CN102720483A - New method for measuring liquid level of oilwell - Google Patents

Abstract

The invention discloses a method for measuring liquid level of an oilwell through a capacitor. An oil well casing and an oil pipe annulus can be taken as a cylindrical capacitor; groundwater exists underground, so that part of the casing and part of an oil pipe are immersed in liquid; the dielectric constant of underground liquid is different from that of gas, so that when the liquid level of the oilwell changes, the value of capacitance between the oil well casing and the oil pipe changes; and the capacitance between the casing and the oil pipe can be measured by a capacitance measuring device, and then the underground liquid level can be worked out according to a theoretic formula of capacitance and liquid level of the oil well casing and the oil pipe annulus.

Description

A kind of new method of measuring oil well liquid level

Technical field

The present invention relates to a kind of new method of measuring oil well liquid level, use the method that electric capacity comes liquid level under the measuring well.

Background technology

In oil field operation, the bottom pressure and the Relationship with Yield curve made from oil-producing well bottom pressure and static bottom pressure can provide this oil well the highest obtainable oil productivity percentage, thereby can obtain the production efficiency of oil well.Whether the staff can be known can be from this oil well produced more oil.Wherein, oil-well level be oil well must survey one of parameter.

Usually the oil well level instrument has two types of operating principles, and one is based on the ultrasonic wave measuring oil well liquid level depth appearance of ultrasonic echo principle, and another kind is based on the oil well liquid level height and causes bottom pressure to change the electron pressure oil well liquid level measuring instrument of principle.

But because the oil well inner case is complicated, disturbs greatlyyer, ping often is submerged in the noise, and the oil pipe joint hoop number between from ground to the liquid level is difficult for looking into standard, adds ping usually by artificial interpretation, and the operation of ultrasonic wave measuring oil well liquid level depth appearance is very inconvenient.

Electron pressure formula oil well liquid level measuring instrument need be installed the electronic pressure sensor in the oil well bottom, therefore exists the shortcoming that needs a underground work when installing.And along with oil well depth increases, the high temperature high voltage resistant design of bottom pressure sensor is more difficult, and required shaft bottom cable cost is high more, only is applicable to the oil well liquid level measurement that the degree of depth is more shallow.

Because the down-hole pipeline is made up of oil pipe and outer field sleeve pipe; Formed the circular concentric capacitor; At present, capacitance sensor is used widely in displacement, thickness, thing position, temperature, vibration, rotating speed, flow and analysis of components, but in oil well liquid level is measured, does not see use.

Summary of the invention

The present invention has designed a kind of method of utilizing the capacitance measurement oil well liquid level.Whole system is by the SG3524 vibrating circuit, single-chip microcomputer, and digit counter and capacitance measurement line are formed.The capacitance measurement line is connected on the sleeve pipe and oil pipe of oil well, starts measureing equipment, measureing equipment is given main website with the liquid level that measures through data line in real time.

Measured capacitance is converted to the square-wave signal of certain frequency.Adopt the SG3524 chip, connect the resistance R of certain resistance at 6 pin, the capacitance measurement line of device is connected on respectively on the inner and outer wall of well casing, the capacitance of establishing well casing this moment is C, then can obtain the square-wave signal that frequency is f at 3 pin of chip.

Wherein, f=1.18/RC

Square-wave signal is through behind the digit counter, the frequency of measuring-signal, and regularly read the count value in the counter by single-chip microcomputer, obtain capacitance C through computing, and calculate the liquid level degree of depth according to theoretical formula.

Relation between condenser capacitance value and the liquid level.

Concentric circles tubular capacitor (like accompanying drawing 3) ignore edge effect: L＞＞(R-r)

$C=\frac{2\mathrm{\π\ϵL}}{\ln \frac{R}{r}}=\frac{2\mathrm{\π}{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{r}L}{\ln \frac{R}{r}}$

ε: the dielectric constant of plate interstage medium

ε _r: the relative dielectric constant of plate interstage medium

ε ₀: the dielectric constant (8.85 * 10 in the vacuum ^-12C/Nm ²)

R: inner core outer radius

R: urceolus inside radius

L: tube length

If ignore edge effect, the drum type brake liquid level sensor is shown in Figure 4, and it is parallelly connected that the electric capacity that immerses the liquid part and the part that does not immerse are equivalent to two electric capacity, then the capacitance of sensor and be by the relation of liquid level:

$C=\frac{2\mathrm{\π}{\mathrm{\ϵ}}_{0}h}{\ln (r_2/r_1)}+\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)h_x}{\ln (r_2/r_1)}=A+K{h}_x$

Wherein, $A=\frac{2\mathrm{\π}{\mathrm{\ϵ}}_{0}h}{\mathrm{Ln}(r_2/r_1)};$ $K=\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)}{\mathrm{Ln}(r_2/r_1)}$

Thus it is clear that, sensor capacitance C and tested liquid level h _xLinear.

Description of drawings

Fig. 1 is overall structure figure of the present invention;

Fig. 2 is a liquid level detection device structure chart of the present invention;

Fig. 3 is a circular concentric capacitor sketch map of the present invention;

Fig. 4 is circular concentric condenser capacitance value of the present invention and liquid level depth relationship sketch map.

The specific embodiment

The oil well liquid level checkout gear is installed in the oil well hydraulic fluid port; Receive oil pipe and sleeve pipe through lead the external capacitor end of liquid level detection device; Obtain the square-wave signal of a certain frequency relevant this moment with capacitance; There is digit counter to obtain frequency, regularly reads the value in the counter by single-chip microcomputer, and with counter O reset.Obtain capacitance by frequency computation part, further calculate the oil well liquid level height again.And the liquid level degree of depth is sent to main website in real time through data transmission device, be used for real-time monitoring to oil well liquid level.

Claims (6)

1. use the capacitance measurement oil-well level.

2. mainly be to utilize oil well casing and the interior liquid level variation of oil pipe annular space to cause sleeve pipe and oil pipe changes in capacitance, sleeve pipe and oil pipe capacitance according to measuring according to theoretical relationship, obtain the oil well liquid level height.

3. to be the oscillator that utilizes the SG3524 chip convert capacitance the square-wave signal of certain frequency to the measuring method of oil well casing and oil pipe electric capacity, through the frequency of counter measures signal.

4. Implemented by Using Single-chip Processor reads the frequency values of counter, and with counter O reset, counts again, and single-chip microcomputer calculates capacitance with the numerical value process that reads, and further obtains the height of liquid level in oil well casing and the oil pipe annular space.

5. whole oil well liquid level measuring system is by oscillating circuit, single-chip microcomputer, and digit counter, capacitance measurement line are formed.

6. the capacitance measurement line is connected on oil well casing and the oil pipe, starts measureing equipment, measureing equipment will record the oil well liquid level height.

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