RU2309248C1 - Oil field development method - Google Patents

Abstract

FIELD: oil production, particularly to develop oil fields formed by thick fractured and cavernous fractured water-saturated carbonate seams with low reservoir properties, high oil viscosity and to develop terrigenous reservoirs.

SUBSTANCE: method involves serially injecting of gel-forming and deposit-forming compositions in reservoir; forcing thereof into reservoir; estimating productive reservoir thickness propagation through field thickness; determining injection well injectivity and admissible production string pressure; performing injection operation beginning from injection wells with high injectivity. The gel-forming composition is polymeric composition, which is injected in plugs beginning from 0.1-0.5% by weight polymer concentration up to 5-10% injection pressure increase. The second plug injection is stopped as polymer concentration reaches 0.5-2% by weight up to 10-20% injection pressure increase. The deposit-forming composition is alkaline agent or alkaline-polymeric composition in mineralized water presence. The deposit-forming composition amount to be injected ensures ratio between deposit-forming composition and gel-forming composition from 1:1 to 1:3 to provide 30-90% injection pressure increase. Then the composition is forced in reservoir with mineralized water having 1.0-1.2 g/cm³ density in amount of 1-3 well bore volumes. After then 1-3 day technological time-delay is exercised. Gel-forming composition for injection well having high injectivity additionally has filler taken in amount of 5-30% by weight. The filler is, for instance, mud powder, chalk or wood flour. Gel-forming composition is injected in reservoir along with simultaneous polymer supplying. The polymer is suspension and aqueous solution of crosslinker. Waste mineralized water with density of 1.01-1.2 g/cm³ is used for deposit-forming composition injection. Gel-forming composition and deposit-forming composition are injected in amount equal to fracture and cavern volume.

EFFECT: increased oil recovery due to improved strength of gel-forming layer, creation of barrier having increased structural properties along with maintenance of low-permeable interlayer permeability, simplified technology and increased technological effectiveness of oil field development, decreased material and labor inputs, as well as reduced fire and explosion hazard.

5 cl, 2 tbl

Description

The proposal relates to the oil and gas industry, namely to the development of oil fields, composed of a thick layer of fractured and fractured-cavernous water-saturated carbonate formations, complicated by low reservoir properties, high viscosity of oil, and can also be used in the development of terrigenous formations.

A known method of alignment of the injection profile in the injection and limitation of water inflow in producing wells, including the injection into the reservoir of an insulating composition based on polymers, a crosslinker and water (US Pat. RF No. 2169258, IPC ЕВВ 43/22, publ. 06/20/2001, bull. No. 17). Prior to gel formation, the insulating composition is pressed into the reservoir at a distance that ensures that the effect of depression on the gel is eliminated to a safe level. However, the method is not effective enough in the development of water-saturated, heterogeneous permeability carbonate formations.

A known method of developing an oil deposit, including sequential injection into the reservoir of gel-forming and sediment-forming compositions and forcing into the reservoir (AS USSR No. 1595063, ЕВВ 43/22, published on 10/10/1996). Before injection of the gel-forming composition and after injection of sediment-forming in the reservoir, the solvent is pumped. The solvent used is propane, butane, a mixture of light hydrocarbons, which are in a liquid state under reservoir conditions. The solvent is mixed with oil and displaces the resulting mixture to production wells. At the same time, due to capillary phenomena, the solvent is absorbed into the rock blocks, the viscosity of the reservoir hydrocarbon fluid decreases, and the saturation of its pore volume increases.

A gelling composition of the following composition, wt.%: Water glass 2.0-10.0; hypane 0.5-2.5; nitrolignin 2.0-7.0; water - the rest, is continuously pumped with rims in a volume equal to the volume of cracks, and the gelation time for the next portion is less than the previous one, and the viscosity of the subsequent portion is greater than the previous one. They stop the well for three days at the time of gelation. As a precipitating composition, solutions of sodium hydroxide or potassium hydroxide are used. The back of an alkaline solution performs the function of a release agent, prevents the premature breakthrough of the hydrocarbon solvent injected next in separate selective paths and thereby contributes to the uniform advancement of the displacement front.

The method allows to increase the degree of formation coverage by impact and to ensure uniformity of the front of displacement of hydrocarbons from fractured reservoirs.

The disadvantage is that the injection of solvent leads to in-situ deasphalting of oil, increases the fire and explosion hazard during field operations, especially in the summer. Another disadvantage is the low processability of the method, ineffective waterproofing of the fractured-pore reservoir of the carbonate formation, due to the low strength of the gelling composition.

The technical task is to increase oil recovery by increasing the residual resistance factor, the strength of the gelling layer, the formation of a barrier with improved structural properties while maintaining the permeability of low-permeability layers, as well as simplifying the technology and improving the manufacturability of the method of developing an oil deposit due to the possibility of controlling the process, reducing material and labor costs and reduction of fire and explosion hazard.

The problem is solved by a method of developing an oil deposit, including sequential injection of gel-forming, sediment-forming compositions into the formation and forcing them into the formation.

What is new is that they clarify the distribution of productive thicknesses of the formation over the area of the reservoir, determine the injectivity of injection wells, allowable pressure on the production string, injection is started from highly responsive injection wells, the polymer composition is injected as a gel-forming composition, the composition is injected with rims starting from polymer concentration 0, 1-0.5 wt.% To increase the injection pressure by 5-10%, the second rim is pumped at a polymer concentration of 0.5-2.0 wt.% To increase the pressure cells by 10-20%, alkaline reagents or an alkaline-polymer composition in the presence of mineralized water are used as the precipitating composition, the precipitating composition is pumped in proportion to the gel-forming composition from 1: 1 to 1: 3 to increase the injection pressure by 30-90%, then squeezed into the reservoir with mineralized water with a density of 1.0-1.2 g / cm ³ in the amount of 1-3 volumes of the wellbore, then produce technological exposure for 1-3 days.

Also new is that for highly-responsive wells, filler in an amount of 5-30 wt.% Is additionally added to the gel-forming composition, and, for example, breaker, or clay powder, or chalk, or wood flour is used as filler.

It is also new that the gel-forming composition is injected into the formation while feeding the polymer in the form of a suspension and an aqueous solution of a crosslinker.

Also new is that mineralized wastewater with a density of 1.01-1.2 g / cm ^{3 is} used to inject the sediment-forming composition.

Also new is the fact that the gel-forming and sediment-forming compositions are pumped in a volume equal to the volume of cracks and caverns.

The effectiveness of the proposed method is due to the following. When developing an oil reservoir represented by a fractured-porous reservoir of a carbonate formation, they perform geophysical and hydrogeological studies, specify the distribution of productive thicknesses of the formation over the area of the reservoir, determine the injectivity of injection wells, allowable pressure on the production string. The volume of injected compositions is determined depending on the volume of pore space. The injection of gel-forming and sediment-forming compositions is carried out in a volume equal to the volume of cracks and caverns. The injection begins with highly responsive injection wells with a minimum injection pressure. As the gel-forming composition, a polymer composition with a crosslinker is used, for example:

1 composition: polyacrylamide 0.1-2.0%, chromium acetate 0.03-0.5%, the rest is water;

2 composition: polyacrylamide 0.05-1.0%, sodium carboxymethyl cellulose 0.05-1.5%, chromium acetate 0.03-0.5%, the rest is water;

3 composition: water-soluble polymer 0.1-2.0%, sodium hydroxide 1.0-5.0%, oligomer 2.0-90.0%, water the rest.

The gelling composition is injected into the formation while feeding the polymer in the form of a suspension and an aqueous solution of a crosslinker. The specified composition is injected with two rims, starting with a concentration of a water-soluble polymer in the first rim of 0.1-0.5 wt.%. The injection pressure is fixed by a pressure gauge installed at the wellhead. The change in pressure is determined in the range from initial to allowable pressure on the production casing. An increase in pressure indicates an increase in resistance to fluid movement in the formation. With an increase in injection pressure by 5-10%, the second rim is injected with a polymer concentration of 0.5-2.0 wt.%. The recommended injection of the rims of the gel-forming composition fills the cracks and caverns of the formation, eliminates the loss of time for gelation, forms a strong gel that does not deteriorate during prolonged mechanical stress, unlike brittle alkaline silicate gels, which decompose into sediment and water. For wells with an injection rate of at least 400 m ³ / day, the gelling composition additionally contains a filler in an amount of 5-30 wt.%, And as a filler, for example, breaker, or clay powder, or chalk, or wood flour. With an increase in injection pressure by 10-20%, the injection of a precipitating composition begins, using alkaline reagents or an alkaline-polymer composition in the presence of saline water with a density of 1.01-1.2 g / cm ³ . Recommended sediment-forming compositions in the range of interaction with the gel-forming composition additionally perform the function of a filler, contributing to the additional structuring and hardening of the gel. The sequential injection of gel-forming and sediment-forming compositions contributes to the formation of a fixing barrier at the boundary of the two compositions, increases adhesion to the rock of the carbonate formation. At the same time, this composition has oil-displacing properties while maintaining the permeability of low-permeability layers. The sediment-forming composition is pumped in a ratio to the gel-forming composition from 1: 1 to 1: 3 to increase the injection pressure by 30-90% depending on the permeability and porosity of the carbonate formation. Then these compositions are pressed into the formation with mineralized water with a density of 1.0-1.2 g / cm ³ in the amount of 1-3 volumes of the wellbore, after which technological exposure is carried out for 1-3 days, so that the fixing barrier is finally formed in the formation , and put the well into operation. As a result, the waterflood coverage increases and the oil recovery coefficient increases. Under control of the injection pressure, the injection composition is selected. The gel-forming and sediment-forming compositions proposed in this method of developing an oil deposit are distinguished by the simplicity of preparation, use, and availability. In field conditions, the method is implemented using the installation for the preparation, dosing and injection of technological solutions into the well.

As water-soluble polymers use:

- an aqueous solution of polyacrylamide (PAA), for example DP9-8177 of German production (MSDS No. 2848), as well as polyacrylamides of American, Japanese and domestic production;

- sodium carboxymethyl cellulose (CMC) - TU 2231-002-50277563-2000;

- polyethylene oxide with a molecular weight of (1.5-10) · 10 ⁶ .

As the oligomer use:

- acetone-formaldehyde resin brand ACF-75 according to TU 2228-006-48090685-2002, which is a homogeneous liquid from light to brown in color.

As an aqueous solution of a crosslinker, chromium acetate or sodium hydroxide is used (GOST 2263-79).

As alkaline reagents, sodium liquid glass is used, including according to GOST 13078-81, or water-soluble sodium silicate powder, for example, according to TU 2145-015-13002578-94, or aqueous solutions of sodium silicates, or spent caustic, or sodium hydroxide (GOST 2263-79).

As an alkaline-polymer composition, a composition is used including an alkaline reagent, a polymer and saline wastewater in the following ratio of components, wt.%: Alkaline reagent 0.5-1.5; polymer 0.01-1.0; the rest is water.

As mineralized wastewater use wastewater with a density of 1.01-1.2 g / cm ³ .

The analysis of the selected patent and scientific and technical information did not allow us to identify a technical solution similar to the one declared, which fulfills the task of increasing the oil recovery of the oil deposit, which meets the criteria of “novelty” and “inventive step”.

To determine the optimal concentration and sequence of pumping compositions, to evaluate the effectiveness of enhanced oil recovery in fractured and fissured cavernous water-saturated carbonate formations, laboratory tests were performed. Tests of the known and proposed methods were carried out on linear models filled with a sandy mixture simulating fracturing of a formation (50 cm long, 6.4 cm ² cross-sectional area). By selecting the size of the quartz sand grains, the necessary channel permeability of the formation model was created.

The studies were carried out in the following sequence:

- after evacuation, the model was successively saturated with mineralized water and oil from the Romashkinskoye field. Characteristics of the used oil: density 0.815-0.895 g / cm ³ , viscosity from 7 to 45 MPa · s. The following parameters were determined: pore volume, initial water saturation, water permeability and oil saturation;

- oil was displaced by mineralized water with a density of 1.0-1.2 g / cm ³ with measurement at the output of oil and water volumes. Primary water displacement was carried out to a total water cut of oil at a yield of 100%;

- the rims of the gel-forming composition (1 composition, or 2 composition, or 3 composition) and the sediment-forming composition in an amount equal to the volume of cracks and caverns were pumped sequentially into the model. The gelling composition was pumped while feeding the polymer as a suspension and an aqueous crosslinker solution. The ratio of sediment-forming composition and gel-forming was from 1: 1 to 1: 3. The injection pressure was recorded. Initial injection pressure of 0.05 MPa, allowable pressure of 0.2 MPa. The first rim of the gel-forming composition was pumped up to a pressure increase of 10% (to 0.065 MPa), the second - to a pressure increase of 20% (to 0.03 MPa), the sediment-forming composition was pumped to a pressure increase of 90% (to 0.135 MPa). Squeezed into the reservoir model with mineralized water with a density of 1.2 g / cm ³ . The model was kept for 1 to 3 days for complete gelation, formation of a barrier and completion of the process of adhesive interaction with the rock. At high permeability of the formation model, a filler was additionally introduced into the gelling composition;

- after which the oil was replaced by mineralized water by pumping water by measuring the output of oil and water.

Thus, we simulated the process of launching wells and oil production from the reservoir after the implementation of the proposed method.

The dynamic viscosity of the compositions was determined on a VPZh-2 capillary viscometer. The gelation time was determined by the time interval from the moment of mixing the components to the moment of loss of fluidity of the composition and the formation of the bulk structure of the gel. The structural and mechanical properties of the gels were evaluated by the shear strength of the gels at a shear rate of 1.4 s ^-1 , as measured by a RPE-1M polymer viscometer. The results of the gelation kinetics are presented in table 1.

From the presented results it is seen that the shear strength of the obtained gels from the initial viscosity of the composition increases by 20-75 times. The gelation time at the indicated concentrations of the composition is from 0.125 hours to 3 days, which makes it possible to pump compositions into the well quickly, thereby significantly reducing the cost of the process.

Adhesion characteristics were determined by the nature of fracture of the samples of the reservoir model. When the samples of the proposed compositions are destroyed, the structure of the crosslinked gel is preserved and remains firmly adhered to the reservoir model. The composition of the prototype does not form a connected structure with the reservoir model, which makes it possible to judge the increase in adhesion with the rock of the carbonate reservoir of the injected compositions.

As the oil displacing parameter, the oil displacement coefficient of a layered inhomogeneous porous medium was used after the primary displacement of oil by water and the final one after injection of the gel-forming and sediment-forming compositions.

The results of filtration studies are shown in table 2.

The analysis of the research results was carried out on the example of the main filtration parameter - residual resistance factor (OFS), which characterizes the filtration resistance during water filtration after injection of gel-forming and sediment-forming compositions in comparison with the initial filtration resistance during water filtration before injection of the composition.

As can be seen from table 2 OFS for the proposed development method for heterogeneous permeability of porous media increases 16 times in comparison with the prototype. The oil recovery factor is doubled.

Thus, the proposed method for developing an oil deposit allows increasing oil recovery by changing and leveling the filtration flows in fractured-cavernous water-saturated carbonate formations by increasing the residual resistance factor of the strength of the gel-forming layer, additional structuring of the fixing barrier, while maintaining the permeability of low-permeability layers. The method is simple to implement, technologically advanced due to the ability to control the process, can reduce material and labor costs, as well as reduce fire and explosion hazard.

Table 1 Gel-forming composition, wt.% Initial viscosity, MPa s Gelling time, days Shear strength, Pa Download sequence Water soluble polymer Stapler Filler Water PAA KMTS-1 Acetone-formaldehyde resin Chromium acetate Sodium hydroxide Slomel Clay powder one 0.5 - - 0.06 - - - 99.44 12.0 3 248 2 0.5 0.06 - - - 99.44 20,0 3 320 one 0.4 - - 0.06 - - - 99.54 18.0 2 420 2 1,0 0.06 - - - 98.94 25.0 2 510 one 0.1 - - 0.06 - 5,0 - 94.84 15.0 one 430 2 2.0 0.2 - 5,0 - 92.80 28.7 one 1800 one 0.3 - - 0.06 - - 5,0 94.64 18.0 3 480 2 0.5 0.06 - - 5,0 94.44 25.6 3 520 one 0.1 1,0 - 0.06 - - - 98.84 18.0 3 980 2 2.0 1,0 - 0.2 - - - 96.80 24.5 2.5 1670 one 0.4 1,0 - 0.06 - - - 98.54 11.0 3 1000 2 1,0 1,0 - 0.06 - - - 97.94 28.0 3 1800 one 0.3 1,0 - 0.06 - 5,0 - 93.64 18.9 1,5 1120 2 0.5 1,0 - 0.06 - 5,0 - 93.44 25.0 1,5 2000 one 0.5 1,0 - 0.06 - - 5,0 93.44 19.0 one 1150 2 0.5 1,0 - 0.06 - - 5,0 93.44 26.0 one 2100 one 0.1 - 2 - 2.0 - 5,0 90.9 8.0 0.25 260 2 2.0 2 2.0 94.0 12.0 0.21 980 one 0.4 - 5 - 2.0 - - 92.6 25.0 0.21 1050 2 1,0 5 2.0 92.0 28.0 0.15 1300 one 0.5 - 10 - 5,0 - - 84.5 25.0 0.15 1800 2 0.6 10 5,0 84,4 28.0 0.125 2100

table 2 No pp Pore volume, cm ³ The initial permeability to water, microns ² The initial oil saturation, cm ³ Development method The ratio of the compositions of sediment-forming: gel-forming The final permeability to water, μm ² The increase in oil recovery ratio,% Residual Resistance Factor, R _ost one 150 fifteen 90 Download 1 composition with conc. polymer 0.1% 1: 3 0.2 7.8 175.0 injection of 1 composition with conc. 0.5% polymer sodium hydroxide injection 2 150 fourteen 84 Download 1 composition with conc. polymer 0.35%, 1: 2 0.09 4.8 156.0 injection of 1 composition with conc. polymer 0.6%, injection of an alkaline polymer composition 3 150 fourteen 86 Download 1 composition with conc. polymer 0.4%, 1: 1 0.056 5.2 248 injection of 1 composition with conc. 1.5% polymer with filler liquid glass injection four 190 58 68 Download 2 composition with conc. 0.5% polymer 1: 3 0.11 5.95 527.0 injection of 2 compounds with conc. polymer 2.0%, injection of an alkaline polymer composition 5 150 0.61 94 Download 2 composition with conc. polymer 0.3%, 1: 2 0,099 7.5 635.0 injection of 2 compounds with conc. polymer 1.0%, liquid glass injection 6 150 15.0 80 Download 2 composition with conc. polymer 0.1% 1: 1 0.09 4.75 167.0 injection of 2 compounds with conc. polymer 0.6%, with filler sodium hydroxide injection 7 160 16 86 Download 3 composition with conc. polymer 0.1% 1: 3 0.14 6.3 489.0 injection of 3 compounds with conc. 0.5% polymer sodium hydroxide injection 8 150 14.0 84 Download 3 composition with conc. polymer 0.4%, 1: 2 0,03 7.3 750.0 injection of 3 compounds with conc. polymer 1.0%, injection of an alkaline polymer composition 9 150 5.8 90 Prototype upload - 3,5 3.3 45.6 10 153 14.0 82 Prototype upload - 6.7 3.9 10,2 eleven 186 52.1 67 Prototype upload - 33,4 2.5 30.1

Claims (5)

1. A method of developing an oil deposit, including sequential injection of gel-forming, sediment-forming compositions into the formation and forcing them into the formation, characterized in that the distribution of productive thicknesses of the formation over the area of the reservoir is clarified, injectivity of injection wells is determined, allowable pressure on the production string, injection begins with highly responsive injection wells, a polymer composition is injected as a gelling composition, the composition is injected with rims starting from polymer traction is 0.1-0.5 wt.% until the injection pressure is increased by 5-10%, the second rim is pumped at a polymer concentration of 0.5-2.0 wt.% until the injection pressure is increased by 10-20%, as sediment-forming composition using alkaline reagents or alkaline-polymer composition in the presence of saline water, the sediment-forming composition is pumped in ratio to the gel-forming composition from 1: 1 to 1: 3 to increase the injection pressure by 30-90%, then squeezed into the reservoir with mineralized water with a density of 1, 0-1.2 g / cm ³ in an amount of 1-3 volume barrel kvazhiny, then produce technological held for 1-3 days. 2. The method according to claim 1, characterized in that for highly-responsive wells, a filler in an amount of 5-30 wt.% Is additionally added to the gel-forming composition, and, for example, breaker or clay powder, or chalk, or wood flour are used as filler. 3. The method according to claim 1, characterized in that the injection of the gelling composition into the formation is carried out while feeding the polymer in the form of a suspension and an aqueous solution of a crosslinker. 4. The method according to claim 1, characterized in that for the injection of sediment-forming composition using saline wastewater with a density of 1.01-1.2 g / cm ³ . 5. The method according to claim 1, characterized in that the gel-forming and sediment-forming compositions are pumped in a volume equal to the volume of cracks and caverns.