Patent Application
20100154529
This patent relates generally to sampling and analyzing formation fluids and, more particularly, to methods and apparatus to evaluate subterranean formations.
During production operations, the temperature and pressure at which fluid extracted from a subterranean formation is maintained affects the phase of the fluid as well as the magnitude of precipitated asphaltenes, production equipment, etc. In particular, as the pressure of an unsaturated formation fluid decreases, asphaltenes that were once dissolved in the formation fluid begin to precipitate. Precipitated asphaltenes have been known to clog wells, flowlines, surface facilities and/or subsurface facilities. However, the temperature and pressure of the fluid as it is brought to the surface may be controlled to minimize some of the adverse effects of asphaltenes as well as phase changes during production operations.
To identify the asphaltene onset pressure and the bubble point of a formation fluid, known techniques rely heavily on laboratory analysis. While such laboratory analysis may provide accurate results in some instances, to do so the sample must be representative of the formation fluid and be maintained at reservoir conditions while being transported to the laboratory. Additionally, laboratory analysis does not provide real-time results.
An example method of evaluating a subterranean formation includes, obtaining a first sample from a first wellbore location. Additionally, the example method includes obtaining a second sample from a second wellbore location different than the first wellbore location. Further, the example method includes mixing the first sample with the second sample in a flowline to obtain a substantially homogenous mixture. Further still, the example method includes measuring a parameter of the mixture to evaluate the subterranean formation.
An example method of identifying an asphaltene onset pressure of a mixed fluid obtained from a subterranean formation includes obtaining a mixed fluid from the subterranean formation. Additionally, the example method includes changing a pressure of the mixed fluid. Further, the example method includes identifying the asphaltene onset pressure to limit or eliminate precipitation of asphaltenes during sampling or production.
Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify the same or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and/or conciseness. Additionally, several examples have been described throughout this specification. Any features from any example may be included with, a replacement for, or otherwise combined with other features from other examples.
The example methods and apparatus described herein can be used to evaluate subterranean formations. In particular, the example methods and apparatus described herein may be advantageously utilized to understand how different production zones, which have fluids with varying composition, affect production operations. Specifically, the examples described herein involve obtaining samples from a plurality of wellbore locations and identifying parameters of the fluid to optimize a production strategy.
In one described example, a probe assembly obtains a first sample from a first wellbore location and then obtains a second sample from a second wellbore location. In particular, the probe assembly obtains fluid from a first wellbore location, which is then pumped through a flowline where a sensor determines a contamination level of the fluid and if the fluid is a single phase. Once it is determined that the fluid from the first wellbore location is acceptable, the fluid is routed to a bypass line. Similarly, the probe assembly then obtains fluid from a second wellbore location, which is then pumped through the flowline where the sensor determines a contamination level of the fluid and if the fluid is a single phase. Once it is determined that the fluid from the second wellbore location is acceptable, the fluid is routed to the bypass line. In some examples, a flow meter may control a ratio of the fluid from the first wellbore location relative to the fluid from the second wellbore location.
After the fluid samples from the different wellbore locations are in the bypass line, a pump mixes or circulates the fluid samples to obtain a substantially homogeneous mixture. A pressure control unit then decreases the pressure of the mixture to determine phase behavior of the mixture and/or to identify the temperature and/or pressure at which particles (e.g., asphaltenes or bubbles) appear in the fluid. In particular, as the pressure of the mixture is reduced, a particle detector detects the presence of particles in the fluid and a fluid measurement unit differentiates between the different particles. Generally, the temperature and pressure at which a bubble (i.e., a separating gas phase) is initially detected in the fluid is associated with a bubble point. Similarly, the temperature and pressure at which a precipitated asphaltene (i.e., a separating solid phase) is initially detected in the fluid is associated with an asphaltene onset pressure. After the sampling operation is performed, the pressure control unit may increase the pressure in the bypass line to redissolve the particles (e.g., asphaltene, bubbles, etc.) in the formation fluid.
The example wireline tool 100 also includes a formation tester 114 having a selectively extendable fluid admitting assembly 116 and a selectively extendable tool anchoring member 118 that are respectively arranged on opposite sides of the elongated body 108. The fluid admitting assembly 116 is configured to selectively seal off or isolate selected portions of the wall of the wellbore 102 to fluidly couple the adjacent formation F and draw fluid samples from the formation F. The formation tester 114 also includes a fluid analysis module 120 through which the obtained fluid samples flow. The fluid may thereafter be expelled through a port (not shown) or it may be sent to one or more fluid collecting chambers 122 and 124, which may receive and retain the formation fluid for subsequent testing at the surface or a testing facility.
In the illustrated example, the electronics and processing system 106 and/or the downhole control system 112 are configured to control the fluid admitting assembly 116 to draw fluid samples from the formation F and to control the fluid analysis module 120 to measure the fluid samples. In some example implementations, the fluid analysis module 120 may be configured to analyze the measurement data of the fluid samples as described herein. In other example implementations, the fluid analysis module 120 may be configured to generate and store the measurement data and subsequently communicate the measurement data to the surface for analysis at the surface. Although the downhole control system 112 is shown as being implemented separate from the formation tester 114, in some example implementations, the downhole control system 112 may be implemented in the formation tester 114.
As described in greater detail below, the example wireline tool 100 may be used in conjunction with the example methods and apparatus described herein to determine parameters of the formation fluid. Such parameters may include, for example, an asphaltene onset pressure, a bubble point and/or a dew point of a mixed fluid obtained from, for example, the formation F. Information obtained using the example methods and apparatus described herein may be later advantageously used to limit and/or eliminate precipitation of asphaltenes and/or phase changes during production or sampling operations. In some examples, the formation tester 114 may include one or more sensors, fluid analyzers and/or fluid measurement units disposed adjacent a flowline and may be controlled by one or both of the downhole control system 112 and the electronics and processing system 106 to determine one or more parameters and/or characteristics of the fluid samples extracted from, for example, the formation F.
While the example methods and apparatus to evaluate a subterranean formation are described in connection with a wireline tool such as that shown in
In operation, in some examples, the probe assembly 202 draws a first sample of fluid from a first wellbore location (e.g., a first production zone) and a second sample of fluid from a second wellbore location (e.g., a second production zone), which is different than the first wellbore location. A flow meter 210 measures a ratio of a volume of the first sample relative to a volume of the second sample in a flowline 212. The ratio may be representative of an amount of hydrocarbons associated with each of the different wellbore locations. After the first and second fluid samples are in the flowline 212, the pump 208 circulates and/or mixes the samples together to obtain a substantially homogeneous fluid.
The formation sampling tool 200 includes a pressure control unit 214 to change the pressure of the mixture (e.g., the first sample and the second sample) in the flowline 212. In practice, after one of the sensors 216 has identified that the mixture is a substantially homogeneous fluid, the pressure control unit 214 decreases the pressure in the flowline 212 and a particle detector 217 analyzes the mixture to identify the presence of particles in the mixture such as, for example, precipitated asphaltenes or bubbles. Identifying the presence of particles may be advantageously utilized to determine an asphaltene onset pressure, a bubble point and/or a dew point of the mixture.
The formation sampling tool 200 includes one or more fluid sensors to measure characteristics of the fluids drawn into the formation sampling tool 200 and/or to differentiate between particles in the mixture. More specifically, in the illustrated example, the formation sampling tool 200 is provided with a fluid measurement unit 218 to measure one or more parameters or characteristics of formation fluids. The formation fluids may comprise at least one of a heavy oil, a bitumen, a gas condensate, a drilling fluid, a wellbore fluid or, more generally, a fluid extracted from a subsurface formation. The fluid measurement unit 218 may be implemented using, for example, a light absorption spectrometer having a plurality of channels, each of which may correspond to a different wavelength. Thus, the fluid measurement unit 218 may be used to measure spectral information for fluids drawn from a formation. In other implementations, the fluid measurement unit 218 may be implemented using a flowline imager, a VIS/NIR spectrometer, a composition fluid analyzer, an in-situ fluid analyzer, a VIS spectrometer, an NIR spectrometer or any other suitable spectrometer. In operation, if the fluid measurement unit 218 is implemented using a flowline imager, after the particle detector 217 has identified the presence of the particles in the mixture, the fluid measurement unit 218 differentiates between the particles. In particular, the fluid measurement unit 218 classifies each particle as, for example, a precipitated asphaltene or a bubble. Additionally or alternatively, the fluid measurement unit 218 may determine a quantity of precipitated asphaltenes and/or bubbles in the mixture.
The formation sampling tool 200 is also provided with the one or more sensors 216 to measure pressure, temperature, density, fluid resistivity, viscosity, and/or any other fluid properties or characteristics of, for example, the mixture. While the sensors 216 are depicted as being in-line with a flowline 220, one or more of the sensors 216 may be used in other flowlines 212, 222, and 224 within the example formation sampling tool 200.
The formation sampling tool 200 may also include a fluid sample container or store 226 including one or more fluid sample chambers in which formation fluid(s) recovered during sampling operations can be stored and brought to the surface for further analysis and/or confirmation of downhole analyses. In other example implementations, the fluid measurement unit 218 and/or the sensors 216 may be positioned in any other suitable position such as, for example, between the pump 208 and the fluid sample container or store 226.
To store, analyze and/or process test and measurement data (or any other data acquired by the formation sampling tool 200), the formation sampling tool 200 is provided with a processing unit 228. The processing unit 228 may be generally implemented as shown in
To store machine readable instructions (e.g., code, software, etc.) that, when executed by the processing unit 228, cause the processing unit 228 to implement measurement processes or any other processes described herein, the processing unit 228 may be provided with an electronic programmable read only memory (EPROM) or any other type of memory (not shown). To communicate information when the formation sampling tool 200 is downhole, the processing unit 228 is communicatively coupled to a tool bus 232, which may be communicatively coupled to a surface system (e.g., the electronics and processing system 106).
Although the components of
In operation, the probe assembly 202 (
Once the first sample is retained in the bypass line 304, the first valve 314 is opened and the probe assembly 202 (
To measure a volume and/or quantity of a sample in the bypass line 304, the example apparatus 300 is provided with a flow meter 322. In operation, after the first valve 314 has closed and the second valve 316 is opened to enable fluid to flow into the bypass line 304, the flow meter 322 measures the amount of fluid that enters the bypass line 304. In particular, as the sample is flowing into the bypass line 304, the flow meter 322 measures the fluid volume to control a ratio of the first sample relative to the second sample in the bypass line 304. In some examples, the ratio may be representative of an amount of hydrocarbons associated with each of the first and second wellbore locations. The ratio may be, for example, one-to-one (e.g., 1:1), two-to-one (e.g., 2:1), one-to-two (e.g., 1:2), etc. After the predetermined ratio and/or volume of the samples are in the bypass line 304, the second valve 316 closes to retain the mixture in the bypass line 304.
To circulate and/or mix the first and second samples in the bypass line 304, the example apparatus 300 is provided with a pump 324. In operation, after the predetermined ratio and/or volume of the samples are retained in the bypass line 304, the pump 324 pumps the mixture (e.g., the first sample and the second sample) in a direction generally indicated by arrows 326, 328, 330 and 332. However, in other examples, the pump 324 may pump the mixture in a direction opposite the direction generally indicated by the arrows 326, 328, 330 and 332.
To identify when a density and/or a viscosity of the mixture is substantially stable (e.g., a homogeneous mixture), the example apparatus 300 is provided with a density sensor 334 and a viscosity sensor 336. In operation, when the first sample and/or the second sample initially enter the bypass line 304, the density and/or the viscosity of the fluid may be relatively unstable, which leads to inaccurate measurements. However, as the pump 324 circulates and/or mixes the fluid in the bypass line 304, the density and/or the viscosity of the fluid substantially stabilizes, which tends to lead to more accurate measurements. Generally, the density and/or the viscosity sensors 334 and 336 may be advantageously utilized to identify when a sampling analysis may begin to obtain relatively accurate measurements.
Asphaltenes are categorized as components that are insoluble in n-alkanes such as, for example, n-pentane or n-heptane, and soluble in toluene. In some examples, formation fluids (e.g., crude oils) may exist in formations at a pressure higher than a bubble point pressure (e.g., understaturated). In such instances, during production, unless preventative steps are taken, the pressure of the formation fluid may decrease to an asphaltene onset pressure (e.g., asphaltene precipitation onset pressure), which enables previously dissolved asphaltenes to precipitate out of the formation fluid and deposit in the flowlines, etc. While some practical uses of precipitated asphaltenes exist, during production and/or sampling operations, asphaltenes can clog wells, flowlines, surface facilities and/or subsurface facilities. To limit and/or eliminate the effects of asphaltenes during production and/or sampling operations, the examples described herein may be advantageously used to identify the asphaltene onset pressure, the bubble point and/or the dew point of the fluid in the bypass line 304. As a result, during production, a pressure and/or a temperature of the formation fluid extracted from the formation F may be controlled to minimize the adverse effects of asphaltenes on reservoir performance.
To decrease the pressure of the fluid in the bypass line 304, the example apparatus 300 is provided with a pressure control unit 338. As discussed above, as the pressure and/or the temperature of the formation fluid changes, previously dissolved asphaltenes may precipitate. Additionally, as the pressure and/or temperature of the formation fluid changes, a phase of the formation fluid may change (e.g., a liquid phase may change to a partially liquid phase and a partially gaseous phase or to an entirely gaseous phase).
To identify the asphaltene onset pressure, the bubble point and/or the dew point, known techniques typically rely heavily on laboratory analysis. While these techniques may provide accurate results in some instances, to do so, the sample must be representative of the formation fluid and be maintained at reservoir conditions while being transported to the laboratory, which poses significant challenges. In contrast, the examples described herein enable real-time downhole measurements to be obtained from the formation fluid. In particular, after the fluid retained in the bypass line 304 is a substantially homogenous fluid, the pressure control unit 338 decreases the pressure of the mixture and a particle detector 340 may be advantageously utilized to detect particles in the mixture. In some examples, the particle detector 340 may include a near-infrared (NIR) light source on a side of, for example, the fourth flowline section 312 and a fiber-optic sensor opposite the NIR light source. In operation, the NIR light source emits light through the fluid in the fourth flowline section 312 and the fiber-optic sensor detects the light. As the pressure decreases and particles (e.g., precipitated asphaltenes or bubbles) begin to appear in the fluid, the light transmitted through the fluid is scattered, which reduces and/or changes the intensity and/or transmittance power of the light received by the fiber-optic sensor. This change is indicative of an asphaltene onset pressure, precipitation of asphaltenes, bubbles in the fluid, a bubble point and/or a dew point of the mixture.
Once the particle detector 340 detects particles in the fluid, a pressure sensor 342 and a temperature sensor 344 measure the pressure and the temperature of the fluid, respectively. The particles identified by the particle detector 340 may be precipitated asphaltenes and/or bubbles and, thus, measuring the pressure and/or the temperature at the point at which the particles were initially identified may be advantageously utilized to determine the asphaltene onset pressure and/or the bubble point.
To differentiate between the different particles in the fluid, the example apparatus 300 is provided with a fluid measurement unit 346. In particular, the fluid measurement unit 346 may differentiate between precipitated asphaltenes and bubbles. Additionally, the fluid measurement unit 346 may be advantageously utilized to determine a quantity of precipitated asphaltenes in the mixture. The fluid measurement unit 346 is provided with a window 348 (e.g., an optical window) that is substantially adjacent a surface 350 of the second flowline section 308. The window 348 may be implemented using any suitable material such as a scratch resistant material (e.g., a sapphire material). The window 348 may be substantially flush with the surface 350 or the window 348 may be partially positioned within the second flowline section 308.
In operation, to evaluate a subterranean formation using the example apparatus 300, initially, the probe assembly 202 engages the formation at a first wellbore location and a pump 352, which may be used to implement the pump 208 of
After the sensor 320 determines that the fluid from the first wellbore location is acceptable, the first valve 314 actuates to the closed position and the second valve 316 actuates to an open position. The second valve 316 may remain in the open position until a predetermined amount of fluid has entered the bypass line 304, at which point the second valve 316 actuates to the closed position. In particular, the second valve 316 may remain in the open position until the flow meter 322 determines that a predetermined amount of fluid has entered the bypass line 304.
After the sample from the first wellbore location has entered the bypass line 304, the pump 324 circulates the fluid in a direction generally indicated by the arrows 326, 328, 330 and 332 until the density sensor 334 and/or the viscosity sensor 336 have identified that the density and/or the viscosity of the fluid is substantially stable (e.g., a homogeneous mixture) and/or until fluid remaining in the bypass line 304 from previous testing is substantially replaced by the sample from the first wellbore location. After it is determined that the fluid is a substantially homogeneous mixture, the pressure control unit 338 decreases the pressure of the fluid in the bypass line 304 until, for example, the particle detector 340 detects particles in the fluid, which may be indicative of precipitated asphaltenes and/or bubbles. The pressure and temperature sensors 342 and 344 measure the pressure and temperature of the fluid, respectively, and then the fluid measurement unit 346 differentiates between precipitated asphaltenes and/or bubbles in the fluid. The pressure and temperature at which precipitated asphaltenes and/or bubbles are identified in the fluid may be advantageously utilized during production and/or sampling operations to design production strategies that avoid or mitigate asphaltene deposition or, more generally, phase separation of extracted formation fluid. After the measurements are obtained from the fluid, the pressure control unit 338 increases the pressure in the bypass line 304 to redissolve the asphaltenes in the fluid.
To better understand how different production zones, which having fluids with varying composition, affect production, the probe assembly 202 is moved to a second wellbore location and the pump 352 pumps fluid (e.g., formation fluid) from the second wellbore location through the flowline 302 in a direction generally indicated by the arrow 354. As the fluid moves through the flowline 302, the first valve 314 is actuated to an open position and the sensor 320 identifies if the contamination level of the fluid is equal to or below a predetermined amount. Additionally, as the fluid moves through the flowline 302, the sensor 320 may identify if the fluid is single phase or multiple phases. After the sensor 320 determines that the fluid from the second wellbore location is acceptable, the first valve 314 actuates to the closed position and the second valve 316 actuates to the open position to enable fluid from the second wellbore location to enter the bypass line 304, which also contains fluid from the first wellbore location.
The flow meter 322 measures the volume of fluid as the fluid from the second wellbore location flows into the bypass line 304. In particular, the flow meter 322 is advantageously utilized to control a ratio of fluid from the first wellbore location relative to fluid from the second wellbore location. After the flow meter 322 has identified that the desired ratio is achieved, the second valve 316 actuates to the closed position.
The pump 324 then circulates and/or mixes the fluids from the first and second wellbore locations in a direction generally indicated by the arrows 326, 328, 330 and 332 until the density sensor 334 and/or the viscosity sensor 336 have identified that the density and/or the viscosity of the mixture is substantially stable (e.g., a homogeneous mixture).
After it is determined that the mixture is a substantially homogeneous mixture, the pressure control unit 338 decreases the pressure of the mixture in the bypass line 304 until, for example, the particle detector 340 detects particles in the mixture. The pressure and temperature sensors 342 and 344 then measure the pressure and the temperature of the mixture, respectively. Additionally, the fluid measurement unit 346 may differentiate between precipitated asphaltenes and/or bubbles in the mixture. The pressure and temperature at which precipitated asphaltenes and/or bubbles are identified in the mixture may be advantageously utilized during production and/or sampling operations to design production strategies that avoid or mitigate asphaltene deposition or, more generally, phase separations of extracted formation fluid. After the measurements are obtained from the mixture, the pressure control unit 338 increases the pressure in the bypass line 304 to redissolve the asphaltenes into the mixture and then the third valve 318 is actuated to the open position to enable the mixture to flow to the flowline 302.
The example apparatus 400 includes a sensor 402 to identify if the contamination level is sufficiently low and if the fluid is single phase as the fluid flows through the flowline 302. The sensor 402 may be utilized to implement the sensor 320 of
To decrease the pressure of the fluid in the bypass line 304, the example apparatus 300 is provided with a pump unit 408 that may be used to implement the pressure control unit 338 of
To identify the presence of particles in the fluid in the bypass line 304, the example apparatus 400 is provided with a scattering detector 424 that may be used to implement the particle detector 340 of
The example method 500 may be used to draw and analyze formation fluids to evaluate the subterranean formation using, for example, the formation sampling tool 200 of
However, if the processing unit 228 (
The probe assembly 202 (
However, if the processing unit 228 (
The pump 208 (
However, if the processing unit 228 (
However, if the particle detector 217 (
Once the particle detector 217 (
Similarly, once the particle detector 217 (
After the measurements have been obtained from the sample in the bypass line 304, the pressure control unit 214 (
The processing unit 228 (
The processing unit 228 (
The processor platform P100 of the example of
The processor P105 is in communication with the main memory (including a ROM P120 and/or the RAM P115) via a bus P125. The RAM P115 may be implemented by dynamic random-access memory (DRAM), synchronous dynamic random-access memory (SDRAM), and/or any other type of RAM device, and ROM may be implemented by flash memory and/or any other desired type of memory device. Access to the memory P115 and the memory P120 may be controlled by a memory controller (not shown).
The processor platform P100 also includes an interface circuit P130. The interface circuit P130 may be implemented by any type of interface standard, such as an external memory interface, serial port, general purpose input/output, etc. One or more input devices P135 and one or more output devices P140 are connected to the interface circuit P130.
Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.
