SU1619106A1 - Method of determining influence of drilling mud on rocks - Google Patents

Abstract

The invention relates to a technique for testing materials, in particular, methods for determining the effect of drilling fluids on the destruction of rocks. The purpose of the invention is to improve accuracy and reduce labor intensity. Rock samples are alternately placed in a thermostatic chamber. Through the rod, which passes through the hole in the chamber lid, the sample is loaded with an axial compressive load, the magnitude of which is less than the dry load of the sample. Then the drilling fluid in contact with the side surface of the sample is poured into the chamber and a stopwatch is turned on to measure time. The time elapsed from the moment the drilling fluid is poured to the moment the sample is destroyed is recorded. Similarly, the time eV is determined when pouring distilled water into the chamber. The x-coefficient of rock resistance to this mud is determined by the ratio x - g / gV Comparing x found for different solutions , allows to assess the degree of their influence on rocks. 1 silt, 3 tab. cl

Description

The invention relates to a technique for testing materials, in particular, to methods for determining the effect of drilling fluids on the softening and destruction of rocks.

The purpose of the invention is to increase accuracy and reduce labor intensity.

The drawing shows a device for carrying out a method for determining the influence of drilling fluids on rocks.

The device contains a thermostated chamber 1 with a lid 2 for placing a rock sample 3, lining 4 for placing on the end surfaces of sample 3, a rod 5 mounted in the hole of the lid 2 for axial movement, a support 6 for cargo 7 fixed to the end rod 5; and funnel 8 for pouring drilling mud 9 or distilled water into the chamber.

The method is carried out as follows.

Cylindrical rock samples 3 are placed between two plates 4, placed at the bottom of the thermostatted chamber 1, the chamber 1 is covered with a cover 2 on top, the core 5 of which is inserted into the rod 5 with the stand 6 fixed on it. To ensure a central loading, sample 3 with overlays 4 is placed so that the bottom

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lining 4 stood in the recess at the bottom of the chamber 1, and the rod 5 fell exactly into the recess on the top lining 4. After that, on the stand. 6, a load 7 is set, the value of which is selected from 0.1 to 0.6 of the value of the critical load of destruction of sample 3 in a dry form. After thermostating of the chamber 1 with sample 3 in a separate vessel of drilling mud 9, the latter is poured through the funnel 8 in the upper lid 2 and the stopwatch is turned on to count the time.

Fixing the time from pouring the drilling fluid 9 into chamber 1 until the destruction of sample 3, determine the time Gy of destruction of sample 3 under load in the drilling fluid.

Similarly, for the same sample 3, the time Cv of destruction in distilled water is determined. The coefficient x of rock resistance to the effect of drilling fluids is determined by the ratio x tr / yy. Comparison of coefficients x. found for various drilling fluids, makes it possible to evaluate the properties of these fluids from the point of view of the stability of rocks in a given drilling fluid, and the more x, the better the stability of the tested rock in the borehole walls with respect to this series of drilling fluids.

In evaluating the effect of the mud on the rock, samples with the same properties, geometrical dimensions and with the same loads are used. Obtained under these conditions does not depend on the specified parameters, but depends only on the properties of the drilling fluid and its interaction with the rock.

The experimentally obtained values of the stability coefficient x, depending on the geometric dimensions of the sample in clays and the applied stresses to them (/ are given in Table 1.

Example. A specific feature of the geological section of the West Siberian region, which determines the choice of drilling mud formulations and the technology for regulating their properties, is the presence of thick clay deposits. Complications arising in the process of drilling in the form of debris, collapses, cavern formations, stickings are caused by the physicochemical processes of interaction of drilling fluids with rocks. Thus, drilling fluids are the main factor determining the stability of rocks in the borehole walls, changes in the reservoir properties of productive formations, which actively influence the process of rock destruction at the bottomhole. In connection with this

Of particular importance are studies aimed at emitting and disclosing the mechanism of the physicochemical effect on rocks of drilling fluids, which allow the development of methodological and scientific bases for predicting such compositions and properties of drilling fluids that would ensure the stability of rocks in the borehole walls, optimal conditions for their destruction on the bottomhole and preservation of reservoir properties of productive layers in the stalk zone.

For this purpose, samples 3 were pressed from clay with a diameter of 10 mm and kept for 10 days in a desiccator. Then the sample 3 was placed between the plates 4 in the chamber 1. On the stand 6, a weight 7 was installed weighing 10 kg. After thermostating of the chamber 1, distilled water was poured into it and a stopwatch was started. After the destruction of sample 3, the time was fixed. After the same preparatory operations were carried out with another sample 3, drilling fluid was poured into chamber 1 and the time of failure in the drilling fluid was determined. The factor x of rock resistance to the effect of this solution was determined by the ratio x Tr / Gu.

In tab. Table 2 shows the values of the stability coefficient x of samples of Nd - montmorillonite in aqueous solutions of electrolytes.

To develop a mud formulation with the use of simethyloxyethylene cellulose (CMCEC-T) boxes for its stabilization, tests were conducted to determine the stability coefficient x for samples of bentonite clays in a drilling mud (10 wt.% Clay) depending on the concentration (C) of CMOS-T. The results are shown in table 3. The density of the solution is p 1.06 g / cm, the time of destruction of the clay sample in distilled water, hw is 350 s.

As can be seen from the data table. 3, the largest value of x is the solution of 5 with C of 0.225. It is easy to see that this solution has an almost minimal water loss value of 9 cm3 and the greatest thixotropic properties of b / / 42/65 dPa.

Thus, the experiments performed made it possible to select the most optimal drilling fluid from the point of view of its effect on clay rocks without overruning the required amount of polymers used.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION Method for Determining the Effect of Drilling Fluids on Rocks, Including Loading of Rock Samples with Uniaxial Compression with Constant Load, Less Destructive Load of Sample in Dry Form, Supply of Drilling Fluid Samples to Side Surface distilled water, characterized in that, in order to increase accuracy and reducing labor intensity; the time from the moment of supplying the drilling fluid to the samples to the moment of their destruction is recorded, and the effect of drilling fluids is determined by the stability coefficient x from the ratio X Gy / Gu. where g, gv is the time of exposure of the samples to their destruction of the drilling mud and distilled water, respectively. Table 1 table 2 Table 3 t / iO zgi ZZZ32ss N & ySvf A / S WnjIfWftre J NEC-6 ii L / VVVV  & To / permuntu