US 3309308 A
Description (OCR text may contain errors)
arch M W57 c. A. Scl-IAD METHOD OF CONTROLLING THE LEVEL OF CONTAMINATION IN CRUDE PETROLEUM Filed June 17. 1965 United States Patent O 3,309,308 METHGD F CONTROLLING THE LEVEL CQNTAMTNATION IN CRUDE PETROLEUM Charles A. Schad, 6547 E. 27th St., Tulsa, Okla. 74129 Filed .lune 17, 1963, Ser. No. 238,139 3 Claims. (Cl. 208-178) This invention relates to a method of controlling the level of contamination in crude petroleum. More particularly, the invention relates to a method of controlling the level of contamination in petroleum in an automatic custody transfer system. Still more particularly, the invention relates to a method of controlling the level of contamination in petroleum in an automatic custody transfer system in a manner to anticipate an approaching unacceptable level of contamination and providing means in the method of corrective measures to reduce the level of contamination so as at all times to keep the level of contamination below the acceptable level and thereby maintain the automatic custody transfer unit in condition for substantially continuous delivery of produced petroleum to custody of the purchaser.
In recent years a trend has developed in the petroleum industry toward the automatic transfer of crude petroleum from the custody of the producer to the custody of the purchaser or pipe line company. Such systems are usually referred to as lease automatic custody transfer units or more briefly LACT units. Typically, such installations include the provision of flow control means wherein crude petroleum produced in one or more leases is channeled through a probe device which measures the level of contamination of the produced petroleum and from thence through a metering system wherein the quantity of produced oil being transferred or sold to the purchaser or pipe line company is measured and recorded. By agreement between the producer and the purchaser, a maximum acceptable level of contamination of the produced crude petroleum is acceptable. When the contamination level rises above such predetermined acceptable level the transfer of petroleum is terminated by automatic control means in the LACT unit. After delivery is terminated measures are undertaken to treat the unacceptable petroleum to reduce or knock-out the contaminants to reestablish an acceptable level.
The type of contamination most generally encountered in petroleum is termed basic or -bottom sediments and water or more -brieily BS and W. The device utilized to detect contamination is usually termed a probe and. is connected electrically .with a BS and W monitor which functions to interpret the results electrically detected by the probe to provide an electrical signal proportional to the level of contamination. ln a typical LACT unit an automatic valving system is responsive to the monitor signal so that when contamination or BS and W in the petroleum being transferred reaches the agreed predetermined maximum acceptable limit, the unit, by the automatic valving system, terminates the fiow of petroleum through the metering system and thereby terminate delivery of custody of the petroleum. The automatic valving system typically channels the flow of petroleum through a treating system. There are two basic means of treatment of petroleum to reduce the contaminant level. One system is to circulate the contaminated petroleum through a heater-treater system wherein, by exposing the petroleum to heat and a separating system, water and bottom sediments are caused to be settled from the produced petroleum. The second common means is to inject chemicals into the petroleum which, in effect, breaks down created emulsions so that water and bottom sediments are settled out. In most fice modern type of LACT units provision is made so that when the `contaminated oil has been circulated sufficiently to -bring it below the acceptable contamination level recirculation is terminated and the valving system automatically again channels the produced petroleum through the metering system and thereby reestablished continuation of transfer of custody.
Thus, with existing LACT systems, when an unacceptable level of contamination is encountered the transfer of custody of petroleum automatically ceases and a treatment or recirculation process begins and continues until the level of contamination is brought back to an acceptable level. This means that production time is lost while an unacceptable level of contamination is being corrected. It is an important object of this invention to provide a method of controlling the level of contamination in produced petroleum in a manner such that an unacceptable level of contamination is anticipated in advance and corrective measures taken to reduce the level of contamination before an unacceptable level is reached.
Another object of this invention is the provision of a method of continuously monitoring the level of contamination of petroleum, automatically determining the level of contamination versus the total volume of the petroleum tested and automatically instigating corrective measures in proportion to the level of contamination of petroleum being tested to reduce and thereby maintain the contamination to an acceptable level.
These and other objects and a better understanding of the invention may be had by referring to the following description and claims taken in conjunction with the attached drawings which:
The gure is a diagrammatic view of a lease automatic custody transfer unit including the provision of a system utilizing the method of this invention for controlling the level of contaminates in produced petroleum.
Briefly this invention may be described as a method of controlling the level of contaminates in petroleum. More particularly, but not by way of limitation, the invention may be described as a method of controlling the contamination level in petroleum comprising the steps of passing the petroleum through a contaminate detector to obtain and analog electrical measurements proportional to the level of contaminate contained therein, converting the analog signal thus obtained to a contaminate digital signal, measuring the quantity of petroleum passing through the said contaminate detector and generating a digital signal in proportion to the volume thereof, inte-v grating the contaminate digital signal with the volume digital signal to obtain a contaminate per volume digital signal, and treating said petroleum before said petroleum passes through said contaminate detector for reduction of contamination in proportion to the said obtained contaminate per volume digital signal.
Referring now to the figure a system utilizing the method of this invention is diagrammatically disclosed. The invention will be described, for purposes of illustration, as it is particularly applied to a lease automatic custody transfer unit wherein the custody of petroleum is being transferred from the producer to a purchaser. Petroleum ows to the system from a petroleum inlet 10, such as from a lease consisting of a number of wells. It is understood however that in some units the petroleum inlet pipe 10 may carry petroleum from a multiplicity of leases having intermediate storage facilities and such a system may consist of an elaborate system for systematically transferring petroleum from a multiplicity of leases to provide the petroleum in the pipe 10. For simplicity, in this description, it will be assumed that petroleum produced from a single lease is collected and ows to the system for custody transferred through pipe 10. A check valve 12 is typically provided to permit petroleum to flow only in a direction from the lease to the system. The produced petroleum flows through a heater-treater 14 where it is subjected to increased temperature for separation of entrained solid particles, usually referred to as bottom sediments, and water.
Through pipe 16 the produced petroleum flows out of the heater-treater 14 and into a storage tank 18 which functions more or less as a reservoir for produced petroleum ready to be transferred to the custody of the purchaser, such as -a pipe line company. Pipe 20 leading from the transfer tank to a transfer pump 22 conducts the petroleum through a probe 24 where the level of contamination is detected. Typically, the probe 24 is a capacitance measuring and comparing device. The amount of contamination entrained in petroleum is reected as a change in the dielectric constant of the petroleum which in turn is detected by the capacitance effect of probe 24. In electrical communication with probe 24 is a measuring system known as a BS Iand W monitor 26. Probe 24 and the BS and W monitor 26 are well known items of equipment in the petroleum industry. Briefly, the BS and W monitor 26 is basically a bridge circuit device which compares the capacitance detected by probe 24 against a standard to obtain an electrical analog signal indicative of the BS and W or contaminate level of the petroleum passing through probe 24.
Pipe 28 conducts the petroleum out of probe 24 and into a two-Way valve 30. When the system is functioning to transfer petroleum to the seller the valve is in the position shown, that is, petroleum ilowing through pipe 28 Hows through the valve 30 and by way of pipe 32 to `a positive displacement meter 34 where the quantity of petroleum being transferred is measured and recorded. When the petroleum passes through meter 34 into the outlet pipe 38 custody has been transferred to the purchaser.
This is a basic custody transfer system although it is understood that many embellishments may be added. A typical supplemental device not shown is a sampler which periodically draws samples to provide means for determining the average level of quality of product being -transferred.
As it has been previously indicated, only petroleum having a contaminate level below pre-agreed maximum acceptable level can be transferred to the purchaser. The BS and W monitor 26, by electrical communication with valve 30, functions to automatically activate valve 30 to shunt the how of petroleum away from meter 34 when a given level of contamination is detected. When this occurs, the typical arrangement is to direct the flow of petroleum away from meter 34 and back through a pipe 40 for recirculation and treatment to bring the contamination level of the unacceptable petroleum back to an acceptable level. Typically, the rejected petroleum flowing through pipe 40 past a check valve 42, and back into heater-treater 14 where it is again subjected to the heat of the heater-treater for the additional removal of water and bottom sediments. In the typical LACT unit, valve 30 will remain in the reject or recycle position until the contamination level detected by probe 24 and BS and W monitor 26 falls below the acceptable level at which time valve 30 will be actuated to reestablish delivery of petroleum to the purchaser. In the meantime, after storage tank 18 is filled, no additional petroleum can be received through inlet pipe 1t) and, by Iautomatic valve means not shown, production of petroleum ceases until the contamination level of the petroleum in the system is reduced to an acceptable level and delivery to the purchaser is resumed. This of course means that production time is lost and the eiciency of the system to transfer custody of the produced petroleum is reduced. This invention provides means to anticipate increases in the contamination level and to take corrective measures to prevent the contamination level rising to or above the unacceptable maximum limits. This invention provides means of instituting corrective measures to begin reduction of the contamina1 tion level in advance of the rise to an unacceptable level so that productivity of the lease or leases from which the petroleum is produced will not be stopped and more effective utilization can be had of the delivery facilities.
The first step in this invention to control the level of contamination in petroleum consists of the addition of an analog-to-digital converter or ADC circuit 42 in electrical communication with the BS and W monitor 26.
As previously described the BS and W monitor delivers, by means of a bridge circuit, an analog signal indicative of the level of contamination detected by probe 24. The ADC circuit, a circuit well known to electrical engineers, converts this analog signal into a digital signal indicative of the contamination of petroleum passing through probe 24.
Aiiixed to the meter 34 is a digital generating device 44 which generates a digital electrical signal in proportion to the quantity of uid owing through the meter. Such a digital generating device is well known in the petroleum industry and consists usually of a switch mechanism or other pulse generating device actuated by counter wheels connected to the meter 34. Typically, the digital generating device 44 may be arranged to create 100 pulses for each barrel of petroleum passing through the meter 34.
The output of the ADC circuit 42, which provides a' digital signal proportional to the contamination level detected by probe 24, and the output of the volume digital generating device 44, which provides a digital signal in proportion to the quantity of fluid passing through probe 24, is fed to an integrating circuit 46 where the two digital signals are integrated to obtain a total volume contami-| nate digital output signal. This output signal, taken on conductor 48, is indicative of the contamination measured by the probe 24 as compared to the volume of fluid flowff ing through probe 24 to indicate the actual elfective con'J taminate level of the fluid passing through the probe 24.
As the contamination level increases such is indicated by the electrical signal at the output 4S of integrator 46. This electrical signal may be used in a variety of Ways. As an example, by conductor 48 and through a switch 59 the signal may be fed to a treater temperature con trol device 52. The treater temperature controldevice 52 is typically a thermostat type of device regulating the temperature to which the petroleum is subjected in the heater-treater 14. When an increasing level of contamination is detected by the probe 24 proportional to the quantity of iluid flowing therethrough, the output of integrator 46 on conductor 43 will function to raise the heater-treater temperature to separate out more of the BS and W contained in the petroleum as it flows through the heater-treater. This in effect, counteracts the increase in contaminate level to begin more intensive treating of incoming petroleum to reduce the level of contamination.
As a decreasing level of contamination is reiiected in probe 24 the output signal on conductor 48 from integra-I tor 46 will function by means of the treater temperature control device 52 to reduce the temperature applied to the petroleum in lthe heater-treater 14. In this manner, steps are taken to apply sufficient treatment within the heater-treater 14 to reduce the BS and W level below the agreed acceptable maximum but without exposing the petroleum passing through the heater-treater 14 to an I unnecessarily high temperature.
Another common means of treating petroleum to reduce the BS and W level is by injecting chemicals into the petroleum to cause the BS and W to more easily and effectively be removed therefrom in subsequent separation processes. The output of integrator 46 by means of conductor 48 and a switch 54, may be applied to a chemical injector 56 to vary the amount of chemical injected into the incoming petroleum. Chemical typically is injected through a pipe 58 having a check valve 66. The chemical injector system 55 can be said to include noti only the chemical injector 56 but also includes pipe 58, check valve 6i) and the balance of the portion of the fluid conducting system for removal of the BS and W by the effect of chemical action.
The provision of switches 50 and 54 provide a means Where temperature regulation and/or lchemical injection corrective measures may be taken to control the level of contamination in the produced crude petroleum.
Integrator 46 may be constructed in a variety of ways all within the knowledge of any electrical engineer familiar with integrating circuits and may include various c-alibrating and control mechanisms.
This invention provides a method of controlling the level of contamination in petroleum in such a Way as to more effectively `utilize lease automatic custody control equipment so that contamination will not periodically shut the device down and forestall t-ransfer of custody of petroleum while treatment is being undertaken. The method of this invention provides a means of m-ore efficiently utilizing lease automatic custody transfer systems.
Although the invention has .been described with a certain degree of partcula-rity it is manifest that many changes may be made in the details of co-nstruction and the arrangement of components without departing from the spirit and scope of this disclosure.
What is claimed: 1. A method of controlling the level of BS and W in petroleum comprising:
passing the petroleum through a temperature controllable heater-treater and from thence through a BS and W level detector;
generating a contaminate electrical analog signal in proportion to the level of BS and W;
converting the contaminate analog signal thus generated to a contaminate digital signal; measuring the quantity of flow of petroleum passing through said BS and W level detector and generating a volume digital signal in proportion thereto;
integrating the contaminate digital signal With the volume digital signal to obtain a total volume contaminate digital signal;
and cont-rolling the temperature of said heater-treater in response to said total volume contaminate signal to increase the temperature of said heater-treater as the level of total volume contamination increases.
6 2. A method of controlling the level of BS and W in petroleum comprising:
passing the petroleum through a chemical injector and from thence through a BS and W level detector;
generating a BS and W electrical analog signal in proportion to the level of BS and W;
converting the contamination analog signal thus generated to a contaminate digital signal;
measuring the quantity of flow of petroleum through said BS and W level detector and :generating a volume digital signal in proportion thereto;
integrating the contaminate digital signal with the volume digital signal to obtain a total volume contaminate signal;
and controlling the quantity of BS `and W reducing chemical injected into said petroleum passing through said chemical injector with said total volume contaminate signal.
3. A -method of controlling the BS and W level in petroleum comprising:
passing the petroleum through a BS and W detector to obtain an analog electrical measurement proportional to the level of BS and W thereof;
converting the analog signal thus obtained to a contaminate digital signal;
measuring the petroleum passing through the said BS and W detector and generating ya volume digital signal proportional to the volume thereof;
integrating the contaminate digital signal with the volume digital signal to obtain a total volume contaminate digital signal;
and treating said petroleum before said petroleum passes through said BS and W detector for lreduction of BS `and W in proportion to the said obtained total volume contaminate digital signal.
References Cited by the Examiner UNITED STATES PATENTS 3,107,526 10/1963 Kuntz 73-195 3,163,173 12/1964 Kuntz 137-93 DELBERT E. GANTZ, Primary Examiner.
HERBERT LEVINE, Examiner.