CN105003257A - Method for qualitatively recognizing high-temperature high-pressure methane gas layer and carbon dioxide gas layer - Google Patents

Abstract

The invention provides a method for qualitatively recognizing a high-temperature high-pressure methane gas layer and carbon dioxide gas layer. The method comprises the following steps: 1) conducting standard processing on well logging data; (2) analyzing the data scale well logging interpretation result through a rock core assay, and precisely calculating the effective porosity and the gas saturation of a storage layer; 3) eliminating influence on density and neutron well logging data by well hole environment and slurry; (4) utilizing the response characteristic difference of the methane gas layer and the carbon dioxide gas layer by density and neutron well logging data to calculate a neutron and density curve interval NDS curve of the high-temperature high-pressure gas layer sections, and then dividing the NDS curve by porosity and gas saturation so as to obtain an NDS_Sg curve. The distinguishment standards of the methane gas layer and the carbon dioxide gas layer are established through the comparison of size of the NDS_Sg curve of gas-bearing pores, the distinguishment precision of the high-temperature high-pressure methane gas layer and carbon dioxide gas layer can be obviously improved, and the coincidence rate is improved from the conventional 50% to 85% or higher.

Description

A kind of method of qualitative recognition HTHP methane gas-bearing formation and carbon dioxide gas-bearing formation

Technical field

The present invention relates to the well logging of oily natural gas and rock core test analysis technical field, the specifically a kind of method of qualitative recognition HTHP methane gas-bearing formation and carbon dioxide gas-bearing formation.

Background technology

Methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation identification is one of key technology of THE WESTERN SOUTH CHINA SEA basin HTHP natural gas reservoir exploration and development.Utilize methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) response characteristic of gas-bearing formation to density and neutron well logging be not both one of common method differentiating gas-bearing formation gas component type.

Utilize density, neutron curve to calculate gas-bearing formation section NDS value to the research methods innovation in natural gas exploration and development field owned by France of gas-bearing formation gas component type identification, mainly utilize well-log information and core experiment data, research methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation to the Different Effects feature of density and neutron data, finally set up methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) density of gas-bearing formation, neutron affect difference relation, and this values of disparity method, thus fast, accurately identify methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation, for natural gas exploration and development provides test layer bit decisions foundation, instruct gas field exploration to develop.

Neutron well logging curve record be apparent hydrogen index, hydrogen index is defined as the ratio of every cubic centimetre of this material hydrogen atom concentration and the hydrogen atom concentration of same volume pure water when 75 ℉.According to definition, the hydrogen index of pure water, carbon dioxide (CO ₂) not hydrogen atoms in gas, thus its hydrogen index is 0; And methane (CH ₄) molecular formula of gas is CH4, containing 4 hydrogen atoms, its hydrogen index is about about 0.5 under formation conditions.Because the depth of stratum of general oil-gas exploration is more than 800 meters, formation temperature pressure is all higher than CO ₂critical-temperature and critical pressure, therefore, carbon dioxide (CO in subterranean strata hole ₂) store mutually with the dense fluids of gas-liquid two-phase formation, its density can reach 0.5 ~ 0.85g/cm3; And methane (CH ₄) gas density is about about 0.3g/cm3.As can be seen here, methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) the response characteristic difference of gas-bearing formation to density and neutron data is obvious.But neutron, density curve are simultaneously by the impact of the factors such as lithology, borehole condition, mud immersion, thus gas-bearing formation gas component type coincidence rate is not high directly to utilize original form of logs to differentiate, through statistics, gas-bearing formation gas component type identification coincidence rate can only reach about 50% usually, produces bring very large difficulty to the construction of natural gas fields.

Summary of the invention

For above Problems existing, the present invention proposes a kind of qualitative recognition HTHP methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) method of gas-bearing formation, the nonfluid influence factors such as lithology, borehole condition, slurry compounding are eliminated when utilizing density, neutron data to differentiate gas-bearing formation gas type, thus can reflect the effect characteristics of gas-bearing formation section gas with various type to density and neutron data truly, intuitively, (HTHP gas-bearing formation) reservoir (gas) fluid type is differentiated, and coincidence rate has brought up to more than 85% by existing 50%.

For solving the problems of the technologies described above, this application provides a kind of qualitative recognition HTHP methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) method of gas-bearing formation, comprise the steps:

S1, Normalizationof Logging Data process: choose mud stone reference lamina, select classical histogram method to carry out standardization to log, eliminate density and neutron well logging data between well from well due to the deviation that instrument series is different or the non-geologic(al) factor such as the error of graduation causes;

S2, by rock core assay data scale result of log interpretation, accurate Calculation reservoir effecive porosity, gas saturation;

S3, eliminating borehole environment, slurry compounding are on the impact of density, neutron well logging data;

S4, utilize density, neutron well logging data to methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) the response characteristic difference of gas-bearing formation, calculate HTHP gas-bearing formation section neutron, density curve interval NDS curve, then by NDS curve divided by degree of porosity and gas saturation, obtain NDS_Sg curve, set up methane (CH by comparative unit containing the size of NDS_Sg curve of spiracular slit ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation discrimination standard:

Methane (CH ₄) gas-bearing formation: NDS_Sg>-30;

Carbon dioxide (CO ₂) gas-bearing formation: NDS_Sg<-30;

In formula: NDS_Sg representation unit is containing the NDS value of spiracular slit.

Described rock core assay data scale result of log interpretation process is use core analysis porosity and the product test well log interpretation effecive porosity of water saturation and the means of interpretation of saturation ratio and adjust, until meet error requirements.

The impact on density, neutron well logging data of described eliminating borehole environment, slurry compounding refers to: hole diameter, slurry compounding factor, on the impact of density data and neutron data, adopt well logging classical theory plate and empirical formula to correct.

Described gas-bearing formation effecive porosity and water saturation computational process are: according to geologic characteristics, set up by resistivity, density and neutron well logging data after correcting through standardization, borehole environment the degree of porosity, the water saturation log response equation that meet work area actual conditions, calculate gas-bearing formation effecive porosity and water saturation.

Beneficial effect

The application has following technique effect or advantage:

Because this method is utilizing density, neutron data eliminates lithology when differentiating HTHP gas-bearing formation gas type, borehole condition, the nonfluid influence factors such as mud immersion, and by neutron, density curve interval NDS curve is divided by degree of porosity and gas saturation, obtain the NDS_Sg curve of unit containing spiracular slit, reflect the influencing characterisitic of gas with various component to density and neutron data more realistically, substantially increase HTHP gas-bearing formation gas type and differentiate coincidence rate, criterion reflects gas type by numerical values recited, gas-bearing formation gas type is differentiated and has brought up to quantitative identification by the qualitative discrimination in past, use more convenient being easier to operate, this numerical value can be combined with seismic data, carry out gas component type prediction in the plane, greatly improve the directive function to natural gas exploration and development.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is mud methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation NDS_Sg curve histogram.

Detailed description of the invention

In order to better understand technique scheme, below in conjunction with Figure of description and concrete embodiment, technique scheme is described in detail.

The invention provides a kind of method of qualitative recognition HTHP methane gas-bearing formation and carbon dioxide gas-bearing formation, the nonfluid influence factors such as lithology, borehole condition, slurry compounding are eliminated when utilizing density, neutron data to differentiate gas-bearing formation gas type, thus can reflect the effect characteristics of gas-bearing formation section gas with various type to density and neutron data truly, intuitively, make distinguishing reservoir fluid type coincidence rate bring up to more than 85% by existing 50%.

As shown in Figure 1, the method for a kind of qualitative recognition HTHP methane gas-bearing formation of the present invention and carbon dioxide gas-bearing formation, comprises the steps:

1) Normalizationof Logging Data process, eliminates density and neutron well logging data between well from well due to the deviation that instrument series is different or the non-geologic(al) factor such as the error of graduation causes;

2) by rock core assay data scale result of log interpretation, accurate Calculation reservoir effecive porosity, water saturation;

Well-log information reflects reservoir situation and gas bearing condition indirectly by measuring the physical parameter of subsurface rock, need can correct interpretation and evaluation reservoir through actual geologic information scales such as rock cores.

Described Core-Calibrated Logging mainly comprises use core analysis porosity and the product test well log interpretation effecive porosity of water saturation and the means of interpretation of water saturation and adjusts, until meet error requirements.

Described gas-bearing formation effecive porosity and water saturation are calculated as: according to geologic characteristics, set up by resistivity, density and neutron well logging data after correcting through standardization, borehole environment the degree of porosity, the water saturation log response equation that meet work area actual conditions, calculate gas-bearing formation effecive porosity and water saturation.

3) borehole environment, slurry compounding is got rid of on the impact of density, neutron well logging data;

Described well-log information environmental correction specifically refers to: because the environmental factor such as temperature, pressure, mud property, borehole condition (as whether " expanding ") when gathering well-log information affects to some extent on well-log information, therefore classical theoretical plate and empirical formula need be selected to carry out environmental correction according to practical logging situation and logging program.

4) utilize density, neutron well logging data to methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) the response characteristic difference of gas-bearing formation, calculate HTHP gas-bearing formation section neutron, density curve interval NDS curve, then by NDS curve divided by degree of porosity and gas saturation, obtain NDS_Sg curve, set up methane (CH by comparative unit containing the size of NDS_Sg curve of spiracular slit ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation discrimination standard:

Methane (CH ₄) gas-bearing formation: NDS_Sg>-30;

Carbon dioxide (CO ₂) gas-bearing formation: NDS_Sg<-30; ;

Neutron, density curve interval NDS curve design formulas are:

$NDS=\frac{(RHOB-1.95)}{0.05}-\frac{(0.45-NPHI)}{0.03}$

In formula, NDS is neutron, density curve spacing value, dimensionless; RHOB is density log value, g/cm ³; NPHI is neutron well logging value, decimal;

Reservoir effecive porosity uses neutron, density curve calculates, and gas saturation uses resistivity curve to calculate, and design formulas is:

$\mathrm{\&phi;}=\frac{{\mathrm{\&phi;}}_{na}-{\mathrm{\&phi;}}_{da}}{4}+\sqrt{\frac{{\mathrm{\&phi;}}_{na}^2+{\mathrm{\&phi;}}_{da}^2}{8}}$

${\mathrm{\&phi;}}_{da}=\frac{{\mathrm{\&rho;}}_b-{\mathrm{\&rho;}}_{ma}}{1-{\mathrm{\&rho;}}_{ma}}-V_{sh}\frac{{\mathrm{\&rho;}}_{sh}-{\mathrm{\&rho;}}_{ma}}{1-{\mathrm{\&rho;}}_{ma}}$

${\mathrm{\&phi;}}_{na}=\frac{H-H_{ma}}{1-H_{ma}}-V_{sh}\frac{H_{sh}-H_{ma}}{1-H_{ma}}$

$Sw=\sqrt[2]{\frac{Rw}{Rt*{\mathrm{\&phi;}}^2}}$

Sg＝1-Sw

In formula, φ is gas-bearing formation effecive porosity, decimal; φ na is neutron porosity, decimal; φ da is density porosity, decimal; ρ _bfor density log value, g/cm ³; ρ _mafor skeletal density, g/cm ³; ρ _shfor pure shale density, g/cm ³; V _shfor shale content, decimal; H is neutron well logging value, decimal; H _mafor skeleton hydrocarbon resistivity index, decimal; H _shfor pure shale hydrocarbon resistivity index, decimal; Sw is gas-bearing formation water saturation, decimal; Sw is gas-bearing formation gas saturation, decimal; Rw is formation water resistivity, ohm.m; Rt is stratum well logging resistivity, ohm.m.

Reservoir shale content uses gamma ray curve to calculate, and design formulas is:

$SH=\frac{GR-{\mathrm{GR}}_{\min }}{{\mathrm{GR}}_{\max }-{\mathrm{GR}}_{\min }}$

$VSH=\frac{2^{2*SH}-1}{2^2-1}$

In formula: GR, GRmin, GRmax-are respectively log value, maximum value, the minimum value of the gamma ray curve calculating shale content;

VSH-is stratum shale content, %;

SH-is SI.

NDS_Sg design formulas is:

$MDS\_Sg=\frac{MDS}{(\mathrm{\&phi;}*Sg)}$

In formula: NDS_Sg is the NDS value that unit contains spiracular slit; Dimensionless;

φ is gas-bearing formation effecive porosity, decimal;

Sg is gas-bearing formation gas saturation, decimal;

The above, it is only preferred embodiment of the present invention, not any pro forma restriction is done to the present invention, although the present invention with preferred embodiment demonstration as above, but and be not used to limit the present invention, any those skilled in the art, do not departing within the scope of technical solution of the present invention, make a little change when the technology contents of above-mentioned announcement can be utilized or be modified to the Equivalent embodiments of equivalent variations, in every case be the content not departing from technical solution of the present invention, according to any simple modification that technical spirit of the present invention is done above embodiment, equivalent variations and modification, all still belong in the scope of technical solution of the present invention.

Claims (4)

1. a method for qualitative recognition HTHP methane gas-bearing formation and carbon dioxide gas-bearing formation, is characterized in that, comprises the steps:

S1, Normalizationof Logging Data process: choose mud stone reference lamina, select classical histogram method to carry out standardization to log, eliminate density and neutron well logging data between well from well due to the deviation that instrument series is different or the non-geologic(al) factor such as the error of graduation causes;

S2, by rock core assay data scale result of log interpretation, accurate Calculation reservoir effecive porosity, gas saturation;

S3, eliminating borehole environment, slurry compounding are on the impact of density, neutron well logging data;

S4, utilize density, neutron well logging data to methane (CH ₄) gas-bearing formation and carbon dioxide (CO ₂) the response characteristic difference of gas-bearing formation, calculate HTHP gas-bearing formation section neutron, density curve interval NDS curve, then by NDS curve divided by degree of porosity and gas saturation, obtain NDS_Sg curve, set up methane (CH by comparative unit containing the size of NDS_Sg curve of spiracular slit ₄) gas-bearing formation and carbon dioxide (CO ₂) gas-bearing formation discrimination standard:

Methane (CH ₄) gas-bearing formation: NDS_Sg>-30;

Carbon dioxide (CO ₂) gas-bearing formation: NDS_Sg<-30;

In formula: NDS_Sg representation unit is containing the NDS value of spiracular slit.

2. the method for a kind of qualitative recognition HTHP methane gas-bearing formation according to claim 1 and carbon dioxide gas-bearing formation, it is characterized in that, described rock core assay data scale result of log interpretation process is use core analysis porosity and the product test well log interpretation effecive porosity of water saturation and the means of interpretation of saturation ratio and adjust, until meet error requirements.

3. the method for a kind of qualitative recognition HTHP methane gas-bearing formation according to claim 1 and carbon dioxide gas-bearing formation, it is characterized in that, the impact on density, neutron well logging data of described eliminating borehole environment, slurry compounding refers to: hole diameter, slurry compounding factor, on the impact of density data and neutron data, adopt well logging classical theory plate and empirical formula to correct.

4. the method for a kind of qualitative recognition HTHP methane gas-bearing formation according to claim 1 and carbon dioxide gas-bearing formation, it is characterized in that, described gas-bearing formation effecive porosity and water saturation computational process are: according to geologic characteristics, set up by resistivity, density and neutron well logging data after correcting through standardization, borehole environment the degree of porosity, the water saturation log response equation that meet work area actual conditions, calculate gas-bearing formation effecive porosity and water saturation.