Patent Publication Number: US-2019187108-A1

Title: Removal of polar compounds from a gas sample

Description:
BACKGROUND 
     In the resource exploration and recovery industry, formation fluids are sampled at various phases of exploration, production, and other stages. For example, fluid logging is employed to determine constituents of fluid or formation fluids in a borehole. In many cases, the fluid is passed through a gas chromatograph for analysis. Contaminants, which may, for example, take the form of polar contaminants such as alcohols, ketones, and the like may bias or negatively affect fluid analysis. Therefore, the art would be open to systems and methods for removing contaminants from formation fluids. 
     SUMMARY 
     Disclosed is a method of analyzing formation fluids including introducing a fluid sample into a chromatograph system, passing the fluid sample through a pre-column including a polar column member and a apolar column member in a first flow direction, separating polar constituents from the fluid sample in the pre-column forming an analytical fluid, passing the analytical fluid through a main column of the chromatograph system, and analyzing the analytical fluid in the main column. 
     Also disclosed is a fluid analyzer system including a sample input system and a pre-column system fluidically connected to a carrier gas control unit. The pre-column system includes a polar column member and an apolar column member. The pre-column system includes an inlet and an outlet. A main column has an inlet portion fluidically connected to the pre-column system and an outlet portion. A detector is fluidically connected to the outlet portion of the main column. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a fluid analyzer system in a first or pass through mode, in accordance with an aspect of an exemplary embodiment; 
         FIG. 2  depicts the fluid analyzer system of  FIG. 1 , in a second or analytical mode, in accordance with an aspect of an exemplary embodiment; and 
         FIG. 3  depicts the fluid analyzer system of  FIG. 2 , in a third or backflush mode, in accordance with an aspect of an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     With initial reference to  FIG. 1 , a fluid analyzer system shown in the form of a chromatograph system is indicated generally at  10 . Fluid analyzer system  10  includes a Fluid sample input system  12  and a sample output  14 . Fluid sample input system  12  may take on a variety of forms that promote introduction of a fluid sample, such as, for example, mud gas, to a carrier gas. Fluid sample input system  12  and sample output  14  are fluidically connected to an injection unit  17 . Injection unit  17  may be arranged in a first or pass through mode ( FIG. 1 ) a second or analytical mode ( FIG. 2 ), and a backflush mode ( FIG. 3 ). At this point, it should be understood that the term “fluid” describes liquids, gases and/or mixtures thereof. 
     Fluid analyzer system  10  also includes a carrier gas control unit  23  that may include a carrier gas supply  28  and a vent line  29 . Fluid analyzer  10  may also include a split line  30  that is connected to carrier gas control unit through a valve  32 . In the first mode, a sample may pass from Fluid sample input system  12  through a sample loop (not separately labeled) and out through sample output  14  without being subjected to analysis. 
     In accordance with an exemplary aspect, fluid analyzer system  10  also includes a separation system  38  including a pre-column system  46  and a main column  50 . The term “pre-column system” should be understood to describe that the pre-column of the fluid analyzer system  10  includes multiple columns. Further, it should be understood that the columns themselves may take on a variety of forms including capillary columns having a coating on an inner wall thereof. More specifically, pre-column system  46  includes an inlet (not separately labeled) leading to a first or polar column member  52  and a second or apolar column member  54  connected to an outlet (also not separately labeled) which leads to an inlet portion (also not separately labeled) of main column system  50 . In this manner, pre-column system  46  should be understood to constitute a mixed column  56 . It should also be understood that one of the first and second column members  52  and  54  may define a capillary column including an inner wall (not separately labeled) having a coating (also not separately labeled). The coating may take the form of polyethylene glycol. The terms first and second should not be understood to denote any sequential order of polar column member  52  and apolar column member  54 . It should also be understood that the number and arrangement of columns may vary. 
     Fluid analyzer system  10  is further shown to include a flame ionization detector (FID)  64  fluidically connected to an outlet portion (not separately labeled) of main column  50  and a detector gas control unit  66  fluidically connected to FID  64 . It should be understood that FID  64  may be replaced and/or augmented with other forms of detectors such as thermal conductivity detectors, mass spectrometers, pulsed discharge detectors, plasma emission detectors, photo ionization detectors, pulsed flame photometer detectors, a mass spectrometer, and the like. FID  64  provides an output identifying constituents of the analytical fluid. Specifically, FID  64  measures organic compounds entrained in a fluid sample exiting main column  50 . Other detectors, if employed, may be configured to measure in-organic compounds. An output system  70  may be connected to detector gas control unit  66  and provides a visual output of various constituents of the fluid sample, as will be discussed herein. 
     In accordance with an exemplary aspect, injection unit  17  is placed in the second mode ( FIG. 2 ) and a selected amount of fluid  80  is passed through a valve member  84  in a first flow direction to separation system  38 . Another, residual portion of fluid  88  may be passed back to CCM  23  to a vent  90  in a second flow direction. Selected amount of fluid  80  flows to mixed column  56  through polar column member  52  and apolar column member  54 . Mixed column  56  separates contaminants including polar and apolar constituents from fluid  80  forming a substantially contaminant free analytical fluid (not separately labeled) that is passed to main column  50 . In main column  50 , the substantially contaminant free analytical fluid is further separated into multiple constituents. In accordance with an exemplary aspect, the substantially contaminant free analytical fluid may contain one or more of hydrocarbons such as C1-C8 or above, non-hydrocarbons such as CO2, He, H2, N2, Ar and the like, and additional compounds such as alcohol, ketones, and/or other organic additives. 
     In accordance with an aspect of an exemplary embodiment, after a selected period of time, injection unit  17  is returned to the first mode and at a selected period of time, a backflush mode is initiated as shown in  FIG. 3 . In the backflush mode, a portion of the analytical fluid is passed to main column  50  and backflush gas, such as carrier gas indicated at  101 , is passed through a backflush line  99  via a port  100  back through mixed column  56  to perform a back flush. The back flush cleans unwanted compounds (polar and apolar compounds) from mixed column  56 . A fluid  102  laden with the unwanted compounds may then be passed through vent line  29  and vented through carrier gas control unit  23 . 
     After passing through main column  50 , an amount  120  of the analytical fluid is separated into multiple constituents is passed to FID  64  to be identified. An analysis of amount  120  of the analytical fluid is passed to output system  70  for review. At this point, it should be understood that the fluid analyzer of the exemplary embodiments employ a mixed column that selectively separates both polar and apolar compounds from a fluid sample prior to analysis. Removing these compounds ensures that the sample of fluid more accurately reflects virgin fluid, not substantially influenced by contaminants. In the context of mud gas logging this could mean that the virgin fluid is the formation fluid, and contaminants would be derived from the drilling mud system. 
     The exemplary embodiments may be employed in connection with mud logging operations. Mud logging and/or gas logging is a commonly applied service for the hydrocarbon industry and is referred to as the extraction and measurement of hydrocarbons in fluid (e.g., drilling mud), which may be dissolved, contained as bubbles or microbubbles, and/or otherwise present in the fluid. Measurements are conducted during a drilling operation with a Mass Spectrometer, a Gas Chromatograph, a combination thereof, an optical sensor, any other gas measurement device, or can be derived from fluid samples previously taken. 
     Set forth below are some embodiments of the foregoing disclosure: 
     Embodiment 1: A method of analyzing formation fluids comprising introducing a fluid sample into a chromatograph system, passing the fluid sample through a pre-column including a polar column member and an apolar column member in a first flow direction, separating polar constituents from the fluid sample in the pre-column forming an analytical fluid, passing the analytical fluid through a main column of the chromatograph system, and analyzing the analytical fluid in the main column. 
     Embodiment 2: The method of any prior embodiment, further comprising passing a backflush gas through the pre-column in a second flow direction after a selected period of time. 
     Embodiment 3: The method of any prior embodiment, wherein analyzing the analytical fluid includes passing the analytical fluid into a detector after passing through the main column. 
     Embodiment 4: The method of any prior embodiment, wherein passing the analytical fluid into the detector includes passing the analytical fluid into a flame ionization detector. 
     Embodiment 5: The method of any prior embodiment, further comprising: providing an output identifying constituents of the analytical fluid. 
     Embodiment 6: The method of any prior embodiment, wherein separating the at least one polar constituent includes separating at least one of an alcohol and a ketone. 
     Embodiment 7: The method of any prior embodiment, wherein passing the fluid sample through the pre-column include passing the fluid sample through a capillary column having an inner wall including a coating. 
     Embodiment 8: A fluid analyzer system comprising a fluid sample input system, a pre-column system fluidically connected to a carrier gas control unit, the pre-column system including a polar column member and an apolar column member, the pre-column system including an inlet and an outlet, a main column having an inlet portion fluidically connected to the pre-column system and an outlet portion, and a detector fluidically connected to the outlet portion of the main column. 
     Embodiment 9: The fluid analyzer system according to any prior embodiment, further comprising a detector gas control unit fluidically connected to the detector. 
     Embodiment 10: The fluid analyzer system according to any prior embodiment, further comprising a backflush line fluidically connected between the pre-column system and the main column, wherein the carrier gas control unit is selectively fluidically connected with the outlet of the pre-column system. 
     Embodiment 11: The fluid analyzer system according to any prior embodiment, wherein the detector is a flame ionization detector. 
     Embodiment 12: The fluid analyzer system according to any prior embodiment, wherein the pre-column system is configured to separate at least one polar constituent from a fluid sample received through the fluid sample input system. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). 
     The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.