: Based on the rock density data of one of the reference wells collected in step 1, calculate the overburden pressure of the reference well; Based on the acoustic time difference data of mudstone sections at different burial depths of the reference well collected and sorted in step 1, a normal compaction trend line is established, and the formation pressure equivalent density of the reference well is calculated; Step 3: Calculate the bottom hole pressure difference equivalent density of the mudstone sections at different burial depths of the reference well based on the formation pressure of the mudstone sections at different burial depths of the reference well calculated in step 2 and the drilling fluid density used at the same well depth of the reference well; Step 4: Repeat steps 2 and 3 to calculate the formation pressure equivalent density P of the mudstone sections at different burial depths in the remaining reference wells. P The equivalent density ΔP of the bottom hole pressure difference in mudstone sections with different buried depths; Step 5: intersect the logging gas logging total hydrocarbon data of three or more wells in the same formation mudstone section collected and sorted in step 1 with the bottom hole pressure difference equivalent density ΔP data of the same formation mudstone section calculated based on step 4, establish a trend line according to the trend of sample landing points, and draw a bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram; Step 6: Substitute the total hydrocarbon data of the target well in the same formation mudstone section acquired in step 1 into the bottom hole pressure difference-logging gas logging total hydrocarbon intersection trend diagram established in step 5 to read the corresponding bottom hole pressure difference equivalent density ΔP coordinate data; Step 7: Based on the corresponding bottom hole pressure difference equivalent density ΔP coordinate data read in step 6 and the drilling fluid density used in the mudstone section of the same well depth of the target well acquired in step 1, the formation pressure equivalent density of the mudstone section of the formation of the target well is calculated, and then the formation pressure data can be obtained according to the conversion relationship between the formation pressure equivalent density and the formation pressure.

2. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 1, characterized in that In step 2, the overburden pressure of the reference well is calculated using the following formula: Among them, G ob is the pressure gradient of the overburden at a certain depth, g / ml; ρ w 、h w is water density and water depth, g / cm 3 , m; ρ0, h o is the average density and thickness of the upper formation section without density logging, g / cm 3 , m; ρ bi is the density scatter data at a certain depth, g / cm 3 , Δh is the depth interval, m.

3. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 1 or 2, characterized in that In step 2, the equivalent density of the formation pressure of the reference well is calculated using the following Eaton formula: Among them, P p is the formation pressure equivalent density, g / cm 3 ;P ob is the pressure equivalent density of the overburden, g / cm 3 ;P h is the equivalent density of the hydrostatic pressure of the formation, g / cm 3 , Δt n is the time difference when the formation is normally compacted, us / m; Δt0 is the measured acoustic time difference of the formation, us / m; N is the Eaton index, a coefficient related to the formation.

4. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 1 or 2, characterized in that In step 3, the bottom hole pressure difference of the mudstone sections at different burial depths of the reference well is calculated using the following formula: ΔP=P p -r i Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i Drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

5. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 3, characterized in that In step 3, the equivalent density of the bottom hole pressure difference of the mudstone sections at different burial depths of the reference well is calculated using the following formula: ΔP=P p -r i Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i Drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

6. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 1 or 2, characterized in that In step 7, the formation pressure equivalent density of the mudstone section of the target well is calculated using the following formula: P p =ΔP+ρ i Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

7. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 3, characterized in that In step 7, the formation pressure equivalent density of the mudstone section of the target well is calculated using the following formula: P p =ΔP+ρ i Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

8. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 4, characterized in that In step 7, the formation pressure equivalent density of the mudstone section of the target well is calculated using the following formula: P p =ΔP+ρ i Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

9. The method for obtaining formation pressure based on wellbore pressure difference and gas logging total hydrocarbon response characteristics according to claim 5, characterized in that In step 7, the formation pressure equivalent density of the mudstone section of the target well is calculated using the following formula: P p =ΔP+ρ i Among them, P p is the formation pressure equivalent density, g / cm 3 ρ i is the drilling fluid density, g / cm 3 ; ΔP is the equivalent density of the bottom hole pressure difference, g / cm 3 .

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