US3381536A - Mud gas sampling and logging system - Google Patents

Description

May 7, 1968 J. M. HORETH ET AL 3,381,536

MUD GAS SAMPLING AND LOGGING SYSTEM 2 Sheets-Sheet 1 Filed Dec. 6, 1965 ATTORNEY m 0 m w M 6 7 w. m 6 6 W c I NA E: H6O TNH A. ELDY H B P HM m M um D M 9 m m M M 4 RTN 0 A H H W m M 0 w H C mm f N w (I T T C 6 R 4 m 7 I. 5 m M F 6 G I M F r. H m AG E W H T L SW 3 B a U T H Dfi U U N MO M I May 7, 1968 J. M. HORETH ET AL 3,381,536

MUD GAS SAMPLING AND LOGGING SYSTEM 2 Sheets-Sheet 2 Filed Dec. 6, 1965 RICHARD H. LANGENHEIM, INVENTORS 8 WILLIAM Dv HOWARD BY jg? ATTORNEY United States Patent 3,381,536 MUD GAS SAMPLING AND LOGGING SYSTEM John M. Horeth, William 1). Howard, and Richard H.

Langenheim, Houston, Tex, assignors to Esso Production Research Company, a corporation of Delaware Continuation-impart of application Ser. No. 294,674, July 12, 1263. This application Dec. 6, 1965, Ser.. No. 511,930

laims. (Cl. 73-4215) ABSTRACT OF THE DISCLOSURE A mud gas sampling and logging system having sampling unit, a retort, and a gas collecting unit. The sampling unit is connected to the mud stream and adapted to periodically obtain hermetically sealed mud samples. The samples are conducted in a hermetically sealed condition to the retort. The effluent of the retort is conducted into the gas collecting chamber from which the uncondensed gas is displaced by introduced fluids. A float valve is provided in the collecting chamber to prevent entry of the condensed steam and heavy hydrocarbons into the uncondensed-gas discharge ports.

This application is a continuation-impart of Ser. No. 294,674, filed July 12, 1963, now US, Patent No. 3,240,- 068, issued Mar. 15, 1966.

This invention relates to the drilling of boreholes in the earth, and more particularly, to the logging of a rotary drilling operation by the periodic sampling and analysis of the drilling mud to determine its light hydrocarbon content.

It is a common practice in the drilling of oil and gas wells to sample and analyze drilling fiuid returns from bottomhole to determine the nature of the strata being traversed by the drill. In this manner, direct evidence is obtained indicative of the presence or absence of oil and gas in the formations being penetrated. The presence of hydrocarbon gases and other light hydrocarbons in the drilling mud returns, even in amounts of only a few parts per million, is frequently the first and most reliable indication of the likelihood that a commercially productive well can be completed. This amount of hydrocarbons entrained, dissolved, or occluded in the mud stream, is much too small to be determined by simple analytical means. It requires instead highly specialized equipment and techniques.

Recent advances in gas chromatography have led to the development of commercially available devices which provide an accurate and dependable analysis of light hydrocarbons, subject primarily to the requirement that the sample supplied to the chromatograph be substantially free of contamination, including particularly water and heavier hydrocarbons. It has thus become desirable that field procedures for sampling the return mud stream be further developed and improved for the purpose of eliminating errors which are usually inherent in manual operations, including primarily the loss of hydrocarbon gases from the mud return stream due to exposure of the mud to the atmosphere.

In addition to sampling errors, a further problem is to eliminate errors caused by an incomplete and/or inconsistent separation of the light hydrocarbons from the mud samples. It is also essential to provide a sample for chromatograph analysis which is free of contamination from water and heavier hydrocarbons.

Accordingly, it is an object of the present invention to provide a fully automated system for mud-gas sampling and analysis. It is a specific object of the invention 3,381,536 Patented May 7, 1968 to provide apparatus for sampling and degassing drilling mud in a reliable and quantitative manner suitable for field operation. It is a further object of the invention to provide a gas collection device which is suitable for receiving gases and vapors from the degassing zone, and which is capable of separating the hydrocarbon gases from heavier hydrocarbon vapors and. water vapor.

These and other objects of the invention will be apparent from the following detailed description of a preferred embodiment of the invention.

FIGURE 1 is a schematic diagram indicating the relationship of the major subcombinations to the complete system of the invention.

FIGURE 2 is an elevation of the sampling unit of the invention, showing its relationship to the degassing chamher or retort.

FIGURE 3 is a vertical cross-section of the sampling unit, showing its essential features.

FIGURE 4 is an elevational view, partly in section, showing the gas collection unit.

FIGURE 5 is a vertical cross-section of the gas collection unit, showing the detailed structure of certain valves and ports associated therewith.

FIGURE 6 is a horizontal cross-section of the gas collection chamber taken along the line 66 of FIG- URE 4.

FIGURE 7 is a horizontal cross-section of the gas collection chamber taken along the line 77 of FIGURE 4.

In FIGURE 1, the mud returned stream to be analyzed is supplied to sampling unit 11 by means of mud inlet line 12. While sampling unit 11 is on standby, the mud is bypassed through outlet line 13. Periodically, the mud stream is passed through the sampling chamber from which a portion of the mud is injected through line 14 into retort 15. Retort 15 is operated at a temperature within the range of 200450 F., and preferably in the range of 300-400 F., for the purpose of quantitatively expelling hydrocarbon gases contained in the drilling mud sample, including primarily methane, ethane and propane, along with steam vapor and the vapors of butane, pentane, and heavier hydrocarbons, if present.

At the end of about 1 to 3 minutes heating, the retort is vented through line 16 to gas collection chamber 17. In chamber 17 the hydrocarbon gases, including butane and pentane, if desired, are separated from the heavier hydrocarbon vapors and steam vapor, whereupon the uncontaminated gas sample is expelled through line 18 for analysis by recording chromatograph 19.

In FIGURES 2 and 3, the detailed construction of the sampling unit is shown. The mud return stream enters the unit through line 12, and during the standby cycle is bypassed through line 21 into discharge line 13. During the bypass period, push rod 22 is displaced from its indicated position by means of double-acting pneumatic piston 23, such that port 24 is closed by valve 25, and such that port 26 is opened by valve 27. A continuous flow is thus maintained through lines 12, 21, and 13, whereby fresh return mud is available for sampling at the desired time intervals.

When sampling, push rod 22 is returned to the position indicated in FIGURE 3, whereby port 26 is closed and port 24 is opened. Mud then flows through line 28 and chamber 29, then through lines 30 and 31, and is discharged through line 13. Mud is allowed to flow through chamber 29 for a sufiicient time to insure complete displacement of any mud remaining from a previous sampling cycle, and to insure complete filling of chamber 29 with fresh mud. Port 24 is then closed by valve 25, whereby port 26 is again opened, permitting mud to bypass through line 21. Port 32 is left open for a short time which permits any air which may have been trapped in chamber 29 to bleed through line 30. Push rod 34 is then displaced from its indicated position by means of double-acting pneumatic piston 35 whereby port 32 is closed by valve 33, thereby closing chamber 29 which is now completely liquid-full. A check valve (not shown) is provided in line 14 to further insure a complete seal of chamber 29.

Injection ram 36 is then forced into chamber 2% by means of double-acting pneumatic piston 37. As the ram enters chamber 29, a volume of mud is forced through line 14 into retort 15, the displaced volume being exactly equal to the fractional volume of chamber 29 occupied by ram 36. At the end of its stroke, the ram is seated against port 38, thereby forming a seal between chamber 29 and retort 15.

After a suitable period of heating in retort 15, the gases and vapors expelled from the mud sample are vented from the retort through line 16, into gas collection chamber 17. Upon venting the retort, a substantial volume of steam is generated, in addition to that released earlier. The additional steam sweeps out the hydrocarbon gas sample, insuring its complete removal from the retort. Retort is then flushed with water introduced through line 39 and discharged through line 40. Water may also be introduced through line 14 to provide additional flush- As illustrated in FIGURE 3, push rods 22 and 34 appear to occupy a large fraction of the total inside diameter of lines 28 and 30, respectively. Actually, however, the push rods should have a somewhat smaller diameter, in order to provide increased clearance for the flow of drilling fluid, particularly when handling a fluid which carries entrained cuttings of larger than average size.

Referring to FIGURES 4 and 5, gas collection chamber 17 is filled with a liquid, for example water, supplied through line 41 in preparation for receiving the gas sample through line 16. As chamber 17 is filled with water, float 42 is displaced upward until it contacts stop 43, which projects into the chamber a sufiicient distance to prevent float 42 from blocking either of ports 44 and 45. Then, as the sample gases enter chamber 17 through line 16, water is displaced through line 41, with the formation of a gas pocket at the upper end of the chamber. As the water level falls, float 42 is lowered until it reaches the end of line 16 which serves as a stop. During entry of the sample through line 16, valves 46 and 437 are held in the closed position by push rods 48 and 49, which are actuated by double-acting pneumatic pistons 50 and 51, respectively. From the total mixture of gases and vapors which enter through line 16, the steam and heavy hydrocarbon vapors are condensed.

The collected sample is then displaced from chamber 17 by the opening of valve 47 and the introduction of water through line 41. Referring to FIGUURE 7, a mechanism is shown whereby the introduction of water through line 41 is interrupted in time to prevent the entry of contaminants into line 13. Light source 52 and photocell 53 are provided on opposite sides of chamber 17, near the upper end thereof, such that light from source 52 must pass through chamber 17 in order to activate cell 53. Thus, as water enters line 41 displacing the gas sample through line 18, float 42 is raised to a position which blocks the passage of light through chamber 17, thereby deactivating cell 53, which generates a signal used to energize piston 51, closing valve 47. Before analysis by chromatograph 19, the sample passing through line 18 must be diluted to a constant, predetermined volume in order that the sequence of analytical results may be consistently related one to the other. This sample dilution is accomplished in the chromatograph sample loop in accordance with the conventional operation of commercially available chromatographs. A suitable gas chromatograph for use in accordance with the present invention is the Chronofrac model VP-I of Fisher Scientific Company, as fully described in their Bulletin No. 619.

Thereafter, in preparation for receiving the next successive sample, chamber 17 is purged by the opening of valve 46 and the injection of water through line 54. The waste is then discharged through line 41. Subsequently, a new supply of water is introduced through line 41 as previously described.

The complete system of the invention is readily automated, similarly as shown in the disclosure of US. 294,- 674, filed July 12, 1963, of which the present application is a continuation-in-part. That is, the sequence of operations described above may be programmed by a series of rotary cams which are timed to engage a series of microswitches, in the sequence necessary to actuate valves which control the flow of the mud stream, and to actuate the remaining valves or relays which similarly control the remaining stages of the operation.

What is claimed is:

1. Apparatus for sampling and degassing a drilling fluid stream which comprises a hermetically scalable sampling chamber, a retort in combination with said sampling chamber, means for periodically flowing said fluid through said sampling chamber means for temporarily hermetically sealing said sampling chamber, hermetically scalable means for conducting fluid from said sampling chamber to said retort, and means for displacing a predetermined volume of fluid from said sampling chamber and for hermetically sealing said conducting means from said sampling chamber.

2. Apparatus as defined by claim 1 wherein said sampling chamber has an inlet port and first and second outlet ports, wherein said means for temporarily sealing said sampling chamber includes means for closing said inlet port and said first outlet port of said sampling chamber, and wherein said means for conducting fluid into said retort includes conduit means connecting said second outlet port of said sampling chamber with said retort.

3. Apparatus as defined by claim 2 wherein said means for displacing the fluid from said sampling chamber cornprises an injection ram extending through a wall of said sampling chamber at a point opposite said second outlet port therein, a portion of said injection ram being adapted to seal against said second outlet port, and means for forcing said ram into said chamber and against said second outlet port.

4. Apparatus as defined by claim 1 further comprising gas collection means connected to receive a gas sample periodically expelled from said retort, said gas collection means comprising an elongated, substantially vertically disposed vessel, means for admitting a gas and vapor stream from said retort to the interior volume of said vessel, means for condensing steam and heavy hydrocarbon vapors from said total sample, means for displacing the remaining uncondensed gases from said vessel, outlet means in said vessel for discharging said displaced gases, and means for preventing discharge of the condensed steam and heavy hydrocarbons from said outlet means.

5, Apparatus as defined by claim 4 wherein said means for condensing steam and heavy hydrocarbon vapors comprises means for providing a body of cooling fluid within said vessel, in direct contact with the stream of gases and vapors entering said vessel.

6. Apparatus as defined by claim 5 wherein said means for displacing the uncondensed gases comprises means for introducing additional cooling liquid into said vessel.

7. Apparatus as defined in claim 4 wherein said means for preventing discharge of condensed steam and condensed heavy hydrocarbons comprises float means within said vessel at the gas-liquid interface, a light source, and a photoelectric cell, said source and cell being located on opposite sides of said gas collection vessel at a. level near the upper end thereof, whereby the approach of said gasliquid interface to the upper end of said chamber causes the float to intercept the path of li ht between said source and said cell.

6 8. Apparatus as defined in claim 7, further comprising 10. A device as defined by claim 9, further comprising means operative upon the interception of said light path means for periodically flushing said vessel to remove confor inte ru tin the dis lacement of fluids from said taminantsr p g P References Cited vessel.

9. A gas collection device comprising an elongated ves- 5 UNITED S ATES P TENTS sel having upper, lower, and intermediate ports therein, 1,837,858 12/1931 Grace 73-422 float means in said vessel, means for restricting move- 5 955 Bliss et a1. 73421.5 X ment of said float means between the upper and inter- FOREIGN PATENTS mediate ports of said vessel, a photoelectric cell and a 10 600 450 4/1948 Great Britain. light source in combination with said vessel, said cell and source being arranged to detect the arrival of said float DAVID SCHONBERG, P'Ymary Examinermeans at a point near said upper port. S. CLEMENT SWISHER, Examiner.

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