Jinghe Basin is located in Jinghe County, Bole County and Wenquan County of Bortala Mongolian Autonomous Prefecture, with an area of about 7000km2. Surrounded by mountains on three sides, it is bounded by Ebinur Lake Fault in Junggar Basin in the east, Alatao Mountain in the north, Biezhentao Mountain, Khan Girgal Mountain and Keguqin Mountain in the south from west to east, and Nushan Mountain in Borocco, Yili Basin. Jinghe basin is also called Bortala basin or Bole basin.
The basin is distributed in the east-west direction, about 180km long, 70km wide from north to south, and 10km at the narrowest point. Generally speaking, the basin is characterized by wide east and narrow west, high west and low east. The western end of the basin is 2500 meters above sea level, and the central and eastern plains are generally 200-600 meters above sea level.
The geological survey of Jinghe Basin began in the 1970s of 19, during which the surface geological survey of1∶ 200,000 was completed. Oil and gas exploration started at 1992, and its exploration process is briefly described as follows (Figure 10-45- 1):
From 65438 to 0992, Xinjiang Petroleum Administration Bureau cooperated with China University of Science and Technology to conduct geochemical research on oil-invaded clastic rocks in Chaweng Prague, and obtained various geological information such as source rock types, organic matter maturity, oil source correlation and so on.
From 1993 to 1994, Xinjiang Petroleum Bureau completed1∶ 200,000 gravity and magnetic survey in Jinghe Basin, covering an area of 1 1000km2.
During the period of 1994, Xinjiang Petroleum Bureau laid four MT survey lines in Jinghe Basin, with a total length of 399km.
1995, Xinjiang Petroleum Bureau built a 663km seismic survey line in Jinghe area, covering 60 times, and the seismic survey network was sparse. The survey network in Shashanzi sag is 8km× 15km ~ 22km× 32km, and the south edge of the sag lacks survey network control. The exploration grid of Wenquan sag is 8km× 28km ~ 8km× 38km, but the exploration grid is sparse.
1995, northwest petroleum geology bureau arranged 12 construction survey line, which is about 300km long and reaches 1 km× 2 km in Wendong1anticline seismic survey network;
1996, Xinjiang Petroleum Bureau completed 1 1 surface outcrop profile survey, about 12300m, carried out field geological exploration 180km, and * * * collected 6 kinds of samples, including 22 1 piece.
During 1996, the seismic work was carried out in Wenquan sag, with a seismic survey line of about 464km and a maximum survey network of 4×7km.
In June, 1996, Xinjiang Petroleum Bureau and Northwest Petroleum Geology Bureau drilled two parameter wells in Chagantunge nose structure and Wendong 1 structure in Wenquan sag, namely Shen Jing 1 well and Boshen 1 well respectively.
The exploration degree of Jinghe basin is relatively low. By the end of 1996 * *, two-dimensional seismic gravity and magnetic surveys of 1224.99km and1∶ 200,000 and four MT profiles have been completed. Three research reports have been completed successively: Regional Gravity and Magnetic Survey Report in Jinghe Area of Xinjiang, Seismic Interpretation in Jinghe Basin and Petroleum Geological Survey and Comprehensive Research in Jinghe Basin.
Figure 10-45- 1 exploration degree map of Jinghe basin
The main work of the Evaluation Report on Oil and Gas Resources in Jinghe Basin was completed by China Petroleum Exploration and Development Research Institute.
Second, the geological conditions
Division of (1) structural units
According to the seismic, gravity and magnetic and MT data, combined with the regional geological background, the area is divided into three first-class structural units (Figure 10-45-2). They are Wenquan sag in the west, Bole uplift and Shashanzi sag in the east.
Wenquan Depression is a linear depression with a width in the east and a width in the west and a height in the west sandwiched between Alatao Mountain and Bizhentao Mountain-Han Ji Gashan, covering an area of about 3000km2. The north-south seismic survey line reflects that the depression is a dustpan depression with thick north and thin south, and the Mesozoic and Cenozoic strata are superimposed on each other and thin south. According to the drilling results of Shen Jing 1 well and Boshen 1 well, the depression is a Cenozoic depression without Mesozoic, and the Cenozoic era is rapidly thickened northward, which is related to the rapid uplift of Alatao Mountain in Himalayan period.
Figure 10-45-2 Structural Outline of Jinghe Basin
Bole uplift separates Wenquan sag and Shashanzi sag, with an area of about 1 100km2. The Cenozoic on the bulge directly covers the Paleozoic, and the bulge gradually transitions with the Paleozoic outcrop area, and transitions with the slopes of Wenquan sag and Shashanzi sag. Permian strata may be distributed on the uplift, but their distribution on the uplift is unclear due to poor reflection of the survey line. One possibility is that it is controlled by the Aksai fault, and the Permian strata are distributed on the west side of the fault, while the Permian strata are missing on the east side of the fault.
Shashanzi sag covers an area of about 2900km2. According to seismic data, it is a Paleogene or Neogene depression with thick south and thin north. The thickest depression is located in the south of Tuanchang 83, and the thickness of sedimentary strata can reach 3400m m m. The Jurassic is locally distributed in this depression, and the Permian strata may be missing.
(2) Stratigraphic characteristics
Jinghe basin is located in the Hercynian fold belt in the northern Tianshan Mountains, with Hercynian fold basement. Most of the basin is covered by Quaternary, with Paleogene and Neogene red beds in the northern margin and Paleogene and Neogene yellow strata in the southeastern margin. Only a few Jurassic strata with nearly east-west zonal distribution are seen in Mozart area of Wenquan County. Late Paleozoic strata are widely exposed in the mountains around the basin. The early Permian Wulang Formation is mostly distributed in the mountain margin, and the late Permian Tomulik Formation is only distributed in the west bank of Ebinur Lake and the south margin of the basin. Carboniferous marine limestone and Devonian strata are widely distributed in the mountains around the basin, while Early Paleozoic and Precambrian strata are only distributed in the mountains at the southern edge of the basin (Figure 10-45-3).
(III) Conditions of source rocks
The evaluation of source rocks mainly starts from the abundance, type and maturity of organic matter of source rocks, and its evaluation standard adopts the evaluation standard of source rocks promulgated by PetroChina.
1. Rich in organic matter
Carboniferous, Upper Permian and Jurassic strata in Jinghe Basin have hydrocarbon generation potential (table 10-45- 1).
Figure 10-45-3 Comprehensive Stratigraphic Histogram of Jinghe Basin
Table 10-45- 1 organic matter abundance data table of source rocks in Jinghe basin
2. Types of organic matter
The type of organic matter is an important parameter to judge the hydrocarbon generation ability of organic matter in source rocks.
Devonian system: according to the data of rock pyrolysis and kerogen elements, it is not difficult to see that the samples in each layer of Devonian system are poor in hydrogen and rich in oxygen, and the H/C atomic ratio is lower than 0.5 and the IH is lower than 50mg/g, indicating that the organic matter types are all type III. Microscopic examination of kerogen shows that the rocks in this group are mainly sapropelic formations with a content of 90% ~ 100%, the rest are inertinite formations, and vitrinite is only a trace. Therefore, it reflects the typical sapropelic kerogen characteristics.
Carboniferous: In the sections of Milchik, Huluhuhe, Aksaiyi and Xianfeng Power Station, the types of organic matter reflected by Carboniferous strata rocks and kerogen are basically the same, and the degree of hydrogen enrichment is very low. For example, the S2/S3 value in rock pyrolysis is generally lower than 0.3, the hydrogen index is basically lower than 50mg/g, and the H/C atomic ratio in kerogen is generally lower than 0.3, which shows the characteristics of humic organic matter. Microscopic examination of kerogen shows that the content of sapropelic formation is 50% ~ 100%, and the rest are vitrinite and inertinite, which reflects the characteristics of type ⅰ-ⅱ 2 kerogen.
Permian: kerogen types reflected in Akshok and Nanshan profiles are basically the same, both of which are humic organic matter and belong to type III organic matter. The microscopic examination results of kerogen show that vitrinite is the main component, accounting for 35% ~ 85%, followed by inertinite and chitin. However, the samples from Nanshan coal mine are relatively rich in hydrogen. The chitin content in Nanshan coal mine is 10% ~ 20%, while the chitin content in Akchok profile is 5% ~ 10%. The pyrolysis and kerogen data of Permian Akshok profile samples are very similar to those of Devonian and Carboniferous samples, and obviously poor in hydrogen, which may be the result of volcanic intrusion and alteration.
Jurassic: Jurassic Xishanyao Formation, mainly on Mozart profile, is composed of dark mudstone, carbonaceous mudstone and coal rock, and the characteristics of organic matter reflected by the three types of rocks are basically similar. In rock pyrolysis, the average S2/S3 is 3.93 ~ 1 1.8, the hydrogen index reaches123 ~ 211mg/g, and the kerogen H/C atomic ratio is 0.70 ~ 0.9/kloc-. Microscopic examination of kerogen shows that it is mainly composed of vitrinite, indicating that the terrigenous parent material has made an important contribution, and it is presumed to be a relatively hydrogen-rich terrigenous type III organic matter.
3. Maturity of organic matter
Whether the organic matter of sedimentary rocks can be converted into hydrocarbons and the scale of hydrocarbon production depends on the heating degree and thermal evolution stage in the geological body, so the maturity of organic matter is an important factor in the evaluation of source rocks.
Because of the lack of vitrinite in Devonian kerogen, there is no Ro data. In addition, due to the low abundance of organic matter in the sample, the highest pyrolysis peak temperature is too low, which can not be used as the chemical basis of maturity. However, in soluble organic matter, the biomarker parameters indicating maturity have reached the thermal equilibrium value, such as the distribution of OEP value is 0.95 ~ 1.77. The two maturity parameters of C29 sterane are 0.38 ~ 0.42 and 0.45 ~ 0.48, respectively. According to the analysis of regional analogy data, it is speculated that the thermal evolution degree of this set of strata has reached the over-mature stage.
The average reflectance of vitrinite of lower Carboniferous mudstone in Mirchik profile and Xianfeng Power Station profile is 2.6% and 2.39%, which has reached the over-mature evolution stage. Ro data were not measured in the middle Carboniferous in Aksaiyi section, but the peak pyrolysis temperature Tmax reached 462℃, which is undoubtedly the evolution feature of high maturity-over maturity. In addition, the soluble hydrocarbon biomarkers have reached the end of isomerization, so it is considered that the thermal evolution of this set of strata should be in an over-mature stage.
The measured Ro data of Permian are from Akshok and Nanshan coal mine profiles respectively. The former has 9 samples with Ro values ranging from 2.5% to 2.8%, while the latter has 10 samples with Ro values ranging from 1.0%- 1.3%. Both sets of data are centralized and reliable. The difference in maturity reflected by the two profiles is actually caused by the thermal alteration of epigenetic volcanic rocks, because a large number of volcanic intrusions were observed in Akshok profile, which caused the rocks on both sides of the intrusion zone to fracture, that is, the instantaneous temperature rise of this layer caused by volcanic intrusion accelerated the thermal evolution of organic matter. Therefore, the Ro data measured in the profile mudstone of Nanshan Coal Mine represents the actual evolution degree of Permian, that is, the organic matter is in the high maturity stage (peak oil generation). The data of rock pyrolysis and soluble hydrocarbon basically reflect this feature.
Ro data measured from mudstone samples of Jurassic Xishanyao Formation in Mozart profile ranged from 0.5% to 0.7%, with an average value of 0.58%, showing the characteristics of immature-low mature organic matter. The peak temperature of rock pyrolysis is generally below 435℃. In the biological standard combination, the isomerization maturity of compounds is low, and the related maturity parameters are basically below the hydrocarbon generation boundary. The macroscopic evolution characteristics can be compared with Jurassic in Junggar basin.
4. Comprehensive evaluation of source rocks
By comparing the abundance, type and maturity of rock organic matter, we can comprehensively evaluate the source rocks in Jinghe Basin.
The source rocks of Permian Timur Formation can be regarded as highly mature regional source rocks that have made practical contributions to oil and gas. This stratum is rich in primitive organic matter, excellent hydrocarbon-generating parent material and relatively rich in lower organisms. The source environment is reduction-strong reduction, and its evolution is at the peak of hydrocarbon generation, which is similar to the Upper Permian source rocks in Junggar Basin.
Jurassic can be inferred as a set of potential oil-generating layers, mainly Xishanyao Formation, which is a set of lacustrine terrigenous organic matter, and the hydrocarbon-generating parent material is mainly higher plants. According to conventional geochemical evaluation, its hydrogen-rich degree is high, but its evolution degree is relatively low.
Carboniferous and Devonian are highly mature-over-mature source rocks. Although it is speculated that the original hydrocarbon-generating parent material is good and the original organic matter is rich, the evolution degree has reached the stage of high maturity-over maturity, especially the Devonian system has experienced high-temperature metamorphism and multiple tectonic movements, and the generated hydrocarbons are difficult to preserve so far.
(4) storage and covering conditions
The fluvial sandstone reservoirs of Upper Permian, Jurassic Sangonghe Formation and Toutunhe Formation are developed in Jinghe Basin and its surrounding areas. The sandstone of Timur Formation in Aqiaoke area on the west bank of Ebinur Lake has a porosity of 0.68% ~ 2.74% and a permeability of 0.02×10-3 ~17.94× 65438+. Micro-fractures are developed in Timuer Formation of Nanshan Coal Mine, but most of them have been filled, all of which are poor-poor reservoirs.
Middle-upper Jurassic reservoir is generally meandering river-braided river channel sandstone, which is only distributed near Kucun coal mine in the northwest of Wenquan county. The thickness of sandstone in Toutunhe Formation is 35.3m, with the timely content of 57% ~ 76%, and the calcite content of interstitial material is less than 65,438+00% ~ 65,438+05%, which is medium-good.
Paleogene or Neogene sandstone should be a good reservoir. Chaweng Prague oil sands are filled with mud in the intergranular cracks of sandstone, and the asphalt content can be as high as 8% ~ 10%, but the porosity cannot be measured due to surface weathering.
The effective porosity of sandstone of Wulang Formation is better than that of Tomulik Formation, with a cumulative thickness of 37.9 meters and a single layer thickness ranging from several meters to 1 1.7 meters. However, the sandstone of Wulang Formation located in the fourth member of the mouth of Baldesu River is a poor reservoir. Carboniferous sandstone is a poor reservoir with low porosity and permeability.
According to the surface and drilling data, there are many sets of Permian, Paleogene or Neogene reservoirs in Jinghe Basin. The lower sub-group of Changji River Formation is mainly mudstone with gypsum layer, and the thickness of gypsum layer can reach 2.5m, which can be used as regional and local cover of the basin. However, due to the great variation of lateral thickness and poor stability, the conditions of caprock are generally poor. It can be seen from the comprehensive logging map of Shen Jing 1 Well that there are several sets of sandstone-mudstone combinations in Shawan Formation and Anji Haihe Formation of Paleogene or Neogene.
Iii. Methods and parameters of resource evaluation
In this resource evaluation, the resource quantity of Permian source rocks in Wenquan sag of Jinghe basin is calculated, and the evaluation methods are genetic method and analogy method.
(A) legal reasons
1. Organic carbon method
(1) source rocks: Because both Carboniferous and Devonian in Jinghe Basin have been metamorphic, the peak of oil generation of these two sets of source rocks may be before Mesozoic, and it is less likely to form reservoirs in the later period. The main body of the basin lacks Jurassic, and the Permian Timur Formation in Wenquan Depression is the best source rock. The Permian source rocks in Jinghe Basin of Wenquan Depression have an area of about 2500km2 and a thickness of about 230m m. ..
(2) Organic carbon recovery coefficient: According to the mature evolution and organic matter types of source rocks in Jinghe Basin, the organic carbon recovery coefficient of source rocks is 1.2.
(3) Hydrocarbon production rate: According to the hydrocarbon generation evolution degree and organic matter type of the source rocks in Jinghe Basin, it is determined that the gas production rate of the Permian source rocks in Jinghe Basin is 6 1.4m3/tc and the oil production rate is 34kg/tc.
(4) Calculation of migration and accumulation coefficient: The calculation of migration and accumulation coefficient of Permian oil in Jinghe Basin adopts the results of statistical model of oil and gas migration and accumulation coefficient published in the third evaluation of China Petroleum, Study on Key Parameters of Scale Area Anatomy and Resource Evaluation (July 2003). The migration and accumulation coefficient of Permian source rock crude oil in Jinghe Basin is calculated to be 2.3% (Table 10-45-2).
Table 10-45-2 Parameters and results of hydrocarbon migration and accumulation coefficient of Permian source rocks in Jinghe basin
Based on the results of the statistical model of oil and gas migration and accumulation coefficient in "Study on key parameters of scale regional anatomy and resource evaluation" (July 2003), the oil and gas migration and accumulation coefficient of Permian source rocks in Jinghe Basin is calculated. Using the above model, the natural gas migration and accumulation coefficient of Permian source rocks in Jinghe Basin is calculated as 1.56‰ (table 10-45-3).
The resources of Permian source rocks in Jinghe Basin are obtained by determining the parameters required by various calculation formulas, such as distribution area, thickness and organic carbon, and then multiplying them by Monte Carlo method (tables 10-45-4, 10-45-5). The petroleum geological resources in Jinghe Basin are 2679.72× 104t, and the natural gas resources are 33.32× 108m3.
Table 10-45-3 Parameters and results of natural gas migration and accumulation coefficient of Permian source rocks in Jinghe basin
Table 10-45-4 Calculation parameters and results of organic carbon petroleum resources in Jinghe basin
Table 10-45-5 Calculation parameters and results of natural gas resources by organic carbon method in Jinghe basin
2. Chloroform asphalt "A" method
According to the distribution area, thickness, density and hydrocarbon migration and accumulation coefficient of effective source rocks, the resources of Permian source rocks in Jinghe Basin are calculated by using chloroform asphalt "A" formula (table 10-45-6). The resources of Jinghe River Basin are 2030.87× 104t.
Table 10-45-6 Parameter Table of Chloroform Asphalt "A" Method Resource Calculation in Jinghe Basin
(2) analogy method
This resource evaluation adopts area abundance analogy method. According to the principle of analogy method, Tiaohu sag in Santanghu basin, which has similar petroleum geological conditions and high exploration degree to Permian source rocks in Jinghe basin, is selected for analogy (Table 10-45-7). The resources of Wenquan sag are 2549.438+08× 104t.
Table 10-45-7 Table of Analogy Resources in Jinghe River Basin
Four. Evaluation results of oil and gas resources
The oil and gas resources of Permian source rocks in Jinghe basin are calculated by organic carbon method, chloroform asphalt "A" method and analogy method. Now the Delphi method is used to summarize the resources calculated by different methods (table 10-45-8, figure 10-45-4). According to Delphi method, the oil resources in Jinghe Basin are 2385.36× 104t, and the natural gas resources are 33. 17× 108m3.
Table 10-45-8 Overview of Oil and Gas Resources in Jinghe Basin
Figure 10-45-4 Evaluation Results of Oil and Gas Resources in Jinghe Basin
The prospective oil and gas resources in Jinghe Basin account for 5% of the calculation results of geological resources, with prospective oil resources of 3020.38× 104t and prospective natural gas resources of 40.02× 108m3.
Oil and gas resources in the basin are all distributed in Permian, with shallow burial depth, mountainous geographical environment and low permeability of oil and gas resources.
Verb (abbreviation of verb) exploration suggestion
Oil seedlings and asphalt have been seen in the outcrop area of Jinghe Basin, which proves that there has been a process of hydrocarbon generation, but the hydrocarbon generation capacity of Carboniferous source rocks has reached a mature stage, while Jurassic source rocks have a high abundance of organic matter, but the sedimentary thickness in the basin is thin, the evolution degree of source rocks is very low, and the distribution area of source rocks is very limited, so the hydrocarbon generation capacity is limited. The main exploration target layer in Jinghe basin is Permian, and the organic matter transformation ability of source rocks is low, which is only distributed in Wenquan sag of Jinghe basin. In addition, due to frequent tectonic movements in the basin, it is difficult to preserve the oil and gas generated in the history of each set of source rocks in the basin, and the traps, reservoirs and preservation conditions in the basin are poor, and the favorable area is small, and the potential for predicting oil and gas resources is small. It is considered that this basin is a possible petroliferous basin with small oil and gas resources and low abundance.
The calculation of Permian source rock resources in the basin shows that the total petroleum geological resources are 2385.36× 104t, and the total natural gas resources are 33. 17× 108m3. It has certain exploration potential, and Permian traps should be the main exploration targets for primary oil and gas reservoirs in the future. So far, the main exploration difficulties and risks are as follows: ① The source rocks have not been confirmed. Permian is the most important source rock in the basin, but due to the poor quality of seismic data, the oil control range and favorable structural traps of Permian and other source rocks need to be further determined. (2) Jinghe Basin experienced multi-stage tectonic movement, with the Upper Paleogene and Quaternary unconformity in the main body of the basin, and the Triassic, Cretaceous and some Jurassic systems missing in the middle. Therefore, when the source rocks enter the peak period of hydrocarbon generation, the generated oil and gas are destroyed and lost due to unfavorable preservation conditions, and can not be preserved so far; ③ Jurassic strata are thinly deposited in the basin, mainly distributed in Shashanzi sag in the east of the basin. Although the quality of source rocks is good, the evolution degree is very low, the hydrocarbon generation ability is limited, and the oil and gas prospect is not good.
Abstract of intransitive verbs
The prospective oil and gas resources in Jinghe Basin account for 5% of the calculation results of geological resources, with prospective oil resources of 3020.38× 104t and prospective natural gas resources of 40.02× 108m3.
The main exploration target layer is Permian, and the organic matter transformation ability of source rocks is low, which is only distributed in Wenquan sag of Jinghe Basin.