Maoming Basin is located in Maoming City in the west of Guangdong Province, with east longitude11'~1103' and north latitude 2 1 26' ~ 22 18'. The uplift areas of Guangdong, Guangxi, Tailong and western Guangdong, which are located on the south China paraplatform, are Cretaceous-Paleogene fault basins formed after Yanshan movement at the end of late Jurassic. Neither the second evaluation nor the third evaluation was evaluated.

The exploration workload in the basin mainly includes surface geological survey1:200,000, aeromagnetic survey1:200,000, gravity and magnetic survey1:110,000 in the north of the basin, seismic survey line of 445.2km, and drilling 149 wells, with a cumulative footage of 6.5766.

This round of resource evaluation is compared with the oil calibration area in the eastern depression of Baise Basin by analogy method. Based on the research results of the south branch, the project research work is carried out according to the actual situation of Maoming Basin. According to this assessment, the prospective oil resources of the basin are 0.0648× 108t, the geological oil resources are 0.0526× 108t, and the recoverable oil resources are 0.0079× 108t.

Second, the geological conditions

(1) Geological survey

Maoming basin can be divided into three secondary structural units: Zhendaling sag, Bei Tang low uplift and Valong sag. The basin structure is relatively simple, and the Paleogene-Neogene basin covers an area of 400km2, with high drilling degree and low resource proven rate. According to the division principle of evaluation units in the evaluation implementation plan, the Paleogene-Neogene system in Maoming basin is evaluated as a whole, and the resources of Cretaceous basin are not calculated in this round of evaluation.

The distribution area of Cretaceous in the basin is 1500km2, and the strata are continental pyroclastic rocks, sand and mudstone. The distribution area of Paleogene-Neogene is only 400km2, and the maximum buried depth of basement is 2500m. Lower part of Paleogene-Neogene: including Youganwo Formation (E2-3y), Huangniuling Formation (N 1h) and Shangcun Formation (N 1s), mainly composed of grayish black mudstone and grayish brown oil shale, with a total thickness of 0 ~ 450 m, in which the sandstone of Huangniuling Formation is relatively developed; Upper Paleogene-Neogene: including Laohuling Formation (N2l) and Gaopengling Formation (N2g), interbedded with glutenite, sandstone and mudstone, with a total thickness of 0 ~ 1500m.

(2) Source rocks

The source rocks in the basin are mainly taupe-grayish black oil shale and mudstone of Paleogene Youganwo Formation and Neogene Shangcun Formation, with a cumulative total thickness of 550m and a continuous maximum thickness of 300-500m. The distribution area of source rocks is about 83km2, and the buried depth: the roof of Youganwo Formation is generally 1932m, and the buried depth of the floor is about1980m; The roof of Shangcun Formation is generally 800 meters, the uplift is 4 15 meters, and the buried depth of the floor is about 1200 meters ... The geochemical indicators of source rocks are as follows: Youganwo Formation: organic carbon c:13.26%; Chloroform asphalt "A": 0.875%; Reduced sulfur s: 0.94%; Fe2+/Fe3+: 10.25； Shangcun Formation: organic carbon C: 3.07%; Chloroform asphalt "A": 0.331%; The reduced sulfur is 0.203% and Fe2+/Fe3+ is 9.655. The above geochemical indicators show that the oil shale and mudstone in Youganwo Formation and Shangcun Formation of Paleogene are rich in organic matter and have good oil-generating ability. Most of the source rocks in the basin are still in the low mature stage, and some source rocks reach the mature stage in the deep depression.

(3) Other conditions for reservoir formation

1. Reservoir conditions

The reservoirs in the basin are mainly sandstone porous reservoirs, which are developed in the middle of Huangniuling Formation and Shangcun Formation. Mainly river sandstone and glutenite. Because the basin is small, the paleotopography fluctuates greatly, forming multi-center and multi-source sedimentary conditions, the sediments are very unstable, and sandstone bodies often become irregular lenslets. The sandstone and gravelly sandstone in the upper member of Huangniuling Formation are 10 ~ 15m thick, the single layer is the thickest 10m, the porosity is generally 15 ~ 30%, with an average of 18.07%, and the permeability is 500 ~ 3000 MD. The sandstone phase transition zone in the middle of Shangcun Formation only develops in the range of 1 ~ 1.2 km south of Tietian fault, with a thickness of 50 ~ 60m, and generally consists of 12 single layer, with the maximum thickness of 12m. The average porosity is 16. 13%, and the average permeability is 631.42md.

2. capping conditions

The Paleogene caprock in Maoming Basin is in good condition, the continuous thickness of mudstone caprock is generally greater than1000 m, the upper member of Huangniuling Formation is covered by Shangcun Formation, and the source rock thickness of Shangcun Formation is100 ~ 550 m ~ 550 m. The thickness of gray-black mudstone in the sandstone phase transition zone in the middle of Shangcun Formation is 90 ~ 150m.

3. Combination of production, storage and mulching

According to the source-reservoir-cap assemblage, the oil-bearing assemblage in this area can be divided into:

(1) Self-generating and self-storing oil-bearing combination: the mudstone of Shangcun Formation is the main source rock of the basin, and it is the regional cap rock of the basin, and the sandstone in the lower part of this formation is the reservoir. After oil and gas generation, they migrated for a short distance and gathered in adjacent sandstone reservoirs, forming a good source-reservoir-cap configuration relationship, such as Bei Tang reservoir in the north of the basin.

(2) Oil-bearing combination of lower generation and upper storage: the source rock is Youganwo Formation, the reservoir is sandstone reservoir of Huangniuling Formation and Shangcun Formation, and the caprock is mudstone of Shangcun Formation, such as shallow oil layer in low mountain area.

(3) Oil-bearing assemblage of Neogene ancient reservoir: Paleogene oil-bearing rocks cover the basement stratum (K), and Paleogene oil and gas migrate to the basement stratum through unconformity or faults, forming oil-bearing assemblage of Neogene ancient reservoir, and crude oil is also found in Cretaceous volcanic fractures in Maoming.

(4) Oil and gas distribution law

The area of Paleogene in Maoming Basin is only 400km2. The buried depth of pre-Paleogene basement can reach 2500 meters, and the depth in the northern part of the basin is generally more than 1000 meters. Oil and gas display is very common, and its horizon comes from Cretaceous eruptive fractures, and all kinds of glutenite in Paleogene are distributed. The main reservoir is the sandstone of Huangniuling Formation, which is distributed in the middle or slope of Bei Tang ancient uplift, and the medium-fine sandstone contains oil.

At present, the types of oil and gas reservoirs found in the basin are mainly lithologic oil and gas reservoirs (for example, the low-lying shallow oil layer is the sandstone lens of Huangniuling Formation) or stratigraphic-structural oil and gas reservoirs (for example, Maoshen 1 Jinghuangniuling Formation sandstone pinch-out zone oil and gas reservoirs).

Iii. Methods and parameters of resource evaluation

This round of evaluation takes the geological resources with a probability of 5% as the prospective resources, and uses analogy method to calculate the oil calibration area of the eastern sag of Baise Basin. The calculation of recoverable resources first obtains the recoverable coefficient by analogy method, and then multiplies the recoverable coefficient by the geological resources to obtain the recoverable resources.

(A) the calculation of analogy similarity coefficient

On the basis of in-depth analysis of the basic conditions of oil and gas geology, according to the established evaluation standards and templates, the geological factors are evaluated and scored item by item, and the final evaluation analogy similarity coefficient is 0. 1923. The geological resources in Maoming basin are calculated by using the area resource abundance method. See table 10-48- 1 for the parameters.

Table 10-48- 1 Parameter Table of Petroleum Geological Risk Analysis in Maoming Basin

sequential

(B) the choice of recoverable coefficient

Maoming basin belongs to the Paleogene-Neogene small fault depression residual basin in the south, and its technical and economic recovery ratio is low, which is 15%.

Fourth, the results of resource evaluation.

(1) Evaluation results of oil and gas resources

Under the probability of 95%, 50% and 5%, the abundance of petroleum geological resources in the oil calibration area in the eastern sag of Baise Basin is 5.0 1× 104, 6.84× 104 and 8.42× 104t/km2 respectively, and the evaluation unit area is 400km2. The evaluation results show that the petroleum geological resources in Maoming Basin are 0.0526× 108t, and the recoverable resources are 0.0079× 108t (table 10-48-2).

Table 10-48-2 Calculation Results of Resources in Maoming Basin

(2) Distribution and grade of oil and gas resources

Maoming Basin, located in the west of Guangdong Province, belongs to low mountains and hills, and the natural geographical feature of oil and gas geological resources in the basin is hills. Maoming basin belongs to Paleogene-Neogene residual basin, and the source rocks are Paleogene-Neogene Youganwo Formation and Shangcun Formation. Source-reservoir-cap assemblage types include authigenic, self-reservoir, epigenetic and epigenetic and epigenetic. The distribution series of oil and gas resources in the basin is mainly Cenozoic Paleogene-Neogene, the depth distribution range of oil and gas resources in the basin is less than 2000 m m, and the grade characteristics of oil and gas resources in the basin are conventional oil.

Verb (abbreviation of verb) exploration suggestion

Maoming basin is rich in oil shale resources, and oil shale is mainly concentrated in the lower part of Youganwo Formation and Shangcun Formation. ① Youganwo Formation: with a distribution area of 300km2 and an average thickness of 25m② Shangcun Formation: with a distribution area of 83km2 and an oil shale thickness of 22m. The proven reserves of oil shale in the basin are 38× 108t (Youganwo Formation is 24× 108t, Shangcun Formation 12× 108t). Maoming oil shale has been put into open-pit mining and refining since 1958.

Although Maoming basin has oil-generating conditions and a certain amount, it is not mature enough because of the shallow burial of Shangcun Formation. The distribution area of source rocks in Youganwo Formation is small, and the burial in the marginal area is shallow. Many wells have been drilled in Paleogene-Neogene basins before, but no high-yield oil and gas wells have been found. Oil sands are exposed on the ground and groundwater is active. Judging from the oil testing, the salinity of formation water is very low. The analysis shows that surface water and formation water collude with each other, and the oil and gas reservoirs are eroded by formation water, with poor preservation conditions, unclear structure, large reservoir changes and small distribution area, mostly sandstone lenses. It is suggested not to consider the new exploration deployment for the time being.

Abstract of intransitive verbs

Through this round of evaluation, Maoming Basin can be divided into three types of oil and gas prospect areas: one type: Bei Tang area, adjacent to the oil-generating sag, but shallow buried, located on the fault zone, poorly preserved; The second type area: Zhendaling-Chendongxu-Fenjiexu area, which is in a favorable oil-generating zone, but its local structure is unclear; Three types of areas: Jintang area, near the fault zone on the edge of the basin, with unclear structure. According to this assessment, the prospective oil resources of the basin are 0.0648× 108t, the geological oil resources are 0.0526× 108t, and the recoverable oil resources are 0.0079× 108t. It is considered that the abundance of petroleum resources in Maoming basin is low and the exploration potential is low.