CN112257010A - Calculation method for resistivity variation lower limit of mat sandstone oil layer - Google Patents
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- 238000004364 calculation method Methods 0.000 title claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000004576 sand Substances 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 7
- 238000012360 testing method Methods 0.000 claims abstract description 7
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 239000003129 oil well Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000008859 change Effects 0.000 description 7
- 239000004568 cement Substances 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- 239000012530 fluid Substances 0.000 description 5
- 230000035699 permeability Effects 0.000 description 5
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 229910000514 dolomite Inorganic materials 0.000 description 4
- 239000010459 dolomite Substances 0.000 description 4
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Abstract
The invention relates to a method for calculating the resistivity variation lower limit of a mat sandstone oil layer, which comprises the steps of firstly calculating the shale content of sandstone of each logging record point of an oil testing well section by utilizing a natural gamma curve; and then constructing an oil layer resistivity variation lower limit calculation model by using the shale content, and calculating the mat-shaped sandstone oil layer resistivity variation lower limit by using the oil layer resistivity variation lower limit calculation model to provide a basis for judging the oil-water layer of the mat-shaped sand micro-phase region. The method is easy to operate and has strong practicability. Under the background that the current oil and gas exploration difficulty is more and more big, under the condition that the exploration and development thought turns to the thin difference layer, the model is provided, assistance is necessarily provided for the identification of the oil field thin difference layer, and a new technical means is further provided for the increasing, storing and production of the oil field.
Description
Technical Field
The invention relates to the technical field of oil and gas development, in particular to a calculation method for a resistivity variation lower limit value of a mat sandstone oil layer.
Background
At present, the lower limit value of the resistivity of an oil layer is determined mainly by using oil testing data on site, and the determined lower limit value is a fixed value. After the lower limit value is determined, a reservoir with resistivity higher than the lower limit value is judged as an oil layer, and a reservoir with resistivity lower than the lower limit value is judged as a water layer.
When the lower limit value of the resistivity of the oil layer is a fixed value, the following defects exist: firstly, the lower limit value is difficult to determine, part of the oil layer can be missed when the lower limit value is high, and part of the water layer can be mistaken for the oil layer when the lower limit value is low; secondly, the determined lower limit value is usually suitable for judging the thick sand layer oil-water layer of the river channel microphase and cannot be suitable for judging the argillaceous sandstone or sand-mudstone thin interbed oil-water layer of the mat-shaped sand microphase area; thirdly, the well logging interpretation compliance rate is low and cannot meet the production requirements.
Disclosure of Invention
The invention provides a calculation method of a resistivity change lower limit value of a mat-shaped sandstone oil layer, which aims to solve the problems in oil layer interpretation and can effectively improve the accuracy of identification and judgment of the properties of oil deposit fluid in a mat-shaped sand micro-phase region.
The technical scheme for solving the technical problems is as follows:
a calculation method for resistivity variation lower limit of a mat sandstone oil layer comprises the following steps:
s1, calculating the shale content of the sandstone of each logging recording point of the oil well testing section by using a natural gamma curve;
s2, constructing an oil layer resistivity variation lower limit calculation model by using the argillaceous content, calculating a mat-shaped sandstone oil layer resistivity variation lower limit by using the model, and identifying an oil-water layer of a mat-shaped sand micro-phase region;
the oil layer resistivity variation lower limit calculation model is as follows:
where a and b are constants, a is 11.5, b is 0.03, vsh is the shale content in%, Ro is the lower limit of the oil layer resistivity in Ω · m.
Further, the calculating the shale content of the sandstone of each logging record point of the oil testing well section by using the natural gamma curve comprises the following steps:
s11, calculating a natural gamma relative value:
in the formula ,ΔGRRepresenting the relative value of natural gamma, GR representing the log value of natural gamma of the target layer, GRminNatural gamma minimum, GR, representing pure sandstone segments in the interval of interestmaxRepresenting the maximum natural gamma value of the pure mudstone stratum of the target interval;
s12, calculating the argillaceous content by using an empirical formula:
wherein GCUR is Hilbert index, and empirical coefficients related to the age of the formation.
Further, the Hilbert index GCUR takes 4.5.
The invention has the beneficial effects that: the factors influencing the resistivity of the reservoir are more, besides the oil-containing property, the factors also comprise lithology factors, such as the content of mud, the content of calcium and dolomite cement, and the like, the increase of the content of mud can cause the resistivity of the oil layer to be reduced, and the increase of the content of calcium cement can cause the resistivity of the oil layer to be increased, so the lower limit value of the resistivity of the oil layer is not a fixed value but a variable. The shale content in the sandstone of the microphase area of the mat-shaped sand is higher, which generally causes the resistivity of an oil layer to be reduced to a certain extent. In order to solve the problem of low resistance of an oil layer in interpretation of a mat-shaped sand micro-phase region oil layer, a set of oil layer resistivity change lower limit calculation model is provided, and the accuracy of judgment of the properties of oil reservoir fluid in the mat-shaped sand micro-phase region can be effectively improved.
The oil saturation of the oil layer is an important factor influencing the resistivity of the oil layer, and if the influence of the oil content on the resistivity is only considered, the resistivity of the oil layer is high when the oil saturation is high; when the oil saturation is low, the resistivity of the oil layer is low; the resistivity of the pure water layer is lower than the resistivity of the oil-bearing layer.
At present, the oil-water layer well logging explanation is to work according to the principle, and the explanation idea is suitable for riverway sandstone with high porosity and high permeability.
However, the siltstone at the front edge of the delta is mostly fine sandstone or siltstone, and the deposition process of the detritus particles is usually accompanied by a certain amount of argillaceous sediments. The mud deposits fill the middle of the pores, resulting in reduced pore throat radius, reduced porosity, reduced permeability, and increased saturation of the irreducible water. Thus, as the shale content of the sandstone increases, the resistivity of the reservoir decreases. Sometimes, the resistivity of the oil layer is decreased to a large extent, close to the resistivity of the water layer, or even lower than the resistivity of the water layer (part of the water layer is increased in the content of calcareous and dolomite cement, the resistivity is increased, and the resistivity value is generally lower than that of the oil layer with high oil saturation).
The 'oil layer resistivity change lower limit calculation model' is a brand-new oil layer calculation model, and can solve a plurality of problems encountered in the process of identifying the mat sandstone oil layer, such as: the resistivity of the oil-water layers is crossed, and the oil layer is difficult to identify; the lower limit value is difficult to determine, the interpretation coincidence rate is low, and the like.
The 'oil layer resistivity change lower limit calculation model' provided at this time is simple, easy to operate and strong in practicability, and the developed mat-shaped sand micro-phase regions of the oil field all have popularization and application values. Under the background that the current oil and gas exploration difficulty is more and more serious, under the condition that an exploration and development idea turns to a thin difference layer, the model is provided, assistance is necessarily provided for identifying the fluid property of the thin difference layer of the oil field, and a new technical means is further provided for increasing storage and increasing production.
Drawings
Fig. 1 is a flowchart of a calculation method of a resistivity variation lower limit value of a mat sandstone reservoir according to an embodiment of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a calculation method of a resistivity variation lower limit value of a mat sandstone oil layer, which comprises the following steps as shown in figure 1:
s1, calculating the shale content of the sandstone of each logging recording point of the oil well testing section by using a natural gamma curve;
first, the natural gamma relative value is calculated:
in the formula ,ΔGRRepresenting the relative value of natural gamma, GR representing the log value of natural gamma of the target layer, GRminNatural gamma minimum, GR, representing pure sandstone segments in the interval of interestmaxRepresenting the maximum natural gamma value of the pure mudstone stratum of the target interval;
then, calculating the argillaceous content by using an empirical formula:
wherein GCUR is Hilbert index, and empirical coefficients related to the age of the formation. The third series of strata was taken as 3.7 and the old strata was taken as 2. In practical application, the Hill index cannot be mechanically applied, and a numerical value suitable for the geological characteristics of a region should be selected. When the value of the Hilchi index is 4.5 in the study, the physical property interpretation error reaches the minimum.
S2, constructing an oil layer resistivity variation lower limit calculation model by using the argillaceous content, calculating a mat-shaped sandstone oil layer resistivity variation lower limit by using the model, and identifying an oil-water layer of a mat-shaped sand micro-phase region;
the oil layer resistivity variation lower limit calculation model is as follows:
where a and b are constants, a is 11.5, b is 0.03, vsh is the shale content in%, Ro is the lower limit of the oil layer resistivity in Ω · m.
The mud deposits fill the middle of the pores, resulting in reduced pore throat radius, reduced porosity, reduced permeability, and increased saturation of the irreducible water. Thus, as the shale content of the sandstone increases, the resistivity of the reservoir decreases.
The factors influencing the resistivity of the reservoir are more, besides the oil-containing property, the factors also comprise lithology factors, such as the content of mud, the content of calcium and dolomite cement, and the like, the increase of the content of mud can cause the resistivity of the oil layer to be reduced, and the increase of the content of calcium cement can cause the resistivity of the oil layer to be increased, so the lower limit value of the resistivity of the oil layer is not a fixed value but a variable. The shale content in the sandstone of the microphase area of the mat-shaped sand is higher, which generally causes the resistivity of an oil layer to be reduced to a certain extent. In order to solve the problem of low resistance of an oil layer in interpretation of a mat-shaped sand micro-phase region oil layer, a set of oil layer resistivity change lower limit calculation model is provided, and the accuracy of judgment of the properties of oil reservoir fluid in the mat-shaped sand micro-phase region can be effectively improved.
The oil saturation of the oil layer is an important factor influencing the resistivity of the oil layer, and if the influence of the oil content on the resistivity is only considered, the resistivity of the oil layer is high when the oil saturation is high; when the oil saturation is low, the resistivity of the oil layer is low; the resistivity of the pure water layer is lower than the resistivity of the oil-bearing layer.
At present, the oil-water layer well logging explanation is to work according to the principle, and the explanation idea is suitable for riverway sandstone with high porosity and high permeability.
However, the siltstone at the front edge of the delta is mostly fine sandstone or siltstone, and the deposition process of the detritus particles is usually accompanied by a certain amount of argillaceous sediments. The mud deposits fill the middle of the pores, resulting in reduced pore throat radius, reduced porosity, reduced permeability, and increased saturation of the irreducible water. Thus, as the shale content of the sandstone increases, the resistivity of the reservoir decreases. Sometimes, the resistivity of the oil layer is decreased to a large extent, close to the resistivity of the water layer, or even lower than the resistivity of the water layer (part of the water layer is increased in the content of calcareous and dolomite cement, the resistivity is increased, and the resistivity value is generally lower than that of the oil layer with high oil saturation).
The 'oil layer resistivity change lower limit calculation model' is a brand-new oil layer calculation model, and can solve a plurality of problems encountered in the process of identifying the mat sandstone oil layer, such as: the resistivity of the oil-water layers is crossed, and the oil layer is difficult to identify; the lower limit value is difficult to determine, the interpretation coincidence rate is low, and the like.
The 'oil layer resistivity change lower limit calculation model' provided at this time is simple, easy to operate and strong in practicability, and the developed mat-shaped sand micro-phase regions of the oil field all have popularization and application values. Under the background that the current oil and gas exploration difficulty is more and more serious, under the condition that an exploration and development idea turns to a thin difference layer, the model is provided, assistance is necessarily provided for identifying the fluid property of the thin difference layer of the oil field, and a new technical means is further provided for increasing storage and increasing production.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (3)
1. A method for calculating the lower limit value of resistivity variation of a mat sandstone oil layer is characterized by comprising the following steps:
s1, calculating the shale content of the sandstone of each logging recording point of the oil well testing section by using a natural gamma curve;
s2, constructing an oil layer resistivity variation lower limit calculation model by using the argillaceous content, calculating a mat-shaped sandstone oil layer resistivity variation lower limit by using the model, and identifying an oil-water layer of a mat-shaped sand micro-phase region;
the oil layer resistivity variation lower limit calculation model is as follows:
wherein a and b are constants, a is 11.5, b is 0.03, vsh is the shale content, and Ro is the lower limit of the resistivity of the oil layer.
2. The method of claim 1, wherein calculating the shale content of the sandstone of each logging point of the test well section by using a natural gamma curve comprises:
s11, calculating a natural gamma relative value:
in the formula ,ΔGRRepresenting the relative value of natural gamma, GR representing the log value of natural gamma of the target layer, GRminNatural gamma minimum, GR, representing pure sandstone segments in the interval of interestmaxRepresenting the maximum natural gamma value of the pure mudstone stratum of the target interval;
s12, calculating the argillaceous content by using an empirical formula:
wherein GCUR is Hilbert index, and empirical coefficients related to the age of the formation.
3. The method according to claim 2, wherein the Hilbert index GCUR takes a value of 4.5.
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| US20120143508A1 (en) * | 2010-12-01 | 2012-06-07 | Conocophillips Company | Automatic estimation of source rock petrophysical properties |
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