SU894470A1 - Device for determination of of bounded water content in a rock - Google Patents

Description

The invention relates to the technically-based determination of the content of bound or residual water saturation in a rock from capillary pressure curves. A device for measuring capillary pressure using a semipermeable septum 1 is known. Its main disadvantage is that the whole cycle of determining the capillary pressure curve takes a long time. The closest to the technical essence and the achieved result to the proposed is a device for determining the content of bound water in the rock, which contains rifugu prices, on the rotor of which there are glasses with core holders for samples of rock with pallets. To measure the capillary pressure with this device, the sample of the rock extracted and weighed after drying is saturated with liquid and weighed again after which it is fixed in the core holder. On the rotor four core holders are fixed. Then they turn on the centrifuge and gradually increase its rotational speed to the initial maximum. The number of revolutions remains unchanged until a state of equilibrium is reached, i.e. until the flow of fluid from the sample to the podoids is stopped. When at a given rotational speed equilibrium is reached, the amount of liquid in the sump (glass test tube) is counted, after which the rotational speed of the centrifuge is removed. If the rock sample is rotated in a centrifuge at different constant speeds, the necessary data can be obtained to create a complete capillary pressure curve. The curve is plotted in a known manner in terms of capillary pressure — residual water saturation, from which it is possible to determine the content of bound water or residual water saturation at any point of the formation at a height above the free surface of the water. The main advantage of determining the content of bound water using a centrifuge is to conduct experiments 2 quickly. However, the experience of examining rock samples with low permeability characteristic of deep deposits (and their number increases in the future) shows that the process of displacing liquid from such rocks by compared with in asocormeable rocks and in the centrifuge proceed slowly, i.e. her-: whether the entire capillary pressure curve for high-permeable rocks can be obtained in a few hours, oh for low-permeable rocks this time can be calculated in days.

The purpose of the invention is to reduce the time to determine the content of bound water.

This goal is achieved by the fact that in a device for determining the content of bound water in a rock containing a centrifuge, on the rotor of which glasses are attached with core holders for rock samples with pallets, each core holder is made up of sections placed at different distances from Rotor rotation axes, each section being provided with an individual pallet.

Figure 1 shows a diagram of the centrifuge; Fig. 2 is a diagram of a glass with a stacked core holder for rock samples with pallets; FIG. 3 is a plot of capillary pressure curve plotted from measurement results.

A device for determining the content of a bound wave in a rock by a capillary pressure curve is a centrifuge, to the rotor 1 of which glasses 2 with core holders are attached, which are made of sections 3, located at different distances from the rotor axis. Each of which contains sample 4 of the studied rock with a pallet 5 for collecting the fluid displaced from it. Cup 2 is worn with a cover b.

The device works as follows.

In each section 3 of the compacted core holder, into the bottom of which a graduated glass tray 5 is inserted to collect the displaced fluid, an extracted specimen 4 of the rock is collected, which must be weighed before and after being saturated with 100% water or a formation water model. Then sections 3 with samples of rock 4 and pallets 5 are inserted into cups 2, which are covered with covers 6.

After that, a centrifuge is turned on and smoothly turns out at such a rotational speed that in the rock that is remote from the rotor axis 1 of rock sample 4 creates a pressure drop corresponding to the maximum height (position) of the rock above the free surface of the water in the reservoir. At the same time, in the remaining rock samples, the pressure drops created will be less than the maximum by as many times as many times as these samples are closer to the rotor axis 1.

The force applied in the center of sample 4 of the rock — capillary pressure is determined by converting the rotational speed into units of force using the formula

, 11.10- (p, j,), (1) where P is the pressure drop between water

and air; O. and Si- density of water and air,

J t. G / CM

n is the number of revolutions per minute;

h - sample height, cm

d - rotation radius, see. When the release of water from rock samples 4 is stopped (a stroboscopic lapma is used for counts in pallets of 5 levels of displaced water), they are removed from the centrifuge and weighed to control the content of bound water determined by the formula

.ioo, (2)

% Gu

where oi is the content of bound water as a percentage of the pore volume;

G4 S weight of dry sample, g; sample weight after centrifugation, g;

Vn pore volume in sample

L l

(Vyi - - (Gjj is the weight of the sample saturated with water, g; g is the specific gravity of water at a given temperature.

According to the data obtained, for example, four to five points (4-5 samples are placed into each core holder), a graph of the dependence of the content of bound water in the rock on capillary pressure is plotted - the capillary pressure curve for laboratory conditions.

According to the known dependencies, capillary pressure in the formation conditions is calculated from laboratory data and results in a saturation plot of the height of the reservoir, which is not shown here.

Thus, for example, a CLR centrifuge (a centrifuge laboratory refrigerated, mass-produced by the Frunzensky plant, equipped with a flat Core holder, becomes a device that provides an express determination of the content of bound water in low-level rocks.

Obviously, the determination time, as compared with the known devices, is reduced by as many times as many times more samples of the same rock are examined simultaneously with different pressure drops (capillary pressures).

With standard dimensions of the investigated samples (with a length and a diameter of 3 s, the proposed device makes it possible to reduce the detection time, for example, four to five times, since it provides, at one speed of rotation, the acquisition of data — four to five points, necessary to construct a capillary curve pressure.

Claims (2)

1. US patent number 4112836, CL.73 / 23, 1978. o 2. Amiks J. and lr. Oil reservoir physics. M., Gostoptekhizdat, 1962, pp. 1336-137 (prototype).