CN102889976B - Method for evaluating experiment for oil replacement through water injection for fracture-cavity carbonate rock oil reservoir - Google Patents

Abstract

The invention relates to a method for evaluating an experiment for oil replacement through water injection for a fracture-cavity carbonate rock oil reservoir, comprising the following steps of: (1) making a rock core model of a fracture-cavity carbonate rock; (2) preparing samples of in-place oil, formation water and injected water, and setting the pressure p1 of water injected at the beginning and the pressure p2 of water injected at the end; (3) restoring the original state, vertically placing the rock core, driving the formation water to enter the rock core from the bottom end, and then, replacing the prepared in-place oil by using the formation water in the rock core; (4) carrying out depletion-drive development experiment on the top end of the rock core to obtain the volumes of crude oil and gas developed when the pressure of the original formation is reduced to P1; (5) carrying out the experiment for oil replacement through water injection to obtain the volumes of crude oil, gas and formation water totally developed after carrying out oil replacement through water injection n times; and (6) calculating the reserve volume of the crude oil in the rock core and the recovery factor of the crude oil after carrying out oil replacement through water injection n times. The invention establishes an experiment method for physically simulating oil replacement through water injection so as to provide a tool and a means for evaluating and optimizing the development way of oil replacement through water injection for the fracture-cavity carbonate rock oil reservoir.

Description

Fractured-cavernous carbonate reservoir water filling is for oily experimental evaluation method

Technical field

The present invention relates to the fracture-pore reservoir water filling of petroleum natural gas exploration field improves oil recovery factor experimental evaluation method for oil.

Background technology

Fractured-cavernous carbonate reservoir reservoir space is special.Due to reasons such as drilling fluid leakages in drilling process, well can only get into fracture-cavity units top usually, and many fracture-cavity units only have individual well to bore chance.Because natural energy is limited, exhaustion formula exploitation recovery ratio is low.Because individual well unit can not set up injection and extraction system, conventional waterflooding extraction mode is also inapplicable.And adopt water filling to replace oil, stratum energy can be supplemented on the one hand, on the other hand due to profit density contrast and gravitational differentiation, inject water and crude oil upwards can be lifted to shaft bottom and extraction, thus effectively improve oil recovery factor.Because current fracture-pore reservoir seepage theory is still immature, this kind of oil reservoir process parameter optimizing cannot be instructed, and Physical Experiment evaluation method can provide guidance to water filling for oily parameter optimization.

Summary of the invention

The object of the present invention is to provide a kind of fractured-cavernous carbonate reservoir water filling for oily experimental evaluation method.The method principle is reliable, easy and simple to handle, and effectively simulating oil deposit water filling can replace oily process, the mining type for evaluation and optimization fractured-cavernous carbonate reservoir provides instrument and means.

For reaching above-mentioned technical purpose, the invention provides following technical scheme:

Fractured-cavernous carbonate reservoir water filling, for oily experimental evaluation method, comprises the following steps successively:

(1) fracture-cave carbonate rock core model is made

Select one piece of length of side at the square carbonate rock rock core of about 30cm, carry out the naturally single seam of man, require that seam face is roughly parallel to arbitrary rib of square and runs through whole rock core, full-hole core is drilled through with 4 inch diameter drill bits, rock core length can reach 10-25cm, require that seam face is positioned at full-hole core central authorities as far as possible and runs through whole rock core vertically, afterwards hole is made to full-hole core inside, the number in hole and size are determined as calculated afterwards by actual oil reservoir solution cavity distribution and size, and hole can not through the edge of rock core and end face, thus a formation manufactured nature singly runs through the core model in all holes in the face of stitching.

(2) prepare in-place oil, formation water and injection water sample, setting starts the pressure p of water filling ₁with the pressure p terminating water filling ₂

Report preparation in-place oil sample according to in-place oil PVT, ensure that the parameter such as the gas-oil ratio of sample under formation temperature with strata pressure, viscosity, volume factor of preparation is reported consistent with in-place oil PVT; According to on-the-spot real data preparation formation water, inject water sample; According to the concrete condition of oil reservoir, setting starts the pressure p of water filling ₁with the pressure p terminating water filling ₂, p ₂can not higher than formation fracture pressure, and p ₂> p ₁.

(3) reset condition recovery is carried out

Rock core is loaded core holding unit and vertical placement, rock core is cleaned, dry, vacuumize, intermediate receptacle is filled formation water, connect automatic pump, pump is set to strata pressure and records pump initial reading V now _fw1, open the gate connected between intermediate receptacle and rock core afterwards, walking unhurriedly with pump drives formation water to enter rock core by bottom, allows the pressure in rock core walk unhurriedly and is increased to strata pressure, record pump reading V now _fw2, the formation water volume entering rock core under strata pressure is rock pore volume V _p:

V _p=V _fw2-V _fw1

Again the in-place oil prepared is injected rock core by top under formation temperature and strata pressure, the formation water from the top down in displacement rock core, until the no longer water outlet of rock core bottom, after a period of stabilisation, record the formation water volume V of extraction _wp, fluid volume V in the pipeline of eliminating rock core two ends _dwimpact after, the in-place oil lower volume V primitively in rock core can be obtained _oi, and then obtain initial oil saturation S _oi:

V _oi=V _wp-V _dw

$S_{\mathrm{oi}}=\frac{V_{\mathrm{oi}}}{V_p}$

In-place oil wherein in rock core lower volume V primitively _oican be used for calculating the crude oil reserve in rock core.

(4) exhaustion extracting experiment is carried out

At the formation temperature, from original formation pressure, exhaustion exploitation is carried out by rock core top.According to original formation pressure and p ₁difference be divided into multistage exhaustion, every grade of exhaustion pressure drop 2-3MPa.Every grade of exhaustion is carried out by the following method: progressively reduce rock core top pressure, make top can be at the uniform velocity fuel-displaced, when top Pressure Drop is to the goal pressure of this grade of exhaustion, keep this pressure till top is no longer fuel-displaced, record exhaustion is to the crude oil volume of this pressure extraction and gas volume.After according to said method carrying out multistage exhaustion, rock core top pressure drop is to p ₁, record from original formation pressure exhaustion to p ₁the crude oil volume V of extraction _o0with gas volume V _g0.

(5) water filling is carried out for oil experiment

At the formation temperature, from pressure p ₁start, injected the injection water of preparation by rock core top to rock core, when pressure gos up to p ₂time stop water filling, record first time water filling volume V _wi1.Close rock core top valve, stablize more than 2 hours, again open top valve and carry out exhaustion exploitation, when pressure drop is to p ₁time close top valve, record by the gas volume V obtained through gas-liquid separator separates of rock core top extraction _g1, the crude oil volume V obtained is separated through oil water separator _o1with formation water volume V _w1, complete first time water filling for oil.

According to said method carry out repeatedly water filling for oil, obtain a series of water filling volume V _wi1, V _wi2, V _wi3..., V _win, extraction gas volume V _g1, V _g2, V _g3..., V _gn, extraction crude oil volume V _o1, V _o2, V _o3..., V _on, produced water volume V _w1, V _w2, V _w3..., V _wn(n is that oily number of times is replaced in water filling).By the crude oil volume V of n water filling for extraction accumulative after oil _otn, gas volume V _gtn, formation water volume V _wtnbe respectively:

V _otn=V _o1+V _o2+V _o3+…+V _on

V _gtn=V _g1+V _g2+V _g3+…+V _gn

V _wtn=V _w1+V _w2+V _w3+…+V _wn

By changing p ₁, p ₂value, can simulate different pressures level, difference is handled up pressure reduction, the recovery process under different injection-production ratio, for optimal water injection provides foundation for oily process system.

Complete last water filling for after oil also exhaustion to abandonment pressure, close rock core top valve, open rock core bottom valve, bottom back pressure is reduced to atmospheric pressure gradually, from all fluids of rock core bottom extraction, measure the crude oil volume V of extraction _on+1, gas volume V _gn+1with formation water volume V _wn+1, for carrying out material balance inspection.

(6) development index is calculated.

According to the lower volume V primitively of the in-place oil in rock core _oiwith the volume factor B of crude oil under formation temperature in PVT report and strata pressure _oi, rock core Crude Oil reserves (representing with volume) N can be calculated:

$N=\frac{V_{\mathrm{oi}}}{B_{\mathrm{oi}}}$

Through n water filling for the oil recovery factor R after oil _onfor:

$R_{\mathrm{on}}=\frac{V_{o0}+V_{\mathrm{otn}}-V_{\mathrm{od}2}}{N}\×100\%$

Wherein V _od2for fluid volume in the pipeline of rock core top;

N-th water filling is for the moisture content f of oil _wn, gas-oil ratio GOR _nbe respectively:

$f_{\mathrm{wn}}=\frac{V_{\mathrm{wn}}}{V_{\mathrm{wn}}+V_{\mathrm{on}}}$

${\mathrm{GOR}}_n=\frac{V_{\mathrm{gn}}}{V_{\mathrm{on}}}$

For improving accuracy and the reliability of experiment, carry out material balance inspection to volume of gas, method is as follows:

Total dissolved gas V of in-place oil in experimental system _gat1for:

V _gat1=V _wp×GOR _i

Wherein GOR _ifor primary Korean pine forest.

The actual total amount V of gas in experimentation _gat2for:

V _gat2=V _g0+V _g1+V _g2+V _g3+…+V _gn+V _gn+1+V _p

V _gat1with V _gat2relative error namely think within 2% and meet the requirements.

Compared with prior art, the present invention establishes the experimental evaluation method of a kind of water filling for oily physical analogy, for the water filling of evaluation and optimization fractured-cavernous carbonate reservoir provides instrument and means for oily mining type.

Detailed description of the invention

The present invention is further illustrated below in conjunction with example.

Fractured-cavernous carbonate reservoir water filling, for oily experimental evaluation method, comprises the following steps successively:

(1) fracture-cave carbonate rock core model is made, select one piece of length of side at the square carbonate rock rock core of about 30cm, carry out the naturally single seam of man, and drill through full-hole core with 4 inch diameter drill bits, carry out making hole, hole through the edge of rock core and end face, can not be formed a manufactured nature and singly runs through the built-up pattern in all holes in the face of stitching;

(2) prepare in-place oil, formation water and injection water sample, setting starts the pressure p of water filling ₁with the pressure p terminating water filling ₂;

(3) reset condition recovery is carried out to rock core, under formation temperature and original formation pressure, first with formation water saturated core from bottom to top, then with the formation water in in-place oil from the top down displacement rock core;

(4) carry out exhaustion extracting experiment from rock core top, record from original formation pressure exhaustion to p ₁the crude oil volume V of institute's extraction _o0;

(5) water filling is carried out at the formation temperature for oil experiment, when rock core pressure is p ₁time, injected the injection water of preparation to rock core by rock core top, when pressure gos up to p ₂and stop water filling after a period of stabilisation, record first time water filling volume V _wi1, closes rock core top valve, stablize more than 2 hours, again open top valve and carry out exhaustion exploitation, and record is by the gas volume V of rock core top extraction _g1, crude oil volume V _o1with formation water volume V _w1, complete first time water filling for oil, according to said method carry out repeatedly water filling for oil;

(6) indexs such as the crude oil reserve in calculating rock core and recovery ratio, and carry out material balance inspection.

Claims (1)

1. fractured-cavernous carbonate reservoir water filling is for oily experimental evaluation method, comprises the following steps successively:

(1) selecting party block carbon Carbonate Rocks rock core, carry out the naturally single seam of man, drill through full-hole core, seam face is positioned at full-hole core central authorities and runs through whole rock core vertically, hole is made to full-hole core inside, the number in hole and size are determined as calculated afterwards by actual oil reservoir solution cavity distribution and size, and hole through the edge of rock core and end face, can not be formed a manufactured nature and singly run through the core model in all holes in the face of stitching;

(2) report preparation in-place oil sample according to in-place oil PVT, according to on-the-spot real data preparation formation water, inject water sample, setting starts the pressure p of water filling ₁with the pressure p terminating water filling ₂;

(3) reset condition recovery is carried out, rock core is loaded core holding unit and vertical placement, rock core is cleaned, dry, vacuumize, formation water is driven to enter rock core by bottom with pump, allow the pressure in rock core walk unhurriedly and be increased to strata pressure, again the in-place oil prepared is injected rock core by top under formation temperature and strata pressure, the formation water in displacement rock core, obtain the in-place oil lower volume V primitively in rock core _oi;

(4) at the formation temperature, from original formation pressure, carry out exhaustion extracting experiment by rock core top, obtain from original formation pressure exhaustion to p ₁the crude oil volume V of extraction _o0with gas volume V _g0;

(5) water filling is carried out for oil experiment, at the formation temperature, from pressure p ₁start, injected the injection water of preparation by rock core top to rock core, when pressure gos up to p ₂time stop water filling, record first time water filling volume V _wi1, close rock core top valve, stablize and within more than 2 hours, open top valve again and carry out exhaustion exploitation, obtain the gas volume V of rock core top extraction _g1, crude oil volume V _o1with formation water volume V _w1, according to said method carry out repeatedly water filling for oil, obtain by the crude oil volume V of n water filling for extraction accumulative after oil _otn, gas volume V _gtn, formation water volume V _wtn;

(6) according to the lower volume V primitively of the in-place oil in rock core _oiwith the volume factor B of crude oil under formation temperature in PVT report and strata pressure _oi, calculate rock core Crude Oil reserves N by following formula and represent with volume:

$N=\frac{V_{\mathrm{oi}}}{B_{\mathrm{oi}}},$

Calculated through n water filling for the oil recovery factor R after oil by following formula _on:

$R_{\mathrm{on}}=\frac{V_{o0}+V_{\mathrm{otn}}-V_{\mathrm{od}2}}{N}\×100\%$

Wherein V _od2for fluid volume in the pipeline of rock core top.