US2070836A - Method for obtaining fluid samples from drilled wells - Google Patents

Description

Feb. 16, 1937. G A, A READY 2,070,836

METHOD FOR OBTAINING FLUID SAMPLES FROM DRILLED WELLS Filed Oct. 1, 1935 la "zil m a Fig. 1.

Patented Feb. 16, 1937 UNITED STATES METHOD FOR OBTAINING FLUID SAMPLES FROM DRILLED WELLS George A. Macready, Los Angeles, Calif.

Application October 1, 1935, Serial N0. 43,074

2 Claims.

My invention relates to bore holes or drilled wells in which it is desired to test formations penetrated by the drill to determine the character of fluid the formation may yield.

In the art of drilling wells for petroleum or other fluid products it is essential that undesirable fluid such as water be excluded from the productive formations. The usual practice is to seal a string of steel casing to the wall of the well by cement so that all fluid originating from formations above the seal is excluded from the interior of the casing and the desired fluid from formations below the seal can then be drawn to the surface through the casing.

Wells drilled by hydraulic methods are kept full of mud laden drilling fluid so that it is difficult to identify the character of fluid a formation penetrated may yield. Casing is expensive so that it is desirable to make a preliminary test of the formation before permanently cementing casing. The test can be made by taking a sample of fluid by my method.

In 1922 I invented a method and apparatus by which a sample of fluid could be caused to enter and become entrapped in drill pipe and brought to the surface in the pipe for inspection, and was granted Patents 1,896,492 and 1,896,522 therefor. Other inventors have followed with improvements thereon.

It requires sometimes several hours to bring the sample to the surface by pulling it out in the drill pipe. My present invention provides for boosting the sample up through the drill pipe to the surface for inspection before pulling the drill pipe. Considerable time is saved thereby so that the well operator can decide on the next procedure for his well while the drill pipe is being pulled from the well.

An object of my invention is to provide a method for obtaining fluid samples from drilled wells by inserting a tube into a well, temporarily sealing the tube against the wall of the well to exclude fluid in the well above the seal from entering the interior of the tube, causing a sample of fluid from below the seal to enter the tube, breaking the seal, and pumping a measured quantity of liquid into the well outside the tube sufflcient to displace the sample upwardly through the tube to discharge from the top of the well for inspection.

With the foregoing and other objects in view which will be made manifest in the following detailed description and especially pointed out in the appended claims, reference is had to the accompanying drawing for illustrative embodiment of my invention, wherein:

Figure 1 is a longitudinal section of a well showing a sample tube therein with a sample of formation fluid drawn into the tube and a pump with fluid measuring apparatus shown in elevation at the ground surface, and

Figure 2. is a longitudinal section of a well showing the sample tube raised to break its seal and the sample of formation fluid displaced to the ground surface for inspection.

Similar numerals refer to similar parts throughout the several-views.

My method is for determining the character of formation fluid F that will be yielded by a formation T encountered in a well as illustrated on Figures 1 and 2. A tube I is inserted into the well and sealed against the wall of the well as at S by means of a packer P.

The tube I may be the conventional casing, tubing or drill rod used in well practice such as the drill pipe used in drilling the well. The packer illustrated at P is of the rat hole type which makes a seal by being pressed by weight of the drill pipe imposed upon it against a previously formed shoulder on the well wall. The seal forms an annular barrier around tube I so that fluid cannot flow up or down outside the tube past the barrier. This application for Letters Patent is not directed to the specific form of seal and any other conventional type of packer can be selected to be most eificient for the individual well, such.- as a flush wall formation packer, or a hook wall casing packer if the seal is made against casing.

After the seal S has been made to exclude overlying fluid a sample of formation fluid F from formation T is next caused to enter tube I.

The sample F may be caused to enter tube l by any of several procedures among them being the following: I

(a) Drilling fluid in tube I may be removed therefrom by pumping, swabbing or bailing, cap

I6 being removed, until the hydrostatic pressure within tube I is less than the pressure in forma tion T which causes the sample of fluid F to flow through inlet 2 into tube I.

(b) Using the apparatus illustrated in applicants Patent Number 1,896,522 the drilling fluid in tube I can be expelled by admitting compressed gas through valve 3 to express the drilling fluid M through a side check valve illustrated at 4 or through the inlet 2 if the -air pressure has been applied during lowering of tube I before making seal S. After the seal S has been made the compressed gas is released, as through valve 5 reducing the hydrostatic pressure in tube I so that a sample of formation fluid F is caused to enter tube I through inlet 2.

(c) The valved packer apparatus illustrated in Patent Number 1,683,031 granted to W. 0. Harris can be used and the tube I lowered into the well Iibf Harris the valve I8 of Harris is opened by matured into Patent Number 2,040,619, granted May 12, 1936, can also be used to perform the method described and claimed herein but not described in said application.

After it is believed sufiicient sample of formation fluid F hastentered tube I (illustrated on Figure 1), the seal S is broken by raising tube I to lift packer P oifits seat.

Drilling mud M from .outside the tube rushes into tube I through inlet 2 displacing sample F bodily upward in the tube I. Additional mud fluid M' is flowed or pumped into the top of the well as at 6. Thesample F usually consists of water, oil or gas of lighter specific gravity than the mud drilling fluid M .or M so that when hydrostatic equilibrium is established the fluid level stands higher inside tube I than outside tube I. It is common practice in oil well drilling to use drilling muds of different specific gravities.

- By filling the well hole outside tube I to the surface with drilling fluid M of heavy specific gravity all-of the fluid originally in tube I including sample F is displaced upwardly to discharge from the top of the well, as into vat I. v (Illustrated on Figure 2.)

For most efflcient use of my method the quantity of additional mud fluid M' supplied into the top of the well may be the same as the volume of fluid that can be contained in tube I, which is readily computed from the known dimensions of tube I. When this known quantity of mud fluid M has been supplied into the well then it is known that the sample of formation fluid F has been completely displaced from tube I to discharge at the top of the well.

The quantity of mud fluid M may be measured by any of numerous standard methods, four of which are illustrated on Figure 1 as follows, although only one measuring method is sumcient:

(a) The quantity of fluid M supplied into the top of the well can be measured by pumping with.

pump II through suction I4 from vats 8, 9 of known calibration.

(b) The quantity of fluid M' can be measured by a liquid meter III in the supply line registering on scale I64.

(c) The qauntity of fluid M can be measured by counting the strokes of pump II either mentally or by a mechanical counter I2 registering on scale I63, the delivery capacity of each stroke having been previously calibrated.

(d) The quantity of fluid M' can be estimated mentally by an expert operator.

The following auxiliary conditions and precautions improve efliciency.

The inlet 2 should be selected of such small diameter that the maximum rate of flow through it with its greatest pressure differential should not be greater than the flow of liquid that pump I I is capable of supplying so that there may be no danger of the fluid level in the well falling to the danger point to cause a blow out.

To protect inlet 2 from clogging with dbris a perforated tube I3 may be used.

During the period that mud fluid M' is being supplied to the well the .tube I may be moved vertically or rotated to prevent its sticking in the well.

In the event that it is impractical or inconvenlent to use mud of different specific gravities a aoraesc packing gland of any conventional type can be inserted between tube I and the wall of the well near its top so as to prevent leakage, and the mud fluid M forced into the top of the well under pressure.

It is advisable to select the level for seal S at a depth where the formation or wall of the well is impervious and has suflicient strength to support the hydrostatic load on the seal.

The vertical distance of outlet I5 above the top of the well should be at a minimum to facilitate complete discharge of'sample F.

In deep wells a pressure relief valve may be used on the packer to lessen the strain of lifting the packer off its seat.

After the sample F has been displaced to the surface for inspection the direction of flow of mud fluid in tube I may be reversed if desirable and the tube I removed from the well.

displaced to the surface, can be inspected to determine its character and value and the probable yield to be expected from formation T.

The operator of the well then has suflicient time to decide on the next procedure for his well while the tube I is being withdrawn from the well.

Where secrecy is desired against prying speculators the sample F may be discharged into a closed tank to be inspected only by the operator or his agents and friends.

I claim as my invention:

1. A method of obtaining fluid samples from wells which consists of inserting a tube into a well, temporarily sealing the tube against the wall of the well to exclude fluid in the well above the seal from entering the interior of the tube,

causing a sample of fluid from below the seal to enter the tube, breaking the temporary seal, supplying a measured quantity of liquid into the well outside the tube sufiicient to displace said sample upwardly through the .tube to discharge from the top of the tube for inspection and identifying .as the sample that fluid which has discharged from the top of the well when the quantity of liquid supplied outside the tube is substantially equal to the interior cubic volume of said tube.

2. A method of obtaining fluid samples from wells which consists of inserting 'a tube-into a well, temporarily sealing the tube against the wall of the well to exclude fluid in the well above the seal from entering the interior of the tube, causing a sample of fluid from below the seal to enter the tube, breaking the temporary seal, supplying a quantity of liquid into the well outside the tube substantially equal to the interior cubic volume of said tube so as to displace said sample upwardly through said tube to discharge from the top of said tube for inspection and identifying as the sample that fluid which has discharged when said quantity has filled the well outside aid tube.

GEORGE A. MACREADY.

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