RU2385892C1 - Stabilisation method of salt-saturated drilling mud - Google Patents

Abstract

FIELD: oil-and-gas production.

SUBSTANCE: in stabilisation method of salt-saturated drilling mud including treatment of mentioned mud by modified starch in the capacity of modified starch it is used dextrin and Phyto-PK, at following ratio of ingredients, wt % to object of drilling mud: dextrine 1.7-2.0; Phyto-PK 1.3-1.5.

EFFECT: conditioning of salt-saturated drilling mud ensured by reduction of foaming ability and increasing of stability in time.

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Description

The invention relates to the oil and gas industry, in particular to drilling fluids for drilling oil and gas wells.

It is known that one of the methods for stabilizing a saline-saturated drilling fluid is its joint treatment with polymer reagents, one of which is modified starch (MK), and carboxymethyl cellulose (CMC), hydrolyzed polyacrylonitrile (hypane), and K- reagent can be used as the second polymer reagent. 4, sulfite-alcohol stillage (PRS) or condensed sulfite-alcohol distillery stillage (KSSB) [1, 2].

The stability of the drilling fluid is estimated by changing the value of the filtration rate over time. An increase in the filtration value after a certain time means a decrease in the stability of the drilling fluid.

Closest to the proposed solution is a method of joint processing of a drilling fluid with polymer reagents: modified starch and sulfite-alcohol bard (SSB) [1]. The disadvantages of this method compared with the proposed solution are the increased foaming ability, characterized by the value of the coefficient of foaming, and the low stability of the drilling fluid over time.

The objective of the invention is to improve the quality of salt-saturated drilling fluids by reducing foaming ability and increasing stability over time.

The problem is achieved in that in the method of stabilizing a saline-saturated drilling fluid, comprising treating said solution with modified starch, according to the invention, dextrin and Fito-RK are used as modified starch, with the following ratio of ingredients, wt.% To the volume of drilling mud:

dextrin 1.7 - 2.0 Fito-RK 1.3-1.5

Dextrin is a carbohydrate (C ₁₂ H ₂₀ O ₁₀ ) obtained from starch by heating to 210 °, the action of weak acids or the enzyme diastasis.

Phyto-RK is a starch reagent designed for drilling oil and gas wells, is a modified starch: white powder with a mass fraction of moisture of 4.0% and a solubility of 99.8%. It is produced by SPK Spetsburtehnologiya LLC in accordance with TU 10 of the Russian Federation 1039-92 (Moscow).

The starch granule consists of branched polysaccharide amylopectin molecules and linear amylose molecules. The degradation of starch reagent and the loss of ability to reduce mud filtration occurs due to retrograde caused by the association of amylose molecules. To increase the stabilizing ability of Phyto-RK, it was necessary to select a reagent with a lower molecular weight, capable of creating spherical obstacles for the convergence of linear amylose molecules.

An important difference between Dextrin and Phyto-RK is its best solubility in water, on which its action as a link is based. In addition, dextrin has an emulsifying ability.

Laboratory studies were carried out on a saline palygorskite clay solution of 8% concentration. Reagents were introduced into the solution in marketable form.

We give examples of the implementation of the method of stabilization of saline drilling fluid in the laboratory.

Example 1

To prepare the clay solution, 920 cm ³ of drinking water is poured into a glass and pour (80 ± 0.5) g of clay powder. The contents are mixed with a mixer or mixer with a speed of at least 3000 per minute for 20-30 minutes.

A solution of clay powder in water is left to swell for 24 hours, then stirred with a mixer or stirrer with a speed of at least 3000 per minute for 20 minutes. Thus, a fresh clay solution is obtained.

To obtain a salt-saturated clay solution, (300 ± 1) g of edible salt is introduced into the fresh solution and stirring is continued for 30-40 minutes until it is completely dissolved.

Since the viscosity of the solution increases after salinization, it must be diluted with brine to a nominal viscosity of 25-30 s.

To stabilize the prepared solution, treatment with stabilizing reagents is carried out. With 500 ml of a saturated clay solution, 8.5 g (1.7 wt.% By volume of the solution) of dextrin and 6.5 g (1.3 wt.% By volume of the solution) Phyto-RK are gradually introduced with constant stirring. The solution is mixed for 30-40 minutes.

Example 2

Salt-saturated clay solution is prepared as in example 1.

To 500 ml of the prepared solution, with constant stirring, 10 g (2 wt.% By volume of the solution) of dextrin and 7.5 g (1.5 wt.% By volume of the solution) Phyto-RK are gradually introduced. The solution is mixed for 30-40 minutes.

The table shows the parameters of salt-saturated drilling fluids treated with polymer reagents.

Experience number Solution composition Main settings Density, ρ, g / cm ³ Viscosity, T, s Filtration, F, ^cm3 / 30 min Filtration, F, cm ^3/30 min, (t + 80 ° C, 2 hours) Filtration, F, cm ^3/30 min, 2 days Filtration, F, cm ^3/30 min, 10 days SNA mgs / cm ² Kvsp. one 2 3 four 5 6 7 8 9 10 one 8% salted polygorskite clay solution 1.24 25 84 ~ - - 12/17 - 2 Solution No. 1 + 5 wt.% PRS + 1.5 wt.% MK (prototype) 1.24 57 6 fifteen 10 22 17/28 1,60 3 Solution No. 1 + 2 wt.% Dextrin 1.24 25 70 - - - 12/19 - four Solution No. 1 + 1.5 wt.% Phyto-RK 1.24 110 6 - 17 - 35/43 - 5 Solution No. 1 + 1.5 wt.% Dextrin + 1.1 wt.% Phyto-RK 1.24 80 8.6 - 9 fifteen 27/38 1.35 6 Solution No. 1 + 1.7 wt.% Dextrin + 1.3 wt.% Phyto-RK (proposed option) 1.24 55 5 6.5 5.5 6 25/34 1.40

Table continuation

one 2 3 four 5 6 7 8 9 10 7 Solution No. 1 + 2 wt.% Dextrin + 1.5 wt.%
Fito-RK (proposed option) 1.24 60 5 6 5 5.5 12/20 1.40 8 Solution No. 1 + 2.5 wt.% Dextrin + 1.9 wt.% Phyto-RK 1.24 98 3.2 - 3.2 3,5 30/39 1.45

In experiments No. 3 and 4, the values of the parameters of the solutions treated with one of the reagents are given. As you can see, the processing of clay mud with one dextrin does not lead to a decrease in mud filtration. And the use of Phyto-RK alone does not stabilize the filtration of the solution over time.

As can be seen from the table, during the joint processing of a saline clay solution with dextrin and Fito-RK, the filtration values are at the same level (experiments No. 6, 7). This suggests that dextrin “protects” Phyto-RK from degradation (ie, supports its ability to reduce the filtration of saline saturated mud over time), due to which the filtration does not increase for 10 days. In contrast, when the salt-saturated drilling fluid is treated together with modified starch and CSP, after 10 days, the filtration of the solution increases to 22 cm ³ in 30 minutes (experiment 2).

The feasibility of treating saline drilling mud with dextrin and Phyto-RK is confirmed in terms of filtering the fluids after holding them for two hours at a temperature of 80 ° C in an OFITE roller mill (experiments No. 6, 7). Using the PRS, such a result was not obtained (experiment 2).

In addition, the value of the coefficient of foaming of a salt-saturated clay solution during the treatment with SSB and MK is higher (1.60) than with dextrin and Fito-RK (1.35-1.40).

The lower limit of the amount of dextrin (1.7 wt.%) Is limited by the rate of filtration after 10 days of the drilling fluid treated with Fito-RK; upper (2 wt.%) - economic inexpediency. Phyto-RK is proposed to be used in an amount of 1.3-1.5 wt.% To the volume of the drilling fluid, because this amount is enough to reduce the filtering value. An increase in the input of this reagent will increase the viscosity of the solution, and a decrease will increase the filtration of the solution.

The results of laboratory studies were confirmed by a decrease in the number of treatments of Fito-RK drilling mud during the drilling of saline deposits in wells. No. 287 of the Rechitsa oil field of RUE “Production Association Belorusneft”, where dextrin was first tested as the second polymer reagent instead of the used PRS.

The test was initiated in the wellbore after lowering to 245 mm technical column to a depth of 1040 m and salinization of the solution when its parameters were as follows: density 1.24 g / cm ^3, a viscosity of 39 s, filtering 8 cm ^3/30 min, 17 SNA / 25 mg / cm ² , the density of the filtrate is 1.20 g / cm ² . The solution was treated with dextrin and Fito-RK at the same time.

After the treating solution has acquired the following parameters: density 1.25 g / cm ^3, a viscosity of 45 s, filtration 3 cm ^3/30 min, SNA 30/45 mgf / cm ^2.

By increasing the index filtration of the solution to 7 cm ^3/30 min secondary treatment was carried out at slaughter 1145 m, then filtering the solution decreased to 4.5 cm ^3/30 min at constant rates other basic parameters.

Further processing of the solution with these polymer reagents according to the proposed technology also did not adversely affect the performance of the solution in the well. Considering the results obtained, it was recommended to continue the test when drilling saline rocks in other oil fields.

Thus, the method of stabilizing a saline-saturated drilling fluid, including treating the specified solution with modified starch, which was used as a mixture of dextrin and Fito-RK, allowed to reduce the consumption of antifoam and Fito-RK by lowering the foaming ability and increasing the stability of the drilling fluid.

Information sources

1. Ryazanov Ya.A. Encyclopedia of drilling fluids. - Orenburg: publishing house "Chronicle", 2005. - P.225,239.

2. Gorodnov V.D. Drilling fluids. - M .: "Nedra", 1985. - P.83.

Claims (1)

A method of stabilizing a salt-saturated drilling fluid, comprising treating said solution with modified starch, characterized in that dextrin and Phyto-RK are used as modified starch in the following ratio of ingredients, wt.% To the volume of drilling mud:
dextrin 1.7-2.0 Fito-RK 1.3-1.5