Determination method of talc mineral logging skeleton parameters and effective porosity of formation

Abstract

The invention discloses a method for determining well logging skeleton parameters of talc minerals and effective porosity of formations, which is characterized by comprising: obtaining the contents of various minerals in core samples at different depths of a coring well and the well logging curve of the coring well; establishing a calculation formula between the contents of various minerals at corresponding depths and the well logging values ​​on the well logging curve; solving the calculation formula according to the well logging skeleton parameters of known minerals to obtain the well logging skeleton parameters of the talc minerals; and solving the problem that the well logging skeleton parameters of the talc minerals are currently unknown and cannot be determined by a pure rock measurement method.

Description

Technical Field

[0001] The present invention relates to the field of well logging parameter interpretation involving complex lithology reservoirs, and in particular to a complex lithology well logging interpretation method under the condition of special minerals with unknown well logging responses. Background Art

[0002] The carbonate reservoirs in a certain area are greatly affected by sedimentation, structure and diagenesis, with strong heterogeneity and complex lithology. They contain not only a variety of conventional minerals such as mud, dolomite, calcite, quartz, but also special minerals such as talc [Mg3(SiO 10 )(OH)2], which leads to complex reservoir logging response characteristics.

[0003] The key to calculating the reservoir mineral content and effective porosity lies in the determination of the volume model and the correct selection of the mineral skeleton parameter values. If the influence of talc is not considered, the silicon and magnesium elements contained in talc in the element logging interpretation will overlap with the magnesium and silicon elements in other conventional minerals, causing errors in the closed model, resulting in large errors between the calculated reservoir mineral content and effective porosity and the core analysis results. Therefore, the determination of the talc mineral logging skeleton parameters is crucial.

[0004] At present, for conventional minerals such as quartz, the logging skeleton parameters are mainly determined by measuring pure rocks. However, talc, a special mineral, belongs to a special clay mineral. First, there is no pure rock with the same composition as that underground. Second, the degree to which this special clay mineral is affected by bound water under underground conditions is unknown. The method of using pure rock measurements to determine the logging skeleton parameters of talc minerals is not applicable. Summary of the invention

[0005] In view of this, the present invention provides a method for determining talc mineral logging skeleton parameters, which solves the problem that the current talc mineral logging skeleton parameters are unknown and cannot be determined by pure rock measurement methods.

[0006] In addition, the present invention also provides a method for determining the content of each mineral in the formation and a method for determining the effective porosity of the formation, which solves the problem that the calculated reservoir mineral content and effective porosity have large errors compared with the core analysis results because the influence of talc is not taken into account.

[0007] In a first aspect, the method for determining the talc mineral logging skeleton parameters is characterized by comprising:

[0008] Obtaining the mineral contents of core samples at different depths of the coring well and the logging curve of the coring well;

[0009] Establishing a calculation formula between the content of each mineral at a corresponding depth and the logging value on the logging curve;

[0010] The calculation formula is solved according to the well logging skeleton parameters of the known minerals to obtain the well logging skeleton parameters of the talc mineral.

[0011] Further, the logging skeleton parameters include element skeleton parameters and three-porosity skeleton parameters;

[0012] The logging curves include dry weight curves of various elements and three porosity logging curves;

[0013] The logging values ​​on the dry weight curves of the elements are the dry weight values ​​of the elements;

[0014] The logging value on the three-porosity logging curve is a three-porosity logging curve value.

[0015] Furthermore, the method for determining the elemental skeleton parameters of the talc mineral is:

[0016] Establishing a calculation formula between the content of each mineral at a corresponding depth and the dry weight value of each element on the dry weight curve of each element;

[0017] The calculation formula is solved according to the element skeleton parameters of the known minerals to obtain the element skeleton parameters of the talc mineral.

[0018] Furthermore, the method for determining the three porosity framework parameters of the talc mineral is:

[0019] Establishing a calculation formula between the content of each mineral at a corresponding depth and the three-porosity logging curve value on the three-porosity logging curve;

[0020] The calculation formula is solved according to the three-porosity framework parameters of the known minerals to obtain the three-porosity framework parameters of the talc mineral.

[0021] Furthermore, the calculation formula between the content of each mineral and the dry weight value of each element is:

[0022]

[0023] Among them: A ij The conversion coefficient of the i-th element in the j-th mineral except talc; X j is the content of the jth mineral except talc; B i is the dry weight content of the i-th element; X h is the talc content; n is the number of minerals; m is the number of elements; p is the number of samples.

[0024] Further, the three-porosity framework parameters include lithology density, compensated neutron and sonic time difference;

[0025] The three-porosity logging curves include a lithology density logging curve, a compensated neutron logging curve and an acoustic time difference logging curve.

[0026] Furthermore, the calculation formula of the mineral content and the three-porosity logging curve value is:

[0027]

[0028] Where: i represents lithology density, compensated neutron, and acoustic time difference; B is the three-porosity logging value (lithology density, compensated neutron, and acoustic time difference); A f is the fluid skeleton value in the pore; A ij represents the skeleton value of the jth mineral in the formation in the i-th porosity logging method, X j is the content of the jth mineral except talc; X h is the talc content; Ф is the effective porosity of the core; n is the number of minerals; p is the number of samples.

[0029] Furthermore, the method for obtaining the mineral contents of the core samples at different depths is:

[0030] Performing depth homing on the core of the coring well to select core samples at different depths;

[0031] Conducting core analysis on the core samples at different depths to obtain core analysis data of the formation where the coring well is located;

[0032] The core analysis data is used to obtain the mineral contents of core samples at different depths in the coring well.

[0033] In a second aspect, a method for determining the content of each mineral in a stratum is characterized by comprising:

[0034] The method for determining the talc mineral well logging skeleton parameters described in the first aspect is used to determine the element skeleton parameters of the talc mineral.

[0035] In a third aspect, a method for determining effective porosity of a formation is characterized by comprising:

[0036] The method for determining the content of each mineral in the stratum described in the second aspect; and

[0037] The method for determining the well logging skeleton parameters of talc mineral described in the first aspect is used to determine the three-porosity skeleton parameters of the talc mineral.

[0038] The present invention has the following beneficial effects:

[0039] The method of the present invention combines core data with logging data, establishes a connection between the content of each mineral in the formation and each element dry weight curve and three-porosity logging curve, and uses the logging skeleton parameters of known minerals to determine the element skeleton parameters of talc minerals and the lithology density, compensated neutron and acoustic wave time difference skeleton parameter values ​​based on the least squares principle, thereby solving the problem that the current talc mineral logging skeleton parameters are unknown and cannot be determined by a pure rock measurement method; further, the talc mineral logging skeleton parameters are applied to the interpretation of the formation mineral content and effective porosity, thereby improving the interpretation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0041] Figure 1 It is a work flow chart of the method for determining the talc mineral well logging skeleton parameters of the present invention;

[0042] Figure 2 It is a comparison chart of the mineral contents, effective porosity and core analysis results obtained by optimization processing before and after determining the talc mineral skeleton parameters in an embodiment of the present invention.

[0043] Figure 2 It can be seen that after determining the talc mineral skeleton parameter value, the mineral contents of the formation obtained by element logging are obviously different, and the accuracy of the calculated effective porosity of the formation is significantly improved, which is consistent with the core analysis results. DETAILED DESCRIPTION

[0044] The present invention is described below based on embodiment, but it is worth noting that the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. However, for the part not described in detail, those skilled in the art can also fully understand the present invention.

[0045] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0046] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning of "including but not limited to".

[0047] Figure 1 is a work flow chart of the method for determining the talc mineral logging skeleton parameters of the present invention; Figure 1 In the method for determining the same, the method comprises:

[0048] Step S101: Obtain the content of each mineral in core samples at different depths of a coring well and the logging curve of the coring well; Step S102: Establish a calculation formula between the content of each mineral and the logging value at the corresponding depth of the logging curve; Step S103: Solve the calculation formula according to the logging skeleton parameters of known minerals to obtain the logging skeleton parameters of talc minerals.

[0049] It should be noted that the logging skeleton parameters of talc mineral disclosed in the present invention include elemental skeleton parameters and three-porosity logging skeleton parameters of talc mineral; and the three-porosity logging skeleton parameters include lithology density logging skeleton parameters, compensated neutron logging skeleton parameters and sonic time difference logging skeleton parameters.

[0050] Step S101: Obtain the mineral contents of core samples at different depths of the coring well and the logging curve of the coring well:

[0051] 1. The method for obtaining the mineral content of core samples at different depths of the coring well is:

[0052] The cores of the coring wells in the study area are depth-relocated with reference to the logging data, so that a number of core samples at different depths can be selected from the cores of the coring wells; core constant element analysis, whole-rock mineral content analysis, and physical property analysis are carried out on these core samples to obtain core analysis data of the stratum where the coring wells are located, and the core analysis data are used to obtain the mineral types, mineral contents, and elemental compositions of the core samples at different depths of the coring wells.

[0053] 2. The method for obtaining the well logging curve of the coring well is:

[0054] The logging curves include dry weight curves of various elements and three-porosity logging curves.

[0055] The element logging data and conventional logging curve data of the core wells in the study area were collected and sorted. The element logging data were calibrated with reference to the depth of the conventional logging curve data to obtain depth-matched logging data. Then, the element logging data of the core wells were processed using the element logging processing module of Schlumberger Techlog software to obtain the dry weight curves of each element.

[0056] Taking into account the element composition, drilling mud type and other factors, the processing parameters and results of element logging data were calibrated using the core constant element analysis results of the coring well, and the dry weight curves of silicon, calcium, magnesium, aluminum and other elements of the coring well were obtained.

[0057] The three-porosity logging curves, including the lithology density logging curve, the compensated neutron logging curve and the sonic time difference logging curve, can be obtained from the conventional logging curve data of the coring wells in the study area.

[0058] Step S102: establishing a calculation formula between the content of each mineral and the logging value at the corresponding depth of the logging curve; and Step S103: solving the calculation formula according to the logging skeleton parameters of known minerals to obtain the logging skeleton parameters of talc minerals.

[0059] 1. The method of establishing the calculation formula between the content of each mineral and the dry weight value of each element at the corresponding depth of the dry weight curve of each element and solving the calculation formula according to the element skeleton parameters of the known mineral to obtain the element skeleton parameters of the talc mineral is:

[0060] 1. Use the core whole-rock mineral content analysis data to determine the types of minerals contained in the stratum;

[0061] 2. Because the dry weight content of a certain element in the stratum is equal to the sum of the product of the mineral content containing the element and the mineral conversion coefficient, the mineral conversion coefficient here is the element skeleton parameter. Therefore, the element skeleton parameter of talc mineral can be calculated by using the conversion coefficients of other known minerals and the contents of each mineral and the dry weight curve values ​​of each element.

[0062] Specifically, the dry weight curve values ​​of each element at the corresponding depth of the core samples at different depths are checked on the dry weight curve of each element, and a calculation matrix between the mineral content, mineral conversion coefficient and the dry weight curve value of each element of each core sample is established, and converted into a linear equation group for calculating the content of each element in the formation; the specific establishment method is:

[0063] Assume that there are n kinds of minerals in the stratigraphic framework, and each mineral is composed of m kinds of elements. Since the sum of the content of a certain element in each mineral in the stratigraphic formation should be equal to the dry weight content of the element in the element logging data, the calculation of the content of a certain element in the stratigraphic formation can be expressed in matrix form:

[0064] C m×n ·M n×1 =E m×1

[0065] In the formula, C m×n 、M n×1 and E m×1 They are the formation mineral conversion coefficient matrix, mineral content matrix and formation element content matrix respectively;

[0066] The element logging responses are all linearized response equations, which can eventually be converted into a set of equations for calculating the element content. The general expression for calculating the element content can be written as:

[0067]

[0068] Where: A ij is the conversion coefficient of the ith element in the jth mineral; X j is the content of the jth mineral; Bi is the dry weight content of the ith element, n is the number of minerals, and m is the number of elements.

[0069] For example, the calculation expression for silicon content can be written as:

[0070]

[0071] Among them: SI j X is the conversion coefficient of silicon in the jth mineral except talc; j is the content of the jth mineral except talc; SI c is the dry weight content of silicon; X h is the talc mineral content; SI h is the silicon conversion coefficient of talc mineral.

[0072] 3. Based on the principle of least squares method, the error between the dry weight value of each element calculated theoretically for each core and the dry weight curve value of each element obtained by element logging at the corresponding depth is minimized, and the mineral conversion coefficient calculation formula of each element of talc mineral is obtained as follows:

[0073]

[0074] Among them: A ij The conversion coefficient of each element in the jth mineral except talc; X j is the content of the jth mineral except talc; B i is the dry weight content of the i-th element, obtained from formation element logging; X h is the talc mineral content; n is the number of minerals; m is the number of elements; p is the number of samples.

[0075] Because the mineral content of each sample and the dry weight curve value of each element at the corresponding depth are known, the mineral conversion coefficients of the minerals except talc can be found in the Schlumberger Mineral Handbook. The linear least squares principle is used to solve the linear equations so that the error between the calculated content of each element and the dry weight curve value of each element at the corresponding depth is minimized. The mineral conversion coefficient of each element in talc can be obtained by forward modeling. The mineral conversion coefficient of each element in talc is the element skeleton parameter of talc.

[0076] For example, the mineral conversion coefficient of silicon in talc can be calculated using the following equation:

[0077]

[0078] Among them: SI j X is the conversion coefficient of silicon in the jth mineral except talc; j is the content of the jth mineral except talc; SIc is the content of silicon; X h is the talc mineral content; n is the number of minerals; p is the number of samples.

[0079] Similarly, the mineral conversion coefficients of other elements in talc can be obtained, that is, to determine the element skeleton parameters of talc minerals.

[0080] 2. Establish the calculation formula between the content of each mineral and the three-porosity logging curve value at the corresponding depth on the three-porosity logging curve, and solve the calculation formula according to the three-porosity logging skeleton parameters of the known minerals to obtain the three-porosity logging skeleton parameters of the talc mineral:

[0081] 1. Use the whole rock mineral content analysis and physical property analysis data to find out the effective porosity of each core sample;

[0082] 2. Because the content of each mineral in each sample and the three-porosity curve value at the corresponding depth are known, the three-porosity framework parameters of the minerals other than talc can be found in the Schlumberger Mineral Manual, and the three-porosity framework parameters of the filling fluid in the effective porosity of the core are known. Apply the principle of least squares method to solve the linear equations, so that the error between the calculated three-porosity value of each core and the three-porosity curve value at the corresponding depth is minimized, and the three-porosity logging of talc minerals can be obtained by forward modeling. The calculation formula is solved by the principle of linear least squares method, and the three-porosity logging framework parameters of talc minerals are obtained by forward modeling.

[0083] Specifically, the three-porosity logging curve values ​​(lithology density, compensated neutron, and sonic time difference) at the corresponding depth of each core sample are checked on the three-porosity logging curves (lithology density logging curve, compensated neutron logging curve, and sonic time difference logging curve), and the method of establishing the response equations of the mineral content in each core sample, the effective porosity of the core, the three-porosity skeleton parameters of each mineral, and the three-porosity logging curve values ​​is:

[0084] Assume A ij represents the skeleton value of the jth mineral in the formation in the i-th logging method, n represents the number of formation minerals, X j Represents the content of the jth mineral.

[0085] The general expression of the response equation is:

[0086]

[0087] Where: i represents lithology density, compensated neutron, and acoustic time difference; B is the value of the three-porosity logging curve; A f is the pore fluid skeleton value; Ф is the effective porosity of the core.

[0088] 3. Based on the principle of least squares method, the error between the theoretically calculated three-porosity logging value of each core and the three-porosity curve value actually measured at the corresponding depth is minimized, and the calculation formula of the three-porosity logging skeleton parameters of talc mineral is obtained:

[0089]

[0090] Where: i represents lithology density, compensated neutron, and acoustic time difference; B is the three-porosity logging value (lithology density, compensated neutron, and acoustic time difference); A f is the fluid skeleton value in the pore; A ij represents the skeleton value of the jth mineral in the formation in the i-th porosity logging method, X j is the content of the jth mineral except talc; X h is the talc content; Ф is the effective porosity of the core; n is the number of minerals; p is the number of samples.

[0091] For example, the lithology density skeleton parameter value of talc mineral can be obtained by the following equation:

[0092]

[0093] Where: maj is the density skeleton value of the jth mineral except talc; X j is the content of the jth mineral except talc; ρ b is the logging value of formation lithology density; X h is the talc mineral content; ρ f is the density of formation fluid; Ф is the effective porosity of the core; n is the number of minerals; p is the number of samples.

[0094] Similarly, the logging skeleton parameter values ​​of talc mineral compensation for neutron and acoustic wave time differences can be obtained.

[0095] The purpose of determining the logging skeleton parameters of talc minerals in the present disclosure is that the existence of talc minerals, which is a mineral with unknown logging response parameters, causes the low interpretation accuracy of the content of each mineral in the formation and the effective porosity. Therefore, the present disclosure continues to further explain the method for determining the content of each mineral in the formation and the effective porosity:

[0096] 1. The method for determining the content of each mineral in the stratum is:

[0097] Techlog software ELAN module was used. The volume sum of all mineral contents in the formation was set to 1. The non-negative value of each mineral content was used as a constraint condition. The element skeleton parameters of each mineral in the formation (including talc) and the dry weight curve of each element were taken as known. The response equation of each mineral content under the multi-mineral model was established. The optimization algorithm based on the least squares principle was used to solve the response equation to minimize the error between the theoretical logging value and the actual element dry weight curve value. Finally, the inversion was performed to obtain the content of each mineral in the formation, such as talc, quartz, dolomite, calcite, etc. ( Figure 2 ).

[0098] The response equation for each mineral content is:

[0099]

[0100] Where: m is the number of formation elements; n is the number of minerals that make up the formation; B is the element response value of the formation in the element logging data; A ij is the conversion coefficient of the ith element in the jth mineral; X j is the content of the jth mineral; B i is the content of the ith element.

[0101] It should be noted that in the method for determining the content of each mineral in the formation disclosed in the present invention, the establishment of the response equations of the content of each mineral under the multi-mineral model, the solution of the response equations and the final inversion method are the same as the existing method, so this disclosure will not go into details.

[0102] 2. The method for determining the effective porosity of the formation is:

[0103] Techlog software ELAN module is used to establish the three-porosity response equation under the multi-mineral model by using the obtained mineral content in the formation and the three-porosity skeleton parameters (lithology density, compensated neutron, and acoustic time difference logging skeleton parameters) of each mineral (including talc) as input. The optimization algorithm is used to invert and solve the effective porosity of the formation. Figure 2 The calculation results of effective porosity of formations before and after determining the talc skeleton parameters are given. It can be seen that after considering the influence of talc, the accuracy of effective porosity of formations is significantly improved compared with the porosity of core analysis.

[0104] It should be noted that the method for determining the effective porosity of the formation disclosed in the present invention, the method for establishing the three-porosity response equations under the multi-mineral volume model and the method for inverting the effective porosity of the formation are the same as the existing methods, so the present invention will not repeat them.

[0105] Because the method for determining the effective porosity of a formation disclosed in the present invention incorporates the three-porosity framework parameters of talc minerals, the accuracy of interpreting the effective porosity parameters of the formation is improved.

[0106] The above-mentioned embodiments are only embodiments of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, without departing from the concept of the present invention, several variations, equivalent substitutions, improvements, etc. may be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for determining talc mineral logging skeleton parameters, characterized in that: include: Obtaining the mineral contents of core samples at different depths of the coring well and the logging curve of the coring well; The logging skeleton parameters include element skeleton parameters and three-porosity skeleton parameters; The logging curves include dry weight curves of various elements and three porosity logging curves; The method for determining the element skeleton parameters is: A calculation formula is established between the content of each mineral at a corresponding depth and the dry weight value of each element on the dry weight curve of each element. The calculation formula is: Among them: A ij represents the conversion coefficient of the i-th element in the j-th mineral except talc; X j is the content of the jth mineral except talc; B i is the dry weight content of the i-th element; X h is the talc content; n is the number of minerals; m is the number of elements; p is the number of samples; Solving the calculation formula according to the element skeleton parameters of the known minerals to obtain the element skeleton parameters of the talc mineral; The method for determining the three porosity framework parameters is: A calculation formula is established between the content of each mineral at a corresponding depth and the three-porosity logging curve value on the three-porosity logging curve. The calculation formula is: Among them: B i is the three-porosity logging value, i represents lithology density, compensated neutron and sonic time difference respectively; A f is the fluid skeleton value in the pore; A ij represents the skeleton value of the jth mineral in the formation in the i-th porosity logging method, X j is the content of the jth mineral except talc; X h is the talc content; Ф is the effective porosity of the core; n is the number of minerals; p is the number of samples; The calculation formula is solved according to the three-porosity framework parameters of the known minerals to obtain the three-porosity framework parameters of the talc mineral.

2. The method for determining talc mineral logging skeleton parameters according to claim 1, characterized in that: The three-porosity framework parameters include lithology density, compensated neutron and sonic time difference; The three-porosity logging curves include a lithology density logging curve, a compensated neutron logging curve and an acoustic time difference logging curve.

3. The method for determining talc mineral logging skeleton parameters according to claim 1 or 2, characterized in that: The method for obtaining the mineral contents of the core samples at different depths is: Performing depth homing on the core of the coring well to select core samples at different depths; Conducting core analysis on the core samples at different depths to obtain core analysis data of the formation where the coring well is located; The core analysis data is used to obtain the mineral contents of core samples at different depths in the coring well.

4. A method for determining the content of each mineral in a stratum, characterized in that: include: The method for determining the talc mineral well logging skeleton parameters according to any one of claims 1 to 3 is used to determine the element skeleton parameters of the talc mineral.

5. A method for determining effective porosity of a formation, characterized in that: include: The method for determining the content of each mineral in a stratum as claimed in claim 4; and The method for determining the well logging skeleton parameters of talc minerals according to any one of claims 1 to 3 is used to determine the three-porosity skeleton parameters of talc minerals.

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