Lanping-Simao basin

(1) Overview of the evaluation area

Lanping-Simao basin consists of Lanping sag and Simao sag respectively. Due to the complex geological conditions and poor oil and gas preservation conditions in Lanping sag, only Simao sag is evaluated this time. Simao Depression is located in the southern half of Lanping-Simao Basin, which starts from Ailao Mountain in the east, reaches Lancang River in the west, reaches Jingdong in the north, reaches the national border in the south, is narrow in the north and wide in the south, and spreads to the south until overseas. The domestic boundary is 2010' ~ 24 40' north latitude and100 ~10310' east longitude. The length from north to south is about 390km, the widest part in the south of the depression is about 3 10km, and the narrowest part in the north of the depression is about 90km, covering an area of 47000km2.

(2) Survey of exploration

Limited by the natural environment, Lanping-Simao Basin has made a large structural profile and carried out MT magnetotelluric, aeromagnetic and gravity exploration after years of research in geology, stratigraphy, paleontology, minerals, petroleum and other disciplines, and achieved some achievements and understanding, but so far there is only one 2D seismic line, which still belongs to a low-level exploration area.

(three) evaluation ideas, methods, principles and organizational implementation units

The evaluation system of conventional oil and gas resources in Lanping-Simao basin is established, including evaluation method system, parameter system, evaluation standard and evaluation process. Master the oil and gas resources in the basin and obtain resource data at all levels, including geological resources, recoverable resources and resource distribution; Establish a national conventional oil and gas resources evaluation database and evaluation system to provide necessary information and technical support for the future dynamic evaluation and management of oil and gas resources.

China Petrochemical Company undertook the task of "A New Round of Oil and Gas Resources Evaluation in Lanping-Simao Basin". The new round of oil and gas resources evaluation implementation plan carries out resource evaluation on the basis of unified standards and parameters, which has far-reaching significance for oil and gas exploration in the basin.

(4) Main achievements

The estimation of oil and gas resources in the new round of oil and gas resources evaluation shows that the prospective resources are 5715×108m3; The geological resources are 2054× 108m3. It shows that Simao sag has great potential of oil and gas resources, and comprehensive analysis shows that Jinggu sag is the most favorable oil and gas prospect area.

Second, the geological conditions

(1) Geological survey

1. Division of structural units

The basic structural framework of Simao depression is divided into east-west zone and north-south block, and it is divided into three zones by Jiufang fault and Amojiang fault. From north to south, there are two east-west bulges (JD.COM bulge and Pu 'er-Tongguan bulge), which form the characteristics of north-south block. Taking Simao Depression as the primary structural unit, it can be divided into five secondary structural units from east to west (figure 10-47- 1, table 10-47- 1).

Table 10-47- 1 structural unit division table of Simao sag

2. Strata and unit division of basin evaluation

The organic carbon method is used to evaluate and calculate the prospective resources of Middle Jurassic, Upper Middle Triassic, Upper Permian and Lower Permian. This oil and gas resource evaluation adopts analogy method, taking Mesozoic in Simao sag as the evaluation unit.

(2) Source rocks

1. Distribution of effective source rock series

Effective source rocks are mainly distributed in J2h, T and P layers. Effective source rocks of carbonate rocks are mainly distributed in J2h, T2, P2 and P 1. The effective source rocks of argillaceous rocks are mainly distributed in T3 horizon.

2. Abundance of organic matter in source rocks

Evaluation criteria of source rock abundance in Simao Depression (Table 10-47-2) and evaluation results of organic matter abundance (Table 10-47-3).

Figure 10-47- 1 Division of Structural Units in Simao Depression

Table 10-47-2 Evaluation Standard Table for Organic Matter Abundance Division

sequential

Table 10-47-3 Evaluation Table of Organic Matter Abundance of Source Rocks in Simao Depression

Note: Organic carbon (%), chloroform asphalt "A" and pyrolysis (S2+S 1) in the table are average values.

3. Organic matter types of source rocks

The type of organic matter in J2 source rocks is mainly type Ⅲ, followed by type Ⅱ b; Meng Jing sag is mainly Ⅱ A type, followed by Ⅰ type. It is speculated that the Jingxing-Jiangcheng sag is mainly Ⅱ A type. Type IIA is the main type of T3 and T2. P2 is mainly Ⅱ A type; Lancangjiang uplift is mainly Ⅱ b type; P 1 ⅱA type is the main type. Most areas are of Class II, and the southern part of Lancang Uplift is of Class I. ..

4. Maturity of organic matter in source rocks

Based on vitrinite reflectance Ro, the maturity of organic matter in source rocks is determined by comprehensive pyrolysis of Tmax(℃), S 1/COT, kerogen TAI, A/C, coal type and other items (Table 10-47-4).

Table 10-47-4 Comprehensive division results of organic matter maturity of source rocks

(3) Other conditions for reservoir formation

1. Reservoir type and characteristics

The Devonian to Lower Cretaceous reservoirs in the main section of Simao Depression can be divided into clastic rocks and carbonate rocks. Clastic rocks in Simao Depression are distributed in different thicknesses in Devonian, Longtan Formation of Upper Permian, Xiapotou Formation of Triassic, Weiyuanjiang Formation and Taozishu Formation, Heping Township Formation of Middle Jurassic, Xiaohongqiao Formation of Lower Cretaceous, Jingxing Formation and Mangang Formation, and there are also a few in the stinky water formation and Wushahe Formation of Lower Cretaceous. Carbonate rocks in the central part of Simao Depression are mainly distributed in the middle and upper Carboniferous, Maokou Formation of Lower Permian, Gu Lou Mountain Formation of Dashuijing Ancient Buildings and Xiapotou Formation of Middle Triassic.

2. Characteristics of source-reservoir-cap assemblage

Source-reservoir-cap assemblage is a stratigraphic assemblage with similar geological conditions such as oil and gas generation, migration and accumulation at a certain stage of structural development (Feng et al., 1995). According to this understanding, Simao Basin is divided into two types of six sets of source-reservoir-cap assemblages (Table 10-47-5).

Table 10-47-5 Division Table of Source-Reservoir-Cover Combination

The conditions of source-reservoir-cap assemblage in Simao sag are moderate to good, among which K 1-J2h/J2h, J2h, T3d-T3d-T3t/T3w and T3l-T3y are good, and T2c, P2c/P2l, P 1 are moderate to poor, in Upper Triassic.

3. Reservoir forming conditions

The source rocks have all entered the mature stage and experienced the peak of oil generation. The depression has geological conditions for trap formation, and structural background and sedimentary evolution are its main controlling factors. Good tectonic environment creates conditions for the formation of various structural traps. Fold trap structures in Simao sag are well developed, and 33 local trap structures have been found, some of which are well reflected in seismic profiles. In addition, there are many types of trap structures such as unconformity trap and buried hill trap.

(4) Distribution law of oil and gas (migration and accumulation)

The oil and gas generated in Upper Triassic migrated to the reservoir in the form of water solubility and diffusibility in the early stage. When a large amount of oil and gas is generated and the fluid pressure is greater than the crushing pressure of surrounding rock, the rock breaks and cracks become the dominant migration mode. The main migration period of Upper Triassic natural gas occurred after a large number of hydrocarbons were generated. The migration direction is centered on the hydrocarbon-generating depression and diverges around.

Iii. Methods and parameters of resource evaluation

evaluation methodology

In this resource evaluation, according to the requirements of the Implementation Plan of the New Round of Resource Evaluation, in basins with medium and low exploration degree, analogy method is generally adopted, and genetic method is also adopted. Lanping-Simao basin is a basin with low exploration degree at present. There are two methods for watershed evaluation: genetic method (organic carbon method) and analogy method, and on this basis, the evaluation system and related parameters of organic carbon method and analogy method are established.

(2) Acquisition of main parameters

1. Genetic method (organic carbon method)

The important parameters for estimating resources by organic carbon method include source rock area, thickness and specific gravity, organic carbon recovery coefficient, organic carbon hydrocarbon generation coefficient, hydrocarbon expulsion coefficient and accumulation coefficient (table 10-47-6).

Table 10-47-6 Statistical Table of Calculation Parameters of Organic Carbon Resources in Simao Depression

2. Simulation method

In this evaluation, the resources are calculated by analogy with the anatomical research results of the representative calibration area of Sichuan Basin, and by analogy with the area abundance.

(1) simulation area implementation. The main source rocks are dark marl or calcareous mudstone of Lower Permian (P 1) and dark gray mudstone, marl or micrite of Middle-Upper Triassic (T2-3). The reservoirs are Permian and Triassic sandstone and carbonate rocks, and the reservoir-forming conditions are similar to those in the western Sichuan foreland basin. Therefore, the western Sichuan foreland basin is taken as an analogy.

(2) Calculation of similarity coefficient. Based on the existing geological analogy parameter selection method in Sichuan Basin, the geological characteristic parameters of each basin are calculated and compared with the geological evaluation coefficients of the corresponding standard areas in Sichuan Basin, and the similarity coefficient is obtained (Table 10-47-7).

Table 10-47-7 Table of Geological Evaluation Coefficient of Simao Depression

(3) The realization of analogical calculation area. Taking the effective exploration area of the current block as the analogy calculation area, the area is 47000km2.

3. Calculation of parameters of recoverable coefficient

The recoverable coefficient of this area is 63%.

Fourth, the results of resource evaluation.

(1) Evaluation results of oil and gas resources

See table 10-47-8 for the calculation results of oil and gas resources by organic carbon method in Simao sag. The total resources are 57 15× 108m3(50% probability), and the resource abundance is 0.122×108m/km2 (50% probability).

Analogy calculation results of Mesozoic geological resources in Simao Depression (Table 10-47-9). The geological resources are 2054× 108m3(50% probability), and the recoverable resources are 1294× 108m3(50% probability).

Table 10-47-8 Calculation Results of Potential Oil and Gas Resources in Simao Depression

Table 10-47-9 Evaluation Results of Oil and Gas Geological Resources in Simao Depression

(2) Distribution of oil and gas resources

The oil and gas resources series in Simao Depression are mainly distributed in Upper Paleozoic and Mesozoic (Table 10-47- 10). Among them, the Mesozoic geological resources are1130×108m3 (50% probability), and the recoverable resources are 7 12× 108m3(50% probability). The geological resources of Upper Paleozoic are 924× 108m3(50% probability) and the recoverable resources are 582× 108m3(50% probability).

Table 10-47- 10 Distribution Table of Main Series of Oil and Gas Resources in Simao Depression

See table 10-47- 1 1 for the depth distribution of oil and gas resources. The geological resources at the depth of 2000 ~ 3500m are1130x108m3 (50% probability), and the recoverable resources are 712xkloc-0/08m3 (50% probability). The geological resources at the depth of 3500 ~ 4500m are 924× 108m3(50% probability), and the recoverable resources are 582× 108m3(50% probability).

Table 10-47- 1 1 Simao Depression Oil and Gas Resources Depth Distribution Table

The oil and gas resources in the depression are distributed in mountainous areas, and the characteristics and distribution of oil and gas resources are mainly natural gas.

Verb (abbreviation of verb) exploration suggestion

Resource potential analysis

Comprehensive analysis shows that Jinggu Sub-sag is the most favorable oil and gas prospect, Jingxing-Jiangcheng sag and Puwen sag are favorable oil and gas prospect, Mengxing uplift is a good oil and gas prospect, Pu 'er sag and Yingpanshan uplift are poor oil and gas prospect, and Lancang uplift and Mojiang uplift are poor oil and gas prospect or no oil and gas prospect.

(2) Exploration direction and suggestions

The existing exploration degree in Simao sag is very low, but the estimated potential oil and gas resources (57 15× 108m3) have the material conditions of large oil and gas fields, so it is suggested to intensify the exploration in Simao sag. Due to the poor traffic and natural environment, the exploration work in Simao sag is limited, and the investigation work is limited to the scope of point-line and route investigation. Therefore, on the basis of geological investigation and research, the exploration work of Simao sag should increase the input of geophysical exploration, including seismic exploration, remote sensing geological research, MT survey and so on. Seismic exploration and deployment should focus on Meng Jing sag, Jingxing-Jiangcheng sag, Jinggu sag and Puwen sag in favorable sag areas, taking into account local structures. According to the structural pattern of east-west zoning and north-south block in Simao sag, the general survey profile of seismic line and MT line should be mainly east-west.

Abstract of intransitive verbs

In the new round of oil and gas resources evaluation, organic carbon method is used to calculate the prospective resources, and analogy method is used to calculate the geological resources. Therefore, the prospective resources are 5715×108m3; The geological resources are 2054× 108m3. It shows that Simao sag has great potential of oil and gas resources.

Due to the low degree of exploration in Simao sag, the spatial distribution of source rocks in the sag and the quality of deep source rocks are not well understood, which will affect the evaluation results to some extent. Therefore, we should be cautious in the whole evaluation process and take the lower limit when calculating and determining the thickness, area and various parameters of source rocks, thus ensuring the reliability of the calculation results.