Kailu Basin is located in the eastern part of Inner Mongolia Autonomous Region, under the jurisdiction of Zhaowuda League and Zhelimu League. Geographically, it is located in the south corner of Songliao Basin, adjacent to the Hercynian Fold Belt in Meng Xing in the west, inner mongolian axis in the south and Jiamatu Uplift in the north. The basin is a Mesozoic faulted basin developed on Hercynian folded basement, which consists of five secondary structural units, namely Lujiapu sag, Zhezhong sag, Shebotu uplift, Southeastern Zhejiang uplift and western slope belt, with an area of 3.32× 104km2. The basement is composed of Paleozoic shallow metamorphic rocks and Hercynian granite, with a buried depth of 3000 ~ 4000 meters.
Liaohe Oilfield Company 198 1 started geological survey, 1983 started large-scale seismic exploration, and 1987 started drilling. By the end of 200 1, it has been completed in five key depressions, such as eastern Shandong, western Shandong, Qianjiadian, Longwantong and Manghan. Three-dimensional earthquake 1098km2, drilling 146 wells, with cumulative footage of 27 128 1m, of which 36 wells obtained industrial oil flow.
This resource evaluation is undertaken by China Petroleum Exploration and Development Research Institute and Liaohe Oilfield Company. Methods include genetic method and analogy method. In the genetic method, basin simulation method is used to calculate the resources of four depressions: Ludong, Luxi, Qianjiadian and Longwantong. In the statistical method, the petroleum geological resources and recoverable resources in Luxi and Ludong depressions where more than three reservoirs have been discovered are estimated by using the reservoir size sequence method and the reservoir discovery process model method. In the analogy method, Luxi sag is used as a model to calculate the resources.
Through this evaluation, the prospective resources of Kailu Basin are 3.85× 104t, the geological resources are 3.08× 104t and the recoverable resources are 0.71×104t.
Second, the oil and gas geological conditions
(1) Geological survey
The basin consists of five secondary structural units, namely Lujiapu sag, Zhezhong sag, Shebotu uplift, Dong Zhe uplift and western slope belt.
Lujiapu sag is located in the northwest of the basin, and consists of two depressions, the eastern sag and the western sag, with a total area of 2500km2 and the thickness of sedimentary rocks of 2000-2500m ... The whole sag is divided into seven positive secondary zones and four negative secondary zones, namely Qinghe nose structural zone, central fault structural zone, eastern fault terrace zone, southern overlapping zone, Ma Bei slope zone, Majiapu Gao Lei zone, Baoriwendu fault structural zone and so on. There are more than 60 faults of different degrees in the depression. Upper Jurassic and Cretaceous are the main sedimentary rock series in the depression, with a thickness of 2,000 ~ 2,500 m and a maximum thickness of 3000m m. The source rocks and reservoir rocks in the southern and northern sections of Baori Du Wen structure and the southern section of the central fault structural belt (south of Lu 'an 1 well) overlap with each other, and are close to the provenance in sedimentation and concave in structure, which is a favorable zone for oil and gas accumulation.
Zhezhong Depression is the largest secondary negative structural unit in Kailu Basin, consisting of Baxiantong-Naiman Banner, Manghan, Longwantong and Qianjiadian depressions, Dongming and Dongsuritu bulges and Ihuta fault zone, with an area of 9000km2. There are five favorable depressions in this evaluation unit: Ludong, Luxi, Qianjiadian, Longwantong and Manghan, and the evaluation stratum is mainly Mesozoic Early Cretaceous.
(2) Source rocks
1. Development and distribution of source rocks
The strata where source rocks are developed are Jiufotang Formation, Shahai Formation and Fuxin Formation. Among them, five key depressions of Jiufotang Formation are all developed, and the cumulative thickness of source rocks is 250 ~ 460 m, which has strong oil and gas generation capacity. Shahe Formation and Jiufotang Formation develop together and are distributed in various depressions, among which the mudstone of Shahe Formation in Qianjiadian Depression is the most developed, which is the sedimentary product in the stable subsidence stage during the development of the depression, and the thickness of source rocks is generally 200 ~ 370 m; The source rocks of Fuxin Formation are the product of late depression development, mainly developed in Lujiapu, Longwantong and Mangya depressions, while Qianjiadian depression is undeveloped. The source rocks are 240 ~ 580 m thick, which are fluvial-lacustrine swamp facies deposits in weak reducing environment, and the oil-generating conditions are poor.
2. Rich in organic matter
Through the statistical analysis of organic carbon content, chloroform asphalt "A" content and total hydrocarbon content in the organic matter abundance of source rocks, it is shown that the three sets of source rocks of Jiufotang Formation, Shahai Formation and Fuxin Formation all have oil-generating ability. From the statistical table of organic matter abundance (Table 8- 12- 1), it can be seen that Jiufotang Formation in Lujiapu Depression has the highest abundance index, followed by Shahai Formation and Fuxin Formation has the lowest. Compared with the continental evaluation criteria, the former is a good-excellent source rock, the Shahai Formation is a good-good source rock, and the latter is a poor source rock (Figure 8-650). Overall, Jiufotang Formation in five key depressions has the highest indexes, with an average organic carbon content of 2.77%, chloroform asphalt "A" abundance of 0.29% and total hydrocarbon content1.5/kl. According to the classification standard of organic matter abundance index of source rocks in China, Jiufotang Formation is a good source rock with high oil generation capacity. Secondly, the average value of each index of Shahai Formation reaches the good source rock category and has certain oil-generating capacity, while Fuxin Formation has low organic matter abundance, belonging to poor source rock and poor oil-generating capacity. In addition, various indicators show that Lujiapu sag and Qianjiadian sag in key depressions have the best oil-generating conditions, while Longwantong sag and Mangya sag are average.
Table 8- 12- 1 Statistical Table of Organic Matter Abundance of Source Rocks in Main Depression of Liaohe Peripheral Area
Fig. 8- 12- 1 hydrocarbon source rock grade map of lujiabao depression
3. Types of organic matter
According to the statistical results of kerogen element, carbon isotope, rock pyrolysis and microscopic examination (Table 8- 12-2), the source rock of Jiufotang Formation is humic sapropelic mudstone with high oil generation index and good oil generation conditions. Shahai Formation takes the second place, and the source rock is sapropelic humic type, with relatively good oil generation index and certain oil generation conditions. Fuxin Formation is the worst, with humic source materials, low oil generation index and poor oil generation conditions. According to the statistical analysis results of secondary depressions (Table 8- 12-3), the source rocks in Ludong and Luxi depressions are II1-Ⅰ, with the highest oil-generating index and the best oil-generating conditions, while Qianjiadian, Longwantong, Mangya and Songjia depressions are II1-Ⅱ 2, with better oil-generating conditions. For example, the statistical analysis results of source rock type histogram and source rock quality histogram of Shahe Formation and Jiufotang Formation in Lujiapu Depression (Attached Figure 8- 12-3) show that the source rock Jiufotang Formation has high index and the best oil generation conditions, followed by Shahe Formation and Fuxin Formation.
Table 8- 12-2 Statistical Table of Organic Matter Types of Source Rocks in Main Depression of Peripheral Basin (according to Zhou Shaoqiang 1994)
Note: The values in the table are average values.
Figure 8- 12-2 Kerogen Fan Shi Diagram in Mangya Depression
Table 8- 12-3 Division Table of Organic Matter Types and Thermal Evolution Stages of Source Rocks in Key Depression of Liaohe Peripheral Area
Fig. 8- 12-3 Frequency Distribution of Organic Matter Types of Source Rocks in Lujiapu Depression
Due to the influence of many volcanic eruptions and magma intrusions in the later period, the geothermal gradient is high, which accelerates the evolution of organic matter and the generation of oil and gas. Based on the research results of various data, among several major oil-bearing depressions in Kailu Basin, Qianjiadian Depression has the highest thermal evolution degree and high local maturity, while Ludong, Luxi, Manghan and Longwantong are all in the low maturity stage (Table 8- 12-3).
(3) Other conditions for reservoir formation
1. Reservoir sedimentary development and distribution characteristics
There are many depressions in Mesozoic basin in the exploration area around Liaohe River, which are strongly divided in plane, different in size and scale, and complicated in sedimentation. However, in the process of sedimentary development, because each depression is controlled by the same regional tectonic background, paleoclimate, paleotopography, water medium, provenance, paleogeothermal and other conditions, its sedimentary environment and sedimentary system should have a certain genetic relationship, so the development, phase distribution and reservoir conditions of each depression have similar regularity. Since the early Cretaceous, Liaohe exploration area has a warm and humid tropical-subtropical climate. The water medium in the lake basin is mainly fresh water-brackish water, and the vertical evolution has gone through the stage of fresh water oxidation (Yixian Formation)-brackish water reduction (Jiufotang Formation and Shahai Formation)-fresh water weak oxidation, which is consistent with the occurrence, development and decline of the fault depression.
The development degree and distribution law of reservoirs are closely related to the development history of each depression. The plane distribution of single fault fault block reservoir has obvious zonation. The reservoir near the basin-controlling fault is the most developed, followed by the other side and the worst in the center. Vertically, the main development and rifting activities in the plutonic stage are strong. The double fault depression is obviously different from the former. The reservoirs on both sides of the fault near the edge of the basin are well developed, but the center is slightly worse. From the statistical results in the following table (Table 8- 12-4), we can see the basic development and distribution of clastic reservoirs in each depression. The reservoir of Jiufotang Formation is generally more developed than Shahai Formation and Fuxin Formation in all areas, both in cumulative thickness and in the proportion of layer thickness, with Lujiabao Depression and Qianjiadian Depression being the most developed. Shahe Formation in Zhangqiang Depression is the most developed reservoir, and Fuxin Formation in Songjia Depression is the most developed reservoir. This set of reservoirs has reported proven reserves. As far as Mesozoic basins around Liaohe River are concerned, Jiufotang Formation is the most developed reservoir, followed by Shahai Formation and Fuxin Formation.
Table 8- 12-4 Statistical Table of Development Degree of Clastic Reservoir in Liaohe Peripheral Basin
The development of sedimentary system in the study area is controlled by the structural evolution of depression, basin-controlled faults and provenance. Due to the strong fault depression activity in the exploration area around Liaohe River, the sedimentary development generally shows multi-provenance, near provenance, multi-facies zone, narrow facies zone and various types of reservoir sand bodies, and the sedimentary system shows short-distance transportation and rapid deposition. According to the previous research results, the main sedimentary systems of Liaohe peripheral basin are: alluvial fan-fan delta, alluvial fan-deep lake facies, river-flood plain facies, braided river-delta, cone-product-nearshore underwater fan (underwater fan) and turbidity current sedimentary system.
2. capping conditions
The argillaceous rocks of Shangshahai Formation-Fuxin Formation in the main depression area of Kailu Basin are well developed and have stable lateral distribution, which can be used as regional caprocks. At present, no oil and gas has been found above Shahejie Formation in Luxi Depression, indicating that there is oil and gas seal below Shahejie Formation-Fuxin Formation. Fuxin formation in Xinfa area of Ludong sag also has good oil and gas display. The main reservoirs in this area, Jiufotang Formation and Shahai Formation, are interbedded with sandstone and mudstone, and the mudstone in direct contact with sandstone can be used as a direct local cap for oil and gas reservoirs to block the oil and gas accumulated in the lower reservoirs.
3. Characteristics of source-reservoir-cap assemblage
Good source-reservoir-cap conditions are important conditions for the formation of oil and gas reservoirs in Liaohe peripheral basin. According to the spatial distribution relationship and combined distribution characteristics of source, reservoir and cap rocks in peripheral oil-gas bearing layers, the source, reservoir and cap rocks in five depressions in Kailu Basin can be divided into two types: vertical and horizontal. One vertical combination is that the source rocks of Jiufotang Formation and Shahai Formation form a self-generating and self-storing combination with their own sandstone interbeds and upper mudstone caprocks; Or the source rock of Jiufotang Formation or Shahai Formation and its upper reservoir cap rock of Shahai Formation or Fuxin Formation form a lower-upper reservoir cap combination; The most typical example is that the oil and gas generated from the source rocks of Jiufotang Formation in Songjia Depression migrated to the reservoir cap rock of Fuxin Formation through faults to form oil reservoirs. The lateral assemblage is mainly composed of lithofacies and lithologic differences caused by different sedimentary environments. For example, the source rocks of Jiufotang Formation are in lateral contact with sandstone and glutenite, forming a lateral source-reservoir-cap assemblage model. For example, Baori Du Wen and Majiapu reservoirs in Luxi sag belong to this type of source-reservoir-cap combination.
4. Trap conditions
Due to the control of basement structure, fault activity and sedimentation, many different types of traps are formed in different parts of each depression, mainly including structural traps, structural-lithologic traps and lithologic traps, among which structural traps are the main types of traps in several depressions, including anticline structural traps (such as Baori Wendu in western Shandong), fault nose structural traps (such as Jiaonan in Shandong) and fault block traps. Its development is characterized by the reverse traction anticline structure in the descending plate of the steep slope belt in the plane, and the semi-anticline and fault block trap in the ascending plate. Fault nose trap can be developed in gentle slope zone, and fault block trap can also be developed in fault cutting zone. Structural-lithologic traps are developed in Lujiapu and Longwantong Sags, such as Majiapu in Luxi Sag and Jiaonandu in Ludong Sag. They are typical lithologic-structural traps, which are controlled by the faults near the oil-generating sag and the development of reservoir sand bodies, forming structural-lithologic compound traps controlled by both structure and lithology. Lithologic trap is the most developed in Luxi sag, which is controlled by sedimentary sand bodies of underwater fans around the sag belt, resulting in lithologic differences and lithologic traps. The most typical lithologic trap in Luxi sag is Bao 14 block, which has obtained high-yield industrial oil flow.
(4) Oil and gas distribution law
Up to now, four sets of reservoirs have been found in five key depressions in Kailu Basin, namely Yixian Formation, Jiufotang Formation, Shahai Formation and Fuxin Formation of Cretaceous. Yixian Formation is a volcanic reservoir, mainly distributed in Longwan series and Luxi sag. The other three sets are clastic reservoirs, which are also the basic reservoirs in Kailu Basin and widely developed in five key depressions. Liaohe Oilfield Company has obtained industrial oil flow in three sets of clastic reservoirs in Lujiabao, Qianjiadian and Longwantong Depression and volcanic reservoirs in Longwantong Depression. The reservoirs in the oil-bearing area of the basin can be basically divided into three main types: underwater fan, delta (or fan delta) and turbidite fan, and there is also a special type-volcanic reservoir.
The argillaceous rocks of Shangshahai Formation-Fuxin Formation in the main depression area of Kailu Basin are well developed and have stable lateral distribution, which can be used as regional caprocks. At present, no oil and gas has been found above Shahejie Formation in Luxi Depression, indicating that there is oil and gas seal below Shahejie Formation-Fuxin Formation. Fuxin formation in Xinfa area of Ludong sag also has good oil and gas display. The main reservoirs in this area, Jiufotang Formation and Shahai Formation, are interbedded with sandstone and mudstone, and the mudstone in direct contact with sandstone can be used as a direct local cap for oil and gas reservoirs to block the oil and gas accumulated in the lower reservoirs.
Good source-reservoir-cap conditions are important conditions for the formation of oil and gas reservoirs in Liaohe peripheral basin. According to the spatial distribution relationship and combined distribution characteristics of source, reservoir and cap rocks in peripheral oil-gas bearing layers, the source, reservoir and cap rocks in five depressions in Kailu Basin can be divided into two types: vertical and horizontal.
Three, resource evaluation methods and parameter system
(A) Method system
There are two main methods to calculate the resources of key anatomical areas in western Shandong: occurrence method and statistics method.
Genetic method: Genetic method uses basin simulation method to calculate resources. Based on Basims4.5 and Pasys 1.5, the geological history, thermal history, maturity history and hydrocarbon generation and expulsion history of Luxi sag in Liaohe peripheral basin are simulated, and the hydrocarbon generation and expulsion amount in each geological period is obtained. The amount of petroleum geological resources in the depression is equal to the amount of oil generated in the depression multiplied by the migration and accumulation coefficient, and the amount of geological resources multiplied by the recoverable coefficient to obtain the recoverable resources. See table 8- 12-5 for the calculation results.
Table 8- 12-5 Calculation Results of Genetic Method Resources in Luxi Depression
Statistical method: In the statistical method, the petroleum geological resources and recoverable resources of more than three oil discoveries in Luxi sag, Ludong sag and Zhangqiang sag are estimated by using the reservoir size sequence method and the reservoir discovery process model method. See table 8- 12-6 for the calculation results.
Table 8- 12-6 Calculation Results of Statistical Resources in Luxi Depression
Delphi synthesis method: the petroleum resources estimated by genetic method and statistical method in Luxi sag are weighted by Delphi probability, and the resources under different probabilities are obtained (Table 8- 12-7).
Table 8- 12-7 Comprehensive Evaluation Results of Luxi Depression Resources
Figure 8- 12-4 Resource Probability Distribution Map of Luxi Depression
(B) Evaluation parameter system
1. basin simulation method
This time, basin simulation method is used to calculate the resources of several depressions in Kailu Basin that meet the conditions of applying basin simulation method. Luxi sag has a high degree of exploration (simulated scale area of key depressions in peripheral basins), and its migration and accumulation coefficient is 5.66%. The hydrocarbon source conditions, migration and accumulation conditions, storage conditions and preservation conditions of Ludong sag, Longwantong sag and Qianjiadian sag are compared with Luxi sag respectively, and the similarity coefficient is obtained, and then the migration and accumulation coefficient is obtained. The migration and accumulation coefficients of Ludong sag, Longwantong sag and Qianjiadian sag are 3.64%, 2.96% and 2.5% respectively. See table 8- 12-8 for the calculation results.
In the genetic method, basin simulation method is used to calculate the resources of four depressions: Ludong, Luxi, Qianjiadian and Longwantong. In the statistical method, the petroleum geological resources and recoverable resources in Luxi and Ludong depressions where more than three reservoirs have been discovered are estimated by using the reservoir size sequence method and the reservoir discovery process model method. In the analogy method, Luxi sag is used as a model to calculate the resources. When the basin simulation method is applied, the hydrocarbon source conditions, migration and accumulation conditions, storage conditions and preservation conditions of Ludong sag, Longwantong sag and Qianjiadian sag are compared with Luxi sag respectively, and the similarity coefficient is obtained, and then the migration and accumulation coefficient is obtained. The migration and accumulation coefficients of Ludong sag, Longwantong sag and Qianjiadian sag are 3.64%, 2.96% and 2.5% respectively. See table 8- 12-8 for the calculation results.
Table 8- 12-8 Calculation Results of Basin Model Resources in Liaohe Peripheral Basin
2. Chloroform asphalt "A" method
The resources of other conditional depressions in peripheral basins are calculated by chloroform asphalt "A" method (Table 8- 12-9):
Table 8- 12-9 Calculation Results of Chloroform Asphalt "A" Method
3. Reservoir size sequence method
The calculation results of Liaohe reservoir scale sequence method are as follows: Table 8- 12- 10.
4. Method of reservoir discovery sequence
Only Ludong sag and Zhangqiang sag in Liaohe peripheral basin meet the application conditions of statistical method. See Table 8- 12- 10 for the calculation results of the sequential method of reservoir discovery.
Table 8- 12- 10 Calculation Results of Statistical Resources in Ludong Depression
5. Simulation method
The exploration degree of most depressions in Liaohe peripheral basin is very low, and the parameters required by analogy method are relatively simple and flexible to operate. Therefore, most of the depressions with low exploration degree are calculated by analogy method, and the analogy area is Luxi sag. See table 8- 12- 1 1 for the calculation parameters.
Table 8- 12- 1 1 Relative Analogy Scoring Table of Zhangqiang Depression and Luxi Depression
Fourth, the results of resource evaluation.
(1) Evaluation results of oil and gas resources
Through this evaluation, the prospective resources of Kailu Basin are 3.85× 104t. The geological resources are 3.08× 104, and the recoverable resources are 0.711×104t. See table 8- 12- 12 for the evaluation results.
Table 8- 12- 12 Evaluation Results of Oil and Gas Resources in Kailu Basin
(2) Distribution of oil and gas resources
The petroleum geological resources in the basin are mainly distributed in Cretaceous, with shallow depth, low permeability oil and conventional oil. Luxi sag is dominated by low permeability oil, accounting for 63. 1%, followed by heavy oil, accounting for 35%, and ultra-low permeability oil accounts for only a small part. Ludong sag is dominated by low permeability oil, followed by heavy oil and conventional oil, with less ultra-low permeability oil. Longwantong sag is dominated by conventional oil. Qianjiadian sag is dominated by low permeability oil.
The geographical environment of resource distribution is mainly plain. Judging from the remaining resources of key depressions in the basin, the remaining petroleum geological resources in Ludong sag are the largest, with 0.7545× 108t, followed by Longwantong sag with 0.4823× 108t, Luxi sag, Qianjiadian sag and Mangya sag with 0.38 respectively. This shows that the resource potential between depressions is very different. The exploration potential of the five key depressions is Ludong, Longwantong, Luxi, Qianjiadian and Mangya Depression in descending order.
Verb (abbreviation of verb) exploration suggestion
Resource potential analysis
Lujiabao, Qianjiadian and Longwanguan oil-bearing sags are rich in oil source conditions, with developed source rocks, high organic matter abundance, good types and developed reservoirs, mainly underwater fan and fan delta sand bodies, and the buried depth of the target layer is moderate. The regional caprock is developed and has a good spatial configuration relationship between source, reservoir and cap rocks. At present, a considerable number of oil and gas reservoirs have been discovered, and the types of oil and gas reservoirs are mainly structural oil and gas reservoirs, structural-lithologic oil and gas reservoirs, lithologic oil and gas reservoirs and volcanic oil and gas reservoirs. The reservoirs are mainly distributed in Jiufotang Formation and Shahai Formation, and the oil products include light oil, medium oil and heavy oil. Therefore, these three key depressions have good petroleum geological conditions and exploration potential.
(2) Exploration direction and suggestions
The oil and gas exploration in Kailu Basin has a good resource base, and the comprehensive geological analysis and resource evaluation results show that the basin has a good exploration prospect. However, in the selection of exploration targets, it is necessary to combine the current situation of resources, focus on the two key links of secondary pores and fracture development zones, and combine the actual exploration situation of each depression to formulate feasible exploration policies.
The migration distance of oil and gas in each depression in the basin is short, and the early structural trap near the oil source area is the focus of exploration. The underwater fan, fan delta and braided delta reservoirs in the central oil-generating sag of each sag are the most favorable places to form oil and gas reservoirs. Forward structures in and between depressions and nose structures extending into depressions are the main places for oil and gas accumulation. Volcanic reservoir should be paid attention to.
Abstract of intransitive verbs
So far, four sets of reservoirs have been discovered in Kailu Basin. Yixian Formation is a volcanic reservoir, mainly distributed in Longwan series and Luxi sag. The argillaceous rocks of Shangshahai Formation-Fuxin Formation in the main depression area of Kailu Basin are well developed and have stable lateral distribution, which can be used as regional caprocks. Good source-reservoir-cap conditions are important conditions for the formation of oil and gas reservoirs in Liaohe peripheral basin. According to the spatial distribution relationship and combined distribution characteristics of source, reservoir and cap rocks in peripheral oil-gas bearing layers, the source, reservoir and cap rocks in five depressions in Kailu Basin can be divided into two types: vertical and horizontal. One vertical combination is that the source rocks of Jiufotang Formation and Shahai Formation form a self-generating and self-storing combination with their own sandstone interbeds and upper mudstone caprocks; The lateral assemblage is mainly composed of lithofacies and lithologic differences caused by different sedimentary environments. For example, the source rocks of Jiufotang Formation are in lateral contact with sandstone and glutenite, forming a lateral source-reservoir-cap assemblage model. For example, Baori Du Wen and Majiapu reservoirs in Luxi sag belong to this type of source-reservoir-cap combination.
This resource evaluation shows that the prospective resources of Kailu Basin are 3.85× 104t, the geological resources are 3.08× 104t and the recoverable resources are 0.71×100t.