Hydrophobic agent for treatment on bottom area of formation

FIELD: oil and gas production.

SUBSTANCE: bottom area of formation is treated with hydrophobic agent, in particular solution of ethylene/vinyl acetate copolymer expressed by general formula [-CH₂-CH₂-C(CH₃COO)H-CH₂-]_n, where n=7000-10000, in hydrocarbon solvent.

EFFECT: increased source of inexpensive hydrophobic agents with improved adhesion properties, intensified oil recovery due to increased depth of penetration of hydrophobic agent into formation, improved environmental conditions in development of oil formations, and reduced oil production expenses.

2 tbl, 2 ex

The invention relates to the oil industry and is intended for processing bottom-hole zone of the well.

Currently, many of the deposits are at a late stage of development. Mining using artificial or natural active water regime at this stage is accompanied by the production of a large volume of associated formation water. Pumping, food preparation and disposal of this water requires significant material costs, and increases the environmental burden in the region of oil and gas production. This determines the importance of addressing limitations in the production of associated water. One way to solve it is the quality of the waterproofing works on wells.

Known use as a hydrophobic agent, hydrophobic silica in an organic solvent with a concentration of from 0.05 to 2 wt.%. /patent RF №2105142, IPC 6 E 21 In 43/22, publ. 20.02.98/.

It helps to increase the flow rate of oil wells up to 2.5 times with a slight decrease in water content of produced fluids (5-10%).

Disadvantages of the use of this agent are relatively low efficiency to increase the output of the wells and a slight decrease in water content of produced fluids.

Know the use of the La intensification of oil production as a hydrophobic water-repellent powder dispersed hydrophobic material based on silicon dioxide or a metal oxide, the surface which is activated carbonates of alkali metals, chemically modified Organoelement compound of General formula Cl_4-nSiR_nwhere n=1-3, R=H, methyl-, ethyl-, Cl -, methyl-, phenyl-, with subsequent additional processing compound selected from the group comprising tetramethoxysilane, tetraethoxysilane, the oligomer polymethyl(ethyl)siloxane, polymethylsiloxane in quantities of 0.5-1.0 wt.% /patent RF №2089499, IPC 6 01 33/18, 09 With 1/281, 3/12, publ. 10.09.97/.

For processing bottom-hole zones of oil wells hydrophobic powder is used in the form of a suspension in an organic solvent per linear meter effective area of the power layer.

The most effective known hydrophobic powders in a hydrocarbon solvent with a concentration of not less than 0.5-2%, low concentrations may cause flooding of the bottom wells.

During the period of extended operation will inevitably decrease the concentration of hydrophobic powder on the surface of the collector due to its desorption and removal of the bottom-hole formation zone (PPP). This has a negative effect on the duration of action of hydrophobic agent, and, in addition, at lower concentrations there is an inversion of wetting, that is, the surface of separation of the phases becomes hydrophilic, and there is danger of breaking the produced water to affected by the oil well, that will lead to adverse effects (increased production of produced water). In addition, it shortens the turnaround activities for production wells.

The disadvantages of the known hydrophobic agents is that uploading them at elevated concentrations often leads to plugging of the pore space of the bottomhole zone of the formation due to the comparability of the pore size with a particle size of suspensions of hydrophobic powder, which limits their use in low-permeability reservoirs. In addition, the suspension is an unstable system and be prepared immediately before injection, which requires additional equipment. Technology solution preparation of highly dispersed hydrophobic powder of oxides of silicon and oxides of metals require special conditions (respirators). Modified oxides are very expensive components, and use them in the processing of wells, at the late stage of development unprofitable.

The task of the invention is the expansion of the Arsenal cheap hydrophobic reagents with high adhesive properties, the intensification of oil recovery by increasing the depth of their penetration into the formation (increase in the effective radius of the processing PPP) when using ICT the spent solution instead metastability suspensions of hydrophobic powders; excluding the effect of inversion wetting fall concentrations of hydrophobic agent associated with desorption from the surface of the breed in the lifetime of the well and, therefore, longer turnaround activities for production wells; enhancement of the environmental performance of oil reservoirs; simplifying the preparation of solutions of hydrophobic agents; reduction of oil production.

The problem is solved by applying a solution of a copolymer of ethylene and vinyl acetate of General formula [-CH₂-CH₂- (CH₃COO)N-CH₂-]n, where n=7000-10000, in a hydrocarbon solvent as a hydrophobic agent for treatment of bottom-hole formation zone.

Table 1 - assessment of the water-repellent action of the compounds, depending on its concentration in the organic solvent, in table 2 - change in permeability of water and oil in the processing of 0.1% of the CMEA in an organic solvent with different degree of polymerization n.

Offered as a hydrophobic agent is a copolymer of ethylene and vinyl acetate (CMEA) can be any brand. Use it for oil production is unknown. CMEA is a high-molecular compound related to the polyolefins. He has enhanced adhesion to various materials. It is used for the manufacture of blown articles hoses, pads, toys. It transforms weather-resistant, transparent film. High adhesive properties CMEA and good compatibility with waxes gives the opportunity to use it as a paper coating, metal packaging. Hot melt adhesives based on them do not contain solvents. They are widely used in printing, furniture, footwear and other industries.

Use offer a hydrophobic agent, as usual, in the form of a solution in a hydrocarbon solvent.

On the action of capillary forces and the degree of adsorption can be judged by the rise of water in the capillary. In order to take into account the efficiency of adsorption in the pore channels, which have their own characteristics, it is necessary to use capillaries, filled with quartz sand.

The method of estimating water-repellent action of lifting the water in the capillary. The solution is hydrophobic agent in a hydrocarbon solvent impregnated activated and inactivated quartz sand with a diameter of 0.14 to 0.25 μm, activated sand - hydrophilic (Hcl treated) and inactivated sand (not processed Hcl, partially hydrophobic). Dried in a drying Cabinet for twenty-four hours or until dry. Sand, soaked and dried, fill through the funnel in the tube height 16 see Condense laboratory shaker 250 cyclo is per minute at an amplitude of 4 for 15-20 minutes. Filled tubing with active and neaktivirovannye sand treated with the investigated solutions, put in a conical flask with distilled water (always the same). Note the time. Stand for five hours, measuring the height of rise of water in capillary through every 10 minutes. The obtained results are processed and build graphs of wetting and diagrams of the effect.

Example 1. According to this method the solution CMEA (2%) in diesel fraction (diesel fuel DT) impregnated with quartz sand (activated and non-activated) with a diameter of 0.14 to 0.25 μm. Dried within twenty-four hours or in a drying Cabinet to dry. Sand, soaked and dried, rolled up in a tube height of 16 cm with a Shoe through the funnel. Condense laboratorni shaker 250 cycles per minute at an amplitude of 4 for 15-20 minutes. Tube Packed with activated and neaktivirovannye sand, treated with a solution of CMEA (2%) in diesel fuel, put in a conical flask with distilled water (always the same). Note the time. Stand for five hours, measuring the results of every 10 minutes. The obtained results are processed and build graphs of wetting and diagrams of the effect.

Similarly were conducted other experiments, the results of which are shown in table 1.

However, when the transition to Promyshlenny testing is necessary to take into account the complex geological and physical conditions: the heterogeneity of sites with different degree of saturation and the water content, the degree of desorption of water-repellent with rocks, the fact that low concentrations and possible Hydrophilidae his behavior, which can lead to the formation water breakthrough. It was therefore conducted a series of experiments by determining the change in the permeability of water and oil before and after treatment with the composition of the reservoir models with different filtration characteristics, different water and oil saturation. Evaluated the degree of desorption of water-repellent surface species during filtration of oil and water. After what has been estimated coefficients of the relative permeability of oil and water before and after processing a hydrophobic agent, the calculated degree (ratio) increase for oil and reduce water.

Example 2. In models of the reservoir as the porous medium used medium-grained quartz sand (0,140-0,315 mm). As a "dry" sand were calcined quartz sand; "initial wet" "dry" sand, through which was filtered one pore volume of water; "initial saturated" - "initial water-saturated sand through which was filtered one pore volume of oil; "residual oil" - "initial oil-saturated sand through which was filtered volume of water required to achieve full water coming from the reservoir model fluid.

A similar experiment was carried out on models of the formation after treatment of the inventive reagent.

The calculation of the coefficients of permeability of oil and water before and after treatment hydrophobic agent is made according to the law Darcy.

From the obtained data shows (table 2)that in the General case for all models of the reservoir there is a decrease in the relative permeability for water (up to 11 times) and a significant increase in the relative permeability to oil (up to 9 times).

It should also be noted that the pumping 30 pore volumes of water under laboratory conditions corresponding to the complete washing of oil-saturated model of reservoir water, does not lead to desorption of hydrophobic agent from the surface of the breed, this can be judged by a constant rate of filtration of water through the formation model.

The results of the experiments are shown in the tables show that the hydrophobic agent effectively increases the permeability intervals with an initial saturation and high productivity online who ralov with residual oil saturation restored to original. The latter is important to extract residual oil is washed out and transported by water flow, and the better, the higher the filtration rate in the bottom hole zone of the well.

Application of the inventive agent can increase the permeability of oil at 2-8,75 times, and lower permeability on water 11 times (see table 2). In addition, the combination of known adhesion properties of the CMEA and the hydrophobic effect can reduce corrosion of oilfield equipment.

Known hydrophobic powder in the hydrocarbons under the same conditions leads to a decrease of the permeability of high-permeability intervals, which hampers their effective development and can lead to lower final oil recovery.

The proposed hydrophobic agent is cheaper silicone hydrophobic powder about 20 times. Use it rationally in concentrations of 0.05-2%.

Applying a solution of a copolymer of ethylene and vinyl acetate of General formula [-CH₂-CH₂- (CH₃COO)N-CH₂-]_nwhere n=7000-10000, in a hydrocarbon solvent as a hydrophobic agent for treatment of bottom-hole formation zone.