Sensor for the subsurface oil and gas exploration

Abstract

Apparatus, systems and methods for soil gas sampling are disclosed. The apparatus may include a first outer surface formed from a rigid liquid-impermeable and gas-impermeable material, and a second outer surface formed from an aquaphobic and gas-permeable membrane, where an edge of the second outer surface is attached to the first edge of the first surface, the first outer surface and the second outer surface entirely enclose an inner volume, and the second outer surface comprises a high specific surface area surface. The apparatus may further include a quantity of porous absorbing material, at least partially filling the inner volume, configured to preferentially absorb gaseous analytes.

Description

SENSOR FOR THE SUBSURFACE OIL AND GAS EXPLORATIONBACKGROUND

[0001] In the petroleum industry, hydrocarbons are located in reservoirs far beneath the surface of the Earth. Wells are drilled into these reservoirs to access and produce hydrocarbons. In some cases, hydrocarbons can migrate to the surface, for example through faults or fractures. Hydrocarbon seepages are a natural phenomenon that occurs as a surface expression of this vertical migration. A hydrocarbon macroseepage occurs when there is a large concentration of hydrocarbons easily detectable at the surface. In comparison, a hydrocarbon microseepage occurs when there are ultra-low trace levels of analytically detectable hydrocarbons in soils, sediments, or waters. Geochemical prospecting for hydrocarbons includes searching for surface or near surface hydrocarbons and their alteration products, which may guide the discovery of oil and gas accumulations from an underlying reservoir.

[0002] Conventional geochemical exploration techniques include soil sampling. Soil sampling occurs both directly by collecting a physical sample of the surface or near surface soil, or indirectly by detecting seepage-induced changes to the soil, sediment, microbes or vegetation. Once collected, these soil samples are often delivered to a laboratory for processing and analysis to determine a hydrocarbon microseepage. However, due to the low concentration in a microseepage, detection is more difficult and requires sensitive analytical instruments for accurate measurement. Hydrocarbon microseepage is also often hindered by contamination issues including anthropogenic industrial signal, recent organic matter signal, and soil sediment background signal. Improvements in geochemical prospecting techniques may aid in hydrocarbon exploration as well as soil and groundwater contamination prevention.SUMMARY

[0003] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In general, in one aspect, embodiments relate to an apparatus for soil gas sampling. The apparatus may include a first outer surface formed from a rigid liquid- impermeable and gas-impermeable material, and a second outer surface formed from an aquaphobic and gas-permeable membrane, where an edge of the second outer surface is attached to the first edge of the first surface, the first outer surface and the second outer surface entirely enclose an inner volume, and the second outer surface comprises a high specific surface area surface. The apparatus may further include a quantity of porous absorbing material, at least partially filling the inner volume, configured to preferentially absorb gaseous analytes.

[0005] In general, in one aspect, embodiments relate to a system for collecting a soil gas sample. The system includes a soil gas sampler, a quantity of porous absorbing material, and an autonomous soil gas sampler deployment vehicle. The soil gas sampler includes a first outer surface formed from a rigid liquid-impermeable and gas-impermeable material, and a second outer surface formed from an aquaphobic and gas-permeable membrane, where an edge of the second outer surface is attached to the first edge of the first surface; the first outer surface and the second outer surface entirely enclose an inner volume; and where the second outer surface comprises a high specific surface area surface. The quantity of porous absorbing material is disposed to at least partially fill the inner volume and configured to preferentially absorb gaseous analytes. The autonomous soil gas sampler deployment vehicle, configured to insert the soil gas sampler into a borehole at a beginning of a sampling time duration, seal, using a sealing cap, the borehole containing the inserted soil gas sampler, unseal the borehole at an end of the sampling time duration, and retrieve the soil gas sampler from the borehole.

[0006] In general, in one aspect, embodiments relate to a method of soil gas sampling. The method includes inserting a soil gas sampler into a borehole at a beginning of a sampling time duration, where the soil gas sampler includes a first outer surface formed from a rigid liquid-impermeable and gas-impermeable material, and a second outer surface formed from an aquaphobic and gas-permeable membrane, and where an edge of the second outer surface is attached to the first edge of the first surface, the first outer surface and the second outer surface entirely enclose an inner volume; and where the second outer surface comprises a high specific surface area surface and aquantity of porous absorbing material, at least partially filling the inner volume, is configured to preferentially absorb gaseous analytes. The method further includes sealing, using a sealing cap, the borehole containing the inserted soil gas sampler, unsealing the borehole at an end of the sampling time duration; and retrieving the soil gas sampler from the borehole.

[0007] In general, in one aspect, embodiments disclosed herein relate to

[0008] In general, in one aspect, embodiments relate to a

[0009] Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.BRIEF DESCRIPTION OF DRAWINGS

[0010] Specific embodiments disclosed herein will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. Like elements may not be labeled in all figures for the sake of simplicity.

[0011] FIG. 1 depicts a hydrocarbon microseepage and a deployed soil gas sampling system in accordance with one or more embodiments.

[0012] FIG. 2 depicts a soil gas sampling system in accordance with one or more embodiments.

[0013] FIGs. 3 A - 3C depict high specific area surfaces in accordance with one or more embodiments.

[0014] FIGs. 4A - 4C depict autonomous airborne vehicles for various stages of the deployment and use of a soil gas sampling system in accordance with one or more embodiments.

[0015] FIG. 5 depicts a dual soil sample analysis system in accordance with one or more embodiments.

[0016] FIG. 6 shows a flowchart in accordance with one or more embodiments.

[0017] FIG. 7 depicts a drilling system in accordance with one or more embodiments.DETAILED DESCRIPTION

[0018] In the following detailed description of embodiments of the disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0019] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as an adjective for an element (i.e., any noun in the application). The use of ordinal numbers is not to imply or create any particular ordering of the elements nor to limit any element to being only a single element unless expressly disclosed, such as using the terms "before", "after", "single", and other such terminology. Rather, the use of ordinal numbers is to distinguish between the elements. By way of an example, a first element is distinct from a second element, and the first element may encompass more than one element and succeed (or precede) the second element in an ordering of elements.

[0020] In the following description of FIGs. 1 -7, any component described with regard to a figure, in various embodiments disclosed herein, may be equivalent to one or more like-named components described with regard to any other figure. For brevity, descriptions of these components will not be repeated with regard to each figure. Thus, each and every embodiment of the components of each figure is incorporated by reference and assumed to be optionally present within every other figure having one or more like-named components. Additionally, in accordance with various embodiments disclosed herein, any description of the components of a figure is to be interpreted as an optional embodiment which may be implemented in addition to, in conjunction with, or in place of the embodiments described with regard to a corresponding like-named component in any other figure.

[0021] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a soil gas sampler” includes reference to one or more of such samplers.

[0022] Terms such as “approximately,” “substantially,” etc., mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0023] It is to be understood that one or more of the steps shown in the flowcharts may be omitted, repeated, and / or performed in a different order than the order shown. Accordingly, the scope disclosed herein should not be considered limited to the specific arrangement of steps shown in the flowcharts.

[0024] Although multiple dependent claims are not introduced, it would be apparent to one of ordinary skill that the subject matter of the dependent claims of one or more embodiments may be combined with other dependent claims.

[0025] Embodiments disclosed herein include methods and systems for collecting a soil gas sample from a borehole in order to determine the presence of a hydrocarbon microseepage. As used herein, the term “borehole” refers to a shallow borehole typically a few feet to a few tens of feet in depth drilled for the purpose of collecting a dual soil sample. In contrast, the term “wellbore” as used herein refers to a wellbore drilled to produce hydrocarbons, such as oil and gas, drilled to penetrate a hydrocarbon reservoir typically at a depth of a few thousand to a few tens of thousands of feet below the surface of the earth. The soil gas sampler includes an outside surface at least partially covered in a gas-permeable aquaphobic membrane that allows a passage of the soil gas sample, and a gas trapping sorbent material that partially fills the soil gas sampler. The gas-permeable aquaphobic membrane may be a “high specific area surface”. As used herein, a high specific area surface refers to a surface that when measured at high resolution has a larger surface area than when measured at low resolution. For example, a corrugated, folded or dimpled surface may be a high specific area surface while, in contrast a plane, that has the same area irrespective of the resolution with which it is measured, is not a high specific area surface.

[0026] The soil gas sampler may be deployed in a section of the borehole and the borehole may be sealed near the surface with a sealing cap. The sealing cap may include a radio frequency identification (“RFID”) tag to provide information about the soil gas sampler and sampling. The soil gas sampler remains in the borehole for a sampling period before being retrieved at the surface for analysis of the contents. Thesoil gas sampler may be deployed and retrieved by an autonomous vehicle at the beginning and end of the sampling period. Further the autonomous vehicle may drill the borehole prior to deploying the sampler.

[0027] In some embodiments, the chromatogram of a soil gas sample taken from a location affected by a microseepage may differ chromatogram of a sample taken from a location unaffected by a microseepage. Soil gas samples may be analyzed alone or in conjunction with other data such as soil samples to determine a presence of a hydrocarbon microseepage. The analysis may include the use of trained machine learning networks that may have been trained using a collection of known chromatography data from the vicinity of a hydrocarbon producing well and the vicinity of a dry well. In some embodiments, the training dataset may be used to form a first discriminant function to define a characteristic hydrocarbon microseepage signature and a second discriminant function to define a characteristic background signature, using a machine learning (ML) network.

[0028] A reservoir model may be generated, revised or updated using a reservoir modeler, based at least in part, on hydrocarbon microseepage detected using soil gas sample data Further, a reservoir simulation may be performed using a reservoir simulator to supplement the detected microseepages to determine a drilling target based on the reservoir model. A wellbore path, or trajectory may then be planned, using a wellbore path planning system, to intersect the drilling target and a wellbore is drilled guided by the wellbore path using a drilling system.

[0029] FIG. 1 depicts a hydrocarbon microseepage system (100) in accordance with one or more embodiments. The hydrocarbon microseepage system (100) includes an underlying reservoir (102) that contains an accumulation of hydrocarbons including oil and / or natural gas. The reservoir (102) is usually a permeable and porous rock layer, overlain by an impermeable layer or layers of rock, known as a hydrocarbon seal (104) or cap rock that, combined with an appropriate structure, such as an anticline or pinch-out, traps the accumulation of hydrocarbons within the reservoir (102). A hydrocarbon seepage may occur where the seal (104) is broken by a defect, such as at a geological fault (110), herein simply a “fault”, or fracture in the seal (104) allowing a natural vertical or steeply inclined migration of at least a portion of thehydrocarbons from the reservoir (102) to a location (108) at or near the surface of the earth.

[0030] A hydrocarbon macroseepage refers to visible oil and gas seeps found at a surface location. Macroseeps have large concentrations of hydrocarbons and are usually localized near the surface expression of faults (110), fractures, and outcropping unconformities or carrier beds. Due to their easy detectability, the discovery of new macroseeps is rare, most having previously discovered.

[0031] Hydrocarbon microseepages (106), in contrast, are both more common and more difficult to detect because of their subtler expression. Depicted in FIG. 1, a hydrocarbon microseepage (106) is characterized by a low concentration of hydrocarbons in soils, sediments, or waters, only detectable by the appropriate sensors and analysis, that result from a vertical migration of smaller amounts of hydrocarbons from the reservoir (102). The microseepage hydrocarbons may contain volatile or semi -volatile compounds. In these cases of seepage, the hydrocarbons migrate vertically through faults (110) or fractures upwards through overlying rock layers (116) towards a surface or near surface location (108). The fault (110) depicted in FIG. 1, fractures and displaces the hydrocarbon seal (104) allowing for the escape of the hydrocarbons in these cases. Microseepage (106) may also occur as vertical or near- vertical migration from the reservoir (102) due to a buoyancy-driven flow of hydrocarbons.

[0032] Geochemical prospecting for a hydrocarbon microseepage (106) facilitates the discovery of oil and gas accumulations from the underlying reservoir (102) and is usually carried out by soil sampling. Furthermore, detection of a hydrocarbon microseepage (106) may be pertinent in soil or groundwater contamination prevention. In some embodiments, geochemical prospecting may include searching for the presence of surface or near-surface hydrocarbons and their alteration products at levels detectable by the appropriate sensors. Geochemical prospecting includes a wide array of techniques ranging from directly detecting hydrocarbons that have escaped their subsurface accumulations, to identifying secondary responses in the soils, rocks, and microorganisms. Soil sampling may occur both directly by collecting a physical sample of the surface or near surface soil, or indirectly by detecting seepage-induced changes to the soil over time.

[0033] FIG. 1 depicts geochemical prospecting on a hydrocarbon microseepage system (100) by soil sampling. One or more boreholes (112), typically shallow boreholes with a depth of 6 - 20 feet (~ 2 - 7 meters) may be drilled in an area of suspected hydrocarbon microseepage (106) in order to detect and quantify the hydrocarbons through various geochemical exploration methods. Geochemical exploration methods may include soil gas samplers (114) disposed in a section of the borehole (112) to remain stationary for a period of time, trapping a soil gas sample. After the period of time has elapsed, often two weeks or more, the soil gas samplers (114) may be recovered to the surface for analysis. The soil gas samplers (114) may sample gas present in the borehole, including hydrocarbon gases. Once collected, a soil gas sample may be sent to an offsite location, such as a laboratory, for analysis. In the analysis, a detailed chemical profiling of organic compounds may be performed to determine the presence of a hydrocarbon microseepage (106).

[0034] Soil gas samples are often hindered by contaminants from anthropogenic factors that may include pollutants from agricultural activities, equipment lubricant leakage, chemical waste dumping, mining activities and industrial activities. Due to the low hydrocarbon concentration in a microseepage (106) coupled with frequent contamination from anthropogenic factors, the presence of recent organic matter, and soil sediment background noise, the accurate detection of a hydrocarbon microseepage (106) is challenging. Improvements in geochemical prospecting techniques, such as the embodiments disclosed herein, aids in accurate and robust microseepage detection, that in turn, facilitates hydrocarbon exploration.

[0035] FIG. 2 depict a soil gas sampling system (200) deployed in a borehole (202), in accordance with one or more embodiments. The soil gas sampling system (200) includes a soil gas sampler (204) disposed in a borehole (202) a few feet below the surface of the earth (206). In some embodiments the borehole (202) may be cased, i.e., lined with a water-proof cylinder constructed from a material such as steel, aluminum, or PVC. In other embodiments the borehole may be uncased. In any case, at least the base of the borehole (208) is uncased to permit the seepage of gas from the soil into the borehole (202).

[0036] In some embodiments, the borehole (202) may be drilled with water-based mud or lubricated with a bio-based oil. Bio-based oils are lubricants derived from plantand vegetable oils that are engineered for hydraulic system operations and are certified for biodegradability and non-toxicity if leaked to the soil or the borehole (202). Importantly, in this context, biobased oils have chemical signatures that differ from the chemical signatures of hydrocarbon derived oils. Due to the low hydrocarbon concentration found in soil samples containing a microseepage (106), the conventional use of petroleum-based lubricants during drilling and casing operations may contaminate the soil samples by creating a false-positive microseepage signature. False-positive results may be detected because petroleum-based lubricants may have a similar chemical composition to a natural microseepage (106). Bio-based oils may also be used to lubricate the drilling equipment involved, such as motors, joints and swivels. Thus, by using water-based muds or bio-based lubricants having a chemical composition easily distinguishable from a natural hydrocarbon microseepage (106), a petroleum contamination is greatly reduced or eliminated.

[0037] The depth of the borehole (202) may vary depending on geological settings. Factors controlling the depth of the borehole (202) may include the depth of bedrock, soil conditions including clay content, as well as economic constraints that may limit the ability to drill a deeper borehole. However, shallow boreholes drilled to a depth of 6 feet (~2 meters) or less may be too close to the ground surface and thus, be heavily contaminated by anthropogenic factors present in shallow soils or sediments.

[0038] The soil gas sampler (204) itself may be constructed from a first outer surface (210) constructed from a water- and gas-impermeable material such as, without limitation, glass, metals, alloys, alumina foils, high-density polyethylene / polypropylene, and other rigid water- and gas-impermeable polymers. These example materials are provided solely for the purpose of illustration and should not be interpreted as limiting the scope of the invention. The soil gas sampler (204) may also be formed with a second outer surface (212) that attaches to the first outer surface (210) at a common edge (214) to define a fully enclosed inner volume (216) for the soil gas sampler (204). In some embodiments the first outer surface (210) may be convex with regard to a first direction (218). When deployed in the borehole (202) first direction (208) may be vertically downward or may be parallel to the borehole in the direction of increasing depth. In some embodiments the second outer surface(212), or a spatially smoothed approximation to the second outer surface, may be convex with regard to a first direction (218).

[0039] The second outer surface (214) may be constructed from one material or a mixture of materials including, without limitation, engineered hydrophobic fluorinated and non-fluorinated oligomers and polymers. Hydrophobic fluorinated polymers for membrane fabrication may include, without limitation, polyvinylidene difluoride (PVDF), polychlorotrifluoroethylene (PCTFE), polytetrafluoroethylene (PTFE), poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy- 1 ,3-dioxole) (P(TTD-TFE)), perfluoro(methyl vinyl ether) polymer (PMVE), among others.

[0040] Alternatively, the membrane may be fabricated from hydrophobic co-polymers of perfluoropolymers, such as copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl- 1,3 -dioxole) (FDD), copolymers of tetrafluoroethylene and perfluoro(alkyl vinyl ether) (PF A), copolymers of hexafluoropropylene and tetrafluoroethylene (FEP), copolymers of tetrafluoroethylene (TFE) and perfluoro- 2,2-dimethyl dioxole (PDD), copolymers of TFE and 2,2,4-trifluoro-5- trifluoromethoxy-1,3 dioxole, and others.

[0041] Furthermore, the membrane could be fabricated from hydrophobic polymers, such as polyamides, polyimides, polyacetylenes, polycarbonates, polyarylates, poly(phenylene oxide)s, poly(ethylene oxides), polyanilines, polysulfones, polypyrrolones, polyesters, polyolefins, polyvinylchlorides (PVC), polyacrylonitrile, polyethersulphones, poly-ether-ether-ketone (PEEK), polystyrenes and combinations of polymers and co-polymers of abovementioned monomers and oligomers.

[0042] The gas-permeable aquaphobic membrane may selectively allow for a passage of the soil gas sample through the membrane and into the inner volume (216) where a gas trapping sorbent material, partially or wholly filling the inner volume (216) may trap the soil gas sample. In some embodiments, the rate at which soil gases may penetrate the gas-permeable aquaphobic membrane may be greater when the surface area of the gas-permeable aquaphobic membrane is greater than when the surface area of the gas-permeable aquaphobic membrane is smaller. To facilitate this passage in may be advantageous for the membrane to be configured to exhibit a high specific area surface. As used herein, a high specific area surface refers to a surface that whenmeasured at high resolution has a larger surface area than when measured at low resolution. For example, a corrugated, folded or dimpled surface may be a high specific area surface while, in contrast a plane, that has the same area irrespective of the resolution with which it is measured, is not a high specific area surface. Examples of such surfaces are displayed in FIGs 3A - 3C and discussed in the description thereof.

[0043] The inner volume (216) may be filled or partially filled by a sorbent material intended to trap soil gas that has passed through the gas-permeable aquaphobic membrane forming the second outer surface (212). The sorbent material, or a mixture of materials may trap the soil gas through absorption, adsorption or both.

[0044] Sorbents may be natural organic, natural inorganic, synthetic or a combination of those materials. The sorbents may be selected for their advantageous adsorption of hydrocarbons capabilities and may, without limitation, activated carbons (AC) based on carbonized natural materials, such as AC obtained from pyrolysis of peat followed by chemical activation with potassium hydroxide and sulfuric acid; AC obtained from fruit seeds and nut shells via carbonization in carbon dioxide at 400 - 900 degrees C followed by steam-gas activation; AC obtained by steam-gas activation of carbonized fruit seeds modified with polymerizing additives; anthracite-based steam-activated carbon; AC obtained from coal-peat by steam activation; AC obtained from pyrolysis of birch wood with consequent thermochemical activation with potassium hydroxide; steam-activated mesoporous carbon. The sorbents could include carbon nanomaterials such as carbon nanotubes, exfoliated carbon and mesoporous carbon materials.

[0045] The sorbents may also include porous organic polymers such as hyper crosslinked polystyrenes, polynorbomenes, covalent organic frameworks, and others. The sorbents could include zeolites such as zeolites NaX, 13X, zeolitic imidazolium frameworks, metal-organic frameworks, and others. The sorbents could include commercial sorbent materials, such as Tenax AT, Tenax GR, Chromosorb 106, Carbopack X, Anasorb, and others. The sorbents could include blends and combinations of the above-mentioned porous materials.

[0046] The design the first outer surface (210) soil gas sampler (220) may preferentially trap soil gas under the convex upwards or “dome” allowing for the equilibration adsorption of the soil gas. The first outer surface and a spatially smoothed approximation to the second outer surface may be convex with respect to a first axis (218). In addition, the design the second outer surface (212) provides an increased high surface area that may allow for a faster and more efficient absorption of the soil gas sample.

[0047] In accordance with one or more embodiments, the soil gas sampling system (200) may include a sealing cap (220) configured to seal the borehole (202) at or near, the surface of the earth (206). The sealing cap (220) may serve to protect the borehole (202) and the soil gas sampler (204) from contaminant, such as rainwater and other natural or anthropomorphic liquids or gases. The sealing cap (220) may be connected to the soil gas sampler (204) by a cable (222). The cable (222) may serve to suspend the soil gas sampler (204) at a desired depth within the borehole (202) and as a means of retrieval at the end of the sampling period. In addition, the cable (222) may form a communications channel between the soil gas sampler and the sealing cap (220).

[0048] The sealing cap (220) may include an RFID tag (224) that may include information relating to the soil gas sampler (204). Such information may include, without limitation a unique identifying number, a date and time of deployment, spatial coordinates of the deployment and design version numbers. The RFID tag may also contain additional information regarding depth of the sensor burying and temperature the sensor is exposed to and external humidity level.

[0049] FIG. 3 A depicts three examples of one-dimensional (“ID”) surfaces of varying specific area. Although second outer surface (212) of the soil gas sampler would typically not be a ID surface, nevertheless FIG. 3 A serves to illustrate relevant concepts. Note that the ID equivalent of a surface area is a length. Surface (302) exhibits a low specific area, i.e., its area is the same no matter what the resolution used to measure it. In contrast, surface (304), although it may have a measured surface area equal to that of surface (302) when measured at a coarse resolution, may have a measured surface area large than the surface area of surface (302) when measured using a higher resolution. Similarly, when measured at a coarse resolution, surface (306) may have a measured surface area equal to surface (302) or surface (304) whenmeasured at a coarse resolution. However, when measured at a fine resolution surface (306) may have a measured surface area larger than the surface measured area of surface (302) and surface (304). Surface (306) maybe said to be a high specific area surface. FIG. 3B depicts an example of a high specific area surface (310) in two- dimensions (“2D”). Surface (310) includes a planar portion (312) and a plurality of cylindrical extrusions.

[0050] FIG. 3C depicts another example of a high specific area surface (312). Surface (312) includes a planar portion (314) and a plurality of cylindrical protrusions, such as cylindrical extrusion (316), protruding from the planar portion (314). The combined surface area of the cylindrical protrusions (316) and the planar portion (312) may be much greater than the planar portion alone.

[0051] To acquire soil gas samples the soil gas sampler must be deployed in a borehole, such as borehole (202). In some embodiments, deployment may be performed manually, for example with a manual auger or a mechanical auger operated manually. In other embodiments, it may be more convenient, efficient and cost-effective to deploy the soil gas sampler using an autonomous vehicle (“AV”), as illustrated in FIGs. 4A-4C. In some embodiments the AV may be a terrestrial AV, such as AV (402), while in other embodiments the AV may be airborne, such as AV (404). An AV may be used in many phases of the soil gas sampling process. For example, the AV may be used in surveying and determining the locations for sampling (not shown). Further an AV, such as AV (402) or (404) may be used to drill the borehole (202) prior to deploying the soil gas sampler.

[0052] In some embodiments, an AV such as AV (406) may be used to insert the soil gas sampler (204) into the borehole (202) and / or to recover the soil gas sampler after the end of the sampling period. In some embodiments, an AV (408) may be used to read the information from an RFID tag (224) before, during, or after the sampling period using an interrogation unit (410) mounted on the AV (408). In some embodiments, different AV, of the same or different designs, maybe used for each of these tasks, while in other embodiments the same AV or the same design of AV may be used for two or more of the tasks illustrated in FlGs. 4A-4C. The date and time of the sensor placement and retraction as well as coordinates and depth of the sensor placement may be collected from RFID. In addition, environmental conditions, suchas temperature and humidity experienced by the soil gas sampler during deployment may be recorded and collected form the RFID.

[0053] The soil gas sample recovered after the sampling interval may be sent to a laboratory for analysis. The soil gas sample may be analyzed independently or in conjunction with other samples, such as soil samples. FIG. 5 depicts a dual soil sample processing system (500) capable of analyzing soil gas samples and soil samples in accordance with one or more embodiments. A person of ordinary skill in the art will readily appreciate the modifications to the sample processing system (500) required to analyze soil gas samples alone. The soil gas sample may be sent to the sample processing system (500) after collection, for a detailed analysis. During analysis the components or “analytes” of the soil gas may be determined and detected analytes symptomatic of a hydrocarbon microseepage may be used to determine the presence or absence of such a microseepage. The dual soil sample (508) may be analyzed using the dual soil sample processing system (500) to determine a presence of known hydrocarbons and other unknown hydrocarbon derivative compounds that may identify a hydrocarbon microseepage. During the first phase of analysis, both sample types may go through an extraction step to isolate the organic compounds including hydrocarbons, from the remainder of the sample.

[0054] The dual soil sample processing system (500) may include a thermal desorber (502), configured to extract a desorbed soil gas (504) from the soil gas sample (516). The extracted sorbents from the soil gas sampler (204) may be placed inside the thermal desorber (302), where they are subjected to high temperatures which release soil gas hydrocarbons from the sorbent material holding the soil gas sample (516) into a vapor phase, referred to as desorbed soil gas (504). In some embodiments, the temperature inside the thermal desorber (502) may range from 50 - 300° Celsius (C). In some embodiments, the thermal desorber (502) may be directly connected to a triple-quadruple mass spectrometer (GC-MS-QQQ) (506) configured to determine the analysis of a dual soil sample (308). In some embodiments, a time-of-flight mass spectrometer (GCxGC-ToFMS) may alternatively be used to perform the analysis.

[0055] The soil sample (510) may be prepared for analysis through a solvent extraction process. The soil sample (510) may be placed inside a liquid extraction device (310) configured to create a liquid soil extract in accordance with one or more embodiments.Solvent extraction, or the release of all organic compounds in the soil sediments to the liquid phase, may be achieved by subjecting the soil sample (510) to a high pressure and temperature. The liquid extraction device (520) may be any type of liquid extraction device including a Soxhlet extractor, an accelerated solvent extractor (ASE) and a microwave-assisted extraction (MAE) device. Any device or technique capable of generating a liquid soil extract from the soil sample (510) may be used without departing from the scope of the method.

[0056] The soil sample (510) may be placed inside one or more sample vessels included in the liquid extraction device (520) and the sample vessels may be flushed with organic extraction solvents prior to extraction. The recovered liquid after extraction, or the liquid soil extract may contain all organic compounds, including hydrocarbons from a microseepage. The solvents used for flushing may include a combination of dichloromethane, pentane, iso-pentane, hexane, iso-hexane, octane, iso-octane, benzene, toluene, methanol, carbon-disulfide and chloroform. In some embodiments, the liquid soil extract may then be further concentrated by evaporating the extraction solvents down to approximately 1-2 milliliters (ml). The liquid soil extract may be transferred to the GC-MS-QQQ (306) or GCxGC-ToFMS for analysis manually through wet chemistry handling and pipetting. In some embodiments, the transfer may be accomplished through automated robotic arms used for liquid handling.

[0057] The liquid soil extract from the soil sample (510) and the desorbed soil gas (504), may each be analyzed via two techniques, including GC-MS-QQQ (306) and / or GCxGC-ToFMS. Gas chromatography is an analytical technique used to separate the chemical components of a sample mixture and then detect targeted compounds and their quantities. Gas chromatography produces a graph called a chromatogram, that shows the patterns and distribution of the identified compounds from the liquid soil extract and the desorbed soil gas (504). Chromatograms present a series of peaks each of which indicates a chemical compound having a specific chemical structure. The GC-MS-QQQ (506) and GCxGC-ToFMS provide sensitive detection of hydrocarbons at ultra-low concentrations (for example, at femtogram-level detection) and have superior selectivity for resolving many compounds in complex matrices such as the liquid soil extract and desorbed soil gas (504). These soil extracts are analyzed for targeted compounds indicative of natural microseepage, which includesaturated and aromatic hydrocarbons, polar nitrogen, sulfur, oxygen (NSO) heterocyclic and NSO-derivatives of hydrocarbon compounds, and asphaltenes (and all of their biologically altered counterparts like organic acids and aldehydes). Other known compounds may be measured, which undergo untargeted mass spectra analysis to determine their identity via multiple reaction monitoring and full-scan time of flight mass spectra analysis.

[0058] The GC-MS-QQQ (306) or GCxGC-ToFMS are each capable of producing a chromatogram which may be processed and interpreted to determine a hydrocarbon microseepage and either may be used in the method described herein. A first chromatogram is produced from the liquid soil extract originating from the soil sample (510) and a second chromatogram is produced from the desorbed soil gas (504) originating from the soil gas sample (204). The first and second chromatograms may be displayed, processed, and interpreted using a data processing module (512).

[0059] In some embodiments, the hydrocarbon microseepage determined from the soil gas sampling method, in conjunction with the soil sampling method or alone, may be used by a reservoir modeler, to generate a reservoir model based, at least in part, on the hydrocarbon microseepage determined from the dual soil sample processing systemS). The reservoir modeler may combine the determined hydrocarbon microseepage information, which includes information relating to the presence and quantities of determined hydrocarbons, with other information relating to the reservoir formation obtained from well logs and geological models to create a reservoir model. In some embodiments, a reservoir model may alternatively be created by georeferencing the determined hydrocarbon microseepage to assign a subsurface location of the reservoir from which the hydrocarbon microseepage originated. In these embodiments, two dimensional (2D) maps of the microseepage concentration over the area of interest may be created and overlaid with other geophysical and geological data to infer the seeping reservoir and hydrocarbon accumulations in the subsurface. The reservoir model may include the location of the hydrocarbon reservoir, a location and concentration of the determined microseepage, and a geological map that contains mapped fault structures used to infer a path that hydrocarbon has migrated from the reservoir.

[0060] FIG. 6 shows a flowchart (600) in accordance with one or more embodiments. Initially, in Step 602, a soil gas sampler may be inserted into a borehole at a beginning of a sampling time duration. The soil gas sampler may include a first outer surface formed from a rigid liquid-impermeable and gas-impermeable material. The first outer surface may have a first edge that may form a circle. The soil gas sampler may also include a second outer surface formed from an aquaphobic and gas-permeable membrane. The edge of the second surface may be attached to the first edge of the first surface to entirely enclose an inner volume. The second outer surface may be a high specific surface area surface. A quantity of porous absorbing material may, at least partially, fill the inner volume and may be configured to preferentially absorb gaseous analytes.

[0061] In some embodiments, the soil gas sampler may be inserted using an autonomous soil gas sampler deployment vehicle. In some embodiments, the autonomous soil gas sampler deployment vehicle may be an autonomous airborne vehicle. In other embodiments, inserting the soil gas sampler may further include drilling, using the autonomous soil gas sampler deployment vehicle, the borehole prior to inserting the soil gas sampler.

[0062] In Step 604, in accordance with one or more embodiments, a sealing cap may be used to seal the borehole containing the inserted soil gas sampler. The sealing cap may include a radio-frequency identification (RFID) tag, configured to transmit information from the soil gas sampler to an interrogation unit (410). In some embodiments, the interrogation unit (410) is mounted on the autonomous soil gas sampler deployment vehicle (408).

[0063] In Step 606, in accordance with one or more embodiments, the borehole may be unsealed at an end of the sampling time duration.

[0064] In Step 608, in accordance with one or more embodiments, the soil gas sampler may be retrieved from the borehole.

[0065] FIG. 7 depicts a drilling system (700) in accordance with one or more embodiments. As shown in FIG. 7 a wellbore path (702) may be drilled by a drill bit (704) attached by a drillstring (706) to a drill rig (716) located on the surface of the Earth (708). The well may traverse a plurality of overburden layers (710) and one ormore cap-rock layers (712) to a drilling target (720) within a hydrocarbon reservoir (714). The wellbore path (702) may be a curved well path, or a straight well path. All or part of the wellbore path (702) may be vertical, and some well paths may be deviated or have horizontal sections.

[0066] Prior to the commencement of drilling, the presence of a hydrocarbon microseepage (724) may be determined from the soil gas sampling method. Further a drilling target (720) may be determined base, at least in part, on the determined microseepage (724). A reservoir model (730) may be generated, using a reservoir modeler (722) based, at least in part, on the hydrocarbon microseepage. In some embodiments, a reservoir modeler (722) comprises functionality for simulating the flow of fluids, including hydrocarbon fluids such as oil and gas, through a formation composed of porous, permeable reservoir rocks. The reservoir modeler (722) may combine information determined from any available well logs (726), the hydrocarbon microseepage (724) determined from the dual soil sampling method and any other geological models (728) available to build models of the reservoir. Well logs (726) may provide depth measurements of a well that describe such reservoir characteristics as formation porosity, formation permeability, resistivity, water saturation, and the like. A geologic model (728) is a spatial representation of the distribution of sediments and rocks (rock types) in the subsurface. The reservoir models (730) may include information regarding total hydrocarbon in place, where the hydrocarbons are located, and how effectively the hydrocarbons can potentially flow.

[0067] A reservoir simulation may be performed using a reservoir simulator (732) to determine a drilling target (720) based, at least in part, on the reservoir model (730). A reservoir simulation may be used to predict the behavior of rocks and fluid under various hydrocarbon recovery scenarios, allowing reservoir engineers to understand which recovery options offer the most advantageous hydrocarbon recovery plan for a given reservoir (714). A drilling target (720), or a chosen location to penetrate the hydrocarbon reservoir (714), may be determined through reservoir simulation by estimating the fluid flow within the reservoir (714) given various drilling target scenarios.

[0068] The reservoir simulator (732) may include hardware and / or software with functionality for performing one or more reservoir simulations regarding determiningthe drilling target (720) in the reservoir (714). The drilling system (700) may also include a wellbore path planning system (718). A wellbore path (702) may be planned, using a wellbore path planning system, to intersect the drilling target (720). The wellbore plan may include a starting surface location of the wellbore, or a subsurface location within an existing wellbore, from which the wellbore may be drilled. Further, the wellbore plan may include a drilling target (720) and a planned wellbore path from the starting location to the drilling target (720). Typically, the wellbore plan is generated based on best available information from a geophysical model associated with the geo-physical properties of the subsurface (e.g., wave speed or velocity, density, attenuation, anisotropy), geomechanical models encapsulating stress conditions in a subterranean region of interest, the trajectory of any existing wellbores (which it may be desirable to avoid), and the existence of other drilling hazards, such as shallow gas pockets, over-pressure zones, and active fault planes. Furthermore, the wellbore plan may take into account other engineering constraints such as the maximum wellbore curvature (“dog-log”) that the drillstring may tolerate and the maximum torque and drag values that the drilling system may tolerate.

[0069] The wellbore path planning system (718) may comprise one or more computer processors in communication with computer memory containing the geophysical and geomechanical models, the reservoir simulation, information relating to drilling hazards, and the constraints imposed by the limitations of the drillstring (706) and the drilling system (700). The wellbore path planning system (718) may further include dedicated software to determine the planned wellbore path and associated drilling parameters, such as the planned wellbore diameter, the location of planned changes of the wellbore diameter, the planned depths at which casing will be inserted to support the wellbore and to prevent formation fluids entering the wellbore, and the drilling mud weights (densities) and types that may be used during drilling the wellbore. A wellbore may be drilled, guided by the wellbore path, using the drilling system (700).

[0070] While the reservoir modeler (722), reservoir simulator (732), and wellbore path planning system (718) are shown at the drilling system (700) location, in some embodiments, these elements may be remote from the drilling system (700) location.

[0071] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible, including dimensions, in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMSWhat is claimed:

1. An apparatus for soil gas sampling, comprising: a first outer surface formed from a rigid liquid-impermeable and gas-impermeable material; a second outer surface formed from an aquaphobic and gas-permeable membrane: wherein an edge of the second outer surface is attached to the first edge of the first surface, wherein the first outer surface and the second outer surface entirely enclose an inner volume, and wherein the second outer surface comprises a high specific surface area surface; and a quantity of porous absorbing material, at least partially filling the inner volume, configured to preferentially absorb gaseous analytes.

2. The apparatus of claim 1 , further comprising a sealing cap attached to the first outer surface and configured to seal a cylinder containing the apparatus for soil gas sampling.

3. The apparatus of claim 2, wherein the sealing cap comprises a radio-frequency identification (RFID) tag, configured to transmit information to an interrogation unit.

4. The apparatus of claim 1, wherein the first outer surface and a spatially smoothed approximation to the second outer surface are convex with respect to a first axis.

5. The apparatus of claim 1, wherein the high specific surface area surface comprises a corrugated surface.

6. The apparatus of claim 1, wherein the porous absorbing material comprises activated carbons based on carbonized natural materials.

7. The apparatus of claim 1 , wherein the aquaphobic and gas-permeable membrane is formed a material selected from a group consisting of hydrophobic co-polymers of perfluoropolymers, hydrophobic fluorinated oligomers, hydrophobic fluorinated polymers, non-fluorinated oligomers, and non-fluorinated polymers.

8. A system for collecting a soil gas sample, comprising: a soil gas sampler, comprising: a first outer surface formed from a rigid liquid-impermeable and gas- impermeable material, a second outer surface formed from an aquaphobic and gas-permeable membrane: wherein an edge of the second outer surface is attached to the first edge of the first surface; wherein the first outer surface and the second outer surface entirely enclose an inner volume; and wherein the second outer surface comprises a high specific surface area surface, and a quantity of porous absorbing material, at least partially filling the inner volume, configured to preferentially absorb gaseous analytes; and an autonomous soil gas sampler deployment vehicle, configured to: insert the soil gas sampler into a borehole at a beginning of a sampling time duration, seal, using a sealing cap, the borehole containing the inserted soil gas sampler, unseal the borehole at an end of the sampling time duration, and retrieve the soil gas sampler from the borehole.

9. The system of claim 8, wherein the sealing cap comprises a radio-frequency identification (RFID) tag configured to transmit information from the soil gas sampler to an interrogation unit.

10. The system of claim 9, wherein the interrogation unit is mounted on the autonomous soil gas sampler deployment vehicle.

11. The system of claim 8, wherein the autonomous soil gas sampler deployment vehicle is further configured to drill the borehole prior to inserting the soil gas sampler.

12. The system of claim 8, wherein the autonomous soil gas sampler deployment vehicle comprises an autonomous airborne vehicle.

13. The system of claim 8, wherein the high specific surface area surface comprises a corrugated surface.

14. The system of claim 13 wherein the first outer surface and a spatially smoothed approximation to the second outer surface are convex with respect to a first axis.

15. A method of soil gas sampling, comprising: inserting a soil gas sampler into a borehole at a beginning of a sampling time duration, wherein the soil gas sampler comprises: a first outer surface formed from a rigid liquid-impermeable and gas- impermeable material, a second outer surface formed from an aquaphobic and gas-permeable membrane: wherein an edge of the second outer surface is attached to the first edge of the first surface; wherein the first outer surface and the second outer surface entirely enclose an inner volume; and wherein the second outer surface comprises a high specific surface area surface, and a quantity of porous absorbing material, at least partially filling the inner volume, configured to preferentially absorb gaseous analytes; sealing, using a sealing cap, the borehole containing the inserted soil gas sampler; unsealing the borehole at an end of the sampling time duration; and retrieving the soil gas sampler from the borehole.

16. The method of claim 15, wherein the inserting the soil gas sampler is performed using an autonomous soil gas sampler deployment vehicle.

17. The method of claim 16, wherein the autonomous soil gas sampler deployment vehicle comprises an autonomous airborne vehicle.

18. The method of claim 16, wherein the inserting the soil gas sampler further comprises drilling, using the autonomous soil gas sampler deployment vehicle, the borehole prior to inserting the soil gas sampler.

19. The method of claim 16, wherein the sealing cap comprises a radio-frequency identification (RFID) tag, configured to transmit information from the soil gas sampler to an interrogation unit.

20. The method of claim 19, wherein the interrogation unit is mounted on the autonomous soil gas sampler deployment vehicle.

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