US2235064A - Determination of densities of fluids in wells - Google Patents

Description

March 1%, 1941. R. T. CLOUD DETERMINATION OF DEHSITIES OF FLUIDS IN WELLS Filed July 16, 1938 INVENTOR Raymond T Cloud ATTORN EY ill tl utentecl Mar. 18, 1941 cannot ltaymond T. llloudt Tulsa, @tlllldh, assignor to Stanolind illil and Gas llompany, Tulsa ulrlla, a corporation oi Delaware This invention relates to means for the determination of the specific gravities, densities or relative densities oi well fluids and more particularly oi the fluids present in oil wells.

it is an object oi my invention to provide apparatus which will permit the measurement oi the densities of well fluids at varying depths within a well. Another object of my invention is to provide apparatus of this type which can he operated quickly and conveniently and which will give readings at or above the surface oi the ground. A further object is to pr'ovide appara tus io-r logging a well by the determination oi the densities of the fluids within it. it still ther object of my invention is to provide a device for the determination of the point oi gas, oil or water intrusion into a well. Additional objects, advantages and uses oi my invention will become apparent as the description thereoi proceeds.

The device of my invention. includes an cle merit responsive to the density oi the well fluid surrounding it and means tor indicating and/or recording this density. Freierahly this indication or recording is made at the surface oi the well.

fluch a device has many important uses in connection with oil well practice. Thus tor in stance, one method of using such a device is in the logging of here holes. This can he done hy circulating a drilling mud, preferably one having a high specific gravity, within the well and then lowering the head of the liquid in the well, tor instance h-y pumping or hailing out a portion oi the drilling mud. This reduction in hydrostatic head permits the fluids contained in the iorma tions penetrated by the well to enter the here hole. hy the use of my device the speciflc gravity oi the column of liquid can then be measured at various depths or continuously as the device is raised and lowered. Where the measured spe ciflc gravity is that of the circulated mud, it is obvious that no fluid has entered the well hut when the specific gravity is found to have heen lowered it is indicated that fluids from the strata opposite such points have entered. it the opeciiic gravity has been lowered hut does not tall helow unity or below the gravity of oil-held hrines it is apparent that water or brine has entered at this point but where the gravity has fallen to less than unity, it is apparent that oil has entered orin some instances that gas has entered and become emulsified with the drilling mud.

Further, a device of this type is useful in that it permits the rapid and accurate location oi the water-oil interface within an oil well and. this is (UL Eddld) an advantage in bottom. hole sampling work. The device can also be used to determine the densities oi fluids in the bottoms of so called distillate wells and to locate accurately the fluid levels in such wells. It can likewise he used in 4% running tests within a well to determine the elfiect oichanges in pressure, etc. on fluids, particularly fluids oi the distillate type, present within a bore hole.

The invention will now he described in more detail in connection with the accompanying drawing which terms a part oi this specification and is to he read in conjunction therewith. in the drawing: Figure l is a diagrammatic elevation of a por-- tion oi a bore hole and the equipment above it, illustrating in highly simplified form one em hodiment oi my invention;

Figure 2 is a sectional elevation of a preferred embodiment oi that portion or my apparatus which is used within the well;

Figure ii is a sectional elevation taken along the line oi Figure 2;

Figtu'e d is another sectional elevation taken along the line of Figure 2; and

Figure 5 is a highly simplified diagrammatic elevation showing the underground portion oil a modified iorrn of apparatus in accordance with my invention.

Turning to Figure i, it will he seen that a bore hole it penetrates heneath the surface oi the earth ill and that the device is lowered into this here hole to measure the speciflc gravities or densities of the fluids within it, Essentially this device consists ot a weight it acting on a spring l t; The strain occasioned by the weight is, of course, proportional to its effective or apparent weight in the particular fluid in which it is immersed. The result is that varying fluid speciflc gravities vary the point of contact between contactor it and resistance it.

insulated electrical conductors and supporting cables Ill, it and it are raised and lowered together' by means of hoist it. While these are shown as three separate lines they will in practice usually he a single supporting cable containing three insulated conductors.

From hoist it the electrical circuits pass through slip rings (not shown) to conductors it, it and it which are extensions of conductors ll, it and it respectively. A source of voltage 24 is connected across conductors t2 and 23. Conductors it, it and it lead to a resistance ratio type of telemetering device 25.. This device contains two coils 26 and 21 mounted on a common shaft at right angles to each other. These coils are placed in a magnetic field provided by magnet 28.

It will be apparent from the circuits shown that the currents flowing through the two coils will vary in accordance with the position of contactor I 5 on resistance It since the circuit which includes coil 23 contains that portion of resistance I6 which is below contactor I5 while the circuit which includes coil 21 contains that portion of resistance I6 which is above contactor l5. The difference in current flow through these two coils tends to cause them to rotate in the magnetic field provided by magnet 28 and this rotation is opposed by spring 29 which is anchored at post 30. The amount of rotation is a function of the specific gravity of the fluid in which weight I3 is immersed and this degree of rotation is shown on scale 3|. Itwill be apparent that this scale can be calibrated in arbitrary terms, in specific gravity, in pounds per gallon or in any other desired unit.

It will also be apparent that other types of telemetering devices are well known and can be used and that my invention is by no means limited to the use of the resistance ratio type of device.

' As an illustration of the variation in apparent weight to be expected from a device of this type we may consider the case of an aluminum block having a volume of 100 cubic inches lowered into a well which contains mud weighing 11 pounds per gallon. The weight of the block in this instance is 9.7 pounds in air while the apparent weight in the mud, water and oil (specific gravity .65) is as follows:

Apparent weight, pounds Circulating mud 4.94 Water a 6.1 Oil 7.4

The underground portion of one form of my device is shown in Figures 2, 3 and 4. In Figure 2 it will be seen that a case 32 which can suitably be made from some insulating material of the synthetic plastic type is divided into two compartments 33 and 34 by means of partition 35. Means for access to these compartments are, of

course, provided but are not shown inthese views.

Compartment 33 is open to the well fluids through holes 36 and 31 while compartment 34 is filled with a relatively non-compressible insulating liquid such as transformer oil and is kept out of contact with the well fluid by means of gland 38 which will be described in. detail hereinafter. Weight I3 is supported from arm 39 which is rigidly mounted on shaft 40 carried between bearings 4| in such manner as to give a minimum resistance to rotation. This rotation is opposed by coil spring I4 anchored to post 42.

The shaft also carries a contactor arm I5 (best seen in Figure 3) which makes contact with resistance I6. From the two ends of this resistance insulated conductors l8 and I9 lead out of compartment 34 through double headed binding posts 43 and 44 and thence into 3-conductor cable 45 which supports case 32 and its contents through U-bolt 46 and passes at its upper end to hoist 20. Similarly, a third insulated conductor I1 leads from a point in metallic contact with contact arm I5 through double headed binding post 41 to 3-conductor cable 45. It is of course understood that the outside portions of these double headed binding posts must be insulated from contact with well fluids.

Gland 38, to which reference has previously been made, serves the purpose of keeping well fluids out of compartment 34 and at the same time makes it possible to maintain the same pressure in compartment 34 as in compartment 33, thus preventing fracture of the case 32 or partition 35 due to varying well pressures as the device is raised or lowered. Ring 48 is attached to shaft 40 and to it is claimed a flexible oilresistant tube 43. This clamping is done by ring 50 which is equipped with flanges 5! which'are pulled together by means of bolt 52 as can be seen in Figure 4. The other end of this flexible tube is clamped by means of ring 53 to a projection 54 on partition 35. Flexible tube 49 can be made of a synthetic oil-resistant rubber composition such as Duprene or Thiokol. It is of such length and sufiiciently thin as to offer very little resistance to the rotation of shaft lll within the limits required and is also sufliciently flexible to permit equalization of the pressures in compartments 33 and 34.

It will be apparent from this description of one embodiment of my invention that the specific gravity of the fluid within the well at the level of the specific gravity-responsive device will control the force operating on weight I3 and thus give an indication or record of the specific gravity of the well fluid. However, it is not essential to rely on measurements of weight forces in order to determine the specific gravities of liquids encountered in the well since the density of the liquid column is a function of the pressure differentials encountered in traversing this column. Thus 'Q d 2 p Where p=pressure z=depth p: density or the rate of change of pressure with depth is proportional to the density of the liquids at the point where the readings are taken, so that if two pressure devices separated by a small distance are lowered into the well arranged so as to record the differential pressure between the two devices the density or specific gravity of the liquid column included between the two pressure devices, will be proportional to the readings obtained.

A device of this type is shown in Figure 5 which is confined t0 the sub-surface portion of the equipment. A telemetering' device and other above-surface equipment identical with that shown in Figure 1 can be used. The device of Figure 5 includes two compartments 55, each of which has a diaphragm 55. The forces exerted on these diaphragms are, of course, proportional to the pressures of the well fluids on the outside of them. These forces tend to rotate contactor arms 57 and thus vary the positions of these contactors on resistances 58. Conductors I'l, I8 and I9 corresponding exactly to the conductors of the same numerals in Figure 1 lead to the abovesurface equipment and specific gravity can thus be measured by the device of Figure 5 just as in the case of the device of Figure 1.

While I have described my invention in connection with certain preferred embodiments thereof it is to be understood that these are by way of illustration and not by way of limitation and I do not mean to be limited thereby but only to the scope of the appended claims.

In the claims, where density measurement is referred to, I mean to include also the measurement of specific gravity, relative density, etc. and

where I speak of indicating values of this type '1 also mean to include the recording of such values.

I claim: ii i. A device for determining well fluid density which comprises a weight suspended in said well fluid, a spring opposing the force exerted by gravity on said weight, means responsive to the position of said weight under the influence of lo gravity, means for raising and lowering the foregoing elements within a well and means associ- 'ated with said responsive means for forming an indication corresponding to the position of said weight. w 2. A device for determining well fluid density which comprises a weight suspended in said well iluid, a spring opposing the force exerted by gravity on said weight, means responsive to the pbsition of said weight under the influence of 2 gravity, means for raising and lowering the foregoing elements within a Well and telemetering means to produce above the surface of the ground an indication corresponding to the density of the fluid in which said weight is immersed.

3;. A device for determining well fluid density which comprises a weight constructed and arranged to be inserted in a well, means constructed and arranged to be inserted in said well and to suspend said weight in the fluid present in said well, a spring associated with said Weight and said means and constructed and arranged to be inserted in said well for opposing the force exerted by gravity on said weight, a contact arm r-esponsive to the position of said weight, a resistw ance contacted by said contact arm, means for maintaining said resistance and the contact arm in contact therewith out of contact with said well fluid to prevent short circuiting of said resistance, and means associated with said resistance and ill said contact arm for forming an indication corresponding to the position of said weight.

i. A device for determining well fluid density which comprises a weight constructed and arranged to be inserted in a well, means constructed i5 and arranged to be inserted in said well and to suspend said weight in the fluid present in said well, a spring associated with said weight and said means and constructed and arranged to be inserted in said'well for opposing the force exerted til by gravity on said weight, a contact arm constructed and arranged to be inserted in said well responsive to the position of said weight, a resistance constructed and arrangedto be inserted in said well contacted by said contact arm, means 55 for maintaining said resistance and the contact arm in contact therewith out of contact with said well fluid to prevent short circuiting of said re sistance, telemetering means associated with said resistance and said contact arm for forming above the surface of the ground an indication corresponding to the position of said weight and means for-raising and lowering said weight, said contact arm and said resistance in said well.

5. A device for determining the densities of well fluids comprising means responsive to the pressure of well fluids at one level, means responsive to the pressure of well fluids at a second level, means for producing electrical variations in accordance with the differential response of said two responsive means and a telemetering device associated with said last-mentioned means for indicating above the surface of the well the density of the fluid in which said two responsive means are immersed.

6. Apparatus for logging a well comprising density-responsive means adapted to be inserted in a well, means for lowering said density-responsive means into said well, means associated with said density-responsive means and adapted to be inserted in a well for producing electrical variations in accordance with the varying response of said density-responsive means, means for transmitting said electrical variations to the top of said well, and means associated with the last-mentioned means and located above the surface for indicat ing the relative densities at various depths of the fluids in said well in which said density-responsive means is immersed.

7. A device for determining well fluid density which comprises two compartments, one of said compartments being open to the penetration of well fluids and theother being closed to the penetration of well fluids, a substantially fluid tight seal between said two compartments, a densityresponsive member disposed in the first of said compartments, means yieldingly opposing the movement of said density-responsive member, force transmission means associated with said density-responsive member and passing through said seal, a contact arm associated with said force transmission means disposed within the second of said two compartments and responsive to the position of said density-responsive means, a resistance contacted by said contact arm disposed within the second of said two compartments, all of the previously mentioned elements being constructed and arranged to be inserted in a well, means for raising and lowering said elements within said well, and telemetering means associated with said resistance and said contact arm for forming above the surface of the ground an indication corresponding to the position of said density-responsive means.

RAYMOND T. CLOUD.

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