RU2405020C2 - Compound for isolation of water inflow in gas wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to gas production industry, namely to compounds for selective isolation of bottom waters in gas wells and can be used during waterproofing works in gas wells at development of gas and gas condensate deposits. Compound for isolation of water inflow in gas wells contains the following, wt %: surface active agent Neftenol ABR 1-10, hydrocarbon solvent- highly volatile component chosen from the group: gas condensate, gas condensate distillate, petroleum ether, natural gasoline or their mixture 90-99.

EFFECT: improving waterproofing capacity, reducing water content of produced gas.

9 ex, 4 tbl, 2 dwg

Description

The invention relates to the gas industry, in particular to compositions for the selective isolation of bottom water in gas wells, and can be used for waterproofing works in gas wells in the development of gas and gas condensate deposits.

A known method of isolating water inflow in gas wells, including injecting into the bottomhole portion of a suspension of a water-soluble polymer in an organic fluid (RU 2188930 C2, E21D 33/138, 2002).

The disadvantage of this method is the difficulty in implementation and lack of effectiveness.

There is a method of isolating the inflow of bottom water into the well, which consists in pumping aerated cement mortar into the bottomhole zone, and after injecting aerated cement mortar, fluorosilicone fluid sumps are pumped into the bottomhole zone (AC 939739, Е21В 43/32, 1982).

The disadvantage of this method is the increased water cut of gas wells and the lack of efficiency of the process of isolating water inflow in gas wells.

A known composition for isolating the zones of absorption and inflow of formation water into the well, including the waste of the oil preparation process and an organic solvent - APC, and a method of preparing a composition for isolating the zones of absorption and inflow of formation water into a well, involving mixing an organic solvent with the waste of the oil preparation process (RU 2126082 C1, E21B 43/22, 1992).

Closest to the invention is a composition for isolating the zones of absorption and inflow of formation water into the well, including the waste of the oil preparation process and an organic solvent. Additionally, this composition contains a surfactant - ethoxylated alkyl phenol, for example OP-10 or neonol AF 9-12, and as a waste of the oil preparation process it contains oil sludge cake thickened on belt press filters (RU 2177539 C2, ЕВВ 43/22, 1999).

The disadvantage of this composition is the entry of bottom water into the well due to its breakthrough from the underlying horizons through the most permeable sections of the formation. In addition, this composition is ineffective, since the injected fluid cannot be easily removed from gas-saturated areas of the reservoir, and has a low selective ability.

The objective of the invention is to develop an effective composition for isolating bottom water in gas wells by selective exposure to the water-saturated part of the reservoir.

The technical result of the invention is to improve the water-insulating ability of the claimed composition, providing a reduction in water cut of the produced gas in the development of gas and gas condensate deposits.

To achieve the technical result, a composition for isolating water inflow in gas wells containing a surfactant and a hydrocarbon solvent, according to the invention, contains Neftenol ADB as a nonionic surfactant, and a volatile component from the group: gas condensate, distillate as a hydrocarbon solvent gas condensate, petroleum ether, gas gasoline or a mixture thereof, in the following ratio of components in wt.%:

Neftenol ADB 1-10 hydrocarbon solvent rest.

Water repellent Neftenol ADB is produced in accordance with TU 2483-081-17197708-03. As a volatile hydrocarbon solvent, the following can be used: stable and unstable gas condensate, gas condensate distillate, unstable gas gasoline, petroleum ether and other similar hydrocarbon solvents or mixtures thereof. At the same time, a volatile hydrocarbon solvent must contain at least 80% of components whose vapor pressure in the produced gas should be lower than the saturation pressure at the temperature of the bottom-hole formation zone. Therefore, methane deposits are most suitable for the use of the claimed composition.

Gas condensate or gas condensate distillate is available in the field and therefore their use reduces transport costs, which is especially important in the Far North. The low freezing temperature of Neftenol ADB and a volatile hydrocarbon solvent allows processing in the autumn-winter period.

The composition is prepared by mixing the components to obtain a homogeneous system.

To implement the process, the proposed composition is pumped into the well through elevator or tubing or using a coiled tubing installation.

The composition arrives mainly in the water-saturated zone of the bottomhole zone of the well. In this case, there is a decrease in the permeability of the porous medium for water due to the action of the water repellent and the saturation of the porous medium with hydrocarbon. Thus, the water insulating effect of the composition is associated with a decrease in phase permeability to water. Most of the composition entering the gas-saturated layers is easily displaced by the gas flow. Subsequently, the evaporation of the volatile hydrocarbon solvent into the gas stream allows you to quickly remove the remaining part of the solvent. At the same time, the water repellent is deposited on the surface of the rock, changing its wettability. Subsequently, this will slow the flow of water from the underlying horizons. Hydrophobization of the rock suppresses capillary forces that hold water into the bottomhole zone (BHP), which will facilitate the removal of water from the BHP and increase the permeability of the formation for gas.

The inventive composition has the following characteristics:

- when injected into the bottomhole formation zone, it enters mainly in the water-saturated part of the formation (selectivity during injection);

- reduces water permeability of the water-saturated interval by 5-10 times;

- does not affect or increases gas permeability of gas-saturated sections of the formation;

- helps to remove water from gas-saturated sections of the reservoir.

Case Studies

Example 1. Based on the geological and physical characteristics of the field and well performance for processing, it is necessary to prepare 10 m ^{3 of the} composition with a Nephtenol ADB water repellent content of 1 wt.%, A hydrocarbon solvent of 99 wt.%. 5 m ^{3 of} stable gas solvent are placed in the tank condensate and gas condensate distillate and mix. Then measure the density of the obtained solvent, which is equal to 721 kg / m ³ . The required amount of ADB Neftenol is calculated. The required amount of Neftenol ADB (72.8 kg) is placed in a container with a solvent and the resulting mixture is stirred until a homogeneous system is obtained.

Example 2. Based on the geological and physical characteristics of the field and well performance for processing, it is necessary to prepare 15 m ^{3 of the} composition with a Nephtenol ADB water repellent content of 5 wt.%, Stable gas condensate - 95 wt.% 15 m ^{3 of} stable gas condensate is placed in the tank density of 742 kg / m ³ . The required amount of ADB Neftenol is calculated. The required amount of Neftenol ADB (585.8 kg) is placed in a container with a solvent and mixed until a homogeneous system is obtained.

Example 3. Based on the geological and physical characteristics of the field and the performance of the well for processing, it is necessary to prepare 6 m ^{3 of the} composition with the content of Neftenol ADB water repellent 10 wt.% And stable gas condensate 90 wt.%. 6 m ^{3 of} stable gas condensate with a density of 742 kg / m ³ are placed in the container. The required amount of ADB Neftenol is calculated. The required amount of Neftenol ADB (494.7 kg) is placed in a container with a solvent and mixed until a homogeneous system is obtained.

Example 4. Based on the geological and physical characteristics of the field and well performance for processing, it is necessary to prepare 10.6 m ^{3 of the} composition with a 5% content of Neftenol ADB water repellent. 10 m ^{3 of} petroleum ether with a density of 804 kg / m ³ is placed in the container. The required amount of ADB Neftenol is calculated. The required amount of Neftenol ADB (448.5 kg) is placed in a container with a solvent and mixed until a homogeneous system is obtained.

Example 5. Based on the geological and physical characteristics of the field and the performance of the well for processing, it is necessary to prepare 13 m ^{3 of the} composition with the content of the specified water repellent 5 wt.% And gas gasoline 95 wt.%. 12 m ³ of gasoline with a density of 792 kg / m ³ are placed in the container. The required amount of ADB Neftenol is calculated. The required amount of Neftenol ADB (541.9 kg) is placed in a container with a solvent and mixed until a homogeneous system is obtained.

Example 6. Based on the geological and physical characteristics of the field and the performance of the well for processing, it is necessary to prepare 10 m ^{3 of the} composition with the content of Neftenol ADB water repellent - 1 wt.%, Hydrocarbon solvent - 99 wt.%. 5 m ³ solvent of stable gas condensate and gas gasoline are placed in a container and mixed. Then measure the density of the obtained solvent, which is equal to 721 kg / m ³ . The required amount of ADB Neftenol is calculated. The required amount of Neftenol ADB (72.8 kg) is placed in a container with a solvent and the resulting mixture is stirred until a homogeneous system is obtained.

The composition for selective waterproofing in gas wells should have the following characteristics:

- not to reduce the permeability of gas-conducting zones and interlayers for gas;

- reduce the permeability to water of water-saturated intervals of the cut. The following characteristics also increase the effectiveness of the impact: - when pumping, the composition should mainly enter the water-saturated interval (selectivity when pumping);

- reduce the water saturation of the gas channels and interlayers of the bottomhole formation zone.

Example 7. The experiments were carried out according to standard methods. To characterize the action of the composition, the degree of restoration of gas permeability (B,%) of gas-saturated porous media was used:

B = 100 · (K _g2 / K _g1 ),

where K _g2 is the gas permeability of the formation model after injection of the composition, K _g1 is the initial gas permeability of the formation model with residual water.

The experimental results are shown in table 1.

The data in table 1 show that, unlike the prototype, the claimed composition does not reduce the permeability of porous media with residual water saturation.

Example 8. This example illustrates the waterproofing properties of the claimed composition and composition of the prototype. The experiments were carried out according to generally accepted methods using water-saturated reservoir models. The following parameters were used to characterize the compositions.

1. Resistance factor (R) to characterize the degree of decrease in the permeability of porous media in water:

R _i = (Q ₁ / ΔP ₁ ) / (Q _i / ΔP _i ),

where R _i is the current resistance factor; Q ₁ and ΔP ₁ - respectively, the volumetric flow rate and pressure drop during steady-state water filtration in stage 1 (primary water injection); Q _i and P _i - respectively, the current flow rate and pressure drop during filtration of water or composition.

In case of steady filtration:

Roc. = K ₁ / k ₂ ,

where roct. - residual resistance factor, i.e. resistance factor established after injection of the composition; k ₁ and k ₂ - respectively, the water permeability of the reservoir model before and after injection of the composition.

As the characteristics of the composition used Roc. and maximum resistance factor (Rmax.).

2. The degree of waterproofing (A,%) - to characterize the level of decrease in water intake as a result of the composition.

S = 100 (k ₁ -k ₂ ) / k ₁ = 100 (R-1) / R

The experimental results are shown in table.2.

The data in table 2 show that when the concentration of the hydrophobizing agent Neftenol ADB equal to 1-10%, the waterproofing effect of the claimed composition is higher than that of the prototype by 5.1-28.5%. At a concentration of Neftenol ADB less than 1% of the waterproofing effect is insufficient.

An important composition parameter for waterproofing is the maximum and residual resistance factor that determines its filtration characteristics. The ratio between the maximum and residual resistance factor characterizes the ratio of the injection conditions of the composition and the waterproofing effect. In the case of the prototype, the maximum factor is 30.6 times higher than the residual, i.e. the composition when pumping encounters great resistance, and the waterproofing effect is low. For the formulations under development at an ADB Neftenol concentration of 1-10%, the ratio of the maximum resistance factor to the residual resistance factor is 1.29-2.54, i.e. the claimed composition has significantly better filtration characteristics than the prototype.

Example 9. This example illustrates the selectivity of the claimed composition when injected into the reservoir. The experiment was carried out according to generally accepted methods using a two-layer reservoir model consisting of a water-saturated layer and a gas-saturated layer with buried water, the experimental results are shown in Tables 3 and 4, Figs. 1 and 2.

To characterize the selectivity during injection, we used the ratio of the volumetric rate of injection into a water-saturated interlayer to the volumetric rate of injection into a gas-saturated interlayer (Q water / Q gas).

The data obtained show that when pumping the inventive composition and composition according to the prototype, there is a constant redistribution of the injected fluid flow between the models of water and gas saturated layers. The rate of arrival of compounds in a water-saturated interlayer increases, and in a gas-saturated layer decreases.

In the case of the claimed composition after injection of 0.28 bp the main amount of the composition enters the water-saturated interlayer, and with an injection volume of 0.91-0.94 bp, the ratio of Qwater / Qgas is 5.22-5.26.

For the prototype, the ratio Qvoda / Qgaz even after pumping 1.42 bp composition does not exceed 0.697.

Thus, the selectivity when downloading the inventive composition significantly exceeds the prototype.

Compared with the prototype, the inventive composition has several advantages. It does not reduce the permeability of gas-permeable layers for gas, has better water-insulating and filtration characteristics, greater selectivity when injected into the reservoir.

It is expected that the use of the composition in 3-10 times will reduce the rate of flow of water into the gas well and increase its productivity by 5-20%. The most suitable objects for the introduction of the inventive composition are methane deposits confined to the Cenomanian horizon.

Claims (1)

Composition for isolating water inflow in gas wells containing a surfactant and a hydrocarbon solvent, characterized in that it contains Neftenol ADB as a surfactant, and a volatile component from the group gas condensate, gas condensate distillate, petroleum as a hydrocarbon solvent ether, gas gasoline or a mixture thereof in the following ratio of components, wt.%:
neftenol adb 1-10 hydrocarbon solvent 90-99

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