RU2112780C1 - Low-silicate drilling mud - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: drilling mud contains, wt.-%: clay, 7-9; liquid glass, 2-5; polyacrylamide, 0.1-0.2; a hydrophobic colmatant, which, according to invention, is colophony-bitumen reagent, 0.5-2.0; and water, the balance. EFFECT: increased mudding properties of mud with simultaneously reduced content of liquid glass and polyacrylamide. 2 cl, 1 tbl

Description

 The invention relates to the drilling of oil and gas wells, in particular to low silicate flushing fluids used in the drilling process.

 Little silicate flushing liquids are known that are used during drilling in the intervals composed of loose unstable clayey rocks [1]. These drilling fluids have a low inhibitory ability and require additional treatment with chemicals to improve filtration and structural-mechanical parameters.

 Closest to the proposed invention is a drilling fluid for drilling wells in flowing rocks [2] containing clay in wt.%: 5 - 7, sodium silicate 5 - 7, polyacrylamide 0.3 - 0.5 and GKZH-94 0.5 - 1.5.

 The disadvantage of this solution, taken as a prototype, is the ability to inhibit only the near-wellbore zone. As the radius of penetration of the filtrate into the reservoir increases, its inhibitory properties are lost.

 The objective of the invention is to increase the fastening properties of low-silicate drilling fluid while reducing the content of water glass and polyacrylamide.

The problem is solved in that in a low-silicate drilling fluid containing bentonite clay, water glass, polyacrylamide and water, hydrophobic colmatant is additionally introduced in the following ratio of components, wt.%:
Bentonite clay - 7 - 9
Liquid glass - 2 - 5
Polyacrylamide - 0.1 - 0.2
Hydrophobic colmatant - 0.5 - 2.0
Water - Else
Malosilicate drilling fluid according to claim 1, characterized in that it contains a rosin-bitumen reagent as a hydrophobic colmatant.

 The role of a hydrophobic colmatant can be performed by any substance capable of hydrophobizing the surface of clay particles and at the same time clogging the pore channels and microcracks along which penetration of the mud filtrate into the formation occurs. The result of the combined effect of hydrophobic colmatant on swell-prone unstable rocks is a decrease in the hydration of clay particles and a decrease in the radius of penetration of the aqueous phase into the interpack space of minerals. Ultimately, the likelihood of complications of deformation nature and softening of the walls of the well is reduced.

 An example of a hydrophobic colmatant is a rosin-bitumen reagent (CBD), which is a mixture of rosin-extraction polymers of CEC and a bitumen structure-forming agent (bitumen).

 Rosin-extraction polymers (TU 81-05-39-79) are a product of forest processing and are a complex mixture of hydrocarbons, including terpenes, diterpenoids, fatty and resin acids, etc.

 Many of the chemicals that make up CEP are water repellents. When powdered bitumen is dissolved in rosin-extraction polymers, a system is formed that can hydrophobize clay particles and clog pore channels and microcracks behind bitumen particles.

 When preparing the CBD in 95 parts by weight CEP is placed 5 wt.h. powdered bitumen, the mixture is stirred and left for a day, periodically repeating mixing. After 24 hours, CBD is used to treat low silicate drilling mud.

 The presence of a rosin-bitumen reagent in a low-silicate drilling fluid with a simultaneous decrease in liquid glass from 5 to 7 wt.% To 2 to 5 wt.% And polyacrylamide from 0.3 to 0.5 wt.% To 0.1 to 0.2 wt. .% is a hallmark of the claimed invention.

 The invention meets the criterion of "Inventive step", since the above combination of hydrophobic inhibitors with hydrophobic colmatant in the given ratios in low silicate drilling fluid is not obvious to the average person skilled in the art.

 The above characteristics allow us to consider the claimed composition of low-silicate drilling fluid new, not described in the scientific, technical and patent literature.

 The invention is industrially applicable, as evidenced by the attached laboratory test report.

 A drilling fluid of the claimed composition was prepared using the following reagents: a clay suspension based on Ilsky bentonite concentration of 7 to 9 wt. %; water glass, TU 6-15-433-75; dry polyacrylamide, TU 16-2531-81; rosin-extraction polymers, TU 81-05-39-79; bituminous builder, TU 38-Ukrainian SSR, 20-184-84.

 The inhibitory properties of the drilling fluid (T - L effectiveness of the claimed technical solution) was evaluated by the swelling index - the amount of liquid phase that absorbs a sample of clay placed in the medium of the studied drilling fluid.

 The test was carried out on samples of clay sludge with wells. 6101 Bovanenkovo field. The pre-ground sludge was sieved through a 0.25 mm sieve and moistened to 20% moisture. A sample weighing 5 g was taken from the obtained fraction, placed in a mold, and a tablet sample was pressed at a pressure of 40 MPa. After weighing, the sample was placed in the test drilling fluid, kept for 4 hours, removed and weighed again. The amount of moisture (in wt.%) Absorbed by the rock per 1 g of the initial fraction was calculated by the difference in weights before and after the experiment according to the results of three parallel changes.

 The results of the tests showed that the presence in the silicate mud only of hydrophobizing inhibitors - water glass and GUZh-94 (according to the prototype) does not provide a significant inhibitory effect. The moisture content of clay samples in the medium of such a solution is from 4.64 wt.% (See table, opt. N 2) (in a bentonite solution without chemical treatment this value is 9.78 wt.%, See table, op. N 1).

 After the introduction of a hydrophobic colmatant, in particular, rosin-bitumen reagent (CBD), into the composition of the drilling fluid, the inhibitory qualities of the solution deepen while reducing the content of water glass and polyacrylamide (see table).

 A decrease in the moisture content of clay samples by 50-60% compared with the prototype was noted in the low-silicate clay solution of the following composition in wt. %: clay 7 - 9, water glass 2 - 5, polyacrylamide 0.1 - 0.2, hydrophobic colmatant (in particular, rosin-bitumen reagent) 0.5 - 2.0, water - the rest (see table, Op. N 3 - 8).

 Changing the ingredients in a solution qualitatively affects its characteristics.

 So, the maximum efficiency of the rosin-bitumen reagent as a hydrophobic colmatant is achieved when it is contained in the solution in an amount of 0.2 - 2.0 wt.%. When the CBD content is below 0.5 wt.%, The processing efficiency decreases (see table, op. N 9), increasing its concentration of more than 2 wt.% Slightly increases the inhibitory effect and is not economically feasible (see tab., Op. N 7 )

 With an increase in the content of water glass more than 5 wt.%, The solution thickens and the pH increases (see table, op. N 8), with a decrease in the amount of this reagent below 2 wt.%, The inhibitory properties of the low-silicate solution deteriorate (see table, op . N 10).

 When the content of polyacrylamide is less than 0.1 wt.%, The filtration of the solution increases and its fastening properties deteriorate (see table, op. N 11), an increase in the content of this reagent above 0.3 wt.% Causes an increase in viscosity (see table, Op. N 12).

Example 1
A clay suspension is prepared with a clay content in water of 7 wt.%, Mixed for 30 minutes. In the resulting solution, liquid glass is sequentially added in an amount of 5 wt.%, Polyacrylamide in an amount of 0.2 wt.%, Rosin-bitumen reagent in an amount of 2 wt.%. After the introduction of each reagent, the solution is stirred for 15 minutes.

Example 2
A clay suspension is prepared with a clay content of 8 wt.% In water, mixed for 30 minutes. After this, the solution is sequentially introduced: liquid glass in an amount of 3 wt.%, Polyacrylamide in an amount of 0.15 wt. %, hydrophobic colmatant (rosin-bitumen reagent) in an amount of 1 wt.%, after adding each reagent, the solution is mixed for 15 minutes

Example 3
A clay suspension is prepared with a clay content in water of 9 wt.%, Mixed for 30 minutes. After that, the solution is sequentially added: liquid glass in an amount of 3 wt.%, Polyacrylamide in an amount of 0.15 wt.% Hydrophobic colmatant (rosin-bitumen reagent) in an amount of 1 wt.%, After adding each reagent, the solution is mixed for 15 minutes .

Example 3
A clay suspension is prepared with a clay content in water of 9 wt.%, Mixed for 30 minutes. After this, the solution is sequentially added: liquid glass in an amount of 2 wt.%, Polyacrylamide in an amount of 0.1 wt.%, Hydrophobic colmatant (rosin-bitumen reagent) in an amount of 0.5 wt.%. After adding each reagent, the solution is stirred for 15 minutes.

 The use of low-silicate drilling fluid of the claimed composition in wells. 10 areas of Belaya (Severgazprom enterprise) allowed to ensure long-term stability of the Nizhne-Famennian-Verkhnefran breeds, to prevent sticking of the drilling tool in the well, to improve the performance of the bits, to reduce the time spent on drilling.

Claims (1)

1. Malosilicate drilling fluid containing clay, water glass, water and polyacrylamide, characterized in that it further comprises a hydrophobic colmatant in the following ratio of components, wt.%:
Clay - 7 - 9
Liquid glass - 2 - 5
Polyacrylamide - 0.1 - 0.2
Hydrophobic colmatant - 0.5 - 2.0
Water - Else
2. The drilling fluid according to claim 1, characterized in that the rosin-bitumen reagent is used as a hydrophobic colmatant.

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