Alkali lake sedimentary reservoir fracturing fluid system selection method
By selecting appropriate fracturing fluids based on reservoir type, the problem of lack of standardized fracturing fluid selection in alkaline lake sedimentary reservoirs has been solved, achieving efficient fracturing stimulation, avoiding gumming and scaling, and reducing stimulation costs.
Patent Information
- Application Number
- CN202410665375.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-27
- Publication Date
- 2025-11-28
AI Technical Summary
In existing technologies, there is a lack of standardization in the selection of fracturing fluids for alkaline lake sedimentary reservoirs, resulting in poor adaptability and high costs. Furthermore, when transforming complex mineral reservoirs into complex mineral reservoirs, the selection of fracturing fluids lacks specificity, leading to problems such as gumming and scaling.
Reservoir types are classified based on the content of reference elements in the core powder soaking solution, the calcite content in the core, and the carbonate content in the formation water. Based on the classification results, guar gum fracturing fluid, acid polymer fracturing fluid, or scale inhibitor polymer fracturing fluid are selected to establish a scientific method for fracturing fluid selection.
It effectively solves the problems of poor targeting and high cost in fracturing fluid selection, avoids post-fracturing gumming and scaling, and ensures efficient fracturing transformation effect.
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of oil and gas production and is a method for selecting a fracturing fluid system for an alkaline lake sedimentary reservoir. BACKGROUND
[0002] The Permian Fengcheng Formation in the Mahu area is the most important replacement layer system in the Mahu sag, and the shale oil in the Mahu area has an exploration potential of hundreds of millions of tons, so the beneficial development of the layer is of great significance. The Fengcheng Formation reservoir in the Mahu oilfield is an alkaline lake deposit, the mineral composition of the reservoir is complex, the heterogeneity is strong, four types of alkaline minerals, namely, sodium bicarbonate stone (Na2CO3.3NaHCO3), carbon sodium calcium stone [Na2Ca2(CO3)3], carbon sodium magnesium stone Na2[Mg(CO3)2] and silicon boron sodium stone (NaBSi3O8) are rich, and part of the reservoir is developed with calcite (calcite), and the formation water is generally sodium bicarbonate type, the alkalinity is strong (the pH is generally greater than 8), and the average mineralization degree is greater than 100000 mg / L. The complex mineral composition and the high mineralization degree of the formation water result in poor adaptability of the downhole fluid to the reservoir. The use of guanidine gum fracturing fluid for fracturing reconstruction frequently causes the post-pressure return of the gel, and the incomplete gel breaking of the fracturing fluid, the use of acid polymer fracturing fluid in some wells causes the calcium carbonate scaling and plugging of the wellbore, the use of the anti-scaling polymer fracturing fluid can solve the problems of the gel returning and the scaling, but the cost is high, the use of the system is blind, the pertinence is poor, and the reconstruction cost is increased. The selection of the fracturing fluid for the Fengcheng Formation lacks corresponding specifications, the reasonable selection of the fracturing fluid has a great influence on the later large-scale development, and becomes a problem to be solved. At present, there is no relevant literature on the selection of the fracturing fluid for the alkaline lake deposit complex mineral reservoir. SUMMARY
[0003] The application provides a method for selecting a fracturing fluid system for an alkaline lake sedimentary reservoir, and overcomes the defects of the prior art, and can effectively solve the problems of the poor fracturing fluid selection for the alkaline lake deposit complex mineral reservoir, the poor pertinence, and the high fracturing reconstruction cost.
[0004] The technical scheme of the application is realized by the following measures: a method for selecting a fracturing fluid system for an alkaline lake sedimentary reservoir, comprising the following steps: dividing the reservoir type according to the content of reference elements in a reservoir core powder immersion liquid, the content of calcite in the reservoir core and the content of carbonate in the formation water; selecting the fracturing fluid according to the divided reservoir type; The reservoir formation water type is NaHCO3 type, the reservoir core powder immersion liquid is obtained by mixing and leaching the reservoir core powder and water at a mass-volume ratio of 1:1, and then performing solid-liquid separation.
[0005] The following is a further optimization or / and improvement of the above-mentioned technical scheme of the application: The determination of the content of the reference elements in the reservoir core powder soaking solution includes: The reservoir core powder is added into water, and heated to leach to obtain a soaking solution; The content of the reference elements in the soaking solution is determined.
[0006] The leaching temperature is 85-95°C, and the leaching time is 3-5h.
[0007] The content of calcite in the reservoir core is determined by X-ray diffraction analysis.
[0008] The determination of the content of carbonate in the formation water includes: taking the formation water and testing the concentration of carbonate therein.
[0009] The reservoir type is divided into the following four types according to the content of the reference elements in the reservoir core powder soaking solution, the content of calcite in the reservoir core, and the content of carbonate in the formation water: Class I reservoir: the content of carbonate in the formation water is ≤10000mg / L, the content of the reference elements is ≤a set threshold value, and the content of calcite in the reservoir is ≤5%; Class II reservoir: the content of carbonate in the formation water is ≤10000mg / L, the content of the reference elements is ≤a set threshold value, and the content of calcite in the reservoir is >5%; Class III reservoir: the content of carbonate in the formation water is >10000mg / L, the content of the reference elements is >a set threshold value, and the content of calcite in the reservoir is ≤5%; Class IV reservoir: the content of carbonate in the formation water is >10000mg / L, the content of the reference elements is >a set threshold value, and the content of calcite in the reservoir is >5%; The reference elements are boron or zirconium, the set threshold value of boron is 200mg / L, and the set threshold value of zirconium is 400mg / L.
[0010] The selection of the fracturing fluid according to the divided reservoir type includes: Class I reservoir selects guanidium gel fracturing fluid, acid polymer fracturing fluid or scale-resistant polymer fracturing fluid; Class II reservoir selects guanidium gel fracturing fluid or scale-resistant polymer fracturing fluid; Class III reservoir selects acid polymer fracturing fluid or scale-resistant polymer fracturing fluid; Class IV reservoir selects scale-resistant polymer fracturing fluid.
[0011] The guanidium gel fracturing fluid is a fracturing fluid in which the total amount of hydroxypropyl guanidium gel and organic boron crosslinking agent accounts for more than 80% of the total effective components.
[0012] The acid polymer fracturing fluid is a fracturing fluid in which the total amount of powdered polyacrylamide thickening agent and organic zirconium crosslinking agent accounts for more than 80% of the total effective components.
[0013] The aforementioned anti-scaling polymer fracturing fluid is a fracturing fluid in which the total amount of emulsion-like polyacrylamide thickener, organozirconium crosslinking agent, and alkaline regulator accounts for more than 80% of the total effective ingredients.
[0014] This invention establishes a method for selecting fracturing fluid systems in alkaline lake sedimentary reservoirs based on reservoir mineral composition and formation water characteristics. This provides a scientific basis for selecting fracturing fluids in alkaline lake sedimentary reservoirs, ensuring efficient fracturing stimulation. The method is simple to operate, highly applicable, and easy to promote and apply. Detailed Implementation
[0015] This invention is not limited to the following embodiments; specific implementation methods can be determined according to the technical solution of this invention and actual conditions. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages.
[0016] The present invention will be further described below with reference to embodiments: Example 1: The method for selecting the fracturing fluid system for this alkaline lake sedimentary reservoir includes the following steps: Reservoir types are classified based on the content of reference elements in the soaking solution of reservoir core powder, the content of calcite in the reservoir core, and the content of carbonate in the formation water. Select fracturing fluids based on the identified reservoir types; The reservoir formation water is of the NaHCO3 type, and the reservoir core powder soaking solution is obtained by mixing and extracting reservoir core powder and water at a mass-volume ratio of 1:1, followed by solid-liquid separation.
[0017] Example 2: As an optimization of the above examples, the determination of the content of reference elements in the reservoir core powder soaking solution includes: The reservoir core powder was added to water and heated for extraction to obtain the soaking solution; The content of reference elements in the soaking solution was determined.
[0018] Example 3: As an optimization of the above example, the heating and leaching temperature is 85℃ to 95℃, and the leaching time is 3h to 5h. Specifically, the reservoir core is ground into powder, 100g of core powder is weighed and added to 100mL of water, heated in a water bath at 90℃ for 4h, and the content of boron or zirconium in the leaching solution is determined by inductively coupled plasma atomic emission spectrometry (ICP).
[0019] Example 4: As an optimization of the above example, the calcite content in the reservoir core was determined by X-ray diffraction analysis.
[0020] Example 5: As an optimization of the above examples, the determination of carbonate content in formation water includes: taking formation water samples and testing the carbonate concentration therein. The carbonate concentration can be determined using methods such as titration.
[0021] Example 6: As an optimization of the above examples, the reservoir types are classified into the following four types based on the content of reference elements in the reservoir core powder soaking solution, the content of calcite in the reservoir core, and the content of carbonate in the formation water: Class I reservoirs: Carbonate content in formation water ≤10000 mg / L, reference element content ≤ set threshold, and calcite content in the reservoir ≤5%; Class II reservoirs: Formation water carbonate content ≤10000 mg / L, reference element content ≤ set threshold, and reservoir calcite content >5%; Class III reservoirs: Formation water carbonate content > 10000 mg / L, reference element content > set threshold, and reservoir calcite content ≤ 5%; Class IV reservoirs: Formation water carbonate content >10000 mg / L, reference element content > set threshold, and reservoir calcite content >5%; The reference elements are boron or zirconium, with a threshold of 200 mg / L for boron and 400 mg / L for zirconium.
[0022] Example 7: As an optimization of the above examples, the selection of fracturing fluid based on the divided reservoir type includes: For Class I reservoirs, guar gum fracturing fluid, acid polymer fracturing fluid, or scale inhibitor polymer fracturing fluid can be selected. For Class II reservoirs, guar gum fracturing fluid or anti-scaling polymer fracturing fluid should be selected. For Class III reservoirs, choose either acidic polymer fracturing fluid or scale-inhibiting polymer fracturing fluid; For Class IV reservoirs, anti-scaling polymer fracturing fluid should be selected.
[0023] Example 8: As an optimization of the above examples, the guar gum fracturing fluid is a fracturing fluid in which the total amount of hydroxypropyl guar gum and organoboron crosslinking agent accounts for more than 80% of the total effective components. Specifically, the effective components in the raw material composition of the guar gum fracturing fluid are other components besides water, including hydroxypropyl guar gum, organoboron crosslinking agent, pH adjuster, etc. In this invention, the raw material composition of the guar gum fracturing fluid, by mass percentage, includes: 0.25% to 0.6% hydroxypropyl guar gum, 0.2% to 0.6% organoboron crosslinking agent, 0.01% to 0.1% pH adjuster, and water.
[0024] Example 9: As an optimization of the above examples, the acid polymer fracturing fluid is a fracturing fluid in which the total amount of powdered polyacrylamide thickener and organozirconium crosslinking agent accounts for more than 80% of the total effective components. Specifically, the effective components in the raw material composition of the acid polymer fracturing fluid are other components besides water, including powdered polyacrylamide thickener, organozirconium crosslinking agent, pH adjuster, etc. In this invention, the raw material composition of the acid polymer fracturing fluid, by mass percentage, includes: 0.2% to 0.6% powdered polyacrylamide thickener, 0.2% to 0.5% organozirconium crosslinking agent, 0.01% to 0.02% pH adjuster, and water.
[0025] Example 10: As an optimization of the above examples, the scale-inhibiting polymer fracturing fluid is a fracturing fluid in which the total amount of emulsion-like polyacrylamide thickener, organozirconium crosslinking agent, and alkalinity regulator accounts for more than 80% of the total effective ingredients. Specifically, the effective ingredients in the raw material composition of the scale-inhibiting polymer fracturing fluid are components other than water, including emulsion-like polyacrylamide thickener, organozirconium crosslinking agent, pH regulator, alkalinity regulator, etc. In this invention, the raw material composition of the scale-inhibiting polymer fracturing fluid, by mass percentage, includes: 0.5% to 1.2% emulsion-like polyacrylamide thickener, 0.2% to 0.5% organozirconium crosslinking agent, 0.005% to 0.01% pH regulator, 0.02% to 0.06% alkalinity regulator, and water.
[0026] This invention addresses the problem of poor applicability of fracturing fluids in the complex mineral reservoirs of the Mahu Fengcheng Formation alkaline lacustrine sedimentary basin, and the risks of backflow and scaling associated with blindly selecting fracturing fluids. A fracturing fluid selection method is developed based on reservoir mineral composition and formation water characteristics. The specific selection criteria are as follows: (1) On the one hand, guar gum fracturing fluid is subjected to high concentrations of alkaline ions (CO3). 2- In environments with concentrations >10000 mg / L, dehydration and concentration will occur, along with high concentrations of CO3. 2- It will consume the breaker, resulting in the fracturing fluid not being able to completely hydrate and break the gel. On the other hand, the guar gum fracturing fluid that is not completely broken will undergo secondary cross-linking with boron and zirconium elements in the reservoir under alkaline conditions, forming a high-viscosity gel, which will cause the gel to return to the wellbore after fracturing.
[0027] (2) Acidic polymer fracturing fluids will not be exposed to high concentrations of alkaline ions (CO3). 2- In environments with concentrations >10000 mg / L, dehydration and concentration occur, and secondary cross-linking with boron and zirconium does not occur under alkaline conditions, thus avoiding the problem of gelation. However, the pH of the gel-breaking fluid in this fracturing fluid system is 3 to 5, which can dissolve reservoir calcite (when calcite content >5%), producing Ca. 2+ Ions, along with abundant CO3 in the reservoir 2- HCO3 -The reaction produces calcium carbonate precipitate and scaling. However, the pH of the guar gum fracturing fluid is >7, which will not dissolve the calcite in the reservoir and cause scaling.
[0028] (3) Anti-scaling polymer fracturing fluid will not cause reverse gelation problem, and its gel breaking fluid pH>6 will not dissolve the calcite in the reservoir and cause scaling problem. Therefore, when the carbonate content in the formation water, the boron content, zircon content and calcite content in the reservoir are all high, choosing anti-scaling polymer fracturing fluid can achieve better results.
[0029] Example 11: Application of the fracturing fluid system selection method for alkaline lake sedimentary reservoirs in the Mahu Fengcheng Formation: The formation water in Well #1 is of the NaHCO3 type, with a salinity of 209110 mg / L and a formation water CO3 content of [missing information]. 2- The concentration was 33135 mg / L. The boron content in the reservoir core powder soaking solution was 621 mg / L, the zirconium content was 281 mg / L, and the calcite content in the reservoir core was 2.5%. Acidic polymer fracturing fluid was selected, and no reverse gelation or scaling occurred during production after fracturing.
[0030] Example 12: Application of the fracturing fluid system selection method for alkaline lake sedimentary reservoirs in the Mahu Fengcheng Formation: The formation water in Well #2 is of the NaHCO3 type, with a salinity of 71508 mg / L and a formation water CO3 content of [missing information]. 2- The concentration was 6147 mg / L. The boron content in the reservoir core powder soaking solution was 217 mg / L, the zirconium content was 52 mg / L, and the calcite content in the reservoir core was 6.2%. Guar gum fracturing fluid was selected, and no reverse gumming or scaling occurred in the post-fracturing production.
[0031] Example 13: Application of the fracturing fluid system selection method for alkaline lake sedimentary reservoirs in the Mahu Fengcheng Formation: The formation water in Well #3 is of the NaHCO3 type, with a salinity of 21919 mg / L and a formation water CO3 content of [missing information]. 2- The concentration was 3790 mg / L. The boron content in the reservoir core powder soaking solution was 136 mg / L, the zirconium content was 21 mg / L, and the calcite content in the reservoir core was 3.5%. Guar gum fracturing fluid was selected, and no reverse gumming or scaling occurred in the post-fracturing production.
[0032] Example 14: Application of the fracturing fluid system selection method for alkaline lake sedimentary reservoirs in the Mahu Fengcheng Formation: The formation water in Well #4 is of the NaHCO3 type, with a salinity of 229,149 mg / L and a formation water CO3 content of [missing information]. 2-The concentration was 11583 mg / L. The boron content in the reservoir core powder soaking solution was 586 mg / L, the zirconium content was 321 mg / L, and the calcite content in the reservoir core was 7.5%. Anti-scaling polymer fracturing fluid was selected, and no reverse gelation or scaling occurred in the post-fracturing production.
[0033] In summary, the fracturing fluid system selection method for alkaline lake sedimentary reservoirs of this invention addresses the challenges of poor applicability of fracturing fluids in complex mineral reservoirs of alkaline lakes, and the risks of backflow and scaling associated with blindly selecting fracturing fluids. It establishes a fracturing fluid selection method based on reservoir mineral composition and formation water characteristics. This provides a scientific basis for fracturing fluid selection in complex mineral reservoirs of alkaline lakes, effectively avoiding serious production-impacting problems such as unmeasured fracturing fluid breakage, backflow, and scaling after fracturing, thus ensuring efficient fracturing stimulation.
[0034] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.
Claims
1. A method for selecting fracturing fluid systems in alkaline lake sedimentary reservoirs, characterized in that... Includes the following steps: Reservoir types are classified based on the content of reference elements in the soaking solution of reservoir core powder, the content of calcite in the reservoir core, and the content of carbonate in the formation water. Select fracturing fluids based on the identified reservoir types; The reservoir formation water is of the NaHCO3 type, and the reservoir core powder soaking solution is obtained by mixing and extracting reservoir core powder and water at a mass-volume ratio of 1:1, followed by solid-liquid separation.
2. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to claim 1, characterized in that... The determination of the content of reference elements in the reservoir core powder soaking solution includes: The reservoir core powder was added to water and heated for extraction to obtain the soaking solution; The content of reference elements in the soaking solution was determined.
3. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to claim 2, characterized in that... The heating and extraction temperature is 85℃ to 95℃, and the extraction time is 3h to 5h.
4. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to any one of claims 1 to 3, characterized in that... The calcite content in the reservoir core was determined by X-ray diffraction analysis.
5. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to any one of claims 1 to 4, characterized in that... Determining the carbonate content in formation water involves taking formation water samples and testing the carbonate concentration.
6. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to any one of claims 1 to 5, characterized in that... Based on the content of reference elements in the soaking solution of reservoir core powder, the content of calcite in the reservoir core, and the content of carbonate in the formation water, reservoir types are classified into the following four types: Class I reservoirs: Carbonate content in formation water ≤10000 mg / L, reference element content ≤ set threshold, and calcite content in the reservoir ≤5%; Class II reservoirs: Formation water carbonate content ≤10000 mg / L, reference element content ≤ set threshold, and reservoir calcite content >5%; Class III reservoirs: Formation water carbonate content > 10000 mg / L, reference element content > set threshold, and reservoir calcite content ≤ 5%; Class IV reservoirs: Formation water carbonate content >10000 mg / L, reference element content > set threshold, and reservoir calcite content >5%; The reference elements are boron or zirconium, with a threshold of 200 mg / L for boron and 400 mg / L for zirconium.
7. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to any one of claims 1 to 6, characterized in that... The selection of fracturing fluid based on the classified reservoir type includes: For Class I reservoirs, guar gum fracturing fluid, acid polymer fracturing fluid, or scale inhibitor polymer fracturing fluid can be selected. For Class II reservoirs, guar gum fracturing fluid or anti-scaling polymer fracturing fluid should be selected. For Class III reservoirs, choose either acidic polymer fracturing fluid or scale-inhibiting polymer fracturing fluid; For Class IV reservoirs, anti-scaling polymer fracturing fluid should be selected.
8. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to claim 7, characterized in that... Guar gum fracturing fluid is a fracturing fluid in which the total amount of hydroxypropyl guar gum and organoboron crosslinking agent accounts for more than 80% of the total effective ingredients.
9. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to claim 7 or 8, characterized in that... Acidic polymer fracturing fluid is a fracturing fluid in which powdered polyacrylamide thickener and organozirconium crosslinking agent account for more than 80% of the total effective ingredients.
10. The method for selecting fracturing fluid systems for alkaline lake sedimentary reservoirs according to claim 7, 8, or 9, characterized in that... The scale-inhibiting polymer fracturing fluid is a fracturing fluid in which the total amount of emulsion-like polyacrylamide thickener, organozirconium crosslinking agent, and alkaline regulator accounts for more than 80% of the total effective ingredients.