CN115680641A - Method for determining porosity lower limit of fractured porous carbonate reservoir - Google Patents
Method for determining porosity lower limit of fractured porous carbonate reservoir Download PDFInfo
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Abstract
The application provides a method for determining the lower limit of the porosity of a fractured-porosity carbonate reservoir, which is characterized in that two types of porosities (fracture porosity and matrix porosity) in carbonate are used for describing respective regression modes respectively to obtain respective calculation formulas; and the porosity of two types of oil testing layers is calculated by utilizing oil testing data and well logging curves which are widely possessed by the oil field; compiling through a scatter diagram, and providing a strong-operability reservoir stratum and dry layer boundary dividing method; and meanwhile, the lower limits of the two types of porosities are determined, and a basis is provided for the evaluation of the fracture pore type carbonate reservoir.
Description
Technical Field
The invention belongs to the technical field of carbonate rock oil and gas reservoir evaluation, and particularly relates to a method for determining the lower limit of the porosity of a fractured porous carbonate rock reservoir.
Background
The fracture pore type carbonate rock refers to carbonate rock which develops fractures and matrix pores, wherein the ratio of fracture volume and matrix pore volume to the total volume of the rock is respectively called fracture porosity and matrix porosity. In fractured pore carbonate rock, the fractures are not only storage spaces, but also channeling media for communicating the pores. The cracks and the porosity in the carbonate rocks have important significance for oil and gas storage.
Experiments show that the porosity of the carbonate oil and gas reservoir matrix is generally between 3 and 12 percent and the porosity of the cracks is generally between 0.005 and 0.5 percent through oil testing. Although the fracture porosity value is low, because of the dual role of the fracture in the oil and gas reservoir, the slight change of the fracture has great change on the storage capacity of the fracture pore type carbonate rock.
The patent CN104806232B provides a method for obtaining a porosity lower limit of a carbonate reservoir, which obtains parameters such as porosity, throat radius, water saturation and the like by utilizing experimental analysis, then establishes correlation relations among the porosity, the throat radius and the water saturation respectively, and conjectures the porosity lower limit of an oil-gas reservoir according to a phase permeability principle. This method essentially only achieves the lower limit of "total porosity" (sum of the porosity of the matrix and the porosity of the fracture), while the respective lower limits of porosity of the matrix and porosity of the fracture have not been achieved; and because the fracture porosity is orders of magnitude lower (compared to the matrix porosity), the lower limit of the general "total porosity" does not reflect the lower limit of the fracture porosity.
Disclosure of Invention
In view of the above, the present invention provides a method of determining a lower limit for porosity of a fractured porous carbonate reservoir that overcomes or at least partially addresses the above problems.
In order to solve the technical problem, the invention provides a method for determining the lower limit of the porosity of a fractured porous carbonate reservoir, which is characterized by comprising the following steps of:
dividing a test oil layer in a target area into a reservoir layer and a dry layer;
acquiring basic data of the target area;
calculating a fracture porosity value and a matrix porosity value of the formation testing interval;
drawing a scatter plot of the fracture porosity values and the matrix porosity values;
distinguishing data of the reservoir and the dry layer in the scatter diagram;
and determining a fracture porosity lower limit value and a matrix porosity lower limit value according to the data of the reservoir stratum and the dry stratum.
Preferably, the calculating the fracture porosity value and the matrix porosity value of the formation interval further comprises:
calculating fracture porosity of the fracture in the target region according to the basic data;
acquiring a fracture porosity logging calculation formula according to the basic data and the fracture porosity;
calculating the matrix porosity of the core in the target area according to the basic data;
and acquiring a matrix porosity logging calculation formula according to the basic data and the matrix porosity.
Preferably, the acquiring the basic data of the target area comprises the steps of:
acquiring core data of the target area;
acquiring logging curve data of the target area;
and acquiring the oil testing data of the target area.
Preferably, said calculating the fracture porosity of the fracture in the target region from the base data comprises the steps of:
acquiring core data of the target area;
identifying a carbonate rock core in the target area according to the core data;
selecting a core segment having fracture development in the carbonate core;
measuring the fracture density, fracture length and fracture width of the fracture;
calculating the average crack length of the crack according to the crack length;
calculating the average crack width of the crack according to the crack width;
calculating a product of the fracture density, the average length of the fracture, and the average width of the fracture;
and taking the product value as the fracture porosity.
Preferably, the acquiring a fracture porosity logging calculation formula according to the basic data and the fracture porosity comprises the following steps:
acquiring a density curve of the cracks in the target area;
acquiring a sonic time difference logging curve of the fracture;
acquiring a natural gamma curve of the crack;
acquiring a caliper log of the fracture;
acquiring the crack porosity of the crack;
performing multiple regression on the density curve, the sonic time difference log curve, the natural gamma curve, the caliper log curve and the fracture pore space;
and taking the multiple regression result as the well logging calculation formula of the fracture porosity.
Preferably, the calculating the porosity of the matrix of the core in the target area according to the basic data comprises the following steps:
acquiring core data of the target area;
identifying a carbonate rock core in the target area according to the core data;
selecting a core section with a crack that does not develop in the carbonate core;
obtaining a plunger sample from the core section;
performing core porosity test on the plunger sample;
and obtaining the matrix porosity of the core according to the test result.
Preferably, the obtaining a matrix porosity logging calculation formula according to the base data and the matrix porosity comprises the following steps:
acquiring acoustic time difference logging curve data of the rock core in the target area;
obtaining the matrix porosity of the core;
performing exponential regression on the sonic moveout log data and the matrix porosity;
and taking the index regression result as the matrix porosity logging calculation formula.
Preferably, said plotting said fracture porosity values and said matrix porosity values comprises the steps of:
establishing a rectangular coordinate system by taking the porosity of the crack as a vertical coordinate and the porosity of the matrix as a horizontal coordinate;
obtaining all of the fracture porosity values and the matrix porosity values;
correspondingly arranging all the fracture porosity numerical values on the rectangular coordinate system;
correspondingly arranging all the matrix porosity degree values on the rectangular coordinate system;
and obtaining a scatter diagram of the fracture porosity value and the matrix porosity value in the rectangular coordinate system.
Preferably, said data distinguishing said reservoir from said dry zone in said scatter plot comprises the steps of:
acquiring the scatter diagram;
representing data of the reservoir in the scatter plot using a first marker;
representing data of the dry layer in the scatter plot using a second marker;
marking fracture porosity values in the reservoir and the dry layer with a first scale;
marking a matrix porosity value in the reservoir and the dry layer with a second scale.
Preferably, said determining a fracture porosity lower limit value and a matrix porosity lower limit value from said reservoir and said dry layer data comprises the steps of:
acquiring a first fracture porosity value and a first matrix porosity value corresponding to the reservoir;
acquiring a second fracture porosity value and a second matrix porosity value corresponding to the dry layer;
plotting the first fracture porosity value, the second fracture porosity value, the first matrix porosity value, and the second matrix porosity value within the same coordinate system;
obtaining a first boundary transition zone of the first fracture porosity value and the second fracture porosity value;
taking the median value of the first boundary line transition zone as the fracture porosity lower limit value;
obtaining a second boundary line transition zone of the first matrix porosity value and the second matrix porosity value;
taking the median value of the second boundary line transition zone as the lower matrix porosity limit value.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: according to the method for determining the porosity lower limit of the fractured-porous carbonate reservoir, the two types of porosities (fracture porosity and matrix porosity) in the carbonate are used for describing respective regression modes respectively, and respective calculation formulas are obtained; and the porosity of two types of oil testing layers is calculated by utilizing oil testing data and well logging curves which are widely possessed by the oil field; compiling through a scatter diagram, and providing a strong-operability reservoir stratum and dry layer boundary dividing method; and meanwhile, the lower limits of the two types of porosities are determined, and a basis is provided for the evaluation of the fractured porous carbonate reservoir.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for determining a lower porosity limit of a fracture-porosity carbonate reservoir according to an embodiment of the present invention.
Detailed Description
The present invention will be specifically explained below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented thereby. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In an embodiment of the present application, the present invention provides a method of determining a lower limit of porosity of a fractured-pore carbonate reservoir, as shown in fig. 1, the method comprising the steps of:
s1: dividing a test oil layer in a target area into a reservoir layer and a dry layer;
in the embodiment of the application, the data of the oil testing layer section can be divided into two types according to the petroleum and gas industry standard SY6293-2008 exploration oil testing working specification of the people's republic of China, wherein one type is a reservoir, and the reservoir comprises a type that the daily liquid production amount of an oil layer, a gas layer, a water-containing oil layer, an oil-water-containing water layer, a low-yield oil gas layer and the like is higher than the dry layer standard; the second type is a dry layer, and the daily liquid yield is lower than the standard of the dry layer.
In the embodiment of the present application, the advantage of dividing the test oil interval in the target area into the reservoir and the dry layer is to classify the data in a targeted manner to prepare for the subsequent steps.
S2: acquiring basic data of the target area;
in this embodiment of the present application, the acquiring of the basic data of the target area in step S2 includes the steps of:
acquiring core data of the target area;
acquiring logging curve data of the target area;
and acquiring the oil testing data of the target area.
In an embodiment of the present application, a method for acquiring core data of the target area includes: during the drilling process (i.e., the process in which the drill bit drills through the formation and grinds the rock), a circular core drill bit is used to remove a cylindrical rock sample, i.e., a core sample, from within the hole as the target zone is approached.
In an embodiment of the present application, the method for obtaining the well-logging curve data of the target area includes: various logging instruments are put into the well by utilizing physical principles such as electricity, magnetism, sound and the like and utilizing logging cables, and the ground testing instrument continuously records various changed parameters along the shaft along with the depth, so that logging curve data are obtained.
In the embodiment of the present application, the method for acquiring the oil test data of the target area includes: and carrying out underground perforation on the target layer, then testing the oil, gas and water yield, acquiring data such as bottom hole pressure, oil, gas and water physical properties and the like, and directly judging an oil layer, a gas layer and a water layer according to the data.
In the embodiments of the present application, the benefit of obtaining the base data for the target area is to obtain a large number of raw production data samples, providing a source for data analysis by the present method.
S3: calculating a fracture porosity value and a matrix porosity value of the formation testing interval;
in the embodiment of the present application, the step of calculating the fracture porosity value and the matrix porosity value of the formation interval in step S3 includes the steps of:
calculating the fracture porosity of the fracture in the target region according to the basic data;
acquiring a fracture porosity logging calculation formula according to the basic data and the fracture porosity;
calculating the matrix porosity of the core in the target area according to the basic data;
and acquiring a matrix porosity logging calculation formula according to the basic data and the matrix porosity.
In an embodiment of the present application, the calculating the fracture porosity of the fracture in the target region according to the basic data comprises:
acquiring core data of the target area;
identifying a carbonate rock core in the target area according to the core data;
selecting a core segment having fracture development in the carbonate core;
measuring the fracture density, fracture length and fracture width of the fracture;
calculating the average crack length of the crack according to the crack length;
calculating the average crack width of the crack according to the crack width;
calculating a product of the fracture density, the average length of the fracture, and the average width of the fracture;
and taking the product value as the fracture porosity.
In the embodiment of the application, a carbonate rock core in a target area is identified through core data (rock color, mineral characteristics, hydrochloric acid drop foaming degree and the like) (the identification method is specifically shown in rock core analysis method SY/T5336-2006 of oil and gas industry standard of the people's republic of China), then a core section with cracks developing in the carbonate rock core is selected, and the well number and the depth of the core section are recorded; and then measuring and recording the fracture density of the core fracture (namely the number of the fractures in a range of 1m & lt 2 & gt), the fracture length (unit m) and the fracture width (unit m), respectively calculating the average fracture length and the average fracture width according to the fracture length and the fracture width, and calculating the fracture porosity according to a formula of fracture porosity = fracture density multiplied by fracture average length multiplied by fracture average width.
In the present embodiment, the fracture measured and recorded at this step refers to an unfilled fracture. Part of cracks in the core can be filled with minerals such as calcite, dolomite and quartz, and the filled cracks do not cover the filled cracks due to the fact that the filled cracks do not have the significance of oil and gas storage. In addition, in order to improve the regression effect below, as many cores as possible need to be selected for measurement.
In the embodiment of the present application, the expression of the fracture porosity logging calculation formula is:
F＝(0.33×DEN+1.51×AC-0.36×CAL-0.47)/100，
wherein F is fracture porosity (in%), DEN is density log value (in g/cm 3), AC sonic log value (in us/m), CAL is caliper log value (in cm);
the expression of the matrix porosity logging calculation formula is as follows:
B＝0.00028e 0.1784×AC ；
where B is the matrix porosity (in%) and AC is the sonic log value (in us/m).
In the embodiment of the present application, the advantage of calculating the fracture porosity of the fracture in the target region according to the basic data is to obtain an intuitive, reliable and quantitative fracture pore development.
In an embodiment of the present application, the obtaining a fracture porosity logging calculation formula according to the base data and the fracture porosity includes:
acquiring a density curve of the cracks in the target area;
acquiring an acoustic time difference logging curve of the fracture;
acquiring a natural gamma curve of the crack;
acquiring a caliper log of the fracture;
acquiring the fracture porosity of the fracture;
performing multiple regression on the density curve, the sonic time difference logging curve, the natural gamma curve, the caliper logging curve and the fracture pore space;
and taking the multiple regression result as the well logging calculation formula of the fracture porosity.
It is known that the occurrence of a crack in the core causes the log data of this depth interval to have corresponding response characteristics, specifically:
(1) the density of the rock is reduced due to the cracks, so that the density curve (which can reflect the density of the rock) of the crack development section is reduced;
(2) the acoustic time difference logging curve reflects the speed of the rock propagation acoustic wave, and the acoustic time difference is increased due to the fact that the rock propagation acoustic wave speed is slowed down and the crack development is caused;
(3) the presence of fractures (referred to herein as unfilled fractures) allows mud invasion during drilling, and the natural gamma curve increases with increased mud content (invaded mud), so the natural gamma increases;
(4) when the cracks develop more, the stratum is easy to collapse in the crack area, the borehole of the well drilling is affected, and the borehole diameter logging curve reflecting the borehole is increased.
In the embodiment of the present application, multivariate regression can be performed through Excel software according to the curve sensitive to fracture development, that is, multivariate regression is performed on the fracture porosity calculated in step S2 and the density curve, the acoustic wave time difference logging curve, the natural gamma curve and the caliper logging curve, and the regression result is a fracture porosity logging calculation formula.
In the embodiment of the present application, the expression of the fracture porosity logging calculation formula is:
F＝(0.33×DEN+1.51×AC-0.36×CAL-0.47)/100，
wherein F is fracture porosity (in%), DEN is density log value (in g/cm 3), AC sonic log value (in us/m), CAL is caliper log value (in cm);
in the embodiment of the application, the advantage of obtaining the fracture porosity logging calculation formula according to the basic data and the fracture porosity is that the fracture porosity can be calculated by using well logging curve data, and oil and gas wells usually have well logging curves, so that a large amount of fracture porosity data can be obtained.
In an embodiment of the present application, the calculating the porosity of the matrix of the core in the target region according to the basic data includes:
acquiring core data of the target area;
identifying a carbonate rock core in the target area according to the core data;
selecting a core section with a crack that does not develop in the carbonate core;
obtaining a plunger sample from the core section;
performing core porosity test on the plunger sample;
and obtaining the matrix porosity of the rock core according to the test result.
In the embodiment of the application, a carbonate rock core in a target area is identified through core data (rock color, mineral characteristics, hydrochloric acid drop foaming degree and the like) (the identification method is specifically shown in rock core analysis method SY/T5336-2006 of oil and gas industry standard of the people's republic of China), then a core section with a crack which does not develop in the carbonate rock core is selected, and the well number and the depth of the core section are recorded; then, a plunger sample is taken from the core, and the porosity test of the core is carried out, so that the matrix porosity of the core is obtained.
In the embodiment of the application, the principle of obtaining the matrix porosity of the core according to the core porosity test result is as follows, the core is washed, dried and weighed, then the saturated formation water is removed and weighed, and the difference value of the two is divided by the formation water density to obtain the pore volume. The pore volume divided by the rock volume is the porosity. An advantage of calculating the matrix porosity of the core in the target zone from the base data is to obtain quantitative, intra-industry common porosity data.
In an embodiment of the present application, the obtaining a matrix porosity log calculation formula according to the basic data and the matrix porosity includes:
acquiring acoustic time difference logging curve data of the rock core in the target area;
obtaining the matrix porosity of the core;
performing exponential regression on the sonic moveout log data and the matrix porosity;
and taking the index regression result as the matrix porosity logging calculation formula.
It is known that acoustic moveout is very sensitive to matrix porosity, and therefore it is the most common method to reflect the porosity of the core using acoustic moveout log data.
In the embodiment of the application, the acoustic time difference logging curve data in the step S3 and the matrix porosity of the core in the step S4 are subjected to exponential regression, so that the regression result is used as a matrix porosity logging calculation formula.
In the embodiment of the present application, the expression of the matrix porosity logging calculation formula is:
B＝0.00028e 0.1784×AC ，
where B is the matrix porosity (in%) and AC is the sonic log value (in us/m).
In the embodiment of the present application, the advantage of obtaining the matrix porosity log calculation formula according to the base data and the matrix porosity is that the fracture porosity can be calculated by using well logging curve data, and oil and gas wells usually have well logging curves, so that a large amount of fracture porosity data can be obtained.
S4: drawing a scatter plot of the fracture porosity values and the matrix porosity values;
in the embodiment of the present application, the step S4 of plotting the fracture porosity value and the matrix porosity value includes the steps of:
establishing a rectangular coordinate system by taking the porosity of the crack as a vertical coordinate and the porosity of the matrix as a horizontal coordinate;
obtaining all of the fracture porosity values and the matrix porosity values;
correspondingly arranging all the fracture porosity numerical values on the rectangular coordinate system;
correspondingly arranging all the matrix porosity degree values on the rectangular coordinate system;
and obtaining a scatter diagram of the fracture porosity value and the matrix porosity value in the rectangular coordinate system.
In the embodiment of the application, a rectangular coordinate system is established in excel software by taking the porosity of the cracks as the ordinate and the porosity of the matrix as the abscissa, then the numerical values of the porosity of the cracks and the numerical values of the porosity of the matrix calculated in the step S3 are correspondingly arranged on the rectangular coordinate system, and then a scatter diagram is made in the rectangular coordinate system.
In the embodiment of the application, the advantage of drawing the scatter diagram of the fracture porosity value and the matrix porosity value is to obtain two visual distributions of data, and lay a foundation for determining the lower limit value.
S5: distinguishing data of the reservoir and the dry layer in the scatter diagram;
in an embodiment of the present application, the step of distinguishing the data of the reservoir and the dry layer in the scatter diagram in step S5 includes the steps of:
acquiring the scatter diagram;
representing data of the reservoir in the scatter plot using a first marker;
representing data of the dry layer in the scatter diagram by using a second mark;
marking fracture porosity values in the reservoir and the dry layer with a first scale;
marking a matrix porosity value in the reservoir and the dry layer with a second scale.
In the embodiment of the present application, two sets of data of a reservoir and a dry layer in the scattergram are distinguished by different markers in the scattergram, for example, red may be used to represent the data of the reservoir, and yellow may be used to represent the data of the dry layer. Further, since the fracture porosity is between 0.001% and 0.7%, the fracture porosity values in the reservoir and the dry layer are marked by logarithmic scales; and the porosity of the matrix is between 1% and 14%, so the porosity value of the matrix in the reservoir layer and the dry layer is marked by adopting a normal scale.
In the embodiment of the application, the data of the reservoir and the dry layer are distinguished in the scatter diagram, so that the matrix porosity and the fracture porosity of the reservoir and the dry layer are visually seen, and the lower limit value is easy to obtain.
S6: determining a fracture porosity lower limit value and a matrix porosity lower limit value according to the data of the reservoir stratum and the dry layer;
in an embodiment of the present application, the determining of the fracture porosity lower limit value and the matrix porosity lower limit value according to the data of the reservoir and the dry layer in step S6 includes the steps of:
acquiring a first fracture porosity value and a first matrix porosity value corresponding to the reservoir;
acquiring a second fracture porosity value and a second matrix porosity value corresponding to the dry layer;
plotting the first fracture porosity value, the second fracture porosity value, the first matrix porosity value, and the second matrix porosity value within the same coordinate system;
obtaining a first boundary transition zone of the first fracture porosity value and the second fracture porosity value;
taking the median value of the first boundary line transition zone as the fracture porosity lower limit value.
Obtaining a second boundary transition zone of the first matrix porosity value and the second matrix porosity value;
and taking the middle value of the second boundary transition zone as the lower matrix porosity limit value.
In the embodiment of the application, because the fracture porosity values corresponding to the reservoir stratum and the dry stratum are drawn in the same coordinate system, theoretically, the fracture porosity value corresponding to the boundary between the reservoir stratum and the dry stratum is the lower fracture porosity limit value. In actual operation, however, due to the oil testing process, the randomness of sampling, the testing errors of the steps and the like, the reservoir stratum and the dry layer have a certain degree of intersection, and the boundary between the reservoir stratum and the dry layer is not obvious, so that the intermediate value of the transition zone of the reservoir stratum and the dry layer is selected as the lower limit value of the fracture porosity. In this example, the lower limit of the fracture porosity is 0.011%.
In the embodiment of the present application, since the matrix porosity values corresponding to the reservoir and the dry layer are plotted in the same coordinate system, theoretically, the matrix porosity value corresponding to the boundary between the reservoir and the dry layer is the lower limit value of the matrix porosity. In actual operation, due to the reasons of the oil testing process, the randomness of sampling, the testing error of the previous steps and the like, the reservoir layer and the dry layer have a certain degree of intersection and are not obviously separated, so the intermediate value of the transition zone of the reservoir layer and the dry layer is selected as the lower limit value of the porosity of the matrix. In this example, the lower limit of the porosity of the matrix is 2.4%.
In the embodiment of the application, the advantage of determining the lower limit of the porosity of the fracture and the lower limit of the porosity of the matrix according to the data of the reservoir and the dry layer is that by adopting the dividing method, the porosity of the matrix of the reservoir and the lower limit of the porosity of the fracture are directly obtained.
According to the method for determining the lower limit of the porosity of the fractured-porosity carbonate reservoir, the two types of porosities (fracture porosity and matrix porosity) in the carbonate are used for describing respective regression modes respectively, and respective calculation formulas are obtained; the porosity of two types of oil testing layers is calculated by utilizing oil testing data and well logging curves which are widely possessed by the oil field; compiling through a scatter diagram, and providing a strong-operability reservoir stratum and dry layer boundary dividing method; and meanwhile, the lower limits of the two types of porosities are determined, and a basis is provided for the evaluation of the fractured porous carbonate reservoir.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element. The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
In short, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method of determining a lower limit of porosity of a fractured-porosity carbonate reservoir, the method comprising the steps of:
dividing a test oil layer in a target area into a reservoir layer and a dry layer;
acquiring basic data of the target area;
calculating a fracture porosity value and a matrix porosity value of the test oil interval;
drawing a scatter plot of the fracture porosity values and the matrix porosity values;
distinguishing data of the reservoir and the dry layer in the scatter diagram;
and determining a fracture porosity lower limit value and a matrix porosity lower limit value according to the data of the reservoir layer and the dry layer.
2. The method of determining a lower fracture-pore carbonate reservoir porosity limit of claim 1, wherein calculating the fracture porosity value and the matrix porosity value for the formation interval further comprises:
calculating fracture porosity of the fracture in the target region according to the basic data;
acquiring a fracture porosity logging calculation formula according to the basic data and the fracture porosity;
calculating the matrix porosity of the core in the target area according to the basic data;
and acquiring a matrix porosity logging calculation formula according to the basic data and the matrix porosity.
3. The method for determining a lower porosity limit of a fractured-pore carbonate reservoir according to claim 1, wherein the step of obtaining the basic data of the target area comprises the steps of:
acquiring core data of the target area;
acquiring logging curve data of the target area;
and acquiring the oil testing data of the target area.
4. The method for determining a lower fracture porosity limit for a carbonate reservoir of the fracture pore type as claimed in claim 2, wherein said calculating the fracture porosity of the fractures in the target zone from the base data comprises the steps of:
acquiring core data of the target area;
identifying a carbonate rock core in the target area according to the core data;
selecting a core segment having fracture development in the carbonate core;
measuring the fracture density, fracture length and fracture width of the fracture;
calculating the average crack length of the crack according to the crack length;
calculating the average crack width of the crack according to the crack width;
calculating a product of the fracture density, the fracture average length, and the fracture average width;
and taking the product value as the fracture porosity.
5. The method for determining a lower fracture porosity limit for a carbonate reservoir of the fracture porosity type as claimed in claim 2, wherein said obtaining a fracture porosity log calculation formula based on said base data and said fracture porosity comprises the steps of:
acquiring a density curve of the cracks in the target area;
acquiring a sonic time difference logging curve of the fracture;
acquiring a natural gamma curve of the crack;
acquiring a caliper log of the fracture;
acquiring the fracture porosity of the fracture;
performing multiple regression on the density curve, the sonic time difference log curve, the natural gamma curve, the caliper log curve and the fracture pore space;
and taking the multiple regression result as the well logging calculation formula of the fracture porosity.
6. The method for determining the lower limit of the porosity of a fractured porous carbonate reservoir according to claim 2, wherein the step of calculating the porosity of the matrix of the core in the target area according to the basic data comprises the steps of:
acquiring core data of the target area;
identifying a carbonate rock core in the target area according to the core data;
selecting a core section with a crack that does not develop in the carbonate core;
obtaining a plunger sample from the core section;
performing core porosity test on the plunger sample;
and obtaining the matrix porosity of the core according to the test result.
7. The method for determining the lower limit of the porosity of a fractured pore carbonate reservoir according to claim 2, wherein the step of obtaining a matrix porosity logging calculation formula according to the basic data and the matrix porosity comprises the following steps:
acquiring acoustic time difference logging curve data of the rock core in the target area;
obtaining the matrix porosity of the core;
performing exponential regression on the sonic moveout log data and the matrix porosity;
and taking the index regression result as the matrix porosity logging calculation formula.
8. The method of determining a lower fracture pore type carbonate reservoir porosity limit of claim 1, wherein the step of plotting the scatter plot of the fracture porosity value and the matrix porosity value comprises the steps of:
establishing a rectangular coordinate system by taking the porosity of the crack as a vertical coordinate and the porosity of the matrix as a horizontal coordinate;
obtaining all of the fracture porosity values and the matrix porosity values;
correspondingly arranging all the fracture porosity numerical values on the rectangular coordinate system;
correspondingly arranging all the matrix porosity degree values on the rectangular coordinate system;
and obtaining a scatter diagram of the fracture porosity value and the matrix porosity value in the rectangular coordinate system.
9. The method of determining a lower porosity limit of a fractured-pore carbonate reservoir according to claim 1, wherein the data for distinguishing the reservoir from the dry zone in the scatter plot comprises the steps of:
acquiring the scatter diagram;
representing data of the reservoir in the scatter plot using a first marker;
representing data of the dry layer in the scatter plot using a second marker;
marking fracture porosity values in the reservoir and the dry layer with a first scale;
marking a matrix porosity value in the reservoir and the dry layer with a second scale.
10. The method of determining a lower fracture porosity limit for a carbonate reservoir according to claim 1, wherein the determining a lower fracture porosity limit value and a lower matrix porosity limit value from the reservoir and the dry zone data comprises the steps of:
acquiring a first fracture porosity value and a first matrix porosity value corresponding to the reservoir;
acquiring a second fracture porosity value and a second matrix porosity value corresponding to the dry layer;
plotting the first fracture porosity value, the second fracture porosity value, the first matrix porosity value, and the second matrix porosity value within the same coordinate system;
obtaining a first boundary transition zone of the first fracture porosity value and the second fracture porosity value;
taking the median value of the first boundary line transition zone as the fracture porosity lower limit value;
obtaining a second boundary line transition zone of the first matrix porosity value and the second matrix porosity value;
taking the median value of the second boundary line transition zone as the lower matrix porosity limit value.
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