RU2099504C1 - Ekogum powdery mixture for preparation of displacement fluid and muds treatment - Google Patents

Abstract

FIELD: drilling and casing of oil and gas wells. SUBSTANCE: EKOGUM powdery mixture contains, mas%: coal-alkali reagent, 30-50; EKOTEX reagent, 50-70. The latter is based on copolymer of vinyl acetate and polysaccharide. EFFECT: higher efficiency. 3 tbl

Description

 The invention relates to the field of drilling and fastening of oil and gas wells, in particular to drilling fluids with low filtrate recovery and rheological parameters.

 For high-quality cementing of the well, it is necessary to prepare its wellbore, clean from the remnants of the drilling fluid and completely replace the drilling fluid with grouting. For this purpose, various buffer fluids are used.

 Known buffer liquid [1] on an aqueous basis containing mineral salt and an alkaline additive. The specified buffer fluid cannot be used for the separation of weighted grouting and drilling fluids due to the risk of weight loss and the formation of non-pumpable plugs.

Closest to the claimed object is a powder mixture for the preparation of a buffer liquid, including lignin, carboxymethyl cellulose, an alkaline reagent and waste oil and fat production [2]
The disadvantage of this mixture is that the resulting buffer fluid degrades the reservoir properties of the reservoir due to high rates of filtration and rheological parameters of the reservoir.

 The purpose of the invention is to obtain a buffer fluid that preserves the reservoir properties of the formation and reduce filtering and rheological parameters of clay drilling fluids.

 This goal is achieved by the fact that in a powder mixture containing water-soluble humates and high molecular weight substances of the polysaccharide class, characterized in that it contains carbon-alkaline reagent (UCHR) as highly soluble humates, and Ecotech polysaccharides are used as compounds in the following ratios of components (wt. .) USCHR 30-50, Ecotech 50-70.

 Ecotech is a white, powdery, readily soluble copolymer of polyvinyl acetate and polysaccharide. Ecotech is produced at the Nevinnomyssk PO Azot according to TU 89-73-06-33-91.

 The technical effect is achieved due to the fact that the copolymer of vinyl acetate and polysaccharide, passing through the highly permeable interval of the well, colmatizes its pore space, thereby reducing the filtration of solutions.

 However, because of its significant molecular weight, the polymer does not penetrate into the pores, settling on the rock of the reservoir, as a result of which it is easily washed out by oil during well completion after completion of work.

 In the table. 1.2, data are presented illustrating the properties of the buffer fluid and its effect on grouting and drilling fluids at different temperatures.

Based on the experimental data given in table. 1, it is seen that the buffer liquid based on "Ecohum" does not accelerate the thickening time of cement mortars in the temperature range up to 150 ^o C.

 Laboratory tests to determine coagulation phenomena when mixed with a variety of drilling fluids and buffer fluid showed that coagulation thickening was not observed in all experiments, -cm. tab. 2.

The concentration of the buffer liquid suspension ranges from 5-8%
The quality of the buffer fluid was evaluated by filter recovery, permeability recovery coefficient, and viscosity of the mixtures formed by the buffer fluid with drilling cement slurries. The nominal viscosity was determined by SPV-5, the plastic viscosity of the buffer fluid, drilling fluid and their mixtures was determined at different temperatures using a VBN-3 vibrating viscometer, and the thickening time of grouting mortars and their mixtures with buffer fluid using a KC-3 consistometer.

 Example 1 (experiments 3, 4, table. 3).

Take 30 g of UShR and 70 g of Ecotech, mix thoroughly. 80 g are taken from the prepared mixture and dissolved in 920 cm ^{3 of} tap water. After thorough mixing and dissolution of the reagent, conditional viscosity, fluid loss of the buffer fluid, and permeability recovery coefficient are measured. The values of these indicators 34 ^o C, 11,0 cm ^3/30 min and 71.8% respectively. Then, the buffer liquid is mixed in a ratio of 1: 9 with the cement slurry and the thickening time of the mixture is determined at KC-3. For ratios 1: 3 and 1: 1, these indicators are not determined, because there is a strong dilution of the mixture, which does not cause acceleration of setting.

 Example 2 (experiments 5.6, table. 3).

Take 40 g of UShR and 60 g of Ecotech. After thorough mixing, the prepared mixture in an amount of 80 g is dissolved in 920 g of water and the conditional viscosity, water yield and permeability recovery coefficient are determined. The indicators of the prepared buffer fluid are as follows: conditional viscosity 25 s; water loss of 13.0 cm ^3/30 min; formation permeability recovery coefficient of 60.0%
Example 3 (experiments 8.9, table. 3).

Take 50 g of UShR and 50 g of Ecotech, mix thoroughly, take 80 g of the mixture and dissolve in 920 cm ^{3 of} water. After dissolution determined conditional viscosity, fluid loss and buffer liquid whose figures 23 ^o C, 15,0 cm ^3/30 min and 63%, respectively.

 Example 4 (experiment 10, 11, table. 3).

Take 60 g of UShR and 40 g of Ecotech. 80 g of the prepared mixture are dissolved in 920 g of water and the nominal viscosity, filtration and permeability recovery coefficient are determined. These indicators for preparing spacer fluid follows: 19 to 25.3 cm ^3/30 min and 45.4% respectively.

 Example 5 (experiments 12, 13, table. 3).

Take 80 grams Prototype mixture is dissolved in 920 cm ³ of water and after dissolving the obtained parameters define buffer liquid, are equal respectively to 22 relative viscosity, water loss of 32 cm ^3/30 min, the permeability recovery ratio 37.6%
The influence of ecohum on the properties of the drilling fluid was evaluated by conditional viscosity, thermal heating, filtrate recovery, static (CHC) and dynamic (τ _o ) shear stress, plastic viscosity and pH of the solution.

 For this, a clay suspension of 7.0% concentration was prepared, a certain amount of ecogum was introduced into it, and the above parameters were determined.

 In the table. 3 shows the data characterizing the effect of the powder mixture on the properties of the drilling fluid. From the table it follows that the powder mixture reduces the filtration of drilling fluids even during thermal exposure, and the prototype, slightly reducing the filtration of the drilling fluid, significantly increases its viscosity. Buffer fluid based on Ecoguma has a high recovery coefficient of formation permeability, and is indifferent to grouting and drilling fluid treatments.

Drilling fluid based on "Ecoguma" has a reduced (2-3 times) indicators of filtrate recovery, static shear stress (CHC) by 1.5 2.0 times, dynamic shear stress (τ _o ) and plastic viscosity by 2-3 times, which provides high technological properties of clay drilling fluids.

Claims (1)

 A powder mixture for preparing a buffer fluid and processing drilling mud containing a high molecular weight compound of the polysaccharide class and an alkaline reagent, characterized in that as a high molecular weight compound of the class of polysaccharides it contains a reagent based on a copolymer of vinyl acetate and polysaccharide, and as an alkaline reagent, a carbon-alkaline reagent in the following ratio of starting ingredients, wt. Reagent based on a copolymer of vinyl acetate and polysaccharide 50 70
Carbon-alkaline reagent 30 50ш

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