Tracing method of trace substances in oil field in complex layer

Abstract

The present application relates to oilfield tracer method technical field, it is a kind of oilfield trace usage method of trace material in complex layer, including for the working condition of reservoir is complex layer, tracer is added in the injection well using layered injection mode, tracer is used between layer and layer and is distributed in plane dislocation, tracer includes trace metal element;Sampling is carried out in oil production well;The sample is analyzed, and the tracer content of sample is obtained.The trace usage method of oilfield trace material in complex layer can identify the communication relationship between injection well and its corresponding oil production well, the percolation direction of fluid, the heterogeneity of oil reservoir, and the channeling identification of each layer, which provides a theoretical basis for further developing water drive / gas drive dynamic analysis and measure adjustment.

Description

Technical Field

[0001] This invention relates to the field of oilfield tracing methods, and is a method for tracing trace substances in complex formations in oilfields. Background Technology

[0002] Oilfield development is a process of gradually deepening our understanding of the reservoir. In the early stages of development, it is necessary to determine the direction of fracture development, reservoir heterogeneity, and the effectiveness of initial water injection. During development, it is necessary to determine the current utilization rate of injected water, interlayer mobilization, and the source of produced water. In the later stages of development, it is necessary to determine the existence of high-permeability bands, the effectiveness of oil wells, evaluate the development effect, and determine the remaining oil saturation of large channels.

[0003] Inter-well tracing technology has become one of the main testing methods in reservoir development. It is widely used to qualitatively and semi-quantitatively describe the dynamic changes in reservoir development and production and to improve the understanding of reservoir models. This technology can not only determine the movement of underground fluids, inter-well connectivity, reservoir heterogeneity, and fracture characteristics, but also determine the thickness and permeability of high-permeability channels, providing a theoretical basis for timely measures to be taken and adjustments made during development to improve development results.

[0004] For complex formations with a large number of monitoring wells (more than 8 wells) that are relatively concentrated and have overlapping horizontal and vertical reservoirs, the single-well injection structure development mode can not meet the needs of different elements for each formation due to the limited variety of tracer elements used.

[0005] Patent application CN111257967A discloses an oilfield tracer and a method for oilfield tracer detection. The method includes the steps of: adding an oilfield tracer, comprising fluorescent carbon quantum dots, to an oilfield injection well; obtaining an oil-water mixture at an oilfield production well; and analyzing the presence of fluorescent carbon quantum dots in the oil-water mixture. This application detects the oilfield tracer in the oil-water mixture at an oilfield production well.

[0006] Patent application CN119662238A discloses a slow-release quantum dot tracer for oilfields and its preparation method. The slow-release quantum dot tracer for oilfields comprises the following components by weight percentage: 10-15% quantum dot material, 6-18% curing agent, and 67-84% epoxy resin. The quantum dot material is mainly prepared from a zinc source precursor, doped metal ions, and oxo compounds, with the molar ratio of zinc source precursor, doped metal ions, and oxo compounds being 8-10:0.01-0.1:10-25. Summary of the Invention

[0007] This invention provides a method for tracing trace substances in oilfields in complex formations, which can effectively solve the problem that existing oil well tracing technologies cannot meet the tracing requirements of complex formations.

[0008] The technical solution of this invention is achieved through the following measures: a method for tracing trace substances in complex formations of oilfields, comprising: For reservoirs with complex formations, tracers are added in the injection wells using a layered injection method. The tracers used between layers are distributed in a planar staggered manner, and the tracers include trace metal elements. Sampling was conducted at the oil well. Analyze the samples to obtain the tracer content.

[0009] The following are further optimizations and / or improvements to the above-mentioned technical solution: Furthermore, the injection volume of the tracer is calculated using the following formula: In the formula, A is the injection volume, m 3 S represents the detection sensitivity of the tracer; μ represents the margin coefficient; Vp represents the maximum dilution volume of the tracer, in m³. 3 .

[0010] Furthermore, the maximum dilution volume of the above tracer is calculated using the following formula: In the formula, Vp is the maximum dilution volume of the tracer, m 3 R is the average well distance between the injection well and each production well, m; H is the reservoir leveling thickness, m; Φ is the porosity, %; Sw is the average water saturation, %; a is the scavenging efficiency, %.

[0011] Furthermore, the aforementioned trace metal elements include macro-labeled trace metal elements and micro-labeled trace metal elements. The macro-labeled trace metal elements are one of Er, Ce, and Sm, while the micro-labeled trace metal elements are two or three of Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, and In.

[0012] Furthermore, the tracer is added to the above-mentioned injection well using a layered injection method, with the tracer used between layers being distributed in a planar staggered manner, including: For complex layers with three main layers, the trace metal element used for labeling the main layers is one of Er, Ce, and Sm, and the trace metal elements used for labeling between main layers are different. The trace metal elements used for labeling each sublayer are two or three of Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, and In. The trace metal element combination consisting of the trace metal element used for labeling the main layers and the trace metal element of each corresponding sublayer does not overlap with the trace metal element combination consisting of the trace metal element used for labeling the main layers and the trace metal element of each corresponding sublayer.

[0013] Furthermore, when using the layered injection method, after injecting the required amount of tracer into a single well and a single layer, normal water injection is resumed. After 2 to 3 days of normal water injection or after the single layer water injection reaches the water injection threshold, the required amount of tracer is injected into the next single layer.

[0014] The method for tracing trace substances in complex formations described in this invention can identify the connectivity between water injection wells and their corresponding production wells, the direction of fluid seepage, reservoir heterogeneity, and crosstalk between different layers. This meets the needs of using different elements in different layers of complex formations and provides a theoretical basis for further water-drive / gas-drive dynamic analysis and adjustment of measures. Detailed Implementation

[0015] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0016] The principle of inter-well tracer testing: Based on relevant dynamic and static data of the test well group, a test plan is designed, a suitable tracer is selected and prepared, and the tracer is added to the injection wells of the test well group. Following the established sampling procedure, samples are taken and prepared from surrounding production wells (i.e., oil production wells). Tracer analysis is conducted in the laboratory to obtain the tracer content in the samples. Simultaneously, the tracer production curve of the production wells is plotted, i.e., the curve showing the change in tracer production over time. By comprehensively analyzing the tracer production curve and other relevant dynamic and static data of the test well group, information such as the direction of fluid movement, propulsion speed, and sweep effect is ultimately obtained.

[0017] Inter-well tracer interpretation methods: Inter-well tracer test interpretation methods are constantly being improved and developed. Currently, there are three main methods for interpreting inter-well tracer tests in conjunction with geological models: analytical methods; numerical methods; and semi-analytical methods. This invention organically combines numerical and analytical methods, overcoming the shortcomings of both methods. It possesses the precision and rationality of numerical methods while also having the simplicity and ease of use of analytical methods.

[0018] Large layer: usually refers to a water-filling section formed by the merging of multiple adjacent small layers in stratigraphic division.

[0019] Small layer: refers to a single sand layer or a thin layer with independent water absorption characteristics. It is the basic unit for subdividing water injection and is used to precisely control the water injection volume of high and low permeability layers.

[0020] The present invention will be further described below with reference to embodiments: Example 1: A method for tracing trace substances in complex formations of oilfields, comprising: For reservoirs with complex formations, tracers are added in the injection wells using a layered injection method. The tracers used between layers are distributed in a planar staggered manner, and the tracers include trace metal elements. Sampling was conducted at the oil well. Analyze the samples to obtain the tracer content.

[0021] According to the method of the present invention, by knowing the seepage direction of the injected tracer, the connectivity between the water injection well and its corresponding oil production well and the heterogeneity of the reservoir can be determined.

[0022] Example 2: As an optimization of the above embodiment, the injection amount of the tracer is calculated according to the following formula: In the formula, A is the injection volume, m 3 S represents the detection sensitivity of the tracer; μ represents the margin coefficient; Vp represents the maximum dilution volume of the tracer, in m³. 3 .

[0023] Example 3: As an optimization of the above embodiments, the maximum dilution volume of the tracer is calculated using the following formula: In the formula, Vp is the maximum dilution volume of the tracer, m 3 R is the average well distance between the injection well and each production well, m; H is the reservoir leveling thickness, m; Φ is the porosity, %; Sw is the average water saturation, %; a is the scavenging efficiency, %.

[0024] Example 4: As an optimization of the above embodiment, the trace metal element includes macro-labeled trace metal elements and micro-labeled trace metal elements. The macro-labeled trace metal element is one of Er, Ce, and Sm, and the micro-labeled trace metal element is two or three of Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, and In.

[0025] The tracer has the characteristics of high sensitivity, multiple types, no analytical interference, convenient on-site injection, layered injection capability, and safe use.

[0026] Example 5: As an optimization of Example 4 above, the tracer is added to the injection well in a layered injection manner, and the tracer used between layers is distributed in a planar staggered manner, including: For complex layers with three main layers, the trace metal element used for labeling the main layers is one of Er, Ce, and Sm, and the trace metal elements used for labeling between main layers are different. The trace metal elements used for labeling each sublayer are two or three of Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, and In. The trace metal element combination consisting of the trace metal element used for labeling the main layers and the trace metal element of each corresponding sublayer does not overlap with the trace metal element combination consisting of the trace metal element used for labeling the main layers and the trace metal element of each corresponding sublayer.

[0027] Example 6: As an optimization of the above example, when using the layered injection method, after injecting the required amount of tracer into a single well and a single layer, normal water injection is resumed. After 2 to 3 days of normal water injection or after the water injection of a single layer (which can be a small layer) reaches the water injection threshold (20 cubic meters), the required amount of tracer is injected into the next single layer.

[0028] Example 7: Application Scenario (Tracer Test Between 60 Layers of 20 Injection Wells in a Monitoring Block) This monitoring block has a large number of well groups that are relatively concentrated, with overlapping reservoirs in both horizontal and vertical space, and is developed using a single-well injection structure.

[0029] In this monitoring block, well B21 has a large number of monitoring wells distributed in the same well area, totaling 20 well groups and 60 layers. From top to bottom, there are 3 major layers (S8, B1, and B3). S8 and B1 are adjacent and have no interlayer development. They are relatively concentrated in the plane and overlap in the vertical direction (B1 and B3 overlap in the plane and vertical direction, while S8 and B1 partially overlap in the plane and vertical direction, and the overall distribution is relatively scattered).

[0030] The tracer design scheme needs to meet the overall synchronous monitoring requirements of single well groups and multiple adjacent well groups in this block. The conventional approach of using one element per layer cannot meet the monitoring needs at all.

[0031] Nine wells were used to collect oil and water samples from the S8, B1, and B3 layers. The samples were sent for testing and analysis. The analysis revealed the background values ​​of 33 trace elements, including four restricted elements, four elements with high background values, and 25 usable elements. If the injection is carried out in the conventional manner, the elements will be severely insufficient.

[0032] After repeated deductions, the final design adopted three elements (Er, Ce, Sm) to mark the S8, B1, and B3 layers respectively as crosstalk identification; and trace metal elements (Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, In) to mark the sub-layers. Based on the background conditions, considering the planar distribution and vertical interference, the design should avoid the repetition of elements in single wells and layers. First, the element arrangement of the B1 (24) sub-layer was determined. Since there are only 21 tracer elements for marking the sub-layers, the elements of the bDT21016 and bDT21002 and bDT21003 wells (Table 2) with the largest well distance were considered to be the same, but the elements of the closer bDT21002 and bDT21003 wells and other wells in the same layer were different. The 24 sub-layer tracer elements were screened as shown in Table 1.

[0033] As shown in Table 1, the B1 macrolayer uses Ce as a tracer, and the 24 sublayers corresponding to the B1 macrolayer use two or three trace elements as tracers. Thus, the B1 macrolayer plus the trace metal elements used in each sublayer constitute different element combinations. This element allocation method (first distinguishing each macrolayer by different trace metal elements as marker elements, and then distinguishing each sublayer by other different trace metal elements as marker elements) meets the requirement of using different elements in each layer system.

[0034] Tracer application: (1) The 20 injection wells in this study are stratified injection wells, totaling 60 layers. The tracer preparation water was prepared using clean water, and the injection volume was determined according to the tracer injection volume formula described in Example 2. The tracer was injected in a stratified manner; (2) Normal water injection shall be resumed immediately after the construction of a single well and a single layer is completed. After two days of normal water injection or when the water injection of a single layer reaches 20 cubic meters, the water nozzle can be adjusted and the next layer can be injected. A total of 20 injection wells and 60 layers were completed.

[0035] Tracer sampling and testing: Sampling and analysis should be conducted strictly in accordance with the sampling time.

[0036] in conclusion: 1) Through well-to-well tracer monitoring of 20 water injection well groups, the project lasted for 5 months and analyzed a total of 10,375 samples. The connectivity between the above 20 water injection wells and their corresponding oil production wells was determined through tracer testing.

[0037] 2) Among the 20 well groups, the advance speed ranged from 0.76 m / d to 82.38 m / d. The magnitude of the advance speed does not indicate the strength of inter-well connectivity, but only the strength of the heterogeneity of that connectivity. The above measurements reflect that the injected water is forming dominant flow channels towards these wells, and planar heterogeneity is further developing in these directions.

[0038] 3) Among the 20 well groups, the cumulative tracer recovery rate ranged from 0.0004% to 18.603%. The tracer recovery rate varied significantly among the wells that produced tracers in this test. Most tracers have not yet been produced; formation adsorption and retention may have prevented some tracers from being recovered, and some tracers may have flowed to other areas. As the monitored wells continue to produce, the tracer recovery rate is likely to improve.

[0039] 4) Among the 20 well groups, according to the interpretation results of the tracer software, the peak concentration ranged from 0.048 μg / L to 540.5 μg / L. Judging from the shape of the tracer response curve, it has the characteristics of single peak, double peak and multi-peak. The water channeling may be caused by the existence of high permeability channels.

[0040] 5) Based on the tracer production curve and main permeation channel parameters, the pore structure of the reservoir has changed significantly due to long-term water injection. Some of the interstitial material between the debris particles has been washed out of the formation by the injected water, resulting in a general increase in reservoir permeability and aggravation of reservoir planar heterogeneity, which leads to a deterioration in water drive performance.

[0041] As can be seen from the above, the method for tracing trace substances in complex formations in oilfields according to the present invention can identify the connectivity between water injection wells and their corresponding production wells, the direction of fluid seepage, reservoir heterogeneity, and crosstalk between layers, providing a theoretical basis for further water-drive / gas-drive dynamic analysis and adjustment of measures.

[0042] In the method described in this invention, the large layer uses specific marker elements (Er, Ce, Sm), and the small layer uses 21 other trace metal elements. This makes the element combination composed of the trace metal elements used in the large layer and the small layer serve as a tracer. Each element combination does not overlap and is distributed in a planar staggered manner, which meets the needs of using different elements in each layer system and facilitates the identification of crosstalk between layers in the monitoring well in the later stage.

[0043] The above technical features constitute various 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 tracing trace substances in complex formations of oilfields, characterized in that, include: For reservoirs with complex formations, tracers are added in the injection wells using a layered injection method. The tracers used between layers are distributed in a planar staggered manner, and the tracers include trace metal elements. Sampling was conducted at the oil well. Analyze the samples to obtain the tracer content.

2. The method for tracing trace substances in complex formations in oilfields according to claim 1, characterized in that, The amount of tracer injected is calculated using the following formula: In the formula, A is the injection volume, m 3 S represents the detection sensitivity of the tracer; μ represents the margin coefficient; Vp represents the maximum dilution volume of the tracer, in m³. 3 .

3. The method for tracing trace substances in complex formations in oilfields according to claim 2, characterized in that, The maximum dilution volume of the tracer is calculated using the following formula: In the formula, Vp is the maximum dilution volume of the tracer, m 3 R is the average well distance between the injection well and each production well, m; H is the reservoir leveling thickness, m; Φ is the porosity, %; Sw is the average water saturation, %; a is the scavenging efficiency, %.

4. The method for tracing trace substances in complex formations in oilfields according to claim 1, 2, or 3, characterized in that, Trace metal elements include macro-labeled trace metal elements and micro-labeled trace metal elements. Macro-labeled trace metal elements are one of Er, Ce, and Sm, while micro-labeled trace metal elements are two or three of Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, and In.

5. The method for tracing trace substances in complex formations in oilfields according to claim 4, characterized in that, In water injection wells, tracers are added using a layered injection method. The tracers used between layers are distributed in a planar staggered manner, including: For complex layers with three main layers, the trace metal element used for labeling the main layers is one of Er, Ce, and Sm, and the trace metal elements used for labeling between main layers are different. The trace metal elements used for labeling each sublayer are two or three of Ga, Nd, Yb, Y, Tm, Ho, Sc, Co, Lu, Mo, Cs, Tb, Eu, Al, Dy, Gd, La, Sn, Pr, Zr, and In. The trace metal element combination consisting of the trace metal element used for labeling the main layers and the trace metal element of each corresponding sublayer does not overlap with the trace metal element combination consisting of the trace metal element used for labeling the main layers and the trace metal element of each corresponding sublayer.

6. The method for tracing trace substances in complex formations of oilfields according to claim 1, 2, or 3, characterized in that, When using the layered injection method, after injecting the required amount of tracer into a single well and a single layer, normal water injection is resumed. After 2 to 3 days of normal water injection or after the single layer water injection reaches the water injection threshold, the required amount of tracer is injected into the next single layer.

7. The method for tracing trace substances in complex formations in oilfields according to claim 4, characterized in that, When using the layered injection method, after injecting the required amount of tracer into a single well and a single layer, normal water injection is resumed. After 2 to 3 days of normal water injection or after the single layer water injection reaches the water injection threshold, the required amount of tracer is injected into the next single layer.

8. The method for tracing trace substances in complex formations in oilfields according to claim 5, characterized in that, When using the layered injection method, after injecting the required amount of tracer into a single well and a single layer, normal water injection is resumed. After 2 to 3 days of normal water injection or after the single layer water injection reaches the water injection threshold, the required amount of tracer is injected into the next single layer.

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