SU1559115A1 - Plugging composition for isolating absorbing formations - Google Patents

Abstract

The invention relates to the drilling of wells. The goal is to improve the quality of the insulation by increasing the stability of cement stones and spills with flushing fluids. The solution contains the following ingredients in their ratio, wt.%: Calcium chloride 52.4-61.5, water-soluble metal sulfate 0.2-4.4, water - the rest. Sulfates of sodium, iron, copper, aluminum, zinc are used. The solution is prepared by successively injecting dry components into the water. The solution has a high penetrating ability, because does not contain solid phase. 1 tab.

Description

The invention relates to the drilling of oil, gas and exploration wells, namely, cementing compositions used to isolate absorbing horizons in low-temperature wells.

The purpose of the invention is to improve the quality of the insulation by increasing the resistance of the cement stone to washing out with washing liquids.

The cement slurry contains a highly concentrated aqueous solution of calcium chloride, in which an additive of water-soluble sulfate, for example Na, Fe, Cu, Al, Zn, is introduced, with a ratio of insulating mixture ingredients, wt.%:

Calcium chloride 52.4-61.5 Na, Cu, Fe, Al, Zn0.2-4.4 sulfate

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Depending on the amount of the additive, part of the calcium chloride reacts with the salt sulphate to form gkpsa and metal chloride salts, which when cooled to the crystallization temperature in the absorbing horizon form crystalline hydrates more resistant to diffusion of drilling fluids circulating in the well. Na, Fe, Cu, Al, Zn sulfates, the ionic radii of which are smaller than those of Ca, reduce the potential energy of the crystal lattice and, by providing

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maximum convergence of structural units, give a more dense packaging. f For experimental verification of the composition, mixtures of ingredients were prepared. The insulating mixtures are prepared in the following order: the metal sulfate salt, then calcium chloride (CaClj) is dissolved in water at a temperature of 15-20srp. When the latter dissolves due to the exothermic dissolution reaction, the temperature rises to 60-65 ° C. At study temperatures tap water of 1.5 mg-eKv dme and chemical reagents are used: anhydrous calcium chloride; iron (II) sulfate-7-water; copper (II) sulfuric acid 5-water; sodium sulfate; aluminum sulphate and zinc (II) 7-water sulphate.

The table shows the test results of cement slurries, which characterize their resistance to erosion.

Samples are cooled in a water bath with flowing water circulation at a temperature of 8-9 ° C for 2 hours. The temperature of the onset of mass crystallization is determined from the solution thermogram and is monitored visually. Crystal stones are washed out under running water

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water at a flow rate of 2 dme / mm, a temperature of 30 ° C, and a height of fall of the jet O, 1 m for 2 min.

The amount of metal sulfate is less than 0.2 wt.% Gives a nice output of cement stone. With an increase in the amount of sulphate of more than 4.4 wt.%, The cement slurry loses its mobility.

The use of the proposed tampon mortar allows high-quality insulation of thin-fractured formations due to deep penetration of the solution and the formation of a durable screen.

Claims (1)

Invention Formula Cement slurry for isolating absorbing layers, including calcium chloride and water, characterized in that, in order to improve the quality of the insulation by increasing the stability of the cement stone, washout with washing liquids, it additionally contains water-soluble metal sulfate in the following ratio, wt.% : Calcium chloride 52,4-6J, 5 Water soluble metal sulfate 0.2-4.4 WaterEverything 26 indicators of solubility and blurring Not pumpable Wake