Electrochemical activation: first invention

A method to treat drilling fluid.

USSR Certificate of Authorship No. 929682, 1974.

U.D. Mamadzhanov, V.M. Bakhir, V.N. Shamsutdinnova, T.M. Bakhir

The priority of this invention in accordance with Claim # 2018444 was established on April 22, 1974 . By that time, a two-year period of investigations and industrial tests of electrochemical methods and devices to condition drilling fluids had been over, which became the basis for electrochemical activation technology. The above investigations had been performed from 1972 in Central Asian Research Institute of Natural Gas (SredAzNIIGas). A drilling fluid is a complex polydisperse system containing clayey mineral particles in water with added organic substances - stabilizers, structure formers, thinning and filtration agents.

The main technological function of a drilling fluid is bringing drill cuttings from the well bottom to the surface. Clayey particles found in drilling fluid are normally negatively charged, the charge density depending on surface configuration and chemical composition of clayey particle crystal lattice, as well as on chemical composition and electrolyte content of the liquid phase of drilling fluid. Passing current through drilling fluid commonly results in deposition on the anode of firm clayey crust made up of the most fine-disperse and highly-charged clayey particles. This crust prevents products of anode electrochemical reactions from entering the drilling fluid, therefore the solution's рН value increases due to cathode, unipolar in fact, electrochemical treatment. It was found that in conditions of the same expended quantity of specific power, the smaller cathode area in comparison with anode one, the stronger thixotropic properties of drilling fluid (structural-mechanic strength) and simultaneously lower its dynamic viscosity (paradox). The paradox can be explained as follows: the electric charges accumulated on the edges and pointed parts of tiny scales or needle-like particles of argillaceous minerals are several times stronger than the charges on their flat facets.

Under the influence of electrochemical treatment, in a high voltage electric field close to the cathode surface (in the area of spatial charge), there increased absolute value of particles' negative charge, thus enhancing their repulsion forces and therefore lowering viscosity. At the same time, the difference between the potentials of the edges and facets of argillaceous particles also rose, causing growth of forces putting in good order structural arrangement of interacting clayey particles. So, the drilling fluid structural and mechanic properties improved due not to mechanic, but to electrostatic cohesion of clayey particles. Studying the phenomenon in question both in laboratory, and under real life drilling conditions made it possible to understand the specific nature of the processes observed, that is, nonequivalence of electrochemical and chemical regulation methods, and start attempting to practically apply the discovered effect in the process of oil and gas borehole drilling.

The reported effect had not been known before, which is why the process of unipolar cathode electrochemical treatment of drilling fluid was firstly called by V. M. Bakhir “ low-voltage polarization”, and three years later “ electrochemical activation” . The above-indicated first invention established a way to improve drilling fluid parameters using no chemicals, i. e. by treatment in an engineering electrochemical system consisting of a current source and two electrodes, the cathode surface area being smaller than the anode one.

In this electrochemical system, the surfaces of drilling device circulation system coming into contact with drilling fluid actually performed the function of anode.

Practical experiments proved the method's high efficiency, which allowed saving up to 30 % of chemicals commonly used in borehole drilling. However, the method had a significant disadvantage, that is the necessity to periodically remove clayey crust from the anodic surface and the laboriousness of the procedure.

The numerous further inventions of 1974 – 1976 were aimed at further perfecting and improving the discovered method of drilling fluid parameters control, and technical systems for its implementation. Appliances developed in that period were fitted with electrochemical reactors having flat electrodes (steel cathodes, loadstone or graphite anodes) with considerable surface area of a single electrode (from 0,2 to 0,7 m 2 ) intended for high-tension currents (600 - 1500 А ) to treat large bulks of drilling fluids (20 – 90 liters per second). Monitoring the operation of the devices' experimental models under conditions of drilling deep oil and gas boreholes indicated that the larger the fluid surface coming directly into contact with the surface of working (negative) electrode, the higher the degree of drilling fluid alterations observed after electrochemical treatment. Inter-electrode space of the devices for unipolar (cathodic) electrochemical treatment was not partitioned by a diaphragm. In all modifications of devices developed to implement the effect of unipolar electrochemical exposure, positive electrode with dense clayey crust deposited on it was safely protected by the latter from direct contact with the main bulk of drilling fluid. The products of anode electrochemical reactions did not enter drilling fluid as they accumulated in argillaceous solution crust whose thickness generally ranged between 2 and 3 cm.