SU1709071A1 - Method of lowering bottomhole permeability by coagulation and crystallization - Google Patents

Abstract

The invention relates to the construction of wells, in particular to methods for reducing the permeability of the formation. The goal is to improve the efficiency of the method of reducing the permeability of the reservoir by increasing the degree of clogging while expanding the temperature range. In a well filled with a water based mud, the bottomhole formation zone (PPP) is sequentially treated with suspensions of silica-containing and lime-containing components. Bore mud solution is used as a silica-containing component. To enhance coagulation-crystallization reduction of permeability of a PPP, the solution in the PPP is replaced with a clay solution treated with a reagent that forms a water-soluble compound when interacting with calcium oxide, for example A12 ($ 04). . Fe2 (S04b. NaSIFe. The method allows to reduce the permeability of the PPP at 22 ° C. 1 Cpfl, 3 table.9 ^

Description

The invention relates to the construction of wells, in particular to methods for reducing the permeability of the formation.

The purpose of the invention is to increase the efficiency of the method by increasing the degree of clogging while expanding the temperature range.

The bottomhole formation zone (PPP) is successively treated with aqueous suspensions of silica-containing and lime-containing components, and clay-based mud is used as the silica-containing component in the wells and in the pores of the PPP. Such a processing sequence produces an effect even if the PPP is treated only with streams of a suspension of the lime-containing component, but the clay solution, in addition, must have a clay concentration of at least 13 wt.%. When the mud in the well contains a smaller amount of clay, it is preferable to place the pre-clay solution treated with a chemical reagent that forms a water-resistant compound when interacting with calcium oxide solution, for example A12 (5O4) h. Fe2 (S64) 2. NaaSlFe.

When using a washing liquid in the form of a water-based mud solution with a density of 1100-1200 kg m, the concentration of the solid phase is so high (15-27 wt.%) That it becomes possible to treat the llast only with a lime suspension. A lime spray slurries a portion of the mud into the reservoir, which, due to the presence of Ca ions, coagulates. compacted into the reservoir. Chemically abundant lime

BaaMMOAeAcTByet with active centers of clay particles with the formation of the corresponding crystalline hydrates, thereby consolidating the screen structure and facilitating the formation of a high-strength screen. Restrictions on density due to the possibility of / g / chen rugged screen. With p 11SU kg m7 / 15 May. % clay) the solids content in the solution is low, therefore it is not possible to obtain a durable screen, at p 1200 kg-m (27 wt.% clay) the solution thickens too much and it is difficult to ensure its penetration into the formation in sufficient quantity, which again leads to reduce the strength of the screen.

When the density of the solution is less than 1100 kg m, it is necessary to change the sequence of operations, since if it is kept as in the prototype, it is impossible to obtain crystallization after the coagulation structure, which reduces the strength of the screen. During the initial treatment of the reservoir with lime and subsequent ingress of clay particles into the reservoir, they coagulate, thicken on this screen, and, just like the early method, are formed. Calcium hydrosilicates and calcium hydroaluminosilicates at a later date and contribute to the formation of a durable screen. Treatment of the clay solution with trivalent metal sulphates leads to the early formation after coagulation of the structure within the calcium hydrosulfate screen and the corresponding chemicals, the formation of which leads to a strong increase in volume, which leads to a strain on the structure of the screen and increase its strength.

If we take into account the total change in the volume of the system (solid phase + liquid), then the coagulation process is accompanied by its increase, since significant amounts of physically bound (pseudocrystalline) water are released, which increase in density (p 1.3–1.5) and in free (p - 0.75). The increase in the volume of water released exceeds the decrease in the volume of the solid phase (solid body is entrained water) and therefore the total volume of the system increases. In order to confirm the indicated positions, connected with changes in the volume of the System in the process of coagulation, special experiments were carried out at the facility. The experimental setup consists of a sealed glass vessel (CW capacity cm, inner diameter 60 mm), which is connected with a measuring joint by means of a connecting joint. The hermetic container was filled with the test mixture (or two mixtures) and the change in its volume with time was measured.

The coagulation process at the boundary between the clay solutions and the lime slurry was accompanied by the formation of a compacted zone of coagulated clay and a zone of the seized water. During the coagulation process, the total volume of the system (solid phase + liquid) increases, while

0, the total volume of the clay solution treated with lime slurry remains virtually unchanged before being placed into the experimental setup (a slight increase in volume is explained by the passage of stopping coagulation processes). In mixtures of lime slurry with clay solutions treated

Al2 (S04) 3, - Fe2 (504) C: NaaSfFe,

The processes of coagulation and crystallization structure formation proceed, accompanied by physicochemical binding of water, and as a result, an increase in the volume of the solid phase and a decrease in the total volume of the system as a whole. Table 1 shows the efficiency of the method compared to the known one.

Table 2 shows the compositions of silica-containing and lime-containing

0 components, of which gotbvili suspension.

Table 3 shows the data on the change in the volume of slurry mixtures for blasting the bottomhole zone of the permeable formation.

Examples characterizing the invention.

Artificial dog kernels with permeability were made.

0 m. The experimental setup consists of a test chamber, a nozzle and a core holder, in which the core is placed.

The tests were carried out in the following sequence.

5 In the method, taken as a prototype, the chamber is filled with a clay solution, then the cores are processed through the nozzle, first with a stream of silica-containing slurry, then with lime-containing slurry.

In the proposed method: A. The chamber is filled with a clay mortar, then the core is treated with a jet of lime-containing

5 suspensions.

B. The chamber is filled with a clay solution, then a core is processed through a nozzle, first with a stream of lime-containing suspension, then with a stream of mud.

B. Same as B, but with pretreatment of the mud: А12 {504) з;

Fe2 (504) h; Na2SIF6.

After processing, the core is removed from the core holder and exposed to various temperatures for 4 hours. After heat treatment, the cores were tested for reverse permeability. During the test, the pressure at which the initial permeability was restored was recorded.

The proposed method is more efficient than the prototype and allows the temperature range of applicability of the method to be extended towards lower temperatures.

Claims (3)

1. Method of coagulation-crystallization reduction of permeability of the bottomhole formation zone (PZP) well. The effectiveness of the processing method. water-based mud using sequential bottomhole formation zone (PZP) treatment with silica suspensions of limestone and lime containing components, characterized in that, in order to increase the efficiency of the method by increasing the degree of clogging while simultaneously expanding the temperature 10 range, as a silica-containing component, the mud is used in the well and in the pores. PPP. 2. The method according to Claim 1, whether or not 15 by replacing the solution in the PPP with a clay solution treated with a chemical reagent that forms a water resistant compound when interacting with calcium oxide before the treatment .. 20 Tab 1 an experimental treatment of the slurry-silica component and 120 specific Lime suspension in the presence of mud in the well density, kg / m (May. Clay): 1210 (28) 22 1200 (27) .22. 1150 (21). 120 1100 (15) 80 1090 (13) 180 Treatment with an effector and later with a clay solution with / 1090 kpm (13 May. Clay) B. Treatment with lime component and subsequent clay mortar / pretreated: ALjCSO) Fej (SO,), VijSiFe The composition of the components of suspensions Prototype 0.6 3.8 Broken way 0.5 5.2 6.8 5.0 2.1. 5.2 22 7.Z 120 8.2 200 8.2 Core destruction Core destruction 6.08 .8 The destruction of the core 7.2 9.50 12.1 table 2 Experimental data on determining the change in volume of the ivesta clay (lime + treated clay) Separate solutions: lime suspension (200 cm) and clay solution (300 cm)  - 115Q kg / n (2t wt.1) +5.8 Mixed solution: lime suspension (200 cm) and clay solution (300 SI) f - 1150 kg / m (21 wt.1) -1-0.3 Mixed solution: lime suspension (200 cm) and clay solution (300 cm) (13 wt.%) / 1090 kg / m, treated with "1, 2 alm AL, (SO"), Same as 3. CLAY solution / 1090 kg / m (13,) treated with Fe {(, Even as 3, clayey rastilf P - 1090 kg / m, (13 masl) (treated with HajSifj-5.0 Table3 +8.3 - "- I, +1," 9, 63 +7.6 +0.8 +0.06 + 0.12 +0.16 +0.6 -6.3 -0.82 -1.16 -1.23 -5.9 -6.6 -0.92 -1.20 -1.29 -7.2 -1.00 -1.33 -1.1