Wells – Processes – Vibrating the earth or material in or being placed in the...
Reexamination Certificate
1998-06-28
2001-06-26
Bagnell, David (Department: 3672)
Wells
Processes
Vibrating the earth or material in or being placed in the...
C166S177200, C166S177600, C166S177700
Reexamination Certificate
active
06250386
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for the stimulation of oil wells by using sound waves which are emitted from the oil well by means of a hydraulically operated sound source or hammer.
BACKGROUND
To date, it has only been possible to recover parts of the oil found in subterranean oil reservoirs because of the special adherences which retain the oil in the formation. These are a combination of capillary forces, adhesive forces, cohesive forces and hydraulic forces.
Most part of the oil will remain in the reservoir until new technology makes it possible to enhance recovery efficiency by affecting the adherences which lock the oil to the formation. Since the reserves in an oil reservoir represent vast economic resources, it is of the greatest interest to develop methods and equipment in order to be able to enhance oil recovery efficiency.
Intensive research is being carried out worldwide in the field of so-called secondary oil recovery to find methods which increase the oil yield. These include methods ranging from injection of chemicals, electrical stimulation, electromagnetic stimulation and also various methods of acoustic stimulation. Interest has been directed in particular towards the conditions surrounding the surface tension between oil and water, where attempts have been made to solve the problems involved here by injecting tensides and surfactants
In U.S. Pat. No. 5,282,508 there are described a number of different embodiments of vibrators for stimulating an oil reservoir in conjunction with electrical stimulation. These vibrators are powered by electricity, but the operation of vibrators using electric power in an oil well environment has been found to pose major practical problems with regard to insulation since the voltages used are about 1500 volts. There has thus been a need to develop a vibrator which could be operated by means of an energy source other than electricity. The most natural was to think of the use of hydraulics or gas, but the problem which arises when using a conventional vibrator as used, for example, in piling or in hydraulic hammers on excavators is that two oil supply lines must be used. In the case of short distances it is possible to use two lines, but when an oil well of several thousand meters is involved, this is impossible because of the pressure loss in the line.
SUMMARY OF THE INVENTION
It is an object of the present invention to show a tool which will enhance recovery efficiency and permit the start of oil production from oil wells where production has already come to a halt or is falling off rapidly. This is achieved with the aid of sound waves, where it has been found that the best effect is obtained when the sound waves are generated and transmitted to the formation from the oil-producing well.
An object of the present invention is to show an embodiment where it is only necessary to use one feed line for the oil and where the return oil is brought up in the actual production tubing in the oil well. To accomplish this, the following conditions must be fulfilled. There must be a power unit at the surface which continuously feeds pressure oil to the vibrator. Since this cannot be controlled with a valve from the surface because of the distance to the vibrator, there must be an accumulator therein which accumulates oil under pressure, but where the pressure also actuates the vibrator. This is achieved by means of a special valve which opens when the pressure in the accumulator reaches a determined level. The valve is so constructed that it alternates at the end of the stroke, i.e., when the plunger strikes against an expansion pipe, owing to a pressure top formed in the hydraulic system because of the sudden stop of the plunger. The fixed aperture of the valve determines the speed of the plunger, whilst the feed quantity of pressure oil determines the repetition frequency.
According to the invention, a process for the sound stimulation of oil wells is proposed, characterized in that there is placed in the well a vertically oscillating vibrator (hammer), which is operated by the produced oil from the oil well, in that a part of the oil is pumped to the vibrator from a hydraulic power unit at the surface, and where the exhaust oil from the vibrator is passed into the oil well and transported back with the produced oil from the oil formation. The vibrator generates elastic sound waves in that a plunger therein strikes against an expansion piece, and sends the sound waves into the reservoir as elastic sound waves having a repetition frequency of from a few hundred to several hundred per minute and where the frequency in the train of waves is composed of the resonance characteristic of the impact from the plunger, which has been found to be in the range of 100 Hz to just a few Hz.
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Bagnell David
Dougherty Jennifer R
Eureka Oil ASA
Merchant & Gould P.C.
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