Why is Xifeng Oilfield the largest oilfield in Longdong?

Xifeng Oilfield is located in Qingyang City and Qingcheng County in Gansu Province, including five districts: Baima, Dongzhi, Banqiao, Gucheng and Shishe. The structure is located in the front part of the southwest slope of the basin, and the oil-producing layers include Chang 3, Chang 6, Chang 7, Chang 8 and Yan 10 of the Jurassic Yan'an Formation, of which Chang 8 is the main oil-producing layer.

The reservoir sand body of the Chang 8 member is a typical delta sediment, and two subfacies, the delta plain and the delta front, are mainly developed, and the delta front subfacies is the main reservoir sand body in the Xifeng Oilfield, which is distributed in a flower-like manner. The reservoir sandstone is mostly distributed in the underwater distributary channel, and the local estuarine dam is generally a single layer of sand thickness of 5m 15m, and the maximum sand thickness. The rock types of reservoir rocks are mainly sandstone, among which feldspar lithic sandstone is the main rock, followed by lithic feldspathic sandstone.

The particle size is mainly fine and medium particles, the sorting is medium, the rounding is mainly secondary edges and corners, the particles are mostly in linear contact, and the cementation type is mainly pore film and film type, and there are some pores and regenerated cementation.

At present, the exploration practice proves that the porosity and permeability of the sandstone in the Chang 8 member of the Xifeng Oilfield have obvious zonal characteristics, and the porosity and permeability in the Zhenyuan and Heshui areas are relatively low, and the average porosity and average permeability of the Pingyu Bureau are relatively low.

The porosity of M2 Dong Zhi area is the highest, which is average, and the permeability is general.

m2 average. The physical properties of the M2 white horse area are generally good, the porosity is general, the average is average, and the permeability is generally .

m2 average. The porosity of the m2 oil layer varies greatly, generally. The average throat radius of the reservoir is small, generally below; The displacement pressure is above, and most of them are greater than; The median radius is smaller, but different sand bodies have their own characteristics. Among them, the average throat radius, displacement pressure, maximum connected throat radius, median pressure, median radius, and median radius in Zhenyuan District; The average throat radius, displacement pressure, maximum throat radius, median pressure and median radius in Baima area have obvious characteristics of biporous structure system.

Exploration results in recent years indicate that the long 81

The sub-delta distributary channel sand body has the potential to form a large oil field, and is the most important oil-bearing layer in the western peak and its surrounding areas. By the end of 2002, the resource conversion rate of Yanchang Formation was only (much lower than that of several large oil-bearing basins abroad), which has good exploration prospects, and it is estimated that the cumulative provenable petroleum geological reserves of Yanchang Formation in Longdong area are (4 5) 108

t。At present, there are a number of wells on both sides of the west peak that have obtained ( industrial oil flow in the Chang 8 Member, and through further implementation of the distribution range of the sand body belt in the Chang 8 Member, the focus is on finding relatively high permeability reservoirs. On the basis of macroscopic research, the genesis of effective reservoirs in different parts of the sand body is analyzed, and favorable drilling targets are found, and (2 3) 108 can be found on both sides of the west peak and in the northern area in the near future

The size of the reserves. According to Fu Jinhua et al. (2004), the Chang 8 member of the Xifeng Oilfield is a water-degrading delta sedimentary period, with the development of underwater distributary channel sand bodies, and Yuzhou is close to the hydrocarbon generation center and is in the low-potential area of the fluid potential, forming a typical lithologic reservoir (Fig.

Figure Reservoir profile of Well Xi 42 and Well West 28 in Xifeng Oilfield.

About 200 million years ago, geologically called the late Triassic, the Ordos Basin was a large lake with vast waters. At that time, the area around Qingyang and Xifeng was a lakeside delta area. The center of the lake is northeast of Qingyang, and the line of Zhenyuan, Jingchuan and Changwu to the south of the west of the west peak is roughly equivalent to the shoreline of the lake.

During the late Triassic period, the flow of water from the southwest to the center of the lake basin in the northeast deposited the sand grains in the delta area, forming a sand layer hundreds of meters thick in the delta. After tens of millions of years of compaction and petrochemical process, the sand layer turned into hard sandstone, forming the sandstone layer of Yanchang Formation, the main oil-bearing layer of Xifeng Oilfield.

Sandstone differs from mudstone in that it retains tiny pores and connectivity. After the oil is generated, it can flow through the pore throat into the pores of the sandstone and accumulate into oil layers. However, the porosity of the sandstone of the Yanchang Formation is very small and the permeability is very low, and it is usually called whetstone, which is very dense.

After oil has entered the low permeability formation over a long period of time, it is very difficult to get it out, and it probably takes the same long age. In order to extract the best from the whetstone formation, the formation must be pressed open by artificial external pressure to guide the oil out of the formation.

The oil-bearing layer of Xifeng Oilfield is long 8 oil layers, which belong to such whetstone formations, which are called ultra-low permeability oil layers. The average permeability of the long 8 layers is about 1 millidarcy. However, due to its large thickness (more than 10 meters thick), large area (more than 500 square kilometers), because of its abundant oil reserves, it has proved oil reserves of 200 million tons, which is the largest oil field in Longdong region, and is the largest oil exploration discovery of China National Petroleum Corporation in the past ten years, which has attracted the attention of the whole country.

On October 24, 2001, Changqing Petroleum Exploration Bureau drilled the West 17 well in Baima Township after fracturing, with a daily output of 34 tons of oil and a depth of 2,100 meters, which was the first industrial oil well in Xifeng Oilfield. The Xifeng Oilfield was put into construction and development immediately after its discovery. The first two blocks, Baima and Dongzhi, produced 10,000 tons of oil in 2002 and 230,000 tons in 2003 (according to the Ministry of Land and Resources).

The development of Xifeng Oilfield will surely benefit one party. Xifeng will be more prosperous and get greater development. May the hard-working and simple people of Xifeng live a happy and happy life.

Xifeng Oilfield is a large oilfield with reserves of more than 400 million tons discovered in the southwest of the Ordos Basin in northern China, and it is also the largest oilfield discovered by China's onshore oil in the past decade. Through large-scale construction in just three years, Xifeng Oilfield now has an annual output of one million tons.