Chemical technology expertise

The SCL Test Center has its own chemical laboratory to conduct chemical engineering research. This division of the test center conducts a wide range of studies related to determining the quality of downhole equipment and expertise of the materials and environments in which the equipment operates. Most tests performed in the laboratory require additional chemical and technological expertise of materials, composition and properties of working fluids, technological schemes of test preparation. The most important activities of the chemical division are:

Study of formation sand properties, including analysis of sand Particle Size Distribution (PSD)
Determination of the properties of the working fluids used in the tests, including dynamic and kinematic viscosity, density. Study of colmatation properties of sand screens.
Expertise for corrosion resistance of materials and their compounds in downhole equipment.
Selection of colmatant for hydraulic collapse/tensile testing.
Development of gel-formation technologies from polymeric structures for applied problems of sand control.

PSD analysis

PSD analysis is performed to determine the particle size distribution curves of the mass distribution of sand particles, the nature of homogeneity and sorting of this distribution. The analysis is performed using the sieve method on the basis of core samples from the customer. The PSD analysis can be broken down into the following operations:

Weighing the original core sample.
Crushing the original sample manually
Drying of core sample particles in a thermal desiccator at 110⁰C
Re-weighing the sample after drying
Filling the sample into the sieve analyzer and sifting
Weighing the sand on each sieve
Construction of particle size distribution curves of sand mass size distribution.

The set of sieves consists of 15 sieves with sizes from 1000 microns to 40 microns. The sieve analyzer is a vertically stacked sieve with a vibration drive at the bottom of the analyzer.

Sieve analyzer VP-30T

The set of sieves consists of 15 sieves with sizes from 1000 microns to 40 microns. The sieve analyzer is a vertically stacked sieve with a vibration drive at the bottom of the analyzer.

Sample elements remaining on the sieve

After sifting the sand on each sieve there is a small portion of sand, which is weighed on a laboratory scale.

Cumulative distribution of the mass fraction of particles as a function of size in μm

After processing the data obtained, a particle size distribution of the mass fraction of particles depending on their size is constructed. A logarithmic scale by size is used.

Qualitative analysis of the distribution is based on the parameters d₁₀, d₄₀, d₅₀, d₉₀, where the parameter d_xx determines the minimum particle size of the 10% largest particles. These parameters are widely used in the task of selecting the optimal screen slot clearance to minimize sanding.

Colmatant selection

To conduct the tensile tests, it is necessary to develop a formulation of a colmatizing liquid with which to stick the surface of the screen. The sticking effect is used to create hydraulic pressure on the screen wire winding to determine the strength of the screen structure. Colmatant selection is carried out on a special laboratory unit to determine colmatation.

The laboratory unit is a hydraulic cylinder with a wire screen sample fixed in its lower part. The screen is made by winding the profile wire on the base tube with guides laid on it so that the clearance between the coils is 304.8 μm. The laboratory apparatus is designed for pumping through a sample of a colmatated composition with obtaining a fluid pressure – piston displacement diagram. A mechanical press with a constant traverse speed is used to press through the composition.

Laboratory colmatant selection unit

Characteristics of the laboratory unit:

Volume of colmatant – 0.5 L;
Sample diameter – 30-63.2 mm;
Piston stroke – 176 mm;
Cylinder diameter – 60 mm;
Maximum pressure – 350 atm.

Typical graph of pressure versus time on a laboratory unit

The colmatant formulation for the preparation of fluid loss control is based on the basic formulation of API Specification 19SS, Sand Screens. The formulation is based on calcium carbide (CaCO3) milled into three fractions according to the size of the particles in relation to the slot clearance. Technical water, polymer and biocide are added to calcium carbide.

After stirring, the solution is poured under the piston into the laboratory unit. With the mechanical press, the piston presses the solution in the cylinder through the screen, resulting in gradual clogging of the screen slots, which leads to an increase in resistance to flow and an increase in pressure in the inlet connection of the screen chamber. The pressure-time diagram is the direct result of the test. The purpose of the colmatant formulation is to achieve maximum pressure until the colmatant crust on the screen coupon is broken down sufficiently for the collapse/tensile testing.