Disclosure of Invention
The invention aims to provide a hydrocarbon source rock logging evaluation method based on equivalent saturation; the method is a novel logging method for quickly, continuously and accurately evaluating the organic carbon content and the hydrocarbon yield of the argillaceous source rock by using conventional logging information, has the characteristics of low measurement cost and large data volume, and is easy to popularize and apply in a large scale.
In order to achieve the purpose, the invention adopts the following technical scheme:
a hydrocarbon source rock logging evaluation method based on equivalent saturation comprises the following steps:
1) Obtaining the total porosity and the effective porosity of the source rock according to a neutron density intersection method;
2) Establishing a functional relation among the total porosity of the source rock, the effective porosity of the source rock and the oil-gas saturation of the source rock to obtain the oil-gas saturation of the source rock;
3) Establishing a functional relation among the total porosity of the source rock, the oil-gas saturation of the source rock and the content of the residual hydrocarbon in the source rock to obtain the content of the residual hydrocarbon in the source rock;
4) Establishing a functional relation among the residual hydrocarbon content in the source rock, the kerogen of the source rock, the mixed density of oil gas, the rock density of the source rock and the total organic carbon of the source rock to obtain the total organic carbon of the source rock;
5) And establishing a functional relation among the total organic carbon, the organic matter maturity, the oil-gas density and the hydrocarbon yield of the source rock to obtain the hydrocarbon yield of the source rock.
Preferably, the functional relationship among the total porosity of the source rock, the effective porosity of the source rock and the oil-gas saturation of the source rock in the step 2) is established through a formula (I), a formula (II) and a formula (III);
S og =1-S wt (II);
in the formulae (I), (II) and (III),
S wt represents the total water saturation of the source rock and has the unit of vol%;
S og representing the oil-gas saturation of the source rock, and the unit is vol%;
a. b, m and n represent empirical parameters and are dimensionless;
R t the unit of the true resistivity of the hydrocarbon source rock is omega-m;
R z the resistivity of mixed formation water is expressed and has the unit of omega.m;
R w the resistivity of a pure rock water layer is shown, and the unit is omega.m;
R wc the resistivity of a pure mud rock water layer is expressed and the unit is omega.m;
φ t represents the total porosity of the source rock, and the unit is vol%;
φ e representing the effective porosity of the source rock in vol%.
Preferably, for a new exploration area, the values of a, b, m and n can take empirical values of a = b =1,m = n =2.
Preferably, the true resistivity of the source rock is obtained from a deep resistivity log.
Preferably, the functional relationship among the total porosity of the source rock, the hydrocarbon saturation and the residual hydrocarbon content in the source rock in the step 3) is established by a formula (IV);
VHC=φ t ·S og (IV);
in the formula (IV), the compound is shown in the specification,
VHC represents the residual hydrocarbon content in the source rock in vol%;
φ t represents the total porosity of the source rock, and the unit is vol%;
S og the hydrocarbon source rock oil-gas saturation is expressed in vol%.
Preferably, the functional relationship among the residual hydrocarbon content in the source rock, the kerogen and oil gas mixed density of the source rock, the rock density of the source rock and the total organic carbon of the source rock in the step 4) is established by a formula (V);
TOC=VHC·ρ gog /ρ hr (V);
in the formula (V), the compound represented by the formula (V),
TOC represents the total organic carbon of the source rock in wt%;
VHC represents the residual hydrocarbon content in the source rock in vol%;
ρ gog the mixed density of the kerogen and the oil gas of the source rock is expressed in g/cm 3 ;
ρ hr The rock density of the source rock is expressed in g/cm 3 。
Preferably, the value of the mixed density of the kerogen of the source rock and the oil gas is 1.2g/cm of default value 3 。
Preferably, the rock density of the hydrocarbon source rock is 2.65g/cm in default value 3 。
Preferably, the functional relationship among the total organic carbon, organic matter maturity, oil gas density and hydrocarbon yield of the source rock in the step 5) is established by a formula (VI);
HCI=TOC·Ro·ρ og ·10 (VI);
in the formula (VI), the compound represented by the formula (VI),
HCI represents the hydrocarbon yield of the source rock and has the unit of kg/t;
ro represents organic matter maturity, dimensionless;
ρ og represents the density of oil gas in g/cm 3 。
Preferably, the oil gas density is 0.8g/cm of default value 3 。
Preferably, the organic matter maturity is calculated by an arrhenius formula or obtained by geological analysis data.
Preferably, the organic matter maturity is 0.5.
Preferably, the organic matter maturity is calculated according to formula (VII) and formula (VIII),
Ro=1-α (VII);
in the formulae (VII) and (VIII),
ro represents organic matter maturity, dimensionless;
alpha represents the residual carbon of the hydrocarbon source rock and is dimensionless;
T z the mean annual absolute temperature of the paleo-geothermal field, which changes with the depth, is expressed in K;
T 0 representing the mean absolute temperature of the paleo-surface year as a function of depth, in units of K;
and t represents organic matter burying time and has a unit of Ma.
The invention has the following beneficial effects:
the invention utilizes the porosity and resistivity curve of the conventional logging series (namely, the logging series widely applied to various oil fields in China at present) to calculate the oil and gas saturation of the hydrocarbon source rock, and utilizes the total porosity, kerogen and the density of the hydrocarbon source rock to convert the oil and gas saturation of the hydrocarbon source rock into the organic carbon content and the hydrocarbon yield by a model equivalent method so as to achieve the aim of quantitatively evaluating the organic carbon content and the hydrocarbon yield of the hydrocarbon source rock by the conventional logging series. The method provides an evaluation idea of indirectly reflecting the organic carbon content and the hydrocarbon yield by utilizing the oil-gas saturation of the argillaceous source rock from the perspective of contribution degree of oil gas generated by organic carbon of the source rock to the current oil-gas reservoir, greatly improves effectiveness and accuracy of conventional logging information for evaluating the organic carbon content of the source rock, and further enriches and perfects a logging evaluation method for the organic carbon content of the source rock.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
The hydrocarbon source rock logging evaluation method based on equivalent saturation is researched according to the residual hydrocarbon concentration of generated hydrocarbons in the oil producing rock. Oil and gas are generated and are transported outwards from the oil and gas source rock in different phase states under the action of various geological stresses, but no matter the oil and gas are transported in early stage or late stage, no matter the oil and gas are transported in water phase or in free phase, the saturation degree of the oil, gas and water remained in the source rock after the oil, gas and water are partially extruded out of the source rock is constant, namely, the saturation degree of the oil and gas of the liquid discharged from the source rock at a certain moment is the same as that of the liquid remained in the pores of the source rock. Therefore, hydrocarbon expulsion does not reduce hydrocarbon saturation in the source rock. Furthermore, along with the process of compaction and hydrocarbon expulsion, the oil-gas saturation of the source rock can only be increased and can not be reduced, because the maturity of the oil-producing rock is increased along with the increase of the buried depth, the conversion is increased, the cumulative production of oil-gas is increased, and the pore space and the water content of the stratum are reduced along with the increase of the buried depth. Therefore, the oil-gas saturation in the pores of the source rock in the same layer is increased along with the increase of the burial depth. The oil gas content in the source rock is a product after organic matters are mature, so that the oil gas content is in direct proportion to the abundance of the organic matters and has a direct relation with the type and the maturity of the organic matters. Therefore, the hydrocarbon source rock has oil and gas saturation S og Directly reflects the hydrocarbon generation potential of the source rock and is the basis for well logging and evaluation of the source rock. The method of the invention is used for generating oil gas from organic carbon in source rockIn the view of contribution degree of oil and gas reservoirs, an evaluation idea of indirectly reflecting organic carbon content and hydrocarbon yield by utilizing oil and gas saturation of argillaceous source rock is provided. The hydrocarbon source rock well logging explanation model is shown in fig. 2 to fig. 6. In FIGS. 4 to 6, φ w Represents the porosity of water in the source rock; phi is a t Represents the total porosity of the source rock; phi is a og Representing the porosity of the hydrocarbons in the source rock.
As can be seen from fig. 2 to 6, the non-hydrocarbon source rock volume model is composed of only mudstone framework particles and pore water; the immature source rock volume model rich in organic matters consists of mudstone framework particles, organic matters and pore water; the mature hydrocarbon source rock volume model consists of mudstone framework particles, residual organic matters, pore water and residual hydrocarbons. Therefore, the invention uses a logging method to calculate the total porosity and hydrocarbon saturation of the born source rock, thereby realizing the logging evaluation of the source rock.
Specifically, the hydrocarbon source rock logging evaluation method based on equivalent saturation comprises the following steps in combination with fig. 1:
s101, obtaining the total porosity and the effective porosity of the source rock according to a neutron density intersection method;
s102, establishing a functional relation among the total porosity of the source rock, the effective porosity of the source rock and the oil-gas saturation of the source rock to obtain the oil-gas saturation of the source rock;
s103, establishing a functional relation among the total porosity of the source rock, the oil-gas saturation of the source rock and the content of the residual hydrocarbons in the source rock to obtain the content of the residual hydrocarbons in the source rock;
s104, establishing a functional relation among the residual hydrocarbon content in the source rock, the kerogen of the source rock, the mixed density of oil gas, the rock density of the source rock and the total organic carbon of the source rock to obtain the total organic carbon of the source rock;
s105, establishing a functional relation among the total organic carbon, the organic matter maturity, the oil gas density and the hydrocarbon yield of the source rock to obtain the hydrocarbon yield of the source rock.
It should be understood by those skilled in the art that the neutron density intersection method in the present invention is a conventional technical method, and is not described herein; step S102, determining the oil and gas saturation of the source rock according to the functional relationship among the total porosity of the source rock, the effective porosity of the source rock and the oil and gas saturation of the source rock and by combining the total porosity of the source rock and the effective porosity of the source rock obtained in the step S101; step S103, determining the content of the residual hydrocarbon in the source rock according to the functional relationship among the total porosity of the source rock, the hydrocarbon saturation of the source rock and the content of the residual hydrocarbon in the source rock by combining the total porosity of the source rock obtained in the step S101 and the hydrocarbon saturation of the source rock obtained in the step S102; step S104, determining the total organic carbon of the source rock according to the functional relationship among the content of the residual hydrocarbon in the source rock, the kerogen and oil gas mixed density of the source rock, the rock density of the source rock and the total organic carbon of the source rock and by combining the content of the residual hydrocarbon in the source rock obtained in the step S103; and S105, determining the hydrocarbon production rate of the source rock according to the functional relation among the total organic carbon of the source rock, the organic matter maturity, the oil-gas density and the hydrocarbon production rate of the source rock and by combining the total organic carbon of the source rock obtained in the S104.
As a preferred embodiment of the present invention, the functional relationship among the total porosity of the source rock, the effective porosity of the source rock and the hydrocarbon saturation of the hydrocarbon gas in the source rock in S102 is established by formula (I), formula (II) and formula (III);
S og =1-S wt (II);
in the formulae (I), (II) and (III),
S wt represents the total water saturation of the source rock and has the unit of vol%;
S og representing the oil-gas saturation of the source rock, and the unit is vol%;
a. b, m and n represent empirical parameters and are dimensionless;
R t the unit of the true resistivity of the hydrocarbon source rock is omega-m;
R z the resistivity of mixed formation water is expressed and has the unit of omega.m;
R w the resistivity of a pure rock water layer is shown, and the unit is omega.m;
R wc the resistivity of a pure mud rock water layer is expressed and the unit is omega.m;
φ t represents the total porosity of the source rock, and the unit is vol%;
φ e represents the effective porosity of the hydrocarbon source rock, and the unit is vol%.
It will be understood by those skilled in the art that the true resistivity R of the source rock in the present invention t Obtaining the resistivity R of the water layer of the pure rock through logging information w And the pure mudstone water layer resistivity R wc The resistivity of the pure rock section water layer and the resistivity of the pure mudstone section water layer are obtained respectively, and the obtaining method is a conventional method and is not described herein any more.
As a preferred embodiment of the present invention, for a new exploration area, the a, b, m, n may take empirical values of a = b =1,m = n =2. It should be understood by those skilled in the art that the values of a, b, m, and n for the old exploration area in the present invention are conventional values or obtained by a rock-electricity experiment, and are not described herein in detail.
In a preferred embodiment of the present invention, the true resistivity of the source rock is obtained from a deep resistivity log. It should be understood by those skilled in the art that the deep resistivity well log according to the present invention is obtained according to well log data, and the obtaining method of the deep resistivity well log is a conventional technical means, and is not described herein.
As a preferred embodiment of the present invention, the functional relationship among the total porosity of the source rock, the hydrocarbon saturation of the hydrocarbon and the content of the remaining hydrocarbons in the source rock in S103 is established by formula (IV);
VHC=φ t ·S og (IV);
in the formula (IV), the compound is shown in the specification,
VHC represents the residual hydrocarbon content in the source rock in vol%;
φ t represents the total porosity of the source rock, and the unit is vol%;
S og the hydrocarbon source rock oil-gas saturation is expressed in vol%.
As a preferred embodiment of the present invention, the functional relationship among the residual hydrocarbon content in the source rock, the kerogen and hydrocarbon gas mixture density of the source rock, the rock density of the source rock and the total organic carbon of the source rock in S104 is established by formula (V);
TOC=VHC·ρ gog /ρ hr (V);
in the formula (V), the compound represented by the formula (V),
TOC represents the total organic carbon of the source rock in wt%;
VHC represents the residual hydrocarbon content in the source rock in vol%;
ρ gog the mixed density of the kerogen and the oil gas of the source rock is expressed in g/cm 3 ;
ρ hr The rock density of the source rock is expressed in g/cm 3 。
In a preferred embodiment of the invention, the mixed density of the kerogen and the oil gas in the source rock is 1.2g/cm of default value 3 。
As a preferred embodiment of the invention, the rock density of the hydrocarbon source rock is a default value of 2.65g/cm 3 。
As a preferred embodiment of the present invention, the functional relationship among the total organic carbon, organic matter maturity, hydrocarbon gas density and hydrocarbon yield of the source rock in S105 is established by formula (VI);
HCI=TOC·Ro·ρ og ·10 (VI);
in the formula (VI), the compound represented by the formula (VI),
HCI represents the hydrocarbon yield of the hydrocarbon source rock and has the unit of kg/t;
ro represents organic matter maturity, dimensionless;
ρ og represents the density of oil gas in g/cm 3 。
As a preferred embodiment of the invention, the oil gas density takes a default value0.8g/cm 3 。
In a preferred embodiment of the present invention, the organic matter maturity is calculated by the arrhenius formula or obtained from geological analysis data. It should be understood by those skilled in the art that the method for obtaining the localization analysis data of the present invention is a conventional technical means, and is not described herein in detail.
In a preferred embodiment of the present invention, the organic matter maturity is 0.5.
As a preferred embodiment of the present invention, the organic matter maturity is calculated according to formula (VII) and formula (VIII),
Ro=1-α (VII);
in the formulae (VII) and (VIII),
ro represents organic matter maturity, dimensionless;
alpha represents the residual carbon of the hydrocarbon source rock and is dimensionless;
T z the mean annual absolute temperature of the paleo-geothermal field, which changes with the depth, is expressed in K;
T 0 representing the mean absolute temperature of the paleo-surface year as a function of depth, in units of K;
and t represents organic matter burying time and has a unit of Ma. It will be understood by those skilled in the art that the ancient geothermal annual average absolute temperature T as a function of depth as described in the present invention z And the annual mean absolute temperature T of the paleo-surface as a function of depth 0 The obtaining method is a conventional method and is not described herein.
The present invention will be further described with reference to the following examples.
Example 1
The embodiment provides a hydrocarbon source rock logging evaluation method based on equivalent saturation, which is used for evaluation of an M well and comprises the following steps:
1) Obtaining the total porosity of the hydrocarbon source rock according to a neutron density intersection methodφ t And effective porosity phi of source rock e FIG. 7 shows a log interpretation achievement plot for M wells, in which:
the 1 st channel is a depth channel;
the 2 nd channel is a lithologic section channel;
lane 3 is reservoir analysis;
the 4 th pass is permeability and crack
Lane 5 contains gas index and saturation;
the 6 th channel is a fluid analysis channel;
comparing the logging evaluation results of the source rock (including logging and calculating the content of residual hydrocarbon, the content of organic carbon, the hydrocarbon yield and the content of organic carbon analyzed by rock debris);
the 8 th path is a storage cover combination;
lanes 9-11 are mudlogging, resistivity logging, and porosity logging Qu Xiandao, respectively;
2) Establishing a functional relation among the total porosity of the source rock, the effective porosity of the source rock and the oil-gas saturation of the source rock according to a formula (I), a formula (II) and a formula (III), and calculating to obtain the oil-gas saturation of the source rock according to the total porosity of the source rock and the effective porosity of the source rock obtained in the step 1);
3) Establishing a functional relation among the total porosity of the source rock, the oil and gas saturation of the source rock and the residual hydrocarbon content in the source rock according to a formula (IV), and calculating to obtain the residual hydrocarbon content in the source rock according to the total porosity of the source rock obtained in the step 1) and the oil and gas saturation of the source rock obtained in the step 2);
4) Establishing a functional relation among the content of the residual hydrocarbon in the source rock, the kerogen of the source rock and the mixed density of oil gas, the rock density of the source rock and the total organic carbon of the source rock through a formula (V), and calculating to obtain the total organic carbon of the source rock according to the content of the residual hydrocarbon in the source rock obtained in the step 3);
5) And (3) establishing a functional relation among the total organic carbon, the organic matter maturity, the oil-gas density and the hydrocarbon yield of the source rock according to a formula (VI), and calculating the hydrocarbon yield of the source rock according to the total organic carbon of the source rock obtained in the step 4).
The results of the logging calculations of this example were compared with the results of the cuttings analysis, and the results are shown in fig. 7 and 8.
As can be seen from FIG. 7, the calculated organic carbon content of the log of this embodiment in the 6 th trace has better consistency with the analyzed organic carbon content of the debris, both in terms of the magnitude and the trend of the change.
As can be seen from FIG. 8, the organic carbon content of the source rock calculated by logging in this embodiment has a good correlation with the organic carbon content of the debris analysis, and the correlation coefficient reaches 0.83. The method can better reflect the organic carbon content and hydrocarbon generation potential of the actual source rock, can be used for source rock evaluation, reduces the cost and expands the scale application.
According to the residual hydrocarbon content, the organic carbon content, the hydrocarbon yield and the like obtained by the hydrocarbon source rock logging evaluation method, parameters in the 7 th path in the attached figure 7 can be obtained, and the graph shows that the organic carbon content calculated by logging has good correlation with the organic carbon content analyzed by experiments, which shows that the method for evaluating the organic carbon content of the hydrocarbon source rock by logging is feasible and can reflect the development degree and the organic carbon size of the hydrocarbon source rock of the stratum, and the hydrocarbon production potential of the hydrocarbon source rock can be further evaluated through the calculated hydrocarbon yield.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.