WO1992019964A1

WO1992019964A1 - Total sulfur analyzer

Info

Publication number: WO1992019964A1
Application number: PCT/FR1991/000337
Authority: WO
Inventors: Jacques Connan
Original assignee: Elf Petroleum Norge A/S
Priority date: 1991-04-24
Filing date: 1991-04-24
Publication date: 1992-11-12
Also published as: NO924969L; EP0536155A1; NO924969D0

Abstract

Device for analyzing and determining the sulfur contents of different types of sulfur-containing compounds contents in a rock sample of determined weight. The device allows to determine different shows of sulfur and optionally hydrogen and/or oxygen based respectively on the mass of total sulfur for the former and on the mass of the sample for the two latter (hydrogen and oxygen).

Description

TOTAL SULFUR ANALYZER

The present invention relates to a device making it possible to determine, simultaneously, quickly and with high accuracy, on the one hand, the sulfur indices IS 'and hydrogen IH' of a rock sample, and, on the other hand, the total sulfur content included in the rock.

It is customary to characterize the petroleum potential of a source rock by its hydrogen indices I and oxygen index 10 expressed respectively in mg. of HC hydrocarbon products per gram of organic carbon TOC and in mg. of carbon monoxide C0 ₂ per gram of organic carbon TOC contained in the rock studied.

These various indices allow, among others, to characterize the rock for their oil potential, their origin, their ^'degree of evolution. These indices are calculated from the analysis of the organic matter contained in the rock.

Recent studies have shown that a better assessment of the petroleum potential and of the functioning of the parent rocks not only requires taking into account a sulfur index IS, expressed in mg. organic sulfur per gram of organic carbon, in addition to the IH and 10 indices - but also the inclusion of mineral sulfur. A method and a device are known, described in the document FR.A. 039539, for determining the organic sulfur content of geological sediments. According to this document, a sample of a sediment to be studied is heated to a temperature capable of producing the pyrolysis of the organic matter contained in the sample. The combustion of the products resulting from the pyrolysis is then caused to transform the organic sulfur compounds into sulfurous gas (S0 ₂ ) mixed with a small proportion of sulfuric gas (S0 ₃ ), then it is determined using a sulfur dioxide and sulfuric gas the amount of sulfur that was contained in the pyrolyzed organic matter in the sample. Optionally and simultaneously, the quantity of resulting hydrocarbon products is determined. pyrolysis of the residual organic matter in the sample (the erogenous), and the amount of organic carbon.

It is imperative in this device that the temperature to which the sample is subjected does not exceed a value of the order of 500-550 ° C. so that the decomposition of the pyrite does not intervene in the measurements of the quantity of sulfur contained in the pyrolized organic material of the sample, which would then be inaccurate. This device makes it possible to take into account only the organic sulfur contained in the free hydrocarbons and the kerogen and therefore does not make it possible to measure the amount of total sulfur (organic + mineral) included in the sample. The device according to the invention for the qualitative and quantitative analysis of all the sulfur compounds contained ^* in a rock sample, in particular for an evaluation of the petroleum potential of said rock, is characterized in that it comprises: - means for producing a vector stream of helium under pressure,

- An oven, supplied with said helium flow, the temperature of which can be constantly varied up to a temperature of at least 700 ° C. so as to allow the thermal elution of the compounds of the sample to be analyzed placed at the beforehand inside the furnace chamber using means for introducing the samples to be analyzed into the furnace chamber, the flow of helium carrying volatile products produced by the sample at the outlet of the furnace up to a detection set,

- a valve for dividing the flow from the furnace into a predetermined ratio, part of the flow being sent to the detection assembly, the other part being discharged for example into the atmosphere, - a detection assembly comprising means for perform the combustion in a hydrogen-enriched atmosphere of the products transported by the helium flow leaving the oven so as to transform the sulfur-containing compounds essentially in SO, as well as an electrically insulating pipe, in ceramic for example, for conducting the burnt gases after combustion, to a detector, and said SO detector with chemiluminescence, connected to a processing unit allowing the determination of indices of sulfur IS 'and total sulfur.

Preferably, the detection means comprise means for ionizing the gases burned by combustion and for detecting the resulting electric current, which characterizes the hydrocarbon products contained in the input stream of the detection assembly, so that the device allows the simultaneous detection of sulfur and hydrocarbon products. Advantageously, the ionization and the combustion is carried out using an ionizing flame detector, the combustion being maintained by means of an air supply in addition to that of hydrogen.

Advantageously, a CO 2 detector can be connected to the device at the level of the flow fractionation valve, a part of the flow coming from the furnace being at this level sent to the CO 2 detector.

The invention will be better understood and all of its advantages will appear more clearly on reading the following description of a non-limiting embodiment of a device according to the invention illustrated by the appended figures, of which:

FIG. 1 'is a block diagram of a device according to the invention, allowing the determination of sulfur indices and of a hydrogen index,

- Figure 2 is a partial sectional view of the part between the outlet of the oven and the SCD detector in the embodiment described, Figure 3 shows two records characterizing the hydrocarbon products and sulfur products of the same real sample given, respectively from the probe connected to the FID (fig. 3B) and the SCD

(fig. 3A), figure 4 represents the records characterizing the sulfur compounds of a real sample (fig. 4A) and a sample artificially prepared from a mixture of galena and a material from the same core as the real sample (fig. 4B).

The combustion of products from the oven takes place in the flame of an ionizing flame detector (FID) used for analyzes by gas chromatography.

Such use of an FID allows the simultaneous continuous detection of hydrocarbon compounds from the same products from the furnace. It is then necessary to complete the device with an amplification unit for the acquisition of the signals characterizing the combustion products burned in the flame of the FID.

In the FID flame, the sulfur compounds are burned in a hydrogen-rich atmosphere so as to produce the following reaction:

- sulfur compounds + H ₂ + 0 ₂ > SO + other products. These gases resulting from this reaction are introduced into the SCD where they are reacted with ozone. A resulting signal from the SO detector is amplified and transmitted to the processing unit.

In the example of embodiment described, a detection detector SCD 350 marketed by SIEVERS was used as the SO detection system, sold usually for the detection of sulfur in chromatography.

Such a detector makes it possible to have linear measurements of great sensitivity for sulfur compounds, with practically no interference due to the presence of hydrocarbon compounds. The response in terms of chemiluminescence of the simple reaction S0 / 0 ₃ being based on the detection of simple sulfur atoms, the response of the detector is linear unlike those that can provide other types of detector such as the FPD (detector with flame frame). The use of an SO detector makes it possible to have not only a linear response directly usable on a computer, but also a highly sensitive measurement (of the order of 10 picograms per second for a signal with a signal / noise ratio equal to three). The selectivity is also excellent (the amplitude of the peak representative of the sulfur-containing compounds being much greater than that of the peak representative of the hydrocarbon products detected).

A system for sequential introduction of the samples and ejection of the samples after pyrolysis as well as an oven specially developed by the company GEOLAB NOR are used. This oven allows the analysis of a weight of rock or kerogen ranging from 0.1 to 100 milligrams per analysis.

Helium is used as a carrier gas to transport the components to be detected from the FID and SCD furnaces. The signals characterizing on the one hand the sulfur compounds detected by the SCD and on the other hand the hydrocarbon compounds detected using a probe connected to the FID, feed a data processing unit (VG Data Systems "Mulichro" ) for the processing and archiving of data and final results.

The entire oven (19), shown diagrammatically in FIG. 1 - comprises a helium supply (1), the flow of which is controlled at all times using a pressure regulator. A pipe (2) allows the transport of gas from the helium supply source to the detection assembly (20) via the oven chamber (3). Non-schematic, mobile feeding means, driven by an endless screw using a precision stepping motor, of several stainless steel sample cups allows regular feeding, sample after sample, of the oven (3).

The regulated flow of helium introduced into the furnace chamber passes to the level of the analyzed sample during the entire duration of the measurement. The metal oven chamber is heated using 2 x 150 Watt heating resistors. The temperature is controlled using a type K miniature contact thermocouple connected to a microprocessor (4) connected to the electrical supply of the resistors. The start of the temperature cycle is controlled from the oven control microprocessor. A distributor (5) placed at the outlet of the furnace makes it possible to divide the gaseous flow of helium charged with the compounds originating from the desorption of the sample placed in the chamber of the furnace, so as to reject into the atmosphere the greatest part of the flux gas, the remainder feeding the detection assembly. In this case 20 volumes are rejected for u volume used for measurements. This operation is performed to have an optimal measurement dynamic and to avoid saturation of the system, which is always possible with samples that are too rich.

The distributor includes a heavy oil trap incorporated to prevent particles or large molecules formed during pyrolysis for example clogging the pipes. The flow at the distributor is controlled by a precision needle valve.

The detection assembly (20) comprises the burner (1) of an FID (6), a sampling line (7), connecting the flame area of the FID to the SCD detector (8), a sensor (9) consisting of an electrode and a probe impregnated with

FID, an amplifier (10) linked to the probe.

In the vicinity of the FID burner (11) is a spark gap (12) and an electrode (13) connected to a probe (14) for measuring electric current. The burned gas mixture, after having been ignited using the spark gap, is ionized using a potential difference established between the collecting electrode (13) and the metal base of the burner brought to high voltage by one of the spark gap electrodes (14) connected to said base. The temperature of the assembly is regulated so that the combustion chamber is kept at an appropriate temperature of around 300 ° C.

The current resulting in the probe, characterizing the quantity of hydrocarbons, is amplified and then transmitted to a computer system, a microcomputer for example, integrated into the processing unit (21).

The burner is supplied with flux from the furnace, supplemented with hydrogen and air. The hydrogen flow (15) is controlled using a precision flow regulator (16) so that the flow variation does not exceed one ml / minute. The flow of ai

(17) is ensured by a simple needle valve, the variations on the flow being able to reach 5ml / min. In the example of embodiment described, the hydrogen flow is 175 ml / min ⁺ lml / min for an air flow of 300 ml / min ⁺ ml / min.

A tube (7) made of ceramic (or any other insulating material) is located in the center of the collecting electrode (13) placed above the burner (11). One of its ends is located about 5mm from the burner flame. The purpose of this conduit (7) is to collect the combustion gases and bring them to a detector (8) of SO chemiluminescence, of the SCD 350 type in this case, in which the reaction with ozone takes place and the detection of sulfur compounds contained in said gases. An ea trap

(18) is placed on the pipe upstream of the SCD.

Once the sample to be analyzed has been placed inside the oven, the analysis process takes place as follows. Initially the sulfur compounds and hydr ^'ocarbonés fibers are carried by the helium flow. This first desorption phase can last approximately three minutes during which the oven is maintained at a constant base temperature which can be of the order of 250 ° C. to 300 ° C. The temperature of the oven is then continuously increased over a sufficiently long time, up to a temperature of up to 700 ° C., so that around 350 ° C. to 500 ° C. takes place the complete pyrolysis of the organic material of the 'sample and that for higher temperatures the decomposition of the mineral sulfur contained in the sample takes place, the more often in the form of pyrite.

All kinds of laws of temperature rise can agree as long as they allow the pyrolysis of organic sulfur compounds from the kerogen and the decomposition of mineral sulfur on the one hand and the establishment of a one-to-one relationship between temperature 8

and other times. The temperature rise can for example be constant, equal to 25 ° C per minute up to a temperature for example of 600 ° C which will be maintained for one to two minutes. During the temperature rise phase (350 ° C - 500 °) pyrolysis of the organic material of the rock sample takes place. The sulfur and hydrocarbon compounds then come from the kerogen of the sample. An analysis lasts a few minutes. During this period of time, the quantities of sulfur and hydrocarbons coming from the furnace are continuously measured and recorded, as a function of time, at the level of the SCD detector and of the probe connected to the FID, respectively. The curve S (t) obtained on the SCD and characterizing the sulfur comprises three peaks s ,, s ₂ , s ₃ , encountered according to increasing times and temperatures, such as those appearing in FIG. 4. These peaks make it possible to measure respectively the quantity of free sulfur and of combined sulfur contained in the volatile compounds (s ^, the quantity of organic sulfur contained in the kerogen (s ₂ ) and the quantity of mineral sulfur (s ₃ ), the data of the three making it possible to define a concept of total sulfur.

The curve H (t) obtained on the FID comprises two peaks h- _] _ and h ₂ (cf. FIG. 3), the first of these peaks making it possible to measure the quantity of free hydrocarbon products, theπnovaporisables, and the second the quantity of combined hydrocarbon products in kerogen (organic matter insoluble in organic solvents) of the sample.

If a C0 ₂ detector is also plugged into the apparatus, a curve is also obtained having two peaks O ^ and O ₂ respectively characterizing the amount of free carbon monoxide and the amount of carbon monoxide in the kerogen.

Such a device therefore makes it possible, from a single analysis on the same sample, to determine several sulfur indices IS 'calculated at the level of the treatment unit expressed in mg of sulfur S per gram of total sulfur characterizing the type of studied rock, of a hydrogen index IH 'expressed in mg of hydrocarbon products HC per gram of rock, and optionally an oxygen index 10' expressed in mg of carbon monoxide Cθ ₂ per gram of rock, the weight of the sample having been determined before its introduction into the oven.

The characteristics of the apparatus make it possible to differentiate different samples from the distribution and the value of the peaks s- ^ s ^ s- _j in particular whereas previously only the criterion of the total quantity of sulfur, not involving the differences in contribution from each of the different sources of SO ₂ in the sample had been used reliably.

The quantity of total sulfur determined by integration of the curve S using the apparatus described above was compared with the quantity of total sulfur determined by a LECO apparatus which has hitherto served as a reference for this type. measurement, and in which the determination of said quantity is done after oxidation of all the sulfur contained in the rock by combustion at very high temperature. The two results agree perfectly.

The value of the quantity of total sulfur can either be determined by integration of the curve S at the level of the treatment unit or determined by external calibration, the measurement being for example carried out on a LECO and introduced as given in the unit of treatment. The transformation of the data of the electric currents (cf. ordinate of FIGS. 3 and 4) supplied by the detectors into the quantity of sulfur requires the data of correspondence curves supplied by the manufacturers and entered as data at the level of the processing unit.

It is therefore possible, using the measured and archived data at the level of the processing unit, to calculate for example an organic sulfur index specific to the kerogen IS'2 (integration of the peak S2), a heat-soluble sulfur index IS'l ( integration of peak SI), a mineral sulfur index IS'3 (integration of peak S3). This device can be used for any application requiring the determination of different forms of sulfur, degradable at different temperatures between 100 - 250 ° C and 700 ° C. This device is particularly suitable for the analysis of different forms of sulfur in coals but also in sulphide ores in the sedimentary system: sedimentary uranium, lead, zinc in stratiform deposits with organic matter, etc. In these latter, mineralization is directly associated with organic matter. The device can also be used to characterize heavy petroleum products: distillation residues, resins and asphaltenes, as well as polymers made from sulfur, rubber for example.

Claims

1 - Device for the quantitative and qualitative analysis of the sulfur compounds contained in a rock sample characterized in that it comprises:

- means for producing a helium vector flow under pressure, - an oven, supplied with said helium flow, the temperature of which can be constantly varied up to a temperature of at least 700 ° C. to allow the thermal elution of the compounds of a sample to be analyzed placed beforehand inside the furnace chamber using means for introducing the samples to be analyzed into the furnace chamber, the flow of helium causing at the outlet of the oven, the volatile products produced by the sample up to a detection assembly,

a valve for dividing the flow from the furnace into a predetermined ratio, part of the flow being sent to the detection assembly, the other part being rejected,

a detection assembly comprising means for carrying out the combustion under a hydrogen-enriched atmosphere of the products transported by the helium flow leaving the furnace so as to transform the sulfur compounds contained in the flow essentially into SO, as well as a pipe made of electrically insulating material, ceramic for example, for conducting the burnt gases after combustion to a detector, and said linear SO detector at ch iluminescence, connected to a treatment unit, a treatment unit allowing the determination of sulfur indices and total sulfur

2 - Device according to claim 1 characterized in that it further comprises means for ionizing the gases burned by combustion and for detecting the resulting electric current characterizing the quantities of hydrocarbon products contained in the stream. 3 - Device according to claim 2 characterized in c that the combustion takes place in the flame of an ionizing flame detector.

4 - Device according to claim 1 characterized in c that the fractionation at the valve is done in u report such that 20 parts of the flow are rejected for a sent to the detection assembly.

5 - Device according to claim 1 or 4 characterized e that a part of the rejected stream is sent to u C02 detector.

6 - Device according to claim 1 characterized in c that the pipe passes through a water trap upstream of detector to SO.

7 - Device according to claim 1 characterized in c that the detection system comprises a supply of ai to maintain combustion.

8 - Device according to claim 7 characterized in c that the hydrogen flow is 175 ml / min for an air flow of 300 ml / min.

9 - Application of the device according to one of claims 1 to 8 to the analysis of sulphide ores in the sedimentary system.

10 - Application of the device according to one of claims 1 to 8 to the analysis of heavy petroleum products.