Method and device for predicting interval transit time and formation pressure of undrilled section

Abstract

The invention discloses a method and a device for predicting interval transit time and formation pressure of an undrilled section. The method comprises the following steps: predicting a reference value of interval transit time of a non-drilling section at a specified depth according to a first relation expression of interval transit time and depth of a drilled section; according to the second relation expression between the interval transit time fluctuation data of the drilled section and the depth, the interval transit time fluctuation value of the non-drilled section at the specified depth is predicted; and according to the reference value and the fluctuation value of the interval transit time of the specified depth of the non-drilling section, determining an interval transit time prediction value of the specified depth of the non-drilling section. According to the pre-established compaction trend line relation expression of the interval transit time and the depth of the drilled section, the interval transit time on the compaction trend line of the specified depth of the non-drilled section is obtained; and in combination with the interval transit time prediction value of the specified depth of the non-drilling section, determining a formation pressure prediction value of the specified depth of the non-drilling section. The interval transit time and the formation pressure of the undrilled section can be accurately predicted based on the data of the drilled section, and the prediction result is accurate and reliable.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas drilling engineering, and particularly to a method and device for predicting acoustic travel time and formation pressure of an undrilled section. Background Art

[0002] Formation pressure is an important parameter in oil and gas drilling engineering, which is usually defined as the pressure borne by the fluid in the rock pores. Before drilling the formation, engineering technicians need to predict the formation pressure before drilling to provide safety guarantee for oil and gas drilling.

[0003] There are mainly three types of methods for predicting formation pressure: one is to predict the formation pressure of the formation to be drilled by using the logging data of adjacent wells; the other is to analyze the formation pressure after drilling by using the logging data of the well itself. This method belongs to the re-prediction and analysis after drilling and cannot be predicted before drilling; the third is to predict the formation pressure before drilling by using seismic data. This method generally uses seismic layer velocity to predict formation pressure. Summary of the Invention

[0004] The inventors of the present application have found that for the existing method of predicting the formation pressure of the formation to be drilled by using the logging data of adjacent wells, there are certain prediction errors in the predicted formation pressure; for the method of analyzing the formation pressure after drilling by using the logging data of the well itself, since it belongs to post-event analysis, it is difficult to guide the actual drilling operation on site and cannot accurately predict the formation pressure of the undrilled formation; for the method of predicting the formation pressure before drilling by using seismic data, due to the low resolution accuracy of seismic layer velocity, it is difficult to ensure the prediction accuracy of formation pressure before drilling. Therefore, there is no method in the prior art that can accurately predict the formation pressure of the undrilled section, and the prediction of the formation pressure of the undrilled section has important value in the drilling process.

[0005] In view of the above problems, the present invention is proposed to provide a method and device for predicting acoustic travel time and formation pressure of an undrilled section that can overcome the above problems or at least partially solve the above problems.

[0006] An embodiment of the present invention provides a method for predicting acoustic travel time of an undrilled section, including:

[0007] Predicting a reference value of the acoustic travel time at a specified depth of the undrilled section according to a first relational expression of the acoustic travel time and depth established in advance for the drilled section; the first relational expression is established according to the acoustic travel time scatter data of the drilled section;

[0008] Predicting a fluctuation value of the acoustic travel time at a specified depth of the undrilled section according to a second relational expression of the acoustic travel time fluctuation data and depth established for the drilled section; the second relational expression is established according to the acoustic travel time fluctuation data of the drilled section;

[0009] Determine the predicted value of the acoustic time difference at a specified depth in the un-drilled section based on the reference value and the fluctuation value of the acoustic time difference at the specified depth in the un-drilled section.

[0010] In some alternative embodiments, predicting the reference value of the acoustic time difference at a specified depth in the un-drilled section according to the first relational expression of the acoustic time difference and depth established in advance for the drilled section includes:

[0011] Fitting the acoustic time difference scatter data of the drilled section according to the following formula to obtain the first relational expression of the acoustic time difference and depth of the drilled section:

[0012] Δt' n =ae bh

[0013] where: Δt' n is the acoustic time difference of the drilled section; h is the depth; a and b are coefficients;

[0014] Predict the reference value of the acoustic time difference at the specified depth in the un-drilled section based on the first relational expression and the specified depth in the un-drilled section.

[0015] In some alternative embodiments, establishing the second relational expression between the acoustic time difference fluctuation data of the drilled section and the depth includes:

[0016] Determine the reference value of the acoustic time difference at different depths in the drilled section according to the first relational expression, and determine the acoustic time difference fluctuation values at different depths according to the reference value of the acoustic time difference at different depths in the drilled section and the measured value of the acoustic time difference at the corresponding depth;

[0017] Determine the extreme values of the acoustic time difference fluctuation within different depth windows according to the acoustic time difference fluctuation values at different depths;

[0018] Establish the second relational expression between the fluctuation value of the acoustic time difference and the depth according to the extreme values of the acoustic time difference fluctuation within different depth windows.

[0019] In some alternative embodiments, the determining the extreme values of the acoustic time difference fluctuation within different depth windows according to the acoustic time difference fluctuation values at different depths, and establishing the second relational expression between the fluctuation value of the acoustic time difference and the depth according to the extreme values of the acoustic time difference within different depth windows includes:

[0020] Determine the maximum and minimum fluctuation values of the acoustic time difference within different depth windows according to the acoustic time difference fluctuation values at different depths;

[0021] Establish the maximum fluctuation relational expression between the maximum fluctuation value of the acoustic time difference and the depth and the minimum fluctuation relational expression between the minimum fluctuation value of the acoustic time difference and the depth according to the maximum and minimum fluctuation values of the acoustic time difference within different depth windows.

[0022] In some alternative embodiments, predicting the acoustic time difference fluctuation value at a specified depth in the un-drilled section according to the second relationship expression between the acoustic time difference fluctuation data and the depth established for the drilled section includes:

[0023] Obtaining the maximum and minimum values of the acoustic time difference fluctuations within different depth window ranges in the un-drilled section according to the expression of the maximum fluctuation relationship between the maximum fluctuation value of the acoustic time difference and the depth, and the expression of the minimum fluctuation relationship between the minimum fluctuation value of the acoustic time difference and the depth;

[0024] Determining the acoustic time difference fluctuation values within different depth window ranges in the un-drilled section according to the maximum and minimum values of the acoustic time difference fluctuations within different depth window ranges in the un-drilled section.

[0025] In some alternative embodiments, determining the acoustic time difference fluctuation values within different depth window ranges in the un-drilled section according to the maximum and minimum values of the acoustic time difference fluctuations within different depth window ranges in the un-drilled section includes:

[0026] According to the maximum value of the acoustic time difference fluctuation within the specified depth window range in the un-drilled section Minimum value Using the following formula to obtain the fluctuation value Δt of the acoustic time difference in the un-drilled section f .

[0027]

[0028] Where: L is the number of acoustic time difference scatter points within a depth window range, and R is a random number between 1 and L.

[0029] The embodiments of the present invention further provide a method for predicting the formation pressure in the un-drilled section, including:

[0030] Using the acoustic time difference prediction method for the un-drilled section to predict the acoustic time difference at a specified depth in the un-drilled section;

[0031] Obtaining the acoustic time difference on the compaction trend line at a specified depth in the un-drilled section according to the pre-established relationship expression between the acoustic time difference and the depth of the drilled section; the compaction trend line relationship expression is established based on the acoustic time difference data of the drilled section;

[0032] Determining the formation pressure prediction value at a specified depth in the un-drilled section according to the predicted value of the acoustic time difference at the specified depth in the un-drilled section and the acoustic time difference on the compaction trend line.

[0033] In some alternative embodiments, obtaining the acoustic time difference on the compaction trend line at a specified depth in the un-drilled section according to the pre-established relationship expression between the acoustic time difference and the depth of the drilled section includes:

[0034] According to the acoustic time difference scatter data of the drilled section, fit the compaction trend line according to the following formula:

[0035] lnΔt' n =lnΔt0 - Ch

[0036] Where, Δt' n is the acoustic time difference at the depth h of the drilled section; Δt0 is the acoustic time difference at zero depth; C is the compaction coefficient; h is the depth;

[0037] According to the compaction trend line and the depth of the undrilled section, determine the acoustic time difference on the compaction trend line at the specified depth of the undrilled section.

[0038] In some alternative embodiments, the determining the predicted value of the acoustic formation pressure of the undrilled section based on the predicted value of the acoustic time difference at the specified depth of the undrilled section and the acoustic time difference on the compaction trend line includes:

[0039] Determine the predicted value of the acoustic formation pressure of the undrilled section based on the predicted value of the acoustic time difference at the specified depth of the undrilled section, the acoustic time difference on the compaction trend line, the overburden pressure and the hydrostatic pressure at the specified depth of the undrilled section.

[0040] In some alternative embodiments, the determining the predicted value of the acoustic formation pressure of the undrilled section based on the predicted value of the acoustic time difference at the specified depth of the undrilled section, the acoustic time difference on the compaction trend line, the overburden pressure and the hydrostatic pressure at the specified depth of the undrilled section includes:

[0041] Determine the formation density at the specified depth of the undrilled section according to the seismic layer velocity at the specified depth of the undrilled section and the relationship expression between the seismic layer velocity and the formation density;

[0042] Determine the overburden pressure at the specified depth of the undrilled section according to the formation density at the specified depth of the undrilled section;

[0043] Use the following formula to determine the predicted value of the acoustic formation pressure of the undrilled section:

[0044]

[0045] Where: P P is the predicted value of the formation pressure; P0 is the overburden pressure; P h is the hydrostatic pressure; Δt″ n is the acoustic time difference on the compaction trend line; Δt n is the predicted value of the acoustic time difference of the undrilled section; N is the Eaton index.

[0046] In some alternative embodiments, the Eaton index is determined based on the measured formation pressure, overburden pressure, hydrostatic pressure at different depths of adjacent wells, the acoustic travel time on the compaction trend line, and the measured acoustic travel time at different depths.

[0047] In some alternative embodiments, the measured formation pressure at a specified depth of the un-drilled section is obtained by a formation pressure testing device, and based on the measured acoustic travel time obtained from well logging and the measured formation pressure, the prediction error of the predicted value of the acoustic travel time and the prediction error of the predicted value of the formation pressure at the specified depth of the un-drilled section are determined.

[0048] It is determined whether the prediction error of the predicted value of the acoustic travel time and the prediction error of the predicted value of the formation pressure at the specified depth of the un-drilled section meet the error requirements.

[0049] In some alternative embodiments, the formation pressure testing device includes:

[0050] A syringe, a piston, and a needle disposed in a hole channel at a specified depth of the formation, and the hole channel is sealed from the wellbore by a packer;

[0051] Surface equipment and a fluid pressure sensor connected by a cable, and the fluid sensor is disposed at the needle for measuring the formation pressure.

[0052] An embodiment of the present invention further provides an acoustic travel time prediction device for an un-drilled section, including:

[0053] A first prediction module for predicting a reference value of the acoustic travel time at a specified depth of the un-drilled section according to a first relationship expression between the acoustic travel time and depth established in advance for the drilled section; the first relationship expression is established based on the acoustic travel time scatter data of the drilled section;

[0054] A second prediction module for predicting a fluctuation value of the acoustic travel time at a specified depth of the un-drilled section according to a second relationship expression between the acoustic travel time fluctuation data and depth established for the drilled section; the second relationship expression is established based on the acoustic travel time fluctuation data of the drilled section;

[0055] An acoustic travel time determination module for determining a predicted value of the acoustic travel time at a specified depth of the un-drilled section according to the reference value and the fluctuation value of the acoustic travel time at the specified depth of the un-drilled section.

[0056] An embodiment of the present invention further provides a formation pressure prediction device for an un-drilled section, including:

[0057] The above-mentioned acoustic travel time prediction device for an un-drilled section, which is used to predict the acoustic travel time at a specified depth of the un-drilled section;

[0058] An acquisition module, configured to obtain the acoustic time difference on the compaction trend line at a specified depth of an un-drilled section according to a pre-established relationship expression between the acoustic time difference and depth of a drilled section; the relationship expression of the compaction trend line is established based on the acoustic time difference data of the drilled section.

[0059] A pressure determination module, configured to determine a predicted formation pressure value at a specified depth of an un-drilled section according to a predicted acoustic time difference value at the specified depth of the un-drilled section and the acoustic time difference on the compaction trend line.

[0060] An embodiment of the present invention further provides a computer storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, the above-mentioned acoustic time difference prediction method and / or formation pressure prediction method for an un-drilled section are implemented.

[0061] An embodiment of the present invention further provides a prediction device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, the above-mentioned acoustic time difference prediction method and / or formation pressure prediction method for an un-drilled section are implemented.

[0062] The beneficial effects of the above technical solutions provided by the embodiments of the present invention at least include:

[0063] The acoustic time difference prediction method for an un-drilled section provided by the embodiment of the present invention predicts a reference value of the acoustic time difference at a specified depth of the un-drilled section according to a pre-established first relationship expression between the acoustic time difference and depth of the drilled section; according to the established second relationship expression between the acoustic time difference fluctuation data of the drilled section and depth, it predicts the acoustic time difference fluctuation value at the specified depth of the un-drilled section, and corrects the predicted reference value based on the fluctuation value to obtain the final predicted acoustic time difference value. This method not only considers the existing acoustic time difference data of the drilled section, but also considers the inaccurate factors existing in the prediction, and makes necessary adjustments, so as to obtain an accurate predicted acoustic time difference result, which is used to guide actual drilling operations, has good reference value, and provides more reliable data support for drilling operations.

[0064] The formation pressure prediction method for the un-drilled section provided by the embodiments of the present invention predicts the formation pressure at a specified depth in the un-drilled section based on the predicted acoustic travel time difference and the acoustic travel time difference on the compaction trend line at the specified depth in the un-drilled section obtained based on the compaction trend line. When predicting the acoustic travel time difference, the predicted reference value is corrected based on the fluctuation value to obtain the final predicted value of the acoustic travel time difference. This method not only considers the existing acoustic travel time difference data in the drilled section but also takes into account the inaccurate factors in the prediction, making necessary adjustments to obtain an accurate prediction result of the acoustic travel time difference. On this basis, further combining the acoustic travel time difference on the compaction trend line and other relevant factors to predict the formation pressure can obtain a more accurate prediction result. This method predicts the formation pressure of the un-drilled section based on the drilled section and corrects and adjusts the errors in the prediction process to ensure the prediction accuracy of the pre-drilling prediction, which is used to guide the actual drilling operation, has good reference value, and provides more reliable data support for the drilling operation.

[0065] Other features and advantages of the present invention will be described in the following specification, and in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures specifically pointed out in the written specification, claims, and drawings.

[0066] The technical solutions of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0067] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0068] Figure 1 is a flow chart of the method for predicting the acoustic travel time difference in the un-drilled section in the first embodiment of the present invention;

[0069] Figure 2 is a schematic block diagram of the principle for predicting the acoustic travel time difference and formation pressure in the un-drilled section in the embodiments of the present invention;

[0070] Figure 3 is a flow chart of the method for predicting the formation pressure in the un-drilled section in the second embodiment of the present invention;

[0071] Figure 4 is a schematic diagram of the formation pressure testing equipment in the third embodiment of the present invention;

[0072] Figure 5 is the acoustic travel time difference data of the drilled section of Well AG2 in the third embodiment of the present invention;

[0073] Figure 6 is the fluctuation value of the acoustic travel time difference of the drilled section of Well AG2 in the third embodiment of the present invention;

[0074] Figure 7a It is the maximum value of the acoustic time difference fluctuation value in the drilled section of Well AG2 in the third embodiment of the present invention

[0075] Figure 7b It is the minimum value of the acoustic time difference fluctuation value in the drilled section of Well AG2 in the third embodiment of the present invention;

[0076] Figure 8 It is the fluctuation value of the acoustic time difference in the undrilled section of Well AG2 in the third embodiment of the present invention;

[0077] Figure 9 It is the predicted value of the acoustic time difference in the undrilled section of Well AG2 in the third embodiment of the present invention;

[0078] Figure 10 It is the seismic layer velocity data of Well AG2 in the third embodiment of the present invention;

[0079] Figure 11 It is the predicted density value of Well AG2 in the third embodiment of the present invention;

[0080] Figure 12 It is the acoustic time difference data of Well AG1 in the third embodiment of the present invention;

[0081] Figure 13 It is the comparison chart of the acoustic time difference results of Well AG2 in the third embodiment of the present invention;

[0082] Figure 14 It is the comparison chart of the formation pressure results of Well AG2 in the third embodiment of the present invention;

[0083] Figure 15 It is the structural schematic diagram of the acoustic time difference prediction device for the undrilled section in the embodiment of the present invention;

[0084] Figure 16 It is the structural schematic diagram of the formation pressure prediction device for the undrilled section in the embodiment of the present invention.

[0085] In the figure: 1. Ground equipment; 2. Cable; 3. Hole channel; 4. Packer; 5. Syringe; 6. Piston; 7. Needle; 8. Fluid pressure sensor; Detailed implementation manners

[0086] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0087] To solve the problems of inaccurate prediction of pre-drilling formation pressure and low accuracy of prediction results in the existing technology, an embodiment of the present invention provides a method for predicting formation pressure in an un-drilled section, which can accurately predict the acoustic travel time and formation pressure in the un-drilled section based on the data of the drilled section, and the prediction results are accurate and reliable.

[0088] Embodiment 1

[0089] Embodiment 1 of the present invention provides a method for predicting acoustic travel time in an un-drilled section, and its process is as Figure 1 shown, and the principle block diagram for implementation can be seen in Figure 2 , including the following steps:

[0090] Step S101: According to the first relational expression of acoustic travel time and depth established in advance for the drilled section, predict the reference value of the acoustic travel time at a specified depth in the un-drilled section. Among them, the first relational expression is established based on the scattered point data of acoustic travel time in the drilled section.

[0091] Step S102: According to the second relational expression established for the fluctuation data of acoustic travel time and depth in the drilled section, predict the fluctuation value of the acoustic travel time at a specified depth in the un-drilled section.

[0092] Step S103: Determine the predicted value of the acoustic travel time at a specified depth in the un-drilled section according to the reference value and the fluctuation value of the acoustic travel time at the specified depth in the un-drilled section.

[0093] As seen in Figure 2 shown, predicting the formation pressure in the un-drilled section according to the well logging data of the drilled section includes predicting the acoustic travel time in the un-drilled section and calculating the density in the un-drilled section. In this embodiment, the prediction of the acoustic travel time is described. The prediction of the acoustic travel time includes the determination of the reference value and the determination of the fluctuation value, and the acoustic travel time in the un-drilled section can be obtained according to the reference value and the fluctuation value.

[0094] In the above step S101, the first relational expression of acoustic travel time and depth for the drilled section can be established in advance for subsequent prediction. The first relational expression can be a curve of the acoustic travel time in the drilled section fitted with respect to depth. The process of establishing the first relational expression includes:

[0095] Screen out the scattered point data of acoustic travel time at a specified depth interval from the well logging data of the drilled section, and then use Matlab to fit the screened scattered point data of acoustic travel time according to the following formula to obtain the first relational expression of acoustic travel time and depth in the drilled section:

[0096] Δt' n =ae bh

[0097] where: Δt' n is the acoustic travel time of the drilled section; h is the depth; a and b are coefficients;

[0098] In this embodiment, the specified depth interval can be set as needed. For example, the depth interval can be 0.1 m or other values.

[0099] After fitting the first relationship curve between the acoustic travel time difference and depth of the drilled section, the reference value of the acoustic travel time difference at the specified depth of the undrilled section can be predicted based on the first relationship expression and the specified depth of the undrilled section. Specifically, the depth of the undrilled section can be substituted into the first relationship expression to obtain the predicted reference value of the acoustic travel time difference at the specified depth of the undrilled section. See Figure 2 the steps in the lower box of the reference value.

[0100] In the above step S102, a second relationship expression between the acoustic travel time difference fluctuation data and depth of the drilled section can be established in advance. The second relationship expression is a curve of the acoustic travel time difference fluctuation value of the drilled section fitted with respect to depth. After establishing the second relationship expression, the predicted fluctuation value of the acoustic travel time difference of the undrilled section can be obtained based on the second relationship expression. See Figure 2 the relevant steps in the lower box of the fluctuation value.

[0101] The process of establishing the second relationship expression includes:

[0102] 1) According to the first relationship expression, determine the reference values of the acoustic travel time difference at different depths of the drilled section. According to the reference values of the acoustic travel time difference at different depths of the drilled section and the measured values of the acoustic travel time difference at the corresponding depths, determine the fluctuation values of the acoustic travel time difference at different depths;

[0103] Substitute the depth h of the drilled section into the first relationship expression to calculate the reference value of the acoustic travel time difference of the drilled section. Subtract the reference value of the acoustic travel time difference of the drilled section from the measured value of the acoustic travel time difference of the drilled section to obtain the fluctuation value of the acoustic travel time difference of the drilled section. The following formula can be used to calculate the fluctuation value of the acoustic travel time difference of the drilled section:

[0104] Δt′ f =Δt′ n -Δt′ b

[0105] In the formula: Δt' f is the fluctuation value of the acoustic travel time difference of the drilled section; Δt' n is the measured value of the acoustic travel time difference of the drilled section; Δt' b is the reference value of the acoustic travel time difference of the drilled section. The unit of the acoustic travel time difference can be μs / m.

[0106] Based on the fluctuation values of the acoustic travel time difference at different depths of the drilled section, establish a matrix of the fluctuation values of the acoustic travel time difference of the drilled section.

[0107] In this embodiment, taking the depth interval of acoustic travel time data as 0.1 m as an example, there are 10 acoustic travel time scatter data per meter. Therefore, a matrix of acoustic travel time fluctuation values for the drilled well section in meters (assuming the depth of the drilled well section is k meters) can be established as follows:

[0108]

[0109] In the formula: Δt' f(ij) is the acoustic travel time fluctuation value at the depth of the (i + 0.1j) -th meter in the drilled well section;

[0110] 2) Determine the extreme values of acoustic travel time fluctuations within different depth window ranges according to the acoustic travel time fluctuation values at different depths; specifically, determine the maximum and minimum acoustic travel time fluctuation values within different depth window ranges according to the acoustic travel time fluctuation values at different depths.

[0111] Based on the matrix of acoustic travel time fluctuation values for the drilled well section, screen out the maximum and minimum values of acoustic travel time fluctuation values within different depth window ranges, for example, within each meter range; taking the 10 acoustic travel time fluctuation values Δt' f(ij) at the i -th meter as an example:

[0112] The maximum value can be expressed as:

[0113] The minimum value can be expressed as:

[0114] 3) Establish a second relationship expression between the fluctuation value of acoustic travel time and depth according to the extreme values of acoustic travel time fluctuations within different depth window ranges; specifically, establish a maximum fluctuation relationship expression between the maximum acoustic travel time fluctuation value and depth and a minimum fluctuation relationship expression between the minimum acoustic travel time fluctuation value and depth according to the maximum and minimum acoustic travel time fluctuation values within different depth window ranges.

[0115] According to the maximum and minimum values of acoustic travel time fluctuation values within different depth window ranges, for example, within each meter range, establish the drilled well section and a functional relationship with respect to depth. The maximum and minimum values of acoustic travel time fluctuation values and the corresponding depths can be fitted using Matlab according to the following formula to determine the coefficients m, n, m', n', and establish and a second relationship expression with respect to depth h, where:

[0116] The maximum fluctuation relationship expression between the maximum acoustic travel time fluctuation value and depth is:

[0117] The minimum fluctuation relationship expression between the minimum acoustic travel time fluctuation value and depth is:

[0118] In the formula: is the maximum value of the acoustic time difference fluctuation per meter in the drilled section; is the minimum value of the acoustic time difference fluctuation per meter in the drilled section; h is the depth; m, n, m′, n′ are coefficients.

[0119] After establishing the second relational expression, it further includes predicting the acoustic time difference fluctuation value at a specified depth in the undrilled section according to the second relational expression.

[0120] 4) Obtain the maximum and minimum values of the acoustic time difference fluctuation values within different depth window ranges in the undrilled section according to the maximum fluctuation relationship expression between the maximum value of the acoustic time difference and the depth and the minimum fluctuation relationship expression between the minimum value of the acoustic time difference and the depth;

[0121] Obtain the maximum value of the acoustic time difference fluctuation per meter in the undrilled section and the minimum value The depth of the undrilled section can be substituted into the second relational expression to obtain the maximum value of the acoustic time difference fluctuation per meter in the undrilled section and the minimum value Where:

[0122]

[0123]

[0124] In the formula: is the maximum value of the acoustic time difference fluctuation per meter in the undrilled section; is the minimum value of the acoustic time difference fluctuation per meter in the undrilled section; H is the depth; m, n, m′, n′ are coefficients.

[0125] 5) Determine the acoustic time difference fluctuation values within different depth window ranges in the undrilled section according to the maximum and minimum values of the acoustic time difference fluctuation values within different depth window ranges in the undrilled section.

[0126] Based on the maximum value of the acoustic time difference fluctuation per meter in the undrilled section the minimum value The fluctuation value Δt of the acoustic time difference in the undrilled section is obtained by using the following formula f .

[0127]

[0128] Where: Δt f is the fluctuation value of the acoustic time difference in the undrilled section; is the minimum value of the acoustic time difference fluctuation per meter in the undrilled section; is the maximum value of the fluctuation value of the acoustic travel time per meter in the un-drilled section; L is the number of scatter points of the acoustic travel time within a depth window range, and R is a random number between 1 and L; in this embodiment, the unit is meter, and the depth interval of the acoustic travel time data is 0.1 meter, so L is 10.

[0129] In the above step S103, the reference value of the acoustic travel time in the un-drilled section and the fluctuation value of the acoustic travel time in the un-drilled section are summed to obtain the acoustic travel time of the un-drilled section.

[0130] For example: the reference value Δt of the acoustic travel time in the un-drilled section b and the fluctuation value Δt f are added to obtain the acoustic travel time Δt of the un-drilled section n :

[0131] Δt n = Δt b + Δt f

[0132] In the formula: Δt n is the acoustic travel time of the un-drilled section; Δt b is the reference value of the acoustic travel time in the un-drilled section; Δt f is the fluctuation value of the acoustic travel time in the un-drilled section.

[0133] The method for predicting the acoustic travel time of the un-drilled section provided by the embodiment of the present invention predicts the reference value of the acoustic travel time at a specified depth in the un-drilled section according to the first relational expression between the acoustic travel time and the depth of the drilled section established in advance; according to the second relational expression between the acoustic travel time fluctuation data of the drilled section and the depth established, predicts the fluctuation value of the acoustic travel time at a specified depth in the un-drilled section, and corrects the predicted reference value based on the fluctuation value to obtain the final predicted value of the acoustic travel time. This method not only considers the existing acoustic travel time data of the drilled section, but also considers the inaccurate factors existing in the prediction, and makes necessary adjustments, so as to obtain an accurate predicted result of the acoustic travel time. The method for predicting the acoustic travel time of the un-drilled section provided by the embodiment of the present invention can provide more reliable data for predicting the formation pressure of the un-drilled section, which is used to guide the actual drilling operation, has good reference value, and provides more reliable data support for the drilling operation.

[0134] Embodiment Two

[0135] The second embodiment of the present invention provides a method for predicting the formation pressure of an un-drilled section, and its process is as Figure 3 shown, and its principle is referred to Figure 2 shown, including the following steps:

[0136] Step S201: Predict the acoustic travel time at a specified depth in the un-drilled section based on the drilled section.

[0137] The acoustic time difference prediction method provided in Embodiment 1 can be used to predict the acoustic time difference at a specified depth in the un-drilled section.

[0138] Step S202: Obtain the acoustic time difference on the compaction trend line at the specified depth in the un-drilled section according to the pre-established relationship expression between the acoustic time difference and depth of the drilled section; wherein, the relationship expression of the compaction trend line is established based on the acoustic time difference data of the drilled section.

[0139] Step S203: Determine the predicted formation pressure value at the specified depth in the un-drilled section according to the predicted acoustic time difference value at the specified depth in the un-drilled section and the acoustic time difference on the compaction trend line.

[0140] In an optional embodiment, in the above step S202, obtaining the acoustic time difference on the compaction trend line at the specified depth in the un-drilled section according to the pre-established relationship expression between the acoustic time difference and depth of the drilled section includes:

[0141] According to the acoustic time difference scatter data of the drilled section, fit the compaction trend line according to the following formula:

[0142] lnΔt' n =lnΔt0 - Ch

[0143] where, Δt' n is the acoustic time difference at the depth h of the drilled section; Δt0 is the acoustic time difference at zero depth; C is the compaction coefficient; h is the depth;

[0144] According to the compaction trend line and the depth of the un-drilled section, determine the acoustic time difference on the compaction trend line at the specified depth in the un-drilled section.

[0145] When fitting the normal compaction trend line, the acoustic time difference data of the shale formation can be screened from the well logging data of the drilled section, and then the screened acoustic time difference scatter data is used in Matlab to fit the compaction trend line according to the above formula to determine the coefficients C and Δt0, and establish the functional relationship of the acoustic time difference Δt' n with respect to the depth h. Then, substitute the depth of the un-drilled section into the compaction trend line relationship to obtain the acoustic time difference on the compaction trend line at the specified depth in the un-drilled section.

[0146] In an optional embodiment, in the above step S203, determining the predicted formation pressure value at the specified depth in the un-drilled section according to the predicted acoustic time difference value at the specified depth in the un-drilled section and the acoustic time difference on the compaction trend line includes: determining the predicted acoustic formation pressure value at the specified depth in the un-drilled section according to the predicted acoustic time difference value at the specified depth in the un-drilled section, the acoustic time difference on the compaction trend line, and the overburden pressure and hydrostatic pressure at the specified depth in the un-drilled section. Specifically, it may include the following process:

[0147] 1) Determine the formation density at a specified depth in the un-drilled section based on the seismic interval velocity at the specified depth in the un-drilled section and the relationship expression between the seismic interval velocity and the formation density.

[0148] Based on the relationship between the seismic interval velocity and the formation density, substitute the seismic interval velocity V a into the following formula to obtain the density ρ of the un-drilled formation:

[0149]

[0150] In the formula: ρ is the formation density; V a is the seismic interval velocity.

[0151] 2) Determine the overburden pressure at a specified depth in the un-drilled section based on the formation density at the specified depth in the un-drilled section.

[0152] 3) Prediction of formation pressure in the un-drilled section.

[0153] According to the predicted acoustic travel time and the acoustic travel time on the compaction trend line at a specified depth in the un-drilled section, use the following formula to determine the predicted value of the acoustic formation pressure in the un-drilled section:

[0154]

[0155] Where: P P is the predicted value of formation pressure; P0 is the overburden pressure; P h is the hydrostatic pressure; Δt' n ' is the acoustic travel time on the compaction trend line; Δt n is the predicted acoustic travel time in the un-drilled section; N is the Eaton exponent.

[0156] The overburden pressure P0 can be the vertical overburden pressure, which is obtained by integrating the density ρ with respect to depth. ρ is the density, and the density ρ can be obtained from density logging data; the hydrostatic pressure P h is obtained by integrating the water density along the depth direction; Δt' n ' is the acoustic travel time on the normal compaction trend line, which is obtained according to the fitted normal compaction trend line.

[0157] When calculating the formation pressure in the un-drilled section using the Eaton formula as described above, the Eaton exponent N can be determined in advance. The Eaton exponent is related to the actual area and can be determined based on the measured formation pressure, overburden pressure, hydrostatic pressure, acoustic travel time on the compaction trend line, and measured acoustic travel time at different depths in adjacent wells.

[0158] Substitute the formation pressure, overburden pressure, hydrostatic pressure, acoustic travel time on the normal trend line, and measured acoustic travel time at the depth of the measured points in the adjacent well into the following formula to calculate it by inversion:

[0159]

[0160] Wherein: P' p is the measured value of the formation pressure of the adjacent well; P'0 is the overlying formation pressure of the adjacent well; P' h is the hydrostatic pressure; Δt″″ is the measured acoustic travel time difference of the adjacent well; Δt″′ n is the acoustic travel time difference on the normal compaction trend line of the adjacent well.

[0161] The present invention proposes a method for predicting the formation pressure of the un-drilled section, which ensures the prediction accuracy of the formation pressure before drilling and can meet the on-site engineering requirements.

[0162] The method for predicting the formation pressure of the un-drilled section provided by the embodiment of the present invention predicts the formation pressure of the specified depth in the un-drilled section based on the predicted acoustic travel time difference and the acoustic travel time difference on the compaction trend line of the specified depth in the un-drilled section obtained based on the compaction trend line; when predicting the acoustic travel time difference, the predicted reference value is corrected based on the fluctuation value to obtain the final predicted value of the acoustic travel time difference. This method not only considers the existing acoustic travel time difference data in the drilled section but also takes into account the inaccurate factors existing in the prediction, and makes necessary adjustments, so as to obtain an accurate predicted result of the acoustic travel time difference. On this basis, further combining the acoustic travel time difference on the compaction trend line and other relevant factors to predict the formation pressure can obtain a more accurate prediction result. This method predicts the formation pressure of the un-drilled section based on the drilled section and corrects and adjusts the errors in the prediction process to ensure the prediction accuracy of the pre-drilling prediction, which is used to guide the actual drilling operation, has good reference value, and provides more reliable data support for the drilling operation.

[0163] Embodiment III

[0164] The specific implementation process of the method for predicting the formation pressure of the un-drilled section provided by the third embodiment of the present invention is different from that of the second embodiment in that, on the basis of the second embodiment, it further includes verifying the accuracy of the acoustic travel time difference and the prediction result of the formation pressure. This method is realized by a field test device for testing the formation pressure of the un-drilled section. The method of this embodiment further includes the following steps on the basis of the second embodiment:

[0165] Obtain the measured formation pressure of the specified depth in the un-drilled section through the formation pressure testing equipment, and determine the prediction error of the predicted value of the acoustic travel time difference and the prediction error of the predicted value of the formation pressure at the specified depth in the un-drilled section according to the measured acoustic travel time difference and the measured formation pressure obtained by well logging; judge whether the prediction error of the predicted value of the acoustic travel time difference and the prediction error of the predicted value of the formation pressure at the specified depth in the un-drilled section meet the error requirements.

[0166] Among them, the formation pressure testing equipment includes: a syringe, a piston, and a needle head disposed in a hole passage at a specified depth of the formation. The hole passage is sealed from the wellbore by a packer; a surface device and a fluid pressure sensor connected by a cable. The fluid sensor is disposed at the needle head for measuring the formation pressure.

[0167] The implementation process of this embodiment will be specifically described below:

[0168] Step 1: Deploy the formation pressure testing equipment

[0169] As Figure 4 shown, the on-site test device for testing the formation pressure of an undrilled section includes: a surface device 1, a cable 2, a hole passage 3, a packer 4, a syringe 5, a piston 6, a needle head 7, and a fluid pressure sensor 8;

[0170] (1) When drilling reaches the specified depth, stop drilling. The surface device 1 controls the perforating gun to fire perforating charges into the formation through the cable 2 to form a hole passage 3;

[0171] (2) Arrange the packer 4 on the wellbore wall to isolate the drilling fluid from flowing into the hole passage 3 from the wellbore wall by using the packer 4;

[0172] (3) Arrange the syringe 5, the piston 6, the needle head 7, and the fluid pressure sensor 8 in the hole passage 3. The syringe 5 extracts the formation fluid in the hole passage 3 through the piston 6 and the needle head 7; a fluid pressure sensor 8 is arranged on the needle head 7 for monitoring the fluid pressure in the hole passage 3, that is, the formation pressure;

[0173] Step 2: Based on the formation pressure testing equipment, test the formation pressure, including:

[0174] (1) Use the syringe 5 to extract fluid from the hole passage 3. The extraction speed and time can be set. For example, the extraction speed is 1000 ml per minute, and stop extraction after 30 minutes; during the extraction process, as the fluid in the hole passage 3 decreases, the fluid pressure drops, and the formation fluid outside the hole passage 3 will seep into the hole passage 3. Eventually, the fluid pressures inside and outside the hole passage 3 will be in an equilibrium state;

[0175] (2) After starting to extract fluid from the syringe 5, record the data of the fluid pressure sensor 8 in real time (note: still record the data of the fluid pressure sensor 8 after stopping fluid extraction) until the data of the fluid pressure sensor 8 remains stable and no longer changes. At this time, the data of the fluid pressure sensor 8 is the measured value p of the formation pressure at the specified depth.

[0176] In one embodiment, the steps for predicting the formation pressure of the undrilled section (6280 m - 6300 m) based on the well logging data of the drilled section (6000 m - 6280 m) of Well AG2 in the JZ block include:

[0177] (1) Based on the logging data of the drilled section (6000m - 6280m) of Well AG2 in the JZ Block, fit the acoustic time difference Δt' of the drilled section (6000m - 6280m) of AG2 n The first relational expression regarding the depth h: Δt' n = 86044e -0.001h , where the original data of the acoustic time difference of the drilled section of Well AG2 is as Figure 5 shown; according to the first relational expression, substitute the depth H of the undrilled section (6280m - 6300m) to obtain the reference value Δt of the acoustic time difference of the undrilled section of Well AG2 b = 86044e -0.001H ;

[0178] (2) According to the first relational expression, calculate the reference value of the acoustic time difference of the drilled section (6000m - 6280m), find the difference between the reference value of the acoustic time difference and the measured value of the acoustic time difference of the drilled section (6000m - 6280m) to obtain the fluctuation value of the acoustic time difference of the drilled section (6000m - 6280m) of Well AG2, as Figure 6 shown, and then establish a matrix of the fluctuation values of the acoustic time difference per meter of the drilled section (6000m - 6280m) in meters;

[0179] According to the matrix of the fluctuation values of the acoustic time difference per meter of the drilled section (6000m - 6280m), screen out the maximum value of the fluctuation value of the acoustic time difference per meter depth range of the drilled section of Well AG2, as Figure 7a shown; screen out the minimum value of the fluctuation value of the acoustic time difference per meter depth range of the drilled section of Well AG2, as Figure 7b shown;

[0180] Establish the second relational expressions of the maximum and minimum values of the fluctuation value of the acoustic time difference per meter depth range of the drilled section of Well AG2 regarding the depth as

[0181] Based on the second relational expressions, substitute different depths of the undrilled section (6280m - 6300m) to obtain the maximum and minimum values of the fluctuation value of the acoustic time difference per meter depth range of the undrilled section;

[0182] According to the maximum and minimum values of the fluctuation value of the acoustic time difference per meter depth range of the undrilled section (6280m - 6300m), obtain the fluctuation value of the acoustic time difference per meter depth range of the undrilled section (6280m - 6300m), as Figure 8 shown;

[0183] (3) According to the reference value of the acoustic time difference of the undrilled section and the fluctuation value of the acoustic time difference of the undrilled section, sum them to obtain the predicted value of the acoustic time difference of the undrilled section;

[0184] (4) Based on steps (1), (2), and (3), obtain the predicted acoustic travel time values for the un-drilled section (6280m - 6300m) of Well AG2, as Figure 9 shown;

[0185] Based on the relationship between seismic layer velocity and density, and according to the seismic layer velocity data of the un-drilled section of Well AG2, as Figure 10 shown, obtain the density of the un-drilled section of Well AG2, as Figure 11 shown;

[0186] According to the acoustic travel time data of the shale formation (3000m - 3800m) in Well AG2 (as Figure 12 shown), fit the equation of the normal compaction trend line as lnΔt' n = 6.0077 - 0.0002H;

[0187] (5) According to the predicted acoustic travel time values of the un-drilled section (6280m - 6300m) of Well AG2 and the acoustic travel time on the compaction trend line of the shale formation (3000m - 3800m) in Well AG2, use the following Eaton formula to calculate the formation pressure of the un-drilled section (6280m - 6300m):

[0188]

[0189] where: P P is the formation pressure; P0 is the overburden pressure, obtained by integrating the density ρ with respect to depth, ρ is the density, obtained from density logging; P h is the hydrostatic pressure, obtained by integrating the water density along the depth direction; Δt″ n is the acoustic travel time on the normal compaction trend line; Δt n is the predicted acoustic travel time value of the un-drilled section; N is the Eaton exponent;

[0190] The Eaton exponent can be obtained by back-calculating using the formation pressure, overburden pressure, hydrostatic pressure, acoustic travel time on the normal trend line, and measured acoustic travel time at the depth of the measured points in the adjacent well and substituting them into the following formula:

[0191]

[0192] where: P' p is the measured value of the formation pressure in the adjacent well; P'0 is the vertical overburden pressure in the adjacent well; P' h is the hydrostatic pressure; Δt″″ is the measured acoustic travel time in the adjacent well; Δt″′ n is the acoustic travel time on the normal compaction trend line in the adjacent well.

[0193] In this embodiment, the adjacent well AG1 of Well AG2 has measured formation pressure data at a depth of 4200 m. Substituting the formation density ρ = 2.251 g / cm3, acoustic time difference Δt = 283.157 μs / m, and formation pressure Pp = 44.57 MPa at a depth of 4200 m in Well AG1 into the above formula to solve for the Eaton index, the Eaton index of Well AG2 is obtained as 1.3; according to the Eaton formula, the predicted formation pressure values of the un-drilled sections of Well AG2 at 6281 m, 6282 m, 6283 m, ……, 6300 m are 62.89 MPa, 63.27 MPa, 63.69 MPa, 64.09 MPa, 64.72 MPa, 64.96 MPa, 65.64 MPa, 66.41 MPa, 67.04 MPa, 67.23 MPa, 66.70 MPa, 67.35 MPa, 66.33 MPa, 65.92 MPa, 67.07 MPa, 66.81 MPa, 66.89 MPa, 66.97 MPa, 67.05 MPa, 67.16 MPa respectively.

[0194] Using the above on-site test device for testing the formation pressure of the un-drilled section, a field test of the formation pressure of Well AG2 is carried out: according to Step 1, the test device is arranged; according to Step 2, the formation pressure is tested at depths of 6281 m, 6282 m, 6283 m, ……, 6300 m, and the test results are p1 = 65.33 MPa, p2 = 64.45 MPa, p3 = 65.22 MPa, p4 = 65.58 MPa, p5 = 65.71 MPa, p6 = 65.79 MPa, p7 = 65.83 MPa, p8 = 66.35 MPa, p9 = 66.75 MPa, p 10 = 67.43 MPa, p 11 = 67.63 MPa, p 12 = 67.15 MPa, p 13 = 66.84 MPa, p 14 = 66.51 MPa, p 15 = 66.75 MPa, p 16 = 66.23 MPa, p 17 = 67.13 MPa, p 18 = 67.54 MPa, p 19 = 67.11 MPa, p 20 = 66.97 MPa.

[0195] Comparing the acoustic time difference results of Well AG2 obtained by the acoustic time difference prediction method for the un-drilled section and well logging in this embodiment, as Figure 13As shown, the average error is 6.75%; comparing with the formation pressure results of Well AG2 obtained by the on-site test device of the formation pressure prediction method based on the undrilled section pressure and the undrilled section formation pressure in the comparative example, see Figure 14 , the average error is 8.25%; the above comparison results show that the proposed prediction method can meet the on-site engineering requirements.

[0196] For the acoustic time difference prediction method for the undrilled section provided by the present invention, by comparing with the measured value of the acoustic time difference, it can be known that the prediction accuracy of the proposed method exceeds 93%, providing more reliable data for the following prediction of the formation pressure in the undrilled section;

[0197] For the formation pressure prediction method for the undrilled section provided by the present invention, by comparing with the measured value of the on-site formation pressure, it can be known that the prediction accuracy of the proposed method exceeds 91%, ensuring the pre-drilling prediction accuracy of the formation pressure and meeting the on-site engineering requirements;

[0198] Based on the same inventive concept, an embodiment of the present invention further provides an acoustic time difference prediction device for the undrilled section. This device can be set in a computer device with data processing capabilities. The structure of this device is as Figure 15 shown, including: a first prediction module 11, a second prediction module 12, and an acoustic time difference determination module 13.

[0199] The first prediction module 11 is used to predict the reference value of the acoustic time difference at a specified depth in the undrilled section according to the first relationship expression of the acoustic time difference and depth established in advance for the drilled section; the first relationship expression is established according to the scatter data of the acoustic time difference in the drilled section;

[0200] The second prediction module 12 is used to predict the fluctuation value of the acoustic time difference at a specified depth in the undrilled section according to the second relationship expression of the acoustic time difference fluctuation data and depth established for the drilled section; the second relationship expression is established according to the acoustic time difference fluctuation data in the drilled section;

[0201] The acoustic time difference determination module 13 is used to determine the predicted value of the acoustic time difference at a specified depth in the undrilled section according to the reference value and the fluctuation value of the acoustic time difference at the specified depth in the undrilled section.

[0202] In addition, an embodiment of the present invention further provides a formation pressure prediction device for the undrilled section. This device can be set in a computer device with data processing capabilities. The structure of this device is as Figure 16 shown, including: an acoustic time difference prediction device 21 for the undrilled section, an acquisition module 22, and a pressure determination module 23.

[0203] The acoustic time difference prediction device 21 for the undrilled section as described above is used to predict the acoustic time difference at a specified depth in the undrilled section;

[0204] An acquisition module 22, configured to obtain the acoustic time difference on the compaction trend line at a specified depth of an un-drilled section according to a pre-established relationship expression between the acoustic time difference and depth of a drilled section; the relationship expression of the compaction trend line is established based on the acoustic time difference data of the drilled section.

[0205] A pressure determination module 23, configured to determine a predicted formation pressure value at a specified depth of an un-drilled section according to the predicted acoustic time difference value at a specified depth of the un-drilled section and the acoustic time difference on the compaction trend line.

[0206] Regarding the device for predicting the acoustic time difference of an un-drilled section and predicting the pressure of an un-drilled section in the above embodiments, the specific manners in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated herein.

[0207] An embodiment of the present invention further provides a computer storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, the above method for predicting the acoustic time difference of an un-drilled section and / or the above method for predicting the formation pressure of an un-drilled section are implemented.

[0208] An embodiment of the present invention further provides a prediction device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, the above method for predicting the acoustic time difference of an un-drilled section and / or the above method for predicting the formation pressure of an un-drilled section are implemented.

[0209] Unless otherwise specifically stated, terms such as processing, calculating, computing, determining, displaying, etc. may refer to actions and / or processes of one or more processing or computing systems, or similar devices, which operate on and transform data represented as physical (such as electronic) quantities in registers or memories of a processing system into other data similarly represented as physical quantities in memories, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals can be represented using any of a variety of different technologies and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0210] It should be understood that the specific order or hierarchy of steps in the disclosed processes are examples of exemplary methods. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The appended method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy.

[0211] In the foregoing detailed description, various features are combined in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are expressly recited in each claim. On the contrary, as reflected in the appended claims, the invention lies in less than all of the features of a single disclosed embodiment. Accordingly, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0212] Those skilled in the art should also understand that the various illustrative logical blocks, modules, circuits, and algorithmic steps described in connection with the embodiments herein can be implemented as electronic hardware, computer software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in a variety of ways for each particular application, but such implementation decisions should not be interpreted as departing from the scope of the present disclosure.

[0213] The steps of a method or algorithm described in connection with the embodiments herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination thereof. The software module may be located in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may be located in an ASIC. The ASIC may be located in a user terminal. Of course, the processor and the storage medium may also exist as discrete components in a user terminal.

[0214] For a software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described herein. These software codes can be stored in a memory unit and executed by a processor. The memory unit may be implemented within the processor or outside the processor, and in the latter case, it is coupled to the processor in a communication manner by various means, which are well known in the art.

[0215] The foregoing description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but those of ordinary skill in the art should recognize that the various embodiments can be further combined and arranged. Accordingly, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. In addition, with respect to the term "comprising" as used in the specification or claims, that term is inclusive in a manner similar to the term "including", as that term is interpreted when used as a transitional word in a claim. Further, any use of the term "or" in a claim or the specification is to mean "non-exclusive or".

Claims

1. A method for predicting the acoustic travel time of an undrilled section, characterized in that, Including: Predicting a reference value of the acoustic transit time at a specified depth of an undrilled section according to a first relational expression of the acoustic transit time and depth of a drilled section established in advance; The first relational expression is established according to the acoustic transit time scatter data of the drilled section; Predicting a fluctuation value of the acoustic transit time at a specified depth of an undrilled section according to a second relational expression of the acoustic transit time fluctuation data and depth of the drilled section established; The second relational expression is established according to the acoustic transit time fluctuation data of the drilled section; Determining a predicted value of the acoustic transit time at a specified depth of an undrilled section according to the reference value and the fluctuation value of the acoustic transit time at the specified depth of the undrilled section.

2. The method according to claim 1, characterized in that, The predicting a reference value of the acoustic transit time at a specified depth of an undrilled section according to a first relational expression of the acoustic transit time and depth of a drilled section established in advance includes: Fitting the acoustic transit time scatter data of the drilled section according to the following formula to obtain a first relational expression of the acoustic transit time and depth of the drilled section: Δt' n = ae bh where: Δt' n is the acoustic travel time difference of the drilled section; h is the depth; a and b are coefficients; Predicting a reference value of the acoustic transit time at a specified depth of an undrilled section based on the first relational expression and the specified depth of the undrilled section.

3. The method according to claim 1, characterized in that Establishing a second relational expression of the acoustic transit time fluctuation data and depth of the drilled section includes: Determining the reference value of the acoustic transit time at different depths of the drilled section according to the first relational expression, and determining the fluctuation value of the acoustic transit time at different depths according to the reference value of the acoustic transit time at different depths of the drilled section and the measured value of the acoustic transit time at the corresponding depth; Determining the extreme values of the acoustic transit time fluctuation within different depth windows according to the fluctuation values of the acoustic transit time at different depths; Establishing a second relational expression of the fluctuation value of the acoustic transit time and depth according to the extreme values of the acoustic transit time fluctuation within different depth windows.

4. The method according to claim 3, wherein The determining the extreme values of the acoustic transit time fluctuation within different depth windows according to the fluctuation values of the acoustic transit time at different depths, and establishing a second relational expression of the fluctuation value of the acoustic transit time and depth according to the extreme values of the acoustic transit time fluctuation within different depth windows includes: Determining the maximum fluctuation value and the minimum fluctuation value of the acoustic transit time within different depth windows according to the fluctuation values of the acoustic transit time at different depths; Establishing a maximum fluctuation relational expression of the maximum fluctuation value of the acoustic transit time and depth and a minimum fluctuation relational expression of the minimum fluctuation value of the acoustic transit time and depth according to the maximum fluctuation value and the minimum fluctuation value of the acoustic transit time within different depth windows.

5. The method according to claim 4, wherein The predicting a fluctuation value of the acoustic transit time at a specified depth of an undrilled section according to a second relational expression of the acoustic transit time fluctuation data and depth of the drilled section established includes: Obtaining the maximum value and the minimum value of the acoustic transit time fluctuation within different depth windows of the undrilled section according to the maximum fluctuation relational expression of the maximum fluctuation value of the acoustic transit time and depth and the minimum fluctuation relational expression of the minimum fluctuation value of the acoustic transit time and depth; Determining the fluctuation value of the acoustic transit time within different depth windows of the undrilled section according to the maximum value and the minimum value of the acoustic transit time fluctuation within different depth windows of the undrilled section.

6. The method according to claim 5, wherein The determining the fluctuation value of the acoustic transit time within different depth windows of the undrilled section according to the maximum value and the minimum value of the acoustic transit time fluctuation within different depth windows of the undrilled section includes: According to the maximum value of the fluctuation value of the acoustic travel time within the specified depth window of the un-drilled section Minimum value The fluctuation value Δt of the acoustic travel time of the un-drilled section is obtained by using the following formula f ; Where: L is the number of acoustic transit time scatter points within a depth window range, and R is a random number between 1 and L.

7. A method for predicting formation pressure in an undrilled section, characterized in that, Including: Use the acoustic time difference prediction method for the undrilled section as described in any one of claims 1-6 to predict the acoustic time difference at a specified depth in the undrilled section; According to the pre-established relationship expression of the compaction trend line between the acoustic time difference and depth in the drilled section, obtain the acoustic time difference on the compaction trend line at the specified depth in the undrilled section; the compaction trend line relationship expression is established based on the acoustic time difference data in the drilled section; Determine the predicted formation pressure value at the specified depth in the undrilled section according to the predicted acoustic time difference value at the specified depth in the undrilled section and the acoustic time difference on the compaction trend line.

8. The method according to claim 7, wherein The obtaining the acoustic time difference on the compaction trend line at the specified depth in the undrilled section according to the pre-established relationship expression of the compaction trend line between the acoustic time difference and depth in the drilled section includes: According to the acoustic time difference scatter data in the drilled section, fit the compaction trend line according to the following formula: lnΔt' n = lnΔt0 - Ch where Δt' n is the acoustic travel time at depth h of the drilled section; Δt0 is the acoustic travel time at zero depth; C is the compaction coefficient; h is the depth; Determine the acoustic time difference on the compaction trend line at the specified depth in the undrilled section according to the compaction trend line and the depth of the undrilled section.

9. The method according to claim 7, wherein The determining the predicted acoustic formation pressure value in the undrilled section according to the predicted acoustic time difference value at the specified depth in the undrilled section and the acoustic time difference on the compaction trend line includes: Determine the predicted acoustic formation pressure value in the undrilled section according to the predicted acoustic time difference value at the specified depth in the undrilled section, the acoustic time difference on the compaction trend line, the overburden pressure and the hydrostatic pressure at the specified depth in the undrilled section.

10. The method according to claim 9, wherein The determining the predicted acoustic formation pressure value in the undrilled section according to the predicted acoustic time difference value at the specified depth in the undrilled section, the acoustic time difference on the compaction trend line, the overburden pressure and the hydrostatic pressure at the specified depth in the undrilled section includes: Determine the formation density at the specified depth in the undrilled section according to the seismic layer velocity at the specified depth in the undrilled section and the relationship expression between the seismic layer velocity and the formation density; Determine the overburden pressure at the specified depth in the undrilled section according to the formation density at the specified depth in the undrilled section; Use the following formula to determine the predicted acoustic formation pressure value in the undrilled section: Where: P P is the predicted formation pressure value; P0 is the overlying formation pressure; P h is the hydrostatic pressure; Δt” n is the acoustic travel time difference on the compaction trend line; Δt n is the predicted acoustic travel time difference value of the un-drilled section; N is the Eaton index.

11. The method according to claim 10, wherein The Eaton index is determined according to the measured formation pressure, overburden pressure, hydrostatic pressure, acoustic time difference on the compaction trend line and the measured acoustic time difference at different depths in the adjacent well.

12. The method according to claim 11, wherein It further includes: Obtain the measured formation pressure at the specified depth in the undrilled section through a formation pressure testing device, and determine the prediction error of the predicted acoustic time difference value and the prediction error of the predicted formation pressure value at the specified depth in the undrilled section according to the measured acoustic time difference obtained by logging and the measured formation pressure; Judge whether the prediction error of the predicted acoustic time difference value and the prediction error of the predicted formation pressure value at the specified depth in the undrilled section meet the error requirements.

13. The method according to claim 12, wherein The formation pressure testing device includes: A syringe, a piston and a needle head arranged in the hole channel at the specified depth of the formation, and the hole channel is sealed with the wellbore through a packer; A surface device and a fluid pressure sensor connected by a cable, and the fluid sensor is arranged at the needle head for measuring the formation pressure.

14. An acoustic travel time prediction device for an undrilled section, characterized in that, It includes: A first prediction module for predicting the reference value of the acoustic time difference at the specified depth in the undrilled section according to the pre-established first relationship expression between the acoustic time difference and depth in the drilled section; The first relationship expression is established based on the acoustic time difference scatter data in the drilled section; A second prediction module, configured to predict the acoustic time difference fluctuation value at a specified depth of an undrilled section according to a second relationship expression established between the acoustic time difference fluctuation data and the depth of the drilled section; The second relationship expression is established according to the acoustic time difference fluctuation data of the drilled section; An acoustic time difference determination module, configured to determine the predicted acoustic time difference value at a specified depth of the undrilled section according to the reference value and the fluctuation value of the acoustic time difference at the specified depth of the undrilled section.

15. A formation pressure prediction device for an undrilled section, characterized in that, Comprising: The undrilled section acoustic time difference prediction device according to claim 14, configured to predict the acoustic time difference at a specified depth of the undrilled section; An acquisition module, configured to acquire the acoustic time difference on the compaction trend line at a specified depth of the undrilled section according to a compaction trend line relationship expression established in advance between the acoustic time difference and the depth of the drilled section; the compaction trend line relationship expression is established according to the acoustic time difference data of the drilled section; A pressure determination module, configured to determine the predicted formation pressure value at a specified depth of the undrilled section according to the predicted acoustic time difference value at the specified depth of the undrilled section and the acoustic time difference on the compaction trend line.

16. A computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, the undrilled section acoustic time difference prediction method according to any one of claims 1-6 and / or the undrilled section formation pressure prediction method according to any one of claims 7-13 are implemented.

17. A prediction device, characterized in that, Comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, the undrilled section acoustic time difference prediction method according to any one of claims 1-6 and / or the undrilled section formation pressure prediction method according to any one of claims 7-13 are implemented.

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