US2322453A - Apparatus for controlling oil wells - Google Patents

Description

June 22, 1943. H. KAVELE 2,322,453

' APPARATUS FOR CONTROLLING OIL WELLS Filed Sept. '23, 1940 2 Sheets-Sheet 1 SEPARATOR GAS SPECIFIC GRAVITY INVENTOR H. H. KAVELER BY M, n

7 ATI'O NEY June 22, 1943. H, H. KAVELER 2,322,453

APPARATUS FOR CONTROLLING OIL WELLS Filed Sept. 25, 1940 2 Sheets-Sheet 2 GAS SPECIFIC GAS SPECIFIC GRAVITY BALANCE INVENTOR H.H. KAVELER RNEY Patented June 22, 1943 2,322,453 APPARATUS Fon. CONTROLLING on. WELLS Herman fle liaveler, Bartlesville, kla., assignor to'lhillips Petroleum Company, a corporation of Delaware npplicatlon'september'zii, 1940;581'13110. 357,998

8 Claims.

This invention relates to apparatus for controlling the withdrawal of fluid through a well bore; and is a continuation in part of my prior filed application, Serial No, 276,108, filed May 2'7, 1939.

The gas production from an oil well is conveniently expressed in relation to the oil production by the so-called gas-oil ratio. The gasoil ratio is generally defined as the ratio of the number of cubic feet of separator gas measured at 60 F. and some reference pressure (usually 14.4 pounds, absolute) to the number of barrels of oil produced, measured at 60 F. and prevailing atmospheric pressure. The ratio therefore expresses the number of cubic feet of gas produced per'barrel of oil during some period of fiow.

Heretofore, the only method for accurately determining gas-oil ratios was to measure separately the oil produced in a stock tank and the gas produced through a separator vent-line having an orifice meter or Pitot tube in place. This method of gauging separately the oil and gas produced shall be referred to as the direct method of determining the ratio. This method requires that a separator and storage tank be provided for each well under test during the test period which usually extends from one to. twenty-four hours.

The gas-oil ratio of an oil well is dependent on a number of factors such as:

1. Inherent reservoir properties as established by reservoir rock, reservoir temperature and pressure and chemical composition of the reservoir contents,

2. The presence in the reservoir of a free gas phase commonly referred to as a gas-cap,

3. The manner in which wells are completed and the method of producing the well (flow rate, choke size, etc.), and

4. The state of depletion of the reservoir.

Gas is the principal source of natural energy available for the production of oil and every eflort is made to conserve reservoir gas by producing oil wells in such a way as to maintain the minimum gas-oil ratio since gas-oil ratios are important in establishing conservative operation of oil reservoirs. Regulatory bodies frequently require extensive periodic gas-oil ratio tests to provide a basis for enforcing the laws established for conservation purposes. I

The determination of gas-oil ratios by the direct method described above is time consuming and often expensive whenever individual separators and stock tanks are required for each well under test. This situation led to a search for som other method of accurately determining gas-oil ratios which would permit a saving of time in observation and which would simplify the mechanical equipment required for individual well tests.

In searching for other means of determining gas-oil ratios, a simple relationship between gasoil ratio and th specific gravity of the gas produced with the oil has been discovered. The employment of this relationship in actual practice provides a means of indirectly determining gasoil ratios to an accuracy of 10 to 15 per cent.

It is an object of the present invention to effectively control the withdrawal of fluid through a well bore.

Another object of the invention resides in the utilization of the specific gravity of produced gas in the regulation of the gas-oil ratio of fluid withdrawn through a well bore that communicates with an oil-bearing formation.

A further object of my invention is the provision of apparatus for regulating the fiow of hydrocarbons through a Well bore to maintain the gas-oil ratio thereof within preselected limits. Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings, forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same, T l

Figure 1 shows a schematic diagram of the surface equipment to be used in determining gas gravities, and

Figure 2 is a graph showing the relation between gas-oil ratio and specific gravity of separator gas.

Figure 3 is a schematic diagram of one appli cation of my invention.

Figure 4 is a schematic diagram of another application of my invention.

Figure 5 illustrates a form of gas specific gravity balance, partly in cross section, that may be advantageously employed in the practice of this invention.

An example of the relationship between gasoil ratio and the specific gravity of gas produced with the oil is given in the following data which were obtained from field observations in which the gas-oil ratio was determined by direct observation.

Example of the relation between gas-oil ratio and the specific gravity of produced gas Separator pressure30 pounds per square inch gauge These data are represented in Figure 2 which we shall call a gravity-ratio" curve. Each and every producing horizon in any field can be represented by a typical "gravity-ratio curve, such as that cited in the example above. Such representative curves must be established by a field test using the direct method of measuring ratio or the curves may be established by computations if the hydrocarbon analyses of the reservoir liquid and gas and proper equilibrium constants are available. The latter involves operations already known and accepted in petroleum technology.

The gas-oil ratio as defined above depends upon separator pressure since the amount of gas dissolved in the separator liquid and the specific gravity of the produced gas may change sensibly with pressure. The gravity-ratio curve must be determined and interpreted always with respect to a chosen, arbitrary separator prwsure. Further, in cases where the separator temperature shows variations in excess of 20 F., a calibration curve to establish the temperature correction would be necessary. In nearly all cases, however, the temperature will not be an important variable. The gravity-ratio curve for a given horizon in a given field will depend upon the pressure in the producing horizon in such a manner that the gravity-ratio curve cited above may have to be redetermined at such intervals as declining reservoir pressures require the adjustment of the curve.

Having the gravity-ratio curve established for a particular field in the manner described above,

, it is only necessary to observe the specific gravity of the produced gas to obtain the gas-oil ratio. This observation can be made on gas produced from the separator or, to make the greatest use of the discoveredrelation, the observation may be made directly in the flow line. All that is required is a means of withdrawing samples of the produced gas into a gas specific gravity meter.

Figure 1 shows a current means of doing this through either nipples 4 and 5, which are approximately 2 by 12 inches, attached to the upper sideof the'flow line 3 through which representative samples of the produced gas could be withdrawn. In' the drawings, I represents a producing well, and 2, a flow control valve mounted on top of the. casing of the well. The fiow line 3 connects into the oil-gas separator 6 and delivers the fluid from the well thereto. Valve I is a fioat valve arrangement which controls valve 8 in flow line 9 to allow for discharge of oil from the .oil-gas separator. Line In running from the top of the oil-gas separator is the vent line conducting the gas from the separator. The nipple I i represents another point at which samples of the gas may be taken to be run through the specific gravity meter. The valve I2 is a pressure regulator which determines the pressure under which the separator 6 operates. Should the pressure in separator 8 and line Ill exceed a predetermined pressure. for example,

. within separator 6 is reduced to below this predetermined pressure, regulator valve l2 automatically operates again to terminate the venting of gas. An additional nipple l3, through which samples of the gas may be withdrawn, is indicated on the down stream side of pressure regulator l2.

As can be seen from the drawings, the position of the sampling nipples can be: (1) In the separator vent line ID as at H and I3 or (2) In the flow line 3 to the separator as at 4 and 5. The nipples 4 and 5 should be located near the separator in order that the pressure at the nipple may be responsive to separator regulation. The location of the sampling nipples 4 and '5 permits observation of gas-oil ratios without the necessity of individual separator and stock tank installations, and furthermore, this is the only method heretofore proposed which permits gasoil ratios to be determined in the flow line before v the gas and oil phases are separated.

' Besides the simplified means of determining gas-oil ratios from observation of the. specific gravity of gas produced in either vent or fiowerator may manually adjust the control valve on the well to such positions as give the maximum gravity of the produced gas (for a chosen separator pressure) and maintain, therefore, the desirable minimum gas-oil ratio. In the other instance when the well is artesian, the specific gravity meter may be installed with auxiliary equipment which will operate the surface control valves automatically. The invention also provides the means for automatically controlling variable subsurface chokes in artesian wells. Furthermore, my instant invention contemplates operating variable speed pumps of all types in such a manner as to provide automatic adjustments to maintain optimum gas-oil ratios.

My invention may be employed to control the operation of a variable speed pump and an embodiment of such an application of the invention is set forth in Figure 3 of the drawings, wherein a conduit l4,'conn'ected to nipple 4, transmits produced gas to a gas specific gravity balance I5, which is provided with-a gasvent I6. It is to be understood that conduit It may be connected to nipples 5, l| or 13, if desired, with equally satisfactory results. The gas gravity meters specific gravity balance is or a conventional type, the particular construction illustrated in Figure including a case I! within which is a fulcrum.

l8 supporting a balance arm l8 having a spherical bulb 28 at one end and an adjustable counterbalance contact member 2! at its opposite end. Above and below contact member 2| is a pair of electrical contacts 22 and 23 which are both connected to a common electric lead 24 while arm I9 is connected to a similar lead 25. The balance may be readily adjusted so that when the specific gravity of the gas passing therethrough is above or below a chosen value of specific gravity, electric contact is made between member 2| and contact 22 or 23 to completean electric circuit, generally indicated by reference numeral 26 (Figure 3). If desired, the balance may be designed to complete the electric circuit only when the gas specific gravity is less than a predetermined minimum. This may be accomplished by merely eliminating contact 22 from the balance. The electric circuit includes a source of electrical energy, such as the plurality of batteries 21 shown in the drawings, a timing device 28 and a power relay 29,

all arranged in series. A pair of electric leads 30 connects the power relay to an electric solenoid having a casing 3|. This solenoid actuates a plunger 32 passing therethrough. A coil spring 33 interposed between plunger 32 and a rigid bail 34 normally maintains the plunger in a retracted position when the solenoid is deenergized. 'Should the specific gravity of the gas passing through balance I5 b above or below the chosen value, electrical contact is made within the balance completing circuit 26, thereby placing power relay 29 into service and energizing solenoid 3|. Plunger 32 is urged downwardly into a valve 35 in gas line 36 to partially or completely cut oil the flow of gas through this line. This regulation of the amount of gas passing through line 36 will in turn determine the speed at which various types of pumps 31, such as gas lift pumps of the type set forth in U. S. Patent 2,142,482, or 2,142,485, will operate. Pump 31 will be completely closed down, or operate at reduced speed as long as solenoid 3| is energized.

The circuit may be interrupted at any desired time by means of timing device 28, which is automatically placed in service when circuit 26 is completed and continues to operate for a predetermined period of time. At the end of such period, timing device 28 is designed to break the electrical circuit, thereby allowing plunger 32 to be retracted by spring 33 and reopen valve 35 to allow unrestricted flow of gas through line 36 and to pump 31.

Figure 4 illustrates a form of my invention which is adaptable to control flowing wells by operating a variable choke that is associated with the well. It will be noted on inspection of the apparatus depicted in Figure 4 that substantially the same equipment is utilized in this embodiment of my invention as that illustrated in Figure 3. In this particular instance, the gas specific gravity balance l5 cooperates with the various items of electrical equipment to control the degree of opening of a variable choke 38.

While I have thus illustrated and described several embodiments covering the application of my invention, it will be obvious that my invention lends itself to a number of other uses taken as the preferred example of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of my invention, or the scope of the subjoined claims.

I claim:

1. Apparatus for controlling the withdrawal of fluid including g s and oil through a well bore comprisingmeans associated with the well and "actuable by variations in the specific gravity of said gas, and means responsive to actuations of said means for controlling the flow oi well fluid whereby the gas-oil ratio of fluid withdrawn from the well is not permitted to exceed a predetermined maximum.

2. Apparatus for controlling the withdrawal of fluid including gas and oil through a well bore comprising a gas specific gravity balance operating between chosen limits or specific gravity of said gas, and means associated with the balance and cooperating therewith for controlling the flow of well fluid at predetermined gravities of the gas whereby the gas-oil ratio of fluid withdrawn from the well is maintained within a chosen range.

3. Apparatus for controlling the withdrawal or fluid including gas and oil through a well bore comprising means associated with the well and actuable by variations in the specific gravity of said gas, and electrical means responsive to actuations of said means for controlling the flow of well fluid whereby the gas-oil ratio of fluid withdrawn from the well is not permitted to exceed a predetermined maximum.

4. Apparatus for controlling the withdrawal of fluid including gas and oil through a well bore comprising a gas specific gravity balance operating between chosen limits of specific gravity of said gas, and electrical means associated with the balance and cooperating therewith for controlling the flow of well fluid at predetermined gravities of the gas whereby the gas-oil ratio of fluidwithdrawn from the well is maintained within a chosen range.

5. In apparatus for controlling the withdrawal of fluid from an oil well, the combination comprising a gas specific gravity balance, means intermediate the well and the balance for transmitting gas from the well to the balance, a variable speed pump in the well, and means cooperating with the balance and the pump to control the speed of the pump to produce the well at predetermined gravities of said gas whereby the gasoil ratio of fluid withdrawn from the Well is not permitted to exceed a predetermined maximum.

6. In apparatus for controlling the withdrawal or fluid from an oil well, the combination comprising a gas specific gravity balance operating between chosen limits of specific gravity of gas admitted thereto, means intermediate the well and the balance for transmitting gas from the well to the balance, a variable speed pump in the well, and means cooperating with the balance and the pump to control the speed of the pump to produce the well at predetermined gravities of said gas whereby the gas-oil ratio of the fluid withdrawn from the well is maintained within achosen range.

'7. In apparatus for controlling the flow of an oil well, the combination comprising a gas specific gravity balance, means intermediate the well and the balance for transmitting gas from the well to the balance, a variable choke associated with the well, and means cooperating with the balance and the choke to actuate the choke to flow the well at predetermined gravities of said gas whereby the gas-oil ratio of fluid withdrawn from the well is not permitted to exceed a predetermined maximum.

8. In apparatus for controlling the flow of an oil well, the combination comprising a gas specific gravity balance operating between chosen limits or specific gravity of gas admitted thereto, means intermediate the well and the balance for transmitting gas from the well to the balance, a variable choke associated with the well, and means cooperating withthe balance and the choke to actuate the choke to flow the well at predetermined gravities of said gas whereby the gas-oil ratio of fluid withdrawn from the well is maintained within a chosen range. a v

HERMAN H; mvmm.

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