RU2140531C1 - Method of treating bottom zone of oil formation - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: invention relates to wells employing terrigenous low-permeable formations or impairing its running characteristics because of pollution in vicinity of hole. Bottom zone of oil formation with low- and high-permeable reservoirs is treated by injecting chemical reagents with different functionality and depressive effect to achieve hydrodynamic superperfection of wells increasing their productivity. Treatment of bottom zone is accomplished in cyclic action mode including injection of reagents into productive formation zone, process ageing, and return of depleted reagent under depression conditions. After that, acid or acid plus surfactant or demulsifier and organic solvent, or organic solvent plus surfactant or demulsifier are pumped into productive formation zone. Chemical reagents are injected into formation in order, combinations, and volumes determined by conditions of well until filtration resistances in the remote formation zone become superior to those in bottom zone. Process ageing and return of depleted solution are also effected after organic solvent is injected. EFFECT: enhanced bottom zone treatment efficiency. 2 cl, 1 tbl

Description

 The invention relates to the oil industry, and in particular to methods for treating the bottom-hole zone to increase production productivity and injectivity of injection wells exploiting terrigenous low-permeability formations or worsening their performance due to contamination of the borehole zone and well development.

 In conditions of low-permeability formations, the productivity (injectivity) of the wells does not correspond to the hydrodynamic parameters of the formation (its remote part is implied) due to a sharp increase in the filtration resistance of the bottom-hole formation zone (PZP) in the mode of radial fluid filtration.

 The decline in the productivity of wells with highly permeable reservoirs is associated with a deterioration in the hydrodynamic characteristics of the BFZ due to a decrease in the permeability of the near-wellbore zone of the reservoir caused by technological factors. The main reasons for this are contamination of the near-bottom part of the bottomhole formation zone with dispersed components of the drilling fluid and process fluids during the opening of the formation and development of the well, compaction of the rocks in the bottom-hole zone due to hydraulic action, swelling of the clay cement of the reservoir rock, increasing the water saturation of the reservoir and reducing the phase permeability of oil, precipitation salts and asphaltene-resin-paraffin deposits (AFS).

 Various methods are used to increase or restore the permeability of respectively low and high permeability formations. The most common are the physicochemical methods for treating the bottom-hole zone (BHP) using various acid compositions and solvents (G.Z. Ibragimov, K. S. Fazlutdinov, N. I. Khisamutdinov "The use of chemical reagents for the intensification of oil production", M. , Nedra, 1991, p. 22 - 38). However, their effectiveness is low due to the insufficient degree of impact on the PPP due to the use of small volumes of chemicals.

 There is a known method of SCR with the help of depressive effects on PZP (RS Yaremiichuk, Yu. D. Kachmar "Opening of productive horizons and development of wells", Lviv, Higher School, 1982, 152 S.). The method is also not effective enough due to the fact that it does not allow to completely clean the PZP of particles of destroyed rock, contaminants, especially agglomerated and having large sizes exceeding the size of pore channels.

 A known method of SCR using physico-chemical exposure, in which the volume of the reagent used, therefore the depth of processing, is calculated based on the assessment of the filtration characteristics of the reservoir ("Guide to the application of systemic technology of impact on oil reservoirs of Glavtyumenneftegaz fields", RD 39-0147035-254-88r , VNIIneft, SibNIIIP). It is also not effective enough due to the fact that the method uses a reagent of only one functional purpose. This does not ensure the removal of all types of contaminants and particles of the destroyed rock from the bottomhole formation zone and thus does not significantly increase the permeability of the formation.

 The closest analogue of the invention to the proposed invention is a method of treating the bottom-hole zone of an oil reservoir by cyclic treatment, including pumping acid into the zone of the reservoir, holding the process and extracting the spent solution by creating a depression in the well (see, for example, “Instructions for developing wells by creating controlled cyclic depressions on the reservoir using jet pumps ", RD 39-2-1306-86. M., Ministry of Petroleum Industry, 1985). The known method is not effective enough due to the small amount of acid composition used and the monofunctionality of the chemical used, which does not provide sufficient depth and completeness of the processing of PPP.

 The technical result of the invention is the creation of a highly efficient method for treating the bottom-hole zone of an oil reservoir with low- or high-permeability reservoirs, which allows to achieve hydrodynamic super-perfection of the well by combining the injection of a chemical agent of various functions with a depressive effect, which makes it possible to increase its productivity.

 At the same time, under the hydrodynamic super-perfection of the well is meant the excess of filtration resistances in the formation zone remote from the well over those in the bottomhole zone.

 The required technical result is achieved by the fact that in the method for treating the bottom-hole zone of an oil reservoir with cyclic action, including injecting acid into the zone of the reservoir, holding the process and extracting the spent solution by creating a depression in the well, according to the invention, acid or acid is pumped from the surface active substance or demulsifier, while chemicals are pumped into the reservoir in the order, combinations and volumes determined by the state of the well and until the filtering resistances in the formation zone remote from the well are higher than those in its bottom-hole zone, and the technological exposure and extraction of the spent solution by depression is carried out after the injection of the organic solvent.

 In addition, a proppant and / or water repellent is additionally pumped into the zone of the reservoir.

 The problem is solved by creating a method for treating the bottom-hole zone of an oil reservoir with a cyclic action, including pumping a chemical into the zone of a productive formation, carrying out technological exposure and extracting the spent chemical by creating depression, the effect being carried out using chemicals of various functional purpose until the hydrodynamic super-perfection of the well is achieved. As chemical reagents of various functionalities, acidic compositions, organic solvents, claying reagents based on inorganic salts, water-based cationic surfactants and surfactants and demulsifiers are used.

To perform the technology, for example, the following acids can be used:
- hydrochloric acid, inhibited according to TU 2122-131-05807960-97, TU 6-01-714-87, TU 6-01-04689381-85-92, TU 39-05765670-OP-212-95;
- hydrofluoric acid (hydrofluoric) in accordance with GOST 2567-89, TU 6-09-2622-88, TU 113-08-523-82, TU 6-08-397-77;
- an inhibited mixture of hydrochloric and hydrofluoric acids according to TU 6-01-14-78-91, TU 113-08-523-82;
- a mixture of acids: technical hydrofluoric acid - waste production of phosphate fertilizers, hydrogen fluoride and chladone according to TU 113-08-555-84 and hydrochloric acid, inhibited according to TU 6-01-04689381-85-92, in a volume ratio of 1: 1.

 Acidic compositions according to reactivity are divided into compositions of hard and moderate action. The hard-acting acid composition contains hydrochloric and hydrofluoric acids with a concentration of 17–22 and 2–5%, respectively, by weight. The moderate acid composition contains hydrochloric and hydrofluoric acids with a concentration of 12-22 and 2-5%, respectively, by weight, and a surfactant or demulsifier in an amount of 0.05-2.0% (by weight). A moderate acid composition is necessarily pushed deep into the reservoir with fresh or industrial water (water for flooding oil reservoirs according to OST 39-225-88) with a volume of 1 - 2.5 volumes of acid composition. Concentrations of acids in acid compositions are selected based on the material and mineralogical compositions of the reservoir rock. Injection of an acid solution helps dissolve and disperse the silicate, carbonate and clay constituents of the rock.

In technology, as organic solvents can be used, for example:
- hydrocarbon solvents such as hexane fraction according to TU 38-10388-93, "Wide fraction of light hydrocarbons" (BFLH) according to TU 38-101524-83. "Straight-run gasoline fraction" according to TU 38.601-09-166-91, distillate and condensate - products of primary oil refining at UKPN of oil fields;
- alcohol solvents, such as bottoms from the production of butyl alcohols according to TU 38.1021167-85, flotation reagent - oxal according to TU 2452-029-05766801-94, spent solvent from the production of TPM-2 polymer according to TU 38.303-04-25-94, liquid pyrolysis products according to TU 10285-83, methanol fraction according to STP 145-95 (Khimprom OJSC), head fraction of butyl alcohol production according to TU 39-9794688-002-89, pyran fraction according to TU 38.602-09-13-90;
aromatic solvents such as Nefras-A-120/1200 according to TU 38.101809-90, Nefras C4-155 / 200 according to GOST 3134-78, solvent - oil solvent according to TU 38.1014049-87E, butylbenzene fraction according to TU 38.10297-78.

 Surfactants or demulsifiers in amounts of 0.05-0.5% (by weight) can be added to organic solvents.

 The introduction of an organic solvent helps to remove film oil and paraffin deposits, the presence of which in the PPP reduces the permeability of this oil, complicates the subsequent acid treatments to destroy mineral contaminants and affect the rock structure.

 As the wining reagents, for example, sodium bisulfate according to GOST 6053-77, or soda ash according to GOST 5100-85E, or sodium hydrosulfite according to GOST 246-67, or ammonium chloride according to GOST 2210-51 can be used.

 The wedging reagents in the PPP are pumped in the form of aqueous solutions with a concentration of 8-12% (by weight).

 Claying reagents contribute to the dispersion and, in part, structural destruction of the clay component of the rock and clay introduced into the bottomhole formation zone when drilling a well.

 As a water repellent agent, for example, cationic surfactants can be used, such as Catapin AB according to TU 6-01-816-75, Katapin according to TU 6-01-816-75, Don-52 according to TU 2484-006-04706205-93, IVV-1 according to TU 6-01-407-89.

 Water repellents in PZP are pumped in the form of aqueous solutions of concentrations of 0.2 - 3.0% (by weight).

 Water repellents are used in conditions of oil-unsaturated formations, i.e., in the presence of loosely bound water. Water repellents contribute to improving the phase permeability of the bottomhole formation zone for oil, thereby significantly reducing hydraulic losses in this zone.

As surfactants can be used, for example, AF Neonol ₉ TU 38.507-63-171-91 -12, -6 ₉ Neonol AF, AF ₉ -4 TU 38.50724-87, sulfanol NP TU-3 84-509- 81.

 As a demulsifier, for example, water-soluble Diproxamine 157-65M according to TU 38.1011128-87, Reapon-4V according to TU 2226-005-10488057-94, other domestic and foreign analogues (Disolvan, Separol and others) that are most effectively used can be used. for the destruction of oil-water emulsions in the preparation of oil of a specific oil field facility (fields). As an oil-soluble demulsifier, for example, SNPCH-4480 according to TU 39-05765670-00-220-96, etc. is used. An oil-soluble demulsifier is added to hydrocarbon and aromatic solvents.

 The use of surfactants and demulsifiers helps to improve the conditions for injecting reagents into the formation and easier removal of spent reaction products and formation contaminants.

где χ₁, χ₂ - соответственно пьезопроводность пласта, определяемая по начальному и конечному участкам КВД (КПД), см²/с;
T₁ - время, соответствующее точке перегиба КВД (КПД), с;
T₂ - время полного восстановления давления, с.The volumes of injected reagents of various functionalities are determined based on the radii of the processed zones, determined on the basis of data obtained as a result of hydrodynamic studies. By interpreting hydrodynamic studies data (HPC-curve pressure recovery for extracting and efficiency curve of the pressure drop for injection wells) define radii altered permeability (P _n, cm) in PPP and radius active drainage (P _a, cm) reservoir by the following formulas:

where χ ₁ , χ ₂ - respectively, the piezoelectric conductivity of the reservoir, determined by the initial and final sections of the HPC (COP), cm ² / s;
T ₁ - time corresponding to the inflection point of the HPC (efficiency), s;
T ₂ is the time of full pressure recovery, s.

где P_x - значения P_п или P_а, определяемые по формулам 1, 2, м;
m - коэффициент пористости, доля единицы;
h - эффективная работающая толщина пласта, определяемая по данным промысловых геофизических исследований, м.The volume of injection of chemicals (V, m ³ ) is determined by the formula

where P _x - the values of P _p or P _a determined by the formulas 1, 2, m;
m - coefficient of porosity, fraction of unit;
h is the effective working thickness of the reservoir, determined according to the data of field geophysical studies, m

For calculation of the volume of the acid composition of the hard actions organic solvent razglinizatora taking values P _n, and for calculating the volume of the acid composition mild action, including the amount of water to push deeper into the formation, taking the value P _a, and _the true scope of the acid composition moderate action is 0, 3 - 0.5 of the calculated value.

 For depressive effects use jet (ejection) pumps brands UOS-1, UEOS, NSS, UGIP, etc. For depressive effects, methods of swabbing, lowering the level of fluid in the well, compression using inert gases, replacing the wellbore fluid with valuable systems, and other technological methods used in oilfield practice can be used.

The method is as follows:
A tubing string (tubing), arranged by a jet pump, a packer and a downhole filter installed at the calculated depths, is lowered into the well. (In the case of using the swabbing method for the depressive effect, the tubing string is lowered from the template pipes and the packer into the well, and when creating depression by compression, two mandrels or bypass valves are installed at the calculated depths). Using pumping units, the calculated volume of the organic solvent is added to the formation with the addition of a surfactant or demulsifier with fresh or industrial water or oil. After exposure for 12 hours using a jet pump or the above methods, a depressive effect is applied to the formation to extract the entire volume of spent solvent and reaction products. Then, hydrochloric acid with a concentration of 22-24% (by weight) is successively squeezed with fresh or technical water into the formation with the addition of a surfactant or demulsifier in a volume calculated on the basis of a flow rate of 0.5 m ³ per meter of effective working thickness of the formation, the acid composition of hard action in estimated volume.

 After holding the reaction for 6 to 12 hours, a depressive effect is carried out to extract the entire volume of spent hydrochloric acid and acid composition, reaction products and contaminants from the formation. Then, the calculated volume of the proppant with the addition of a surfactant or demulsifier and fresh or industrial water is forced through the formation. After exposure to the reaction for 6 to 8 hours, a depressive effect is carried out to extract the spent reagent and reaction products, dispersed clay particles. Then, the calculated volumes of moderate acid composition with the addition of a surfactant or demulsifier and fresh or industrial water are successively pushed into the reservoir. Selling is carried out with fresh or industrial water. After exposure to the reaction for 2 hours, a depressive effect is performed to extract from the formation the entire volume of the spent acid composition, including water crushed into the formation, and reaction products. Then, the calculated volume of the aqueous solution of the hydrophobizer with fresh or industrial water is pushed into the reservoir. After exposure for 6 to 8 hours, a depressive effect is performed to extract the entire volume of the spent water repellent. After that, field geophysical studies of the well are carried out, its productivity is determined, the corresponding pump is lowered into the well (with the exception of the cases when the wells enter the gushing mode after processing) and put into operation.

 The sequence of technological operations for the injection of chemicals of different functionalities may be different and from technological operations, crushing in the PPP of a decontaminator and / or water repellent may be excluded. The specific sequence of chemicals used is determined by the diagnosis of the condition of the bottomhole formation zone based on the geological and physical characteristics of the formation, its material and mineralogical composition and the history of the well.

 A new set of claimed essential features allows to obtain a new technical result, namely due to the targeted chemical exposure to chemicals of various functionalities with subsequent depressive effects to extract the reaction products to more effectively treat the bottom-hole formation zone until the hydrodynamic super-perfection of the well is achieved.

 An analysis of the well-known solutions selected in the search process showed that in science and technology there is no object similar to the claimed combination of essential features and having high rates when processing PPP.

 We give a specific industrial example of the method of processing the bottom-hole zone of the oil reservoir.

 Example 1

The method is implemented on an existing producing well 2086 operating a layer of BS _{18-20 of the} Bystrinskoye field. The effective working layer thickness is 3.4 m. The layer is low permeable. The well is operated with SHGN. Liquid flow rate of the well is 8.0 tons / day, water cut is 56.8%.

 A tubing string is lowered into the well, assembled by a UOS-1 jet pump, a packer and a downhole filter with the column shoe installed in the middle of the perforation interval.

Using pumping units, 10 m ^{3 of} NGL organic solvent is crushed into the reservoir. After technological exposure to the reaction for 12 hours, a cyclic depressive effect (12 cycles) is carried out and 10 m ^{3 of} spent BFLH with dispersed and dissolved ASPO components are extracted from the reservoir. The buffer layer sequentially crush of 3.5 m ³ of hydrochloric acid of 24% concentration (by weight) supplemented with Neonol AF ₉ -12 with 0.5% (by weight), and 6.5 ^m3 of acid composition with a content of 22% ( by weight) hydrochloric acid and 3% (by weight) hydrofluoric acid. Spend technological exposure to the reaction for 12 hours. Carry out a depressive effect and extract 10 m ^{3 of} spent reagents with reaction products. Their analysis showed the absence of clay components. The layer sequentially crush 18 ^m3 of acid composition with a content of 22% (by weight) hydrochloric acid and 3% (by weight) of hydrofluoric kisot, 0.7% (by weight) Neonol AF ₉ -12 and 36 m ³ of industrial water. Carry out technological exposure for 2 hours. By depressive action, 54 m ^{3 of} spent reagent with water and reaction products are extracted from the formation. At the end of the depressive effect, the well entered the gushing mode. A well is put into operation in a fountain way. Liquid flow rate was 48.6 m ³ / day, water cut 51.3%.

 Examples 2 to 12.

Accordingly, implemented at wells 3118, 3129, 3117 of the Bystrinskoye field, BS 18-20 formation; 5612, 1480, 24401 of the Romashkinskoye field, reservoir D ₁ , 5417 of the Yuzhno-Yagunskoye field, reservoir YUS-1; 73, 56 of the Maslikhovsky field, 12915 ^a , 24401 of the Romashkinskoye field, reservoir D ₁ , 3061 (prototype) of the Bystrinskoye field, BS-18-20 layer. The treatment is carried out similarly to that described in example 1, changing according to the claims used chemicals. The geological and field characteristics of the wells, the main technological parameters of the treatments in Examples 1-12 and their effectiveness (productivity coefficients) are presented in the table.

 From the data presented in the table it can be seen that the use of the claimed method allows to achieve hydrodynamic super-perfection of the well, providing a multiple increase in its productivity.

Claims (2)

 1. The method of processing the bottom-hole zone of the oil formation by cyclic action, including pumping acid through the well in the zone of the productive formation, conducting technological exposure and extracting the spent solution by creating depression in the well, characterized in that acid or surface-active acid is pumped into the zone of the producing formation a substance or demulsifier and an organic solvent, or an organic solvent with a surfactant or demulsifier, while the chemicals are pumped formation in order combinations and quantities defining the state of a well bottom zone and before filtration resistance in excess remote from the well above a formation zone established in its bottom zone, and the process speed and extracting spent liquor depression is performed and after the injection of the organic solvent.  2. The method according to p. 1, characterized in that in the area of the reservoir additionally pumped out the clay and / or water repellent.

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