Measuring and testing – Borehole or drilling – Downhole test
Patent
1980-11-27
1982-08-03
Myracle, Jerry W.
Measuring and testing
Borehole or drilling
Downhole test
E21B 4900
Patent
active
043422225
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the techniques for the study of drilled wells, and more particularly to methods for the determination of depth of a fluid-saturated stratum and fluid type.
The present invention may be most advantageously used in oil and gas recovery industries in drilling wells.
BACKGROUND OF THE INVENTION
Known in the art are methods for the determination of depth of water-seepage strata, comprising lifting the drill tool and lowering special flow meters (Driller's Handbook by V. I. Mischevich, vol. II, published 1973, "Nedra" Publishers, Moscow, p. 88 (in Russian)).
These methods are dificient in a low sensitivity of flow meters which cannot detect a stratum at low quantities of fluids entering the mud.
Known in the art is a method for the determination of depth of a water-seepage stratum, comprising a short-time suspension of drilling mud supply with subsequent restoration of circulation and detection at the surface of the batch of the drilling mud diluted with fluid from the change in density of the drilling mud compared to the original density, and measuring the time since the beginning of pumping till the appearance at the surface of the batch of drilling mud diluted with fluid (Bull. "Discoveries, Inventions Industrial Designs and Trademarks" USSR Inventor's Certificate No. 484301 Published in No. 34 of 1975, IPC E 21 b, 47 04).
This prior art method is also characterized by low accuracy with small differences in densities of the drilling mud and stratum fluid so that the application of this method is rather limited.
DISCLOSURE OF THE INVENTION
The invention resides in the provision of a method for the determination of depth of a stratum saturated with a fluid, such as water, oil or gas, and the type of fluid saturating the stratum, which enables the detection of location of a fluid-saturated stratum and type of the fluid in a short time and at high accuracy.
The invention materially resides in that in a method for the determination of depth of a fluid-saturated stratum and type of fluid, preferably mineralized water, oil and gas released during drilling, comprising suspending the supply of a drilling mud to a well upon revealing some fluid in the drilling mud leaving the well and restoring the supply of the drilling mud to the well after a certain time lapse, marking the time of restoration of drilling mud supply and the time of appearance at the surface of the batch of the drilling mud diluted with the fluid saturating the stratum to be used for the determination of depth of the stratum, according to the invention, the drilling mud fed to the well is pretreated in such a manner as to maintain the original value of its redox potential at a stable level, the value of redox potential of the drilling mud leaving the well is continuously measured and compared to the original value of redox potential of the drilling mud, and upon a change in the value of redox potential indicating to the presence of a stratum-saturating fluid in the drilling mud the supply of drilling mud to the well is suspended, whereafter the redox potential of a batch of drilling mud saturated with fluid is determined and compared to known normal values of redox potential to determine the type of the fluid.
The stable level of the value of redox potential is preferably maintained within the range from -1.6 to +1.8 V.
The method according to the invention enables the determination of depth of a stratum saturated with some fluid and fluid type: oil, gas or mineralized water with high accuracy. There is no need to use special geophysical instruments lowered into the well which would require considerable time waste.
BRIEF DESCRIPTION OF THE DRAWING
The method according to the invention will low be described in detail with reference to the accompanying drawing, in which:
FIG. 1 shows a principle diagram of an embodiment of a method for the determination of depth of a fluid-saturated stratum and fluid type.
BEST MODE FOR CARRYING OUT THE INVENTION
In drilling a well different rocks are drilled
REFERENCES:
patent: 3722606 (1973-03-01), Fertl et al.
patent: 3802259 (1974-04-01), Eckels
Alekhin Stanislav A.
Bakhir Tatyana M.
Bakhir Vitold M.
Born Raisa I.
Khusandzhanov Aman I.
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