Apparatus for analyzing oil well production fluid

An improved apparatus and method for analyzing oil well production fluid that includes a flow pipe through which production fluid normally flows, a test pipe defining an elongate vertical test chamber, valves to selectively intermittently bypass fluid flowing through the flow pipe into the test pipe to fill the chamber with a sample of production fluid. The apparatus includes devices to measure and record the rate of flow of the production fluid flowing through the flow pipe and to measure and record the temperature, pressure, weight and the capacitance of the sample in the chamber for comparative use with earlier recorded base measurements to calculate and record the net volumes of the oil, gas and water fractions in the production fluid.

BACKGROUND OF THE INVENTION 
The present invention has to do with the testing and/or analyzing of fluid 
mixtures flowing through fluid conducting lines and is particularly 
concerned with an improved apparatus that is particularly suited for 
analyzing and determining the net volumes of oil, gas and water of 
production fluid flowing from oil wells. 
The present invention has to do with certain notable improvements in that 
apparatus for testing and analyzing fluid mixtures that is the subject 
matter of and that is fully disclosed in my earlier issued U.S. Pat. No. 
3,911,256, issued Oct. 7, 1975. The full disclosure of U.S. Pat. No. 
3,911,256 is incorporated herein by reference and will hereinafter be 
referred to as the patent. 
To the best of my knowledge and belief, the patent is the most pertinent 
prior art and was representative of the state of the art at the time of my 
present invention. 
In the patent the need for determining the net oil content of the 
production fluids issuing from oil wells is fully and clearly set forth. 
The patent also describes that old method and apparatus employed to test 
oil well production fluids to determine the net oil content thereof that 
was, and remains, the most common and widely used method and apparatus for 
determining the net oil content of oil well production fluid throughout 
the petroleum industry at the time of the invention of the patent 
apparatus. That old and common method and apparatus for testing production 
fluid is characterized by the provision and use of three-phase separator 
tanks in and through which production fluids issuing from oil wells are 
caused to flow at a sufficiently slow rate to allow the force of gravity 
to cause free water in the production fluid to settle to the bottoms of 
the tanks, for the lighter oils to rise to the top of the settled water 
and for free gases to rise in the tanks above the oil. The volumes of 
separated water, gas and oil in the tanks are measured and recorded and 
samples of the separated oil (wet oil) are extracted from the tanks and 
tested to determine the net volumes of the water, gas and oil fractions 
thereof. 
In the apparatus of the referred-to patent, the use of a three-phase 
separator tank is eliminated and in its stead the apparatus includes an 
elongate vertical test chamber that is filled with and holds a sample of 
production fluid to be tested. That apparatus operates to read and record 
the flow rate, temperature, pressure and weight of the sample of fluid in 
the chamber and operates to alter the pressure on the sample in the 
chamber to expand or compress the gas in the chamber and to vary the 
volume of the sample in the course of calculating and determining the net 
gas content of the sample. The net oil and/or net water content of the 
sample is determined by subtracting the measured volume and weight of the 
gas from the total volume and weight of the sample to determine the net 
volume and weight of the remaining water and oil in the sample and 
comparing the measured volume and weight of the water and oil with base or 
reference measurements of the volume and weight earlier obtained from a 
prepared anhydrous sample of the oil. The net volume of oil in the sample 
being tested is established by subtracting the measured weight thereof 
from the measured weight of a like volume of anhydrous oil. 
The apparatus of the referenced patent has proven to be effective to test 
and determine the net oil content of oil well production fluid containing 
oil that has a specific gravity that is notably different from the 
specific gravity of water. As the specific gravity of oil in production 
fluid tested nears the specific gravity of water, the difficulty and time 
required to calculate and determine the net content of oil increases at an 
exponential rate and the accuracy and dependability of the apparatus 
diminishes in a like manner. That apparatus is rendered totally 
ineffective when the specific gravity of the oil is the same as water. In 
practice, the apparatus of the referred-to patent cannot reliably and 
dependably analyze oil well production fluid containing oil the API 
gravity of which is between 14 and 7 degrees API. Accordingly, the 
apparatus of my referred-to patent is not suitable for use in analyzing 
oil well production fluids containing those heavy crude oils that 
characterize the production from most oil deposits throughout the world. 
In addition to the foregoing, the apparatus which is the subject matter of 
my above referred-to patent has proven to be such that it requires closer 
monitoring and field service than many of those who own, maintain and 
service oil field production equipment are willing to be burdened with. 
This is due to the fact that the apparatus includes many mechanical parts 
that are subject to leaking and failing and that must be periodically 
serviced, repaired and/or replaced. For example, the patented apparatus 
includes the flow meter, four large fall valves, a double-acting hydraulic 
cylinder and piston unit and link means for operating those valves; a 
source of motive hydraulic fluid and an electrically operated four-way 
valve for controlling operation of the cylinder and piston unit; a 
motor-driven high-pressure liquid pump with a related check valve and an 
electrically operated plug valve for introducing and removing liquid from 
the test chamber. It is an accepted rule-of-thumb that the likelihood of 
mechanical failure in such apparati increases exponentially with the 
number of mechanical parts included. 
OBJECTS AND FEATURES OF THE INVENTION 
It is an object of my invention to provide an improved apparatus for 
testing and analyzing oil production fluid to determine the net oil 
content thereof that overcomes many of the shortcomings that are to be 
found in and that characterize apparatus provided by the prior art for 
analyzing such fluids to determine the net oil content thereof. 
It is an object and a feature of my invention to provide a novel and 
improved apparatus for the purpose set forth above which is such that the 
gas, water and oil fractions or components of a sample of production fluid 
being analyzed are not and need not be separated or otherwise worked upon 
in the course of analyzing and determining the net content of the oil, gas 
and/or water thereof. 
Yet another object and feature of my invention is to provide a novel and 
improved apparatus of the general character referred to which is not 
affected by the specific gravity of the oil contained in the sample fluid 
being tested and that can quickly and accurately determine the net oil 
content of oil well production fluid tested and analyzed without regard to 
the specific gravity of the oil therein. 
Still another object and feature of my invention is to provide a novel 
apparatus of the general character referred to above that is extremely 
easy and economical to make and that is highly dependable and durable in 
operation. 
It is an object of the invention to provide an apparatus of the character 
referred to above the mechanical parts of which include three valves and a 
valve operator to intermittently simultaneously operate the valves between 
opened and closed positions. 
Yet another object and feature of my invention is to provide an apparatus 
of the general character referred to that includes an elongate vertical 
test pipe connected with and extending between a pair of normally closed 
valves and defining an elongate vertical test chamber, a flow pipe through 
which production fluid normally flows and in which a normally open valve 
is engaged, and valve actuator means to selectively open the normally 
closed valves and to close the normally open valve to bypass production 
fluid flowing through the flow pipe into and through the test pipe to fill 
the chamber with a sample of production fluid to be analyzed. 
A further object and feature of my invention is to provide an apparatus of 
the character referred to including a flow meter in the flow pipe to read 
the flow rate of production fluid flowing therethrough and to transmit a 
corresponding flow rate signal; and, devices at the test pipe to read the 
pressure, temperature, weight and capacitance of a sample of production 
fluid in the test chamber and to transmit corresponding pressure, 
temperature, weight and capacitance signals. 
Finally, it is an object and feature of my invention to provide an 
apparatus of the general character referred to above that includes a 
computer including an input section or means receiving and converting the 
pressure, temperature, weight and capacitance signals transmitted by the 
apparatus into corresponding feedback data, a memory section or means in 
which previously established control data is stored, a control section or 
means to receive and process feedback and control data received thereby 
from the input and memory means; and, an output section or means that 
translates and presents processed data and information for use. 
The foregoing and other objects and features of my invention will be 
apparent and will be fully understood from the following detailed 
description of one typical preferred form and embodiment of my invention 
throughout which description reference is made to the accompanying 
drawings.

DETAILED DESCRIPTION OF THE INVENTION 
The apparatus A, shown in the drawing, is engaged between and connected 
with related outlet and inlet ends of upstream and downstream sections 10 
and 11 of a production pipeline through which oil well production fluid 
produced by a well being monitored by the apparatus A flows at a normal 
rate and under normal pressure. 
In practice, the pipe sections 10 and 11 can be parts of a valve controlled 
manifold system that is connected with and handles the production from a 
plurality of oil wells that are monitored by the apparatus and that is 
automatically operated to sequentially and intermittently conduct the 
production fluid from each of those oil wells into and from the apparatus, 
as desired and as circumstances require. 
Since the novelty and spirit of this invention is in no way altered or 
affected by the number of wells it might be used to monitor or by the 
particular means by which the production fluid(s) from one or more oil 
wells might be conducted to and from it, I have elected not to unduly 
burden this disclosure with illustration and/or description of any one 
particular structure or means to handle inflowing and outflowing 
production fluid, other than to show the production pipeline sections 10 
and 11 noted above. 
The apparatus A first includes an elongate flow pipe 12 extending between 
and connected with the production pipeline sections 10 and 11 and through 
which oil well production fluid normally flows. 
The flow pipe 12 has a normally open flow control valve V engaged therein. 
The valve V is selectively closed and opened to stop and start the flow of 
production fluid through the pipe 12, as will here and after be described. 
In practice, a flow meter F can be and is preferably engaged in the flow 
pipe 12, downstream from the valve V. The flow meter F reads the rate of 
flow of production fluid through the pipe and transmits a corresponding 
flow rate signal. 
In practice, the flow meter F is preferably one of those types of flow 
meters that has no moving parts and that is trouble-free and 
maintenance-free when used in the harsh environments (oil fields) in which 
the apparatus A is used. One type of flow meters that I have 
advantageously employed is a magnetic inductance type flow meter. 
The apparatus A next includes an elongate vertically extending test pipe 20 
with a lower inlet or upstream end portion and an upper outlet or 
downstream end portion. The pipe 20 defines an elongate, vertical, 
cylindrical in cross-section, test chamber 21. 
The lower end portion of the pipe 20 has an inlet port 22 connected with 
the downstream side of a normally closed inlet valve V1. The other or 
upstream side of the valve V1 is suitably connected with the downstream 
end of the upstream section 10 of the production pipeline. 
The lower end of the pipe 20 and the chamber 21 are closed by a suitable 
closure structure 23 that includes a lower rod support for insulator 24 of 
dielectric material. The structure 23 preferably includes a mounting 
flange on the pipe and a plate suitably fastened to the flange. The plate 
carries the rod support or insulator 24. 
The lower end of the pipe 20 next and finally includes a port 25 that 
communicates with the lower end of the chamber 21 and in and through which 
a part of a fluid pressure sensing device D extends. The device D is 
preferably mounted on and carried by the pipe at the exterior thereof. 
The upper end portion of the pipe 20 is similar to the lower end portion 
thereof and, as shown, has an inlet port 22' suitably connected with the 
upstream side of a normally closed outlet valve V2. The other or 
downstream side of the valve V2 is suitably connected with the upstream 
end of the downstream section 11 of the production pipeline. 
The upper end of the pipe 20 and the chamber 21 are closed by a suitable 
closure structure 23', similar to the closure structure 23, and that 
includes an upper rod support or insulator 24' of dielectric material. 
The upper end portion of the pipe 20, like the lower end portion thereof, 
includes a port 25' that communicates with the upper end of the chamber 21 
and through which a part of a fluid pressure sensing device D', similar to 
the device D, is engaged. The device D', like the device D, is shown 
mounted at the exterior of the pipe 20. 
The apparatus next includes a valve actuating means G that operates to 
simultaneously close the valve V and open the valves V1 and V2 to shut off 
the flow of production fluid through the pipe 12 and establish flow of 
that fluid through the pipe 20, to fill the chamber 21 with the fluid and 
to thereafter simultaneously open the valve V and close the valves V1 and 
V2 to trap a fluid sample in the chamber 21, without stopping or 
interrupting normal flow of production fluid in and through the pipeline 
with which the apparatus is connected. 
The fluid filling and trapped in the chamber 21 in the manner set forth 
above, establishes a fluid sample of predetermined vertical and volumetric 
extent and that is under the normal or working pressure of the production 
fluid flowing through the pipeline is under. 
It is to be noted that each time the several valves are operated in the 
manner set forth above, a previously tested fluid sample in the chamber 21 
is displaced or moved downstream therefrom and is replaced by a new 
yet-to-be-tested fluid sample. 
In practice, the several valves V, V1 and V2 are preferably alike. In the 
case illustrated, they are ball valves with operating stems accessible at 
their exteriors and that are actuated between open and close positions by 
rotation of the stems through 90.degree.. The valves V1 and V2 are in 
vertical spaced relationship from each other and are arranged with their 
stems in axially aligned opposing relationship with each other. The valve 
V is laterally spaced from the center line along which the stems of the 
valves V1 and V2 extend and is arranged with its stem projecting toward 
the noted center line and on an axis perpendicular to it. 
The valve actuating means G that I prefer to employ includes a right angle 
gear box B with an input shaft opposing and concentric with the stem of 
the valve V and with an output shaft axially aligned with and having lower 
and upper ends opposing the stems of the valves V1 and V2 and which are 
drivingly connected therewith by drive shafts 31 and 32. The drive shafts 
31 and 32 are preferably provided with Universal joints 33 and 34, having 
splined coupler parts and that serves to compensate for misalignment and 
for thermal expansion and contraction of the parts of the apparatus 
related to them. 
The valve actuating means G next includes a prime mover or drive motor H 
with a drive shaft with opposite ends projecting toward and aligned with 
the stem of the valve V and the input shaft of the gear box B. The motor H 
is shown mounted to a part of a frame for the apparatus and can be 
connected with its related valve stem and gear box input shaft by 
intermediate shafts or, as shown, the end of the drive shaft related to 
the stem of the valve V can be directly connected to that valve stem and 
the end of the drive shaft related to the input shaft of the gear box can 
be connected thereto by means of a suitable Universal joint 35 (with a 
splined coupling part). 
The motor H can be an electric, hydraulic or pneumatic motor as desired or 
as circumstances require and is selectively operated to turn 90.degree. 
and to thereby effect simultaneous actuation of the valves V, V1 and V2, 
between their opened and closed positions as required during normal and 
intended operation and use of the apparatus A. 
The apparatus A next includes pressure and temperature sensing devices P 
and T suitably mounted on the exterior of the pipe 20 and having parts 
projecting through related ports formed in the pipe 20 and into the 
chamber 21. The devices P and T operate to sense the pressure and the 
temperature of the fluid sample in the chamber and to transmit 
corresponding pressure and temperature signals. The devices P and T can be 
any one of those several different kinds of standard pressure and 
temperature sensing devices one might elect to use when practicing my 
invention. 
The above-noted pressure sensing devices D and D' at the upper and lower 
ends of the pipe 20 are parts of a density sensing means N that operates 
to measure the weight or density of the fluid sample and that transmit a 
corresponding density signal. 
The devices D and D' can vary widely in form and are shown as simple 
diaphragm structures with pressure input sides exposed to the fluid sample 
within the chamber 21 and pressure output sides exposed to a suitable 
force transmitting fluid medium, such as hydraulic oil. The force output 
sides of the devices D and D' are connected with a comparator and 
translator unit 50 by means of capillary tubes 51 and 51', as clearly 
shown in the drawing. The unit 50 operates to compare the pressures sensed 
by the devices D and D' and to transmit the desired and corresponding 
density signal. 
The device A next includes an elongate vertically extending electrode rod R 
with an outer jacket 55 of insulating material. The jacketed rod is 
positioned centrally within the test pipe 20 in uniform spaced 
relationship with the wall of the pipe 20 and to extend centrally 
throughout the longitudinal extent of the chamber 21. The lower end of the 
rod R is securely held and supported in and by the insulator 24 at the 
bottom of the pipe and chamber 21 and the upper end thereof is securely 
held and supported in and by the insulator 24' at the top of the pipe and 
chamber. 
The rod R and pipe 20 are, in effect, the spaced electrodes of a capacitor 
structure and the fluid sample in the chamber is the dielectric of that 
capacitor structure. Accordingly, the pipe 20, rod R and fluid sample 
establish an effective electrical capacitor. 
The jacket 55 about the rod R prevents the sample short circuiting between 
the rod and the pipe 20. Its dielectric properties are accounted for when 
the dielectric constant of the sample is determined. 
The rod R and test pipe 20 of the noted capacitor structure are connected 
in and with a suitable comparator circuit, such as a bridge circuit, of a 
transmitter unit U that is shown conveniently mounted atop the closure 
structure 23' at the upper end of the pipe 20. A conductor to connect the 
unit U to the rod R can be extended through the closure structure 23', 
between the unit U and rod R, as illustrated in dotted lines. A high 
frequency AC voltage is applied to the bridge in the unit U and the bridge 
operates to measure the capacitance of the fluid sample and to emit or 
transmit a corresponding capacitance electrical signal. 
It is to be noted that the dielectric fluid sample extends throughout the 
longitudinal extent of the chamber 21 and is deposited dimensionally 
uniformly about and between the opposing surfaces of the rod R and pipe 
20. Accordingly, the resistance afforded thereby and read by the unit U is 
the average or mean resistance afforded by the whole of the sample. 
Accordingly, if the gas, water and oil fractions of the sample should 
separate, settle or otherwise become unevenly distributed throughout the 
chamber and about the rod and the pipe, a reading of the resistance or 
capacitance which is the average or mean resistance or capacitance 
afforded by the whole of the sample is attained. 
It is believed apparent that any one of numerous different comparator 
circuits or bridge circuits that are known to exist can be utilized in 
practicing my invention. 
The flow rate, pressure, temperature, density and capacitance signals 
transmitted by the flow meter F, means P, T, N and by the unit U, which 
signals will hereinafter be referred to as feedback signals, are suitably 
translated into corresponding digital or numerical data and, together with 
earlier acquired base data pertaining to the production fluid being 
tested, can be processed or used to calculate the net oil content and the 
net content of the water and gas in the fluid sample. If the data is 
numerically or mathematically calculated, considerable skill and time must 
be expended to attain the desired results. On the other hand, if the data 
is computed digitally, utilizing appropriate computer hardware and 
software, the desired information and/or answers can be attained quickly. 
For example, the data can be processed and the desired information can be 
presented in a matter of minutes rather than hours. Also, when the data is 
computed by means of an appropriate computer, the information and answers 
and all or any part of the data utilized to gain that information and to 
reach those answers can be transmitted by telephone service to a remote 
computer where the data and information can be recorded and put to use, by 
means of a modem. 
In another use of my new apparatus, the transmitted feedback signals are 
stored in a retrievable form by means of or in a simple recording device 
that can be accessed by telephone. When it is timely or desired to record 
and/or process the stored signals or data, the recording device is 
accessed, by telephone, and the data is entered into a central computer 
and thereafter processed. In accordance with the foregoing, it will be 
apparent that large numbers of my apparatus, each serving a number of 
wells and spaced throughout large geographical areas can be monitored and 
managed at a single or central monitoring station. 
In accordance with the above, though I do not make any claim to any 
particular computer hardware and computer software or hardware, such 
hardware and software are important collateral or support means and/or 
equipment used in conjunction with my apparatus to utilize its full useful 
potentials and to most effectively and efficiently realize all that it 
offers. 
In the drawing, I have diagrammatically illustrated the basic components of 
a computer as might be used in conjunction with my apparatus. The computer 
includes an input means 60 which receives the several noted feedback 
signals from the apparatus and converts them into digital form; a memory 
means 61 in which previously obtained and/or prepared base or reference 
data is stored; a control means 62 that compares and processes data 
received from the input and memory means; and, an output section 63 that 
converts the data processed by the control means and presents it in 
readable and useable form. 
To utilize and calculate the data obtained and provided by my apparatus and 
to obtain the information and/or answers sought, the following set of 
basic equations are used: 
EQU Qg=Vg*Fg*Ap 
Where: 
QG=Volumetric flow rate of gas, Ft.sup.3 /sec 
Vg=Velocity of gas, Ft/sec 
Fg=Fraction of gas in pipeline, dimensionless 
Ap=Cross sectional area of pipe, Ft.sup.2 
EQU Qo=V1*Fo*Ap 
Where: 
Qo=Volumetric flow rate of oil, Ft.sup.3 /sec 
V1=Velocity of liquid, Ft/sec 
Fo=Fraction of oil in fluid stream, dimensionless 
Ap=Cross sectional area of pipe, Ft.sup.2 
EQU Qw=V1*Fw*Ap 
Where: 
Qw=Volumetric flow rate of water, Ft.sup.3 /sec 
Fw=Fraction of water in fluid stream, dimensionless 
V1=Velocity of liquid, Ft/sec 
Ap=Cross sectional area of pipe, Ft.sup.2 
Once the volumetric flow rates are established through the pipeline by 
means of the meter F, the volumes of gas and liquid, at standard 
conditions, are calculated using fluid property correlations and pressure 
and temperature measurements established by the devices P and T. These 
corrected volumetric rates are then integrated over the time length of the 
test to give the final test results. 
The fractions of oil, water, and gas are related to each other by three 
simultaneous, linear equations. The three equations are: 
EQU Fo+Fw+Fg=1 (1) 
EQU FoRhoo+FwRhow+FgRhog=Rhos (2) 
EQU FoEo+FwEw+FgEg=Es (3) 
Where: 
Fo=Fraction of oil (dimensionless) 
Fw=Fraction of water (dimensionless) 
Fg=Fraction of gas (dimensionless) 
Rhoo=Density of oil, lbs/in.sup.3 
Rhow=Density of water, lbs/in.sup.3 
Rhog=Density of gas, lbs/in.sup.3 
Rhos=Density of sample, lbs/in.sup.3 
Eo=Dielectric constant of oil (dimensionless) 
Ew=Dielectric constant of water (dimensionless) 
Eg=Dielectric constant of gas (dimensionless) 
Es=Dielectric constant of sample (dimensionless) 
The density of the liquid sample is calculated by measuring the delta 
pressure between the pressures sensed by the vertically spaced devices D 
and D' or the means N. The basic equation for determining the density of 
the samples is: 
EQU Rhos=Rhof-Pd/Hc 
Where: 
Rhos=Density of sample, lbs/in.sup.3 
Rhof=Density of isolation diaphragm fill fluid, lbs/in.sup.3 
Pd=Delta pressure, lbs/in.sup.2 
Hc=Height between isolation diaphragms, inches 
The dielectric constant of the sample is determined by measuring the 
capacitance of the liquid sample in the chamber 21 and using the known 
dimensions of the chamber to calculate the dielectric constant. The basic 
equation is: 
EQU Es=(C * In(B/A) * k)/(2 * Pi * L) 
Where: 
Es=Dielectric constant of sample, dimensionless 
C=Capacitance of sample, pF 
B=Radius of outer cylinder, Ft 
A=Radius of inner cylinder, Ft 
K=Scaling constant 
L=Length of cylinder, Ft 
The values of the dielectric constants and densities of the oil, water and 
gas are calculated from properties equations relating these values to 
temperature pressure. 
It will be apparent that through use of my apparatus and related use of the 
several measurements made thereby in carrying out the above equations, the 
net content of oil, as well as the net content of water and/or gas, in the 
production fluid flowing from an oil well can be rapidly and accurately 
determined without regard to the differential between the densities or 
specific gravities of the oil and the water; without the need to separate 
and extract samples of the oil, gas and/or water; and, without the need to 
perform any special work on the sample of production fluid that is 
temporarily isolated from the main flow of production fluid being tested. 
It will also be apparent that the apparatus that I provide is made of a 
small number of easy and economical to make, assemble and maintain parts 
and is sufficiently rugged and durable to withstand the environments in 
which it is likely to be used, for extended periods, without adverse 
effects. 
Having described my invention, I do not wish to be limited to the specific 
details herein set forth but wish to reserve to myself any modifications 
and/or variations that might appear to those skilled in the art and which 
fall within the scope of the following claims.