Preparation method of well killing fluid
阅读说明：本技术 一种压井液的制备方法 (Preparation method of well killing fluid ) 是由 张海军 高太文 葛红江 杜会尧 于 2020-06-12 设计创作，主要内容包括：本申请公开了一种压井液的制备方法,属于油田开发技术领域。该方法首先确定油层水中多项预设离子的当量浓度和基液中多项预设离子的当量浓度,然后根据生产层的油层水中的多项预设离子的当量浓度,通过向基液中添加稀释液和/或化学试剂制备仿油层水溶液,并进一步调节仿油层水溶液的PH值和黏度值,得到压井液。本申请实施例制备得到的压井液中相应的多项预设离子的浓度与油层水中多项预设离子的当量浓度相当,且PH值和黏度值也与油层水相当,因而使压井液和油层水之间具有良好的配伍性,避免了采用压井液在压井作业中发生油层过敏现象,从而保护了油层的孔隙度和渗透率,保证油井产量。(The application discloses a preparation method of a well killing fluid, and belongs to the technical field of oilfield development. The method comprises the steps of firstly determining the equivalent concentration of multiple preset ions in oil layer water and the equivalent concentration of multiple preset ions in base liquid, then adding diluent and/or chemical reagents into the base liquid according to the equivalent concentration of the multiple preset ions in the oil layer water of a production layer to prepare an oil layer simulating aqueous solution, and further adjusting the pH value and viscosity value of the oil layer simulating aqueous solution to obtain the well killing liquid. The concentration of ion is predetermine to corresponding multinomial in the kill fluid that this application embodiment prepared obtains is equivalent with the multinomial equivalent concentration of predetermineeing the ion in the oil reservoir aquatic, and PH value and viscosity number value also are equivalent with the oil reservoir water, therefore make and have good compatibility between kill fluid and the oil reservoir water, avoided adopting the kill fluid to take place the oil reservoir allergy phenomenon in the kill operation to the porosity and the permeability of oil reservoir have been protected, oil well output is guaranteed.)
1. A method of preparing a kill fluid, the method comprising:
determining the equivalent concentration of multiple preset ions in oil layer water;
determining the equivalent concentration of the plurality of preset ions in the base fluid;
comparing the equivalent concentration of the multiple preset ions in the oil layer water with the equivalent concentration of the multiple preset ions in the base liquid, and when the equivalent concentration of at least one ion in the multiple preset ions in the base liquid is not less than the equivalent concentration of the corresponding ion in the oil layer water, adding a diluent and a chemical reagent into the base liquid to obtain an oil layer simulating aqueous solution; when the equivalent concentrations of the multiple preset ions in the base liquid are all smaller than the equivalent concentrations of corresponding ions in the oil layer water, adding a chemical reagent into the base liquid to obtain an oil layer simulating aqueous solution;
adjusting the pH value of the simulated oil layer aqueous solution according to the pH value of the oil layer water; and adjusting the viscosity value of the simulated oil layer aqueous solution according to the viscosity value of the oil layer water to obtain the well killing fluid.
2. The method according to claim 1, wherein when the equivalent concentration of at least one of the plurality of predetermined ions in the base fluid is not less than the equivalent concentration of the corresponding ion in the reservoir water, adding a diluent and a chemical reagent to the base fluid to obtain a simulated reservoir aqueous solution, comprises:
determining the equivalent concentrations of the plurality of preset ions in the diluent;
determining ions with the maximum equivalent concentration difference ratio value as reference ions according to the equivalent concentrations of the preset ions in the oil layer water, the equivalent concentrations of the preset ions in the base liquid and the equivalent concentrations of the preset ions in the diluent;
preparing an intermediate solution based on the base fluid and the diluent according to the equivalent concentration of the reference ion in the reservoir water such that the equivalent concentration of the reference ion in the intermediate solution is equal to the equivalent concentration of the reference ion in the reservoir water, and then calculating the equivalent concentrations of the other ions than the reference ion among the plurality of preset ions of the intermediate solution;
calculating the addition amount of the chemical agent corresponding to each ion of the other ions according to the equivalent concentration of the other ions in the intermediate solution and the equivalent concentration of the other ions in the reservoir water;
and adding the chemical reagent into the intermediate solution to obtain the oil-imitating layer aqueous solution.
3. The method according to claim 1, wherein when the equivalent concentrations of the plurality of predetermined ions in the base fluid are less than the equivalent concentrations of the corresponding ions in the reservoir water, adding a chemical reagent to the base fluid to obtain an oil-like layer aqueous solution, comprises:
calculating the addition amount of the chemical reagent corresponding to each ion of the plurality of preset ions according to the equivalent concentration of the plurality of preset ions in the base fluid and the equivalent concentration of the plurality of preset ions in the oil layer water;
and adding the chemical reagent into the base liquid to obtain the oil-imitating layer aqueous solution.
4. The method according to any one of claims 1 to 3, wherein the diluent is fresh water and/or fresh water.
5. The production method according to any one of claims 1 to 3, wherein the plurality of predetermined ions include calcium ion, magnesium ion, sulfate ion, carbonate ion, and bicarbonate ion.
6. The method according to claim 5, wherein when the equivalent concentrations of the plurality of predetermined ions in the base fluid are less than the equivalent concentrations of the corresponding ions in the reservoir water, adding a chemical agent to the base fluid comprises:
when the equivalent concentration of calcium ions in the base fluid is less than that of calcium ions in the oil layer water, adding calcium chloride into the base fluid;
when the equivalent concentration of magnesium ions in the base fluid is less than that of magnesium ions in the oil layer water, adding magnesium chloride into the base fluid;
when the equivalent concentration of sulfate ions in the base liquid is less than that of the sulfate ions in the oil layer water, adding sodium sulfate and/or potassium sulfate into the base liquid;
when the equivalent concentration of carbonate ions in the base liquid is less than that of the carbonate ions in the oil layer water, adding sodium carbonate and/or potassium carbonate into the base liquid;
and when the equivalent concentration of the bicarbonate ions in the base fluid is less than that of the bicarbonate ions in the oil layer water, adding sodium bicarbonate and/or potassium bicarbonate into the base fluid.
7. The method of claim 1, wherein the base fluid is filtered formation water or surface water.
8. The method of claim 1, wherein the base fluid has a suspended solid content of less than 10 mg/L.
9. The method of claim 1, wherein adjusting the PH of the simulated reservoir aqueous solution based on the PH of the reservoir water comprises:
determining the pH value of the reservoir water;
and adding hydrochloric acid or sodium hydroxide into the oil layer simulating aqueous solution according to the pH value of the oil layer water.
10. The method of claim 1, wherein adjusting the viscosity value of the simulated reservoir aqueous solution according to the viscosity value of reservoir water comprises:
determining the viscosity value of the reservoir water;
and adding xanthan gum or polyacrylamide into the oil layer simulating aqueous solution according to the viscosity value of the oil layer water.
Technical Field
The application relates to the technical field of oilfield development, in particular to a preparation method of a well killing fluid.
Background
In oilfield development, it is often necessary to perform work and construction downhole in order to improve economic efficiency. In order to avoid accidents such as blowout during downhole operation, a well killing fluid is generally used to perform fluid well killing on an operation construction oil well.
The existing well killing fluid and oil layer fluid are not properly compatible, and the problem of oil layer allergy such as water sensitivity, salt sensitivity, acid sensitivity, alkali sensitivity, temperature sensitivity, quick sensitivity and the like is easy to occur. For example, when clean water is used for killing a well, the clean water has lower content of each ion component than that of oil layer water, so that water sensitivity is easily caused; when brine is used for killing wells, salt sensitivity is easily caused because brine is higher in ion content than oil layer water. Oil layer allergy can cause the swelling or falling of argillaceous components in sandstone to block an oil layer, thereby reducing the permeability of the oil layer and influencing the yield of an oil well and even yielding water.
In order to prevent oil layer allergy, the prior art also adopts oil layer protection fluid to kill the well, i.e. a surfactant is added into the kill fluid, however, the addition of the surfactant increases the preparation cost, and the kill effect of the kill fluid cannot be ensured.
Disclosure of Invention
The embodiment of the application provides a preparation method of the well killing fluid, so that the prepared well killing fluid and the reservoir fluid have good compatibility.
Specifically, the method comprises the following technical scheme:
a method of preparing a kill fluid is provided, the method comprising:
determining the equivalent concentration of multiple preset ions in oil layer water;
determining the equivalent concentration of the plurality of preset ions in the base fluid;
comparing the equivalent concentration of the multiple preset ions in the oil layer water with the equivalent concentration of the multiple preset ions in the base liquid, and when the equivalent concentration of at least one ion in the multiple preset ions in the base liquid is not less than the equivalent concentration of the corresponding ion in the oil layer water, adding a diluent and a chemical reagent into the base liquid to obtain an oil layer simulating aqueous solution; when the equivalent concentrations of the multiple preset ions in the base liquid are all smaller than the equivalent concentrations of corresponding ions in the oil layer water, adding a chemical reagent into the base liquid to obtain an oil layer simulating aqueous solution;
adjusting the pH value of the simulated oil layer aqueous solution according to the pH value of the oil layer water; and adjusting the viscosity value of the simulated oil layer aqueous solution according to the viscosity value of the oil layer water to obtain the well killing fluid.
In a possible embodiment, when the equivalent concentration of at least one of the preset ions in the base fluid is not less than the equivalent concentration of the corresponding ion in the reservoir water, adding a diluent and a chemical reagent to the base fluid to obtain a simulated reservoir aqueous solution, includes:
determining the equivalent concentrations of the plurality of preset ions in the diluent;
determining ions with the maximum equivalent concentration difference ratio value as reference ions according to the equivalent concentrations of the preset ions in the oil layer water, the equivalent concentrations of the preset ions in the base liquid and the equivalent concentrations of the preset ions in the diluent;
preparing an intermediate solution based on the base fluid and the diluent according to the equivalent concentration of the reference ion in the reservoir water such that the equivalent concentration of the reference ion in the intermediate solution is equal to the equivalent concentration of the reference ion in the reservoir water, and then calculating the equivalent concentrations of the other ions than the reference ion among the plurality of preset ions of the intermediate solution;
calculating the addition amount of the chemical agent corresponding to each ion of the other ions according to the equivalent concentration of the other ions in the intermediate solution and the equivalent concentration of the other ions in the reservoir water;
and adding the chemical reagent into the intermediate solution to obtain the oil-imitating layer aqueous solution.
In a possible embodiment, when the equivalent concentrations of the plurality of preset ions in the base fluid are all less than the equivalent concentrations of the corresponding ions in the reservoir water, adding a chemical reagent to the base fluid to obtain an oil reservoir-like aqueous solution, includes:
calculating the addition amount of the chemical reagent corresponding to each ion of the plurality of preset ions according to the equivalent concentration of the plurality of preset ions in the base fluid and the equivalent concentration of the plurality of preset ions in the oil layer water;
and adding the chemical reagent into the base liquid to obtain the oil-imitating layer aqueous solution.
In a possible embodiment, the dilution liquid is fresh water and/or fresh water.
In one possible embodiment, the plurality of preset ions includes calcium ions, magnesium ions, sulfate ions, carbonate ions, and bicarbonate ions.
In a possible embodiment, the adding a chemical reagent to the base fluid when the equivalent concentrations of the plurality of preset ions in the base fluid are all less than the equivalent concentrations of the corresponding ions in the reservoir water includes:
when the equivalent concentration of calcium ions in the base fluid is less than that of calcium ions in the oil layer water, adding calcium chloride into the base fluid;
when the equivalent concentration of magnesium ions in the base fluid is less than that of magnesium ions in the oil layer water, adding magnesium chloride into the base fluid;
when the equivalent concentration of sulfate ions in the base liquid is less than that of the sulfate ions in the oil layer water, adding sodium sulfate and/or potassium sulfate into the base liquid;
when the equivalent concentration of carbonate ions in the base liquid is less than that of the carbonate ions in the oil layer water, adding sodium carbonate and/or potassium carbonate into the base liquid;
and when the equivalent concentration of the bicarbonate ions in the base fluid is less than that of the bicarbonate ions in the oil layer water, adding sodium bicarbonate and/or potassium bicarbonate into the base fluid.
In one possible embodiment, the base fluid is filtered formation water or surface water.
In one possible embodiment, the content of suspended solids in the base liquid is less than 10 mg/L.
In one possible embodiment, the adjusting the PH of the reservoir-simulating aqueous solution according to the PH of the reservoir water comprises:
determining the pH value of the reservoir water;
and adding hydrochloric acid or sodium hydroxide into the oil layer simulating aqueous solution according to the pH value of the oil layer water.
In one possible embodiment, the adjusting the viscosity value of the reservoir simulating aqueous solution according to the viscosity value of the reservoir water comprises:
determining the viscosity value of the reservoir water;
and adding xanthan gum or polyacrylamide into the oil layer simulating aqueous solution according to the viscosity value of the oil layer water.
The beneficial effects brought by the technical scheme provided by the embodiment of the application at least comprise:
according to the embodiment of the application, firstly, diluent and/or chemical reagent are added into base fluid according to the equivalent concentration of multiple preset ions in reservoir water of a production layer to prepare the reservoir simulating aqueous solution, and then the pH value and the viscosity value of the reservoir simulating aqueous solution are further adjusted according to the pH value and the viscosity of the reservoir water of the production layer to obtain the well killing fluid. The concentration of ion is predetermine to corresponding multinomial in the kill fluid that this application embodiment prepared obtains is equivalent with the multinomial equivalent concentration of predetermineeing the ion in the oil reservoir aquatic, and PH value and viscosity number value also are equivalent with the oil reservoir water, and then make and have good compatibility between kill fluid and the oil reservoir liquid, has avoided adopting the kill fluid to take place the oil reservoir allergy phenomenon at the kill process to the porosity and the permeability of oil reservoir have been protected, oil well output is guaranteed.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a step diagram of a method for preparing a control fluid provided by an embodiment of the present application.
Detailed Description
In order to make the technical solutions and advantages of the present application clearer, the following will describe the embodiments of the present application in further detail with reference to the accompanying drawings. Unless defined otherwise, all technical terms used in the examples of the present application have the same meaning as commonly understood by one of ordinary skill in the art.
The sensitivity of the reservoir refers to the property that the pore structure and the permeability of the reservoir are changed due to various physical or chemical actions of the oil and gas reservoir and external fluid, and the sensitivity of the reservoir can cause oil layer allergy.
Generally, oil reservoir water contains hundreds of inorganic and organic components, while the organic component usually does not react with the stratum, the inorganic component usually changes due to the combination of the inorganic component and the stratum ions, which is visually shown as the change of volume, and the oil reservoir water can measure dozens of inorganic components, but the cation: sodium, potassium, calcium, magnesium ion content, and anion: chloride ion, carbonate ion, bicarbonate ion, sulfate ion, their mass ratio in each component accounts for more than 99%. When the oil well is operated, if the water ion component content of the well killing fluid for killing the well is different from that of the oil layer, the oil layer allergy problems such as water sensitivity, salt sensitivity, acid sensitivity, alkali sensitivity, temperature sensitivity, quick sensitivity and the like are easily caused. For example, adversely affecting well production.
The mechanism and hazard of oil layer allergy are further illustrated below by taking water sensitivity as an example. The water sensitivity refers to the phenomenon that when external fluid incompatible with an oil layer enters the oil layer, clay minerals are hydrated, expanded, dispersed and migrated, so that the permeability of the oil layer is reduced to different degrees. More specifically, the external fluid causes bentonite containing montmorillonite in an oil layer to absorb water and swell, block the oil layer or reduce the permeability of the oil layer, influences the flow of crude oil molecules, has high individual viscosity of the crude oil molecules and even causes water to be discharged.
In the initial stage of exploitation of oil production well, because of the large pressure of oil layer, the energy for driving liquid in layer to flow is large, and various allergic problems are not obvious, but with the continuous development, the pressure of oil layer is gradually reduced, and in addition, the liquid contradiction between oil layer and oil layer is gradually shown due to the influence of injected water component, and especially the influence of well-killing fluid is more obvious during operation.
The embodiment of the application provides a preparation method of a well killing fluid, and as shown in figure 1, the method comprises the following steps:
step 101, determining equivalent concentrations of multiple preset ions in oil layer water;
102, determining equivalent concentrations of multiple preset ions in base liquid;
103, comparing the equivalent concentration of a plurality of preset ions in the oil layer water with the equivalent concentration of a plurality of preset ions in the base liquid, and adding a diluent and a chemical reagent into the base liquid to obtain an oil layer simulating aqueous solution when the equivalent concentration of at least one ion in the plurality of preset ions in the base liquid is not less than the equivalent concentration of the corresponding ion in the oil layer water; when the equivalent concentration of a plurality of preset ions in the base liquid is smaller than the equivalent concentration of corresponding ions in the oil layer water, adding a chemical reagent into the base liquid to obtain an oil layer simulating aqueous solution;
104, adjusting the pH value of the oil layer simulating aqueous solution according to the pH value of the oil layer water; and adjusting the viscosity value of the simulated oil layer aqueous solution according to the viscosity value of the oil layer water to obtain the well control fluid.
In the embodiments of the present application, reservoir water refers to reservoir water of a producing formation in an operating oil (water) well; the base fluid is used for preparing the well killing fluid; the diluent is used for diluting preset ions in the base liquid so as to reduce the equivalent concentration of the preset ions in the base liquid; the chemical reagent is a fixing reagent containing a preset ionic element and used for increasing the ion equivalent concentration in the base liquid.
According to the embodiment of the application, firstly, diluent and/or chemical reagent are added into base fluid according to the equivalent concentration of multiple preset ions in reservoir water of a production layer to prepare the reservoir simulating aqueous solution, and then the pH value and the viscosity value of the reservoir simulating aqueous solution are further adjusted according to the pH value and the viscosity of the reservoir water of the production layer to obtain the well killing fluid. The concentration of ion is predetermine to corresponding multinomial in the kill fluid that this application embodiment prepared obtains is equivalent with the multinomial equivalent concentration of predetermineeing the ion in the oil reservoir aquatic, and PH value and viscosity number value also are equivalent with the oil reservoir water, and then make and have good compatibility between kill fluid and the oil reservoir liquid, has avoided adopting the kill fluid to take place the oil reservoir allergy phenomenon at the kill process to the porosity and the permeability of oil reservoir have been protected, oil well output is guaranteed.
As the base fluid, the diluent and the chemical reagent adopted in the embodiment of the application can be conveniently obtained, the preparation cost can be saved by adopting the method to prepare the well killing fluid.
The production zone fluid is a mixture of oil and water, including organic and inorganic components. The organic components generally do not affect the reservoir, while the inorganic components cause reservoir irritation due to reaction by ionic bonding with the formation. In order to avoid the oil layer allergy phenomenon, the well killing fluid needs to be compatible with the oil layer fluid, namely, the equivalent concentration of ions in the well killing fluid and the oil layer water is equivalent.
The chemical composition of the oil layer water is very complex, and the ion types contained in the oil layer water are many. Wherein the most common ions include the cation Na+、K+、Ca2+、Mg2+And anion CI-、SO4 2-、CO3 2-、HCO3 -The mass of the catalyst in oil layer water accounts for more than 99 percent, and the catalyst also contains Br-、I-、Sr2 +、Li+And the like. In consideration of simplicity and feasibility of implementation of the scheme, the main ions in the oil layer water can be selected as the preset ions for preparation, namely, the preset ion concentration of the prepared well control fluid is equivalent to the equivalent concentration of the corresponding preset ions in the oil layer water.
In one possible embodiment, the predetermined ion may be made to include Na+、K+、Ca2+、Mg2+、CI-、SO4 2-、CO3 2-、HCO3 -Any of the above. Taking into account Na+、K+And CI-Little or no effect or damage to the formation may be caused, and in one practical embodiment, the predetermined ions may be made to include five ions, calcium, magnesium, sulfate, carbonate, and bicarbonate.
Further, "normality" refers to the concentration of a solution expressed by the number of gram equivalents of solute contained in 1 liter of the solution (expressed by N). The embodiment of the application aims at preparing the well killing fluid with equivalent concentration equivalent to the corresponding preset ions in the reservoir water, and the equivalent concentration is selected for metering, because the gram equivalent number of the anions and cations in the solution is equal, the calculation in the preparation process is convenient.
Specifically, for step 101, determining the equivalent concentrations of a plurality of preset ions in the reservoir water may include the following steps:
in the embodiment of the application, reservoir water refers to reservoir water of a production zone of an operating oil (water) well, and can be directly obtained from production. If the reservoir water produced by the operating well is not available, the reservoir water of the same reservoir of the adjacent well may be used.
More specifically, the equivalent concentrations of a plurality of predetermined ions in the reservoir water can be determined by chemical methods, respectively.
For step 102, determining the equivalent concentrations of the plurality of predetermined ions in the base fluid may include the following:
the base fluid refers to a base fluid used for preparing the well control fluid. In embodiments of the present application, filtered formation water or surface water may be used as the base fluid. In consideration of the reason of oil layer leakage, the content of solid suspended substances in the base liquid is less than 10 mg/L.
For step 103, comparing the equivalent concentration of the multiple preset ions in the oil layer water with the equivalent concentration of the multiple preset ions in the base liquid, and adding a diluent and a chemical reagent into the base liquid when the equivalent concentration of at least one ion in the multiple preset ions of the base liquid is not less than the equivalent concentration of the corresponding ion in the oil layer water to obtain an oil layer simulating aqueous solution; and when the equivalent concentration of a plurality of preset ions in the base liquid is less than the equivalent concentration of corresponding ions in the oil layer water, adding a chemical reagent into the base liquid to obtain the oil layer simulating aqueous solution.
The examples of the present application are prepared primarily by the addition of chemical reagents. That is, the concentrations of the multiple preset ions in the base fluid need to be equal to or lower than the corresponding concentrations of the multiple preset ions in the reservoir water, otherwise, the base fluid needs to be diluted and then prepared by adding a chemical reagent.
The diluent is a liquid for diluting preset ions in the base liquid so as to reduce the equivalent concentration of the preset ions in the base liquid. For example, the diluent may be fresh water and/or fresh water, and the equivalent concentration of the preset ions in the diluent is not greater than the equivalent concentration of the preset ions in the base fluid and not greater than the equivalent concentration of each preset ion in the reservoir water. The chemical reagent is a solid reagent containing a predetermined ion element for increasing the ion equivalent concentration in the base liquid.
In one possible embodiment, when the equivalent concentration of at least one ion in the plurality of preset ions in the base fluid is not less than the equivalent concentration of the corresponding ion in the reservoir water, adding a diluent and a chemical agent to the base fluid to obtain the reservoir-simulated aqueous solution, comprises:
determining the equivalent concentration of a plurality of preset ions in the diluent;
determining ions with the largest equivalent concentration difference ratio value as reference ions according to the equivalent concentrations of a plurality of preset ions in the oil layer water, the equivalent concentrations of the plurality of preset ions in the base liquid and the equivalent concentrations of the plurality of preset ions in the diluent;
preparing an intermediate solution based on the base solution and the diluent according to the equivalent concentration of the reference ions in the oil layer water, making the equivalent concentration of the reference ions in the intermediate solution equal to the equivalent concentration of the reference ions in the oil layer water, and then calculating the equivalent concentrations of other ions except the reference ions in the plurality of items of preset ions of the intermediate solution;
calculating the addition amount of chemical reagent corresponding to each ion of other ions according to the equivalent concentration of other ions in the intermediate solution and the equivalent concentration of other ions in the oil layer water;
and adding a chemical reagent into the intermediate solution to obtain an oil-imitating layer aqueous solution.
In another possible embodiment, when the equivalent concentrations of a plurality of preset ions in the base fluid are all less than the equivalent concentrations of corresponding ions in the reservoir water, adding a chemical reagent into the base fluid to obtain the reservoir-simulated aqueous solution, including:
calculating the addition amount of a chemical reagent corresponding to each ion of the multiple preset ions according to the equivalent concentration of the multiple preset ions in the base fluid and the equivalent concentration of the multiple preset ions in the oil layer water;
and adding a chemical reagent into the base solution to obtain an oil-imitating layer aqueous solution.
Wherein, the kind of the added chemical reagent can be selected according to the type of the preset ion. For example, when the plurality of predetermined ions include calcium ion, magnesium ion, sulfate ion, carbonate ion, and bicarbonate ion, the chemical agent may be solid agents such as sodium and/or potassium sulfate, sodium and/or potassium carbonate, sodium and/or potassium bicarbonate, calcium chloride, and magnesium chloride.
When the method is used, when the equivalent concentration of calcium ions in the base fluid is less than that of calcium ions in oil layer water, calcium chloride is added into the base fluid;
when the equivalent concentration of magnesium ions in the base liquid is less than that of magnesium ions in the oil layer water, adding magnesium chloride into the base liquid;
when the equivalent concentration of sulfate ions in the base liquid is less than that of sulfate ions in the oil layer water, adding sodium sulfate and/or potassium sulfate into the base liquid;
when the equivalent concentration of carbonate ions in the base liquid is less than that of the carbonate ions in the oil layer water, adding sodium carbonate and/or potassium carbonate into the base liquid;
and when the equivalent concentration of the bicarbonate ions in the base fluid is less than that of the bicarbonate ions in the oil layer water, adding sodium bicarbonate and/or potassium bicarbonate into the base fluid.
In step 104, the PH value of the simulated oil layer aqueous solution can be further adjusted according to the PH value of the oil layer water, and the viscosity value of the simulated oil layer aqueous solution can be adjusted according to the viscosity value of the oil layer water, so as to obtain the well control fluid.
More specifically, adjusting the PH of the simulated reservoir aqueous solution based on the PH of the reservoir water may include:
determining the pH value of oil layer water;
adding hydrochloric acid or sodium hydroxide into the aqueous solution of the simulated oil layer according to the pH value of the water of the oil layer.
In fact, because each ion concentration in the simulated oil layer water is equivalent to each ion concentration in the oil layer water, the difference between the pH value of the oil-proof layer water and the pH value of the oil layer water is very small, only a small amount of hydrochloric acid or sodium hydroxide needs to be added when the pH value of the oil-proof layer water is adjusted, and the influence on other ions in the oil-proof layer water can be ignored.
Adjusting the viscosity value of the simulated reservoir aqueous solution according to the viscosity value of the reservoir water may include:
determining the viscosity value of oil layer water;
adding xanthan gum or polyacrylamide into the oil layer simulating water solution according to the viscosity value of the oil layer water.
The xanthan gum or polyacrylamide can increase the viscosity of the well killing fluid and increase the capillary force, thereby reducing the loss of the well killing fluid.
In addition, if the density of the compatible well killing fluid does not meet the well killing requirement of operation construction, potassium chloride or sodium chloride can be added to adjust the density of the well killing fluid so as to achieve the well killing fluid meeting the density of the operation construction requirement.
The technical solutions and advantages of the present application will be further described with reference to specific examples.
Taking port 5-60-1 of the oil field in port east as an example, before killing a well in a production zone, preparing a killing fluid, and performing the following operation:
1) firstly, oil layer water is obtained, five ion measurements are carried out on the oil layer water of an oil well to be operated, and the ion concentrations are respectively (milliequivalent/liter):
anion: sulfate 1.5, carbonate 3, bicarbonate 20
Cation: calcium ion 5 and magnesium ion 4
2) Selecting oil layer water filtered by a sewage station as base liquid, and carrying out five-item ion measurement on the base liquid, wherein the ion concentrations are respectively (milliequivalent/liter):
anion: sulfate 2.5, carbonate 5, bicarbonate 15
Cation: calcium ion 8 and magnesium ion 6
3) Selecting clear water as diluent, and measuring five ions in the clear water, wherein the ion concentrations are respectively (milliequivalent/liter):
anion: sulfate 0.5, carbonate 1.1, bicarbonate 1.2
Cation: calcium ion 2 and magnesium ion 0.8
4) Preparation of intermediate solution
The first step is as follows: the equivalent concentrations of the five ions were compared.
The second step is that: a reference ion is determined. Taking the gram-equivalent concentration of the ion with the larger difference as a reference ion to prepare an intermediate solution:
if it is required to prepare a control fluid volume of V, assuming a base fluid volume of V1Volume of the diluent is V2，V*N＝V1*N1+V2*N2And V ═ V1+V2The column equation of once in two:
since the difference in gram-equivalent concentrations of carbonate ions is the greatest, take N1＝5，N2＝1.1
I.e. 3V-5V1+1.1V2
V＝V1+V2
If V is 20 cubic meters, the solution of the equation V19.7 cubic meters, V210.3 cubic meter
That is, 9.7 cubic meters of the base solution was mixed with 10.3 cubic meters of the diluent to obtain 20 cubic meters of the intermediate solution.
The third step: the concentration of each of the other ions in the intermediate solution (meq/l) was calculated.
Sulfate ion ═ 2.5V1+0.5V2)/V＝(24.25+5.1)/20＝1.5
Bicarbonate radical (15V)1+1.2V2)/V＝(145.5+12.4)/20＝7.9
Calcium ion ═ 8V1+2V2)/V＝(77.6+20.6)/20＝4.9
Magnesium ion ═ 6V1+0.8V2)/V＝(58.2+8.2)/20＝3.3
5) An aqueous simulated oil layer solution was prepared. Because the great carbonate ion concentration of the ratio according to the difference of above-mentioned process is accomplished, so other ion concentration all do not reach the concentration of corresponding ion in the oil reservoir water, at this moment, adopt the mode of adding chemical reagent to accomplish the concentration index of other ions, specifically do:
the difference in gram-equivalent concentrations of sulfate ions is 1.5-0 meq/l,
when sodium sulfate is added, the addition amount thereof is 0 × V × 142/2 ═ 0 g (sodium sulfate molecular weight 142, sodium ion number 2);
the difference between the gram equivalent concentration of the bicarbonate ion and 20-7.9 is 12.1 milliequivalents/L,
when sodium bicarbonate is added, the addition amount is 12.1V 84/1 g 20328 g (sodium bicarbonate molecular weight 84, sodium ion number 1);
the difference of the gram equivalent concentration of the calcium ions is 5-4.9-0.1 milliequivalent/L,
when calcium chloride is added, the addition amount is 0.1V 111/2 g (calcium chloride molecular weight 111, calcium ion valence 2);
the difference of the gram equivalent concentration of the magnesium ions is 4-3.3-0.7 milliequivalent/L,
when magnesium chloride is used, the amount of magnesium chloride added is 0.7V 95/2 g 665 g (magnesium chloride molecular weight 95, magnesium ion valence 2).
Thus, 20328 g of sodium bicarbonate, 111 g of calcium chloride and 665 g of magnesium chloride were added to the above intermediate solution to obtain an aqueous simulated oil layer solution.
6) And preparing the well killing fluid.
And respectively measuring the pH value and the viscosity value of the oil layer water and the oil layer simulating aqueous solution by adopting an acidity tester and a viscosity tester, and adjusting the pH value and the viscosity value of the oil layer simulating aqueous solution according to the pH value and the viscosity value of the oil layer water to obtain the well killing fluid.
Through detection, the concentration of each ion in the well killing fluid is equivalent to that of the corresponding ion in the oil layer water, and the PH value and the viscosity value are also equivalent to that of the oil layer water. The prepared well killing fluid is adopted to kill the well, and the effects of preventing oil layer pollution and oil layer allergy can be achieved.
The above description is only for facilitating the understanding of the technical solutions of the present application by those skilled in the art, and is not intended to limit the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.