RU2215868C2 - Well killing fluid - Google Patents

Abstract

FIELD: oil gas production, particularly, fluids for perforation and killing of wells. SUBSTANCE: killing fluid includes dispersion medium - solution of magnesium chloride diluted with water from formation to be treated, dispersed phase, reagents- filtration control agents in form of thickeners and surfactants. Magnesium chloride solution contains above 93% of MgCl₂. Chalk is used as dispersed phase. Thickener is used in form of polyacrylamide PRAESTOL 2530-2640. Surfactant is used in form of surfactant of complex action SNPH PKD-0515. Well killing fluid has the following amounts of components, wt.%: said magnesium chloride 8-30; chalk 0-10; said polyacrylamide 0.01-0.2; surfactant of complex action SNPH PKD-0515 0.04-3.0; the balance, said water. Well killing fluid may contain bishofite instead of said magnesium chloride. EFFECT: preserved reservoir properties of producing formations during their secondary tapping in performance of well overhauls and production maintenance and other geological and technical measures, increased efficiency of well completion. 2 cl, 1 tbl, 1 ex

Description

 The invention relates to the field of oil and gas production, in particular to fluids for perforating and killing wells.

 Known fluids for killing wells (GHS) based on mineral salts (produced water, produced water), sodium, magnesium, calcium chlorides, phosphate salts [Catalog of killing fluids. Krasnodar, 1989, p. 12-23, 42-46].

 Also known is a killing liquid, including lime, chloride salts of sodium, magnesium, aluminum, isopropyl alcohol production waste from the stage of crude alcohol sedimentation and rectification of the epureate, filtration reducing agents and water adopted by the authors for the prototype [RF Patent 2136854, publication date September 10, 1999].

 The main disadvantages of these kill fluids are the formation of insoluble sediments upon contact with formation water due to the presence of chloride salts of calcium and aluminum in the dispersion medium, which leads to clogging of the formation pores, as well as the relative complexity of preparation and poor foaming, depending on the quality of isopropyl alcohol production waste .

 The objective of the invention is the preservation of the reservoir properties of productive formations during their secondary opening during the period of overhaul and maintenance of wells and other geological and technical measures, increasing the efficiency of well development, expanding the raw material base of materials for preparing well killing fluids.

This object is achieved in that in a fluid for killing wells, which includes a dispersion medium — a solution of magnesium chloride diluted with formation water of an object for using a killing fluid, a dispersed phase, reagents — filtration reducers — thickeners and surfactants, according to the invention magnesium chloride solution contains more than 93% MgCl _2, as the dispersed phase using chalk as thickener - polyacrylamide PAA mark Praestol 2530-2640, as surfactant - surfactant complex of action - SNPCH PKD-0515, the following component ratio, wt.%:
The specified magnesium chloride is 8-30
Chalk - 0-10
Specified PAA - 0.01-0.2
Complex surfactant SNPK PKD-0515 - 0.01-3.0
Water - Else
moreover, as the specified solution of magnesium chloride, it contains mainly bischofite.

The essence of the invention lies in the fact that the killing fluid is prepared by mechanical mixing of the components. A solution of magnesium chloride containing MgCl ₂ > 93%, for example bischofite, is diluted with produced water of the well into which the kill fluid will be pumped. Bischofite is a natural salt, which contains mainly MgCl ₂ (more than 95%) and other salts. It is a clear, transparent, oily liquid, having a density at 20 ^{° C. of} 1.2-1.4 g / cm ³ . When mixing a kill fluid prepared on the basis of salts of magnesium chloride, mainly bischofite, with produced water of any degree of mineralization and ionic composition, the formation of insoluble sediments is absent. As for the corrosion indicators, according to the results of laboratory tests of a magnesium chloride sample with an MgCl ₂ content _of more than 99%, when the St.-3 brand plate contacts the magnesium chloride solution under room conditions, there is a slight exchange reaction between the metal of the plate and the magnesium chloride solution, which is expressed by a dissolution rate of 0.046 g / m ² hour, and a more intense exchange reaction at 115 ^o C - 1,64 g / m ² hour. The solution of magnesium chloride in the formation water of the object of application of the GHS is a dispersion medium. If necessary, to increase the density of the solution, the calculated amount of MgCl ₂ or K ₂ CO ₃ salts is added to it. The dispersed phase is CaCO ₃ chalk particles with a grinding fraction corresponding to the pore size of the formation rocks in the near-wellbore zone of the well, closed in formation water. For thickening, PAAESTOL grade PAA with an average anionic activity (2530-2640) and a molecular weight of 14-16 million is added to the mixture, and complex surfactants (SNPK PKD - 0515) are added as surfactants.

Complex surfactant - SNPK PKD-0515 - is a harmonious combination of a nonionic surfactant, a nitrogen-containing additive and a solvent. This liquid is light yellow to light brown in color, with a mass fraction of water of 0.5%, a freezing point of minus 30 to minus 40 ^o C and a flash point of 40 ^o C. The reagent is available in accordance with TU 39-05765670-OP-211- 95 (with amendments 1 and 2) of three grades A, B and H; Grades A and B - for drilling fluids; grade N - for fluids for killing, perforation, and conservation of wells.

 All components of the proposed composition of the ZhGS are dissolved or shut with formation water of the object in which the ZhGS will be used. With stirring, the mixture is brought to a homogeneous state and weighted to the required working density of the GHS.

 The invention is implemented as follows.

Example 1:
8 g of CaCO ₃ (chalk) are intensively stirred in the formation water of the object of application of the GHS. The resulting suspension is added to a bischofite solution, which is obtained by mixing 7.32 g of bischofite in produced water (the content of MgCl ₂ in bischofite is 95.7%). The mixture is thickened with PAA PRESTOL brand PAA with an average anionic activity of 2550, with a molecular weight of 14 million, adding it in an amount of 0.05 g. In addition, to reduce the surface tension, the surfactant SNPK PKD - 0515 in an amount of 0.5 is added to the mixture g. The amount of produced water in the obtained composition of ZhGS-84.13 g. The parameters of the obtained ZhGS and other options for producing ZhGS are given in the table.

The technical result of the proposed invention is the preservation of the reservoir properties of reservoirs during their second opening during the completion of major and ongoing repairs of wells and other geological and technical measures, as well as improving the efficiency of well development. In addition, the high content of magnesium chloride in the aqueous salt solution (more than 93%) allows the preparation of kill fluids with a density range of 1.02-1.30-1.35 g / cm ³ , which makes it possible to plug wells with high reservoir pressure and to temporarily isolation of the pores of the formation rocks. From the standpoint of achieving environmental rationality, the developed ZhGS formulation helps to increase the environmental cleanliness of the materials used in the overhaul and maintenance of wells and reduce the harmful effects on reservoir properties.

So, the use of the proposed formulation of ZhGS allows
- to improve the quality of jamming of productive wells with anomalous pressure 1.0-1.3 due to the weight of the formation water with magnesium chloride (mainly bischofite), which does not cause the formation of insoluble sediments in contact with the formation waters of any mineralization and composition;
- to increase the efficiency of development of productive wells after killing by reducing the volume of filtration of GHS in the reservoir to 8 cm ³ in 30 min, due to the introduction of a thickener - PAA medium anionic activity with high molecular weight and filler (chalk), if necessary, soluble in an acidic environment;
- to increase the efficiency of development of productive wells after killing by reducing the surface tension at the boundary of the GHS with the hydrocarbon medium (oil) to 6.2 μN / m and the swelling of clay minerals due to the introduction of surfactants of complex action.

Claims (1)

1. Well killing fluid, including dispersion medium - a solution of magnesium chloride diluted with produced water of the object used for killing fluid, a dispersed phase, reagents - filtration reducers - thickeners and surfactants surfactants, characterized in that the magnesium chloride solution contains more than 93% MgCI ₂ , chalk is used as a dispersed phase, PAA grade PRAESTOL 2530-2640 polyacrylamide is used as a thickener, and complex complex surfactant SNPK PKD-0515 is used as a surfactant in the following ratio components, wt. %:
The specified magnesium chloride is 8-30
Chalk - 0-10
Specified PAA - 0.01-0.2
Complex surfactant SNPK PKD-0515 - 0.01-3.0
Indicated Water - Else
2. The liquid according to claim 1, characterized in that it contains bischofite as the specified solution of magnesium chloride.

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