CN104316449A - Experimental method and experimental device for determinating volcanic gas-water relative permeability - Google Patents

Abstract

The invention relates to an experimental method and an experimental device for determinating volcanic gas-water relative permeability. Through experimental steps of preparing a volcanic core, measuring permeability and porosity of a rock sample gas, exerting a confining pressure and performing rock sample gas water displacement, a relative permeability curve when gas saturation increases and water saturation decreases in the volcanic core is determinated by a non-steady-state method.

Description

A kind of for measuring volcanics gas, the experimental technique of water relative permeability and experimental provision

Technical field

The present invention relates to a kind of experimental technique measuring permeability, particularly relating to a kind of for measuring volcanics gas, the experimental technique of water relative permeability and experimental provision.

Background technology

Volcanic rock reservoir belongs to ultralow permeability gas reservoir, and its reservoir space is based on hole, but compared with conventional ultra-low permeability reservoir, volcanics has more pore, fracture development usually, and therefore its volcanic gas reservoir has higher business extraction value.In recent years, China develops many places volcanic gas reservoir in succession, and obtains certain economic benefit.

Gas, liquid is the important references data in gas reservoir development performance analysis and numerical simulation to permeability curve, this curve obtains with stabilization method test in the lab with the true core of gas reservoir usually, and for volcanic rock reservoir, due to the cavern porosity structure of its inside, two-phase fluid mixed phase easily produces phenomenon of advancing by leaps and bounds when injecting, cause mixed phase, cause measurement result and physical presence relatively large deviation.Due to the Extra-low permeability of volcanics sample, the pressure reduction of displacement simultaneously must be less than confined pressure, and therefore confined pressure size is wanted suitably: if confined pressure is too small, and displacement pressure reduction is also by too small, then displacing velocity is extremely slow, and easily produces water lock phenomenon, and will affect output fluid flow; If displacement pressure reduction is excessive, then will makes microfracture blocking in rock sample, and even cause rock sample to rupture.Therefore in OK range, confined pressure should be increased as far as possible to ensure enough Space adjustment displacement pressure reduction.

Summary of the invention

For the problems referred to above, the present invention proposes a kind of experimental technique for measuring volcanics gas, water relative permeability, to solve in prior art volcanics gas, aqueous phase the accurate not problem of permeability survey.

Another object of the present invention is to provide a kind of experimental provision for measuring volcanics gas, water relative permeability.

Experimental technique of the present invention comprises the steps:

Step 1, prepared by rock core: get volcanics rock core, rock core drills through rear polyethylene film and wraps sealing;

Step 2, rock sample perm-plug method and factor of porosity: rock sample is per weighed once after drying 4 hours at 90 DEG C half an hour, until when the relative error of double mass change is less than 5%, records now rock sample quality; Rock sample is put into clamper, uses nitrogen to inject, record displacement pressure reduction, air output, calculate rock sample perm-plug method; Rock core is put into and vacuumizes saturation device, by saturated for the rock core local water vacuumized, and weighing measurement, thus calculate volume of voids and the net porosity of rock sample;

Step 3, applies confined pressure: the rock sample after saturation simulation bottom water is loaded core holding unit, and utilize confined pressure pump to add confined pressure to core holding unit, the value of confined pressure should between formation damage pressure and starting pressure;

Step 4, rock sample gas drive water is tested: the pressure regulator valve opening gas injection apparatus, carries upstream pressure, and carry out gas drive water to core holding unit under given upstream pressure; Initial differential pressure must ensure that can overcome end effect does not produce turbulent flow again; Record the displacement time in each moment, displacement pressure reduction, accumulative fluid-withdrawal rate, accumulative water production rate and initially see gas point, and data are inserted in raw data table; Gas drive water reaches irreducible water state and terminates experiment after carrying out perm-plug method;

The computing formula of gas, water relative permeability is:

$K_{\mathrm{rg}}=\frac{q_{\mathrm{gi}}}{q_g}---\left(10\right)$

$\frac{K_{\mathrm{rg}}}{K_{\mathrm{rw}}}=\frac{f_g}{f_w}\·\frac{{\mathrm{\μ}}_g}{{\mathrm{\μ}}_w}---\left(11\right)$

In formula:

$q_{\mathrm{gi}}=\frac{\mathrm{\Δ}{V}_{\mathrm{gi}}}{\mathrm{\Δt}}---\left(12\right)$

$q_g=\frac{\mathrm{KA}}{{\mathrm{\μ}}_g}\·\mathrm{\Δp}---\left(13\right)$

$f_g=\frac{\mathrm{\Δ}{V}_{\mathrm{gi}}}{\mathrm{\Δ}{V}_i}---\left(14\right)$

$f_w=\frac{\mathrm{\Δ}{V}_{\mathrm{wi}}}{\mathrm{\Δ}{V}_i}---\left(15\right)$

Wherein:

K _rg---gas relative permeability, decimal;

K _rw---liquid relative permeability, decimal;

Q _gi---gas flow during diphasic flow, mL/s

Q _g---gas flow during single-phase flowing, mL/s

V _w---the accumulative outlet water yield, mL;

Δ V _gi---record the gas increment at interval sometime under atmospheric pressure, mL;

Δ V _wi---record the water increment at interval sometime under atmospheric pressure, mL;

Δ p---displacement pressure reduction, MPa;

A---sectional area, m ²;

Δ t---the time interval, s;

K---gas surveys Absolute permeation, μm ²

Δ V---record the fluid total increment at interval sometime under atmospheric pressure, mL;

F _g---void fraction, decimal;

F _w---water percentage, decimal;

μ _g---injecting gas viscosity; MPa.s;

μ _w---the viscosity of the simulated formation water of saturated rock sample; MPa.s.

In described step 1, rock core drill cut-off footpath 2.50cm, length must not lower than 2 of diameter times, 5 times of no more than diameter.

Experimental provision structure of the present invention is as follows:

Wobble pump connects core holding unit, is provided with tensimeter and confined pressure two-way valve between wobble pump and core holding unit; Gas cylinder is communicated with the side of gas injection apparatus, and the opposite side of gas humidifier connects core holding unit, is provided with pressure regulator valve, is provided with tensimeter and two-way valve between gas humidifier and core holding unit between gas cylinder and gas humidifier; Core holding unit connects the input end of gas-liquid separator, and the output terminal of gas-liquid separator connects gas flowmeter and graduated cylinder, and graduated cylinder connects electronic balance.

Described gas injection apparatus is gas humidifier.

Described core holding unit connects gas-liquid separator by microscopic capillary with a scale.

Advantageous effect of the present invention is as follows:

Easy to use, volcanics gas, water permeability-ratio curve can accurately be measured simultaneously.The experimental study of the method to Low-permeability Gas Reservoirs is significant.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the present invention is further described.

Fig. 1 is a kind of experimental provision structural representation for measuring volcanics gas, water relative permeability.

In figure, 1, gas cylinder, 2, pressure regulator valve, 3, gas humidifier, 4, tensimeter, 5, two-way valve, 6, core holding unit, 7, wobble pump, 8, tensimeter, 9, confined pressure two-way valve, 10, microscopic capillary with a scale, 11, gas-liquid separator, 12, gas flowmeter, 13, graduated cylinder, 14, electronic balance.

Embodiment

Embodiment

With reference to accompanying drawing 1, experimental provision structure of the present invention is that confined pressure wobble pump 7 connects core holding unit 6, is provided with tensimeter 8 and confined pressure two-way valve 9 between wobble pump 7 and core holding unit 6; Gas cylinder 1 is communicated with the side of gas humidifier 3, and the opposite side of gas humidifier 3 connects core holding unit 6, is provided with pressure regulator valve 2, is provided with tensimeter 4 and two-way valve 5 between gas humidifier 3 and core holding unit 6 between gas cylinder 1 and gas humidifier 3; Core holding unit 6 connects the input end of gas-liquid separator 11 by microscopic capillary 10 with a scale, and the output terminal of gas-liquid separator 11 connects gas flowmeter 12 and graduated cylinder 13, and graduated cylinder 13 connects high Accuracy Electronic Balance 14.

During use, wobble pump 7 provides confined pressure to core holding unit 6, is read by tensimeter 8, and can at closedown confined pressure two-way valve 9 to keep confined pressure.Gas flows out from gas cylinder 1, flows through pressure regulator valve 2, injects core holding unit 6 by gas humidifier 3, two-way valve 5, the readable inlet pressure of tensimeter 4.Gas and liquid are by flowing out from microscopic capillary 10 with a scale after rock core, and flow into gas-liquid separator 11, gas flow enters gas flowmeter 12, and liquid flows into graduated cylinder 13, meanwhile, use high Accuracy Electronic Balance 14 to carrying out liquid weighing.

Experimental technique of the present invention comprises the steps:

Step 1, prepared by rock core: get volcanics rock core, drill through diameter 2.50cm, length lower than 2 of diameter times, must not drill through rear polyethylene film and wrap sealing;

Step 2, rock sample perm-plug method and factor of porosity: rock sample is per weighed once after drying 4 hours at 90 DEG C half an hour, until when the relative error of double mass change is less than 5%, records now rock sample quality; Rock sample is put into clamper, uses nitrogen to inject, record displacement pressure reduction, air output, calculate rock sample perm-plug method; Rock core is put into and vacuumizes saturation device, by saturated for the rock core local water vacuumized, and weighing measurement, thus calculate volume of voids and the net porosity of rock sample;

Step 3, apply confined pressure: the rock sample after saturation simulation bottom water is loaded core holding unit, confined pressure pump is utilized to add confined pressure to core holding unit, confined pressure value should lower than formation damage pressure, for extra-low permeability rock sample, its displacement pressure reduction must higher than starting pressure, thus the value of confined pressure should between formation damage pressure and starting pressure value;

Step 4, rock sample gas drive water is tested: the pressure regulator valve opening gas injection apparatus, carries upstream pressure, and carry out gas drive water to core holding unit under given upstream pressure (as: 5MPa); Initial differential pressure must ensure that can overcome end effect does not produce turbulent flow again; Record the displacement time in each moment, displacement pressure reduction, accumulative fluid-withdrawal rate, accumulative water production rate and initially see gas point, and data are inserted in raw data table; Gas drive water reaches irreducible water state and terminates experiment after carrying out perm-plug method;

The computing formula of gas, water relative permeability is:

$K_{\mathrm{rg}}=\frac{q_{\mathrm{gi}}}{q_g}---\left(10\right)$

$\frac{K_{\mathrm{rg}}}{K_{\mathrm{rw}}}=\frac{f_g}{f_w}\·\frac{{\mathrm{\μ}}_g}{{\mathrm{\μ}}_w}---\left(11\right)$

In formula:

$q_{\mathrm{gi}}=\frac{\mathrm{\Δ}{V}_{\mathrm{gi}}}{\mathrm{\Δt}}---\left(12\right)$

$q_g=\frac{\mathrm{KA}}{{\mathrm{\μ}}_g}\·\mathrm{\Δp}---\left(13\right)$

$f_g=\frac{\mathrm{\Δ}{V}_{\mathrm{gi}}}{\mathrm{\Δ}{V}_i}---\left(14\right)$

$f_w=\frac{\mathrm{\Δ}{V}_{\mathrm{wi}}}{\mathrm{\Δ}{V}_i}---\left(15\right)$

Wherein:

K _rg---gas relative permeability, decimal;

K _rw---liquid relative permeability, decimal;

Q _gi---gas flow during diphasic flow, mL/s

Q _g---gas flow during single-phase flowing, mL/s

V _w---the accumulative outlet water yield, mL;

Δ V _gi---record the gas increment at interval sometime under atmospheric pressure, mL;

Δ V _wi---record the water increment at interval sometime under atmospheric pressure, mL;

Δ p---displacement pressure reduction, MPa;

A---sectional area, m ²;

Δ t---the time interval, s;

K---gas surveys Absolute permeation, μm ²

Δ V---record the fluid total increment at interval sometime under atmospheric pressure, mL;

F _g---void fraction, decimal;

F _w---water percentage, decimal;

μ _g---injecting gas viscosity; MPa.s;

μ _w---the viscosity of the simulated formation water of saturated rock sample; MPa.s.

Claims (5)

1., for measuring an experimental technique for volcanics gas, water relative permeability, it is characterized in that comprising the steps:

Step 1, prepared by rock core: get volcanics rock core, rock core drills through rear polyethylene film and wraps sealing;

Step 2, rock sample perm-plug method and factor of porosity: rock sample is per weighed once after drying 4 hours at 90 DEG C half an hour, until when the relative error of double mass change is less than 5%, records now rock sample quality; Rock sample is put into clamper, uses nitrogen to inject, record displacement pressure reduction, air output, calculate rock sample perm-plug method; Rock core is put into and vacuumizes saturation device, by saturated for the rock core local water vacuumized, and weighing measurement, thus calculate volume of voids and the net porosity of rock sample;

Step 3, applies confined pressure: the rock sample after saturation simulation bottom water is loaded core holding unit, and utilize confined pressure pump to add confined pressure to core holding unit, the value of confined pressure should between formation damage pressure and starting pressure;

Step 4, rock sample gas drive water is tested: the pressure regulator valve opening gas injection apparatus, carries upstream pressure, and carry out gas drive water to core holding unit under given upstream pressure; Initial differential pressure must ensure that can overcome end effect does not produce turbulent flow again; Record the displacement time in each moment, displacement pressure reduction, accumulative fluid-withdrawal rate, accumulative water production rate and initially see gas point, and data are inserted in raw data table; Gas drive water reaches irreducible water state and terminates experiment after carrying out perm-plug method;

The computing formula of gas, water relative permeability is:

$K_{\mathrm{rg}}=\frac{q_{\mathrm{gi}}}{q_g}---\left(10\right)$

$\frac{K_{\mathrm{rg}}}{K_{\mathrm{rw}}}=\frac{f_g}{f_w}\·\frac{{\mathrm{\μ}}_g}{{\mathrm{\μ}}_w}---\left(11\right)$

In formula:

$q_{\mathrm{gi}}=\frac{{\mathrm{\ΔV}}_{\mathrm{gi}}}{\mathrm{\Δt}}---\left(12\right)$

$q_g=\frac{\mathrm{KA}}{{\mathrm{\μ}}_g}\mathrm{\Δp}---\left(13\right)$

$f_g=\frac{{\mathrm{\ΔV}}_{\mathrm{gi}}}{{\mathrm{\ΔV}}_i}---\left(14\right)$

$f_w=\frac{{\mathrm{\ΔV}}_{\mathrm{wi}}}{{\mathrm{\ΔV}}_i}---\left(15\right)$

Wherein:

K _rg---gas relative permeability, decimal;

K _rw---liquid relative permeability, decimal;

Q _gi---gas flow during diphasic flow, mL/s

Q _g---gas flow during single-phase flowing, mL/s

V _w---the accumulative outlet water yield, mL;

Δ V _gi---record the gas increment at interval sometime under atmospheric pressure, mL;

Δ V _wi---record the water increment at interval sometime under atmospheric pressure, mL;

Δ p---displacement pressure reduction, MPa;

A---sectional area, m ²;

Δ t---the time interval, s;

K---gas surveys Absolute permeation, μm ²

Δ V---record the fluid total increment at interval sometime under atmospheric pressure, mL;

F _g---void fraction, decimal;

F _w---water percentage, decimal;

μ _g---injecting gas viscosity; MPa.s;

μ _w---the viscosity of the simulated formation water of saturated rock sample; MPa.s.

2. a kind of experimental technique for measuring volcanics gas, water relative permeability according to claim 1, is characterized in that in described step 1, rock core drill cut-off footpath 2.50cm, and length must not lower than 2 of diameter times, 5 times of no more than diameter.

3. a kind of experimental provision for measuring volcanics gas, water relative permeability experimental technique according to claim 1, it is characterized in that structure is as follows: wobble pump (7) connects core holding unit (6), is provided with tensimeter (8) and confined pressure two-way valve (9) between wobble pump (7) and core holding unit (6); Gas cylinder (1) is communicated with the side of gas injection apparatus, the opposite side of gas humidifier (3) connects core holding unit (6), be provided with pressure regulator valve (2) between gas cylinder (1) and gas humidifier (3), between gas humidifier (3) and core holding unit (6), be provided with tensimeter (4) and two-way valve (5); Core holding unit (6) connects the input end of gas-liquid separator (11), the output terminal of gas-liquid separator (11) connects gas flowmeter (12) and graduated cylinder (13), and graduated cylinder (13) connects electronic balance (14).

4. a kind of experimental provision for measuring volcanics gas, water relative permeability experimental technique according to claim 3, is characterized in that described gas injection apparatus is gas humidifier (3).

5. a kind of experimental provision for measuring volcanics gas, water relative permeability experimental technique according to claim 3, is characterized in that described core holding unit (6) connects gas-liquid separator (11) by microscopic capillary (10) with a scale.