RU1777048C - Method for determining wettability of collector rocks - Google Patents

Abstract

Usage: the invention relates to mining and can be used in determining the estimated parameters of reservoir rocks, estimating oil and gas reserves, designing rational systems for developing oil fields by water flooding. SUBSTANCE: permeability, open porosity, porosity parameter, saturation parameter, interfacial tension at the oil-water interface are experimentally determined, double capillimetry is performed by displacing water with oil and oil by water, setting the pressure values to a certain value. The thickness of the water and oil films held by the pore surface of each sample is determined, according to the data of the latter, the samples are separated into hydrophilic and hydrophobized, and the contact angles are determined by the corresponding formulas. A correlation relationship is established between the wetting angle and the humidity parameter, and a reference graph is plotted for the dependence of the wetting angle on the humidity parameter. The reservoir moisture parameter is calculated from the well log data, and the wettability of the rocks is determined from the fixed value of the last from the reference graph. 1 wp 3 ill. Yo

Description

The invention relates to mining and can be used in interpreting data from geophysical surveys of wells, calculating oil and gas reserves, designing rational systems for developing oil fields.

A known method for determining the wettability of porous materials is that the rock sample is preliminarily saturated with the studied liquid and then kept in the liquid polar opposite to the studied one until the droplets formed on the surface of the sample are fixed in shape, the geometrical dimensions of which calculate the contact angle of contact.

The disadvantage of this method is that measurements are close to surface, which reduces the reliability of the wettability determinations of porous materials.

The closest technical solution is a method for determining the wettability of reservoir rocks, including sampling from the studied formations, extracting and drying them, measuring the permeability of the samples, saturating them with formation water, measuring

VJ VI VI

g

With

the porosity parameter, conducting capillary rimetry by stepwise displacing water and each sample with fluid, plotting the dependence of capillary pressure on water saturation, determining the residual water saturation and average capillary pressure for each sample, measuring the interfacial tension at the oil-water interface and calculating the edge wetting angle.

The main disadvantages of the prototype are the following: the inability to determine the wetting angle of hydrophobized rocks, it is limited only by the scope of laboratory definitions, i.e. there is no transition from laboratory definitions to field geophysics, the method has a low information content.

The aim of the proposed method is to increase the reliability of the determination of the integral wettability of rocks by formation fluids.

The goal is achieved by the fact that in the known method, which consists in taking samples from the studied formations, extracting them, drying, measure the permeability of the samples, saturate them with formation water, measure the porosity parameter. Then, capillimetry is carried out by stepwise displacement of water from each sample with oil, and curves of the dependence of capillary pressure on water saturation are plotted. After that, the residual water saturation and average capillary pressure for each sample are determined, the interfacial tension at the oil-water interface is measured, and the contact angle is calculated.

The method differs from the known one by the presence of new operations: in addition, the volume of each sample and the volume of water entering the sample at saturation are measured, the open porosity of each sample is determined from the ratio of the volumes of water and the sample, a sample of samples taken from various parts of the reservoir is selected with a wide range changes in their permeability and porosity, saturate the samples with reservoir oil, keep them under saturation until stabilization of the adsorption processes by monitoring the saturation process to stabilize the electrical conductivity stiffness of each sample, displace oil from them with produced water, setting a number of discrete pressure values, and for each discrete pressure value, the volume of displaced oil is measured, and the curves of the dependence of capillary pressure on oil saturation are measured.

the residual oil saturation of the samples is determined, the median water and oil saturation are calculated from the obtained values of the residual water and oil saturation from the ratio:

Md

1 TO

about. at.

K l Kn

Md

- (1 - Co.)

  O.V. , Cr. N.

where Кв, Кн - median water and oil saturation;

Co., Ph.D. - residual water and oil saturation;

Using the previously experimentally obtained parameters: the parameter of porosity, open porosity, permeability, residual water and oil saturation, median water and oil saturation, the absolute hydraulic radius of pores and hydraulic radii of pores are determined taking into account the residual water saturation and oil saturation at median saturation for each sample according to the formulas:

Md

Goabs V ,, o2

0 rOB, Md

Md

, Md

URPK.OKPRKV G ° VnKn.oKnp (.B)

(via ./ about GoN Ur2

URPK.OKPRKKN

Md

Md

where Goabs is the absolute hydraulic radius of the pores of the sample;

Го.вШ, Го.н d - hydraulic radii of the pores of the sample, taking into account the residual water saturation and median oil saturation:

y is the pore channel shape factor;

RP is the parameter of porosity; Kp o - open porosity; CRC - permeability;

determine the thickness of the films of water and oil held by the pore surface of each sample at median saturation and ratios

fifty

Tv - (Go.abs Go.v J 2;

, - ir Md Md about. Tn - (Go.o Go.n),

according to the data of the latter, the samples are separated into hydrophilic and hydrophobized, the value of the contact angle for hydrophilic rocks is determined by the formula:

pMd

& -Z RpKpoMK -Kov):

0 °.

where Pkv d is the average value of capillary pressure at a median water saturation;

(5Нв - interfacial tension at the oil-water interface:

y is the pore channel shape factor;

RP is the parameter of porosity;

Kp.o - open porosity;

CRC - permeability;

Qu, Co in - median and residual water saturation;

for hydrophobized rocks, the hydrophobicity coefficient is additionally determined equal to the ratio of the hydraulic radii of pores taking into account oil saturation and residual water saturation

Md

and . Md / r Gon / Go.

Md

where ft is the hydrophobic coefficient ™;

Гон, г0.в hydraulic radii of the pores of the sample, taking into account the median oil saturation and residual water saturation;

determine the value of the contact angle for hydrophobized rocks by the formula:

at 180 ° - arccos (/ fcos 0B); 90 ° 0 „180 °,

on a previously selected sample of samples saturated with formation water, the electrical resistance of each sample is measured at 100% and residual water saturation, with respect to which a saturation parameter is set; determining a moisture parameter equal to the product of the porosity parameter and the saturation parameter of each sample; establish a correlation between the previously determined wetting angle and the humidity parameter: build a reference graph of the dependence of the wetting angle on the humidity parameter for a particular field: from the data of geophysical studies of the wells, the porosity parameter and the saturation parameter of the formation under study are determined, based on which formation moisture parameter, and according to a fixed value of the latter according to the reference graph, the dependence of the wetting angle on the humidity parameter is determined The wettability of the rocks.

Fig. 1 is a diagram of an apparatus for implementing the method of the invention; Fig. 2 shows the dependence of capillary pressure on water and oil saturation; in Fig.Z - dependence of the wetting angle of moisture.

The device comprises a housing 1 and a camera

2 hydraulic compression of the rock sample 3, flanges 4 and 5, an elastic sleeve 6 for the rock sample 3 and a semipermeable membrane 7, pistons 8 and 9 with inlet and outlet channels 10 and 11. The pistons 8 and 9 are electrically isolated from the housing 1. The housing 1 has an inlet channel 12 for supplying oil to the chamber 2 from the hydraulic cylinder (not shown in Fig. 1).

5 the housing 1 is enclosed in a casing 13 having

grooves 14 in which the electric heating element is mounted. The outlet channel 11 is hydraulically connected by a pipe 15 to a microburette 16. A resistivity measuring device 17 of the rock sample 3 is connected to the pistons 8 and 9 under. The measuring electrodes are the ends of the pistons 8 and 9, pressed against the rock sample 3 and a semipermeable membrane

5 7 and isolated from the housing 1 and other elements of the device. A fluid supply system (not shown in Fig. 1) is connected to the supply channel 10 and comprises piston separators with oil and water.

0 manifolds. manometers.

The semipermeable membrane 7 is made of compressed nickel powder by sintering it in dissociated ammonia.

5 The method is carried out as follows.

At the field, rock samples are taken from drilled wells from the studied formations, and extracted by

0 cold extraction in hexane in order to preserve their initial wetting properties in the same way, then the samples are dried to the constant of their weight.

Each sample 3 is placed alternately5 but in the elastic cuff 6 of the device and by applying crimping pressure from the hydraulic cylinder (not shown in Fig. 1) to the elastic cuff 6 and pistons 8, create effective pressure on the rock sample 3 and simulate the temperature equal to the reservoir temperature using an electric heating element mounted in a casing 13. After creating 3 formation conditions on the rock sample, measure it by pressure and temperature

5, the permeability of CRC by supplying a gaseous agent to the supply channel 10. After determining the permeability of the sample, the crimp pressure is vented by the hydraulic cylinder (not shown in Fig. 1) through the supply channel 12.

Then the samples are weighed and saturated with formation water. It is re-weighed, their geometric dimensions are measured - diameter and length, from which the area S and volume V0 are calculated. The difference in the weights of the water-saturated and dry samples divided by the specific gravity of the produced water determines the volume of water VB that entered the sample at saturation, and its open porosity Kp.

Kp.o. - VeVo.

Next, the water-saturated sample 3 is re-placed in the elastic cuff 6 and conditions are created on it, close to the reservoir pressure and temperature (similarly, when measuring permeability). When the electrical resistance of sample 3 is stabilized, which indicates the completion of the deformation processes, take its readout R using electrical resistivity measuring instruments 17 and, knowing the cross-sectional area of the sample S, its length I, calculate the electrical resistivity of a fully water-saturated sample / EEC RS / I, and its porosity parameter Pn is defined as the ratio of the rvp to the electrical resistivity of the water rv saturated with the pore of the sample

RP RVP / RV

Note that if water is used to determine porosity, the latter will characterize the moisture capacity of the pore space of the rock sample. For practical purposes, fixing the amount of water by the electrical resistivity of a water-saturated sample is based on the saturation of the sample with water.

After that, on the test sample 3, having previously placed a semipermeable membrane 7 on the end face of the piston 9, capillimetry is carried out by stepwise displacing water from the sample 3 with oil supplied through the supply channel 10 of the piston 8. In this case, water is displaced from the sample pores through the semipermeable m. the membrane 7 into the outlet channel 11 of the piston 9 and enters through the pipe 15 into the microburette 16. It should be noted that the entire system including the outlet channel 11, the pipe 15 and some part of the microburette (up to zero) but (before .issledovany)

filled with formation water and evacuated. The volume of displaced water from the pores of sample 3 is recorded in the microburette 16. Based on the obtained current values of capillary pressures Pk and water saturation Kv, the dependence of capillary pressure on water saturation Pk f (KB) is constructed. The non-decreasing water saturation value taken from this curve is taken as

residual water saturation Kv. Calculate the median water saturation Kv. for each sample 3 of the ratios:

Md

Md

1 -

1 Co.

(1).

From the Pk f (KB) plot, the average capillary pressure PkvMa at the point of intersection of the median water saturation line with the Pt (Kv) curve is determined from the median water saturation Kv obtained, which corresponds to the median pore radius.

Then, its specific electric resistance RNP with residual water saturation Ko.v. is measured on sample 3. and the ratio of the specific electrical resistances of the sample at residual water saturation and 100% water saturation determines its saturation parameter Rn:

Rn / ONP / RVP

(2).

The moisture parameter Pw is then calculated for each sample as the product of the porosity parameter Pn and the saturation parameter Pn (p Pp1 Pn). Interfacial tension at the oil-water interface is measured

rotating drop method or other known method.

Determining experimentally the above parameters, select a sample of samples taken from various

parts of the reservoir, with a wide range of changes in their porosity and permeability.

Then, the samples are saturated with reservoir oil under vacuum in a desiccator and kept under saturation until stabilization

adsorption processes. The saturation completion process is monitored by measuring the electrical resistance of each sample, placing them alternately in the device (fi g. 1). As soon as the electrical resistance of the sample stabilizes, it is believed that the process of saturating it with oil has been completed. After that, the oil-saturated sample with residual water is weighed, the volume of oil that enters it at saturation is determined by weight, placed in an elastic cuff 6 and conditions are created on it that are close to reservoir pressure and temperature. After that, having previously placed a semipermeable membrane 7 on the end face 5 of the piston 9, the oil is displaced from the sample 3 with produced water, setting a number of discrete pressure values P. At each discrete value Pk, the volumes of displaced oil in the microburette 16 are measured The dependence of the capillary pressure P "on the oil saturation K" for each sample Pk f (KH) is plotted. Non-decreasing oil saturation. taken from this curve, 15 is taken as the residual oil saturation Co. The median oil saturation is calculated (similarly, the median

Md

Then, to obtain absolute pore radius, you should write as

Md

Goabs Vvp2 | f I / k-Md o.aos ukpK-r oKprKa

The physical meaning of the introduced expression (7) is the value of the residual saturation. consists of residual water filling the filter channels, which are not involved in the liquid, in relation to the direction, and is non-conductive (unfiltered rock sample 3).

The expression for hydraulic pore taking into account oil saturation at median saturation of KHM

water saturation) Кн for each of the other formulas (8) takes the form:

Sample 3 from the ratio:

twenty

Md

Kn - (1 Ko.v.) -

1 - Co. - Ph.D.

According to previously obtained experimentally parameters: Kp permeability, open porosity Co.p., porosity parameter Pp, residual water and oil saturation Co.v., Co.N., median water and oil saturation Kvsh, Kn are determined for each Sample hydraulic pore radii as follows.

It is known that the Laplace equation expressing the relationship between the capillary pressure Pk, the interfacial tension 5Нв, the hydraulic radius of pores r0 and the contact angle of contact of the explosives, has the form:

 in -go

He is in

and

(4)

In turn, the hydraulic radius of the pores is equal to:

r ° VnKn.oKnp

(5)

Md.

We introduce the concept of the effectiveness of tortuosity uv:

(6) Cl.o. (Qu - Co.v.)

Product of RP Kp.o. in formula (5) there is nothing but tortuosity p; then, substituting K8 - K0.v. in expression (5), we obtain a formula for determining the hydraulic (effective) pore radius of a sample taking into account residual water saturation at a median water saturation Kv

Gov

Md

VnKn.oKnp (KMd - Co.) (P

Then, to obtain the absolute hydraulic radius of pores, expression (7) should be written as

Md

Goabs Vvp2 | f I / k-Md o.aos ukpK-r oKprKa

(8).

The physical meaning of introducing residual water saturation into the calculated expression (7). consists in the fact that the residual water fills the pore channels transverse with respect to the filtration direction and are not involved in the fluid filtration, and is, as it were, a part of the non-conductive (unfiltered) skeleton of rock sample 3.

The expression for the hydraulic radius of the pores taking into account the oil saturation r0n at the median saturation KHMd, similar

Rut

Md

URPK.OKPRKKN

(9)

25 30 After determining the hydraulic pore radii for each sample, the thicknesses of water films TB and oil gn held by the pore surface of each sample at median saturation are determined from dependences (7), (8) and (9) from the ratios

Gv - (Goabs - Gov) 2, Gn (G08Sh - rc.HMd) 2

(YU)

(eleven)

0

5

0

5

5

The coefficient 2 in equations (10) and (11) is introduced because the ratio between the hydraulic r0 and the geometric r pore radii has the form r 2 r0, and the radii must be converted to geometric dimensions to determine the thickness of the water and oil films.

According to the definitions of the thicknesses of water films of TV and oil Hz, the studied samples are separated into hydrophilic and hydrophobized samples as follows:

if gv tn - the rock is hydrophilic;

if gn gv - the breed is hydrophobic;

if gv ng - the rock has neutral wettability (it is equally wetted with water and oil).

The validity of this classification of rocks as hydrophilic and hydrophobized is based on wetting theory. It should be noted that the thicker the film of the first fluid is retained relative to the second, the rock is predominantly wetted by the first fluid and vice versa.

Then, based on this classification, the contact angle value for hydrophilic Oa rocks is determined by the formula

p Md

) .oKnp (KSM-Ko.B.):

0 ° (12)

where is the average value of capillary pressure at a median water saturation;

5nv — interfacial tension at the oil – water interface;

γ is the pore channel shape factor equal to 2.5 on average;

RG1 - parameter-porosity;

Kp.o - open porosity;

CRC - permeability;

KB, Co. - median and residual water saturation.

For hydrophobized rocks, the hydrophobicity coefficient is additionally determined. It is equal to the ratio of hydraulic pore radii taking into account the median oil saturation r0HMd and residual water saturation r0vMc1.

Md /, Md

/ 3 GonMS7Gov

(thirteen).

Oq

The value of the contact angle for hydrophobized rocks is determined by the formula:

5

0

Q

As an example, figure 2, 3 presents the results of these studies on samples of reservoir rocks of the Middle Cambrian age Genchi oil field (Lithuania),

Figure 2 shows two combined dependences of the capillary pressure Pk on the water saturation Kb, Kk f (KB) and oil saturation Kch, PK f (KH) for one sample. The abscissa shows the water saturation Kb and oil saturation Kn. Moreover, the amount of water saturation Kw along the ascis axis increases from 0 to 100%, and the value of oil saturation Kw decreases from 100% to 0.

The curves describe the dependence of capillary pressure on water saturation (curve a) and oil saturation (curve b).

With a water saturation Kb of 0.136, the capillary pressure Pk tends to infinity. This value of water saturation is taken as the residual water saturation of the rock sample.

Similarly, for an oil-saturated sample with residual water, a residual oil saturation value of Ko.N. of 0.450 is obtained. Intersection. Lines of Median Water Saturation Qug

Md

(TO

Md

1 KOE

)

bn 180 ° - arccos (/ cos # в); 90 ° # n 180 ° (14).

Then, according to a previously studied sample of samples, using the methods of mathematical statistics, a correlation relationship is established between the previously determined contact angle of contact 00, inside and the humidity parameter Pw (Pw Pn Pn).

A reference graph of the contact angle of 0 wt. from humidity parameter PW, OB. f (Pw) for a particular field.

Then, according to the standard methodology, the porosity parameter Pn and the saturation parameter Pn of the formation under study are determined according to the standard methods of well analysis, based on which the formation moisture parameter Pw is calculated. According to the fixed value of the latter according to the reference graph, the dependence of the contact angle of wetting on the moisture parameter QS.H. - G (Ru) the wettability of the rocks is distributed, without resorting to the above laborious laboratory studies of the samples.

5

0

,.

"To

Md

with curve a gives a Pkv value of 0.0015 MPa, which is used to determine the wetting angle of hydrophilic rocks.

Fig. 3 shows a reference graph of the contact angle of 9bh versus the moisture parameter Pw, which makes it possible to evaluate the wettability of the rocks with formation fluids for the Genchi oil field.

The criterion for dividing the reservoir rocks into hydrophilic and hydrophobized is the point M, which corresponds to a sharp inflection of the $ v. f (Pw). Theoretically, this point corresponds to a contact angle of 90 ° (neutral wettability).

Draw a neutral wettability line parallel to the ordinate axis through point M, the intersection of which with the axis of abscissa gives a moisture parameter Pw of 600 equal to the same wettability of the rocks with water and oil. If, according to the data of geophysical studies of wells, a humidity parameter is obtained

Pw 600, the rocks are hydrophilic, while PW 600, the rocks are hydrophobic. From the current values of the formation Pw, it is not difficult to find the value of the boundary angle 0V from the reference graph.

The study of reservoir rocks for the wettability of their pore surfaces with oil and water is a necessary and integral stage of work for reliable substantiation of calculation parameters, determination of oil and gas reserves, and design of rational systems for developing oil fields by water flooding.

Despite the considerable laboriousness of laboratory research, the method provides for the complexity of the radiation of the petrophysical properties of the rocks, in connection with which it has significant informativeness, which is necessary to solve the above problems. Therefore, the technical and economic efficiency of the proposed method, which allows to increase the information content, objectivity and reliability of the determination of the integral wettability of rocks by formation fluids, improves the efficiency of exploration work for oil and gas, and, as a result, promotes a rational distribution of material and labor resources in field development process.

Claims (2)

The claims 1, A method for determining the wettability of reservoir rocks, including sampling samples from the studied formations, extracting and drying them, measuring the permeability of samples, saturating them with formation water, measuring porosity parameters, performing capillimetry by stepwise displacing water from each sample with oil, plotting curves dependences of capillary pressure on water saturation, determination of residual water saturation and average capillary pressure for each sample, measurement of interfacial tension on a grain oil-water and the calculation of the contact angle, characterized in that, in order to increase the reliability of determining the integral wettability of the rocks with formation fluids, the volume of each sample and the volume of water entering the sample at saturation are additionally measured in relation to the volumes of water and the sample - divide the open porosity of each sample, select a sample of samples taken from various parts of the reservoir, with a wide range of changes in their permeability and porosity, saturate the samples with reservoir oil, maintain them under saturation By destabilizing the adsorption processes by controlling the saturation process by stabilizing the electrical resistance of each sample, oil is displaced from them with formation water, a number of discrete pressure values are set, and the volumes of displaced oil are measured at each discrete pressure value, and the curves of the capillary pressure are plotted from the oil saturation, which determine the residual oil saturation of the samples, from the obtained values of the residual water saturation and oil saturation, calculate the median water and oil saturation from ratios ,, Md - I 1 TO, o.v. Md Knma - (1 - Co.) 1 - Co. - Ko.N. where apt. Кн - median water and oil saturation; Ko.v, Ko.n - residual water and oil saturation; The previously obtained parameters: the parameter of porosity, open porosity, permeability, residual water and oil saturation, median water and oil saturation, determine the absolute hydraulic radius of pores and hydraulic radii of pores taking into account the residual water saturation and oil saturation at median saturation for each sample according to the formulas Md Goa6c VnKn.oKnpKMd I W VSKn.oKnp (Kr-Ko.B) .Go. Mr. N Md VЈp2ir South U.Nugpk.p o1Chpr1chn where g.abs is the absolute hydraulic radius of the pores of the sample; Go. g0.n - hydraulic radii of the pores of the sample, taking into account the residual water saturation and median oil saturation; y is the pore channel shape factor; RP is the parameter of porosity; Kp.o - open porosity; CRC - permeability then determine the thickness of the films of water and oil held by the pore surface of each sample at median saturation from the ratios Gv (go.absSh - Go.eMs)) - 2; Mr. . ir Md r Md h (Go.V Go.n j -L according to the data of the latter, samples are divided into hydrophilic and hydrophobized, the value of the contact angle for hydrophilic rocks is determined by the formula a-ry 3Нв РпКп.оКпр (Ке - К O.BJ 0 ° where PkvM (1 - average value of capillary pressure at median water saturation; 5nv - interfacial tension at the oil-water interface: y is the pore channel shape factor; RP is the parameter of porosity; Kp.o - open porosity; Kv, Ko.v - median and residual water saturation, for hydrophobized rocks, the hydrophobicity coefficient is additionally determined equal to the ratio of the hydraulic radii of pores taking into account oil saturation and residual water saturation rMd / 3 1 ° g rMd Go.V. where / is the hydrophobic coefficient ™; ro.HMd, g0.v - hydraulic radii of the pores of the sample taking into account the median oil saturation and residual water saturation, . 1 determine the value of the contact angle for hydrophobized rocks by the formula vn 180o - arccos cos #B), , geophysical surveys are underway all drilled in the field wells. 2. The method according to p. 1, characterized in that, in order to increase the information content by determining the wettability rocks with reservoir fluids in all wells drilled in the field, in a previously selected sample of samples saturated with reservoir water, the electrical resistance of each sample is measured at 100% and residual water saturation, according to which the saturation parameter is determined, the humidity parameter is determined, which is equal to the product of the porosity parameter and the saturation parameter of each sample, establish a correlation between the previously determined wetting angle and the humidity parameter, build a reference graph of the dependence of the wetting angle on the humidity parameter for the rocks of a particular field; according to geophysical research wells determine the parameter of porosity and formation saturation parameter, on the basis of which the parameter is calculated formation moisture, and the wettability of the rocks is determined from the fixed value of the latter according to the reference graph of the dependence of the contact angle on the moisture parameter. 110s MPo 0 ° g o, k ™ o.6 av k6 108 о.B.O.CH 0.2 Kn O2OO W 60О 800 / LLC VOO / (Р „-РМ) Hurray, regression and " o -tiitf + o.z9pM-a.t4- / dspЈ, .9зо & ifi