CN1740785A - A Method for Predicting Deep Oil and Gas Reservoirs Using BTEX Anomalies in Submarine Shallow Sediments - Google Patents

Abstract

The invented method used BTEX in sea-bottom shallow-layer sediment as geochemical mark of hydrocarbon reservoir, and utilizes the equipments of purging trapping apparatus, gas chromatograph with photo ionization detector and computer, etc. and adopts the techniques of sample pretreatment, separation, identification and high-sensibility measurement so as to predicate the deep hydrocarbon reservoir. Said invention also provides the working principle of said method and its concrete working steps.

Description

The method of BTEX predicting abnormality deep oil-gas reservoir in the sea-bottom shallow sediment

Technical field:

The present invention relates to a kind of new method of predicting the seabed deep oil-gas reservoir, belong to the oil and gas geochemistry field.

Background technology:

The guiding theory of oil and gas geochemical exploration is hydro carbons vertical migration mechanism.It has been generally acknowledged that from hydrocarbon-bearing pool and rise and the gas that comes that principal ingredient is a methane, be indication underground oil and gas " courier " that hide (messenger).Therefore, the main detected object of traditional oil and gas geochemical exploration is the methane in the soil free gas (soil-gas), promptly detects the gaseous methane light hydrocarbon component that is free in the soil gap and reaches the purpose of seeking hydrocarbon-bearing pool.Because the source of methane is not unique, usually is subjected to the interference of biogenesis methane, effect is not good.

Over past ten years, oil and gas geochemistry is reconnoitred distinctive macromolecule alkane in crude oil volatilization component, naphthenic hydrocarbon and aromatic hydrocarbons development, as the benzene in the aromatic hydrocarbons series, toluene, ethylbenzene, dimethylbenzene (being called for short BTEX) (Burtells G, Jones III V is of subsurface brines can indicate proximity of oil T.1996.Benzenecontent, gas.Oil and gas Journal.June.3:59-64.Calhoun G G, and Hawkins J is detector ' s results good in oil identification.Oil and gas Journal.Mar.30:77-80.Calhoun G G and Hawkins J and toluene are accurate oil predictors.AAPG Bulletin.83 (2): 386.Calhoun L.1999.Benzene L.1998.BTEX, G G, Hawkins, J L., 1999.BTEX geochemical investigation, Permian basin.AmericanAssociation of Petroleum Geologists 1999annual meeting, San Antonio, TX, United States, April 11-14,1999.).Because BTEX is difficult to generate under the earth's surface biological chemical action, and is slow by the degradation speed of yeast, bacterium, enzyme, minority degradable aromatic hydrocarbon is only arranged, and the BTEX molecular volume is little, be easy to migration, the solubleness in underground water is lower.So, there be not humane activity, industrial pollution and petroleum transported to reveal under the influence, BTEX is unusual directly related with deep oil-gas reservoir.The U.S. reported whether the concentration of benzene in detection seawater and the soil free gas (soil-gas) and toluene has the example of hydrocarbon-bearing pool near predicting.As: the content of benzene is followed the trail of the hydrocarbon-bearing pool that the seabed may exist in the measurement seawater such as U.S. Burtell.Secondly, Calhoun and Hawkins extract land topsoil free gas, and the concentration change of measuring benzene and toluene is predicted the oily possibility of underlying formation.Their measurement sensitivity is all in the ppb magnitude.Because surface soil is affected by environment bigger, and seawater is mobile big, certain limitation is arranged aspect the deep oil-gas reservoir predictably descending.

Our seminar once carried out research to the BTEX in the oceanic sediment, that adopt is Micellar Electrokinetic Chromatography method (Wang Shuhu, history faces south, Ma Wanyun, and old small melon prolongs, Liu Jiang, " measure benzene series thing in the oceanic sediment ", analytical test journal, Vol.18 with the Micellar Electrokinetic Chromatography method, No.5 (1999), 5-8.Wang Shuhu, history faces south, Ma Wanyun, old small melon prolongs, Liu Jiang, " the Micellar Electrokinetic Chromatography method is measured benzene, toluene, ethylbenzene and dimethylbenzene in the oceanic sediment ", chromatogram, Vol.18, No.1 (2000), 77-79.Wang Junqi, history faces south, Zhang Songwei, Lin Yuxia, Yang Guangwei, Ma Wanyun, old small melon prolongs, " the Micellar Electrokinetic Chromatography method is measured the benzene compounds in the deposit on marine-bottom surface ", and the test of rock ore deposit, Vol.20, No.1 (2001), 20-22.).This method need carry out sediment sample earlier to become liquid after the chemical treatment, detects the content of BTEX then with capillary electrophoresis apparatus.Because chemical treating process is numerous and diverse, tediously long, sample only chemical treatment just needs 2-3 days, also will with an organic solvent and produce a large amount of debirs, causes environmental pollution.Be limited to hundreds of μ g/L (being hundreds of ppb magnitude) and detect, concerning hundred meters to the sea-bottom shallow sediment of the km depth of water, sensitivity for analysis is not enough.

Summary of the invention

The object of the invention be to seek to the direct indicant of oil gas keep, disturb little, be easy to the appropriate samples medium gathered, overcome the shortcoming that methane is subject to environmental interference, the detection sensitivity of setting up BTEX reaches ppt (10 ^-12) detection method of magnitude, for efficiently reconnoitring of marine oil and gas provides important means.

The invention is characterized in: described BTEX respectively is benzene, toluene, ethylbenzene and the dimethylbenzene in the aromatic hydrocarbons series, and this Forecasting Methodology contains following steps successively:

Step 1:

Design sampling grid in sample region by sampling density every a point of distance that sets, calculate the latitude and longitude coordinates of every bit, reduction of speed and gather sea-bottom shallow sediment when surveying vessel navigates by water with reaching sampled point consistent location with the gravity sampling thief, rapidly cutting sealing in container, number, freezing preservation;

Step 2:

The BTEX hypersensitivity is measured, and this step combines pre-treatment, separation identification and high-sensitivity measurement method in a hypersensitivity detection system and realizes, may further comprise the steps successively:

Step 2.1, example enrichment: utilize to purge the collection instrument, high-purity nitrogen is fed the surface of fluid sample or solid, the component that will analyze is purged out, make it by an adsorption trap enrichment, and then adsorption trap is heated rapidly to makes the component desorption that is adsorbed, take in the gas chromatograph with nitrogen;

Step 2.2, gas chromatographic analysis

Chromatographic column is 60m * 0.32mm * 0.25 μ m high purity quartz capillary column, split sampling 10: 1, flow rate of carrier gas 1ml/min, 180 ℃ of capillary column injector temperatures, 250 ℃ of detecting devices, heating schedule: 50 ℃ of initial temperature, kept 5 minutes, speed with 10 ℃/min rises to 200 ℃ again, keeps 20 minutes, and carrier gas is 99.999% nitrogen;

Step 2.3, the photoionization high-sensitivity measurement, this step is that the ultraviolet source with 10.2eV realizes that output current signal is recorded on the computing machine after amplifying in the photoion detecting device;

Step 3: data analysis and prediction of oil-gas reserve contain following each step:

Step 3.1 is rejected indivedual extra-high-speeds or low especially data;

Step 3.2, ask mean value and the variance of BTEX on each measurement point by following formula:

Mean value is represented with X: $\stackrel{\‾}{X}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{x}_i,$

Variance is represented with S: $S=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{X})}^2}{n-1}},$

Wherein, n is a sample number, x _iIt is the measured value of i measurement point BTEX;

Step 3.3 is the data x of each measurement point _iLatitude and longitude coordinates with this point forms a data file that is called Excel;

Step 3.4 is opened the Surfer mapping software, calls described data, and data are carried out gridding, draws plane equivalence;

Step 3.5, above and below the zone of described mean value as exceptions area, all the other are background area;

Step 3.6 is having the unusual distribution of BTEX and this exceptions area to be defined as the oil and gas anomaly district with structural trapping or the corresponding area of tomography again.

The present invention finds and confirms in the marine bottom sediment that the unusual and oil gas of BTEX keeps definite correlativity, can effectively and quickly determine the hydrocarbon-bearing pool of underliing of seabed deep layer.Engineering effect in the Bohai Sea and marine site, the South Sea proves, this kind marine oil gas reservoir method of exploration can reduce the demand of expensive ocean floor drilling (OFD) sampling exploration in a large number, improve marine oil and gas significantly and reconnoitre efficient, will form substantial economics, may become the new way of sea-bottom oil-gas geochemical exploration.

The present invention utilize the ultratrace of adsorbing in the oceanic sediment with the closely-related aromatic hydrocarbon BTEX of hydrocarbon-bearing pool component, the area of predicting most possible enrichment oil gas reservoir.Set up the analytical approach of the pollution-free quick sampling technology of the oceanic sediment that is suitable for analysing ultra-traces BTEX, sample retention method, highly sensitive purge and trap-gas chromatography-photoionization, detectability reaches 10 ^-12The order of magnitude.Sample rate of the present invention is fast, and the analysis precision height obtains Preliminary Applications in the Bohai Sea, the Nanhai area of China.

Description of drawings

Fig. 1. the process flow diagram of the method for the invention;

Fig. 2. purge and trap method synoptic diagram;

Fig. 3. have the gas chromatograph synoptic diagram of photoionization detector;

Fig. 4. the plane equivalence of 1 toluene level of enforcement of the present invention;

Fig. 5. the seabed 5000m that the unusual distribution of 2 BTEX of enforcement of the present invention and classic method the obtain synoptic diagram that the hydrocarbon-bearing pool prospecting results matches that underlies;

5.1: benzene; 5.2, toluene; 5.3, ethylbenzene; 5.4, dimethylbenzene.

Embodiment:

Fig. 1 techniqueflow.1, sampling: according to work program, the sampling density of pressing a point of 500-1000 rice in sample region designs sampling grid, gathers sea-bottom shallow sediment, sample is sealed in PVC sleeve pipe or other containers freezing preservation rapidly.2, the BTEX ultra-high sensitive is measured: with directly pack into the sample cell of purge and trap instrument of sample, directly heating make the BTEX evaporation, then with cold-trap enrichment is carried out in BTEX absorption after, measure from being dynamically connected with the gas chromatograph that has photoionization detector.3, data analysis: advanced line data pre-service, reject indivedual extra-high-speeds or special low data, obtain mean value and variance then.The data of each measurement point are formed an Excel data file with the latitude and longitude coordinates of this point.Open the Surfer mapping software, call data, data are carried out gridding, draw plane equivalence.Will be above and below the zone of mean value as exceptions area, all the other are background area.Probability distribution check and trend surface analysis be can further carry out, trend surface isoline, background isogram obtained.4, prediction of oil-gas reserve: find out the unusual distributive province of BTEX, in conjunction with tectonic structure, physical prospecting is unusual and the data of existing drilling well, oil gas well, determines the oil and gas anomaly district.Unusual and structural trapping of BTEX or tomography have corresponding relation.Fig. 2 purge and trap.Feed fluid sample (or solid surface) with high-purity nitrogen, the BTEX that analyze is purged out, make it to carry out enrichment by an adsorption trap (cold well).And then adsorption trap is heated rapidly to 180 ℃, and make the component desorption that is adsorbed, take to nitrogen and carry out the component compartment analysis in the gas chromatograph.

Fig. 3 has the gas chromatograph of photoionization detector

Fig. 4 example 1: the toluene level in the Bohai Sea district sea-bottom shallow sediment can reflect the position of the hydrocarbon-bearing pool of underliing in the seabed unusually.Provided the plane equivalence of toluene level among the figure, the dark more representative toluene level of color is high more.As seen from the figure, it is unusual that the top appears in content of toluene, and existing oil gas well mainly is distributed in the abnormal belt of toluene.2514,2515,2518 is oil well among the figure; 2517,2516,2519 is the oil gas well.Predict the outcome and conform to actual.

Fig. 5 example 2: the seabed 5000m that the unusual distribution of BTEX and classic method obtain in the South Sea district shallow sediment hydrocarbon-bearing pool prospecting results that underlies is coincide.(it is high more that color is deeply felt the content that shows BTEX more.Around the pre-drilling well of being determined by physical prospecting, the content of BTEX annular anomaly occurs and the top is unusual.)

Concrete implementation step:

1. judging from gravity, seismic data according to the promptly selected target area of geology, geophysical information, is a basin that distant view is arranged at present, according to the level of detail of estimating, designs geochemistry sample range and sampling grid, calculates the longitude and latitude of each sampled point.

2. implement survey vessel and corresponding gravity sampling instrument, skilled operating personnel with sampling function.

3. be ready to the sample encapsulating material, freezing proof box etc.

4. all material is focused on and leave for the workspace on the ship, prepare sampling.

5. sample in time send lab analysis BTEX.

6. the debugging of purge and trap, gas chromatograph is ready, detects and is limited to the ppt magnitude, sets up the typical curve of conversion usefulness.It is enough big that concentration range is wanted, and contains the high and low concentration that may occur in the sample.

7. sample measurement, concentration is calculated, and figure is unusually drawn in the data pre-service, and layer thickness, lithology factor of porosity, the stratigraphic trap degree of depth, structure data are carried out integrated interpretation in combination.

Sampling and preservation: according to work program, press the sampling density design sampling grid of a point of 500-1000 rice in sample region, calculate the latitude and longitude coordinates of every bit, when ship navigates by water assigned address, ship's speed lowers, the boat-carrying windlass discharges the gravity sampling thief rapidly, utilize action of gravity, sampler is inserted and is gathered the sediment sample in the sediment, this moment windlass with the sampling thief fast lifting to the deck, then with the rapid cutting sealing of bottom sample in PVC sleeve pipe or other containers, numbering, freezing preservation.Whole sampling process absolute prohibition sampling thief and sample are contaminated.

BTEX measures: because the effumability of BTEX, the sample of collection exists difficulty in the process that stores, handles and analyze, and because their background values in ground surface environment are very low, therefore needs the detection means of high sensitivity.Complicacy and the BTEX content of considering oceanic sediment are extremely low, and we have built the ultra-high sensitive detection system that can be used for Marine Geology sample composite measurement with pre-treatment, separation identification and integrally combining of high-sensitivity measurement method.This system adopt the actual deposition matter sample directly heating makes the BTEX evaporation, then with cold-trap enrichment is carried out in BTEX absorption after, measure from being dynamically connected with the gas chromatograph that has photoionization detector.The detectability of the benzene of this system, toluene, ethylbenzene, dimethylbenzene reaches 3ppt, 3ppt successively, 6ppt, 3ppt[annotate 1ppt=10 ^-12].The actual sample sample cell analysis of can directly packing into without any need for chemical reagent, has been avoided tediously long sample chemical pre-treatment.Be controlled at the analysis time of sample about 30-35 minute, and avoided loss, waste liquid in chemical analysis cycle long (about 2-3 days time), the sample preparation process in the past to cause problems such as environmental pollution.The present invention is as follows to the measuring condition of BTEX:

Example enrichment: utilize the purge and trap instrument, feed fluid sample (or solid surface) with high-purity nitrogen, purged 10 minutes, the component that will analyze is purged out, make it to carry out enrichment by an adsorption trap, and then adsorption trap is heated rapidly to 180 ℃, and make the component desorption that is adsorbed, take to nitrogen and carry out the component compartment analysis in the gas chromatograph.

GC conditions: chromatographic column 60m * 0.32mm * 0.25 μ m high purity quartz capillary column, split sampling 10: 1, flow rate of carrier gas 1ml/min (about 18.4cm/sec), 180 ℃ of capillary column injector temperatures, 250 ℃ of detecting devices.Heating schedule: 50 ℃ of initial temperature, kept 5 minutes, the speed with 10 ℃/min rises to 200 ℃ then, keeps 20 minutes.Carrier gas is 99.999% nitrogen.

Photoionization is measured (PID): adopt the ultraviolet source of 10.2eV,, all can be ionized when first ionization energy of testing molecule component less than 10.2eV, especially suitable to the BTEX molecule.The component that is less than or equal to luminous energy when ionization potential enters ionization chamber, and direct or indirect photoionization promptly takes place.Electronics that is produced and positive ion flow to positive and negative electrode respectively, form little electric current.This current signal is recorded on the computing machine after further amplifying.

Data analysis and prediction of oil-gas reserve method:

The first step: data screening.Reject indivedual extra-high-speeds or special low data.

Second step: average and standard deviation, formula is as follows:

$\stackrel{\‾}{X}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{x}_i$

$S=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{X})}^2}{n-1}}$

N: sample number;

x _i: the measurement result of each measurement point BTEX.

The 3rd step: the data of each measurement point are formed an Excel data file with the latitude and longitude coordinates of this point.

The 4th step: open the Surfer mapping software, call data, data are carried out gridding, draw plane equivalence.

The 5th step: unusual identification: will be above and below the zone of mean value as exceptions area.All the other are background area.

The 6th step: determine the oil and gas anomaly district: 1) have BTEX to distribute unusually; 2) unusual and structural trapping or tomography have corresponding relation.

Introduce two embodiments of the present invention below.We are used for Bohai Sea district and South Sea district with the present invention.In Bohai Sea district, the length of the reflection wave time of arrival that receives according to seismoreceiver is determined the shape and the degree of depth of stratum or fault trap, it is unusual that the top appears in content of toluene in the sea-bottom shallow sediment on fault trap, and existing oil gas well mainly is distributed in the abnormal belt of toluene.Toluene level abnormal belt that Fig. 4 has provided and the position of existing oil gas well relation.In South Sea district, the unusual distribution of BTEX is similar basically, and with seabed 5000m that classic method the obtains hydrocarbon-bearing pool prospecting results (see figure 5) of coincideing that underlies.The BTEX content distribution of this explanation in shallow sediment can reflect that 5000m the underlie position of hydrocarbon-bearing pool in seabed distributes.Should particularly point out and be, 50 square kilometres the sample region in work area, marine site, the South Sea, the sampling of deep water shallow sediment, 50 sampled points have only been used 16 hours and have just been finished, an average sampled point 20 minutes.And the BTEX measurement in the sediment sample obtained the well unusual distribution plan of signal to noise ratio (S/N ratio).This deep-sea oil gas reconnoitres sampling efficiency and economic benefit is challenging.This shows that BTEX has following advantage as the oil and gas reservoir geochemistry direct mark in the sea-bottom shallow sediment:

1, BTEX has certain volatility, molecular volume is little, be easy to migration, this compounds that diposits of petroleum contained that buries in deep formation passes through microbubble, molecule or migration forms such as molecular cluster and nanoparticle in very long geochron, be diffused into the face of land gradually, make that consequently such compound concentrations occurs unusual in some stratum in some areas or the face of land.Therefore, BTEX is the direct mark that whether contains oil gas in a kind of reliable evaluation study district.Get rid of outside humane activity, industrial pollution and the petroleum transported leakage, BTEX is unusual and deep oil-gas reservoir is closely related, thereby keeps unique effect to reconnoitring oil gas.

2, BTEX is difficult to generate under the earth's surface biological chemical action, and is slow by the degradation speed of yeast, bacterium, enzyme, and minority degradable BTEX is only arranged.Therefore, near the interference that microbial activities is caused the face of land is little, and good stability has the advantage that Indication of Oil-Gas is hidden " selectivity ";

3, sea-bottom shallow sediment is compared with surface soil more favourable aspect the preservation BTEX as sampling media.Because the protection of going up again seawater and surface deposit is arranged, BTEX is difficult for running off, and with seabed deep-seated oil gas reservoir definite correlativity is arranged.

Claims (1)

1. the method for BTEX predicting abnormality deep oil-gas reservoir in the sea-bottom shallow sediment is characterized in that, described BTEX respectively is benzene, toluene, ethylbenzene and the dimethylbenzene in the aromatic hydrocarbons series, and this Forecasting Methodology contains following steps successively:

Step 1:

Design sampling grid in sample region by sampling density every a point of distance that sets, calculate the latitude and longitude coordinates of every bit, reduction of speed and gather sea-bottom shallow sediment when surveying vessel navigates by water with reaching sampled point consistent location with the gravity sampling thief, rapidly cutting sealing in container, number, freezing preservation;

Step 2:BTEX hypersensitivity is measured, and this step combines pre-treatment, separation identification and high-sensitivity measurement method in a hypersensitivity detection system and realizes, may further comprise the steps successively:

Step 2.1, example enrichment: utilize the purge and trap instrument, high-purity nitrogen is fed the surface of fluid sample or solid, the component that will analyze is purged out, make it by an adsorption trap enrichment, and then adsorption trap is heated rapidly to makes the component desorption that is adsorbed, take in the gas chromatograph with nitrogen;

Step 2.2, gas chromatographic analysis

Chromatographic column is 60m * 0.32mm * 0.25 μ m high purity quartz capillary column, split sampling 10: 1, flow rate of carrier gas 1ml/min, 180 ℃ of capillary column injector temperatures, 250 ℃ of detecting devices, heating schedule: 50 ℃ of initial temperature, kept 5 minutes, speed with 10 ℃/min rises to 200 ℃ again, keeps 20 minutes, and carrier gas is 99.999% nitrogen;

Step 2.3, the photoionization high-sensitivity measurement, this step is that the ultraviolet source with 10.2eV realizes that output current signal is recorded on the computing machine after amplifying in the photoion detecting device;

Step 3: data analysis and prediction of oil-gas reserve contain following each step:

Step 3.1 is rejected indivedual extra-high-speeds or low especially data;

Step 3.2, ask mean value and the variance of BTEX on each measurement point by following formula: mean value is represented with X: $\stackrel{\‾}{X}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{x}_i,$

Variance is represented with S: $S=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{X})}^2}{n-1}},$

Wherein, n is a sample number, x _iIt is the measured value of i measurement point BTEX;

Step 3.3 is the data x of each measurement point _iLatitude and longitude coordinates with this point forms a data file that is called Excel;

Step 3.4 is opened the Surer mapping software, calls described data, and data are carried out gridding, draws plane equivalence;

Step 3.5, above and below the zone of described mean value as exceptions area, all the other are background area;

Step 3.6 is having the unusual distribution of BTEX and this exceptions area to be defined as the oil and gas anomaly district with structural trapping or the corresponding area of tomography again.

Images