CN103837452A - Acidifying return stimulation experiment method - Google Patents
Acidifying return stimulation experiment method Download PDFInfo
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- CN103837452A CN103837452A CN201210481825.0A CN201210481825A CN103837452A CN 103837452 A CN103837452 A CN 103837452A CN 201210481825 A CN201210481825 A CN 201210481825A CN 103837452 A CN103837452 A CN 103837452A
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Abstract
The invention discloses an acidifying return stimulation experiment method. The method comprises the following steps: 1, determining the original permeability of a rock core; 2, pressing a return solution in the rock core under a nitrogen cylinder pressurization condition until the flow of the solution flowing through the rock core is stable, and stabilizing for a period of time; 3, sealing the tail end of a rock core holder, and pressing a certain amount of hydrochloric acid in the rock core; 4, carrying out restrained pressure acidification, relieving the pressure, and spraying the obtained acid solution from the forward end of the rock core holder; and 5, determining the permeability of the acidified rock core. The method enables the acidifying return stimulation experiment to be completed, has simple steps, and substantially reduces the stimulation cost.
Description
Technical field
The present invention relates to a kind of acidifying and return row's analogue experiment method.
Background technology
Foam is the heterogeneous dispersed system that insoluble (or slightly soluble) gas dispersion forms in liquid or molten solids, and wherein liquid is external phase (dispersion medium), and gas is discontinuous phase (disperse phase).Foam has very large surface free energy, and after broken bubble, the total surface area of system liquid greatly reduces, and energy reduces, thereby it is the unsettled system on a kind of thermodynamics, but under certain condition, take suitable measure, can keep certain stability.In order to characterize the state of phase in this mixed system, two kinds of the most frequently used methods are Rustem Kazakov method and Michele's method.Rustem Kazakov adopts coefficient of foaming value Kf, and in the time of Kf ﹤ 3.8, this mixed system is considered to the gas emulsion in liquid, is stable foam in the time of Kf>3.8.Michele adopts the foam quality QF under normal temperature and pressure to describe, i.e. the ratio of gas volume and foam cumulative volume in foam.In the time of QF=0～0.54, mixed system shows as Newtonian fluid; In the time of QF=0.54～0.96, show as non-Newtonian fluid; In the time of QF>0.96, foam becomes mist.In order to increase the stability of foam, also need in solution, add the materials such as frothing agent (surfactant) and foam stabilizer in actual applications.
The precondition of formation of foam is to have gas and liquid to be in contact with one another.And contacting of gas and liquid can reach by three kinds of approach: the one, directly in liquid, pass into external gas; The 2nd, utilize the stirring of air-flow in gas well; The 3rd, the reactant in solution reacts under certain condition and produces insoluble gas, thereby achieves the goal.
Pure liquid can not form stable foam.For example pure water, only adds soap or other surfactant, could form foam.Other liquid, as ethanol, benzene etc., can not form foam.Can form the liquid of stable foam, at least must have two or more components, water phase surfactant mixture is the typical system that easily produces foam, and protein and some other water-soluble polymer solution also easily produce and stablize lasting foam.
The stability of foam refers to the persistence after foam generates, i.e. " life-span " length of foam.It is constant whether liquid film keeps, and is the key of foam stability, and this just requires liquid film to have some strength, can resist extraneous various impact and remain unchanged.Affect the principal element of foam stability, that is affect the factor more complicated of thickness of liquid film and surface film intensity:
(1) surface tension: when foam generates, along with the increase of liquid surface area, the energy of system is also along with increase.In the time that foam destroys, the energy of system is also with regard to corresponding decline.But simple surface tension is not the determinative that affects foam stability.Consider from energy viewpoint, low surface tension is conducive to the formation of foam, generates the foam of identical total surface area, can do work less, but can not guarantee that foam has good stability.Only have when surface film have some strength, can form polyhedral foam time, low surface tension just contributes to the stable of foam.Pressure reduction and surface tension between intersection and the planar film of liquid film are directly proportional, and the low pressure reduction of surface tension is little, thereby drain age velocity is slower, and thinning of liquid film is slower, is conducive to foam stabilization.
(2) surface viscosity: the key factor that determines foam stability is film strength, and Film strength depends mainly on the soundness of surface film absorption, measures as it take surface viscosity experimentally.
Surface viscosity refers to the viscosity in surface film liquid unimolecular layer.This viscosity mainly hydrophilic group interphase interaction and the hydration of surface active molecules in its surperficial unimolecular layer produces.Surface viscosity is larger, and the film strength more stability of macrofoam is also just better.Surface film strength is relevant with the intermolecular interaction of adsorption, and the large person's film strength that interacts is also large.General macromolecular organic compound is because molecular weight is larger, and intermolecular interaction is stronger, therefore the foam stability that its aqueous solution forms is also higher.The more surfactant of branch in general hydrophobic group, its intermolecular interaction is poorer than straight chain person, thereby the surface viscosity of solution is less, and the stability of foam is also poor.
(3) viscosity of solution: surface viscosity is large, bubble film is often survivable, here there is double action: increase first liquid film surface strength, another make the liquid that closes on liquid film two surface film be difficult for discharging (because surface viscosity is large, surface is closed on liquid and is also difficult for flowing).As can be seen here, if the viscosity of liquid own is larger, the liquid in liquid film is difficult for discharging, and the speed that thickness of liquid film diminishes is slower, thereby has delayed the time of liquid-sheet disintegration, has increased the stability of foam.But it should be noted that liquid internal viscosity is only a cofactor, if do not have surface film to form, even if inner viscosity is large again, also differs and form surely stable foam.
(4) capillary " reparation " effect: in the time that the liquid film of foam is subject to external impacts, local attenuation phenomenon can occur, attenuation part surface area increases, and the surfactant molecule density of absorption also reduces, so the surface tension at this place raises.Therefore, surfactant molecule tries hard to, to the migration of attenuation part, make the molecule of Adsorption on Surface return to original density, and surface tension is reduced to again original level.In transition process, active agent molecule also can carry contiguous thin layer liquid and move together, and result makes the liquid film thickening again of attenuation.The recovery of this capillary recovery and thickness of liquid film all causes Film strength to recover, and Bearing performance is that foam has good stability, this so-called capillary " reparation " effect, namely so-called Marangoni effect.
Viewpoint from energy is seen, when liquid film is expanded, will reduce the concentration of activating agent from the teeth outwards, and increases surface tension, and this is the process of a needs acting, and further expansion will be done larger merit.And when liquid film is shunk, although reduced surperficial energy, increase the concentration of adsorption molecule, this is unfavorable for automatic contraction.This anti-surface spreading of liquid film and the ability of anti-contraction also only just can occur in the time that surfactant molecule is adsorbed in liquid film, and neat liquid is not possess this repairing performance, so can not form stable foam.
For this kind of repair, should be taken into account two kinds of different processes.One is the process from the paramount surface tension of low surface tension zone migration active agent molecule region; Be the extremely lip-deep process of molecular adsorption in solution in addition.The result of this process also can make the surface tension of impacting liquid film return to initial value, has recovered the density of adsorption molecule simultaneously.If but a rear process is carried out comparatively fast (adsorption rate is fast), the absorption molecule lacking at liquid film expansion is supplied major part by adsorbing, rather than passes through surface migration.So, though the surface tension at the place of being hit and absorption molecular density can restore, not thickening (because non-migratory molecule brings solution) again of the liquid film of attenuation.Such liquid film, its intensity is obviously poor, and foam stability is also therefore poor.The foam stability of general alcohol solution is not high, has certain relation with alcohol adsorption from solution in surperficial speed; General surfactant adsorption rate of (﹤ cmc) in the time that concentration is lower is slower, and foam stability is higher.The concentration of surfactant solution exceedes cmc when more, and adsorption speed, therefore often finds that foam stability is lower.
(5) gas is by the diffusion (liquid film gas penetration potential) of liquid film: its Air Bubble Size of freshly prepd foam is inhomogeneous.Due to the result of additonal pressure, the air pressure in vesicle is larger than the air pressure in bulla, goes so the gas in vesicle can be diffused in bulla, and result is that vesicle diminishes gradually so that disappears, and it is large that bulla becomes gradually.Owing to there being additonal pressure, final all bubbles will all disappear.In this whole process, liquid film depends on gas through liquid film capacity of water and existing, and this is just the gas penetration potential of liquid film.Conventionally can be with bubble radius on liquid level and time rate of change as the standard of weighing liquid film gas penetration potential.General bubble gas penetration potential is low, and its surface viscosity is just high, and the foam stability forming is all right.
(6) impact of surface charge: if bubble film with the electric charge of same-sign, two surfaces of liquid film are mutually exclusive, and even to prevent that thinning of liquid film from breaking.Ionic surfactant is during as frothing agent, and due to the result of adsorption, surface active agent ion will be enriched on surface.Two surperficial electricity effects of repelling each other start significantly, prevent the further attenuation of liquid film.This kind of electricity repel each other act on liquid film when thicker impact little.When in solution, electrolyte concentration is higher, diffuse electric double layer compression, the electricity effect of repelling each other reduces, and film thickness diminishes, and also can make its impact reduce.
Comprehensive above-mentioned discussion can be found out, although it is varied to affect the factor of foam stability, wherein most important factor is surperficial film strength.For surfactant, as for the generalized case of frothing agent and foam stabilizer, the tight fecundity of adsorption molecules align is most important factor, and foam stability depends on surface structure and the interaction of adsorption molecule.Adsorption molecular structure closely, interact when strong, not only surface film itself has larger intensity, can also make contiguous solution layer below superficial layer be difficult for flowing away (because of surface viscosity large), discharge opeing is difficulty relatively, thickness of liquid film more easily keeps; In addition, arrange surface molecular closely and can also reduce the permeability of gas, thereby increase the stability of foam.
The frothing agent of applying on oil field is except reducing significantly the surface tension at gas-liquid interface, HLB (parent hates equilibrium value) remains on inside and outside 9～15 scopes, also must possess: 1. foamability strong (, under same case, the foam volume of generation is many); 2. the foam forming has certain stability, and foam is difficult for breaking, long half time; 3. foam carrier amount is large; 4. formation condition (as: temperature, salinity and pH value etc.) is had to certain adaptive faculty.
Summary of the invention
The object of the invention is to overcome the shortcoming and defect of above-mentioned prior art, provide a kind of acidifying to return row's analogue experiment method, the method can complete the simulated experiment of acidifying being returned to row, and step is simple, greatly reduces simulated cost.
Object of the present invention is achieved through the following technical solutions: row's analogue experiment method is returned in a kind of acidifying, comprises the following steps:
(a) first, measure rock core original permeability;
(b) first will return discharge opeing and be pushed down into rock core at nitrogen cylinder pressurized conditions, until it is stable to flow through the liquid inventory of rock core, stablize a period of time;
(c) be pressed into rock core then by core holding unit end seal, then by a certain amount of hydrochloric acid;
(d) acidifying that builds the pressure, release, from core holding unit forward end open flow acid solution;
(e) measure the core permeability after acidifying.
In described step (b), be 3～5min stabilization time.
In described step (c), the massfraction of hydrochloric acid is 15%.
In described step (d), experimental temperature remains on 60 ℃ of left and right.
In described step (d), release after 30min.
In sum, the invention has the beneficial effects as follows: can complete the simulated experiment of acidifying being returned to row, and step is simple, greatly reduces simulated cost.
Embodiment
Below in conjunction with embodiment, the present invention is described in further detail, but embodiments of the present invention are not limited only to this.
Embodiment:
The invention discloses a kind of acidifying and return row's analogue experiment method, comprise the following steps:
(a) first, measure rock core original permeability;
(b) first will return discharge opeing and be pushed down into rock core at nitrogen cylinder pressurized conditions, until it is stable to flow through the liquid inventory of rock core, stablize a period of time;
(c) be pressed into rock core then by core holding unit end seal, then by a certain amount of hydrochloric acid;
(d) acidifying that builds the pressure, release, from core holding unit forward end open flow acid solution;
(e) measure the core permeability after acidifying.
In described step (b), be 3～5min stabilization time.
In described step (c), the massfraction of hydrochloric acid is 15%.
In described step (d), experimental temperature remains on 60 ℃ of left and right.
In described step (d), release after 30min.
Result is as shown in the table:
From data in table, for core permeability, the Combined Processing effect of acid solution+return discharge opeing will obviously be better than independent acid solution treatment effect.Can know by inference from this result, experiment gained returns discharge opeing and has good result to promoting residual acid to return row.
The above, be only preferred embodiment of the present invention, not the present invention done to any pro forma restriction, every foundation technical spirit of the present invention, and any simple modification, equivalent variations that above embodiment is done, within all falling into protection scope of the present invention.
Claims (5)
1. row's analogue experiment method is returned in acidifying, it is characterized in that, comprises the following steps:
(a) first, measure rock core original permeability;
(b) first will return discharge opeing and be pushed down into rock core at nitrogen cylinder pressurized conditions, until it is stable to flow through the liquid inventory of rock core, stablize a period of time;
(c) be pressed into rock core then by core holding unit end seal, then by a certain amount of hydrochloric acid;
(d) acidifying that builds the pressure, release, from core holding unit forward end open flow acid solution;
(e) measure the core permeability after acidifying.
2. row's analogue experiment method is returned in a kind of acidifying according to claim 1, it is characterized in that, in described step (b), be 3～5min stabilization time.
3. row's analogue experiment method is returned in a kind of acidifying according to claim 1, it is characterized in that, in described step (c), the massfraction of hydrochloric acid is 15%.
4. row's analogue experiment method is returned in a kind of acidifying according to claim 1, it is characterized in that, in described step (d), experimental temperature remains on 60 ℃ of left and right.
5. row's analogue experiment method is returned in a kind of acidifying according to claim 1, it is characterized in that, and in described step (d), release after 30min.
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| CN201210481825.0A CN103837452A (en) | 2012-11-24 | 2012-11-24 | Acidifying return stimulation experiment method |
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| CN201210481825.0A CN103837452A (en) | 2012-11-24 | 2012-11-24 | Acidifying return stimulation experiment method |
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| CN103837452A true CN103837452A (en) | 2014-06-04 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108225998A (en) * | 2016-12-15 | 2018-06-29 | 中国石油化工股份有限公司 | Acid stimulation analogue experiment method under 7 cm diameter rock core stratum temperature and pressure |
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- 2012-11-24 CN CN201210481825.0A patent/CN103837452A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108225998A (en) * | 2016-12-15 | 2018-06-29 | 中国石油化工股份有限公司 | Acid stimulation analogue experiment method under 7 cm diameter rock core stratum temperature and pressure |
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Application publication date: 20140604 |