CN103713107A - Method for determining matrix damage rate of rock core - Google Patents

Abstract

The invention discloses a method for determining the matrix damage rate of a rock core. The method comprises the following steps: 1, a flow medium is extruded into the rock core from the reverse end of a rock core holder to displace until the flow and a differential pressure are stable, the flow velocity of the flow medium is lower than a critical flow velocity, and a flow medium of a water injection well should enter the rock core from the forward end inlet of the rock core holder; 2, a fracturing fluid filtrate is filled into a high pressure container and is pressurized to make the filtrate enter the rock core, the time and the accumulated filter loss of the filtrate are recorded when the flow of the filtrate starts, and valves at two ends of the holder are closed after the extrusion to make the filtrate residual in the rock core; 3, the permeability K2 of the flow medium damaged by the fracturing fluid filtrate of the rock core is determined through a rock core permeability determination technology before the damage; and 4, the matrix damage rate of the rock core is obtained by calculating according to the above obtained KI and K2. The method allows the determination of the matrix damage rate of the rock core to be well completed, and has the advantages of simple test process, short test time, test cost reduction and accurate test result.

Description

A kind of method of measuring rock core matrix spoilage

Technical field

The present invention relates to a kind of method of measuring rock core matrix spoilage.

Background technology

Rock core, according to the needs of geology preliminry basic research or engineering, is used ring-type hollow bit and other coring tools, from the cylindric rock sample taking out in hole.The ore rock or the ore that from the ore body of Solid Mineral or ore bed, take out, claim the ore deposit heart.Rock core is research and the geologic information important in kind of understanding subsurface geology and mineral products situation.

In ore prospecting and performance history, need to carry out and creep into by the stratigraphic horizon of geological design and the degree of depth, in well, be lowered to coring tool, the rock sample drilling through out.Rock core is to understand subsurface formations and contain directly perceived, the most most realistic data of ore deposit feature.There are two kinds of modes of sidewall sampling and drilling and coring delivery, conventionally take the latter as main.

Within the scope of oil field, must select appropriate well, to relevant oil, gas-bearing formation position, drill through the rock core of some, by observing, analyze and studying, can understand: the 1. epoch on stratum, lithology, deposition characteristics; 2. the physics of reservoir, chemical property and oil-containing, gas, aqueous condition; 3. petroleum source bed feature and source rock index; 4. underground structure situation (as tomography, joint, inclination angle etc.); 5. the basic data of qualitative, the quantitative interpretation of various logging methods; 6. oil, gas, water sport and distribution situation in recovery process, and the variation of stratal configuration; Rock core also can supply the laboratory experiment analysis of water filling or various raising recovery ratio method and volume increase, well stimulation, is the requisite basic data of estimation petroleum reserves, establishment reasonable development scheme, raising reservoir waterflooding effect and recovery ratio.

For obtaining irreducible water saturation, thereby ask accurate initial oil saturation, use oil-base mud coring (seeing drilling fluid) more.For checking oil, the water saturation having changed after exploitation.The sealing core drill technique of China's widespread use sealing fluid protection rock core.USA in recent years has developed maintenance pressure coring, makes the rock core taking out neither be subject to mud influence, can keep the fluid saturation under condition of formation pressure again.But this method complex process, cost is high.

Summary of the invention

The object of the invention is to overcome the shortcoming and defect of above-mentioned prior art, a kind of method of measuring rock core matrix spoilage is provided, this assay method can well complete the mensuration to rock core matrix spoilage, and test process is simple, test duration is short, has reduced testing cost, and test result is accurate.

Object of the present invention is achieved through the following technical solutions: a kind of method of measuring rock core matrix spoilage, comprises the following steps:

(a) first, make flow media clamp-on rock core from core holding unit backward end and carry out displacement, the flow velocity of flow media is lower than critical flow velocity, until flow and pressure reduction are stable, the flow media of water injection well should enter rock core from core holding unit forward end entrance;

(b) by fracturing liquid filtrate dress people high pressure vessel, with pressure source pressurization, make filtrate enter rock core from core holding unit forward end entrance; When filtrate beginning is flowed out, the accumulative total filter loss of writing time, filtrate; After having squeezed, close clamper two ends valve, filtrate is stopped in rock core;

(c) by core permeability assay method before infringement, measure the permeability K2 that rock core is subject to the flow media after the infringement of fracturing liquid filtrate, computing formula is as follows:

$K=0.1\frac{\mathrm{Q\μL}}{\mathrm{\ΔPA}}$

In formula

K---core permeability, μ m ²;

The volumetric flow rate of Q---flow media, cm ³/ s;

The viscosity of μ---flow media, mPas;

L---rock core axial length, cm;

The pressure reduction that Δ P---rock core is imported and exported, MPa;

A---rock core cross-sectional area, cm ².

(d) by the above-mentioned KI recording and K2, calculate rock core matrix damage rate, computing formula is as follows:

$\mathrm{\η}=\frac{K_1-K_2}{K_1}\×100\%$

In formula

η---permeability damage rate, %;

K ₁---rock core squeezes the matrix permeability before fracturing liquid filtrate, μ m ²;

K ₂---rock core squeezes the matrix permeability after fracturing liquid filtrate, μ m ².

In described step (b), the accumulative total filter loss of time, filtrate is accurate to 0.1mL; The residence time is 2h, and experimental temperature is 60 ℃.

In described step (a), be no less than 60min stabilization time.

In sum, the invention has the beneficial effects as follows: can well complete the mensuration to rock core matrix spoilage, and test process is simple, the test duration is short, has reduced testing cost, and test result is accurate.

Embodiment

Below in conjunction with embodiment, the present invention is described in further detail, but embodiments of the present invention are not limited only to this.

Embodiment:

A kind of method of measuring rock core matrix spoilage the present invention relates to, comprises the following steps:

(a) first, make flow media clamp-on rock core from core holding unit backward end and carry out displacement, the flow velocity of flow media is lower than critical flow velocity, until flow and pressure reduction are stable, the flow media of water injection well should enter rock core from core holding unit forward end entrance;

(b) by fracturing liquid filtrate dress people high pressure vessel, with pressure source pressurization, make filtrate enter rock core from core holding unit forward end entrance; When filtrate beginning is flowed out, the accumulative total filter loss of writing time, filtrate; After having squeezed, close clamper two ends valve, filtrate is stopped in rock core;

(c) by core permeability assay method before infringement, measure the permeability K2 that rock core is subject to the flow media after the infringement of fracturing liquid filtrate, computing formula is as follows:

$K=0.1\frac{\mathrm{Q\μL}}{\mathrm{\ΔPA}}$

In formula

K---core permeability, μ m ²;

The volumetric flow rate of Q---flow media, cm ³/ s;

The viscosity of μ---flow media, mPas;

L---rock core axial length, cm;

The pressure reduction that Δ P---rock core is imported and exported, MPa;

A---rock core mode cross section is long-pending, cm ².

(d) by the above-mentioned KI recording and K2, calculate rock core matrix damage rate, computing formula is as follows:

$\mathrm{\η}=\frac{K_1-K_2}{K_1}\×100\%$

In formula

η---permeability damage rate, %;

K ₁---rock core squeezes the matrix permeability before fracturing liquid filtrate, μ m ²;

K ₂---rock core squeezes the matrix permeability after fracturing liquid filtrate, μ m ².

In described step (b), the accumulative total filter loss of time, filtrate is accurate to 0.1mL; The residence time is 2h, and experimental temperature is 60 ℃.

In described step (a), be no less than 60min stabilization time.

The present invention has measured respectively fracturing liquid filtrate to the water saturated rock core of salt and the saturated rock core damage rate of kerosene, rock core basic parameter and rear permeability determination, and result is as shown in the table:

The above, be only preferred embodiment of the present invention, not the present invention done to any pro forma restriction, every foundation technical spirit of the present invention, and any simple modification, equivalent variations that above embodiment is done, within all falling into protection scope of the present invention.

Claims (3)

1. a method of measuring rock core matrix spoilage, is characterized in that, comprises the following steps:

(a) first, make flow media clamp-on rock core from core holding unit backward end and carry out displacement, the flow velocity of flow media is lower than critical flow velocity, until flow and pressure reduction are stable, the flow media of water injection well should enter rock core from core holding unit forward end entrance;

(b) by fracturing liquid filtrate dress people high pressure vessel, with pressure source pressurization, make filtrate enter rock core from core holding unit forward end entrance; When filtrate beginning is flowed out, the accumulative total filter loss of writing time, filtrate; After having squeezed, close clamper two ends valve, filtrate is stopped in rock core;

(c) by core permeability assay method before infringement, measure the permeability K2 that rock core is subject to the flow media after the infringement of fracturing liquid filtrate, computing formula is as follows:

$K=0.1\frac{\mathrm{Q\μL}}{\mathrm{\ΔPA}}$

In formula

K---core permeability, μ m ²;

The volumetric flow rate of Q---flow media, cm ³/ s;

The viscosity of μ---flow media, mPas;

L---rock core axial length, cm;

The pressure reduction that Δ P---rock core is imported and exported, MPa;

A---rock core cross-sectional area, cm ².

(d) by the above-mentioned KI recording and K2, calculate rock core matrix damage rate, computing formula is as follows:

$\mathrm{\η}=\frac{K_1-K_2}{K_1}\×100\%$

In formula

η---permeability damage rate, %;

K ₁---rock core squeezes the matrix permeability before fracturing liquid filtrate, μ m ²;

K ₂---rock core squeezes the matrix permeability after fracturing liquid filtrate, μ m ².

2. a kind of method of measuring rock core matrix spoilage according to claim 1, is characterized in that, in described step (b), the accumulative total filter loss of time, filtrate is accurate to 0.1mL; The residence time is 2h, and experimental temperature is 60 ℃.

3. a kind of method of measuring rock core matrix spoilage according to claim 1, is characterized in that, in described step (a), is no less than 60min stabilization time.