RU2529080C1 - Selective composition for repair and isolation in oil and gas wells - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to compositions for isolation of inflow of formation fluid in wells located in watered zones at pull-out of hole under conditions of abnormally low formation pressures. Proposed composition comprises 10 vol. % of water-repellant organosilicon fluid ("ГКЖ-11Н"), 85 vol. % of ethyl silicate "ЭТС"-40 as catalyst and 5 vol. % of diatomite as thickener.

EFFECT: higher efficiency of said jobs.

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Description

The invention relates to the oil and gas industry, namely, compositions for isolating the influx of formation water in wells located in heavily flooded areas during overhauls in wells under conditions of abnormally low formation pressure (ANPD), in particular, to limit and eliminate water inflows, interstratal behind-the-casing flows and fixing collectors in oil and gas wells.

The main requirements for water-insulating compounds during cattle are the selectivity of the impact on the reservoir. They must isolate the influx of formation water, that is, pass through the hydrocarbon component (gas, oil, gas condensate) and cut off the water coming from the formation, in other words, be a water repellent for water, but have hydrophobizing ability for oil.

A known composition for the selective isolation of produced water in oil and gas wells, consisting of organosilicon compounds of polyphenylethoxysiloxane (modifier 113-63, 113-65) and a catalyst of sodium ethylsiliconate GKZH-10 or sodium methylsiliconate GKZH-11 [SU 1078036 A1, IPC5 E21B 43 / 32, publ. 1984], in the following ratio of components, vol.%:

polyphenylethoxysiloxane - 75-99, aqueous-alcoholic solutions of sodium ethylsiliconate GKZh-10 or sodium methylsiliconate GKZh-11 - 1-25.

The disadvantage of this composition is the low insulating ability when eliminating the influx of formation water in wells with AAP, since there is no ability to block formation water.

Also known is a composition for isolating formation waters, eliminating interstratal and annular flows, including organosilicon liquid (GCR) and an alcohol-containing solution — an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 5.0-7.5% at a volume ratio of 1: 1 [RU No. 2032068 C1, IPC6 E21B 33/138, publ. 1995].

The disadvantages of this composition are its low efficiency, lack of selectivity with respect to hydrocarbons and the high cost of work when isolating formation water in super collectors, which include Cenomanian gas deposits, when the costs of chemicals for performing one operation to isolate water in these reservoirs increase many times.

The closest technical solution chosen for the prototype is a water-insulating composition containing GKZh-10 or GKZh-11 hydrophobizing silicone fluid, an aqueous solution of polyvinyl alcohol (PVA) and aluminosilicate microspheres (AFM), with the following ratio of components, vol.% [RU No. 2211306 C1, IPC7 E21B 33/138, publ. 2003].

The disadvantages of this composition are the lack of insulating ability when eliminating the influx of formation water in wells with ANP due to the lack of selectivity of the composition by the method of influencing the bottom-hole formation zone (PZP), although blocking of the PZP is available, but only for hydrocarbons and formation water, in addition , the complexity of preparing the composition, since it consists of three components and requires preliminary preparation at the mouth. In addition, the impossibility of conducting work on the isolation of formation water in low- and medium-permeable reservoirs, because the geometrical breaks of the microspheres do not allow the composition to be pumped (crushed) into the pore space of a water-saturated reservoir; moreover, this composition is not distinguished by high adhesive and fastening properties and is not able, along with waterproofing, to fix a weakly cemented reservoir in the near-wellbore zone of the formation.

The objective of the invention is to increase the efficiency of repair-insulating works (RIR) in wells located in heavily flooded areas in the conditions of the API.

The technical result when creating the invention is to develop a selective composition for repair and insulation works, which provides selective isolation of water while maintaining the ability to pass hydrocarbons through it (oil, gas, gas condensate) in reservoirs of any permeability from super collectors to low permeability and to consolidate the rocks of the bottom-hole formation with preservation FES of oil and gas collectors.

The task and technical result are achieved in that the composition for isolating the influx of formation water consists of GKZh-11N hydrophobizing organosilicon liquid, ETS-40 ethyl silicate additive and diatomite thickener, with the following ratio of components, vol.%: GKZh-11N - 10, ETS-40 - 85, diatomite - 5.

In oil and gas practice, the ability of various organosilicon compounds (CBS) in the presence of water to enter the hydrolytic polycondensation reaction and the lack of interaction with oil is known. To implement and accelerate the hydrolytic polycondensation reaction with the alkoxy derivative of KOS (ETS-40), it is necessary to introduce acidic or alkaline catalysts. For these purposes, GKZh-11N in the amount of 10% of the volume of ethyl silicates and diatomites as a thickener and adsorbent capable of retaining the composition due to the high porosity of 85%, as well as due to the high adhesion to the rock and casing metal ( when the content of SiO ₂ 80-88%). Such a composition is practically non-toxic, explosion and fireproof, has low corrosion activity (not acid, but lower aliphatic alcohols are released during hydrolysis), high selective water-insulating properties. The resulting cement material has satisfactory strength characteristics, high adhesion to rocks and casing metal, has good hydrophobic activity. These compositions can be used in a wide range of reservoir temperatures (0-200 C °) regardless of the degree of mineralization of formation waters. The freezing point of the reagents is below minus 40 ° C, which is especially important in the conditions of the north of Western Siberia.

A comparative analysis with the prototype allows us to conclude that the inventive composition for the selective isolation of formation water inflows differs from the known one in that instead of PVA it contains a water-repellent additive - ETS-40, as a gelling agent. Instead of AFM, it contains diatomite as a thickener and adsorbent capable of retaining the composition due to the high porosity of 85%, as well as due to the high adhesion to the rock and metal of the casing strings (with a SiO ₂ content _of 80-88%). The size of the AFM is on average from 20-50 microns to 400-500 microns, and the particle size of diatomite usually does not exceed 1 micron, they consist of elongated lamellar particles of silica, up to 0.5 microns long and up to 0.1 microns thick. This suggests the possibility of using this composition in low and medium permeability reservoirs. The inventive composition becomes impermeable to water, but permeable to hydrocarbons, while due to the inclusion of diatomite in it, additional drainage of the PPP occurs due to adsorption of moisture (or water) in the surrounding rock.

Thus, the claimed composition gives the waterproofing composition new qualities, namely high selectivity, and additional adhesion to rock and casing metal at low corrosion activity, has good hydrophobic activity. The possibility of using in low- and medium-permeable reservoirs in a wide range of reservoir temperatures (0-200 ° C), and the preparation of this composition at the wellhead is possible at below minus 40 ° C, which allows us to conclude about the inventive step.

For experimental verification, formulations with different amounts of ingredients were prepared. The purpose of the experiments was to obtain permeability recovery coefficients from technological operations corresponding to the tested technology for isolating water-saturated formations using a well filter model, which is a water-saturated rock sample.

The order of the experiments. The model of the bottomhole filter is provided by the following conditions. A core sample is placed in a core holder. An intra-pore (reservoir) pressure of 4 MPa and a crimping pressure (mountain) of 20 MPa are created. The experiments reproduce the effective pressure equal to the difference between the rock and reservoir pressure, adopted in the tests equal to 16 MPa. Cell temperature - 60 ° C.

Formation water is filtered through a water-saturated model of the bottomhole filter to determine its water permeability; this permeability is basic. Then the liquids GKZh-PN (TU 2229-276-05763441-990, ETS-40 (GOST 26371-84), diatomite (TU 5761-001-25310144-99, are filtered, are light porous rocks from white to yellowish-gray, 96% consists of aqueous silica (opal) of the general formula SiO ₂ · nH ₂ O).

The sequence and volume of fluid filtration correspond to the exposure technology, see table. The basic permeability of rock samples by formation water and kerosene was separately measured.

Upon completion of the activities established by the tested technology, an exposure is performed for 12 hours.

After that, the permeability of the rock sample is measured.

During testing, the differential pressure (dP) on the core and the volumetric filtration rate (Q) are measured. The value of the Q / dP ratio, which is used in the calculation of permeability, is determined.

Permeability is determined by the formula:

$$K=\frac{\mathrm{one}}{36}\left(\frac{Q}{\Delta P}\right)\mu \frac{L}{S}\text{(one)}$$

where: K is the permeability of the sample, 10 ^-3 μm ² ;

(Q / dP), is the ratio of the volumetric gas filtration rate to the pressure drop at the ends of the bottom-hole filter model, (cm ³ / h) / MPa;

µ _i is the gas viscosity MPa · s;

L / S is the ratio of the length of the sample to its cross-sectional area, cm ^-1 ;

1/36 - conversion factor, depending on the system of units in the experiments.

The parameter characterizing the testing adopted the recovery coefficient of permeability:

$$\beta =\frac{K}{K_0}\text{(2)}$$

where: β is the coefficient of increase in permeability;

K - permeability after exposure;

To ₀ - the base permeability for produced water.

Preparation of core samples. In experiments, the downhole filter model is a pair of rock samples 30-35 mm long and 29-30 mm in diameter.

Water. The model of produced water with mineralization corresponding to the mineralization of produced water is used.

The inventive composition provides selective isolation of the influx of formation water in flooded wells under the conditions of oil production with preservation of the productive characteristics of the bottom hole, as evidenced by the results of the core study shown in the table. With high selectivity, the optimal composition provides additional adhesion to rock and casing metal at low corrosion activity, has good hydrophobic activity. It is possible to use in low- and medium-permeable reservoirs in a wide range of reservoir temperatures (0-200 ° C), and the preparation of this composition at the wellhead is possible at below minus 40 ° C.

It should be noted that when the concentration of HCL in the ETS is more than 10%, the polymerization time is significantly reduced, which can lead to the inability to pump the waterproofing composition into the reservoir, and with a lower content of the GCR (less than 5%) in the ETS, the polymerization process increases significantly, which is not economically justified when conducting waterproofing work at the well.

The presented results show a rather high insulating effect of the composition based on ETS 40, GKZH-11N and diatomite, applicable over a wide range of permeability of reservoir rocks, including low permeability differences, as well as reservoirs that have high permeability (up to 1 μm ² ), commensurate with core of the Cenomanian deposits, which is an important point for isolating the influx of formation water.

The mechanism of formation of an impermeable screen for water from organosilicon compounds when introduced into the borehole zone of the formation is as follows. The composition based on ETS 40, GKZh-11N and diatomite dissolves in hydrocarbon production intervals and enters into a hydrolytic polycondensation reaction with water contained in waterlogged intervals in the absence of interaction with oil. The penetration of the composition into water-saturated formations causes the formation of a zone consisting of a porous medium saturated with a polymer mass, the viscosity of which, when interacting with water, increases with increasing concentration up to a complete loss of fluidity. From this moment, the penetration of the plugging polymer mass into the pore channels stops. The chemical reaction of injected substances with produced water is carried out according to the mass transfer scheme. In this case, the process can be represented as the supply of a reagent to the reaction surface with the subsequent distribution of reaction products in an aggressive environment. The neutralization of the reagent in a moving aggressive phase goes to zero concentration. The staircase-type polymer formed in a porous medium, with strong adhesion to the sandstones of the rock due to the content of diatomite, clogs water-saturated intervals and cementes sand in the encircled zone of the formation.

Claims (1)

Composition for selective repair and insulation works in wells, including hydrophobizing organosilicon fluid (GKZh-11N), hydrophobizing additive as a catalyst and thickener, characterized in that it contains ethyl silicate ETS-40 as a hydrophobizing additive and diatomite as a thickener, in the following ratio of components, vol.%:
GKZH-11N 10, ETS-40 85, Diatomite 5