WO2016060681A1

WO2016060681A1 - Pneumatic heating of self-degassed hydrocarbons in drilling fluid

Info

Publication number: WO2016060681A1
Application number: PCT/US2014/061110
Authority: WO
Inventors: Prashant SHEKHAR; Gillies Alexander MACDONALD
Original assignee: Halliburton Energy Services, Inc.
Priority date: 2014-10-17
Filing date: 2014-10-17
Publication date: 2016-04-21

Abstract

A method of heating a sample gas including introducing sample gas from a deaerator into a heat exchanger, where the sample gas is from a drilling mud sample; and heating the sample gas in the heat exchanger using pneumatic heating. An apparatus includes a deaerator, a heat exchanger, where a sample gas stream from the deaerator is coupled to the heat exchanger, and a pneumatic heater, where the pneumatic heater is configured to provide heat to the heat exchanger to heat the sample gas stream.

Description

PNEU MATIC HEATING OF SELF-DEGASSED HYDROCARBONS IN

DRILLING FLUID

BACKGROUND

Drilling a borehole in the earth for the recovery of hydrocarbons (e.g ., oil and gas) may include mounting an earth-boring drill bit on the lower end of a tubular drill string and then rotating it. Sometimes, a downward force is applied to the drill string, which, in combination with the weight of the drill string and other factors may provide a downward force also referred to as weight-on-bit (WOB). The rotating drill bit forms a borehole along a predetermined path toward a target zone. During parts of the drilling process, drilling fluid (sometimes referred to as "drilling mud") may be pumped from the surface through the drill string and directed out of nozzles in the face of the drill bit into the bottom of the borehole. The drilling fluid exiting the bit is forced from the bottom of the borehole to the surface through the annulus between the drill string and the borehole sidewalk

The drilling fluid may perform several functions, including but not limited to maintaining a desired pressure within one or more portions of the borehole, cooling and lubricating the drill bit, carrying rock cuttings to the surface, improving borehole stability, and/or transmitting hydraulic energy to downhole tools. For example, maintaining a minimum pressure in the wellbore may inhibit the influx of formation fluids into the wellbore, while limiting the maximum pressure may avoid fracturing the formation which can lead to drilling fluid loss into the formation.

In most drilling systems, the drilling fluid returned to the surface via the annulus is processed and reconditioned to remove rock cuttings, sand, and other solids, as well as to monitor and/or maintain proper mud weight and density, pH, etc. After such processing and reconditioning, the drilling fluid may be temporarily stored in mud tanks at the surface and then pumped back down the drillstring. In this manner, the drilling fluid is recirculated through the drilling system .

As the drilling fluid is circulated through the drilling system, samples of the drilling fluid returning to the surface may be monitored to identify species of interest (liquids and gases) in the drilling fluid . Typically, species of interest may include hydrocarbons, carbon dioxide, hydrogen, helium, sulfur dioxide, benzene, and/or hydrogen sulfide. In some systems for monitoring the drilling fluid, samples are heated to volatize and/or vaporize liquid species of interest in the drilling fluid . Once volatized and separated from the drilling fluid, the species of interest may be transported to analytical equipment for further processing and analysis. This process of removing species of interest from drilling fluid for analytical purposes is commonly referred to as "degassing" or "extracting," with the resulting gaseous samples being called "representative sample gas" as it is generally representative of the species of interest in the returned drilling fluid stream at that particular time. Once the species of interest are removed, the heated drilling fluid is typically returned to the drilling recirculation loop.

In certain areas of a drilling rig heating of the exchangers requires the use of special devices that are ignition protected because of the close proximity to hydrocarbons. These heaters may present a safety hazard to personnel positioned near the drilling fluid sample exchanger if the ignition protection is not properly installed, maintained, or reinstalled after routine maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of the present invention, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to one having ordinary skill in the art and having the benefit of this disclosure.

Figure 1 is a schematic representation of a sample gas heating apparatus/system of the invention.

Figure 2 depicts a sample gas heat exchanger design according to the invention .

Figure 3 is a schematic representation of a double pipe heat exchanger useful in the invention.

Figure 4A is a schematic representation of a single pass shell and tube heat exchanger useful in the invention .

Figure 4B is a schematic representation of a double pass shell and tube heat exchanger useful in the invention . Figures 5 is a schematic representation of a plate heat exchanger useful in the invention.

Figure 6 is a schematic representation of a spiral heat exchanger useful in the invention.

Figure 7 is a schematic view of an embodiment of an offshore drilling system in accordance with the invention .

DETAILED DESCRIPTION

In the following discussion and in the claims, the terms "including" and "comprising" are used in an open ended fashion, and thus should be interpreted to mean "including, but not limited to . . . ."Also, the term "couple" or "couples" is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components and connections.

The present invention relates to pneumatic heating of sample gases in a heat exchanger.

In some embodiments, the invention is directed to a method comprising : processing a sample gas recovered from a drilling mud sample in a deaerator, transferring the deaerated sample gas to a heat exchanger, heating the sample gas in the heat exchanger using pneumatic heating, and transferring the heated sample gas to a degasser. The energy source for the pneumatic heating may include compressed gas. Compressed air may be used as the energy source for the pneumatic heating. In an embodiment, the pneumatic heating is supplied by a hot air gun. Compressed air may be used to power the hot air gun. In some embodiments, the heat exchanger design is a double pipe or a shell and tube design. The shell and tube design may be a single pass or a double pass design. In one embodiment, the heat exchanger may gravity drain into the degasser.

Several embodiments of the invention are directed to an apparatus comprising : a deaerator; a heat exchanger, wherein a sample gas stream from the deaerator is coupled to the heat exchanger; and a pneumatic heater, wherein the pneumatic heater is configured to provide heat to the heat exchanger to heat the sample gas stream . The apparatus may further comprise a degasser, wherein the degasser is coupled to the discharge of the heat exchanger such that it may receive the heated sample gas. The pneumatic heater may be a hot air gun configured to receive compressed air. The heat exchanger design may be one selected from a parallel, countercurrent, and spiral design. In some embodiments, the heat exchanger is a double pipe or a shell and tube design . The heat exchanger may be configured to gravity drain into the degasser.

Certain embodiments of the invention are directed to a sample gas heating system comprising : a heat exchanger configured to heat sample gas received from a deaerator, wherein said sample gas is from a drilling mud sample; and a pneumatic heater, wherein the pneumatic heater heats the sample gas in the heat exchanger. The heating system may also include a degasser, wherein the heated sample gas is sent to the degasser. Compressed air may be used as the energy source for the pneumatic heating . In an embodiment, the pneumatic heating is supplied by a hot air gun. Compressed air may be used to power the hot air gun . In some embodiments, the heat exchanger design is a double pipe or a shell and tube design. The shell and tube design may be a single pass or a double pass design. In one embodiment, the heat exchanger may gravity drain into the degasser.

Figure 1 shows an embodiment of the invention including a sample gas heating system 100. This apparatus 100 may include a deaerator 110, which separates gasses 111, liquids 112, and solids 113 from drilling mud . The gasses 111 flow to a sample gas heat exchanger 114. The exchanger 114 may be of any design, but is shown with a cast block 115 and coaxial tubes 116, 117. The cast block may also be surrounded by insulation 123. A hot air gun 118 supplies warm heating gas 119 to the coaxial tube 116 of exchanger 114 by using compressed gas as an energy source. Cool heating gas 120 exhausts from the other end of coaxial tube 116o. Some embodiments may include a parallel flow heat exchanger. In a countercurrent arrangement, cool sample gas 111 from the deaerator 110 enters coaxial tube 117i near the cool heating gas exit 120 from coaxial tube 116o. Heated sample gas 121 exits from the other end of coaxial tube 117o near the heated gas entrance 119 to coaxial tube 116i. The heated sample gas 121 flows to a degasser 122, where it is combined with heated mud 123.

Referring to Figure 2, an embodiment of the invention 200 includes a sample gas heat exchanger 214 with a spiral tube configuration. Cool sample gasses 211 flow to a sample gas heat exchanger 214. The exchanger 214 may be of any design, but is shown with a cast block 215 and coaxial tubes 216, 217. The cast block may also be surrounded by insulation 223. A hot air gun (not shown) supplies warm heating gas 219 to the coaxial tube 216 of exchanger 214 by using compressed gas as a n energy source. Cool heating gas 220 exhausts from the other end of coaxial tube 216o. Some embodiments may include a parallel flow heat excha nger. In a countercurrent arrangement, cool sa mple gas 211 from a deaerator (not shown) enters coaxial tube 217i near the cool heating gas exit 220 from coaxial tube 216o . Heated sample gas 221 exits from the other end of coaxia l tube 217o near the heated gas entrance 219 to coaxial tube 216i. The heated sa mple gas 221 flows to a degasser (not shown), where it is combined with heated m ud . The coaxia l tubes 216,217 are shown in a spiral configuration . If more heat transfer area is needed, the number of turns of the tubes 216, 217 may be increased to provide more surface area, or decreased to reduce the surface area . In alternative arrangements, the relative surface area of the tubes 216, 217 may be adjusted by increasing the number of tubes 216, 217 a nd/or decreasing the diameter of the tubes 216, 217.

Pneumatic Heating

Pneumatic heating typically involves forcing a com pressed gas through a nozzle a nd using thermal energy released by the gas as the velocity increases. Compressed air is typica lly used as the energy source, but other compressed gases may be used, such as compressed nitrogen . In hot air guns, a vortex tube may create both cold a ir and hot a ir by directing compressed air into a vortex chamber. This chamber and connecting tube spins the air at a high rate of speed, and the high speed air heats up as it spins along the inner wal ls of the tube towa rd a control valve. A portion of the hot, high speed air is perm itted to exit at the valve. The remainder of the air stream is forced back up through the center of the high speed a ir stream in a second vortex. The slower moving air g ives up energy in the form of heat and becomes cooled as it spins up the tube. The cooled air exits through a cold air exhaust port.

In an embodiment of the invention, a hot a ir gun powered by a compressed gas is used to generate heat and provide that heat to a heat exchanger to heat a sample gas stream from a deaerator that is coupled to the heat exchanger. One hot air gun that may be incorporated to the invention is the Vortec Model 609, available from ITW Vortec, a division of ITW Air Management in Cincinnati, OH . If compressed air is supplied at 80 to 100 psig and 70 °F, the hot air gun may provide hot air at up to about 200 °F.

Heat Exchanger

The sample gas heat exchanges of the invention may include any heat exchanger design known to one of skill in the art. As shown in Figures 1 and 2, the exchanger may be of a cast design with a coaxial tubes either in a "U" shape, or in a spiral shape. As shown in Figure 3, the exchanger may also be of a double pipe design 300. Figure 4A shows a shell and tube design with a single tube pass 400. Figure 4B shows a shell and tube design with a double tube pass 405. Figure 5 illustrates a plate heat exchanger design 500. Figure 6 depicts a spiral heat exchanger design 600. Any of the above designs may be in either parallel or countercurrent configuration. Examples of suitable materials for the block 115,215 and coaxial tubes 116, 117, 216, 217 including, without limitation, steel, aluminum, and copper. In a preferred embodiment, block 115,215 is aluminum that is cast around stainless steel coaxial tubes 116, 117, 216, 217.

Sample Gases

In certain embodiments, the sample gas from the muds may include at least one of methane, ethane, propane, i-butane, n-butane, i-pentane, n- pentane, n-hexane, ethane, propene, carbon dioxide, hydrogen, helium, sulfur dioxide, benzene, hydrogen sulfide, and combinations thereof.

Deaerator and Degasser

In general, as shown in Figure 1, degasser 122 may comprise any suitable device known in the art for separating gases (e.g ., gases 121) from liquids (e.g., hot drilling fluids/mud 123). Deaerator 110 may comprise any suitable device known in the art for separating gases (e.g ., gases 111) from liquids 112 and from solids 113.

Referring now to FIG. 7, an embodiment of an offshore drilling system 10 for drilling a subsea borehole 11 in an earthen formation 12 is shown . In this embodiment, system 10 includes an offshore platform 20 (e.g., a semi- submersible platform) disposed at the sea surface 13, a subsea blowout preventer (BOP) 30 mounted to a wellhead 31 at the sea floor 14, and a lower marine riser package (LMRP) 40 mounted to the upper end of BOP 30. The upper end of LMRP 40 comprises a riser flex joint 41 connected to the lower end of a d rill ing riser 22 extend ing from platform 20. As will be described in more detail below, riser 22 ta kes m ud returns from borehole 11 to platform 20. Flex joint 41 allows riser 22 to deflect angularly relative to BOP 30 and LMRP 40 while hyd rocarbon fluids flow from well bore 11, BOP 30 and LM RP 40 into riser 22.

Platform 20 is equipped with a derrick 21 that supports a hoist (not shown) . A drill string 50 suspended from derrick 21 extends from platform 20 throug h riser 22, LM RP 40, BOP 30, and into borehole 11. Drill string 50 includes a plurality of d rill pipe joints coupled together end -to-end, a bottom-hole- assem bly (BHA) 52 coupled to the lowermost pipe joint, and a drill bit 54 coupled to the lower end of BHA 52. During d rilling operations, weig h-on-bit (WOB) is a pplied as d rill bit 54 is rotated, thereby enabling drill bit 54 to engage formation 12 and drill borehole 11 along a predeterm ined path toward a target zone. In general, drill bit 54 may be rotated with drill string 50 from platform 20 with a top drive or rota ry table, and/or with a downhole m ud motor within BHA 52. Casing 32 is installed and cemented in a n upper portion of borehole 11 extending downward from wellhead 31 at the sea floor 14.

An annular space or annulus 60 is disposed about drillstring 50 and extends from drill bit 54 to platform 20. Moving upward from drill bit 54, a nnulus 60 is rad ia lly positioned between the sidewall 15 of borehole 11 and d rill string 50, between casing 32 and drill string 50, between BOP 30 and drill string 50, between LMRP 40 and drill string 50, and between riser 22 and d rill string 50. In other words, annulus 60 extends through borehole 20, casing 32, BOP 30, LMRP 40, and riser 22.

Referring still to FIG. 7, a drilling fluid supply or circulation system 70 d isposed on platform 20 processes, cond itions, samples, and circulates a suita ble drilling fluid, also referred to as mud or d ril l ing mud, to cool drill bit 54, remove cuttings from the bottom 16 of borehole 11 and carry them to platform 20 throug h annulus 60, a nd maintain a desired pressure or pressure profile in borehole 11 during drilling operations. In this embodiment, drilling fluid supply system 70 includes a drilling fluid cond itioning system 73, a drilling fluid reservoir or tank 74, and a drilling fluid supply or mud pump 76. A drill ing fluid return line 72 couples conditioning system 73 to riser 22, and a dril ling fluid supply line 77 couples m ud pump 76 to the upper end of drill string 50. Thus, d rill ing fluid returning from borehole 11 through annulus 60 is suppl ied to system 70 via return line 72, and drilling fluid processed and conditioned by system 70 is supplied by system 70 to drill string 50 via supply line 77.

During drilling operations, drilling fluid from tank 74 is pressurized by pump 76 and sent through fluid supply line 77 into drill string 50. The drilling fluid flows down drill string 50 and is discharged at the borehole bottom 16 through nozzles in drill bit 54. The drilling fluid cools bit 54 and carries the formation cuttings to platform 20 through annulus 60. The drilling fluid returned to platform 20 via annulus 60 exits the upper end of riser 22 through return line 72 and flows into conditioning system 73, which cleans and conditions the drilling fluid before it is circulated back into drill string 50. In particular, conditioning system 73 removes undesirable solids from the drilling fluid (e.g., formation cuttings) and removes undesirable gases from the drilling fluid (e.g., dissolved hydrocarbon gases). Such functions may be performed in conditioning system 73 by equipment known in the art including, without limitation, shakers, desanders, desilters, degassers, mud cleaners, centrifuges, etc. The cleaned drilling fluid flows from conditioning system 73 into tank 74. The chemistry (e.g., pH, concentration of corrosion inhibiting chemicals, etc.) and density of the drilling fluid can be adjusted in conditioning system 73 or in tank 74. The cleaned and conditioned drilling fluid in tank 74 is then supplied by pump 76 back down drill string 50. In this manner, drilling fluid may be continuously circulated through drilling system 10, providing cleaned, processed, and conditioned drilling fluid to the tool string.

Referring still to FIG. 7, in this embodiment, drilling system 10 also includes a drilling fluid sampling system 100 disposed on a skid supported by platform 20. Sampling system 100 is in fluid communication with circulation system 70 and continuously samples and analyzes drilling fluid returning from annulus 60 to identify species of interest within the drilling fluid. In this embodiment, samples of drilling fluid are continuously taken by sampling system 100 from return line 72 via a sample supply line 101 positioned upstream of conditioning system 73, and analyzed samples of drilling fluid are continuously returned from sampling system to return line 72 via a sample return line 102 positioned upstream of conditioning system 73. Thus, sampling system 100 may acquire unprocessed samples of drilling fluid returning from annulus 60, analyze the unprocessed samples of drilling fluid, and then return the analyzed samples of drilling fluid to return line 72 for subsequent processing by conditioning system 73. As noted above and will be described in more detail below, sampling system 100 may analyze samples of drilling fluid returned to the surface from annulus 60. However, it should be appreciated that a sampling system (e.g., sampling system 100) can also be provided to analyze samples of drilling fluid being pumped down the drill string (e.g., drill string 50). By analyzing samples of drilling fluid pumped downhole and returned from the borehole, a differential analysis of the species of interest identified, and qua ntities thereof, can be performed .

EXAMPLES

The invention having been generally described, the following examples are given as particular embodiments of the invention and to demonstrate the practice and advantages hereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims to follow in any manner.

Example 1

Heat Exchanger Sizing

Case 1 : In this scenario, it is assumed that no mud is coming into the heat exchanger along with the self degassed sample gases.

Heat Requirement for Methane

c

Specific Heat Capacity of Air (Cp) 1182.4 J/Kg°C

Temp Change (5T) 50 c

Energy eqd. 235.153898 Watt

Energy generated. (6Q=m*Cp*6T) 0.235153898 KW

The calculations show that the heat generated is much higher than the heat requirement for methane to heat up to 80 °C. Thus one heat gun may be sufficient to heat up the sample gas separating out of deaerator.

Example 2

Mud in Deaerator

In this scenario, it is assumed that the mud is coming into the heat exchanger along with the self degassed sample gases. In some embodiments, the mud is heated up pneumatically before it goes to the degasser.

Heat Requirement for Mud

Diameter of sample path 0.25 in

Diameter of sample path 0.00635 m

Area of path 3.16683E-05 m2

Overall length of tu bing 36 in

Overall length of tu bing 0.9144 m

Volume flow rate of sample 0.25 L/min

Volume flow rate (Vf) 0.000004175 m3/sec

Volume of flow path (vp) 2.89575E-05 m3

Time for which the sample travels inside the heat 6.935922964 sec

exchanger =(Vp/Vf)

The calculations show that, even if mud comes in throug h the heat exchanger, the heat exchanger can heat up the mud to 80 °C. With 3 ft of tubing, the m ud will stay inside the heat exchanger for approximately 7 seconds. That may be adequate to heat the mud sample. Thus, the overall dimensions in this scena rio may be l imited to 24" X 24" X 6" .

While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skil led in the art without depa rting from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting . Many variations and modifications of the invention d isclosed herein are possible and are within the scope of the invention . Use of the term "optionally" with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required . Both alternatives are intended to be within the scope of the claim .

Embodiments disclosed herein include :

A: A method comprising : processing a sample gas recovered from a d rill ing mud sample in a deaerator, transferring the deaerated sample gas to a heat exchanger, heating the sample gas in the heat exchanger using pneumatic heating, and transferring the heated sa mple gas to a degasser..

B: An apparatus comprising : a deaerator; a heat exchanger, wherein a sample gas stream from the deaerator is coupled to the heat exchanger; and a pneumatic heater, wherein the pneumatic heater is configured to provide heat to the heat exchanger to heat the sa mple gas stream .

C: A sample gas heating system comprising : a heat excha nger config ured to heat sample gas received from a deaerator, wherein said sam ple gas is from a d rill ing mud sample; a nd a pneumatic heater, wherein the pneumatic heater heats the sample gas in the heat excha nger. Each of embodiments A, B and C may have one or more of the following additiona l elements in any combination : Element 1 : further comprising send ing the heated sample gas to a degasser. Element 2 : wherein the pneumatic heating is supplied by a hot air gun. Element 3 : wherein an energy source for the pneumatic heating is compressed air. Element 4: wherein compressed air powers a hot air gun . Element 5 : wherein the heat exchanger design is one selected from a para llel, countercurrent, a nd spiral design. Element 6: wherein the heat exchanger design is a double pipe or a shell a nd tube desig n. Element 7 : wherein the shel l a nd tube design is a single pass or a double pass desig n. Element 8 : wherein the heat exchanger gravity drains into the degasser. Element 9 : further comprising a degasser, wherein the degasser is coupled to the discharge of the heat exchanger such that it may receive the heated sample gas. Element 10 : wherein the pneumatic heater is a hot a ir gun config ured to receive compressed a ir. Element 11 : wherein the heat exchanger comprises a block and coaxial tubes. Element 12 : wherein the block of the heat exchanger is cast around the coaxial tubes. Element 13 : wherein the energy source for the pneumatic heating is compressed gas .

Numerous other modifications, eq uivalents, and alternatives, wil l become appa rent to those skilled in the art once the above disclosure is fully appreciated . It is intended that the following claims be interpreted to embrace a ll such modifications, equivalents, and alternatives where a pplicable.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A method comprising :

processing a sample gas recovered from a drilling mud sample in a deaerator;

transferring the deaerated sample gas to a heat exchanger;

heating the sample gas in the heat exchanger using pneumatic heating; and

transferring the heated sample gas to a degasser.

2. The method of claim 1, wherein the energy source for the pneumatic heating is compressed gas.

3. The method of claim 1, wherein the pneumatic heating is supplied by a hot air gun .

4. The method of claim 1, wherein an energy source for the pneumatic heating is compressed air.

5. The method of claim 4, wherein compressed air powers a hot air gun.

6. The method of claim 1, wherein the heat exchanger design is one selected from a parallel, countercurrent, and spiral design.

7. The method of claim 1, wherein the heat exchanger design is a double pipe or a shell and tube design.

8. The method of claim 7, wherein the shell and tube design is a single pass or a double pass design .

9. The method of claim 2, wherein the heat exchanger gravity drains into the degasser.

10. An apparatus comprising :

a deaerator;

a heat exchanger, wherein a sample gas stream from the deaerator is coupled to the heat exchanger; and a pneumatic heater, wherein the pneumatic heater is configured to provide heat to the heat exchanger to heat the sample gas strea m .

11. The apparatus of claim 10, further comprising a degasser, wherein the degasser is coupled to the discharge of the heat excha nger such that it may receive the heated sample gas.

12. The apparatus of claim 10, wherein the pneumatic heater is a hot air gun configured to receive compressed air.

13. The apparatus of claim 10, wherein the heat exchanger design is one selected from a pa ral lel, countercurrent, a nd spiral desig n.

14. The apparatus of claim 10, wherein the heat exchanger design is a double pipe or a shell and tube design .

15. The apparatus of claim 11, wherein the heat exchanger is config ured to g ravity dra in into the degasser.

16. A sample gas heating system comprising :

a heat exchanger configured to heat sample gas received from a deaerator, wherein said sa mple gas is from a drill ing mud sample; and

a pneumatic heater, wherein the pneumatic heater heats the sa mple gas in the heat exchanger.

17. The system of claim 16, further comprising a degasser, wherein the heated sample gas is sent to the degasser.

18. The system of claim 16, wherein the pneumatic heater is a hot air gun.

19. The system of claim 16, wherein an energy source for the pneumatic heater is compressed air.

20. The system of claim 17, wherein the heat exchanger gravity drains into the degasser.