RU2419714C1 - Procedure for insulation of water production in well - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: procedure for insulation of water production in well consists in successive pumping sodium silicate and 5-15% solution of fluorosilicate ammonia in equal volumes through a buffer of fresh water into a required interval of insulation.

EFFECT: raised processability and efficiency of repair-insulation operations; reduced volume of associated produced water.

2 tbl, 1 ex

Description

The invention relates to the oil and gas industry, in particular to methods for isolating water inflow in a well.

A known method of preparing cement slurry, which is used to limit water inflow (US Pat. RF 2270328, E21B 33/138, publ. 02.20.2006, Bull. No. 5). The grouting mortar contains sodium silicate (water glass) with a silicate module of 3.5-5.0, and formamide as an organic hardener in the following ratio of components, parts by weight:

modified liquid glass one hundred water 10-25 formamide 10-25

or use ethyl acetate in the presence of neonol AF 9-12 in the following ratio of components, parts by weight:

modified liquid glass one hundred water one hundred ethyl acetate 5-10 Neonol AF 9-12 one

The disadvantage of the composition in the known method is the susceptibility of the formed grouting mass to syneresis when using ethyl acetate as a structurant, in addition, the latter is a flammable liquid and fire safety measures should be taken when working with it.

The closest analogue is the composition for isolating water inflows into the well, including an aqueous solution of sodium silicate, sodium silicofluoride, triacetin and wood flour (US Pat. RF 2244819, E21B 43/32, publ. 20.01.2005, Bull. No. 2). According to the known invention, a composition prepared on a day surface is pumped into the formation in the following ratio of components, wt.%:

An aqueous solution of sodium silicate with a density of 1.36 g / cm ³ and silicate module M = 3.0 90.0-95.0 Sodium silicofluoride 3.0-8.0 Wood flour 1.0-4.0 Triacetin 1.0-4.0

A disadvantage of the known composition is that when the composition is injected, insoluble part of sodium silicofluoride is precipitated in the pump of the cementing unit due to the low solubility of this reagent - 7.62 g / l (Big Encyclopedic Dictionary. Chemistry, Big Russian Encyclopedia, M., 2000, p.362), therefore, compliance with the technology and accurate dosing of the components of the composition are required. Stopping the pumping process to clean a clogged pump can lead to an emergency — curing the composition in the tubing.

The technical task of the proposal is to increase the manufacturability and efficiency of repair and insulation works due to the use of a homogeneous composition with a higher insulating ability in the insulation method and eliminating an emergency situation - curing the composition in tubing.

The problem is solved by the method of isolating water inflow in the well, including the injection of sodium silicate and silicofluoride salt into the required isolation interval.

What is new is that sodium silicate and an aqueous 5-15% solution of silicofluoride salt are pumped sequentially in equal volumes through a buffer of fresh water, and ammonium silicofluoride is used as the silicofluoride salt.

The reagents used in the inventive composition are presented in table 1.

Table 1 Reagent Name Name GOST or TU Appearance Liquid sodium glass (sodium silicate) GOST 13078-81 thick yellow or gray liquid without mechanical impurities and inclusions visible to the naked eye Ammonium silicofluoride TU 6-09-1927-92 white crystalline powder, soluble in water

The essence of the proposed technical solution consists in blocking the insulated interval during the repair and insulation work with the plugging mass formed during the sequential pumping and mixing of the components of the waterproofing composition. The volume of the waterproofing composition may be 3-10 m ³ depending on the geological and technical conditions in the well. When implementing the method, sodium silicate and a solution of ammonium silicofluoride, separated by a buffer from fresh water, are sequentially pumped into the insulated interval through tubing pipes lowered into the well. The use of highly soluble ammonium silicofluoride - 187.5 g / l (Big Encyclopedic Dictionary. Chemistry, Big Russian Encyclopedia Publishing House, Moscow, 2000, p. 42) in the proposed proposal allows to obtain a homogeneous composition, the component of which does not drop out sediment when it is pumped into the well. The method of sequentially pumping the components of the composition makes it possible to use solutions of high concentration ammonium silicofluoride, up to saturated, which makes it possible to obtain a groutstone after its structuring with sodium silicate.

The composition in the laboratory is prepared as follows. 20 g of ammonium silicofluoride in 180 g of water are dissolved in a glass beaker. 100 ml of the resulting solution is added to a glass beaker with 100 ml of sodium silicate, stirred and the composition is cured for 30 minutes with the formation of a homogeneous plugging mass in the entire volume. The remaining compositions are prepared similarly, and they are presented in table.2.

Testing the water-insulating ability of the proposed method and prototype is carried out on reservoir models 30 cm long and 2.7 cm in internal diameter, filled with quartz sand of a fraction of 0.2-0.3 mm, which allow simulating the injection of reagents into the formation. The formation model was saturated with produced water, after which, according to the proposed method, sodium silicate, a buffer from fresh water, a solution of ammonium silicofluoride according to the recipes from Table 2 were pumped and left to react. The amount of injected composition was equal to the pore volume of the reservoir model. After 24 hours, water was pumped in and the breakthrough pressure of the water was determined. The average results of model tests are presented in table 2.

When using a concentration of a solution of ammonium silicofluoride of less than 5%, curing of the composition does not occur, and the use of more than 15% of a solution is impractical, since a saturated solution is formed and the precipitation of insoluble ammonium silicofluoride begins. The results of model tests indicate that the breakthrough pressure of the model according to the proposed method is on average 20% higher than for the model with the composition according to the closest analogue, which indicates its better insulating ability.

An example of practical application.

The proposed composition is used to isolate the waterlogged layer in the Bobrikov horizon, in the well of the Romashkinskoye field with a current bottom of 1230 m and a perforation interval that has opened the productive horizon in the range of 1180-1200 m. Underground equipment is lifted from the well, pumping and compressor wells are lowered to a depth of 1180 m pipes with a diameter of 73 mm.

table 2 The content of reagents in the composition Breakthrough pressure of the model after reacting for 24 hours, MPa / m Sodium silicate, vol.% Water, vol.% Ammonium silicofluoride, vol.% The proposed method The composition of the claimed method one hundred 97 3 - one hundred 95 5 21.1 one hundred 90 10 22.5 one hundred 85 fifteen 23.3 one hundred 80 twenty 23.9 The composition of the closest analogue Sodium silicate, wt.% Silicon fluoride, wt.% Wood flour, wt.% Triacetin, wt.% Prototype 95 3 one one 16.3 90 8 four four 18.5

A 10% solution of ammonium silicofluoride is prepared on the day surface in the measuring unit of the cementing unit, for which 200 kg of ammonium silicofluoride are dissolved in 1.95 m ^{3 of} water and the resulting solution is stirred for 15 minutes. 2 m ^{3 of} sodium silicate, 0.2 m ^{3 of} fresh water, 2 m ^{3 of a} solution prepared in a cementing unit of a solution of ammonium silicofluoride, and industrial water in a volume of 3.6 m ³ for forcing the composition into an insulated interlayer are successively pumped into the tubing. Next, the tubing is lifted 200 m to prevent them being caught by the hardened composition and the well is left to react for 24 hours. During this time, the composition is cured and blocks the flooded layer. Then the well is mastered, the underground equipment is lowered and the well is put into operation.

Thus, through the use of a method of isolating water inflow zones in a well and a water-insulating composition, which is a homogeneous system, a grouting mass with a high insulating ability is formed and an increase in manufacturability and efficiency of repair and insulation works, a decrease in the volume of produced water by 25-30%, respectively and lower material costs for water production.

Claims (1)

A method of isolating water inflow in a well, comprising injecting sodium silicate and silicofluoride salt into the required isolation interval, characterized in that sodium silicate and an aqueous 5-15% solution of silicofluoride are pumped sequentially in equal volumes through a buffer from fresh water, and as silicofluoride salts use ammonium silicofluoride.