CA2450399A1 - Method of and system for increasing productivity of oil, gas and hydrogeological wells - Google Patents

Abstract

A method and a system for of increasing the productivity of oil, gas and hydrogeological wells includes cutting slots only in a near well zone so as to perform a partial unloading of the well and to remove a part of support stresses; and cyclically treating well with a formation-treating substance so as to remove a remaining part of the support stresses, with controlling a density of a formation and correcting the cyclical treatment in correspondence with the density of the formation.

Description

Method of and System for Increasinct Praductivit~of Oil. Gas and Hydrogeologiical Wells Technical Field The present invention relates to oil and gas industry. It involves a new abrasive hydrojet perforation which offers an effective means to communicate the wel~bore with the target formation and to achieve more effective completion due to an increase of flow area, I~ypassing the damage in a near-wellbore zone and reduction of the compressive stresses. The invention represents a new method of and a new system for treatment of a near-well zone of producing formation with a combination of chemical treatment.
Background Art It is known that the flow from productive zones can be increased by slotting and chemical treatment. Slotting allows redistribution of the mechanical stresses in the near well zone, while chemical treatment allows increased productivity of the wells. However,'the fiPSt method is very labor consuming and requires high costs. In order to shot three feet of the productive interval some time it is necessary to spend up to three hours of ..
pumping unit operation, which is an expensive operation. The chemical action also treats the near well zone, but it requires a primary opening of the formation and does not remove a zone of support pressure which is a main reason of locking of the passages for fluid flow into the well. T he first method is very efficient and increases the productivity of wells on average several times, however it is expensive. In order to provide maximum effectiveness or completely restore the potential productivity of wells, it is usually necessary to provide a subsequent treatment with formation treating reagents.

The method disclosed in SU116792a is the closest to the present invention. It is a combined method for the increase of productivity, which includes slotting of the welt and cyclic acid formation treatment. The slotting is performed in accordance with known "classic" recommendations in order to obtain a maximum possible effect, while the cyclic acid treatment is performed also in accordance with the known method described in the above mentioned documents, for a depth which is not less than ~ diameters of the wets, so as to attempt to completely use its possibilities without the consideration of the results of slotting or control of the results of each cycle.
The cyclical "periodic" treatment of a well was performed by a reagent solution whose volume was determined from a mass and porosity of rock adjoining a shaft of the well, at a distance of approximately two diameters from the well. Each cycle of treatment is performed by pressing of a calculated volume of solution into the formation to tae treated, which. is preliminarily limited from above and from below by packers. The treatment in some ~ense.is performed blindly, the results were evaluated in accordance with a change of productivity of the well. The cycles of treatment continued until the time when repetition did not lead to a change in productivity.
it has been shown from practice that this method which Includes a complete slotting with a subsequent complete treatment with technological reagents has a universal action of the formation and provides an increase of well productivity, an equalization of a profrle of advancement of a front of water pumped into a formation for maintaining of the formation pressure, a increase of the oil yield of the formation. Because of these advantages this method has been widely utilized. It also has been used during exploration and drilling of new welts. Monrover, it was made possible with this method to explore and efficiently use wells in low-production formations of Western Siberia in which the oil flow is less than 30 bbl per day. This method therefore is efficien#. However, this method, similarly to _3_ the other methods has a limitation as to its possibility and efficiency. !t is expensive, labor consuming and does not guarantee obtaining of the maximum possible increase of well productivity. The method is used without consideration of negative action of elevated stress concentrations, which are formed near the wellbare. ' It is known thatthe maximum stresses in the nearwell zone are generated within one diameter of the well or approximately 0.6 ft., and the maximum stress directly adjoins the wails of the well (Fig. 1 ). The plastic zone in this case can be not considered, since in accordance with the calculation its width at the depth of # 0,000 ft. is only 0.08 ft.. It is also known that during the process of drilling of wells, even after canying out of slot slotting, a zone of support pressure remains near it. The slot removes only a part of these stresses, which is equivalent to a reduction of depth of the well approximately 1.5 times. During slotting at the depth of 10,000 ft. it is equivalent to a reduction of stresses to the depth of B,600 ft.. However, the .:
made arid parameters of acid treatment (or treatment with other reagents, such as technological compositions) nowadays are detem~ined without consideration of negative influence of the remaining stresses near the well.
The zone of support pressure, which remains around the welt, is not taken into consideration and parameters of treatment with technological compositions are calculated from the condition of action of a uniform supply ' of active technological solution per volume unit of a formation.
However, experimental observations and analytical i nvestigations showed that the influence of zone of support pressure nearthe well is significant. If this influence is i~ot taken into consideration, false conclusions can be made with respect to the productivity of the wails. Based on the results of the treatment, it is considered that a low c~ii yield from a formation can be explained by a week natural permeability of the formation itself, while a real cause is the reduction of permeability only within limits of the zone of support stresses, caused by stress concentration beyond the wellbone.
D~closure of the Invention Accordingly, it is an object of the present invention to provide a method -and a system formed so as to reduce labor consumption and cost of treatment of a well, without a reduction of ef~eiency of treatment, time of use of wells, and gasloil yield of productive formations.
. In keeping with these objects and with others which wilt become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of increasing the productivity of ail, gas and hydrogeological wells, comprising the steps of cutting slats only in a near well zone so as.
tn perform a partial unloading of the well and to remove a part of support stresses~and cyclically treating,well with a inrmation treating substance so as to reinave a remaining part of the support stresses, with controlling a density of a formation and correcting the cyclical treatment in correspondence with the density of the formation.
Another feature of the invention resides in a system for increasing the productivity of oil, gas and hydrogeolo~ica( wells, comprising means for cutting slots only in a near well zone so as to perform a partial unloading of the well and to remove a part at support stresses; arid means for cyclicatlytreating well with a formation-treating substance so as to remove a remaining part of the support stresses, with controlling a density of a .
fom~ation and correcting the cyclical treatment in correspondence with the density of the formation.

When the method is performed and the system is designed in accordance with the invention it provides the following benefits:
The inventive slotting provides a very precise, reliable and controllable method to establish a large inflow path between the cased borehole and the formation. The inflow area of an 8-in per foot dual slot is equivalent to 36 spf of 0.'~5-in shaped charge holes. IVloreaver, the pressure drop on the slot is significantly less then on the aroal equivalent set of perforated holes. In addition, the cutting process is much more robust in creating a low-resistant flow path, even with two strings of casing.
The slotting preserves the integrity of the cement bond. This can be critical for tonal isolation when the perforated intervals are in close proximity to water or a gas cap. The integrity of the cement sheath also increases the casing strength and resistance to failure.
The created slots simplify the fracture initiation and therefore may significantly reduce the near wellbore problems {multiple fracturing, tortuosity, etc). This reduces the chances of screenouts during fracture stimulation and minimizes the choking non-darcy effect because of the tortuous path during production (esp., in gas wells).
The slot geometry {with the penetration depth up to 4-90 ft) bypasses the near wellbore mud invasion zone and increases the drainage area. This suggests that the inventive slotting in clean, high permeability sands is the preferced completion method. if these clean formations require .
sand control, slotting can be used in combination with high rate water packs.
For laminated formations, slots in should result in the consistent negative skin cornpletions.

The cutting does not reduce the near wel)bore strength of the formation, as does conventional shape charge perforating. Under some circumstances, this feature in combination with a larger created drainage area may allow a natural completion of formations that currently require sand control.
The slots modify the stresses in near the wellbore zone (relaxed in zone adjacent to the slots, and increased at the tip zone).
Formations with strong stress-dependant permeability may encounters significantly reduced completion sEdn moreover, for deep and relatively hard formations. Staffing may achieve compressive fracturing in the nearwellbore region that results in a significant permeability incn3ase at a distance of several slot diameters and dramatic reduction of the near well bore conversion pressure drop. In gas wells it will reduce (orcompletely eliminate) sometimes very large non-darcy skin.
_ ~ ....
fn order to optimize the mefhod and the system, the partial abrasive hydrojet perforation is performed bye cutting slots only in surrounding column, cement layer and a part of the productive zone of the formation.
This method allows cutting slots in a thin productive zone and in the case when the productive layer is notfar awayfrom thewater horizons.
Abrasive hydrojet perforation is preformed by fluids, which includes water and quartz sand. This allows preserving the integrity of the cement and leads toward h6gher penetration into the formation compared to other systems and .
methods (conventional perforation, hydrafracturing).
The technology can be divided into sun'ace and underground equipment. Underground equipment includes an engine with nozzles, which is connected.to surface pumping units. For abrasive hydrajet perforation, hydrojet perforators are used; for single slotting the perforator is used with 4 nozzles. Nozzles are located 180 degrees across from each other. The distance between nozzles is around 4". The abrasive fluid is recycled all the time during the process in addition underground equipment includes:
underground engine switch and hydrojet perforator. This equipment can slot in one session three intervals with the approximate length of 3 ft each. After that pertorators must be changed description of the slotting technique is shown on.
Surface equipment includes pumping units, mixer blender of sandlwater, block manifold, filters and connectors. Pumping units for abrasive hydrojet perforation can be used with the following characteristic 5,000-10,000 psi, depending on well depth and continuous working capacity of 6 hours.
.... ~ .
- Abrasive ~uids are prepared in blender. Filter are used to flter fluids and separate waterforthe recycling process quartz sand can be used as the abrasive material with the quartz consumption not less then 50%.
During the abrasive hydrojet perforation it is preferable preliminarily to determine the porosity and permeability of the production '.
formation of the near welibore zone, and the depth of the zone of support stresses, and td perform the subsequenttreatment in the dependence of the porosity and depth.
In particular when the rock has a porosity of the approximately 15% and higher, the abrasive hydrojet perforation is performed at the depth of 1-1.5 welt diameters, with the porosity of less than approximately 15% the _8..
abrasive hydrojet perforation is performed at the depth not less than four wail diameters.
in the first case it guarantees achieving of the maximum possible effect. Moreover, during a subsequent cyclic treatment with technological reagents in order to increase permeabifi#y of the zone of suppork pressure and a maximum acting stress in it are determined and the treatment is performed on a part of the formation witch adjoins the well, including a zone of the support pressure after each cycle of treatment, a change of density (permeability) of the formation in the zone of support . pressure is controlled.
In order to optimize the method and the system, the treatment is stopped when the density of the formation in the zone of support pressure is reduced by a predetermined value, which is determined in accordarace with the form~fa: , L~pZkp(~y- HOE, wherein K is a factor of ef8aency of treatment, p is the density of the formation of a not disturbed formation at the depth, lblft a is the maximum stress acting in the zone of support pressure Mpa, y is the specific weight of rock of the formation, Iblft3, E is an elasticity modules of fiomlation rock, Mpa.
It is also proposed in accordance with the present invention to use a technological solution with an acid of flow, which interacts with a clay component for oolmatating portions and a matrix of rock of a productive formation, whose composition is selected in accordance with the nature of the rock of the productive formation of a near well zone.
In particular, with a terrigen collector of the productive formation, the technological solution is a solution of NaHSO 4xH~ andJor K2S2O, and/or (NH)4S70$ with concentration 4-7%, with .additions of anion active surface active substances or mixture of anion active and noiogenic surface active substances within the concentrations 0.5-2'Yo.
If in a terrigen collector, there is a carbonate component more than 30% and if there is a carbonated collector of the productive formation, the technological solution can be a solution of NH 2S04H with addition of anion active surtace active substances or a mixture of anion active and non ionogenic surtace active substances within the concentrations 02-04°~6 and polyphosphates within the concentration 0.1-0.2 % or a solution of CH3COCl with cc~r~ntration 0-12°,~ with admixtures of anion active surface acfrve substances or a mixture of anion active and non ionogenic surface active substances within the concentration 0.5-9 % or polyphosphates within the concentrations of 0.1-0.2% and as polyphosphates, there are used in NaSP~O,o and/or Na2[Na4(P03~].
In accordance with a further advantageous feature of the present invention, the formation treatment fluid (technological solution) is formed directly in a well within an interval of a formation to be treated, for example by enclosing of chemical agents for preparation of a solution into a transport package, transporting the package to the formation to be treated, and then removing the package for example by its dissolution with a solution in the wall or by supplying of a dissolving liquid.

-1 ~-The transporting package can be formed as a micro container or capsule with a dissolvable enclosure formed, for example as a water soluble polyethylene film. The container can tae also composed of a binding material, for example starch which is water soluble without the residues and consequences. Containers can be formed as balls or cylinders.
Thus, the new features of the present invention include a combination of operations, such as performance of the method in two stages with a primary controlled partial Abrasive Hydrojet Perforation and a subsequent controlled and regulated cyclical treatment of a well with a formation-treating agent, cutting of slots only in a surrounding column, a cement layer and a part of the rock of the collector immediately adjoining the well, preliminary determination of porosity of the rocks of the productive formation of the near well zone and a depth of a zone of support stress, and correction of a further treatment depending on the porosity and depth, determir~tion of a radius of zone of support pressure and a maximum acting .._ stress iri ~it before each cycle of the formation treatment, carrying out of the _ treatment of alt parts of the adjoining formation to the well including a zone of the support pressure, controlling of a change of denshy (permeability, porosity) of rocks in the zone of support pressure after each treatment, stopping of the cyclical treatment when density of the formation in the zone of support pressure is reduced by a predetermined value, change of volumes (radii) of a mass which is treated in stages, selection of compositions of technological solutions and their preparation direc~y in a well in an interval of a treating formation. These features provide an unexpected result, which is a significant reduction of labor consumption and cost of the method without .
a reduction of efficiettcy of treatment and long-term stabilization of the obtained effects. These results are unobviaus and inventive.

Tile r<ovel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from thefotlowing description ofspecificembodiments when read in connection with the accompanying drawings.
Brief Description of the Drawings Figure 1 illustrates a in abrasive hydrojet slotting perforation Figure 2 shows a surface equipment used for abrasive hydrojet slotting perforation Figure 3 shows an underground equipment used for abrasive hydrojet slotting perforation;
figure 4 shows an inventive method of increasing productivity of wens; ~ ..
' Figure 5, 6 7 are views showing a distribution of stresses in a near well zone before thp beginning of a cycttcal treatment, after a first cycle of treatment, and after the end of treatment correspondingly.
(n the drawings the following symbols are utilized:
aXay are a vertical and a horizontal stress, ay, is a remaining maximum stress in a zone of support stresses before a beginning of a formation treatment rafter a partial slot abrasive hydrojet perforation), aye is a remaining maximum stress in a zone of support of stresses after a first cycle of formation treatment, yH is a remaining maximum stress in a zone of support stresses after the end of formation treatment, -iz-r, is a radius zone of remaining support.stresses before the beginning of formation treatment (after a partial abrasive hydrojet perforation), r2 is a radius of a zone of remaining support stresses after a first cycle of formation treatment, r$ is a radius of zone of reduced support stresses around the welt after a first cycle of formation treatment.
BB~s~ Mode of Cling taut the invention it is known that a maximum stress in a near welibore zone within one diameter of a well shown in Figure 1 is approximately 0.6 ft. The . maximum stresses directly adjoin the waifs of the well. In the present invention it is permissible not to consider a plastic zone, since in accordance with calculations its width on the depth of 10,400 ft is only p.4".
it is therefore proposedto reduce and redistributs#he maximum stressesithout a complete cutting of an unloading slot. This significantly accelerates and reduces the cost of the method. Then it is suggested to remove the remaining part of stresses in the zone of support pressure with another method (formation treatment)with labor consumption which is lower than usual. As a result, a desired corrtdorfor movement of useful fluids into the well is formed in a reliable and less labor consuming method.
The corresponding operations indudethefoilowing sequence.
Before the .beginning of works, porosity and density of a format'ron is evaluated by .a geophysical methods. For example the porosity .
is determined by a neutron logging, while density is determined in accordance with a density logging. If the porosity is higher than approximately 15%, the speed of movement of a perforator is selected to be 1.5 hours for 3 ft, instead of the conventional three hours for 3 ft. In this case, a surrounding pipe, cement and a main part of the area of increased stresses will be cut through, and directions for pumping of a formation treatment solution are created. The solution, in addition to a conventional dissolution of cementing substance of the productive formation, performs pressurization of rock of the productive formations and therefore increases support stresses.
if porosity of rock is less than 15°h, the abrasive hydrojet perforation is performed in accordance with the traditional method, with a speed of cutting of the slot about three hours for 3 ft. After this, because of the formation of a great draining surface a more reliable depressurization of rock in the zone of support pressure is performed, and a maximum reduction of stresses in the nearweA zone is obtained. .
The formation treating agent can be for example a solution of . hydrochi~ric acid {for carbonate rock and for terrigen rock with a signifrcant content of carbonate cement).
initially, the remaining stress-deformed condition of~rock in the near welt zone is evaluated, and based on it, a pattern of distribution of support stresses is determined as represented by a curve 'I in Figure 5.
The stress condition is evaluated by experimental methods. In wells which do not have surrounding tubes, it is necessary to use electrometric and ultrasound methods. !n w~lls which are provided with surrounding tubes, it is possible to use a method of radioactive {density and .
neutron) logging. It is also possible to use analytical methods for the calculation of parameters of the zone of support pressure.

-1~-Based on the evaluation of stress condition, a zone of support toads and a compactian of rocks with radius r~ (Figure 5j is determined and a volume of rocks is calculated, within limits of a cylindrical column near a well, which are to be subjected to a preliminary treatment Tlpl = ~(ri2 -- rcz2 )m, wherein m is a thickness of a formation-collector, rc is a radius of the well"
In correspondence with this volume, a volume of an acid solution for pumping (pressing through) into a near wait zone of formation is determined: .
i' pZ = ~rl ~ ~~
wherein n is a porosity of rock of a formation-collector.
This portion of solution is pumped into the well, pressed info a near well zone of formation for action on the zone of support pressure. As a result of this action, dissolving of bath a cement of rock and the rock itself is performed. When the dissolved mass is withdrawn, density of rock and action in this zone of stresses is reduced. The evaluation of the obtained effect of depressurization is performed by the geophysical methods, The .
efficiency of treatment with a first cycle can be insufficient. Figure 6 shows that as a result of the first cycle of action, a certain effect is obtained, which is a reduction of maximum value of stresses to the value oy, ~y2. Near the wall of well, a ring of reduced stresses with a radius ro is obtained.
However, -~! 5-within the interval r2 stresses continue to act, which exceed initial stresses of untouched mass.
In this case a .second cycle of pumping is pertormed in accordance with the same or reduced parameters. A change of quantity of the pumped solution to increase the volume Vp~ is necessary in the case if an exterior radius of a ring of compaction is increased rx > r,.
After the second cycle of action, again a control of efficiency is performed and the necessity of a subsequent treatment of the zone is determined.
An idea! result of the treatment is a complete removal of a "splash" of support loads when in the vicinity of a well a "funnel" of stress "is formed, which is characterized by a pattern of monotonous increase of stresses'~nd density of rocks from a watt of the well into a depth of the mass as shown in (Figure 7). .
The achievementofthis pattern is notalways necessary. Even a partial depressurization of rock in the zone of support pressure can provide a sufficient effect of increase in welt productivity. Therefore, a factor of effici$ncy of treatment K is introduced, which characterizes a given critical level, in accordance with which it is necessary to reduce stresses acting in a support zone.
~y~-ffy2 a'y! - yH

The value K > 1 corresponds to a complete unloading of roc(cs in the zone of support pressure as shown in Figure 7. Values 0 < K < 1 correspond to a partial unloading of reeks as shown in Figure 3. In practice the coefficient K is determined experimental#y, but as a rule it can not be equal to 1.
Removal of a "threshold of compaction" in the zone of support pressure in certain conditions #ncreases the productivity of well, not more than by 1 a°lo, which is summed with the effect. of abrasive hydrojet perForat#on. .
As for the selection of concrete composition of technological solutions for this treatment, it should be mentioned that for treatment of a terr#gen collector of productive formation, there are utilized solutions of NaHSOd x Hz0 and/or K2Sz0~ and/or (NH)4S,O8 with concentration 4-?°~
with additions of anion a~~tive surface active substance or a mixture of anion active ar~f non ionogenic surface active substance with concentrations 0.5- .
2°l0. The destruction of clay colmatating raglans with this technological solutions is performed by disturbance of coagulating contacts between clay aggregates of cofmatating regions, dissolution of admixtures, cementing sand, and-dealkyfization of afumosil#cates which form carcases of clay aggregates.
When in a terrigen collector there is a carbonate fraction of higher titan 30°lo and when there is a carbonate collector of the productive formation, then a technological solution with an acid reaction can be a solution of NH2S03H with admixtures of anion active surface active substance and a mixture of anion active and non iongenic surface active substance with concentrat'wn 0.2-t~.4 % and polyphosphates with concer:tratian 0.1-0.2% or a solution of CH3COC1 with concentrations 8-12°!°
with admixtures of anion active surface active substance or a mixture of anion active and non ionogenic surface active substance with concentration g.5-1 % and polyphosphates with concentration 0.1-U.2%, and as polyphosphates N.a5P30,~ andlor Na2[Na4(P03)s] are utilized.
Sulphamine acid actively dissolves carbonate rocks. When a acethyle chloride is dissolved in water, a mixture of asetic and hydrochloric acid is formed in condition of active temperature increase:
CHZCOCI + H20 = CH3COOH-r HCI + AQ ~' , which also provides a dissolution of carbonates in a thusly formed rock area.
The utilization of agents of comptex forming action in the composition of a carrier liquid in the case of Na$PsO,a andlor Na2[Na4(PO$)~]
stabilizes the technological solutions and prevents a secondary deposition of calcium in the case of very low concentrations which are not sufficient for binding of deposited rations into soluble complexes. The stabilization effect of such ~rery small admixtures is connected with adsorption processes_ ~ "
Phosphate and ions are adsorbed on seeds or growing crystals, block active centers and therefore prevent precipitation of salts. As a result of laboratory tests for dissolving of carbonate rocks with such technological solutions with an acid reaction, optimal values of polyphosphates in condition ofi neutralization of solutions are determined as 01-d2°/°.
The above mentioned technological solutions are preferably prepared directly in the treated formation. For example, powder chemical agents for preparation of solution are filled in a transporting package, the package is delivered into an interval of treated formation, and then the transporting package is removed, for example by its dissolution with a dissolving liquid suppti~ info the well. The powder mixture is made from components, introduced into containers {capsules or mini containers) with ,'~'a~r , soluble enclosure, and transported to the interval of intersection of productive ..~.,.;:~.. , formation, preliminarily- veparating it from lower and upper layers with a packer. Then, a dissolution of container is performed, or a solvent for capsule casing and a solvent for agents are introduced into the productive layer. When the solution is ready, the inter-pipe space is cut off by packers, and the solution is pressed into the formation. This leads to an economy of reagents, their more accurate dosage, simplifcation of requirements for a material of column and a pumping mechanism, elimination of corrosion, etc.
This increases the efficiency of treatment by more accurate composi~on of the treating fluid in the productive treated formation" reduces the ~ consumption of agents, and protects equipment of action of chemical agents in the fluid. This approach significantly reduces the volume of required agents, increases the quality of treatment by more accurate correspondence of real working formation-treatment composition to a calculated composition, reduces requirement to equipment and increases its service life.
..
' The transporting package can be formed as a mini container, such as capsules with a soluble enclosure, in particular with the use of starch, in form of balls. The calculated quantity of balls is thrown into the well and then water is poured on them. Starch is dissolved in water without residual and without any harm.
The present invention is illustrated by the following examples:
Exam~te 1:
Initial conditions. A treatment of an operating well with a diameter 8" is performed, with a carbonate collector of 164 ft. at the depth x,562 ft. tt is known that an elasticity module is E=3xfii~?lPa, specific weight .

- _ of rock y~ 125 (b/ft3. The well has an open shaft, and before treatment it is used with a yield 28.3 bbllday.
Performed operations. It has been determined by geophysical methods that porosity of productive formation is 10%, density of the formation in a zone of support pressure p=193.5 Ib/ft ~. Taking this into consideration, speed of cutting 0.45 hour per 1 ft. r and hour concentration of abrasive fluid 0.06 Iblft~ . The composition of abrasive is a sand with grain 0,008-0,04" and quartz content not less than 50°/°.
. The ground equipment is installed which provides a pressure of the abrasive fluid 4,800 psi, a predetermined concentration of abrasive fluid, washing of well, collection of stone material, and receipt of productive fluid. Then a underground equipment is connected, in particulars perforaxor engine with a perforator adjusted to the predetermined cutting speed 0.43"Imiy~ute. Then the underground equipment is lowered to the depth 6,562 ft.~and after adjustment of the equipment of the depth, a slot cutting with the speed 4"/minute is performed. The cutting is performed approximately in 10.45x164=73.8) haurs.
The abrasive hydrdjet perforation is performed only in approximately 75 hours instead of 150 hours in a known method. After the partial slot treatment, the productivity of the well increased over 60 bbllday.
The required reduction of density of the rock in the zone of support pressure was calculated 1x2000(80xI0b - 2x1042x10' 3x10" = 1.75 The irolume of rock to be treated is determined Depth of slotting not less then fourdiameters equivalent to 32", open slotting 4", then we can calculate the volume of the slot:
V~32x4x'164=132 bbl.
Where productive layer in the formation equal164 ft.
as well as required volume of acid:
132x0.1-3.2=10 bbl.
. 3.2-volume without slotting 0.1-porosity of the collector.
Then 10 bbl. of acid is pumped into an interval of treatment, it is pressed into the formation, and afterthe reaction the products of reaction are removed by draining. Then the geophysical observations were performed, and it was determirted that the stresses in the zone of support pressure reduced to fi0 MPa, while a radius of the zone of support pressure increase to 1.6 ft. The obtained reduction of permeability is detem~ined as follows:
P~~,,, - ~'z ) 6562(80 - 60) ~ l Ob dp.= ~ ~ bra= 3.1~" = 0.$4 The quantity of acid for the second cycle of treatment is calculated as follows.
~~J=0.84 lblft.3<1.75 lblft.3 After this, another treatment of the productive interval was perFormed. The geophysical investigations were carried out, and an obtained reduction of density of rock in the zone of support pressure was determined.
A complete removal of stresses in the zone of support pressure made possible to increase the productivity of welt even more than by 20%.
The cost ofthe second stage, which is the formation treatment, and the common time of two cycles was only about 6 hours with an insignificant cost and a relatively simple equipment.
. Therefore, the total time of realization in the given concrete case was correspondingly 80 hour, which is approximately '/2 when compared with the traditional methods of increasing the productivity ofwells.
The efficiency of treatment and the time of maintaining the obtained yield are at least identical.
The main advantage of the proposed method is a significant reduction of labor consumption and the cost ofthe method, with maintaining of increased efficiency. This is achieved mainly by a subdivision of the method into two controlled and regulated stages, and by optimal distribution of labor consumption and cost of the treatment between the two stages.
Simultaneously, the method includes additional technological features which increase its efficiency, namely a new selection of agents and preparation of a technological solution directly in the welt.
The invention takes into consideration that the zone of support .
pressure adjoining the watt is the most responsible in the system of filtration of fluid from the formation into the well. The quantity of flowing fluid (gas) per unit of filtering area is increased in second power when it approaches to the welt. The highest intensity of streams is in this zone. This is the reason for -zz-the maximum "dirtying" of rocks with asphalt-resin and other deposits which substantially reduce the productivity of the well.
It is therefore extremely important to reduce the tendency to accumulation of destroyed particlesof rocks and drilling solution, to eliminate the xane of dirtying and near well zone which is subjected to the action of support pressure and is the most close to the bare zone which is the zone of support pressure.
The proposed invention significantly reduces laborconsumption and costs ofworksforincreasing productivity and unobjectionable movement of fluids in this zone, which explains cleaning of filtering passages and therefore long term action of the obtained effect of treatment.
Figure 2 shows the surface equipment. Reference numeral 1 identifiesla mouth of the well with a fountain equipment, reference numeral 2 identfi~es filters for Leaning of a pulp, reference numeral 3 identifies a block of manifolds, 4 is a pump aggregate, 5 is a sand mixing aggregate, and 6 is a containment.
Figure 3 shows the underground equipment. It includes a coupling clutch 7, an underground engine 8 connected with pumping units and having nozzles, a hydrojet perforator 9, a valve control system 1 t3, with recess and antirecess identified as r' and r".
In Figure 4 reference numeral 19, idenffies a chemically .
treated part of a productive layer with worsened collector properties, while reference numeral 13 identifies a treated part of the productive layer with good collector properties. The ether elements shown in Figure 1 are: a perforator 92, packers 14, pumping compressor pipes with an engine of the perforator 15, non pem7eable rock 16, a productive layer with good collector properties 17, a cut through part of the productive layer with good collector properties 18, a productive layer with worsened collector properties 9 9, a cut through part of the productive layerwith worsened collector properties 20, a tall part 21 and a plug 22.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
What is claimed as new and desired to be protected by Letters ' Patent is set forth in the appended claims.
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Claims (12)

1. A method of increasing the productivity of oil, gas and hydrogeological wells, comprising the steps of cutting slots only in a nearwell zone so as to perform a partial unloading of the well and to remove a part of support stresses; and cyclically treating well with a formation treating substance so as to remove a remaining part of the support stresses, with controlling a density of a formation and correcting the cyclical treatment in correspondence with the density of the formation.

2. A method as defined in claim 1, wherein said slot cutting includes cutting of slots only in a surrounding column, a cement layer, and a part of rock which immediately adjoins the well.

3. A method as defined in claim 2, wherein said slot cutting includes preliminarily determining a porosity of rock of the formation of the near well zone and a depth of a zone of support stresses, while the cyclical treatment is performed in dependence on the determined porosity and the depth.

4. A method as defined in claim 3, wherein when with the porosity of rock approximately 15% and higher, the slot cutting is performed to a depth 1-1.5 of a well diameter.

5. A method as defined in claim 3, wherein when the porosity is less than approximately 15%, the slot cutting is performed to the depth of not less than 4 well diameters.

6. A method as defined in claim 1, wherein said cyclical treatment includes, before each cycle determining a radius of a zone of support pressure and a maximum stress acting in it, and performing the cyclical treatment for all parts of a formation adjoining the well including the zone of support pressure, and after each cycle of the cyclical treatment controlling a change of density or permeability of rock in the zone of support pressure.

7. A method as defined in claim 6; and further comprising stopping of the cyclical treatment when a density of rock in the zone of support pressure reduces by a value determined in accordance with the formula .DELTA..rho.>K.multidot..rho. (.sigma. - .gamma.H)E
wherein K is a coefficient of efficiency of treatment, p .rho.is a density of rock of a non disturbed formation at the depth H, lb/ft3, .sigma. is a maximum stress acting in the zone of support pressure MPa, .gamma. is a specific weight of rock of the formation lb/ft3, E is an elasticity module of rock of the formation MPa.

8. A method as defined in claim 1; and further comprising introducing the formation-treating substance in form of jets.

9. A method as defined in claim 8, wherein the formation-treating substance includes solutions of NaHSO4 x H2O and/or (NH)4S7O8 with concentration 4-7% and with admixtures of anion active surface active substance or a mixture of anion active and non ionogenic surface active substance with concentration 0.5-2%.

10. A method as defined in claim 8, wherein the formation-treating substance includes a solution of NH2SO4H with admixture of anion active surface active substance or a mixture of anion active and non ionogenic surface active substance with concentration 0.2-0.4% and polyphosphate with concentration 0.1-0.2% or solution of CH3COCl with concentration 6-2% with admixtures of anion active surface active substance or a mixture of anon active and non ionogenic surface active substance with concentration of 0.5-1 % and a polyphosphates with concentration 0.1-0.2%
and tho polyphosphates include Na5P3O10 and/or Na2[Na11(PO3)6].

11. A method as defined in claim 1; and further comprising preparing the formation-treating substance directly in a well, and in an interval of a formation.

12. A method as defined in claim 11, wherein said preparing of the formation treating substance including using chemical agents in a transporting package, delivering the transporting package with the agents into the formation, and removing the transporting package.
14. A method as defined in claim 12; and further comprising using as the transporting package a microcontainer formed as a capsule with soluble wall.
15. A method as defined in claim 14; and further comprising using a soluble polyesthylene film as the soluble wall.
16. A method as defined in claim 14; and further comprising making the microcontainer from a binder, which is soluble in water without residues.

17. A method as defined in claim 14; and further comprising forming the microcontainer with a shape selected of the group consisting of a ball shape and a cylinder shape.
18. A system for increasing the productivity of oil, gas and hydrogeological wells, comprising means for cutting slots only in a near well zone so as to perform a partial unloading of the well and to remove a part of support stresses; and means for cyclically treating well with a formation-treating substance so as to remove a remaining part of the support stresses, with controlling a density of a formation and correcting the cyclical treatment in correspondence with the density of the formation.
19. A system as defined in claim 18, wherein said slot cutting means is operative for slot cutting which includes cutting of slots only in a surrounding column, a cement layer, and a part of rock which immediately adjoins the well.
20. A system as defined in claim 19, wherein said slot cutting means is operative for slot cutting which includes preliminarily determining a porosity of rock of the formation of the near well zone and a depth of a zone of support stresses, while the cyclical treatment is performed in dependence on the determined porosity and the depth.
21. A system as defined in claim 18, wherein said cyclical treatment means includes means which, before each cycle, determine a radius of a zone of support pressure and a maximum stress acting in it, and perform the cyclical treatment for all parts of a formation adjoining the well including the zone of support pressure, and after each cycle of the cyclical treatment control a change of density or permeability of rock in the zone of support pressure.

22. A system as defined in claim 18; and further comprising means for introducing the formation-treating substance in form of jets.

23. A system as defined in claim 22, wherein said introducing means introduce the formation-treating substance which includes solutions of NaHSO4 x H2O and/or (NH)4S7O8 with concentration 4-7% and with admixtures of anion active surface active substance or a mixture of anion active and non ionogenic surface active substance with concentration 0.5-2%.
24. A system as defined in claim 22, wherein said substance introducing means introduce the formation-treating substance which includes a solution of NH2SO4H with admixtures of anion active surface active substance or a mixture of anion active and non ionogenic surface active substance with concentration 0.2-0.4% and polyphosphate with concentration 0.1-0.2% or solution of CH9COCl with concentration 6-2% with admixtures of anion active surface active substance or admixture of anion active and non ionogenic surface active substance with concentration of 0.5-1 % and a polyphosphates with concentration 0.1-0.2%, and the polyphosphates include Na5P3O10 and/or Na2[Nan(PO3)6].
25. A system as defined in claim 18; and further comprising means for preparing the formation-treating substance directly in a well, and in an interval of a formation.

26. A system as defined in claim 25, wherein said means for preparing the formation treating substance including means using chemical agents in a transporting package, delivering the transporting package with the agents into the formation, and removing the transporting package.
27. A system as defined in claim 26, wherein said transporting package is a microcontainer formed as a capsule with soluble wall.
28. A system as defined in claim 27, wherein said soluble wall is composed of a soluble polyesthylene film.
29. A system as defined in claim 27, wherein said microcontainer is composed of a binder, which is soluble in water without residues.
30. A system as defined in claim 27, wherein said microcontainer has a shape selected of the group consisting of a ball shape and a cylinder shape.

31. A system as defined in claim 18, wherein said means include a surface equipment and an underground equipment.

32. A system as defined in claim 31, wherein said surface equipment includes a fountain equipment, filters for cleaning a pulp, a block of manifolds, a pulp, a block of manifolds, a pump aggregate, a sand mixing equipment, and a contaminant, said underground equipment including a coupling clutch, an underground engine, a hydrojet perforator and a valve control system.