Apparatus for draining high pressure fluid samples

Abstract: Apparatus for draining a high pressure sampler bottle comprises a first conduit (106) connected between a fluid reservoir (102) and the sampler bottle (4); a first pump (110) in said first conduit, the pump having an output (114) and an input (112) port, said input port of said pump being connected to said reservoir and the output of said pump being connected to said sampler bottle (4); an output conduit leading from said sampler bottle (4); a first valve (134) placed in said output conduit; a sample vessel (122) receiving said output conduit, said sample vessel having a discharge conduit (140) which leads back into said first conduit; a second valve (138) placed in said discharge conduit; and means (141), located in line with said discharge conduit, for pumping the fluid from said sample vessel (122) to said first conduit (106).

Description: This invention relates to an apparatus for draining high pressure fluid samples without mercury. In the oil and gas industry, it is necessary from time to time to obtain one or more samples of fluid from a wellbore (see U.S. patent specifications nos. 4,787,447 (Christensen), 4,766,955 (Petermann), 4,665,983 (Ringgenberg) and 4,502,537 (Carter, Jr). The fluid which is typically required for analysis is fluid from a subterranean formation or a reservoir intersected by the well so that it can be determined whether the fluid is suitable for being produced. In general, to obtain a sample, a fluid sample tool is first lowered into the well, such as on a tubing string, a wireline or a slickline. When the tool is at the desired depth, a port (one or more openings) defined on the sampler will open, such as in response to pressure exerted through the well fluid or in response to an electrical actuation from the surface. The open port admits well fluid into a sample retaining chamber within the tool. The port is thereafter closed, the tool is withdrawn from the well, and the sample is taken from the chamber for analysis. The sample retaining chamber, or simply sampler chamber, is generally enclosed in a cylindrical housing, as described for example in U.S. patent specifications nos. 4,665,983 (Ringgenberg) and 4,903,765 (Zunkel), to which reference should be made for further details. U.S. specification no. 4,665,983 discloses a method of draining the chamber containing the reservoir fluid sample. When the testing string is tripped out of the wellbore, the fluid sample may be removed from the downhole sampler valve on site or the upper section of the sampler valve containing the sample chamber may be removed from the lower section thereof by backing off the air chamber case from the sample chamber case and oil chamber mandrel from sample chamber mandrel, and the detached upper section is then transported to a laboratory or shop. In either case, when a fluid sample is to be removed from the sample chamber, the downhole sampler valve is placed in a horizontal position and a drain assembly is then secured thereto (see column 9, lines 33-44 of U.S. patent specification 4665983). To drain the sample chamber fluid, it is necessary to threadedly connect the drain assembly to the predefined drained ports in the sampler valve. The fluid sample will drain from the sample chamber, through the drain assembly, into a collector vessel. To ensure complete draining and capture of the fluid sample from the sample chamber, it is desirable to have a pump and a source of mercury sufficient to fill the sample chamber connected to the pressure line running to the bottom nipple. Mercury is then pumped into the sample chamber of the sampler valve through the drain assembly, and the fluid sample is displaced upwardly into the drain assembly by the heavier mercury (see column 10, lines 1-10 of the U.S. patent). The method of draining the reservoir fluid filled chamber as disclosed in both U.S. patent specifications nos. 4,665,983 and 4,903,765 has several distinct disadvantages. First, the method disclosed is not a closed system such that there is a potential release of hazardous wellbore fluids and gases (such as hydrogen sulfide). Second, the methods disclosed require the handling of mercury which is a hazardous material. Third, the method disclosed does not allow the determination of the bubble point pressure while the fluid sample is still in the fluid sampler chamber. We have now devised an apparatus for draining a high pressure sampler bottle, by which disadvantages of the prior art can be reduced or overcome. According to the present invention, there is provided an apparatus for draining a high pressure sampler bottle, which apparatus comprises a first conduit connected between a fluid reservoir and the sampler bottle; a first pump in said first conduit, the pump having an output and an input port, said input port of said pump being connected to said reservoir and the output of said pump being connected to said sampler bottle; an output conduit leading from said sampler bottle; a first valve placed in said output conduit; a sample vessel receiving said output conduit, said sample vessel having a discharge conduit which leads back into said first conduit; a second valve placed in said discharge conduit; and means, located in line with said discharge conduit, for pumping the fluid from said sample vessel to said first conduit. The hydraulic circuit used in the present invention contains a completely closed system such that the fluid can be transferred from the downhole sampler to the sample vessel without the exposure of hazardous gas or release of high pressure. Also, the present invention allows for the calculation of the bubble point pressure before the sample is drained, if desired. The present invention allows for the removal of the fluid sample without mercury. Another advantage is the draining of the reservoir under controlled movement of the fluid by use of the displacement pump. Yet another advantage allows for the continual monitoring of the fluid sample pressure. Still another advantage is the low maintenance due to the elimination of pressure relief valves and bleed-off valves present in the prior art systems. Preferably, the apparatus further comprises a third conduit with one end of said third conduit being connected to said first conduit, and the other end of said conduit being connected to said sample vessel; and a third valve located in the line of said third conduit. Preferably the apparatus further comprises means for gauging the pressure of said first output and third conduit line; and means for evacuating air and fluid from the conduit between said sample bottle and said sample vessel. Preferably, the means for pumping said fluid from said sample vessel to said first conduit includes a pump; a direct conduit feeding into said pump; a bypass conduit leading from said direct conduit, feeding into said first conduit; a relief valve placed in said bypass conduit; an output conduit leading from said pump; and a valve operable between an open and close position, placed in said output conduit. Further the apparatus may also comprise first means, connected to said first conduit for gauging the pressure in said conduit; a relief conduit with a fourth valve, connected to said first conduit upstream of sampler bottle; second means connected to said output conduit, for gauging pressure within said conduit lines; a fifth valve located in stream with discharge conduit line, with an output line leading from said fifth valve leading to a discharge vessel for receiving excess fluid; and third means, connected to said discharge line, for gauging pressure within said conduit line. A method of obtaining a bubble point pressure of fluid held in a sample bottle comprises the steps of connecting to a fluid reservoir with a pump in stream with said first conduit, then connecting said first conduit to a Data Acquisition System for plotting the pressure increase within the conduit versus time wherein a graphical representation of the pressure within the conduit versus time is obtained. Further, the fluid is pumped to a first pressure P₁, with the pressure being measured by the Data Acquisition System. P₁ corresponds to the first change in slope of the graph represented by pressure versus fluid displacement. Pumping is continued to P₂ wherein P₂ is measured by the Data Acquisition System, and P₂ being represented by a second change in slope of the graphical representation of pressure versus fluid displacement. Finally, the graphical representation of pressure versus fluid displacement is plotted. In order that the invention may be more fully understood, reference is made to the accompanying drawings, wherein: Fig. 1 is a schematic and block diagram of a wellbore and rig which includes a high pressure sampler bottle for obtaining a reservoir fluid sample. Fig. 2 is a longitudinal schematic view of a high pressure sampler bottle. Fig. 3 is a schematic drawing of one embodiment of hydraulic circuit of the present invention. Fig. 4 is a graphical representation of the pressure of a high pressure sampler bottle versus pump displacement. Figs. 5A and 5B form a longitudinal sectional view of one preferred embodiment of the means for displacing fluid in the hydraulic circuit. In the description which follows, like parts are generally marked throughout the specification and drawings with the same reference numerals, respectively. Referring to Fig. 1, a fluid sampling tool 2, representing the high pressure sampler bottle, is lowered into an oil and gas wellbore prior to performing a Drill Stem Test, as will be appreciated by those skilled in the art. An apparatus and method of obtaining a reservoir fluid sample is described in U.S. patent specifications nos. 4,903,765 and 4,665,983 to which reference has already been made. After obtaining a sample of fluid, the fluid sampling tool 2, with high pressure sampler bottle contained within, are pulled out of the wellbore. The high pressure sampler bottle can be detached from the downhole tool apparatus; it should be noted that the pressure contained within the sampler bottle has not been allowed to bleed off during this removal stage. In accordance with the teachings of the present invention, the sampler bottle can now be drained into a sealed drain bottle, also known as a sampler vessel. As will be more fully understood following the detailed description of the present invention, the draining of the sampler bottle, and determination of the bubble point pressure can be carried out at the well site because of the compact size of the hydraulic draining circuit. Referring now to FIG. 2, the high pressure sampler bottle 4 is shown. An inlet face 6 and an outlet face 8 are located at each end of the sampler bottle. Within the sampler bottle, an isolation piston 10 defines a sample chamber 12 and a clean fluid chamber 14. Sampler bottle valves 16, 17 are securely attached on this sampler bottle, directly downstream of the outlet face 8 and 6, respectively. Referring now to FIG. 3, the hydraulic circuit of the present invention is generally shown at 100. The apparatus of the present invention comprises a fluid reservoir 102 which is filled with a suitable fluid such as distilled water 104. Other suitable fluids such as silicon oil can be used. The fluid reservoir is connected to first conduit 106, the first conduit 106 being attached at the bottom 108 of the fluid reservoir 102. The hydraulic circuit also includes a first pump 110, which includes an inlet 112 and outlet 114, the first pump being attached and in the stream of the first conduit 106. The conduit 106 leading from the first circuit valve 116 is connected to the high pressure sampler bottle 4, at the inlet face 6. A first branch 118 of the conduit 106, contains a first circuit valve 116. The outlet from the first circuit valve leads to a bleed off chamber 120 for bleeding pressure in conduit 106. Also included in the hydraulic circuit is a drain bottle 122, also known as a sample vessel 122. The reservoir fluid sample taken from the wellhead of the oil and gas reservoir and located in sampler chamber 12 of the sampler bottle 4 will be transferred to the sample vessel 122. A separation piston 124 is slidably disposed on the inner peripheral of the sample vessel 122. The separation piston 124 forms two chambers, a first sample vessel chamber 126 and a second sample vessel chamber 128. Before the reservoir fluid sample is drained, the separation piston 124 will be located at the upper end 130. At one end of the sample vessel, an inlet face 132 represents the inlet for fluids which will be entering the sample vessel 122. A second circuit valve 134 is placed upstream of the inlet face 132, the second circuit valve 134 being an on and off valve, such as can be purchased from Autoclave Incorporated. These types of valves are also referred to as needle valves, as will be appreciated by those skilled in the art. At the opposite end of the sample vessel, relative to the inlet face 132, is the outlet face 136. Placed downstream of the outlet face 136 will be a third circuit valve 138, which is an on and off type of valve, and is similar to other on and off valves utilized in this hydraulic circuit. A second conduit 140 leads from the third circuit valve 138. A means for pumping 141 the fluid located in the second conduit 140 is placed in line. Generally, the means for pumping 141 is a displacement pump as shown in figures 5A and 5B; the displacement pump will be discussed in further detail later on in this application. It should be appreciated, however, that other displacement pumps can be utilized in order to displace the fluid located in the conduit 140. An on and off valve 143 is placed in tandem, with conduit 140, downstream of the displacement pump 141. The first conduit 106 and second conduit 140 intersect at 142, at which point the two conduits are in fluid communication. The hydraulic circuit further comprises a third conduit line, 144, with the third conduit line 144 being connected to the first conduit 106, such that the two conduits are in communication. The point at where the two conduits connect, 146, represent an area upstream of the inlet face 6 of the sampler bottle 4, but downstream of the point of connection at the second conduit 140 and first conduit 106, represented by numeral 142. The third conduit line 144 is also connected to the first conduit line 106 at a second point 148, this second communication being downstream of the sampler bottle 4. A fourth circuit valve, 150, is placed in tandem with conduit 144, with valve 150 being a two-way valve as previously described. The hydraulic circuit also includes means for gauging and recording the pressure of the hydraulic circuit. First, the first conduit 106 has attached at a point upstream of the inlet face 6 a two-way directional sleeve 152. The first sleeve 153 directs the first conduit 106 to the sampler bottle 4, while the second sleeve 154 directs the first conduit 106 to a pressure gauge 156 and Data Acquisition System 158. The Data Acquisition System 158 is a pressure sensor which records pressure relative to time. The Data Acquisition System 158 can be connected to a microprocessor, and the pressure can be graphically represented in real time, and plotted continuously through the obtaining of a bubble point pressure and draining of the sampler bottle 4. A fourth conduit 172 with an on and off valve 165 contained in tandem is disclosed. The fourth conduit 172 intersects the second conduit 140 at 174, and the first conduit at 176. The hydraulic circuit 100 can contain other pressure gauges located throughout the system which will enable the operator to determine the pressure in the conduit at any given time during either the calculation of the bubble point pressure or draining of the sampler bottle. For instance, pressure gauge 160 can be placed at the intersection of the first conduit and third conduit, downstream of sampler bottle 4. Pressure gauge 162 can be placed in the second conduit 140, at a point downstream of the sampler vessel 122, but upstream of the displacement pump 141. The hydraulic circuit 100 will also contain two bleed off sample vessel valves, 164 and 166. Both of these valves will lead to fluid basins 168 and 170. Fluid basing 168 and 170 can collect fluid which is bled off from the bleed off valves 164 and 166. Optionally, the hydraulic circuit 100 can also contain a vacuum pump (not shown). The referred location of the vacuum pump would be down stream of the sampler bottle 4 and upstream of the drain bottle 122. The vacuum pump will evacuate air and fluid which may be contained in the conduit between the sampler bottle 4 and drain bottle 122. Method of Operation : Figure 4 is a typical graphical representation of pressure of the high pressure sampler bottle 4 versus pump displacement. Line 200 of FIG. 4 represents the typical pressure increase in the sampler bottle 4 experienced from the fluid in the hydraulic line when being pumped, and when sampler bottle valve 16 is closed. In other words, fluid is being pumped into fluid chamber 14, which acts against piston 10 and causes the reservoir fluid sample in sample chamber 12 to compress. It should be remembered that this reservoir fluid sample may contain oil, gas and water from the subterranean formation. In order to obtain the bubble point pressure of the reservoir fluid held in sampler bottle 4, first, it is necessary to connect the reservoir of distilled water 102 to the first pump 110 with first conduit 106. As shown in FIG. 3, the first conduit 106 leads to the sampler bottle 4, as well as to the two way directional sleeve 152, which will also lead to the Data Acquisition System 158. The sampler bottle valve 16 is closed. Also valves 150, 116, 143 and 165 are closed. The first fluid pump 110 is used to increase the line pressure until the pressure inside the sampler bottle 4 is reached. The isolation piston 10 will begin to compress the gas and oil sample located within sample chamber 12 when the pump pressure of first pump 110 exceeds the sample pressure. As the pressure in sample chamber 12 is increased further, the gas in the oil and gas sample chamber 12 will continue to compress. When the pressure gets high enough in sample chamber 12, all of the gas will be in solution with the oil of the fluid sample causing the compressibility of the fluid sample to decrease dramatically. This will cause a rapid pressure increase in the fluid chamber 14 and pump pressure as first pump 110 continues to pump at the same volumetric rate. Referring again to FIG. 4, line 200 shows the characteristic plot of pump displacement versus sample pressure as the gas was compressed into the liquid solution. The first change of slope, 201, represents where the gas begins to compress and indicates the pressure of the oil and gas fluids in sample chamber 12. This pressure is represented by P₁, at 202. The second change of slope, 204, indicates the bubble point of the oil and gas fluid sample, which is represented by P₂ at 206. In accordance with the teachings of the present disclosure, the pressure of the oil and gas fluid sample can be observed visually on a pressure gauge 156, or recorded and plotted by the Data Acquisition System 158. The pressure at any given point in the system can be gauged and/or recorded, as deemed necessary and desirable by the operator. In order to drain the sampler bottle 4, first, it is necessary to close valves 116, 143, 150, and 166. Then, with displacement pump 141, a pressure is pumped up to approximately 500 psi (3.45 MPa) above the previously determined bubble point pressure. By doing this, the separation piston 124 in sample vessel 122 will move to the uppermost end, adjacent to the sample vessel inlet 132. Next, bleed off valve 164 and check valve 165 are closed. The sampler bottle valves 16 is then opened. The operator can then begin fluid displacement by starting up the displacement pump 141. At this point, fluid is moving in the hydraulic circuit. As fluid is being displaced, isolation piston 10 moves relative to sample bottle 4. This movement of isolation piston 10 causes the oil and gas sample to be displaced, exiting from sampler bottle 4, into first conduit 106, and into sampler vessel 122 in the first sample vessel chamber 126. Once a predetermined amount fluid has been displaced inside the sample vessel, a displacement volume can now be calculated by subtracting the amount of fluid which has been displaced from this sample bottle. This information can now be utilized when a fluid analysis is performed on the fluid sample. With regards to the means for displacing fluid within the hydraulic fluid circle, please refer now to FIGS. 5A and 5B. Generally, the means for displacing fluid in the hydraulic circuit includes a cylindrical housing 300 with a first 302 and a second port 304 defined within said housing 300. A power piston 306 is disposed and received slidably within said cylindrical housing 300. The power piston 306 has defined on one end a threaded portion 308. Also defined with the cylindrical housing, is a threaded sub 310 which has an internal bore 312A. Defined on said internal bore are internal thread connection means 312 which will threadily mate with the threads located on the power piston 308. On the outer diameter of the threaded sub 310, is a first surface 311 which extends to shoulder 314. A second surface, 316, is defined thereon. The threaded sub terminates at radial flat surface 318. A capped portion 320 with external thread connection means 322 is threadily connected to a spacer sub 324. The spacer sub contains on the inner diameter thread connection means 326 which will be threadily mated with threads 322 of the capped sub 320. The spacer sub 324, also contains inner thread connection means at 328 at a second end. Threads 328 located on said spacer sub 324 will be threadily connected to the cylindrical housing 300. An internal spacer sub 330 is located on the inner peripheral of the cylindrical housing. The inner spacer sub 330 contains a first shoulder 332 which will abut the threaded sub 318. The internal spacer sub 330 has an internal bore which defines a plurality of grooves 338 and 340, containing elastomeric seal means 339 and 341. On the outer periphery of said internal spacer sub 330, is contained a plurality of recess grooves 334 and 336, which contain elastomeric seal means 335 and 337. The internal spacer sub 330 terminates at shoulder 339. The power piston 306 contains a first surface 342 which terminates at radial flat shoulder 344. A second surface, 346, has defined thereon a recessed groove 348, an elastomeric seal means 350 placed within the groove 348. Surface 346 terminates at radially flat shoulder 352 which abuts the shoulder 339 of the internal spacer sub. Referring back to Fig. 5B, a third surface 354 of the power piston extends therefrom as a smooth cylinder until terminating at threads 308. Wrenching flats 309 are defined thereafter. Referring to Fig. 5A, the cylindrical housing 300 contains internal thread means 360. A top adapter sub 362 contains a first outer diameter surface 364 which terminates at shoulder 366, which in turn leads to external threads 370. External threads 370 of said top adapter sub 362 threadily connects to the internal thread means 360 of the cylindrical housing. The thread means 370 terminate at shoulder 372 which is a radially flat shoulder extending to fourth surface 374. Surface 374 has defined thereon a plurality of grooves, 376 and 378, which have defined therein elastomeric means 377 and 379. The fourth bore ends at radially flat shoulder 380. Connected to the output 302 and input ports 304, are two conduits. The first conduit 382 has a first branch 386 and a second branch 388. The conduit 384 has two branches: 390 and 392. The first branch conduit 386 has defined therein a check valve 394 which allows flow only into conduit 382. The second valve 396 in branch 390 allows fluid flow only into conduit 384. Joining conduit 389 joins check valves 394 and 396 in fluid communication. Joining conduit 391 joins check valve 398 and 400 in fluid communication. Placed in conduit 388 is a check valve 398; placed in conduit 392 is check valve 400. Check valve 398 allows fluid only out of conduit 382 while check valve 400 allows fluid only out of conduit 392. Two conduits, representing an input line 402 and an output line 404 connect to joining conduits 389 and 391. Input line 402 is connected to conduit 386 at 406. Output line 404 is connected to conduit 388 at 408. It should be noted that in order to move the power piston longitudinally the threaded sub 310 can be rotated either manually or by some automatic mechanical means. In order to move the piston, the threaded sub, which is slidably received within the cylindrical housing, is rotated in a counterclockwise or clockwise rotation. Because of thread connection means 312 located on the inner diameter of the threaded sub 310, as well as the external thread connection means located on said power mandrel 308, the rotation of the threaded sub 310 causes the longitudinal movement of the power piston 306. As the power piston 306 is moved longitudinally, the fluid in chamber 420 will be forced out of port 302, through conduit 382, check valve 398 and into conduit 404. Fluid from the circuit will be allowed to enter via conduit 402, to conduit 389, through check valve 396, into port 304, and accumulating in chamber 422.

Claims: An apparatus for draining a high pressure sampler bottle (4), which apparatus comprises a first conduit (106) connected between a fluid reservoir (102) and the sampler bottle (4); a first pump (110) in said first conduit, the pump having an output (114) and an input (112) port, said input port of said pump being connected to said reservoir and the output of said pump being connected to said sampler bottle (4); an output conduit leading from said sampler bottle (4); a first valve (134) placed in said output conduit; a sample vessel (122) receiving said output conduit, said sample vessel having a discharge conduit (140) which leads back into said first conduit; a second valve (138) placed in said discharge conduit; and means (141), located in line with said discharge conduit, for pumping the fluid from said sample vessel (122) to said first conduit (106). Apparatus according to claim 1, further comprising a third conduit (144), with one end of said third conduit being connected (146) to said first conduit (106), and the other end of said conduit being connected to said sample vessel; and a third valve (150) located in the line of said third conduit. Apparatus according to claim 2, further comprising means (156;162;160) for gauging the pressure of said first, output and third conduit line; and means (164) for evacuating air and fluid from the conduit between said sampler bottle and said sample vessel. Apparatus according to claim 1,2 or 3, wherein said means (141) for pumping said fluid from said sample vessel to said first conduit includes a pump (141); a direct conduit (140) feeding into said pump; a bypass conduit (172) leading from said direct conduit, feeding into said first conduit (106); a relief valve (165), placed in said bypass conduit; an output conduit leading from said pump; and a valve (143) operable between an open and close position, placed in said output conduit. Apparatus according to claim 4, further comprising first means (156), connected to said first conduit (106), for gauging the pressure in said conduit; a relief conduit (144), with a fourth valve (150), connected to said first conduit upstream of sampler bottle; second means (160), connected to said output conduit, for gauging pressure within said conduit lines; a fifth valve (166) located in stream with discharge conduit line (140), with an output line leading from said fifth valve leading to a discharge vessel (170) for receiving excess fluid; and third means (162), connected to said discharge line (140), for gauging pressure within said conduit line. A method of draining a high pressure sampler bottle wherein there is used an apparatus as claimed in any of claims 1 to 5.

Inventors: RINGGENBERG PAUL D, SCHULTZ ROGER L, RINGGENBERG, PAUL D., SCHULTZ, ROGER L.
Applicants: HALLIBURTON CO, HALLIBURTON COMPANY
Application year: 1992
Main classification: E21B49
IPC codes: E21B49