Jurong—Changzhou Basin

1. Introduction

The Jurong-Changzhou area includes two continental Mesozoic and Cenozoic basins, Jurong and Changzhou. The basin areas are 3995km2 and 5987km2 respectively, with a total area of ??9982km2. The geographical location is within the range of X: 118°51'27″～120°16'54″, Y: 31°16'51″～32°08'12″.

A total of 82 exploratory wells of various types were drilled in the Jurong Basin, with a total footage of 6.5×104m, and most of the wells were less than 1000m deep. The maximum well depth - Well Shengke 1 is 4250.52m, and the oldest formation encountered during drilling is the Cambrian Guanyintai Formation. There are no digital seismic lines in the Changzhou Basin, and the petroleum and mineral resources departments have completed 94 light-point seismic lines covering a total length of 1,713.5 km. There are 48 shallow wells of various types, including 1 deep well, 11 medium-deep wells, and the rest are shallow wells, with a total footage of 4.52×104m. The oldest strata encountered during drilling are the Triassic. The basin is distributed in the Paleogene, Cretaceous and marine Mesozoic and Paleozoic.

This evaluation is carried out by Sinopec Southern Exploration and Development Branch. It establishes a conventional oil and gas resource evaluation system in the Jurong-Changzhou area, including evaluation method system, parameter system, evaluation specifications and evaluation process, etc.; masters the oil and gas in this area Resource status, obtain resource data at all levels, including geological resources, recoverable resources, and resource distribution; establish a national conventional oil and gas resource evaluation database and evaluation system to provide necessary information and management for future dynamic evaluation and management of oil and gas resources. Technical support. The geological resources of the basin are 1412.00×108m3, and the recoverable resources are 678×108m3.

2. Oil and gas geological conditions

(1) Geological overview

1. Division of structural units

Divide Jurong-Changzhou Jurong Basin and Changzhou Basin, each basin is divided into three secondary structural units (Figure 8-21-1, Table 8-21-1).

2. Basin evaluation strata and unit division

The evaluated strata include the upper assemblage and the lower assemblage. The upper assemblage includes three strata: T1, P, and S. The lower combination includes three layer systems: O, ∈1, and Z2 (Table 8-21-2).

Figure 8-21-1 Division of tectonic units in the Jurong-Changzhou region

Table 8-21-1 Division of tectonic units in the Jurong-Changzhou region

Table 8-21-2 Basin evaluation strata and unit division table

(2) Source rock

1. Organic matter abundance of source rock

The mudstones of the Lower Triassic and Permian are good to medium source rocks, while the mudstones of the Lower Silurian and Lower Cambrian are poor source rocks. Most of the carbonate rocks in the area are poor-non-source rocks. From a plane perspective, the Middle Paleozoic oil-generating layers are relatively developed in the Jurong-Changzhou area, which is the center of Lower Yangtze deposition, and two sub-centers are developed in the Jurong and Changzhou areas respectively.

2. Source rock organic matter types

The organic matter types of Mesozoic and Paleozoic source rocks in this area are mainly type II, that is, mixed type areas.

3. Vertical thermal evolution trend of source rocks

At the end of the Silurian Period, the ∈1mu oil source layer was generally mature; the O3-S1g oil source layer was only partially mature, and most areas were immature— Under cooked. At the end of the Triassic, the ∈1mu oil-generating layers were generally overmature and locally highly mature (Jurong-Nanjing area), and the Taihu area was in the late high-maturity period; most areas of O3-S1g were highly mature and locally mature (northern Jiangsu) or Overmature (Taihu Lake); Middle and Upper Paleozoic source rocks are locally undermature (Taihu Lake area) and generally immature. At the end of the Early Cretaceous, all ∈1mu oil-generating layers were overmature; the O3-S1g oil-generating layers were generally high-mature, and some were overmature; the middle and upper Paleozoic source rocks were low-mature in most areas, and high-mature in some places (Jianning-Yangzhou line) or Unripe (northern Jiangsu). At the end of the Late Cretaceous, most of the O3-S1g oil-generating layers were overmature and partially highly mature; the middle and upper Paleozoic source rocks were generally mature and partially highly mature. Up to now, most of the lower Paleozoic oil-generating layers have entered the over-mature stage, and some areas are still highly mature; most areas of the middle and upper Paleozoic are highly mature, and a few areas are mature or over-mature.

4. Horizontal maturity evolution trend of source rocks

The highest maturity of Lower Paleozoic source rocks is located in the Early Paleozoic deep basin facies area of ??Taihu Lake, and the second highest maturity is located in Jiangning-Yangzhou A first-line Mesozoic foreland basin development area. The highest maturity of Middle and Upper Paleozoic source rocks is located in the Cenozoic basin area, and the second highest maturity is located along the Jiangning-Yangzhou line and Wuxi Taihu area.

Jurong has low maturity due to the small subsidence amplitude in previous times.

5. Hydrocarbon generation history of source rocks

The largest increase in hydrocarbon generation was in the Silurian, followed by the Late Cretaceous, Carboniferous-Permian, Triassic and Paleo Recent times.

From the above, it can be seen that the "three main areas" of hydrocarbon generation in this area are: mainly late paleo; mainly gas generation; mainly early hydrocarbon generation. The planar distribution of hydrocarbon generation in the late Upper and Lower Paleozoic does not coincide with each other. The Middle to Upper Paleozoic source rocks are generally late mature, and their late hydrocarbon generation is actually their main hydrocarbon generation period. The most intense areas are the residual distribution areas of oil generation layers, which are located south of the Nanjing-Yangzhou-Xinghua line and Liyang- North of the Wuxi-Nantong line.

(3) Other reservoir-forming conditions

Multiple sets of reservoirs are developed in the marine Mesozoic and Paleozoic in the Lower Yangtze area, mainly carbonate reservoirs and clastic rock reservoirs. Two types of layers. Carbonate reservoirs mainly include Sinian Dengying Formation algal dolomite, middle and upper Cambrian medium-fine-grained, fine-grained-pink crystal, mud-powder crystal dolomite, and Lower Ordovician Honghuayuan Formation and Lunshan Formation grains. Limestone, Carboniferous Laohudong Formation dolomite and Huanglong Formation bottom coarse crystal limestone, etc. The clastic rock reservoirs mainly include the Silurian Fentou Formation and Maoshan Formation, the Devonian Wutong Formation, and the Permian Longtan Formation.

From the Sinian System to the Paleogene System and the Neogene System, there are multiple sets of caprocks. Possibly as caprocks for the Mesozoic and Paleozoic oil and gas reservoirs, there are the lower Silurian Gaojiabian Formation, the upper Permian Longtan Formation, the Triassic Qinglong Formation, the Zhouchongcun Formation gypsum layer and the upper Cretaceous Pukou Formation. wait. Due to later transformation, some good caprocks suffered severe erosion and their distribution was limited.

A.∈1mu shale (source rock)-Z2dn dolomite (reservoir)-∈1mu shale (caprock); B.∈1mu shale (source rock)-∈2 +3 and O1 dolomite - O3w + S1g mudstone (cap rock); C.S1g mudstone (source rock) - S2f + D3w + C1 sandstone, carbonate (reservoir) - P1q limestone + P1g shale (cap rock) layer); D.P mudstone, limestone (source rock) - P2l+P1y sandstone (reservoir) - P2l+K2p mudstone (caprock); E.T1q limestone (source rock) - T1q limestone (reservoir) -T1q+T2z+K2p mudstone, gypsum salt (caprock).

(4) Oil and gas migration and accumulation rules

The marine Mesozoic and Paleozoic reservoir-forming assemblages in the Jurong-Changzhou area are not only restricted by the generation, storage and capping conditions, but also by Construct motion control. Marine Mesozoic and Paleozoic source rocks entered their peak oil generation period from the late Mesozoic to the Neogene. On the one hand, the generated oil and gas migrated and accumulated in well-preserved anticlines; on the other hand, a certain amount of oil and gas was transported along the It flows through layers and then migrates along the cracks to the unconformity and overlying overlying structures, forming unconformity oil and gas reservoirs and Mesozoic overlying structure oil and gas reservoirs. The Mesozoic and Cenozoic caprock conditions directly affect the preservation of oil and gas reservoirs in this area.

3. Resource evaluation methods and parameter system

(1) Method system

The Jurong-Changzhou Basin is currently a basin with a medium to low degree of exploration. The new round of resource evaluation uses the genesis method and the analogy method for evaluation, and on this basis, the evaluation system and related parameters of the organic carbon method and the analogy method are established. Since commercial oil and gas fields have not yet been discovered in the Jurong and Changzhou basins, and due to data limitations, it is impossible to establish a standard scale area at the sag level for analogy, so the genetic method and analogy with the Sichuan Basin are used to calculate the resources.

(2) Obtaining main parameters

1. Obtaining parameters for resource calculation by analogy method

Implementation of analogy areas: Lower combination accumulation conditions and Leshan- The Longnvsi ancient uplift is relatively similar, and the upper assemblage-Mesozoic reservoir formation conditions are relatively similar to the low-steep structural belt in southern Sichuan. See Table 8-21-3 for obtaining the similarity coefficient.

Table 8-21-3 Geological evaluation coefficient table of Jurong-Changzhou Basin

2. Resource amount by genetic method (organic carbon method)

Each layer The values ??of parameters calculated by the genesis method are shown in Table 8-21-4.

Table 8-21-4 Jurong-Changzhou Basin Genesis Method Parameter Value Table

Continued Table

Implementation of Analogous Calculation Area

< p>Using the current effective exploration area of ??the block as an analogy to calculate the area, the area is 9982km2.

3. Recoverability coefficient

The recoverability coefficient in this area is 48%.

IV. Resource evaluation results

(1) Oil and gas resource evaluation results

1. Prospective resource calculation results based on the genesis method

Sentence Under the probability of 5%, 50% and 95% of the organic carbon method oil and gas resources in the Rong-Changzhou Basin, the resource abundances are 0.5659×108m3/km2, 0.3048×108m3/km2 and 0.1289×108m3/km2 respectively (Table 8-21- 5).

Table 8-21-5 Jurong-Changzhou Basin resource calculation results table

2. Calculation results of oil and gas geological resources by area abundance analogy method

Calculation results of geological resources and recoverable resources (Table 8-21-6). When the probability is 50%, the geological resources are 1412.00×108m3, the recoverability coefficient is 0.48, and the recoverable resources are 678×108m3.

Table 8-21-6 Jurong-Changzhou Basin oil and gas resource evaluation results table

(2) Oil and gas resource distribution

Jurong-Changzhou Basin oil and gas resources The strata are mainly distributed in the Lower Paleozoic and Upper Paleozoic (Table 8-21-7).

Table 8-21-7 Distribution table of oil and gas resource strata

Depth distribution of oil and gas resources (Table 8-21-8).

Table 8-21-8 Depth distribution table of oil and gas resources in the Jurong-Changzhou Basin

The natural geographical distribution of oil and gas resources in the basin is in the plain area; the oil and gas resources in the basin are mainly natural gas.

V. Exploration Suggestions

The secondary structural belts evaluated as Class I favorable areas in this area mainly include the Jurong structural belt in the Jurong Basin and the Gecun-Ershengqiao structure Belt and Shishi structural belt, Huangli-Houyu structural belt in Changzhou Basin (Table 8-21-9).

The Jurong structural belt and the Gecun-Ershengqiao structural belt in the Jurong Basin are regarded as the first level, in order to achieve new breakthroughs or newly discovered exploration target areas; the Shishi structure in the Jurong Basin is The belt and the Huangli-Houyu structural belt in the Changzhou Basin are regarded as the second level, which are exploration target areas for strengthening research and active exploration; the other secondary structural belts in the Jurong-Changzhou Basin and the Maoshan nappe structural belt are regarded as the third level. , an exploration target area for strengthening reconnaissance and active preparation. In the near future, the Jurong-Gecun uplift zone in the Jurong Basin will be focused on deploying exploration workload.

Table 8-21-9 Evaluation results of the Jurong and Changzhou basin areas

VI. Summary

Evaluation of oil and gas resources in the Jurong-Changzhou area Specifically, we have the following results: Mesozoic and Paleozoic oil and gas shows are common in the Lower Yangtze area of ??Jiangsu Province; there are four main sets of good to relatively good oil-generating layers in the Lower Yangtze area of ??Jiangsu Province: the Lower Qinglong Formation (T1x), the Permian, and the Gaojiabian Formation ( S1g)-Wufeng Formation (O3w) and Mufushan Formation (∈1mu), mainly composed of mudstone; according to various data demonstrations, the hydrocarbon generation and accumulation evolution in this area can be roughly divided into three stages. The evolution of Paleozoic source rocks Late hydrocarbon generation or "secondary hydrocarbon generation" is an objective existence.

The geological resources of the basin are 1412.00×108m3, and the recoverable resources are 678×108m3.