CA3080347A1 - Process for determining a composition of a hydrocarbon sample obtained from a subterranean reservoir - Google Patents

Abstract

A method for performing solvent composition in a hydrocarbon sample for a predetermined condition having a predetermined temperature and a predetermined pressure includes preparing the sample, determining a saturation pressure of the sample at the predetermined temperature, comparing the saturation pressure to the predetermined pressure to determine the saturation of the sample at the predetermined condition, and performing composition analysis on the sample based on the determined saturation of the sample at the predetermined condition.

Description

PROCESS FOR DETERMINING A COMPOSITION OF A HYDROCARBON
SAMPLE OBTAINED FROM A SUBTERRANEAN RESERVOIR
TECHNICAL FIELD
[0001] The present invention relates to determining a composition of hydrocarbon sample obtained from a subterranean reservoir.
BACKGROUND DISCUSSION

[0002] Hydrocarbon analysis procedures established by the American Society of Testing and Materials (ASTM) are typically conducted by evolving all light hydrocarbons from the liquid phase of a hydrocarbon sample. Such analysis procedures are limited in that they provide inaccurate information for total composition of hydrocarbons, particularly in C5 and lower components, and provide limited if any information regarding phase behaviour of the sample.

[0003] Improvements to methods for analyzing hydrocarbon emulsions is desired.
SUMMARY

[0004] The present disclosure provides a method for determining compositional information of a hydrocarbon sample obtained from a hydrocarbon-bearing reservoir that is based on the saturation pressure of the sample at predetermined temperature and pressure conditions. The methods set forth in the present disclosure facilitate determining the total hydrocarbon composition of the hydrocarbon sample, the phase behavior of the sample, and may provide an understanding of liquid and gas phase ratios and compositions at a given pressure and temperature condition.

[0005] In conventional analysis procedures, samples may not be representative of the actual samples hydrocarbon samples because the samples Date Recue/Date Received 2020-05-01 may include water, which may show up as a C30+ component of the sample, skewing the composition information obtained by the analysis. Further, conventional analysis procedures may not accurately determine amounts of hydrocarbon components in solution vs in the gaseous phase because analysis may not be performed an operating temperature or pressure of interest, which may provide false analysis. For example, lighter components, e.g., <C5, may be in gaseous phase during analysis but in liquid phase under the operating temperature or pressure of interest, which will skew the compositional information of the gas and liquid components.

[0006] In an aspect of the present disclosure, there is a method for performing solvent composition analysis in a hydrocarbon sample for a predetermined condition having a predetermined temperature and a predetermined pressure, the method includes preparing the sample, determining a saturation pressure of the sample at the predetermined temperature, comparing the saturation pressure to the predetermined pressure to determine the saturation of the sample at the predetermined condition, and performing composition analysis on the sample based on the determined saturation of the sample at the predetermined condition.

[0007] In another aspect of the present disclosure, the saturation at the predetermined condition is determined to be undersaturated if the saturation pressure does not exceed the predetermined pressure by more than a predetermined threshold.

[0008] In another aspect of the present disclosure, when the determined saturation at the predetermined condition is undersaturated, performing composition analysis on the sample includes performing a liquid composition analysis on the sample while maintaining the sample at the predetermined pressure and predetermined temperature to obtain compositional information of the sample.

[0009] In another aspect of the present disclosure, when the determined saturation at the predetermined condition is oversaturated, performing Date Recue/Date Received 2020-05-01 composition analysis on the sample includes performing a first liquid composition analysis on the sample while maintaining the sample at a pressure that meets or exceeds the saturation pressure to obtain total compositional information for the sample, adjusting a temperature of the sample to the predetermined temperature and the pressure of the sample to the predetermined pressure to separate the sample into a gas component and a remaining liquid component, performing a gas composition analysis on the gap component to obtain compositional information of the gas component, and performing a second liquid composition analysis on the remaining liquid component to obtain compositional information on the remaining liquid component.

[0010] In another aspect of the present disclosure, preparing the sample comprises cleaning the sample.

[0011] In another aspect of the present disclosure, the sample is an emulsion comprising water and hydrocarbons, and wherein cleaning the sample includes maintaining the sample in a sealed container while heating the sample to a temperature to cause separation of the hydrocarbon and the water in the sample, and removing the separated water from the sample, the temperature not exceeding a density inversion temperature of the emulsion.

[0012] In another aspect of the present disclosure, cleaning the sample includes adding a separation chemical to the sample.

[0013] In another aspect of the present disclosure, the separation chemical comprises an interfacial tension reducing agent, a miscible solvent, or both an interfacial tension reducing agent, a miscible solvent.

[0014] In another aspect of the present disclosure, the interfacial tension reducing agent comprises a dennulsifier, a surfactant, or both a dennulsifier and a surfactant.

[0015] In another aspect of the present disclosure, the miscible solvent comprises an alcohol, a salt, or both an alcohol and a salt.

Date Recue/Date Received 2020-05-01 BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the present application will now be described, by way of example only, with reference to the attached Figures, wherein:

[0017] FIG. 1 is a sectional view through a reservoir;

[0018] FIG. 2 is a flow chart of a method of determining solvent compositional information for a hydrocarbon sample according to an embodiment of the present disclosure;

[0019] FIG. 3 is a flow chart of a method of determining solvent compositional information for an undersaturated sample according to an embodiment of the present disclosure; and

[0020] FIG. 4 is a flow chart of a method of determining solvent compositional information for an oversaturated sample according to an embodiment of the present disclosure.
DETAILED DESCRIPTION

[0021] For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
Numerous details are set forth to provide an understanding of the examples described herein. The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein.

[0022] The disclosure generally relates to a method for determining compositional information of a hydrocarbon sample obtained from a hydrocarbon-bearing reservoir that is based on the saturation pressure of the sample at predetermined conditions. The method includes preparing the sample, determining a saturation pressure of the sample at the predetermined temperature, comparing the saturation pressure to the predetermined pressure Date Recue/Date Received 2020-05-01 to determine the saturation of the sample at the predetermined condition, and performing composition analysis on the sample based on the determined saturation of the sample at the predetermined condition.

[0023] The hydrocarbons utilized to prepare a sample for analysis according to the present disclosure are obtained from a production well drilled into a subterranean hydrocarbon-bearing formation. One example of a hydrocarbon production well 100 is illustrated in FIG. 1. The hydrocarbon production well 100 extends generally vertically from a surface 102 into the hydrocarbon-bearing reservoir 106. Surface 102 refers to the environment above the surface of the ground 103. The hydrocarbon production well may extend near the base or bottom 104 of the hydrocarbon reservoir 106.

[0024] The production well 100 may form part of a steam assisted gravity drainage (SAGD) production process. In SAGD, the production well 100 may include a generally horizontal segment (not shown) and an injection well that also includes a generally horizontal segment (not shown) is disposed generally parallel to and spaced generally vertically above the horizontal segment of the hydrocarbon production well 100. During SAGD, steam is injected into the injection well to mobilize the hydrocarbons and create a steam chamber in the reservoir 106, around and above the generally horizontal segment of the injection well. In a SAGD process, the production well 100 may produce an emulsion that includes hydrocarbons and water.

[0025] In other examples, any suitable process for recovering hydrocarbons from the reservoir via the production well 100 may be any suitable hydrocarbon recovery process. The process utilized may depend, at least in part, on the geological conditions within the reservoir 106.

[0026] Once the hydrocarbons are pumped to the surface 102 via the production well, the hydrocarbons may be transported via, for example, a pipeline (not shown). The pipeline may transport the hydrocarbons to another facility such as, for example, a storage facility or a refinery.
Date Recue/Date Received 2020-05-01

[0027] In general, compositional information of the hydrocarbons recovered from the reservoir 106 is desired. The compositional information may include, for example, the saturation of the sample under specified pressure and temperature conditions, the mole or mass fraction of various hydrocarbon constituents for the total sample, the mole or mass fraction for the various hydrocarbon constituents of the gas component and the liquid component of the hydrocarbon sample.

[0028] Determining the compositional information at a particular predetermined condition, i.e., for a predetermined temperature and a predetermined pressure may be desired. The predetermined conditions may be, for example, the conditions within the production well 100, the conditions at the surface 102, the conditions within the reservoir 106. The conditions at the surface may include, for example, conditions within piping, a pipeline, or downstream of a vessel, or any condition within a hydrocarbon processing facility.

[0029] The compositional information at a predetermined condition may be utilized, for example, to verify simulations or predictions for solubility of solvents in bitumen or other properties such as viscosity or density dependence of a particular hydrocarbon component. Further, compositional information indicating that the sample is oversaturated under reservoir conditions facilitates predicting downhole separation of liquid and gas phases, and provides information regarding gas flow through liquid pumps. Compositional information at a predetermined condition corresponding to the surface conditions may be utilized, for example, to determine surface equipment requirements based on the saturation of the sample at the surface conditions, determine surface process mass balance, or determine fluid properties of streams for surface facility operations including, for example, heat capacities for exchanger monitoring or optimization.

[0030] Previous analytic techniques are typically conducted by evolving all light hydrocarbons out of the liquid phase of a hydrocarbon sample. Such Date Recue/Date Received 2020-05-01 techniques may provide inaccurate results, particularly for the light hydrocarbon component(s) of the sample, and do not provide phase behaviour information of the sample.

[0031] Referring to FIG. 2, a method determining solvent compositional information of a hydrocarbon sample is shown.

[0032] At 202 a hydrocarbon sample is prepared from hydrocarbons recovered from a hydrocarbon reservoir, such as the reservoir 106 shown in FIG.
1. The hydrocarbons may be recovered utilizing any suitable method for recovering hydrocarbons from a hydrocarbon-bearing formation.

[0033] The sample may be prepared by placing the hydrocarbons in a sealable container that facilitates adjusting the temperature and pressure conditions within the container. The temperature of the sample may be adjustable by heating the sample through, for example, electrical heating bands located on the outside of the container or placing the container in an oven.
The pressure of the sample may be adjusted by, for example, adjusting a piston located within a piston-container or injecting an inert gas or a non-soluble liquid into the container. The inert gas or non-soluble liquid may be selected such that the contribution of the inert gas or non-soluble liquid does not affect the compositional information obtained through analysis for the hydrocarbon components of the sample.

[0034] In some examples, preparing the hydrocarbon sample at 202 may include cleaning the sample. Cleaning the sample may include removing water from the sample in cases in which the recovered hydrocarbons are an emulsion comprised of hydrocarbons and water. Emulsions may result, for example, when water is utilized in the process for recovering the hydrocarbons such as, for example, when a SAGD process is utilized.

[0035] Removing water from the emulsion sample includes heating the sample to a temperature that does not exceed a water-hydrocarbon density inversion temperature of the emulsion sample in order to cause the water and Date Recue/Date Received 2020-05-01 hydrocarbons to separate, while the emulsion sample is sealed in a container.
In addition to heating the sample, a separation chemical may optionally be added to the emulsion sample to facilitate the separation of the water from the hydrocarbons.

[0036] In an example, the separation chemical may include an interfacial tension reducing agent to improve separation of oleic and aqueous phases. Any suitable interfacial tension reducing agent may be utilized including, for example a dennulsifier such as a flocculant, a solvent that is miscible in both water and hydrocarbon phases, or a sulphonate dennulsifier.

[0037] In another example, the separation chemical may include one or both of an alcohol and a salt to increase the density differential between the oleic and aqueous phases to facilitate separation of the water from the hydrocarbons.
Any suitable alcohol may be utilized including, for example, alcohols heavier than C4 alcohols such as butanol. In general, the soluability of an alcohol in oil increases with increased length of the carbon chain of the alcohol. Any suitable salt may be utilized including, for example, sodium chloride and anhydrous sodium sulphate.

[0038] At 204, a saturation pressure, which may also be referred to as the "bubble point" of the sample, is determined at the predetermined temperature.
The determining at 204 may include adjusting the temperature of the sample to the predetermined temperature. The determining at 204 may be performed by any suitable process for determining a saturation pressure of a sample that includes a liquid and a gas.

[0039] For example, the determining at 204 may include raising a pressure of the sample within a container to a pressure at which all of the gas within the sample is forced into the liquid. This may be performed by reducing the volume the container holding the sample to increase the pressure until an inflection point in the pressure readings, observed as a more rapid increase in the measured pressure with decreased volume. The inflection point indicates that the gas component has been forced into the liquid and which inflection point is the Date Recue/Date Received 2020-05-01 saturation pressure or bubble point for the sample at the predetermined temperature. Alternatively, if the gas component is dissolved in liquid component at the outset of the determining at 204, then the volume of the container may be increased until an inflection point in the pressure readings is observed, observed as a more rapid drop in pressure with increased volume.

[0040] At 206, the saturation pressure determined at 204 is compared to the predetermined pressure to determine the saturation of the sample at the predetermined conditions. The saturation of the sample may be determined to be oversaturated at the predetermined conditions if the determined saturation pressure exceeds the predetermined pressure and may be determined to be undersaturated at the predetermined conditions if the determined saturation pressure does not exceed, or is less than, the predetermined pressure. In an example, the saturation may be determined to be undersaturated when the determined saturation pressure does not exceed the predetermined pressure by more than a threshold amount. The threshold amount may be, for example, a percentage of the determined saturation pressure. In an example, the threshold is 5% of the determined saturation pressure.

[0041] At 208, composition analysis is performed on the sample based on the saturation determination at 206 to determine compositional information for the sample. For example, the process for performing the composition analysis at 208 will depend on whether the saturation is determined at 206 to be oversaturated or undersaturated. Examples of processes based on the determined saturation that may be utilized are described in more detail below with reference to FIGS. 3 and 4.

[0042] The compositional information that is determined at 208 may depend on the composition analysis that is performed, but generally may include any or all of a composition of complete sample, a composition of a gas component of the sample, a composition of the liquid component of the sample.
The compositional information may include mole and mass percent of the hydrocarbon components of the sample or relevant portion of the sample.

Date Recue/Date Received 2020-05-01

[0043] Optionally at 210, a report is generated that includes the compositional information determined at 208. Additionally, the report optionally generated at 210 may include other information in addition to the compositional information including, for example, any of the determined saturation pressure, the predetermined temperature and pressure of the predetermined conditions, and a gas component to liquid component mass ratio.

[0044] The report that is optionally generated at 210 may be transmitted at 212. The transmitting at 212 may include automatically transmitting the report electronically in any suitable manner including, for example, utilizing a file transfer protocol (FTP) to transmit the report to a server or other computer.
Additionally, or alternatively, the transmitting at 212 may include automatically transmitting the report via email or text message.

[0045] The compositional information generated at 208 may be utilized to verify simulations or models of hydrocarbon characteristics, to determine downhole separation, or to determine downhole liquid and gas separation, and to determine surface equipment and processes to utilize, as described previously.

[0046] Referring now to FIG. 3, an example process for performing the composition analysis at 208 in the example method described above with reference to FIG. 2 is shown. The example process for performing composition analysis shown in FIG. 3 may be utilized when the saturation of the sample is determined, such as at the determining 206 described above, to be undersaturated.

[0047] At 302, the sample is determined to be undersaturated. As described above, the sample may be determined to be undersaturated if the determined saturation pressure does not exceed, or is less than, the predetermined pressure. The determination at 302 may be made when, for example, the determined saturation pressure does not exceed the predetermined pressure by more than a threshold amount. The threshold amount may be, for example, a percentage of the determined saturation pressure. In an example the threshold is 5% of the determined saturation pressure.
Date Recue/Date Received 2020-05-01

[0048] At 304, liquid composition analysis is performed on the sample while the sample is maintained at the predetermined conditions, i.e., at the predetermined temperature and the predetermined pressure. A determination at 302 that the sample is undersaturated at the predetermined conditions means that the gas in the sample is dissolved in the liquid component. Thus, the liquid composition analysis performed at 304 will provide total composition analysis for the total sample.

[0049] The liquid composition analysis may be performed utilizing any suitable process or technique for determining the composition of a liquid hydrocarbon sample. The liquid composition analysis may be an analysis process that provides the mole or mass fraction of each of hydrocarbon present in the sample. For example, the liquid composition analysis may be a C36+
composition analysis in which the mole or mass fractions of hydrocarbons Cl to C36 are determined as well as the mole or mass fraction of all of the hydrocarbons heavier than C36. Techniques that may be utilized for the liquid composition analysis may include, for example, gas chromatography or liquid chromatography (LC) which may utilize infrared spectroscopy (IR), mass spectroscopy (MS) or modulation ratio (MR).

[0050] Referring to FIG. 4, another example process for performing the composition analysis at 208 in the example method described above with reference to FIG. 2 is shown. The example process for performing composition analysis shown in FIG. 4 may be utilized when the saturation of the sample is determined, such as at the determining 206 described above, to be oversaturated.

[0051] At 402, the sample is determined to be oversaturated. As described above, the sample may be determined to be oversaturated if the determined saturation pressure exceeds the predetermined pressure. The determination at 402 may be made when, for example, the determined saturation pressure exceeds the predetermined pressure by more than a threshold amount. The threshold amount may be, for example, a percentage of the determined Date Recue/Date Received 2020-05-01 saturation pressure. In an example the threshold is 5% of the determined saturation pressure.

[0052] Because the sample being analyzed in the example process set out in FIG. 4 is oversaturated, the sample will include a gas component and a liquid component at the predetermined conditions. Thus, three separate analyses may be performed to determine the total compositional information for the total sample, as well as the compositional information of each of the gas component and the liquid component of the sample that are present at the predetermined conditions.

[0053] At 404, a first liquid composition analysis is performed while maintaining the sample at a pressure that meets or exceeds a saturation pressure to obtain the total compositional information. The saturation pressure that is met or exceeded will depend on the temperature of the sample while the first liquid composition analysis is performed. Maintaining the sample at a pressure that meets or exceeds the saturation facilitates most, if not all, of the gas component being dissolved in the sample. The first liquid composition analysis may be performed utilizing any suitable process or technique, similar to the liquid composition processes and techniques described above with reference to step 304 in FIG. 3.

[0054] At 406, the pressure, and the temperature if necessary, of the sample is adjusted to the predetermined pressure and the predetermined temperature, respectively. Adjusting the pressure and temperature of the sample to the predetermined pressure and predetermined temperature will cause an oversaturated sample to separate into a gas component and a remaining, fully saturated, liquid component.

[0055] At 408, a gas composition analysis is performed on the gas component of the sample to obtain gas compositional information for the gas component.

Date Recue/Date Received 2020-05-01

[0056] The gas composition analysis may be performed utilizing any suitable process or technique for determining the composition of a gas hydrocarbon sample. The gas composition analysis may be an analysis that provides the mole or mass fraction of each of hydrocarbon present in a gas sample. For example, the gas composition analysis may be a C11+ composition analysis in which the mole or mass fractions of hydrocarbons Cl to C11 are determined as well as the mole or mass fraction of all of the hydrocarbons heavier than C11. Generally, lighter hydrocarbons will more easily evolve out of the sample into a gas phase, while heavier hydrocarbons will be more likely to remain in the liquid phase in an oversaturated sample. Thus, separate mole or mass fractions for heavier hydrocarbons are less important in the gas composition analysis than in the liquid composition analysis described above.
Techniques that may be utilized for the gas composition analysis may include, for example, absorption spectroscopy or gas chromatography (GC) which may utilize mass spectroscopy (MS), infrared spectroscopy (IR) or modulation ratio (MR).

[0057] At 410, a second liquid composition analysis may be performed on the remaining liquid component to obtain compositional information for the remaining liquid component. The second liquid composition analysis may be performed utilizing the same process or technique as the first liquid composition analysis performed at 404, or may utilize a different process or technique.
The second liquid composition analysis may be performed utilizing any suitable process or technique, similar to the liquid composition processes and techniques described above with reference to step 304 in FIG. 3.

[0058] The present disclosure describes methods for performing composition analysis of a hydrocarbon sample based on a determined saturation of the hydrocarbon sample at predetermined conditions. By performing composition analysis based on the saturation of the hydrocarbon sample provides more accurate compositional information at the predetermined conditions by, for example, removing water from the sample prior to analysis and performing analysis at predetermined conditions. Further, additional information regarding Date Recue/Date Received 2020-05-01 the hydrocarbons under the predetermined conditions may be provided by performing composition analysis based on the determined saturation including, for example, the phase behaviour and the compositional information of the gas component and liquid component, which is not provided by conventional analysis processes.

[0059] In an example, the accuracy of mass balance determinations may be improved utilizing the compositional information determined in the present disclosure. Conventionally, mass balance determinations may include errors when a stream includes a multiphase flow by assuming that the flow is single phase flow. By knowing it is oversaturated and two phase flow, the properties of the fluid (i.e. instead of pure liquid density, knows it's a mixed flow with a ratio of gas-liquid of X, density Y and viscosity Z) may be input to the flownneter to obtain a more accurate reading. Oversaturation information may also be utilized to select the type of sensor technology to be used used. For example, instead of differential pressure (dP), switch to a mass and dP meter in series to more accurately determine gas phase flow.

[0060] The above-described embodiments are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art. The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Date Recue/Date Received 2020-05-01

Claims (10)

What is claimed is:

1. A method for performing solvent composition in a hydrocarbon sample for a predetermined condition having a predetermined temperature and a predetermined pressure, the method comprising:
preparing the sample;
determining a saturation pressure of the sample at the predetermined temperature;
comparing the saturation pressure to the predetermined pressure to determine the saturation of the sample at the predetermined condition; and performing composition analysis on the sample based on the determined saturation of the sample at the predetermined condition.

2. The method according to claim 1; wherein the saturation at the predetermined condition is determined to be undersaturated if the saturation pressure does not exceed the predetermined pressure by more than a predetermined threshold.

3. The method according to claim 1, wherein when the determined saturation at the predetermined condition is undersaturated, performing composition analysis on the sample comprises:
performing a liquid composition analysis on the sample while maintaining the sample at the predetermined pressure and predetermined temperature to obtain compositional information of the sample.

4. The method according to claim 1, wherein when the determined saturation at the predetermined condition is oversaturated, performing composition analysis on the sample comprises:
performing a first liquid composition analysis on the sample while maintaining the sample at a pressure that meets or exceeds the saturation pressure to obtain total compositional information for the sample;
adjusting a temperature of the sample to the predetermined temperature and the pressure of the sample to the predetermined pressure to separate the sample into a gas component and a remaining liquid component;
performing a gas composition analysis on the gap component to obtain compositional information of the gas component; and performing a second liquid composition analysis on the remaining liquid component to obtain compositional information on the remaining liquid component.

5. The method according to claim 1, wherein preparing the sample comprises cleaning the sample.

6. The method according to claim 5, wherein the sample is an emulsion comprising water and hydrocarbons, and wherein cleaning the sample comprises:
maintaining the sample in a sealed container while:
heating the sample to a temperature to cause separation of the hydrocarbon and the water in the sample, the temperature not exceeding a density inversion temperature of the emulsion; and removing the separated water from the sample.

7. The method according to claim 6, wherein cleaning the sample comprises adding a separation chemical to the sample.

8. The method according to claim 7, wherein the separation chemical comprises an interfacial tension reducing agent, a miscible solvent, or both an interfacial tension reducing agent, a miscible solvent.

9. The method according to claim 8, wherein the interfacial tension reducing agent comprises a demulsifier, a surfactant, or both a demulsifier and a surfactant.

10. The method according to claim 8, wherein the miscible solvent comprises an alcohol, a salt, or both an alcohol and a salt.